Abstract:
A method and a device are described for determining an angular velocity of the rotor of a polyphase machine operated by field orientation without a transmitter, wherein control signals, a stator current model space vector and a conjugated complex reference space vector are calculated by a signal processor containing, among other things, a complete machine model and a modulator, as a function of a flux setpoint, a torque setpoint, a d.c. voltage value, measured power converter output voltage values and system parameters, with a real stator current space vector which is measured and the calculated stator current model space vector are being multiplied by the calculated conjugated complex reference space vector, and the imaginary components of the results being compared with one another, and the system deviation determined therefrom being used to adjust the angular velocity of the rotor as a system parameter in such a way that the system deviation thus determined becomes zero. In this method, the stator current model space vector and the real stator current space vector are each processed in angular position and modulus as a function of the operating point before these processed space vectors are transformed into the complex reference system. Thus, the operational dependence of the relationship between the rotational speed difference and the system is greatly reduced.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method of determining the angular velocity of a polyphase machine operated by field orientation without a transmitter and a device for carrying out this method. 
     BACKGROUND INFORMATION 
     German Patent Application No. 195 31 771.8 describes a method and a device for determining an angular velocity of a polyphase machine operated by field orientation without a transmitter. 
     The present invention is based on the finding that under steady-state operating conditions, there is a difference 
     
       
         Δω/ω * ={circumflex over (ω)}/ω * −ω/ω * {circumflex over (=)}Δ n={circumflex over (n)}−n   (1) 
       
     
     between a normalized rotational speed {circumflex over (n)} of the model of the machine and a normalized speed n of the polyphase machine. 
     According to German Patent Application No. 195 31 771.8, in steady-state operation, the following formal relationship exists between normalized rotational speed difference Δñ and system deviation {tilde over (Δ)}⊥ at the input of the equalizing controller according to the older German patent application:                  Δ   ⊥     ~     =             u   ¨     ^     ·     (       -   Δ          n   ~       )                     with                     u   ¨     ^       =     f        (         n   ^     s     ,       n   ^     r     ,     σ   ^     ,     ρ   ^     ,         T   ^     →     *       )                 (   2   )                                
     where 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 
                   
                     
                       
                         
                           n 
                           ^ 
                         
                         r 
                       
                     
                             
                     
                         
                     
                   
                 
                 is the model rotor frequency 
               
               
                   
               
               
                 
                   
                     
                       
                         
                           n 
                           ^ 
                         
                         s 
                       
                     
                             
                     
                         
                     
                   
                 
                 is the model stator frequency 
               
               
                   
               
               
                 
                   
                     
                       
                         
                           σ 
                           ^ 
                         
                         = 
                         
                           
                             
                               L 
                               ^ 
                             
                             σ 
                           
                           / 
                           
                             ( 
                             
                               
                                 
                                   L 
                                   ^ 
                                 
                                 μ 
                               
                               + 
                               
                                 
                                   L 
                                   ^ 
                                 
                                 σ 
                               
                             
                             ) 
                           
                         
                       
                     
                             
                     
                         
                     
                   
                 
                 is the leakage factor of the polyphase machine 
               
               
                   
               
               
                 
                   
                     
                       
                         
                           
                             ρ 
                             ^ 
                           
                           = 
                           
                             
                               
                                 
                                   T 
                                   ^ 
                                 
                                 r 
                               
                               / 
                               
                                 
                                   T 
                                   ^ 
                                 
                                 s 
                               
                             
                             = 
                             
                               
                                 ( 
                                 
                                   
                                     
                                       L 
                                       ^ 
                                     
                                     μ 
                                   
                                   + 
                                   
                                     
                                       L 
                                       ^ 
                                     
                                     σ 
                                   
                                 
                                 ) 
                               
                                
                               
                                   
                               
                               · 
                               
                                   
                               
                                
                               
                                 
                                   
                                     R 
                                     ^ 
                                   
                                   s 
                                 
                                 / 
                                 
                                   ( 
                                   
                                     
                                       
                                         R 
                                         ^ 
                                       
                                       r 
                                     
                                      
                                     
                                         
                                     
                                     · 
                                     
                                         
                                     
                                      
                                     
                                       
                                         L 
                                         ^ 
                                       
                                       μ 
                                     
                                   
                                   ) 
                                 
                               
                             
                           
                         
                          
                         
                             
                         
                       
                     
                             
                     
                         
                     
                   
                 
                 is the time constant ratio 
               
               
                   
               
               
                 
                   
                     
                       
                         
                           T 
                           ^ 
                         
                         → 
                       
                     
                             
                     
                         
                     
                   
                 
                 is the selected reference space vector 
               
               
                   
               
             
          
         
       
     
     The “˜” symbols above notations in the equation indicate that only steady-state operating states are taken into account. 
     According to equation 2, the magnitude of steady-state transfer factor {umlaut over ({tilde over (u)})} in general changes considerably as a function of stator frequency {circumflex over (n)} s  and rotor frequency {circumflex over (n)} r  as operating parameters, which characterize a steady-state operating point of the polyphase machine. FIG. 3 illustrates this relationship for the case when normalized rotor flux space vector {circumflex over (ψ)} r  is selected as reference space vector          T   ^     →                          
     for splitting the stator current model space vector and the stator current real space vector. Stator frequency {circumflex over (n)} s  and rotor frequency {circumflex over (n)} r  as operating parameters are linked together via normalized rotational speed n according to the following equation: 
     
