Abstract:
A control system to realize input power changing along with both loads and rotate speed by an inverter bridge dragging many sets of motors, is composed of a stator voltage regulating unit ( 1 ), a motor unit ( 2 ), a rotor speed control unit ( 3 ), an inverter bridge unit ( 4 ), a control drive unit ( 5 ) and a signal processing unit ( 6 ). By setting a power factor sensor, the phase voltage and phase current of the motor stator are acquired as a control signal to regulate the input power so as to make it change with loads. At the same time, by setting a voltage sensor and a current sensor, motor rotor phase voltage, rectifier output current, overvoltage protection current and chopper working current are acquired separately as a control signal to regulate the input power so as to make it change with the rotate speed, thus realizing input power changing along with both loads and rotate speed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Phase Application of PCT International Application No. PCT/CN2012/000885, International Filing Date Jun. 28, 2012, claiming priority of Chinese Patent Application No. 201110231539.4, filed Aug. 11, 2011, which is hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a control system for driving multiple electric motors via one inverter bridge; and in particular, to a control system for realizing the change of input power with load and rotating speed simultaneously, by driving multiple electric motors via an inverter bridge. 
     BACKGROUND OF THE INVENTION 
     Nowadays, electrical energy is basically converted into mechanical energy via electric motors worldwide. An overseas survey shows that, in USA, Japan, France and Russia, the electrical energy consumed by electric motors accounts more than 60% of the overall industrial electrical energy consumption; and as investigated by related authorities, in the main electric grids in China, the electrical energy consumed by electric motors accounts 60%-68% of the overall industrial electrical energy consumption, which is approximately the same as that in developed countries. Therefore, countries all over the world are developing and popularizing various advanced technologies and devices so as to prompt the economical operation of electric motors. In China, remarkable effects and experiences have been obtained in the developing and adopting of various apparatuses and technologies that prompt the economical operation of electric motors. 
     With the development of electrical and electronic technologies, microelectronic technologies, control technologies and other technologies such as manufacturing processing, various speed-regulating apparatuses appear, among which, a frequency-changing type speed-regulating apparatus has the best performance and developing prospect. Particularly, with the application of vector-control technologies and direct torque control technologies, frequency-changing technologies become mature and take a leading position in AC driving due to its broad speed-regulating range, high speed-stabilization precision, rapid dynamic response and its performance of reversible operation in the four quadrants of a rectangular coordinate system. The speed-regulating performance of the frequency-changing technologies is comparable to DC driving. There is a trend that DC driving will be replaced by AC driving. 
     At present, globally well-known enterprises, including Siemens Electrical Drives Ltd. of Germany, Vaasa Control System Co., Ltd. of Finland, ABB of Switzerland, Schneider Electric Co. of France and Yaskawa of Japan, etc., are dominating the manufacturing of those commercialized large-scale electrical and electronic devices and frequency-changing devices. Products of the above industrially developed countries are also found in related application fields in China. In applying these products, however, one frequency inverter is employed for one electrical function, and one inverter bridge has to be provided for one frequency inverter. If an energy feedback function is required for the frequency-changing type speed-regulating system, another inverter bridge has to be added. Apparently, above configuration not only makes the system bulky and complex with poor stability, but also deteriorate the maintainability and performance-price ratio. 
     In view of above defects in prior art frequency-changing technologies, the inventor has conducted a large amount of experiments in cranes, oil pumping units used in oil fields, water injection pumps and steel ball machines, etc., on how to realize rotor frequency-changing type speed-regulating simultaneously by driving multiple electric motors asynchronously via an inverter bridge. In addition, a cabinet body and a tank body are designed and manufactured for AC and DC devices, thereby batch production and application are implemented, and a good effect is obtained. In this regard, three Chinese patents have been applied and authorized successively, with patent numbers ZL 200810094147.6, ZL 200810048732.2 and ZL 200810048252.2, respectively. 
     However, in an electric driving system, on one hand, there exists a power balance equation of electric motors:
 
 P 1=3 U 1 I 1 cos φ1
 
     Wherein
     P 1 —electric motor input power (KW);   U 1 —stator winding phase voltage (KV);   I 1 —stator winding phase current (A);   φ 1 —angle between the phase voltage and the phase current;   3 U 1  I 1  COS φ1—electric motor power factor.   

