Abstract:
A voltage control method and apparatus of a central bus in a power system are provided. The method comprises: S1: obtaining a predetermined voltage and a current voltage; S2: obtaining a first voltage adjustment of the generator and a second voltage adjustment of the dynamic reactive power compensation device; S3: sending the first voltage adjustment and the second voltage adjustment; S4: judging whether a current reactive power of the dynamic reactive power compensation device is between a first predetermined reactive power and a second predetermined reactive power; S5: if yes, obtaining a third voltage adjustment of the generator and a fourth voltage adjustment of the dynamic reactive power compensation device; S6: sending the third voltage adjustment and the fourth voltage adjustment; repeating steps S1-S7 after a predetermined period of time; S7: if no, repeating steps S1-S7 after the predetermined period of time.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and benefits of Chinese Patent Application Serial No. 201410030530.0, filed with the State Intellectual Property Office of P. R. China on Jan. 22, 2014, the entire content of which is incorporated herein by reference. 
       FIELD 
       [0002]    The present disclosure relates to a power system evaluation and control field, and more particularly relates to a voltage control method and apparatus of a central bus in a power system. 
       BACKGROUND 
       [0003]    In recent years, problems of voltage stability of a power system frequently occur and some of them have caused enormous influence, so a voltage control method is particularly important. However, a conventional voltage control method is limited, such that the controlling response speed is slow. 
       SUMMARY 
       [0004]    Embodiments of the present disclosure seek to solve at least one of the problems existing in the related art to at least some extent. 
         [0005]    A first objective of the present disclosure is aimed to provide a voltage control method of a central bus in a power system. With the method, a dynamic reactive power compensation device is used as a control means, participating in a voltage control of the central bus in the power system, and a preventive control may be implemented by a dynamic reactive power optimization when the power system is out of order. 
         [0006]    The voltage control method of a central bus in a power system provided in the present disclosure comprises: S1: obtaining a predetermined voltage and a current voltage of the central bus; S2: obtaining a first voltage adjustment of a generator participating in a voltage control and a second voltage adjustment of a dynamic reactive power compensation device participating in the voltage control according to the predetermined voltage and the current voltage; S3: sending the first voltage adjustment to the generator participating in the voltage control and the second voltage adjustment to the dynamic reactive power compensation device participating in the voltage control to perform a voltage control; S4: judging whether a current reactive power of the dynamic reactive power compensation device is between a first predetermined reactive power and a second predetermined reactive power; S5: if the current reactive power of the dynamic reactive power compensation device is between the first predetermined reactive power and the second predetermined reactive power, obtaining a third voltage adjustment of a generator participating in an optimization control and a fourth voltage adjustment of a dynamic reactive power compensation device participating in the optimization control; S6: sending the third voltage adjustment to the generator participating in the optimization control and the fourth voltage adjustment to the dynamic reactive power compensation device participating in the optimization control to perform a dynamic reactive power optimization, and repeating steps S1-S7 after a predetermined period of time; S7: if the current reactive power of the dynamic reactive power compensation device is not between the first predetermined reactive power and the second predetermined reactive power, repeating steps S1-S7 after the predetermined period of time. 
         [0007]    In some embodiments, obtaining the first voltage adjustment and the second voltage adjustment according to formula (1): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         min 
                         
                           
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               g 
                             
                           
                           , 
                           
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               s 
                             
                           
                         
                       
                     
                     
                       
                         { 
                         
                           
                             
                               W 
                               p 
                             
                              
                             
                               
                                  
                                 
                                   
                                     a 
                                     · 
                                     
                                       ( 
                                       
                                         
                                           V 
                                           p 
                                         
                                         - 
                                         
                                           V 
                                           p 
                                           ref 
                                         
                                       
                                       ) 
                                     
                                   
                                   + 
                                   
                                     
                                       C 
                                       pg 
                                     
                                      
                                     Δ 
                                      
                                     
                                         
                                     
                                      
                                     
                                       V 
                                       g 
                                     
                                   
                                   + 
                                   
                                     
                                       C 
                                       ps 
                                     
                                      
                                     Δ 
                                      
                                     
                                         
                                     
                                      
                                     
                                       V 
                                       s 
                                     
                                   
                                 
                                  
                               
                               2 
                             
                           
                           + 
                           
                             
                               W 
                               q 
                             
                              
                             
                               ( 
                               
                                 
                                   
                                      
                                     
                                       Θ 
                                       g 
                                     
                                      
                                   
                                   2 
                                 
                                 + 
                                 
                                   
                                      
                                     Θ 
                                      
                                   
                                   2 
                                 
                               
                               ) 
                             
                           
                         
                         } 
                       
                     
                   
                   
                     
                       
                         s 
                         . 
                         t 
                         . 
                       
                     
                     
                       
                         
                           V 
                           p 
                           min 
                         
                         ≤ 
                         
                           
                             V 
                             p 
                           
                           + 
                           
                             
                               C 
                               pg 
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               g 
                             
                           
                           + 
                           
                             
                               C 
                               ps 
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               s 
                             
                           
                         
                         ≤ 
                         
                           V 
                           p 
                           max 
                         
                       
                     
                   
                   
                     
                       
                           
                       
                     
                     
                       
                         
                           Q 
                           g 
                           min 
                         
                         ≤ 
                         
                           
                             Q 
                             g 
                           
                           + 
                           
                             
                               C 
                               g 
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               g 
                             
                           
                           + 
                           
                             
                               C 
                               gs 
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               s 
                             
                           
                         
                         ≤ 
                         
                           Q 
                           g 
                           max 
                         
                       
                     
                   
                   
                     
                       
                           
                       
                     
                     
                       
                         
                           Q 
                           s 
                           min 
                         
                         ≤ 
                         
                           
                             Q 
                             s 
                           
                           + 
                           
                             
                               C 
                               sg 
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               g 
                             
                           
                           + 
                           
                             
                               C 
                               s 
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               s 
                             
                           
                         
                         ≤ 
                         
                           Q 
                           s 
                           max 
                         
                       
                     
                   
                   
                     
                       
                           
                       
                     
                     
                       
                         
                            
                           
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               g 
                             
                           
                            
                         
                         ≤ 
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             g 
                             max 
                           
                         
                       
                     
                   
                   
                     
                       
                           
                       
                     
                     
                       
                         
                           
                              
                             
                               Δ 
                                
                               
                                   
                               
                                
                               
                                 V 
                                 s 
                               
                             
                              
                           
                           ≤ 
                           
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               s 
                               max 
                             
                           
                         
                         , 
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where p represents the central bus, g represents the generator, s represents the dynamic reactive power compensation device, ΔV g  is a first voltage adjustment vector, ΔV s  is a second voltage adjustment vector, V p  is a current voltage vector of central buses, V p   ref  is a predetermined voltage vector of the central buses, C pg  is a sensitivity matrix of voltage deviations of the central buses relative to ΔV g , C ps  is a sensitivity matrix of the voltage deviations of the central buses relative to ΔV s , α is a gain coefficient vector of voltages of the central buses, Θ g  is a first margin vector of reactive powers of the generators participating in the voltage control, Θ s  is a second margin vector of reactive powers of the dynamic reactive power compensation devices participating in the voltage control, W p  is a first weight coefficient vector of the voltage deviations of the central buses, W q  is a second weight coefficient vector of reserve margins of the reactive powers of the generators and the dynamic reactive power compensation devices, V p   min  is a predetermined lower limit vector of the voltages of the central buses, V p   max  is a predetermined upper limit vector of the voltages of the central buses, Q g  is a current reactive power vector of the generators participating in the voltage control, Q g   min  is a lower limit vector of the reactive powers of the generators participating in the voltage control, Q g   max  is an upper limit vector of the reactive powers of the generators participating in the voltage control, C g  is a sensitivity matrix of a reactive power adjustment vector of the generators participating in the voltage control relative to ΔV g , C gs  is a sensitivity matrix of the reactive power adjustment vector of the generators participating in the voltage control relative to ΔV s , Q s  is a current reactive power vector of the dynamic reactive power compensation devices participating in the voltage control, Q s   min  is a lower limit vector of the reactive powers of the dynamic reactive power compensation devices participating in the voltage control, Q s   max  is an upper limit vector of the reactive powers of the dynamic reactive power compensation devices participating in the voltage control, C s  is a sensitivity matrix of a reactive power adjustment vector of the dynamic reactive power compensation devices participating in the voltage control relative to ΔV s , C sg  is a sensitivity matrix of the reactive power adjustment vector of the dynamic reactive power compensation devices participating in the voltage control relative to ΔV g , ΔV g   max  is a maximum adjustment vector allowed by the generators participating in the voltage control, ΔV s   max  is a maximum adjustment vector allowed by the dynamic reactive power compensation devices participating in the voltage control. 
         [0008]    In some embodiments, a i th  component in Θ g  is calculated according to formula (2): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       Θ 
                       
                         g 
                         i 
                       
                     
                     = 
                     
                       
                         
                           Q 
                           
                             g 
                             i 
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                               
                           
                            
                           
                             
                               C 
                               
                                 g 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 j 
                               
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                               
                           
                            
                           
                             
                               C 
                               
                                 gs 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 k 
                               
                             
                           
                         
                         - 
                         
                           Q 
                           
                             g 
                             i 
                           
                           min 
                         
                       
                       
                         
                           Q 
                           
                             g 
                             i 
                           
                           max 
                         
                         - 
                         
                           Q 
                           
                             g 
                             i 
                           
                           min 
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0000]    and a i th  component in Θ s  is calculated according to formula (3): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       Θ 
                       