       
         
           ñ 
           s 
           =ñ+ñ 
           r 
         
       
     
     Normalization to rotor break-down circular frequency ω rK =R r /L 94   and the symbol “−” for characterization of steady-state operation are described in the article “Schnelle Drehmomentregelung im gesamten Drehzahlbereich eines hochausgenutzten Drehfeldantriebs” (Fast torque control in the entire rpm range of a highly utilized rotational field drives), printed in the German journal  Archiv für Elektrotechnik  (Archive for Electrical Engineering), 1994, volume 77, pages 289 through 301. 
     SUMMARY 
     An object of the present invention is to improve upon the conventional method and device in such a way as to greatly reduce the interfering dependence of the steady-state transfer factor on the rotor frequency as an operating parameter. 
     Due to the fact that the conjugated complex normalized rotor flux space vector divided by the square of its modulus is provided as the conjugated complex reference space vector, and the stator current model space vector and the stator current real space vector are each processed in regard to angular position and modulus as a function of the operating point before these processed space vectors are transformed into the complex reference system, this achieves the result that the interfering dependence of the steady-state transfer factor on the rotor frequency as an operating parameter is greatly reduced. 
     In an advantageous method, the model and real stator current space vectors are each normalized, and a differential current space vector is formed from these normalized space vectors, and then is processed as explained above and transformed. This greatly reduces the dependence of the steady-state transfer factor on rotor frequency as an operating parameter and greatly reduces the complexity. 
     These two methods can be optimized by calculating a complex factor which depends on the rotor frequency as an operating parameter and a leakage factor and/or a time constant ratio as a system parameter. 
     In another advantageous method, a time integral value of the differential current space vector is formed and is then processed and added to the processed differential current space vector. This achieves the result that the steady-state transfer factor has a constant value of one. Thus, this steady-state transfer factor no longer depends on rotor frequency as an operating parameter and the leakage factor and/or the time constant ratio as a system parameter. 
     By varying the calculation of the complex factors for processing the differential current space vector and its time integral value, this method can be improved with regard to its dynamic response without altering the steady-state transfer factor. 
     In another advantageous method, a time derivation of the differential current space vector is formed, and the sum of the processed differential current integral space vector and the processed differential current space vector is added up, and then the sum space vector thus formed is transformed. This further improves the response characteristic in the dynamic operating state. 
     In one example embodiment of the present invention, a device for calculating complex factors for processing the stator current model space vector, the stator current real space vector, a differential current space vector and a differential current integral space vector is connected downstream from the signal processor, with several multipliers being provided, connected to this device at the input end and at the other end to the elements at whose outputs the signals to be processed are available. 
     In comparison with the conventional device, an advantageous device additionally has only the device for calculating the complex factors, a comparator device and two additional multipliers. These additional elements may be integrated into the signal processor in an especially advantageous device. In other words, the difference between the device according to the present invention and the conventional device lies in the software rather than the hardware. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a block diagram of a first embodiment of the device for carrying out the method according to the present invention. 
     FIG. 2 shows a block diagram of a second embodiment of the device for carrying out the method according to the present invention. 
     FIG. 3 shows a diagram illustrating the steady-state transfer factor plotted over the stator frequency as a function of the rotor frequency without the use of the method according to the present invention. 
     FIG. 4 shows a diagram illustrating the steady-state transfer factor plotted over the stator frequency as a function of the rotor frequency when using the method according to the present invention. 
     FIG. 5 shows a block diagram of another example embodiment of the present invention. 
     FIG. 6 shows a block diagram of yet another example embodiment of the present invention. 
     FIG. 7 shows a block diagram of a further example embodiment of the present invention. 