     On the other hand, for easy analysis, under the premise that no stator copper loss and iron loss of an electric motor and no rotor mechanical loss are considered:
 
 P 1= P 2+ PS  
 
     Here, P 2 —electric motor output power, i.e., load power; 
     PS—electric motor slip power, i.e., the power which is fed back to an electric grid or an electric motor by an inverter bridge after speed regulating of the electric motor. 
     Moreover, Ps=SP 1 ; 
     Therefore, 
     
       
         
           
             
               
                 
                   
                     P 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   = 
                     
                   ⁢ 
                   
                     
                       P 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       2 
                     
                     + 
                     Ps 
                   
                 
               
             
             
               
                 
                   = 
                     
                   ⁢ 
                   
                     
                       P 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       2 
                     
                     + 
                     
                       SP 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       1 
                     
                   
                 
               
             
           
         
       
     
     Or, 
     
       
         
           
             
               
                 
                   
                     P 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   = 
                     
                   ⁢ 
                   
                     
                       P 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       1 
                     
                     - 
                     
                       SP 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       1 
                     
                   
                 
               
             
             
               
                 
                   = 
                     
                   ⁢ 
                   
                     P 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                     ⁢ 
                     
                       ( 
                       
                         1 
                         - 
                         S 
                       
                       ) 
                     
                   
                 
               
             
           
         
       
     
     Based on that in an electric driving system, the slip ratio S of an electric motor is: 
     
       
         
           
             S 
             = 
             
               
                 
                   
                     N 
                     0 
                   
                   - 
                   N 
                 
                 
                   N 
                   0 
                 
               
               = 
               
                 1 
                 - 
                 
                   N 
                   
                     N 
                     0 
                   
                 
               
             
           
         
       
     
     Therefore, 
     
       
         
           
             
               
                 
                   
                     P 
                     2 
                   
                   = 
                     
                   ⁢ 
                   
                     
                       P 
                       1 
                     
                     ⁡ 
                     
                       ( 
                       
                         1 
                         - 
                         S 
                       
                       ) 
                     
                   
                 
               
             
             
               
                 
                   = 
                     
                   ⁢ 
                   
                     
                       P 
                       1 
                     
                     ⁡ 
                     
                       ( 
                       
                         1 
                         - 
                         
                           ( 
                           
                             1 
                             - 
                             
                               N 
                               
                                 N 
                                 0 
                               
                             
                           
                           ) 
                         
                       
                       ) 
                     
                   
                 
               
             
             
               
                 
                   = 
                     
                   ⁢ 
                   
                     
                       P 
                       1 
                     
                     ⁢ 
                     
                       N 
                       
                         N 
                         0 
                       
                     
                   
                 
               
             
           
         
       
     
     That is, 
     
       
         
           
             
               
                 
                   
                     P 
                     1 
                   
                   = 
                     
                   ⁢ 
                   
                     
                       
                         N 
                         0 
                       
                       N 
                     
                     ⁢ 
                     
                       P 
                       2 
                     
                   
                 
               
             
             
               
                 
                   = 
                     
                   ⁢ 
                   
                     
                       N 
                       0 
                     
                     ⁢ 
                     
                       
                         P 
                         2 
                       
                       N 
                     
                   
                 
               
             
           
         
       
     
     Wherein,
     No—rotor synchronous rotating speed of an electric motor;   N—rotor instant rotating speed of an electric motor.   