                         s 
                         i 
                       
                     
                     = 
                     
                       
                         
                           Q 
                           
                             s 
                             i 
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                               
                           
                            
                           
                             
                               C 
                               
                                 s 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 j 
                               
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                               
                           
                            
                           
                             
                               C 
                               
                                 sg 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 k 
                               
                             
                           
                         
                         - 
                         
                           Q 
                           
                             s 
                             i 
                           
                           min 
                         
                       
                       
                         
                           Q 
                           
                             s 
                             i 
                           
                           max 
                         
                         - 
                         
                           Q 
                           
                             s 
                             i 
                           
                           min 
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where Θ g     i    is the i th  component in Θ g , Θ s     i    is the i th  component in Θ s , N s  is a number of the dynamic reactive power compensation devices participating in the voltage control, N g  is a number of the generators participating in the voltage control, Q g     i    a i th  component in Q g , C g     ij    is an element corresponding to a j th  generator participating in the voltage control of a i th  component in C g , ΔV g     j    is a j th  component corresponding to the j th  generator participating in the voltage control in ΔV g , C gs     ik    is an element corresponding to a k th  dynamic reactive power compensation device participating in the voltage control of a i th  component in C gs , ΔV s     k    is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the voltage control in ΔV s , Q g     i     min  is a i th  component in Q g   min , Q g     i     max  is a i th  component in Q g   max , Q s     i    is a i th  component in Q s , C s     ij    is an element corresponding to the j th  generator participating in the voltage control of a i th  component in C s , ΔV s     j    is a j th  component corresponding to the j th  generator participating in the voltage control in ΔV s , C sg     ik    is an element corresponding to the k th  dynamic reactive power compensation device participating in the voltage control of a i th  component in C sg , ΔV g     k    is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the voltage control in ΔV g , Q s     i     min  is a i th  component in Q s   min , Q s     i     max  is a i th  component in Q s   max . 
         [0009]    In some embodiments, the first predetermined reactive power is Q s   pre −0.1*Q s   max , the second predetermined reactive power is Q s   pre +0.1*Q s   max , where Q s   pre =(Q s   max +Q s   min )/2. 
         [0010]    In some embodiments, obtaining the third voltage adjustment and the fourth voltage adjustment according to formula (4): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         
                           min 
                           
                             
                               Δ 
                                
                               
                                   
                               
                                
                               
                                 V 
                                 g 
                                 ′ 
                               
                             
                             , 
                             
                               Δ 
                                
                               
                                   
                               
                                
                               
                                 V 
                                 s 
                                 ′ 
                               
                             
                           
                         
                          
                         
                           
                             { 
                             
                               
                                 
                                   W 
                                   s 
                                 
                                  
                                 
                                   
                                      
                                     
                                       μ 
                                       s 
                                     
                                      
                                   
                                   2 
                                 
                               
                               + 
                               
                                 
                                   W 
                                   g 
                                 
                                  
                                 
                                   
                                      
                                     
                                       μ 
                                       g 
                                     
                                      
                                   
                                   2 
                                 
                               
                             
                             } 
                           
                            
                           
                               
                           
                            
                           
                             s 
                             . 
                             t 
                             . 
                             
                               
 
                             
                              
                             
                               V 
                               p 
                             
                           
                         
                       
                       - 
                       
                         V 
                         band 
                       
                     
                     ≤ 
                     
                       
                         V 
                         p 
                       
                       + 
                       
                         
                           C 
                           pg 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                       + 
                       
                         
                           C 
                           ps 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           ′ 
                         
                       
                     
                     ≤ 
                     
                       
                         V 
                         p 
                       
                       + 
                       
                         V 
                         band 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       Q 
                       g 
                       min 
                     
                     ≤ 
                     
                       
                         Q 
                         g 
                       
                       + 
                       
                         
                           C 
                           g 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                       + 
                       
                         
                           C 
                           gs 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           ′ 
                         
                       
                     
                     ≤ 
                     
                       Q 
                       g 
                       max 
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       Q 
                       s 
                       min 
                     
                     ≤ 
                     
                       
                         Q 
                         s 
                       
                       + 
                       
                         
                           C 
                           sg 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                       + 
                       
                         
                           C 
                           s 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           ′ 
                         
                       
                     
                     ≤ 
                     
                       Q 
                       s 
                       max 
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                        
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                        
                     
                     ≤ 
                     
                       Δ 
                        
                       
                           
                       
                        
                       
                         V 
                         g 
                         max 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                          
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                             ′ 
                           
                         
                          
                       
                       ≤ 
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           max 
                         
                       
                     
                     , 
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where ΔV g ′ is a third voltage adjustment vector, ΔV s ′ is a fourth voltage adjustment vector, μ s  is a reactive power vector of the dynamic reactive power compensation devices participating in the optimization control, μ g  is a reactive power vector of the generators participating in the optimization control, W s  is a weight coefficient vector of the reactive powers of the dynamic reactive power compensation devices participating in the optimization control, W g  is a weight coefficient vector of the reactive powers of the generators participating in the optimization control, V p  is a current voltage vector of central buses, V band  is a voltage deadband value for controlling, C pg  is a sensitivity matrix of the voltage deviations of the central buses relative to ΔV g ′, C ps  is a sensitivity matrix of the voltage deviations of the central buses relative to ΔV s ′, Q g  is a current reactive power vector of the generators participating in the optimization control, Q g   min  is a lower limit vector of reactive powers of the generators participating in the optimization control, Q g   max  is an upper limit vector of the reactive powers of the generators participating in the optimization control, C g  is a sensitivity matrix of a reactive power adjustment vector of the generators participating in the optimization control relative to ΔV g ′, Q s  is a current reactive power vector of the dynamic reactive power compensation devices participating in the optimization control, Q s   min  is a lower limit vector of reactive powers of the dynamic reactive power compensation devices participating in the optimization control, Q s   max  is an upper limit vector of the reactive powers of the dynamic reactive power compensation devices participating in the optimization control, C s  is a sensitivity matrix of a reactive power adjustment vector of the dynamic reactive power compensation devices participating in the optimization control relative to ΔV s ′, C gs  is a sensitivity matrix of the reactive power adjustment vector of the generators participating in the optimization control relative to ΔV s ′, C sg  is a sensitivity matrix of the reactive power adjustment vector of the dynamic reactive power compensation devices participating in the optimization control relative to ΔV g ′, ΔV g ′ is a maximum adjustment vector allowed by the generators participating in the optimization control, ΔV s   max  is a maximum adjustment vector allowed by the dynamic reactive power compensation devices participating in the optimization control. 
         [0011]    In some embodiments, a i th  component in μ s  is calculated according to formula (5): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       μ 
                       si 
                     
                     = 
                     
                       
                         
                           Q 
                           si 
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                               
                           
                            
                           
                             
                               C 
                               
                                 s 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 j 
                               
                               ′ 
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                               
                           
                            
                           
                             
                               C 
                               
                                 sg 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 k 
                               
                               ′ 
                             
                           
                         
                         - 
                         
                           Q 
                           
                             s 
                             i 
                           
                           reference 
                         
                       
                       
                         
                           Q 
                           si 
                           max 
                         
                         - 
                         
                           Q 
                           si 
                           min 
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
         [0000]    and a i th  component in μ g  is calculated according to formula (6): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       μ 
                       gi 
                     
                     = 
                     
                       
                         
                           Q 
                           gi 
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                               
                           
                            
                           
                             
                               C 
                               
                                 g 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 j 
                               
                               ′ 
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                               
                           
                            
                           
                             
                               C 
                               
                                 gs 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 k 
                               
                               ′ 
                             
                           
                         
                         - 
                         
                           Q 
                           g 
                           aver 
                         
                       
                       
                         Q 
                         g 
                         sum 
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where μ si  is the i th  component in μ s , μ gi  is the i th  component in μ g , N S  is a number of the dynamic reactive power compensation devices participating in the optimization control, N g  is a number of the generators participating in the optimization control, Q s     i    is a i th  component in Q s , C s     ij    is an element corresponding to a i th  generator participating in the optimization control of a i th  component in C s , ΔV s     j   ′ is a j th  component corresponding to the j th  generator participating in the optimization control in ΔV s ′, C sg     ik    is an element corresponding to a k th  dynamic reactive power compensation device participating in the optimization control of a i th  component in C sg , ΔV g     k   ′ is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the optimization control in ΔV g ′, Q s     i     reference  is a predetermined margin of the dynamic reactive power compensation device participating in the optimization control, Q s     i     min  is a i th  component in Q s   min , Q s     i     max  is a i th  component in Q s   max , Q g     i    is a i th  component in Q g , C g     ij    is an element corresponding to the j th  generator participating in the optimization control of a i th  component in C g , ΔV g     j   ′ is a j th  component corresponding to the j th  generator participating in the optimization control in ΔV g ′, C gs     ik    is an element corresponding to the k th  dynamic reactive power compensation device participating in the optimization control of a i th  component in C gs , ΔV s     k   ′ is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the optimization control in ΔV s ′, Q g   aver  is an average value of reactive power of the generator participating in the optimization control, Q g   sum  is a sum of reactive power of the generator participating in the optimization control. 
         [0012]    A second objective of the present disclosure is aimed to provide a voltage control apparatus of a central bus in a power system. 
         [0013]    The voltage control apparatus of a central bus in a power system provided in the present disclosure comprises: a first obtaining module, configured to obtain a predetermined voltage and a current voltage of the central bus; a second obtaining module, configured to obtain a first voltage adjustment of a generator participating in a voltage control and a second voltage adjustment of a dynamic reactive power compensation device participating in the voltage control according to the predetermined voltage and the current voltage; a first sending module, configured to send the first voltage adjustment to the generator participating in the voltage control and the second voltage adjustment to the dynamic reactive power compensation device participating in the voltage control to perform a voltage control; a judging module, configured to judge whether a current reactive power of the dynamic reactive power compensation device is between a first predetermined reactive power and a second predetermined reactive power; a third obtaining module, configured to obtain a third voltage adjustment of a generator participating in an optimization control and a fourth voltage adjustment of a dynamic reactive power compensation device participating in the optimization control if the current reactive power of the dynamic reactive power compensation device is between the first predetermined reactive power and the second predetermined reactive power; a second sending module, configured to send the third voltage adjustment to the generator participating in the optimization control and the fourth voltage adjustment to the dynamic reactive power compensation device participating in the optimization control to perform a dynamic reactive power optimization. 
         [0014]    In some embodiments, the second obtaining module is further configured to obtain the first voltage adjustment and the second voltage adjustment according to formula (1): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         min 
                         