     FIG. 8 shows a block diagram of yet another example embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a block diagram of a first embodiment of the device for carrying out the method according to the present invention. Portions of this device are described in German Patent Application No. 195 31 771.8. This conventional portion includes polyphase machine DM which receives power from a pulse power converter SR. A d.c. voltage 2E d , also referred to as an d.c. link voltage, is applied at the input end of pulse power converter SR. Pulse power converter SR receives control signals S a , S b , S c  from a signal processor  2 . In addition, the conventional portion of this device includes measuring elements  4 ,  6 ,  26 , lag elements  10 ,  12 ,  14 ,  16 ,  28 , a coordinate converter  8 , a first and a second multiplier  18 ,  20 , two comparators  24 ,  30 , two equalizing controllers  22 ,  32  and a multiplier  34 . Signal processor  2 , which also includes a complete machine model and a modulator, is linked at the output end to pulse power converter SR by way of lag element  10 , to an input of first multiplier  18  by way of a lag element  14 , and to another input of the first and second multipliers  18 ,  20  by way of lag element  16 . Coordinate converter  8  is connected at the input to measuring element  6  via lag element  12  and at the output to another input of second multiplier  20 . At the input, signal processor  2  is connected directly to measuring element  4  and it is connected to measuring element  26  by way of lag element  28 . In addition, signal processor  2  is connected at the input to equalizing controllers  22 ,  32 , with equalizing controller  22  being connected directly to the output of comparator  24  and equalizing controller  32  being connected to the output of comparator  30  by way of multiplier  34 . Furthermore, two setpoints ŜM and ŜF are supplied to signal processor  2 . The outputs of these two multipliers  18 ,  20  at which imaginary components WG,{circumflex over (WG)} are available are connected to the inputs of comparator  24 , and the outputs of these two multipliers  18 ,  20 , where real components BG,{circumflex over (BG)} are available, are connected to the inputs of comparator  30 . System deviation Δ⊥ is available at the output of comparator  24  for adaptation of rotor angular velocity {circumflex over (ω)} as a system parameter, and system deviation Δ∥ is available at the output of comparator  30  for adaptation of stator resistance {circumflex over (R)} s  as a system parameter. 
     German Patent Application 195 31 771.8 discussed above describes the mode of operation of this conventional device in detail, so that no description is necessary here. 
     According to the present invention, this conventional device is expanded, as described below. 
     In an example embodiment of the present invention, the first and second multipliers  18 ,  20  are subdivided into partial multipliers  18   1 ,  18   2 ,  20   1 ,  20   2 , one output of partial multipliers  18   1 ,  20   1 , being connected to the inputs of comparator  24  and one output of partial multipliers  18   2 ,  20   2  being connected to the inputs of comparator  30 . Two additional multipliers  36 ,  38 , subdivided into partial multipliers  36   1 ,  36   2  and  38   1 ,  38   2 , are arranged between these first and second multipliers  18   1 ,  18   1 ,  20   1 ,  20   2  and lag element  14  on the one hand, and coordinate converter  8 , on the other. The outputs of partial multipliers  36   1 ,  36   2  and  38   1 ,  38   2  are each connected to one input of partial multipliers  18   1 ,  18   2  and  20   1 ,  20   2 . The additional inputs of these partial multipliers  18   1 ,  18   2 ,  20   1 ,  20   2  are each connected to the output of lag element  16  at whose input conjugated complex reference space vector            T   ^     *     →                          
     is applied. The first inputs of partial multipliers  36   1 ,  36   2  and  38   1 ,  38   2  are each connected to lag element  14  and coordinate converter  8 , whereas the second inputs of these partial multipliers  36   1 ,  38   1  and  36   2 ,  38   2  are connected via a lag element  40  or  42  to a device  44  for calculating complex factors  K   ω ,  K   R . A processed stator current model space vector            K   ω     ·         i   ^     s     →       ,       K   R     ·         i   ^     s     →                              
     and a processed stator current real space vector            K   ω     ·       i   s     →       ,       K   R     ·       i   s     →                              
     are available at the outputs of partial multipliers  36   1 ,  36   2  and  38   1 ,  38   2  and are then transformed by conjugated complex reference space vector            T   ^     *     →                          
     and partial multipliers  18   1 ,  18   2 ,  20   1 ,  20   2  into the complex reference system. The angular position and modulus of stator current model space vector            i   ^     s     →                          
     and stator current real space vector          i   s     →                          
     are changed by multiplication by complex factors  K   ω ,  K   R  as a function of operating point. 
     In the following embodiments according to FIGS. 2 and 5 through  8 , normalized variables are used. These variables are obtained by dividing by a corresponding reference quantity. The following reference quantities are used: 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 Ψ *   
                 Reference quantity for flux variables, defined 
               