     The rotor synchronous rotating speed of an electric motor No is a constant, therefore, it is seen from the above equation that: electric motor output power P 1  relates simultaneously to electric motor output power P 2  (i.e., load) and electric motor rotor instant rotating speed N. 
     In conclusion, it is clear that: an electric driving system has three working states: in the first working state, the rotor rotating speed of the electric motor keeps constant, while the system load changes instantaneously; in the second working state, the system load keeps constant, while the rotor rotating speed of the electric motor changes instantaneously; and in the third working state, both the system load and the rotor rotating speed of the electric motor change instantaneously. 
     The prior art designs of an electric motor fail to satisfy the requirements of an electric driving system, in other words, an electric motor can not operate constantly in a high-efficiency region by these designs. Furthermore, during the practical operation of an electric driving system, technicians only contribute to an electric driving system of above discussed first or the second working state. Electrical driving systems of the first and the second working states have been discussed in  Practical Manual For Energy - Saving Reforming On An Electric Motor  (published by Shanghai Science Publishing House) and related patent documents. However, with the rapid development of science and technology and the urgent need of energy saving, an electrical driving and controlling system applicable for above discussed third working state is desired. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a solution in view of the situation in which both the system load and the rotor rotating speed of the electric motor change instantaneously, that is, to provide an electric driving control system under the above discussed “third working state”. This solution is a control system for realizing the change of input power with regard to both load and rotating speed. In other words, multiple electric motors are driven via one inverter bridge; on one hand, the input power changes with the instantaneous change of each load in the electric driving system; meanwhile, on the other hand, the input power changes with the instantaneous change of the rotating speed of each functional electric motor in the electric driving system. Moreover, each electric motor operates independently, and is synchronously coordinated and controlled in real time, without any interference. 
     Additionally, the invention also provides a function of energy feedback and recycling, that is, the AC current outputted by the inverter bridge is fed back to the electric grid or the electric motor in a manner of in-frequency and in-phase, so that the problem of “reverse power generation” of the electric motor may be solved, and the energy may be effectively saved. 
     To accomplish the above objects, the invention proposes the following technical solutions: 
     A control system for changing an input power according to both a load and a rotating speed, by driving multiple electric motors via one inverter bridge, the control system comprising: 
     a stator voltage-regulating unit  1 , an electric motor unit  2 , a rotor speed-regulating unit  3 , an inverter bridge unit  4 , a controlling and driving unit  5  and a signal processing unit  6 , wherein: 
     the stator voltage-regulating unit  1  comprises a plurality of stator voltage-regulating modules (i.e., the first stator voltage-regulating module  1 . 1  to the N th  stator voltage-regulating module  1 .N) for detecting a power factor as the input voltage control signal, and then adjusting the input power by controlling the input voltage so as to make the input power change with the change of the load. 
     The electric motor unit  2  comprises a plurality of electric motors (i.e., the first electric motor M 1  to the N th  electric motor MN) for accomplishing each work in the electric driving system asynchronously and simultaneously. 
     The rotor speed-regulating unit  3  comprises a plurality of rotor speed-regulating modules (i.e., the first rotor speed-regulating module  3 . 1  to the N th  rotor speed-regulating module  3 .N) for detecting the rotor voltage and the chopper current as the input voltage control signal, and then adjusting the input power by controlling the input voltage so as to make the input power change with the change of the rotating speed. 
     The inverter bridge unit  4  is used for rectifying the AC current signals having different frequencies, which are output from the rotor of each functional motor, into DC signals, then inverting the DC signals into AC current signals having the same frequency and phase as those of the electric grids, and then feeding the electrical energy of the inverted AC current signals back to the electric grids or the electric motor effectively. 
     The controlling and driving unit  5  comprises a plurality of controlling and driving modules (i.e., the first controlling and driving module  5 . 1  to the N th  controlling and driving module  5 .N) for receiving the digital signals from the signal processing unit  6 , performing digital processing and amplifying and driving, and controlling the stator voltage-regulating unit and the rotor speed-regulating unit, and realizing a real-time control for changing the input power according to both the load and the rotating speed. 
     The signal processing unit  6  comprises a plurality of signal processing modules (i.e., the first signal processing module  6 . 1  to the N th  signal processing module  6 .N) for receiving related signals detected by each sensor of the stator voltage-regulating unit and the rotor speed-regulating unit, performing signal processing and analog-digital conversion, sending digital signals to each corresponding controlling and driving unit, and performing real-time processing and controlling. 
     The technical solution of the invention is: on one hand, the real-time power factors of an electric motor (i.e., phase voltage and phase current of stator) are detected as the input voltage control signal of the whole system, and then, the input power is adjusted by controlling the input voltage control signal so as to make the input power change with the change of the load; at the same time, on the other hand, the rotor voltage of the electric motor, the rectifier output current, the overvoltage protection current and the working current of the chopper are detected as the input voltage control signal of the whole system, and then, the chopper is controlled by controlling the input voltage control signal, which is equivalent to adjusting the input power, so as to make it change with the change of the rotating speed. The detection of the above various signals are implemented by setting various sensors, and the corresponding change thereof is realized by microprocessors under the control of its master program. 
     The invention has the following beneficial effects: the invention designed based on the following consideration: software upgrading is more preferred than hardware upgrading, and at the same time, during developing, software debugging will not bring any physical damage to hardware. The invention employs a multi-microprocessor (CPU) operating system, develops a modularized circuit structure, an interface standard and signal processing technology. The invention implements a real-time control on the working state in which the input power changes according to both the load and the rotating speed, by a simply mechanical structure and hardware platform. Meanwhile, only one inverter bridge is used to guarantee that the slip power energy is effectively fed back to the electric grids or the electric motors. The invention has the characteristics of novel design, reasonable structure, reliable working, good maintainability, apparent energy-saving effect and broad application fields. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a functional block diagram of the circuit of the invention; 
         FIG. 2  is a circuit diagram showing the interconnection between the six units of the invention; 
         FIG. 3  is an amplified circuit diagram of the 1 st , the 2 nd  and the 3 rd  units of the invention; and 
         FIG. 4  is an amplified circuit diagram of the 4 th , the 5 th  and the 6 th  units of the invention. 
     