                           
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               g 
                             
                           
                           , 
                           
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               s 
                             
                           
                         
                       
                        
                       
                         
                           { 
                           
                             
                               
                                 W 
                                 p 
                               
                                
                               
                                 
                                    
                                   
                                     
                                       a 
                                       · 
                                       
                                         ( 
                                         
                                           
                                             V 
                                             p 
                                           
                                           - 
                                           
                                             V 
                                             p 
                                             ref 
                                           
                                         
                                         ) 
                                       
                                     
                                     + 
                                     
                                       
                                         C 
                                         pg 
                                       
                                        
                                       Δ 
                                        
                                       
                                           
                                       
                                        
                                       
                                         V 
                                         g 
                                       
                                     
                                     + 
                                     
                                       
                                         C 
                                         ps 
                                       
                                        
                                       Δ 
                                        
                                       
                                           
                                       
                                        
                                       
                                         V 
                                         s 
                                       
                                     
                                   
                                    
                                 
                                 2 
                               
                             
                             + 
                             
                               
                                 W 
                                 q 
                               
                                
                               
                                 ( 
                                 
                                   
                                     
                                        
                                       
                                         Θ 
                                         g 
                                       
                                        
                                     
                                     2 
                                   
                                   + 
                                   
                                     
                                        
                                       
                                         Θ 
                                         s 
                                       
                                        
                                     
                                     2 
                                   
                                 
                                 ) 
                               
                             
                           
                           } 
                         
                          
                         
                             
                         
                          
                         
                           s 
                           . 
                           t 
                           . 
                           
                             
 
                           
                            
                           
                               
                           
                            
                           
                             V 
                             p 
                             min 
                           
                         
                       
                     
                     ≤ 
                     
                       
                         V 
                         p 
                       
                       + 
                       
                         
                           C 
                           pg 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                         
                       
                       + 
                       
                         
                           C 
                           ps 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                         
                       
                     
                     ≤ 
                     
                       V 
                       p 
                       max 
                     
                   
                    
                   
                     
 
                   
                    
                   
                       
                   
                    
                   
                     
                       Q 
                       g 
                       min 
                     
                     ≤ 
                     
                       
                         Q 
                         g 
                       
                       + 
                       
                         
                           C 
                           g 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                         
                       
                       + 
                       
                         
                           C 
                           gs 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                         
                       
                     
                     ≤ 
                     
                       Q 
                       g 
                       max 
                     
                   
                    
                   
                     
 
                   
                    
                   
                       
                   
                    
                   
                     
                       Q 
                       s 
                       min 
                     
                     ≤ 
                     
                       
                         Q 
                         s 
                       
                       + 
                       
                         
                           C 
                           sg 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                         
                       
                       + 
                       
                         
                           C 
                           s 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                         
                       
                     
                     ≤ 
                     
                       Q 
                       s 
                       max 
                     
                   
                    
                   
                     
 
                   
                    
                   
                       
                   
                    
                   
                     
                        
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                         
                       
                        
                     
                     ≤ 
                     
                       Δ 
                        
                       
                           
                       
                        
                       
                         V 
                         g 
                         max 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                       
                   
                    
                   
                     
                       
                          
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                           
                         
                          
                       
                       ≤ 
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           max 
                         
                       
                     
                     , 
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where p represents the central bus, g represents the generator, s represents the dynamic reactive power compensation device, ΔV g  is a first voltage adjustment vector, ΔV s  is a second voltage adjustment vector, V p  is a current voltage vector of central buses, V p   ref  is a predetermined voltage vector of the central buses, C pg  is a sensitivity matrix of voltage deviations of the central buses relative to ΔV g , C ps  is a sensitivity matrix of the voltage deviations of the central buses relative to ΔV s′ , α is a gain coefficient vector of voltages of the central buses, Θ g  is a first margin vector of reactive powers of the generators participating in the voltage control, Θ s  is a second margin vector of reactive powers of the dynamic reactive power compensation devices participating in the voltage control, W p  is a first weight coefficient vector of the voltage deviations of the central buses, W q  is a second weight coefficient vector of reserve margins of the reactive powers of the generators and the dynamic reactive power compensation devices, V p   min  is a predetermined lower limit vector of the voltages of the central buses, V p   max  is a predetermined upper limit vector of the voltages of the central buses, Q g  is a current reactive power vector of the generators participating in the voltage control, Q g   min  is a lower limit vector of the reactive powers of the generators participating in the voltage control, Q g   max  is an upper limit vector of the reactive powers of the generators participating in the voltage control, C g  is a sensitivity matrix of a reactive power adjustment vector of the generators participating in the voltage control relative to ΔV g , C gs  is a sensitivity matrix of the reactive power adjustment vector of the generators participating in the voltage control relative to ΔV s′ , Q s  is a current reactive power vector of the dynamic reactive power compensation devices participating in the voltage control, Q s   min  is a lower limit vector of the reactive powers of the dynamic reactive power compensation devices participating in the voltage control, Q s   max  is an upper limit vector of the reactive powers of the dynamic reactive power compensation devices participating in the voltage control, C s  is a sensitivity matrix of a reactive power adjustment vector of the dynamic reactive power compensation devices participating in the voltage control relative to ΔV s , C sg  is a sensitivity matrix of the reactive power adjustment vector of the dynamic reactive power compensation devices participating in the voltage control relative to ΔV g , ΔV g   max  is a maximum adjustment vector allowed by the generators participating in the voltage control, ΔV s   max  is a maximum adjustment vector allowed by the dynamic reactive power compensation devices participating in the voltage control. 
         [0015]    In some embodiments, a i th  component in Θ g  is calculated according to formula (2): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       Θ 
                       
                         g 
                         i 
                       
                     
                     = 
                     
                       
                         
                           Q 
                           
                             g 
                             i 
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                             
                               C 
                               
                                 g 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 j 
                               
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                             
                               C 
                               
                                 gs 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 k 
                               
                             
                           
                         
                         - 
                         
                           Q 
                           
                             g 
                             i 
                           
                           min 
                         
                       
                       
                         
                           Q 
                           
                             g 
                             i 
                           
                           max 
                         
                         - 
                         
                           Q 
                           
                             g 
                             i 
                           
                           min 
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0000]    and a i th  component in Θ s  is calculated according to formula (3): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       Θ 
                       
                         s 
                         i 
                       
                     
                     = 
                     
                       
                         
                           Q 
                           
                             s 
                             i 
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                             
                               C 
                               
                                 s 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 j 
                               
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                             
                               C 
                               
                                 sg 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 k 
                               
                             
                           
                         
                         - 
                         
                           Q 
                           
                             s 
                             i 
                           
                           min 
                         
                       
                       
                         
                           Q 
                           
                             s 
                             i 
                           
                           max 
                         
                         - 
                         
                           Q 
                           
                             s 
                             i 
                           
                           min 
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where Θ g  is the i th  component in Θ g , Θ s     i    is the i th  component in Θ s , N S  is a number of the dynamic reactive power compensation devices participating in the voltage control, N g  is a number of the generators participating in the voltage control, Q g  is a i th  component in Q g , C g     ij    is an element corresponding to a j th  generator participating in the voltage control of a i th  component in C g , ΔV g     j    is a j th  component corresponding to the j th  generator participating in the voltage control in ΔV g , C gs     ik    is an element corresponding to a k th  dynamic reactive power compensation device participating in the voltage control of a i th  component in C gs , ΔV s     k    is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the voltage control in ΔV s , Q g     i     min  is a i th  component in Q g   min , Q g     i     max  is a i th  component in Q g   max , Q s     i    is a i th  component in Q s , C s     ij    is an element corresponding to the j th  generator participating in the voltage control of a i th  component in C s , ΔV s     j    is a j th  component corresponding to the j th  generator participating in the voltage control in ΔV s , C sg     ik    is an element corresponding to the k th  dynamic reactive power compensation device participating in the voltage control of a i th  component in C sg , ΔV g     k    is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the voltage control in ΔV g , Q s     i     min  is a i th  component in Q s   min , Q s     i     max  is a i th  component in Q s   max . 
         [0016]    In some embodiments, the first predetermined reactive power is Q s   pre −0.1*Q s   max , the second predetermined reactive power is Q s   pre +0.1*Q s   max , where Q s   pre =(Q s   max +Q s   min )/2. 
         [0017]    In some embodiments, the third obtaining module is further configured to obtain the third voltage adjustment and the fourth voltage adjustment according to formula (4): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       min 
                       
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             g 
                             ′ 
                           
                         
                         , 
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                             ′ 
                           
                         
                       
                     
                      
                     
                       { 
                       
                         
                           
                             W 
                             s 
                           
                            
                           
                             
                                
                               
                                 μ 
                                 s 
                               
                                
                             
                             2 
                           
                         
                         + 
                         
                           
                             W 
                             g 
                           
                            
                           
                             
                                
                               
                                 μ 
                                 g 
                               
                                
                             
                             2 
                           
                         
                       
                       } 
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         s 
                         . 
                         t 
                         . 
                         