               
                   
                 as the modulus of the sapce vector of the 
               
               
                   
                 stator flux linkage in operation at 
               
               
                   
                 nominal flux 
               
               
                 I *  = Ψ * /L σ   
                 Reference quantity for currents 
               
               
                 ω *  = ω σ = R r /L σ   
                 Reference quantity for circular 
               
               
                   
                 frequencies and angular velocities 
               
               
                   
               
               
                 
                   
                     
                       
                         
                           T 
                           * 
                         
                         = 
                         
                           
                             T 
                             σ 
                           
                           = 
                           
                             
                               
                                 L 
                                 σ 
                               
                               / 
                               
                                 R 
                                 r 
                               
                             
                             = 
                             
                               1 
                               
                                 ω 
                                 rK 
                               
                             
                           
                         
                       
                     
                             
                     
                         
                     
                   
                 
                 Reference quantity for time 
               
               
                   
               
             
          
         
       
     
     These reference quantities are characterized by the index * with the respective symbol. The following symbols and letters have been chosen for normalized variables: 
     Ψ/Ψ * =ψ 
     i/I * =y 
     ω/ω * =n 
     t/T * =τ 
     FIG. 2 shows a second embodiment of the device for carrying out the method according to the present invention. This second embodiment is especially advantageous, because it is less complicated and less expensive than the first embodiment according to FIG.  1 . In this second embodiment, the output of coordinate converter  8  and the output of lag element  14  are connected to the inputs of a comparator device  46 , whose output is connected to one input each of multipliers  36 ,  38 . From the pending normalized stator current model space vector            y   ^     s     →                          
     and the normalized stator current real space vector            y   s     →     ,                          
     this comparator device  46  forms a normalized differential current space vector        Δ                     y   s     →                            
     which is processed further. 
     This space vector        Δ                     y   s     →                            
     of the differences between the model currents and the machine currents is determined by taking into account the shift in time between the measured values and the previously calculated model values in the v th  calculation cycle according to the following equation:                Δ                       y   s     →          (   v   )         =             y   ^     s     →          (     v   -       T   ∑     /     T   C         )       -       y   s                       (   v   )     →                 (   3   )                                
     The resulting time shift T Σ  is taken into account by lag element  14  in FIG.  2 . 
     In comparison with the embodiment according to FIG. 1, multipliers  18 ,  20 ,  36 ,  38  are not subdivided into two partial multipliers here. The second input of multiplier  36  is connected to the output of lag element  40  whose input receives complex factor  K   ω . The second input of multiplier  38  is connected to the output of lag element  42  whose input receives complex factor  K   R . A processed, normalized differential current space vector        Δ                     y   sω     →                   and                 Δ                     y   sR     →                            
     is available at the output of multiplier  36  and  38 , respectively, and is transformed to the complex reference system by conjugated complex reference space vector            T   ^     *     →                          
     and multiplier  18  or  20 . 
     The imaginary component of the product formed by multiplier  18  is sent as system deviation Δ⊥ to equalizing controller  22  for adaptation of normalized rotational speed {circumflex over (n)}, with the real component of the product formed by multiplier  20  being sent as a system deviation Δ∥ to equalizing controller  32  by way of multiplier  34  for adaptation of stator resistance {circumflex over (r)} s . Instead of the sign of the stator power, the sign ‘sign ({circumflex over (n)} r ·{circumflex over (n)} s )’ of the product of model rotor frequency {circumflex over (n)} r  and stator frequency {circumflex over (n)} s  is sent from signal processor  2  to multiplier  34 . 
     FIG. 3 shows a diagram of steady-state transfer factor {umlaut over ({tilde over (u)})} plotted over stator frequency ñ s  as a function of rotor frequency ñ r . This diagram is obtained if normalized conjugated complex rotor flux space vector          ψ     -&gt;   r       *                          
     is selected as when conjugated 
     as conjugated complex reference space vector            T   ^     *     →                          
     in the second embodiment according to FIG. 2, and a constant value of one is assumed for complex factor  K ω for processing differential current space vector        Δ                       y   s     →     .                            
     As this diagram shows, steady-state transfer factor {umlaut over ({tilde over (u)})} in motor operation and generator operation depends to a great extent on rotor frequency ñ r  as an operating parameter, and this transfer factor {umlaut over ({tilde over (u)})} changes signs in generator operation at a low stator frequency ñ s  Rotor frequency ñ r  and stator frequency ñ s  are operating parameters calculated according to the equations: 
       ñ   r ={tilde over (ω)} r ·{circumflex over (σ)}· {circumflex over (T)}   r   (4) 
     
       
           {circumflex over (n)}   s ={tilde over (ω)} s ·{circumflex over (σ)}· {circumflex over (T)}   r   (5) 
       
     
     FIG. 4 shows a diagram of steady-state transfer factor {umlaut over ({tilde over (u)})} plotted over stator frequency ñ s  as a function of rotor frequency ñ r . This diagram is obtained when complex factor  K ω according to the equation: 
     
       
             K     ω =1 +j·{circumflex over (n)}   r   (6) 
       
     
     is selected by device  44  for calculating complex factors  K   ω ,  K   R  and conjugated complex reference space vector            T   ^     *     →                          
     according to the following equation:                    T   ^     *     →     =           Ψ   ^     r   *     →     /                Ψ   ^     r     →          2               (   7   )                                
     is selected. 
     Thus, system deviation Δ⊥ for adaptation of normalized rotational speed {circumflex over (n)} of the complete machine model of signal processor  2  according to the embodiment of the device as in FIG. 2 is formed according to the equation:                Δ   ⊥     =     Im        {         Δ                   y   s       -&gt;     ·     (     1   +     j   ·       n   ^     r         )     ·           Ψ   ^       -&gt;   r       *     /              Ψ   ^       -&gt;   r            2         }               (   8   )                                
     Due to the processing of differential current space vector          Δ                   y   s       -&gt;                          
     using complex factor  K   ω  according to equation (6), the dependence of steady-state transfer factor {umlaut over ({tilde over (u)})} on rotor frequency ñ r  as an operating parameter is greatly reduced, as shown by the diagram according to FIG.  4 . However, this diagram shows that this steady-state transfer factor {umlaut over ({tilde over (u)})} still changes signs in generator operation at a low stator frequency ñ s . 
     At such operating points, rotational speed difference Δn cannot be regulated to zero in a stable manner using a simple PI controller in the form of an equalizing controller  22 . To overcome this disadvantage, in another example of the method in the operating range in question, complex factor  K   ω  is calculated in device  44  according to the following equation: 
     
       
             K     ω =1 +j·{circumflex over (n)}   r /{circumflex over (σ)}  (9) 
       
     
     System deviation Δ⊥ is then determined according to the following equation:                Δ   ⊥     =     Im        {         Δ                   y   s       -&gt;     ·     (     1   +     j   ·         n   ^     r     /     σ   ^           )     ·           Ψ   ^       -&gt;   r       *     /              Ψ   ^       -&gt;   r            2         }               (   10   )                                
     Steady-state transfer factor {umlaut over ({tilde over (u)})} then always has a positive sign for any desired combination of operating parameters ñ s  and ñ r , although the characteristic curves in FIG. 4 are tangents to the zero line at ñ s =0, i.e., system deviation Δ⊥ has a very low sensitivity in reacting to a rotational speed difference Δn. In another example of this method, this disadvantage can be overcome if complex factor  K ω is determined in device  44  according to the following equation: 
     