    
    
     LIST OF REFERENCE SYMBOLS 
     
         
           1  stator voltage-regulating unit 
           1 . 1  the first stator voltage-regulating module 
           1 .N the N th  stator voltage-regulating module 
         G 1 -GN power factor sensor group 
         KP 11 , KP 21 , KP 31 -KP 1 N, KP 2 N, KP 3 N stator voltage regulator group 
         C 11 , C 21 , C 31 , C 41 , C 51 , C 61 -C 1 N, C 2 N 1 , C 3 N, C 4 N, C 5 N, C 6 N capacitor group 
         R 11 , R 21 , R 31 -R 1 N, R 2 N, R 3 N resistor group 
         U           1  and UI 1  a phase voltage of any two phases in the three stators of the first electric motor M 1 , and a DC voltage converted from a phase current of any one phase in the three stators of the first electric motor M 1   
         U         N and UIN a phase voltage of any two phases in the three stators of the N th  electric motor MN, and a DC voltage converted from a phase current of any one phase in the three stators of the N th  electric motor MN 
           2  electric motor unit 
         M 1  the first electric motor 
         MN the N th  electric motor 
           3  rotor speed-regulating unit 
           3 . 1  the first rotor speed-regulating module 
           3 .N the N th  rotor speed-regulating module 
         Z 1 -ZN rectifier group 
         H 1 -HN hall voltage sensor group 
         H 21 , H 31 , H 41 -H 2 N, H 3 N, H 4 N hall current sensor group 
         IGBT 1 -IGBTN chopper group 
         UR 1 -URN overvoltage protector group 
         D 11 , D 21 , D 31  and D 11 , D 2 N, D 3 N isolator group 
         C 71 -C 7 N filtering capacitor group 
           4  inverter bridge unit 
         L 1  reactor 
         KP 4 , KP 5 , KP 6 , KP 7 , KP 8 , KP 9  silicon controlled rectifier 
         C 8 , C 9 , C 10 , C 11 , C 12 , C 13 , C 14 , C 15 , C 16 , C 16 , C 17 , C 18 , C 19  capacitor 
         R 4 , R 5 , R 6 , R 7 , R 8 , R 9  resistor 
         U 1  a phase voltage of any two phases in the three rotors of the first electric motor M 1   
         UN a phase voltage of any two phases in the three rotors of the N th  electric motor MN 
         UDI 1  and UDIN DC voltages converted from the output DC current of rectifier Z 1  and ZN, respectively 
         UDY 1  and UDYN DC voltages converted from the overcurrent that flows through protector UR 1  and URN, respectively 
         UTI 1  and UTIN DC voltages converted from the current that flows through the anode of chopper IGBT 1 -IGBTN, respectively 
           5  controlling and driving unit 
           5 . 1  the first controlling and driving module 
           5 .N the N th  controlling and driving module 
         U 51 -U 5 N triggering driver group 
           6  signal processing unit 
           6 . 1  the first signal processing module 
           6 .N the N th  signal processing module 
         U 11 -U 1 N signal processor group 
         U 21 -U 2 N analog-to-digital converter group 
         UM 1 -UMN on-line working voltage 
       