                             
                         
                          
                         
                           V 
                           p 
                         
                       
                       - 
                       
                         V 
                         band 
                       
                     
                     ≤ 
                     
                       
                         V 
                         p 
                       
                       + 
                       
                         
                           C 
                           pg 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                       + 
                       
                         
                           C 
                           ps 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           ′ 
                         
                       
                     
                     ≤ 
                     
                       
                         V 
                         p 
                       
                       + 
                       
                         V 
                         band 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       Q 
                       g 
                       min 
                     
                     ≤ 
                     
                       
                         Q 
                         g 
                       
                       + 
                       
                         
                           C 
                           g 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                       + 
                       
                         
                           C 
                           gs 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           ′ 
                         
                       
                     
                     ≤ 
                     
                       Q 
                       g 
                       max 
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       Q 
                       s 
                       min 
                     
                     ≤ 
                     
                       
                         Q 
                         s 
                       
                       + 
                       
                         
                           C 
                           sg 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                       + 
                       
                         
                           C 
                           s 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           ′ 
                         
                       
                     
                     ≤ 
                     
                       Q 
                       g 
                       max 
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                        
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                        
                     
                     ≤ 
                     
                       Δ 
                        
                       
                           
                       
                        
                       
                         V 
                         g 
                         max 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                          
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                             ′ 
                           
                         
                          
                       
                       ≤ 
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           max 
                         
                       
                     
                     , 
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where ΔV g ′ is a third voltage adjustment vector, ΔV s ′ is a fourth voltage adjustment vector, μ s  is a reactive power vector of the dynamic reactive power compensation devices participating in the optimization control, μ g  is a reactive power vector of the generators participating in the optimization control, W s  is a weight coefficient vector of the reactive powers of the dynamic reactive power compensation devices participating in the optimization control, W g  is a weight coefficient vector of the reactive powers of the generators participating in the optimization control, V p  is a current voltage vector of central buses, V band  is a voltage deadband value for controlling, C pg  is a sensitivity matrix of the voltage deviations of the central buses relative to ΔV g ′, C ps  is a sensitivity matrix of the voltage deviations of the central buses relative to ΔV s ′, Q g  is a current reactive power vector of the generators participating in the optimization control, Q g   min  is a lower limit vector of reactive powers of the generators participating in the optimization control, Q g   max  is an upper limit vector of the reactive powers of the generators participating in the optimization control, C g  is a sensitivity matrix of a reactive power adjustment vector of the generators participating in the optimization control relative to ΔV g ′, Q s  is a current reactive power vector of the dynamic reactive power compensation devices participating in the optimization control, Q s   min  is a lower limit vector of reactive powers of the dynamic reactive power compensation devices participating in the optimization control, Q s   max  is an upper limit vector of the reactive powers of the dynamic reactive power compensation devices participating in the optimization control, C s  is a sensitivity matrix of a reactive power adjustment vector of the dynamic reactive power compensation devices participating in the optimization control relative to ΔV s ′, C gs  is a sensitivity matrix of the reactive power adjustment vector of the generators participating in the optimization control relative to ΔV s ′, C sg  is a sensitivity matrix of the reactive power adjustment vector of the dynamic reactive power compensation devices participating in the optimization control relative to ΔV g ′, ΔV g   max  is a maximum adjustment vector allowed by the generators participating in the optimization control, ΔV s   max  is a maximum adjustment vector allowed by the dynamic reactive power compensation devices participating in the optimization control. 
         [0018]    In some embodiments, a i th  component in μ s  is calculated according to formula (5): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       μ 
                       si 
                     
                     = 
                     
                       
                         
                           Q 
                           si 
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                             
                               C 
                               
                                 s 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 j 
                               
                               ′ 
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                             
                               C 
                               
                                 sg 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 k 
                               
                               ′ 
                             
                           
                         
                         - 
                         
                           Q 
                           
                             s 
                             i 
                           
                           reference 
                         
                       
                       
                         
                           Q 
                           si 
                           max 
                         
                         - 
                         
                           Q 
                           si 
                           min 
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
         [0000]    and a i th  component in μ g  is calculated according to formula (6): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       μ 
                       gi 
                     
                     = 
                     
                       
                         
                           Q 
                           gi 
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                             
                               C 
                               
                                 g 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 j 
                               
                               ′ 
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                             
                               C 
                               
                                 gs 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 k 
                               
                               ′ 
                             
                           
                         
                         - 
                         
                           Q 
                           g 
                           aver 
                         
                       
                       
                         Q 
                         g 
                         sum 
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where μ si  is the i th  component in μ s , μ gi  is the i th  component in μ g , N S  is a number of the dynamic reactive power compensation devices participating in the optimization control, N g  is a number of the generators participating in the optimization control, Q s     i    is a i th  component in Q s , C s     ij    is an element corresponding to a j th  generator participating in the optimization control of a i th  component in C s , ΔV s     j   ′ is a j th  component corresponding to the j th  generator participating in the optimization control in ΔV s ′, C sg     ik    is an element corresponding to a k th  dynamic reactive power compensation device participating in the optimization control of a i th  component in C sg , ΔV g     k   ′ is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the optimization control in ΔV g ′, Q s     i     reference  is a predetermined margin of the dynamic reactive power compensation device participating in the optimization control, Q s     i     min  is a i th  component in Q s   min , Q s     i     max  is a i th  component in Q s   max , Q g     i    is a i th  component in Q g , C g     ij    is an element corresponding to the j th  generator participating in the optimization control of a i th  component in C g , ΔV g     j   ′ is a j th  component corresponding to the j th  generator participating in the optimization control in ΔV g ′, C gs     ik    is an element corresponding to the k th  dynamic reactive power compensation device participating in the optimization control of a i th  component in C gs , ΔV s     k   ′ is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the optimization control in ΔV s ′, Q g   aver  is an average value of reactive power of the generator participating in the optimization control, Q g   sum  is a sum of reactive power of the generator participating in the optimization control. 
         [0019]    With the voltage control method and apparatus of a central bus in a power system provided by the present disclosure, a dynamic reactive power compensation device is used in a conventional voltage control model and a characteristic of fast adjustment of the dynamic reactive power compensation device is fully utilized, in addition, a dynamic reactive power optimization model is established and a reserve level of a reactive power in the power system may be improved by replacing the reactive power of the dynamic reactive power compensation device with the slow dynamic reactive power compensation device, further, an effective preventive control for transient voltage stability may be implemented by the method and a recovery effect after disturbances of voltages of the power system can be improved. 
         [0020]    A third objective of the present disclosure is aimed to provide computer readable storage medium, comprising a computer program for executing the voltage control method of a central bus in a power system according to the first objective of the present disclosure. 
         [0021]    The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures and the detailed description which follow more particularly exemplify illustrative embodiments. 
         [0022]    Additional aspects and advantages of embodiments of present disclosure will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    These and other aspects and advantages of embodiments of the present disclosure will become apparent and more readily appreciated from the following descriptions made with reference to the drawings, in which: 
           [0024]      FIG. 1  is a flow chart of the voltage control method of a central bus in a power system according to embodiments of the present disclosure; and 
           [0025]      FIG. 2  is block diagram of the voltage control apparatus of a central bus in a power system according to an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    Reference will be made in detail to embodiments of the present disclosure. The embodiments described herein with reference to drawings are explanatory, illustrative, and used to generally understand the present disclosure. The embodiments shall not be construed to limit the present disclosure. The same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the descriptions. 
         [0027]    In addition, terms such as “first” and “second” are used herein for purposes of description and are not intended to indicate or imply relative importance or significance. 
         [0028]    In the description, unless specified or limited otherwise, it is to be understood that phraseology and terminology used herein with reference to device or element orientation (for example, terms like “upper”, “lower”, and the like) should be construed to refer to the orientation as then described or as shown in the drawings under discussion for simplifying the description of the present disclosure, but do not alone indicate or imply that the device or element referred to must have a particular orientation. Moreover, it is not required that the present disclosure is constructed or operated in a particular orientation. 
         [0029]    Various embodiments and examples are provided in the following description to implement different structures of the present disclosure. In order to simplify the present disclosure, certain elements and settings will be described. However, these elements and settings are only by way of example and are not intended to limit the present disclosure. In addition, reference numerals may be repeated in different examples in the present disclosure. This repeating is for the purpose of simplification and clarity and does not refer to relations between different embodiments and/or settings. Furthermore, examples of different processes and materials are provided in the present disclosure. However, it would be appreciated by those skilled in the art that other processes and/or materials may be also applied. Moreover, a structure in which a first feature is “on” a second feature may include an embodiment in which the first feature directly contacts the second feature, and may also include an embodiment in which an additional feature is formed between the first feature and the second feature so that the first feature does not directly contact the second feature. 
         [0030]    In the following, the voltage control method and apparatus of a central bus in a power system according to embodiments of the present disclosure will be described in detail with reference to drawings. 
         [0031]    As shown in  FIG. 1 , the voltage control method of a central bus in a power system provided by the present disclosure includes the following steps. 
         [0032]    At step S 101 : a predetermined voltage and a current voltage of the central bus are obtained. Specifically, the predetermined voltage and the current voltage of the central bus can be obtained from a dispatching center of the power system. More specifically, at a current acquisition time, the predetermined voltage and the current voltage of the central bus corresponding to the current acquisition time can be obtained from the dispatching center of the power system. 
         [0033]    At step S 102 : a first voltage adjustment of a generator participating in a voltage control and a second voltage adjustment of a dynamic reactive power compensation device participating in the voltage control are obtained according to the predetermined voltage and the current voltage. 
         [0034]    In an embodiment, the first voltage adjustment and the second voltage adjustment may be obtained according to formula (1): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       min 
                       