       
             K     ω =1 +j·{circumflex over (n)}   r ·(2/{circumflex over (σ)}− 1 )  (11) 
       
     
     System deviation Δ⊥ is then obtained according to the following equation:                Δ   ⊥     =     Im        {         Δ                   y   s       -&gt;     ·     [     1   +     j   ·       n   ^     r     ·     (       2   /     σ   ^       -   1     )         ]     ·           Ψ   ^       -&gt;   r       *     /              Ψ   ^       -&gt;   r            2         }               (   12   )                                
     However, in motor operation at a low stator frequency, this variant yields negative values for steady-state transfer factor {umlaut over ({tilde over (u)})}. For this reason, complex factor  K ω is always calculated according to equation (6) in device  44  in motor operation, i.e., when the product of stator frequency ñ s  and rotor frequency ñ r  as operating parameters is positive. The same thing is true if the sign of the product of stator frequency {circumflex over (n)} s  and rotor frequency {circumflex over (n)} r  as operating parameters is negative, but the absolute value of stator frequency {circumflex over (n)} s  as an operating parameter is above a limit |{circumflex over (n)} sE |. On the whole, these instructions for using equation (6) can be implemented by binary logic processing of the following relationship: 
     
       
           {circumflex over (n)}   s   ·{circumflex over (n)}   r &gt;0 
       
     
     or 
     
       
         | {circumflex over (n)}   s   |&gt;|{circumflex over (n)}   sE | 
       
     
     where 
     
       
           {circumflex over (n)}   sE   =−V·{circumflex over (ρ)}·{circumflex over (n)}   r   (13) 
       
     
     where V&gt;1, e.g., V=1.3. 
     Complex factor  K ω is calculated according to equation (9) or (11) by using device  44  in conjunction with signal processor  2  only in the operating range with the following characterization: 
     
       
           {circumflex over (n)}   s   ·{circumflex over (n)}   r &lt;0 and 0&lt;| {circumflex over (n)}   s   |&lt;|{circumflex over (n)}   sA | 
       
     
     where                  n   ^     sA     =       1     Q   ·   V       ·       1   -     σ   ^         1   +       n   ^     r   2         ·       n   ^     sE               (   14   )                                
     where Q&gt;1, e.g., Q=2 when complex factor  K   ω  is calculated according to equation (9), and Q=4 when this complex factor  K   ω  is calculated according to equation (11). 
     In the remaining range with values of {circumflex over (n)} s  between {circumflex over (n)} sE  and {circumflex over (n)} sA , which is also referred to as the cross-fade range, a soft cross-fade is performed from equation (6) to equation (9) or to equation (11) to calculate factor  K ω. To do so, an auxiliary variable X 2  which is always positive is used; it is determined according to the following equation:                X   2     =         (         n   ^     sE     -       n   ^     s       )     2         (         n   ^     sE     -       n   ^     sA       )     2               (   15   )                                
     in device  44  in combination with signal processor  2 . 
     In this cross-fade range, complex factor  K   ω  is then determined in device  44  according to the following instructions. In cross-fade between equation (6) and equation (9), the instruction is: 
     
       
             K ω =1+ j·{circumflex over (n)}   r ·[1+ x   2 ·( 1−{circumflex over (σ)})/{circumflex over (σ)}]   (16) 
       
     
     and in cross-fade between equation (6) and equation (11), the instruction for calculating complex factor  K   ω  is then: 
     
       
             K ω =1+ j·{circumflex over (n)}   r ·[1+ x   2 ·2·( 1−{circumflex over (σ)})/{circumflex over (σ)}]   (17) 
       
     
     FIG. 5 shows a block diagram of another embodiment of the device for carrying out the method according to the present invention, with this embodiment based on the embodiment according to FIG.  2 . This embodiment of the device differs from the embodiment of the device according to FIG. 2 in that the output of comparator device  46  is connected to an input of an integrator  48 , which is connected at its output to an adder  52  by way of an additional multiplier  50 . A second input of the additional multiplier  50  is connected to one output of an additional lag element  54 , which is connected at its input to device  44 . The second input of adder  52  is connected to the output of multiplier  36 , with this adder  52  being connected at the output to an input of first multiplier  18 . A complex factor  K   I  is available at the input of second lag element  54 ; time integral value            Δ                   y     s                 τ         -&gt;     ,                          
     which is also known as differential current integral space vector            Δ                   y     s                 τ         -&gt;     ,                          
     of differential current space vector          Δ                   y   s       -&gt;                          
     is processed with the help of this complex factor. This processed differential current integral space vector          Δ                   y     s                 τ                 I         -&gt;                          
     is then added to the processed differential current space vector          Δ                   y     s                 ω         -&gt;                          
     by adder  52 . Like complex factor  K   ω , complex factor  K   I  is determined anew by device  44  in each calculation cycle. The time shift of calculated variables and those determined by measurement is taken into account by lag element  54 . Sum space vector          Δ                   y     s                 ω                 I         -&gt;                          
     available at the output of adder  52  is multiplied by conjugated complex reference space vector            T   ^     -&gt;     *                          
     in first multiplier  18 . The imaginary component of this product supplies system deviation Δ⊥. Conjugated complex reference space vector            T   ^     -&gt;     *                          
     is formed unchanged according to equation (7) in signal processor  2 , whereas complex factor  K   ω  is calculated in device  44  according to equation (6) in combination with signal processor  2 . The following equation holds for determination of additional complex factor  K   I : 
         K     I ={circumflex over (ρ)}·({circumflex over (σ)}= j·{circumflex over (n)}   r )  (18) 
     System deviation Δ⊥ is thus obtained from the following rule:                  Δ   ⊥     =     Im        {       (         Δ                   y     s                 ω         -&gt;     +       Δ                   y     s                 τ                 I         -&gt;       )     ·           Ψ   ^       -&gt;   r       *     /              Ψ   ^       -&gt;   r            2         }                       where                       Δ                   y     s                 ω         -&gt;     =         K   _     ω     ·       Δ                   y   s       -&gt;                             Δ                   y     s                 τ                 I         -&gt;     =         K   _     I     ·     ∫         Δ                   y   s       -&gt;     ·        τ                     (   19   )                                
     When system deviation Δ⊥ is determined according to equation (19), then steady-state transfer factor {umlaut over ({tilde over (u)})} has a constant value of one, i.e., it no longer depends on the operating parameters or system parameters. However, in dynamic transitions between steady-state operating points, there is still some dependence of transfer factor ü on these parameters. 
     If, according to another variant of the method, these two complex factors  K   ω  and  K   I  are calculated according to the two following equations: 
     