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring to  FIGS. 1-4 , the specific embodiments of the invention are shown. 
     As shown in  FIG. 1  and  FIG. 2 , the invention is consisted of a stator voltage-regulating unit  1 , an electric motor unit  2 , a rotor speed-regulating unit  3 , an inverter bridge unit  4 , a controlling and driving unit  5  and a signal processing unit  6 , wherein: 
     the stator voltage-regulating unit  1  includes a plurality of stator voltage-regulating modules, i.e., the first stator voltage-regulating module  1 . 1  to the N th  stator voltage-regulating module  1 .N; here, N represents an integer greater than 1. 
     As shown in  FIG. 3 , the first stator voltage-regulating module  1 . 1  is provided with a stator voltage regulator group KP 11 , KP 21 , KP 31 , a resistor group R 11 , R 21 , R 31 , and a capacitor group C 11 , C 21 , C 31 , C 41 , C 51  and C 61 ; these components are divided into three blocks: the first block includes KP 11 , R 11 , C 11 , C 21 , the second block includes KP 21 , R 21 , R 31 , R 41 , and the third block includes KP 31 , R 31 , R 41 , R 51 , R 61 . The input ends of these three block are connected with the three phases ABC of the electric grid power respectively, while the output ends thereof are connected with the three stators of the first electric motor M 1 . Moreover, a power factor sensor G 1  is provided on the three-phase power lines that connected with the three stators; 
     Similarly, as shown in  FIG. 3  the N th  stator voltage-regulating module  1 .N is provided with a stator voltage regulator group KP 1 N, KP 2  N, KP 3  N, a resistor group R 1 N, R 2  N, R 3  N, and a capacitor group C 1 N, C 2  N, C 3  N, C 4  N, C 5  N and C 6  N; these components are divided into three blocks: the first block includes KP 1  N, R 1  N, C 1  N, C 2  N, the second block includes KP 2  N, R 2  N, R 3  N, R 4  N, and the third block includes KP 3  N, R 3  N, R 4  N, R 5  N, R 6  N. The input ends of each block are connected with the three phases ABC of the electric grid power respectively, while the output ends thereof are connected with the three stators of the first electric motor M 1 . Moreover, a power factor sensor GN is provided on the three-phase power lines connected with the three stators. 
     As shown in  FIG. 3 , the electric motor unit  2  include a plurality of electric motors, i.e., the first electric motor M 1  to the N th  electric motor MN. The three stators of the first electric motor M 1  are connected respectively with the respective output end of the three stator voltage regulators KP 11 , KP 21  and KP 31  in the first stator voltage-regulating module  1 . 1 ; and the three rotors of the first electric motor M 1  are connected respectively with the three input ends of the rectifier Z 1  in the first speed-regulating module  3 . 1 . Similarly, the three stators of the N th  electric motor MN are connected respectively with the respective output end of the three stator voltage regulators KP 1 N, KP 2 N and KP 3 N in the N th  stator voltage-regulating module  1 .N, and the three rotors of the N th  electric motor MN are connected respectively with the three input ends of the rectifier ZN in the N th  speed-regulating module  3 .N. 
     As shown in  FIG. 3 , the rotor speed-regulating unit  3  includes a plurality of speed-regulating modules, i.e., the first rotor speed-regulating module  3 . 1  to the N th  rotor speed-regulating module  3 .N; 
     As shown in  FIG. 3 , the first rotor speed-regulating module  3 . 1  is provided with a rectifier Z 1 , a chopper IGBT 1 , an overvoltage protector UR 1 , an isolator group D 11 , D 21 , D 31  and a filtering capacitor C 71 . A hall voltage sensor H 11  is provided on the three input ends of the rectifier Z 1  and the three-phase power lines of the three rotors of the electric motor M 1 . A hall current sensor H 21  is provided between the cathode of the isolator D 11  and the anode Q 1  of the isolator D 21 . A hall current sensor H 31  is provided between the anode Q 1  of the isolator and the upper point S 1  of the overvoltage protector UR 1 . A hall current sensor H 41  is provided between the anode Q 1  of the isolator D 21  and the anode TC 1  of the chopper IGBT 1 . 