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             g 
                           
                         
                         , 
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                           
                         
                       
                     
                      
                     
                       { 
                       
                         
                           
                             W 
                             p 
                           
                            
                           
                             
                                
                               
                                 
                                   a 
                                   · 
                                   
                                     ( 
                                     
                                       
                                         V 
                                         p 
                                       
                                       - 
                                       
                                         V 
                                         p 
                                         ref 
                                       
                                     
                                     ) 
                                   
                                 
                                 + 
                                 
                                   
                                     C 
                                     pg 
                                   
                                    
                                   Δ 
                                    
                                   
                                       
                                   
                                    
                                   
                                     V 
                                     g 
                                   
                                 
                                 + 
                                 
                                   
                                     C 
                                     ps 
                                   
                                    
                                   Δ 
                                    
                                   
                                       
                                   
                                    
                                   
                                     V 
                                     s 
                                   
                                 
                               
                                
                             
                             2 
                           
                         
                         + 
                         
                           
                             W 
                             q 
                           
                            
                           
                             ( 
                             
                               
                                 
                                    
                                   
                                     Θ 
                                     g 
                                   
                                    
                                 
                                 2 
                               
                               + 
                               
                                 
                                    
                                   
                                     Θ 
                                     s 
                                   
                                    
                                 
                                 2 
                               
                             
                             ) 
                           
                         
                       
                       } 
                     
                   
                    
                   
                     
 
                   
                    
                   
                       
                   
                    
                   
                     
                       
                         s 
                         . 
                         t 
                         . 
                         
                             
                         
                          
                         
                           V 
                           p 
                           min 
                         
                       
                       ≤ 
                       
                         
                           V 
                           p 
                         
                         + 
                         
                           
                             C 
                             pg 
                           
                            
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             g 
                           
                         
                         + 
                         
                           
                             C 
                             ps 
                           
                            
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                           
                         
                       
                       ≤ 
                       
                         
                           V 
                           p 
                           max 
                         
                          
                         
                           
 
                         
                          
                         
                             
                         
                          
                         
                           Q 
                           g 
                           min 
                         
                       
                       ≤ 
                       
                         
                           Q 
                           g 
                         
                         + 
                         
                           
                             C 
                             g 
                           
                            
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             g 
                           
                         
                         + 
                         
                           
                             C 
                             gs 
                           
                            
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                           
                         
                       
                       ≤ 
                       
                         
                           Q 
                           g 
                           max 
                         
                          
                         
                           
 
                         
                          
                         
                             
                         
                          
                         
                           Q 
                           s 
                           min 
                         
                       
                       ≤ 
                       
                         
                           Q 
                           s 
                         
                         + 
                         
                           
                             C 
                             sg 
                           
                            
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             g 
                           
                         
                         + 
                         
                           
                             C 
                             s 
                           
                            
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                           
                         
                       
                       ≤ 
                       
                         
                           Q 
                           g 
                           max 
                         
                          
                         
                           
 
                         
                          
                         
                             
                         
                          
                         
                            
                           
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               g 
                             
                           
                            
                         
                       
                       ≤ 
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           max 
                         
                          
                         
                           
 
                         
                          
                         
                             
                         
                          
                         
                            
                           
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               s 
                             
                           
                            
                         
                       
                       ≤ 
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           max 
                         
                       
                     
                     , 
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where p represents the central bus, g represents the generator, s represents the dynamic reactive power compensation device, ΔV g  is a first voltage adjustment vector, ΔV s  is a second voltage adjustment vector, V p  is a current voltage vector of central buses, V p   ref  is a predetermined voltage vector of the central buses, C pg  is a sensitivity matrix of voltage deviations of the central buses relative to ΔV g , C ps  is a sensitivity matrix of the voltage deviations of the central buses relative to ΔV s′ , α is a gain coefficient vector of voltages of the central buses and a range of α is 1-10, Θ g  is a first margin vector of reactive powers of the generators participating in the voltage control, Θ s  is a second margin vector of reactive powers of the dynamic reactive power compensation devices participating in the voltage control, W p  is a first weight coefficient vector of the voltage deviations of the central buses and a range of W p  is 0.1-1, W q  is a second weight coefficient vector of reserve margins of the reactive powers of the generators and the dynamic reactive power compensation devices and a range of W q  is 10-100, the reserve margin is the percentage of counts of the current reactive powers on the largest providable reactive powers, V p   min  is a predetermined lower limit vector of the voltages of the central buses, V p   max  is a predetermined upper limit vector of the voltages of the central buses, Q g  is a current reactive power vector of the generators participating in the voltage control, Q g   min  is a lower limit vector of the reactive powers of the generators participating in the voltage control, Q g   max  is an upper limit vector of the reactive powers of the generators participating in the voltage control, C g  is a sensitivity matrix of a reactive power adjustment vector of the generators participating in the voltage control relative to ΔV g , C gs  is a sensitivity matrix of the reactive power adjustment vector of the generators participating in the voltage control relative to ΔV s′ , Q s  is a current reactive power vector of the dynamic reactive power compensation devices participating in the voltage control, Q s   min  is a lower limit vector of the reactive powers of the dynamic reactive power compensation devices participating in the voltage control, Q s   max  is an upper limit vector of the reactive powers of the dynamic reactive power compensation devices participating in the voltage control, C s  is a sensitivity matrix of a reactive power adjustment vector of the dynamic reactive power compensation devices participating in the voltage control relative to ΔV s , C sg  is a sensitivity matrix of the reactive power adjustment vector of the dynamic reactive power compensation devices participating in the voltage control relative to ΔV g , ΔV g   max  is a maximum adjustment vector allowed by the generators participating in the voltage control, ΔV s   max  is a maximum adjustment vector allowed by the dynamic reactive power compensation devices participating in the voltage control. 
         [0035]    In an embodiment, all parameters in formula (1) can be obtained from the dispatching center of the power system. 
         [0036]    In an embodiment, a i th  component in Θ g  may be calculated according to formula (2): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       Θ 
                       
                         g 
                         i 
                       
                     
                     = 
                     
                       
                         
                           Q 
                           
                             g 
                             i 
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                             
                               C 
                               
                                 g 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 j 
                               
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                             
                               C 
                               
                                 gs 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 k 
                               
                             
                           
                         
                         - 
                         
                           Q 
                           
                             g 
                             i 
                           
                           min 
                         
                       
                       
                         
                           Q 
                           
                             g 
                             i 
                           
                           max 
                         
                         - 
                         
                           Q 
                           
                             g 
                             i 
                           
                           min 
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0000]    and a i th  component in Θ s  may be calculated according to formula (3): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       Θ 
                       
                         s 
                         i 
                       
                     
                     = 
                     
                       
                         
                           Q 
                           
                             s 
                             i 
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                             
                               C 
                               
                                 s 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 j 
                               
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                             
                               C 
                               
                                 sg 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 k 
                               
                             
                           
                         
                         - 
                         
                           Q 
                           
                             s 
                             i 
                           
                           min 
                         
                       
                       