       
             K ω ={circumflex over (ρ)}+1 +j·{circumflex over (n)}   r   (20) 
       
     
     and 
         K     I ={circumflex over (ρ)}·({circumflex over (σ)}− j·{circumflex over (n)})   (21) 
     where 
     
       
         
           {circumflex over (n)}={circumflex over (ω)}/ω* 
         
       
     
     this yields an improvement in the dynamic response without any change in steady-state transfer factor {umlaut over ({tilde over (u)})}. 
     A further improvement in transfer response in dynamic operating states is achieved by also taking into account the time derivative of differential current space vector          Δ                   y   s       -&gt;                          
     in sum space vector            Δ                   y     s                 ω                 I         -&gt;     .                          
     To do so, the output of comparator device  46  is also connected to a differentiator  56 , which is connected at the output to another input of adder  52 . Time derivative          Δ                   y     s                 D         -&gt;                          
     of differential current space vector          Δ                   y   s       -&gt;                          
     is then available at the output of this differentiator  56  and it is added to sum space vector            Δ                   y     s                 ω                 I         -&gt;     .                          
     In this variant, complex factors  K   ω  and  K   I  are determined in device  44  in combination with signal processor  2  according to the two following equations: 
     
       
             K     ω ={circumflex over (ρ)}+1 −j·{circumflex over (n)}   (22) 
       
     
     and 
     
       
             K     I ={circumflex over (ρ)}·({circumflex over (σ)}− j·{circumflex over (n)} )  (21) 
       
     
     In comparison with the previous variant, only the rule for determination of complex factor  K   ω  changes. The equation for determining system deviation Δ⊥ is thus:                      Δ   ⊥     =                Im        {     [                    Δ                   y   s       -&gt;       /        τ                Δ                   y   sO       -&gt;       +             Δ                   y   s       -&gt;     ·     (       ρ   ^     +   1   -     j   ·     n   ^         )                Δ                   y     s                 ω         -&gt;       +                                              (     ∫         Δ                   y   s       -&gt;     ·        τ         )     ·     ρ   ^     ·     (       σ   ^     -     j   ·     n   ^         )                Δ                   y     s                 τ                 I         -&gt;       ]     ·           Ψ   ^       -&gt;   r       *     /              Ψ   ^       -&gt;   r            2         }                 (   23   )                                
     In practice, variable               ψ   r     -&gt;                               
     normally changes so slowly that its time derivative can be disregarded without any significant error. Then equation (23) yields value Δn continuously, not only under steady-state operating conditions, and it holds that: 
     
       
         Δ⊥=−Δn {right arrow over (u)}=1 {right arrow over (u)}≠f ( {circumflex over (n)}   s   ,{circumflex over (n)}   r   ,{circumflex over (σ)},{circumflex over (ρ)}, t)   (24) 
       