     Similarly, as shown in  FIG. 3 , the N th  rotor speed-regulating module  3 .N is provided with a rectifier Z N , a chopper IGBTN, an overvoltage protector URN, an isolator group D 1 N, D 2 N, D 3 N and a filtering capacitor C 7 N. A hall voltage sensor H 1 N is provided on the three input ends of the rectifier ZN and the three-phase power lines of the three rotors of the first electric motor MN. A hall current sensor H 2 N is provided between the cathode of the isolator DN and the anode QN of the isolator D 2 N. A hall current sensor H 3 N is provided between the anode QN of the isolator and the upper point SN of the overvoltage protector. A hall current sensor H 4 N is provided between the anode QN of the isolator D 2 N and the anode TCN of the chopper IGBTN. The rotor speed-regulating unit  3  is used for detecting the rotor voltage and the chopper current as input voltage control signals, and then adjusting the input power by controlling the input voltage so as to make the input power change with the change of the rotating speed. 
     As shown in  FIG. 4 , the inverter bridge unit  4  includes: a reactor L 1 ; silicon-controlled rectifier groups KP 4  and KP 7 , KP 5  and KP 8 , KP 6  and KP 9 ; resistor groups R 4  and R 7 , R 5  and R 8 , R 6  and R 9 ; and capacitor groups C 8 , C 9  and C 14 , C 15 ; C 10 , C 11  and C 16 , C 17 ; C 12 , C 13  and C 18 , C 19 ; wherein, the H point of the reactor L 1  is connected with the anodes of the silicon-controlled rectifier group KP 4 , KP 5 , KP 6 , while the connection points of the silicon controlled rectifier groups KP 4  and KP 7 , KP 5  and KP 8 , KP 6  and KP 9  are connected with the terminals A, B and C of a three-phase electric grid power, respectively. The inverter bridge unit  4  is used for rectifying the AC current signals having different frequencies, which are output from the rotors of each functional electric motor, into DC signals, and then, inverting the DC signals into AC current signals having the same frequency and phase as those of the electric grids, and feeding the electrical energy of the AC current signals back to the electric grid or the electric motors. 
     As shown in  FIG. 4 , the controlling and driving unit  5  comprises a plurality of controlling and driving modules, i.e., the first controlling and driving module  5 . 1  to the N th  controlling and driving module  5 .N. 
     The first controlling and driving module  5 . 1  is provided with a microprocessor U 31 , an amplifying driver U 41  and a triggering driver U 51 . The 10 th  pin and the 11 th  pin of the microprocessor U 31  are connected with the 15 th  pin and the 14 th  pin of the amplifying driver U 41 , respectively. The 3 rd  pin of the amplifying driver U 41  and the gate TG 1  of the chopper IGBT 1  in the first rotor speed-regulating module  3 . 1  are connected at a third point F. The 20 th  pin of the microprocessor is connected with the 11 th  pin of the triggering driver U 51 , and the 3 rd , 4 th , 5 th , 6 th , 7 th , 8 th  pins of the triggering driver U 51  are in turn connected directly with each point of AG 1 , AK 1 , BG 1 , BK 1 , CG 1 , CK 1  in the first stator voltage-regulating module  1 . 1 , respectively. 