                         
                           Q 
                           
                             s 
                             i 
                           
                           max 
                         
                         - 
                         
                           Q 
                           
                             s 
                             i 
                           
                           min 
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where Θ g     i    is the i th  component in Θ g , Θ s     i    is the i th  component in Θ s , N s  is a number of the dynamic reactive power compensation devices participating in the voltage control, N g  is a number of the generators participating in the voltage control, Q g     i    is a i th  component in Q g , C g     ij    is an element corresponding to a j th  generator participating in the voltage control of a i th  component in C g , ΔV g     j    is a j th  component corresponding to the j th  generator participating in the voltage control in ΔV g , C gs     ik    is an element corresponding to a k th  dynamic reactive power compensation device participating in the voltage control of a i th  component in C gs , ΔV s     k    is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the voltage control in ΔV s , Q g     i     min  is a i th  component in Q g   min , Q g     i     max  is a i th  component in Q g   max , Q s     i    is a i th  component in Q s , C s     ij    is an element corresponding to the j th  generator participating in the voltage control of a i th  component in C s , ΔV s     j    is a j th  component corresponding to the j th  generator participating in the voltage control in ΔV s , C sg     ik    is an element corresponding to the k th  dynamic reactive power compensation device participating in the voltage control of a i th  component in C sg , ΔV g     k    is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the voltage control in ΔV g , Q s     i     min  is a i th  component in Q s   min , Q s     i     max  is a i th  component in Q s   max . 
         [0037]    At step S 103 : the first voltage adjustment is sent to the generator participating in the voltage control and the second voltage adjustment is sent to the dynamic reactive power compensation device participating in the voltage control to perform a voltage control. 
         [0038]    Specifically, the first voltage adjustment and the second voltage adjustment can be as control instructions and sent to the corresponding generator and the dynamic reactive power compensation device, each generator and each dynamic reactive power compensation device perform the voltage control according to the corresponding control instruction at a voltage control phase of the central bus. 
         [0039]    At step S 104 : it is judged whether a current reactive power of the dynamic reactive power compensation device is between a first predetermined reactive power and a second predetermined reactive power. 
         [0040]    In an embodiment, the first predetermined reactive power is Q pre −0.1*Q s   max , the second predetermined reactive power is Q s   pre +0.1*Q s   max , where Q s   pre =(Q s   max +Q s   min )/2. 
         [0041]    At step S 105 : if the current reactive power of the dynamic reactive power compensation device is between the first predetermined reactive power and the second predetermined reactive power, a third voltage adjustment of a generator participating in an optimization control and a fourth voltage adjustment of a dynamic reactive power compensation device participating in the optimization control are obtained. 
         [0042]    At step S 106 , the third voltage adjustment is sent to the generator participating in the optimization control and the fourth voltage adjustment is sent to the dynamic reactive power compensation device participating in the optimization control to perform a dynamic reactive power optimization and steps S 101 -S 107  are repeated after a predetermined period of time. 
         [0043]    Specifically, the third voltage adjustment and the fourth voltage adjustment can be as control instructions and sent to the corresponding generator and the dynamic reactive power compensation device, each generator and each dynamic reactive power compensation device perform the voltage control according to the corresponding control instruction at a reactive power margin optimization phase of the central bus. 
         [0044]    In an embodiment, the predetermined period of time may be five to ten minutes. 
         [0045]    In an embodiment, the third voltage adjustment and the fourth voltage adjustment may be obtained according to formula (4): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       min 
                       
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             g 
                             ′ 
                           
                         
                         , 
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                             ′ 
                           
                         
                       
                     
                      
                     
                       { 
                       
                         
                           
                             W 
                             s 
                           
                            
                           
                             
                                
                               
                                 μ 
                                 s 
                               
                                
                             
                             2 
                           
                         
                         + 
                         
                           
                             W 
                             g 
                           
                            
                           
                             
                                
                               
                                 μ 
                                 g 
                               
                                
                             
                             2 
                           
                         
                       
                       } 
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         s 
                         . 
                         t 
                         . 
                         
                             
                         
                          
                         
                           V 
                           p 
                         
                       
                       - 
                       
                         V 
                         band 
                       
                     
                     ≤ 
                     
                       
                         V 
                         p 
                       
                       + 
                       
                         
                           C 
                           pg 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                       + 
                       
                         
                           C 
                           ps 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           ′ 
                         
                       
                     
                     ≤ 
                     
                       
                         V 
                         p 
                       
                       + 
                       
                         V 
                         band 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       Q 
                       g 
                       min 
                     
                     ≤ 
                     
                       
                         Q 
                         g 
                       
                       + 
                       
                         
                           C 
                           g 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                       + 
                       
                         
                           C 
                           gs 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           ′ 
                         
                       
                     
                     ≤ 
                     
                       Q 
                       g 
                       max 
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       Q 
                       s 
                       min 
                     
                     ≤ 
                     
                       
                         Q 
                         s 
                       
                       + 
                       
                         
                           C 
                           sg 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                       + 
                       
                         
                           C 
                           s 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           ′ 
                         
                       
                     
                     ≤ 
                     
                       Q 
                       g 
                       max 
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                        
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                        
                     
                     ≤ 
                     
                       Δ 
                        
                       
                           
                       
                        
                       
                         V 
                         g 
                         max 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                          
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                             ′ 
                           
                         
                          
                       
                       ≤ 
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           max 
                         
                       
                     
                     , 
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where ΔV g ′ is a third voltage adjustment vector, ΔV s ′ is a fourth voltage adjustment vector, μ s  is a reactive power vector of the dynamic reactive power compensation devices participating in the optimization control, μ g  is a reactive power vector of the generators participating in the optimization control, W s  is a weight coefficient vector of the reactive powers of the dynamic reactive power compensation devices participating in the optimization control and a range of W s  is 0.1-1, W g  is a weight coefficient vector of the reactive powers of the generators participating in the optimization control and a range of W g  is 10-100, V p  is a current voltage vector of central buses, V band  is a voltage deadband value for controlling, C pg  is a sensitivity matrix of the voltage deviations of the central buses relative to ΔV g ′, C ps  is a sensitivity matrix of the voltage deviations of the central buses relative to ΔV s ′, Q g  is a current reactive power vector of the generators participating in the optimization control, Q g   min  is a lower limit vector of reactive powers of the generators participating in the optimization control, Q g   max  is an upper limit vector of the reactive powers of the generators participating in the optimization control, C g  is a sensitivity matrix of a reactive power adjustment vector of the generators participating in the optimization control relative to ΔV g ′, Q s  is a current reactive power vector of the dynamic reactive power compensation devices participating in the optimization control, Q s   min  is a lower limit vector of reactive powers of the dynamic reactive power compensation devices participating in the optimization control, Q s   max  is an upper limit vector of the reactive powers of the dynamic reactive power compensation devices participating in the optimization control, C s  is a sensitivity matrix of a reactive power adjustment vector of the dynamic reactive power compensation devices participating in the optimization control relative to ΔV s ′, C gs  is a sensitivity matrix of the reactive power adjustment vector of the generators participating in the optimization control relative to ΔV s ′, C sg  is a sensitivity matrix of the reactive power adjustment vector of the dynamic reactive power compensation devices participating in the optimization control relative to ΔV g ′, ΔV g   max  is a maximum adjustment vector allowed by the generators participating in the optimization control, ΔV s   max  is a maximum adjustment vector allowed by the dynamic reactive power compensation devices participating in the optimization control. 
         [0046]    In an embodiment, a i th  component in μ s  may be calculated according to formula (5): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       μ 
                       si 
                     
                     = 
                     
                       
                         
                           Q 
                           si 
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                             
                               C 
                               
                                 s 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 j 
                               
                               ′ 
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                             
                               C 
                               
                                 sg 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 k 
                               
                               ′ 
                             
                           
                         
                         - 
                         
                           Q 
                           
                             s 
                             i 
                           
                           reference 
                         
                       
                       
                         
                           Q 
                           si 
                           max 
                         
                         - 
                         
                           Q 
                           si 
                           min 
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
         [0000]    and a i th  component in μ g  may be calculated according to formula (6): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       μ 
                       gi 
                     
                     = 
                     
                       
                         
                           Q 
                           gi 
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                             
                               C 
                               
                                 g 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 j 
                               
                               ′ 
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                             
                               C 
                               
                                 gs 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 k 
                               
                               ′ 
                             
                           
                         
                         - 
                         
                           Q 
                           g 
                           aver 
                         
                       
                       
                         Q 
                         g 
                         sum 
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where μ si  is the i th  component in μ s , μ gi  is the i th  component in μ g , N s  is a number of the dynamic reactive power compensation devices participating in the optimization control, N g  is a number of the generators participating in the optimization control, Q s     i    is a i th  component in Q s , C s     ij    is an element corresponding to a j th  generator participating in the optimization control of a i th  component in C s , ΔV s     j   ′ is a j th  component corresponding to the j th  generator participating in the optimization control in ΔV s ′, C sg     ik    is an element corresponding to a k th  dynamic reactive power compensation device participating in the optimization control of a i th  component in C sg , ΔV g     k   ′ is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the optimization control in ΔV g ′, Q s     i     reference  is a predetermined margin of the dynamic reactive power compensation device participating in the optimization control, Q s     i     min  is a i th  component in Q s   min , Q i     s     max  a i th  component in Q s   max , Q g     i    is a i th  component in Q g , C g     ij    is an element corresponding to the j th  generator participating in the optimization control of a i th  component in C g , ΔV g     j   ′ is a j th  component corresponding to the j th  generator participating in the optimization control in ΔV g ′, C gs     ik    is an element corresponding to the k th  dynamic reactive power compensation device participating in the optimization control of a i th  component in C gs , ΔV s     k   ′ is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the optimization control in ΔV s ′, Q g   aver  is an average value of reactive power of the generator participating in the optimization control, Q g   sum  is a sum of reactive power of the generator participating in the optimization control. 
         [0047]    At step S 107 : if the current reactive power of each dynamic reactive power compensation device is not between the first predetermined reactive power and the second predetermined reactive power, steps S 101 -S 107  are repeated after the predetermined period of time. 
         [0048]    The present disclosure also provides a voltage control apparatus of a central bus in a power system. 
         [0049]      FIG. 2  is block diagram of the voltage control apparatus of a central bus in a power system according to an embodiment of the present disclosure. 
         [0050]    As shown in  FIG. 2 , the apparatus includes a first obtaining module  110 , a second obtaining module  120 , a first sending module  130 , a judging module  140 , a third obtaining module  150  and a second sending module  160 . 
         [0051]    Specifically, the first obtaining module  110  is configured to obtain a predetermined voltage and a current voltage of the central bus. More specifically, the predetermined voltage and the current voltage of the central bus can be obtained from a dispatching center of the power system by the first obtaining module  110 . In particular, at a current acquisition time, the predetermined voltage and the current voltage of the central bus corresponding to the current acquisition time can be obtained from the dispatching center of the power system by the first obtaining module  110 . 
         [0052]    The second obtaining module  120  is configured to obtain a first voltage adjustment of a generator participating in a voltage control and a second voltage adjustment of a dynamic reactive power compensation device participating in the voltage control according to the predetermined voltage and the current voltage. 
         [0053]    In an embodiment, the second obtaining module  120  is further configured to obtain the first voltage adjustment and the second voltage adjustment according to formula (1): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       min 
                       