     
     Under steady-state operating conditions, differential current space vector          Δ                   y   s       -&gt;                          
     rotates at angular velocity {circumflex over (ω)} s  which can reach very high values, e.g., 200·2π to 300·2π Hz. The orthogonal coordinates of time derivative          Δ                   y     s                 D         -&gt;                          
     of differential current space vector          Δ                   y   s       -&gt;                          
     which are formed by differentiator  56  according to FIG. 5 are periodic quantities with angular frequency {circumflex over (ω)} s . Then, it is difficult to adequately filter out the interfering signals which are superimposed on the useful signal and originate from the measurement chain for determination of the normalized stator current real space vector            y   s     -&gt;     .                          
     This disadvantage can be reduced significantly by another embodiment of the device according to FIG.  6 . To achieve this, three new quantities, which are formed by the following equations, are also needed:                [     ∫       u   -&gt;     ·        τ         ]     ≈       {     ∫         Δ                   y   s       -&gt;     ·        τ         }     ·           Ψ   ^       -&gt;   r       *     /              Ψ   ^       -&gt;   r            2                 (   25   )                 u   -&gt;     =       (         Δ                   y   s       -&gt;     ·           Ψ   ^       -&gt;   r       *     /              Ψ   ^       -&gt;   r            2         )     -     j   ·       n   ^     s     ·     [     ∫       u   -&gt;     ·        τ         ]                 (   26   )                   u   -&gt;     °     =              (         Δ                   y   s       -&gt;     ·           Ψ   ^       -&gt;   r       *     /              Ψ   ^       -&gt;   r            2         )       /        τ       -     j   ·       n   ^     s     ·     u   -&gt;                 (   27   )                                
     Under steady-state conditions, the quantities determined with equations (25) and (26) are then constant over time, and the quantity determined by equation (27) has a value of zero. The noise interference superimposed on the useful signals can now be attenuated comparatively easily to a sufficient extent by low-pass filtering. 
     FIG. 6 shows a block diagram of another embodiment of the device for carrying out the method according to the present invention, using the quantities determined by equations (25), (26) and (27). In this embodiment, the output of comparator device  46  is connected to an additional multiplier  58  instead of multiplier  36 ; the second input of this additional multiplier is connected to the output of lag element  16 , at whose input conjugated complex reference space vector            T   ^     -&gt;     *                          
     is available. 
     The output of this multiplier  58  is connected first to an additional adder  60  and second to an additional differentiator  62 , which is connected at the output to an input of an additional adder  64 . Signal processor  2 , which generates conjugated complex reference space vector              T   ^     -&gt;     *     ,                          
     also calculates the negative imaginary stator frequency−−j·{circumflex over (n)} s . This stator frequency −j·{circumflex over (n)} s  goes over a lag element  66  to an additional multiplier  68  and  70 . The output of multiplier  68  is connected to the second input of second adder  60 , whose output is connected first to an additional integrator  72  and second to multiplier  70 . The output of this integrator  72  is connected first to multiplier  68  and second to multiplier  50  at whose second input the complex factor  K   I  is available, which is delayed by lag element  54 . The output of multiplier  70  is connected to a second input of additional adder  64  by whose output supplies quantity              u   -&gt;     °     ·   Quantity                     u   -&gt;                            
     which is determined according to equation (26) is available at the output of additional adder  60 , and the quantity determined according to equation (25) is available at the output of additional integrator  72 . The outputs of multipliers  36  and  50  and the output of additional adder  64  are linked together by adder  52 . The imaginary component of this output quantity then forms system deviation Δ⊥ which is sent to equalizing controller  22 . 
     In this embodiment, complex factors  K   ω  and K I  are determined in device  44  according to the following rules: 
     
       
             K     ω ={circumflex over (ρ)}+1 +j ·( {circumflex over (n)}   s   +{circumflex over (n)}   r )  (28) 
       
     
     
       
             K     I   ={circumflex over (ρ)}·{circumflex over (σ)}−{circumflex over (n)}   r   +j· ({circumflex over (n)} s   +{circumflex over (ρ)}·{circumflex over (n)}   r )=Z  (29) 
       
     
     The resulting equation for determining system deviation Δ⊥ is then:                Δ   ⊥     =     Im        {         u   -&gt;     °     +       u   -&gt;     ·     [       ρ   ^     +   1   +     j   ·     (         n   ^     s     +       n   ^     r       )         ]       +       [     ∫       u   -&gt;     ·        τ         ]     ·     Z   _         }               (   30   )                                
     In the ideal case, real component Re at the second output of adder  52  is always equal to zero. For attenuation of residual errors that are technically unavoidable, the second scalar output signal, i.e., real component Re of the complex quantity at the output of adder  52 , can be multiplied by an attenuation factor D by an additional multiplier  74 . Output quantity ∥ of this additional multiplier  74  is superimposed on quantity        u   -&gt;                          
     by an additional adder  76 . The signal at the output of multiplier  74  formally has two identical coordinates, which is why the output signal of multiplier  74  is designated by two parallel lines. Since in the ideal case, real component Re of the output quantity of adder  52  is constantly equal to zero, this branch is represented by an interrupted line. 
     With regard to system deviation Δ∥, which is formed from the real component of the product at the output of second multiplier  20 , there is the problem that outside of the operating range with an extremely low stator frequency, the rotational speed determination by equalizing controller  22  and the stator resistance determination by equalizing controller  32  can interfere mutually with one another. In steady-state operation, the feedback effect of a rotational speed deviation An on system deviation Δ∥ can be prevented according to the present invention if complex factor  K   R  is determined in device  44  according to the following equation: 
     
       
             K     R   =−j·Z=−j[{circumflex over (ρ)}·{circumflex over (σ)}−{circumflex over (n)}   s   ·{circumflex over (n)}   r   +j ( {circumflex over (n)}   s   +{circumflex over (ρ)}·{circumflex over (n)}   r )]  (31) 
       