     As shown in  FIG. 4 , the N th  controlling and driving module  5 .N is provided with a microprocessor U 3 N, an amplifying driver U 4 N and a triggering driver U 5 N. The 10 th  pin and 11 th  pin of the microprocessor U 3 N are connected with the 15 th  pin and the 14 th  pin of the amplifying driver U 4 N, respectively. The 3 rd  pin of the amplifying driver U 4 N and the gate TGN of the chopper IGBTN in the first rotor speed-regulating module  3 .N are connected at a fourth point G. The 20 th  pin of the microprocessor is connected with the 11 th  pin of the triggering driver U 5 N, and the 3 rd , 4 th , 5 th , 6 th , 7 th , 8 th  pins of the triggering driver U 5 N are in turn connected directly with each point of AGN, AKN, BGN, BKN, CGN, CKN in the first stator voltage-regulating module  1 .N, respectively. The controlling and driving unit  5  is used for receiving digital signals from the signal processing unit  6 , performing digital processing, amplifying and driving, performing real time controlling of stator voltage-regulating unit and the rotor speed-regulating unit, and realizing a real-time control for changing the input power according to both the load and the rotating speed. 
     As shown in  FIG. 4 , the signal processing unit  6  includes a plurality of signal processing modules, i.e., the first signal processing module  6 . 1  to the N th  signal processing module  6 .N. 
     The first signal processing module  6 . 1  is provided with a signal processor U 11  and an analog-to-digital converter U 21 , and the analog-to-digital converter U 21  is connected with the microprocessor U 31  of the first controlling and driving module  5 . 1 . 
     The N th  signal processing module  6 .N is provided with a signal processor UN and an analog-to-digital converter U 2 N, and the analog-to-digital converter U 2 N is connected with the microprocessor U 3 N of the first controlling and driving module  5 .N. 
     A phase voltage U 1  of any two phases in the three stators of the first electric motor M 1 , and a DC voltage UI 1  which is converted from a phase current of any one phase in the three stators of the first electric motor M 1 , are respectively provided to the 1 st  pin and the 2 nd  pin of the input end of the signal processor U 11  of the first signal processing module  6 . 1 . 
     A phase voltage UN of any two phases in the three stators of the first electric motor MN, and a DC voltage UIN which is converted from a phase current of any one phase in the three stators of the first electric motor MN, are respectively provided to the 1 st  pin and the 2 nd  pin of the input end of the signal processor U 1 N of the first signal processing module  6 .N. 
     A phase voltage U 1  of any two phases in the three stators of the first electric motor M 1  and a phase voltage UN of any two phases in the three stators of the N th  electric motor MN are provided to the 3 rd  pin of the input end of the signal processor U 11  in the first signal processing module  6 . 1  and the 3 rd  pin of the signal processor U 1 N in the N th  signal processing module  6 .N, respectively. 
     As shown in  FIG. 3  and  FIG. 4 , DC voltages UDI 1  and UDIN, which are respectively converted from the output DC current of the rectifier Z 1  in the first rotor speed-regulating module  3 . 1  and the output DC current of the rectifier ZN in the N th  rotor speed-regulating module  3 .N, are provided to the 4 th  pin of the input end of the signal processor U 11  in the first signal processing module  6 . 1  and the 4 th  pin of the input end of the signal processor U 1 N in the N th  signal processing module  6 .N, respectively. 
     As shown in  FIG. 3  and  FIG. 4 , DC voltages UDY 1  and UDYN, which are respectively converted from the current that flows through the overvoltage protector UR 1  in the first rotor speed-regulating module  3 . 1  and the current that flows through the overvoltage protector URN in the N th  rotor speed-regulating module  3 .N, are respectively provided to the 5 th  pin of the input end of the signal processor U 11  in the first signal processing module  6 . 1  and the 5 th  pin of the input end of the signal processor U 1 N in the N th  signal processing module  6 .N. 
     DC voltages UTI 1  and UTIN, which are respectively converted from the current flowing through the chopper IGBT 1  in the first rotor speed-regulating module  3 . 1  and the current flowing through the chopper IGBTN in the N th  rotor speed-regulating module  3 .N, are respectively provided to the 6 th  pin of the input end of the signal processor U 11  in the first signal processing module  6 . 1  and the 6 th  pin of the input end of the signal processor U 1 N in the N th  signal processing module  6 .N. 