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             g 
                           
                         
                         , 
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                           
                         
                       
                     
                      
                     
                       { 
                       
                         
                           
                             W 
                             p 
                           
                            
                           
                             
                                
                               
                                 
                                   a 
                                   · 
                                   
                                     ( 
                                     
                                       
                                         V 
                                         p 
                                       
                                       - 
                                       
                                         V 
                                         p 
                                         ref 
                                       
                                     
                                     ) 
                                   
                                 
                                 + 
                                 
                                   
                                     C 
                                     pg 
                                   
                                    
                                   Δ 
                                    
                                   
                                       
                                   
                                    
                                   
                                     V 
                                     g 
                                   
                                 
                                 + 
                                 
                                   
                                     C 
                                     ps 
                                   
                                    
                                   Δ 
                                    
                                   
                                       
                                   
                                    
                                   
                                     V 
                                     s 
                                   
                                 
                               
                                
                             
                             2 
                           
                         
                         + 
                         
                           
                             W 
                             q 
                           
                            
                           
                             ( 
                             
                               
                                 
                                    
                                   
                                     Θ 
                                     g 
                                   
                                    
                                 
                                 2 
                               
                               + 
                               
                                 
                                    
                                   
                                     Θ 
                                     s 
                                   
                                    
                                 
                                 2 
                               
                             
                             ) 
                           
                         
                       
                       } 
                     
                   
                    
                   
                     
 
                   
                    
                   
                       
                   
                    
                   
                     
                       
                         s 
                         . 
                         t 
                         . 
                         
                             
                         
                          
                         
                           V 
                           p 
                           min 
                         
                       
                       ≤ 
                       
                         
                           V 
                           p 
                         
                         + 
                         
                           
                             C 
                             pg 
                           
                            
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             g 
                           
                         
                         + 
                         
                           
                             C 
                             ps 
                           
                            
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                           
                         
                       
                       ≤ 
                       
                         
                           V 
                           p 
                           max 
                         
                          
                         
                           
 
                         
                          
                         
                             
                         
                          
                         
                           Q 
                           g 
                           min 
                         
                       
                       ≤ 
                       
                         
                           Q 
                           g 
                         
                         + 
                         
                           
                             C 
                             g 
                           
                            
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             g 
                           
                         
                         + 
                         
                           
                             C 
                             gs 
                           
                            
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                           
                         
                       
                       ≤ 
                       
                         
                           Q 
                           g 
                           max 
                         
                          
                         
                           
 
                         
                          
                         
                             
                         
                          
                         
                           Q 
                           s 
                           min 
                         
                       
                       ≤ 
                       
                         
                           Q 
                           s 
                         
                         + 
                         
                           
                             C 
                             sg 
                           
                            
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             g 
                           
                         
                         + 
                         
                           
                             C 
                             s 
                           
                            
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                           
                         
                       
                       ≤ 
                       
                         
                           Q 
                           g 
                           max 
                         
                          
                         
                           
 
                         
                          
                         
                             
                         
                          
                         
                            
                           
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               g 
                             
                           
                            
                         
                       
                       ≤ 
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           max 
                         
                          
                         
                           
 
                         
                          
                         
                             
                         
                          
                         
                            
                           
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               s 
                             
                           
                            
                         
                       
                       ≤ 
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           max 
                         
                       
                     
                     , 
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where p represents the central bus, g represents the generator, s represents the dynamic reactive power compensation device, ΔV g  is the first voltage adjustment vector, ΔV s  is the second voltage adjustment vector, V p  is a current voltage vector of central buses, V p   ref  is a predetermined voltage vector of the central buses, C pg  is a sensitivity matrix of voltage deviations of the central buses relative to ΔV g , C ps  is a sensitivity matrix of the voltage deviations of the central buses relative to ΔV s′ , α is a gain coefficient vector of voltages of the central buses and a range of α is 1-10, Θ g  is a first margin vector of reactive powers of the generators participating in the voltage control, Θ s  is a second margin vector of reactive powers of the dynamic reactive power compensation devices participating in the voltage control, W p  is a first weight coefficient vector of the voltage deviations of the central buses and a range of W p  is 0.1-1, W q  is a second weight coefficient vector of reserve margins of the reactive powers of the generators and the dynamic reactive power compensation devices and a range of W q  is 10-100, V p   min  is a predetermined lower limit vector of the voltages of the central buses, V p   max  is a predetermined upper limit vector of the voltages of the central buses, Q g  is a current reactive power vector of the generators participating in the voltage control, Q g   min  is a lower limit vector of the reactive powers of the generators participating in the voltage control, Q g   max  is an upper limit vector of the reactive powers of the generators participating in the voltage control, C g  is a sensitivity matrix of a reactive power adjustment vector of the generators participating in the voltage control relative to ΔV g , C gs  is a sensitivity matrix of the reactive power adjustment vector of the generators participating in the voltage control relative to ΔV s′ , Q s  is a current reactive power vector of the dynamic reactive power compensation devices participating in the voltage control, Q s   min  is a lower limit vector of the reactive powers of the dynamic reactive power compensation devices participating in the voltage control, Q s   max  is an upper limit vector of the reactive powers of the dynamic reactive power compensation devices participating in the voltage control, C s  is a sensitivity matrix of a reactive power adjustment vector of the dynamic reactive power compensation devices participating in the voltage control relative to ΔV s , C sg  is a sensitivity matrix of the reactive power adjustment vector of the dynamic reactive power compensation devices participating in the voltage control relative to ΔV g , ΔV g   max  is a maximum adjustment vector allowed by the generators participating in the voltage control, ΔV s   max  is a maximum adjustment vector allowed by the dynamic reactive power compensation devices participating in the voltage control. 
         [0054]    In an embodiment, all parameters in formula (1) can be obtained from the dispatching center of the power system. 
         [0055]    In an embodiment, a i th  component in Θ g  may be calculated according to formula (2): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       Θ 
                       
                         g 
                         i 
                       
                     
                     = 
                     
                       
                         
                           Q 
                           
                             g 
                             i 
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                             
                               C 
                               
                                 g 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 j 
                               
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                             
                               C 
                               
                                 gs 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 k 
                               
                             
                           
                         
                         - 
                         
                           Q 
                           
                             g 
                             i 
                           
                           min 
                         
                       
                       
                         
                           Q 
                           
                             g 
                             i 
                           
                           max 
                         
                         - 
                         
                           Q 
                           
                             g 
                             i 
                           
                           min 
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0000]    and a i th  component in Θ s  may be calculated according to formula (3): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       Θ 
                       
                         s 
                         i 
                       
                     
                     = 
                     
                       
                         
                           Q 
                           
                             s 
                             i 
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                             
                               C 
                               
                                 s 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 j 
                               
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                             
                               C 
                               
                                 sg 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 k 
                               
                             
                           
                         
                         - 
                         
                           Q 
                           
                             s 
                             i 
                           
                           min 
                         
                       
                       
                         
                           Q 
                           
                             s 
                             i 
                           
                           max 
                         
                         - 
                         
                           Q 
                           
                             s 
                             i 
                           
                           min 
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where Θ g     i    is the i th  component in Θ g , Θ s  is the i th  component in Θ s , N S  is a number of the dynamic reactive power compensation devices participating in the voltage control, N g  is a number of the generators participating in the voltage control, Q g     i    is a i th  component in Q g , C g     ij    is an element corresponding to a j th  generator participating in the voltage control of a i th  component in C g , ΔV g     j    is a j th  component corresponding to the j th  generator participating in the voltage control in ΔV g , C gs     ik    is an element corresponding to a k th  dynamic reactive power compensation device participating in the voltage control of a i th  component in C gs , V s     k    is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the voltage control in ΔV s , Q g     i     min  is a i th  component in Q g   min , Q g     i     max  is a i th  component in Q g   max , Q s     i    is a i th  component in Q s , C s     ij    is an element corresponding to the j th  generator participating in the voltage control of a i th  component in C s , ΔV s     j    is a j th  component corresponding to the j th  generator participating in the voltage control in ΔV s , C sg     ik    is an element corresponding to the k th  dynamic reactive power compensation device participating in the voltage control of a i th  component in C sg , ΔV g     k    is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the voltage control in ΔV g , Q s     i     min  is a i th  component in Q s   min , Q s     i     max  is a i th  component in Q s   max . 
         [0056]    The first sending module  130  is configured to send the first voltage adjustment to the generator participating in the voltage control and the second voltage adjustment to the dynamic reactive power compensation device participating in the voltage control to perform a voltage control. 
         [0057]    More specifically, the first voltage adjustment and the second voltage adjustment can be as control instructions and sent to the corresponding generator and the dynamic reactive power compensation device by the first sending module  130 , each generator and each dynamic reactive power compensation device perform the voltage control according to the corresponding control instruction at a voltage control phase of the central bus. 
         [0058]    The judging module  140  is configured to judge whether a current reactive power of the dynamic reactive power compensation device is between a first predetermined reactive power and a second predetermined reactive power. 
         [0059]    In an embodiment, the first predetermined reactive power is Q s   pre −0.1*Q s   max , the second predetermined reactive power is Q s   pre +0.1*Q s   max , where Q s   pre =(Q s   max +Q s   min )/2. 
         [0060]    The third obtaining module  150  is configured to obtain a third voltage adjustment of a generator participating in an optimization control and a fourth voltage adjustment of a dynamic reactive power compensation device participating in the optimization control if the current reactive power of the dynamic reactive power compensation device is between the first predetermined reactive power and the second predetermined reactive power. 
         [0061]    In an embodiment, the third obtaining module  150  is further configured to obtain the third voltage adjustment and the fourth voltage adjustment according to formula (4): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       min 
                       
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             g 
                             ′ 
                           
                         
                         , 
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                             ′ 
                           
                         
                       
                     
                      
                     
                       { 
                       
                         
                           
                             W 
                             s 
                           
                            
                           
                             
                                
                               
                                 μ 
                                 s 
                               
                                
                             
                             2 
                           
                         
                         + 
                         
                           
                             W 
                             g 
                           
                            
                           
                             
                                
                               
                                 μ 
                                 g 
                               
                                
                             
                             2 
                           
                         
                       
                       } 
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         s 
                         . 
                         t 
                         . 
                         