     
     The equation for determining system deviation Δ∥ is thus:                Δ        =     Re        {       -       Δ                   y   s       -&gt;       ·   j   ·     Z   _     ·           Ψ   ^       -&gt;   r       *     /              Ψ   ^       -&gt;   r            2         }               (   32   )                                
     In this application of equation (32), the quantity sign {circumflex over (n)} r  can be obtained from signal processor  2  as the input signal for correcting the control direction, which is sent to multiplier  34 . 
     FIG. 7 shows a block diagram of another embodiment of the device, which differs from the embodiment according to FIG. 6 in that now two additional multipliers  78 ,  80  and two lag elements  82 ,  84  are provided instead of multipliers  38 ,  20  and lag element  42 . The output of lag element  82  is connected to a first input of multiplier  78 , whose second input is connected to the second output of adder  52  at which real component Re of the complex quantity at the output of adder  52  [sic] is available. At the output, this multiplier  78  is connected first to the input of equalizing controller  32  and second to an input of multiplier  80  whose second input is connected to the output of lag element  84 . At the output, this multiplier  80  is connected to an additional adder  86  at whose second input is applied imaginary component Im of the complex output quantity of adder  52 . The output quantity of this adder  86  is system deviation Δ⊥ for adaptation of model parameter {circumflex over (n)}. Lag elements  82 ,  84  are connected at the input to the outputs of device  44 , where real factor K R  and real isolation factor K E  are applied. In device  44  in combination with signal processor  2 , required processing factors K R , K E ,  K   ω ,  K   I  are calculated according to the following equations: 
     
       
           K   R   ={circumflex over (n)}   s ·((1−{circumflex over (σ)}) 2 /(2 ·{circumflex over (σ)}·{circumflex over (n)}   r )  (33) 
       
     
     
       
           K   E =({circumflex over (σ)}− {circumflex over (n)}   r   2 )/[ {circumflex over (n)}   s ·(1−{circumflex over (σ)}) 2]   (34) 
       
     
     
       
             K     ω ={circumflex over (ρ)}+1 +j ·( {circumflex over (n)}   s   +{circumflex over (n)}   r )  (35) 
       
     
     
       
             K     I   =Z={circumflex over (ρ)}·{circumflex over (σ)}−{circumflex over (n)}   s   ·{circumflex over (n)}   r   +j· ( {circumflex over (n)}   s   +{circumflex over (ρ)}·{circumflex over (n)}   r )  (36) 
       
     
     System deviations Δ⊥ and Δ∥ are thus formed according to the following rules:                  Δ        =     Re          {         u   -&gt;     °     +       u   -&gt;     ·       K   _     ω       +       [     ∫       u   -&gt;     ·        τ         ]     ·       K   _     I         }     ·     K   R                         and           (   37   )                     Δ   ⊥     =       Im        {         u   -&gt;     °     +       u   -&gt;     ·       K   _     ω       +       [     ∫       u   -&gt;     ·        τ         ]     ·       K   _     I         }       +   Δ            ·     K   E             (   38   )                                
     With this embodiment, the corrections of system deviations Δ⊥ and Δ∥ can be isolated not only under steady-state conditions but also under fully dynamic conditions. 
     Isolation of the corrections of system deviations Δ⊥ and Δ∥ that is very good under steady-state conditions and is adequate under dynamic conditions is possible even without integration of quantity        u   -&gt;                          
     defined by equation (26) or the quantity according to equation (25). 
     In this case, the equations for determination of processing factors K R , K E  and  K   ω  are as follows: 
     
       
           K   R   ={circumflex over (n)}   s ·(1−{circumflex over (σ)}) 2 /(2 ·{circumflex over (σ)}·{circumflex over (n)}   r )  (33) 
       
     
     
       
           K   E =({circumflex over (σ)}− {circumflex over (n)}   r   2 )/[ {circumflex over (n)}   s ·(1−{circumflex over (σ)}) 2 ]  (34) 
       
     
     and 
     
       
             K     ω =1 +{circumflex over (ρ)}·{circumflex over (n)}   r   /{circumflex over (n)}   s   −j·[{circumflex over (ρ)}·{circumflex over (σ)}/{circumflex over (n)}   s   −{circumflex over (n)}   r ]  (39) 
       
     
     System deviations Δ⊥ and Δ∥ are then formed according to the following rules:                  Δ        =     Re          {         v   -&gt;     °     +       v   -&gt;     ·       K   _     ω         }     ·     K   R                         and           (   40   )                       Δ   ⊥     =       Im        {         v   -&gt;     °     +       v   -&gt;     ·       K   _     ω         }       +   Δ            ·     K   E                     where                       v   -&gt;     =     (         Δ                   y   s       -&gt;     ·           Ψ   ^       -&gt;   r       *     /              Ψ   ^       -&gt;   r            2         )       ;                    v   -&gt;     °     =            v   -&gt;            τ                   (   41   )                                
     FIG. 8 shows a block diagram of a corresponding embodiment formed by omitting the following elements from the embodiment according to FIG.  7 : 
     lag elements  54  and  66 , multipliers  50 ,  68  and  70 , integrator  72  and adders  60  and  64 . 
     It should be pointed out that since the operating parameters stator frequency ñ s  and rotor frequency ñ r  also occur as factors in the denominator of fractions in equations (33) through (41), these quantities are to be limited to minimum values before the corresponding division. 
     By using processing factor  K   ω  for stator current model space vector              i   ^     s     -&gt;     ,                          
     stator current real space vector          i   s     -&gt;                          
     or normalized differential current space vector            Δ                   y   s       -&gt;     ,                          
     the dependence of steady-state transfer factor {umlaut over ({tilde over (u)})} on the operating parameter rotor frequency ñ r  can be greatly reduced. By using all processing factors  K   ω ,  K   R  and K E , K R , transfer factor ü may have a constant value of one for steady-state and dynamic operating conditions, with the corrections of system deviations Δ⊥ and Δ∥ also being fully isolated even under dynamic conditions.