     The cathode of the isolator D 31  in the first rotor speed-regulating module  3 . 1  and the cathode of the isolator D 3 N in the N th  rotor speed-regulating module  3 .N are connected at a first point D with the input end of the reactor L 1  in the inverter bridge unit  4 . 
     The cathode TE 1  of the chopper IGBT 1  in the first rotor speed-regulating module  3 . 1  and the cathode TEN of the chopper IGBTN in the N th  rotor speed-regulating module  3 .N are connected at a second point E with the respective cathodes of the silicon-controlled rectifier group KP 7 , KP 8 , KP 9  in the inverter bridge unit  4 , the first pin of the amplifying driver U 41  in the first controlling and driving module  5 . 1  and the first pin of the amplifying driver U 4 N in the N th  controlling and driving module  5 .N. 
     The model number, specification and function of the main devices in each unit of the invention are as follows: 
     G 1  to GN are power factor sensors, with a model number of WB9128, for detecting the phase voltage and phase current signal of the stators of an electric motor. 
     KP 11 -KP 31  or KP 1 N-KP 3 N is a stator voltage regulator group, with a model number of KP500 300A/1800V bi-directional silicon-controlled rectifier, for adjusting the stator voltage of an electric motor. 
     H 11  or H 1 N is a hall voltage sensor, with a model number of VSM025A, for detecting the rotor voltage, which representing the rotor rotating speed of the electric motor. 
     H 31  or H 3 N is a hall leakage current, with a model number of QDC21LTA, for detecting the DC bus overvoltage signal generated by the leakage current that flows through the piezoresistor of the overvoltage protector UR 1  or URN. 
     H 21 , H 41  or H 2 N, H 4 N are hall current sensors, with a model number of CSM300LT, for detecting the corresponding DC bus current and chopper current. 
     IGBT 1  or IGBT N  is a chopper, with a model number of GD300HFL120C2S, for adjusting the rotor current, i.e., the rotating speed of the electric motor. 
     KP 4 -KP 9  are silicon-controlled rectifiers, with a model number of KP500, 300/1800V, for building an inverter bridge which feeds the DC energy back to the electric grid or electric motors. 
     U 31  or U 3 N is a microprocessor, with a model number of ATMEGA64, for receiving a system state signal, performing data processing, issuing an instruction, and providing a system control signal. 
     U 41  or U 4 N is an amplifying drivers, with a model number of EX841, for receiving a microprocessor signal, generating a PWM signal required by the chopper, thereby adjusting the rotor rotating speed. 
     U 51  or U 5 N is a triggering driver, with a model number of LSJK-T3SCRH, for receiving a microprocessor instruction, generating a trigger signal required by the bidirectional silicon controlled rectifier of the stator voltage regulator, thereby adjusting the stator voltage. 
     U 11  or U 1 N is a signal processor, with a model number of LM258, for collecting signals detected by each sensor of the system and the on-line working main command voltage signal, processing the signals into the analog signals, and then converting the analog signals by an analog-to-digital converter into the digital signals that can be processed by the microprocessor. 
     The rest parts are all industrially interchangeable parts. 
     The above embodiments are only preferred embodiments of the invention, which are used for illustrating the technical characteristics and implementability of the invention, rather than limiting the patent scope of the invention. Meanwhile, one skilled in the art can understand and implement the above description. Therefore, all equivalent variations or modifications without departing from the disclosure of the invention fall into the scope of the claims of the invention.