                             
                         
                          
                         
                           V 
                           p 
                         
                       
                       - 
                       
                         V 
                         band 
                       
                     
                     ≤ 
                     
                       
                         V 
                         p 
                       
                       + 
                       
                         
                           C 
                           pg 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                       + 
                       
                         
                           C 
                           ps 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           ′ 
                         
                       
                     
                     ≤ 
                     
                       
                         V 
                         p 
                       
                       + 
                       
                         V 
                         band 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       Q 
                       g 
                       min 
                     
                     ≤ 
                     
                       
                         Q 
                         g 
                       
                       + 
                       
                         
                           C 
                           g 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                       + 
                       
                         
                           C 
                           gs 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           ′ 
                         
                       
                     
                     ≤ 
                     
                       Q 
                       g 
                       max 
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       Q 
                       s 
                       min 
                     
                     ≤ 
                     
                       
                         Q 
                         s 
                       
                       + 
                       
                         
                           C 
                           sg 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                       + 
                       
                         
                           C 
                           s 
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           ′ 
                         
                       
                     
                     ≤ 
                     
                       Q 
                       g 
                       max 
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                        
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           g 
                           ′ 
                         
                       
                        
                     
                     ≤ 
                     
                       Δ 
                        
                       
                           
                       
                        
                       
                         V 
                         g 
                         max 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                          
                         
                           Δ 
                            
                           
                               
                           
                            
                           
                             V 
                             s 
                             ′ 
                           
                         
                          
                       
                       ≤ 
                       
                         Δ 
                          
                         
                             
                         
                          
                         
                           V 
                           s 
                           max 
                         
                       
                     
                     , 
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where ΔV g ′ is the third voltage adjustment vector, ΔV s ′ is the fourth voltage adjustment vector, μ s  is a reactive power vector of the dynamic reactive power compensation devices participating in the optimization control, μ g  is a reactive power vector of the generators participating in the optimization control, W s  is a weight coefficient vector of the reactive powers of the dynamic reactive power compensation devices participating in the optimization control and a range of W s  is 0.1-1, W g  is a weight coefficient vector of the reactive powers of the generators participating in the optimization control and a range of W g  is 10-100, V p  is a current voltage vector of central buses, V band  is a voltage deadband value for controlling, C pg  is a sensitivity matrix of the voltage deviations of the central buses relative to ΔV g ′, C ps  is a sensitivity matrix of the voltage deviations of the central buses relative to ΔV g ′, Q g  is a current reactive power vector of the generators participating in the optimization control, Q g   min  is a lower limit vector of reactive powers of the generators participating in the optimization control, Q g   max  is an upper limit vector of the reactive powers of the generators participating in the optimization control, C g  is a sensitivity matrix of a reactive power adjustment vector of the generators participating in the optimization control relative to ΔV g ′, Q s  is a current reactive power vector of the dynamic reactive power compensation devices participating in the optimization control, Q s   min  is a lower limit vector of reactive powers of the dynamic reactive power compensation devices participating in the optimization control, Q s   max  is an upper limit vector of the reactive powers of the dynamic reactive power compensation devices participating in the optimization control, C s  is a sensitivity matrix of a reactive power adjustment vector of the dynamic reactive power compensation devices participating in the optimization control relative to ΔV s ′, C gs  is a sensitivity matrix of the reactive power adjustment vector of the generators participating in the optimization control relative to ΔV s ′, C sg  is a sensitivity matrix of the reactive power adjustment vector of the dynamic reactive power compensation devices participating in the optimization control relative to ΔV g ′, ΔV g   max  is a maximum adjustment vector allowed by the generators participating in the optimization control, ΔV s   max  is a maximum adjustment vector allowed by the dynamic reactive power compensation devices participating in the optimization control. 
         [0062]    In an embodiment, a i th  component in μ s  is calculated according to formula (5): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       μ 
                       si 
                     
                     = 
                     
                       
                         
                           Q 
                           si 
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                             
                               C 
                               
                                 s 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 j 
                               
                               ′ 
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                             
                               C 
                               
                                 sg 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 k 
                               
                               ′ 
                             
                           
                         
                         - 
                         
                           Q 
                           
                             s 
                             i 
                           
                           reference 
                         
                       
                       
                         
                           Q 
                           si 
                           max 
                         
                         - 
                         
                           Q 
                           si 
                           min 
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
         [0000]    and a i th  component in μ g  is calculated according to formula (6): 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       μ 
                       gi 
                     
                     = 
                     
                       
                         
                           Q 
                           gi 
                         
                         + 
                         
                           
                             ∑ 
                             
                               j 
                               = 
                               1 
                             
                             Ng 
                           
                            
                           
                             
                               C 
                               
                                 g 
                                 ij 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 g 
                                 j 
                               
                               ′ 
                             
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               k 
                               = 
                               1 
                             
                             Ns 
                           
                            
                           
                             
                               C 
                               
                                 gs 
                                 ik 
                               
                             
                              
                             Δ 
                              
                             
                                 
                             
                              
                             
                               V 
                               
                                 s 
                                 k 
                               
                               ′ 
                             
                           
                         
                         - 
                         
                           Q 
                           g 
                           aver 
                         
                       
                       
                         Q 
                         g 
                         sum 
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where μ si  is the component in μ s , μ gi  is the i th  component in μ g , N S  is a number of the dynamic reactive power compensation devices participating in the optimization control, N g  is a number of the generators participating in the optimization control, Q s     i    is a i th  component in Q s , C s     ij    is an element corresponding to a j th  generator participating in the optimization control of a i th  component in C s , ΔV s     j   ′ is a j th  component corresponding to the j th  generator participating in the optimization control in ΔV s ′, C sg     ik    is an element corresponding to a k th  dynamic reactive power compensation device participating in the optimization control of a i th  component in C sg , ΔV g     k   ′ is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the optimization control in ΔV g ′, Q s     i     reference  is a predetermined margin of the dynamic reactive power compensation device participating in the optimization control, Q s     i     min  is a i th  component in Q s   min , Q s     i     max  is a i th  component in Q s   max , Q g     i    is a i th  component in Q g , C g     ij    is an element corresponding to the j th  generator participating in the optimization control of a i th  component in C g , ΔV g     j   ′ is a j th  component corresponding to the j th  generator participating in the optimization control in ΔV g ′, C gs     ik    is an element corresponding to the k th  dynamic reactive power compensation device participating in the optimization control of a i th  component in C gs , ΔV s     k   ′ is a k th  component corresponding to the k th  dynamic reactive power compensation device participating in the optimization control in ΔV s ′, Q g   aver  is an average value of reactive power of the generator participating in the optimization control, Q g   sum  is a sum of reactive power of the generator participating in the optimization control. 
         [0063]    The second sending module  160  is configured to send the third voltage adjustment to the generator participating in the optimization control and the fourth voltage adjustment to the dynamic reactive power compensation device participating in the optimization control to perform a dynamic reactive power optimization. 
         [0064]    With the voltage control method and apparatus of a central bus in a power system provided by the present disclosure, a dynamic reactive power compensation device is used in a conventional voltage control model and a characteristic of fast adjustment of the dynamic reactive power compensation device is fully utilized, in addition, a dynamic reactive power optimization model is established and a reserve level of a reactive power in the power system may be improved by replacing the reactive power of the dynamic reactive power compensation device with the slow dynamic reactive power compensation device, further, an effective preventive control for transient voltage stability may be implemented by the method and a recovery effect after disturbances of voltages of the power system can be improved. 
         [0065]    A computer readable storage medium is provided, including a computer program for executing voltage control method and of a central bus in a power system according to the above embodiments of the present disclosure, when running on a computer. 
         [0066]    Reference throughout this specification to “an embodiment,” “some embodiments,” “one embodiment”, “another example,” “an example,” “a specific example,” or “some examples,” means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. Thus, the appearances of the phrases such as “in some embodiments,” “in one embodiment”, “in an embodiment”, “in another example,” “in an example,” “in a specific example,” or “in some examples,” in various places throughout this specification are not necessarily referring to the same embodiment or example of the present invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples. 
         [0067]    Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that the above embodiments cannot be construed to limit the present invention, and changes, alternatives, and modifications can be made in the embodiments without departing from spirit, principles and scope of the present invention.