CN110120763A - A kind of permanent magnet synchronous motor is without weight coefficient prediction method for controlling torque - Google Patents

Abstract

The present invention proposes a method for predicting the torque of a permanent magnet synchronous motor without weight coefficients, the steps of which are: sampling the three-phase current, angular velocity and rotor position angle of the permanent magnet synchronous motor at time k, and obtaining the output current and etc. Calculate the output voltage vector and stator voltage according to the switching state of the voltage source inverter, and predict the output current, stator flux linkage, and stator flux amplitude and torque at time k+1 according to the stator voltage; then The torque objective function and the stator flux objective function are calculated by using the stator flux amplitude and torque, and then a new objective function is obtained; finally, the value of the objective function is compared, and the voltage vector corresponding to the minimum objective function is used for control permanent magnet synchronous motor. The present invention realizes the non-weight coefficient predictive torque control of the permanent magnet synchronous motor by standardizing the torque and flux linkage objective functions with two norms, can simplify the system complexity, reduce the torque ripple, and improve the torque control precision.

Description

A non-weight coefficient predictive torque control method for permanent magnet synchronous motor

technical field

The invention relates to the field of power electronics, in particular to a non-weight coefficient predictive torque control method for a permanent magnet synchronous motor.

Background technique

In recent years, in order to cope with the energy crisis, new energy electric vehicle technology has been vigorously developed. Compared with asynchronous motors, permanent magnet synchronous motors (Permanent Magnet Synchronous Motor, PMSM) have been widely used in the field of electric vehicles because of their high efficiency, high power density and many other advantages. In order to improve the torque dynamic control characteristics of permanent magnet synchronous motors, model predictive control is widely used in the drive control of permanent magnet synchronous motors. However, the conventional predictive torque control method of permanent magnet synchronous motor has the disadvantage of needing to design weight coefficients. Although the literature has studied the non-weight coefficient predictive torque control method of permanent magnet synchronous motor, but so far, there is still no good weight coefficient theoretical design method.

At present, there is a control method for torque prediction of permanent magnet synchronous motors. For example, the application number is 201611046203.X, and the name of the invention is a fast weightless coefficient model predictive control calculation method and its system. A fast weightless coefficient model prediction method is proposed. In the control method, by using the target voltage vector as the objective function, the use of weight coefficients is avoided, so that the fast non-weight coefficient control of the multilevel converter can be realized. However, this method cannot be used to realize predictive torque control of permanent magnet synchronous motors. The application number is 201810724498.4, and the name of the invention is a linear induction motor thrust control method without weight coefficient model prediction. A linear induction motor thrust control method without weight coefficient model prediction with thrust and conjugate thrust as the objective function is proposed. By rewriting the objective function , transforming the thrust and flux linkages of different dimensions into the same dimension, thus avoiding the use of weight coefficients. However, this invention patent is for linear induction motors and cannot be directly applied to permanent magnet synchronous motors. The application number is 201811426304.9, and the name of the invention is a weightless predictive torque control method for permanent magnet motor systems based on discrete duty cycles. A weightless predictive torque control method for permanent magnet synchronous motors is proposed, which is calculated based on flux linkage and torque commands. Reference voltage command, and use the reference voltage to establish the objective function, thereby eliminating the weight coefficient. Although this method can realize the weightless predictive torque control of the permanent magnet motor system, it needs complex calculations to obtain the target voltage vector. Literature [Xu Yanping, Li Yuanyuan, Zhou Qin. Dual-model predictive torque control strategy for permanent magnet synchronous motors [J]. Power Electronics Technology, 2018, 52(06): 37-39] proposed a dual-model predictive method for permanent magnet synchronous motors Torque control can effectively reduce the torque ripple and reduce the calculation amount of the algorithm. However, in this method, weight factors need to be designed, and the design of weight factors is difficult.

Contents of the invention

Aiming at the technical problem of complex calculation in the existing control method for torque prediction of permanent magnet synchronous motors, the present invention proposes a non-weight coefficient predictive torque control method for permanent magnet synchronous motors, and establishes two parameters of torque and flux linkage. objective function, and a new objective function without weight coefficient is obtained through two-norm standardization, so that the predictive torque control without weight coefficient of permanent magnet synchronous motor is finally realized, which simplifies the algorithm complexity and reduces the torque ripple.

Technical scheme of the present invention is realized like this:

A non-weight coefficient predictive torque control method for a permanent magnet synchronous motor, the steps of which are as follows:

Step 1. Sampling the three-phase currents ia, ib, ic of the permanent magnet synchronous motor at time k, the angular velocity ω _r of the permanent magnet synchronous motor, and the rotor position angle θ _r , and _calculating the three-phase currents _{i a , i b ,} i _c obtains the output current i _α and i _β in the static αβ coordinate system through coordinate transformation;

Step 2. Use the rotor position angle θ _r in step 1 to perform coordinate transformation on the output currents i _α and i _β to obtain d-axis current i _d and q-axis current i _q respectively, and then convert the angular velocity ω _r and rotor The position angle θ _r and the d-axis current i _d are substituted into the equivalent back electromotive force mathematical model of the permanent magnet synchronous motor, and the equivalent back electromotive force e _α and e _β of the permanent magnet synchronous motor are calculated;

Step 3. Obtain the voltage vector V _i (S _a S _b S _c ) output by the voltage source inverter according to the switching states S _a , S _b , and S _c of the voltage source inverter, where i=0,1, 2, 3, 4, 5, 6, 7, the values of switch states S _a , S _b , and S _c are equal to 0 or 1;

Step 4. According to the DC voltage U _dc of the voltage source inverter, perform coordinate transformation on the switching states S _a , S _b , and S _c corresponding to the voltage vector V _i (S _a S _b S _c ) in step 3 to obtain the inverter The output voltage of the device, that is, the stator voltage u _αi and u _βi of the permanent magnet synchronous motor;

Step 5. Substitute the output current i _α , i _β obtained in step 1, the equivalent back electromotive force e _α , e _β obtained in step 2, and the stator voltage u _αi , u _βi obtained in step 4 into the discrete current prediction of the permanent magnet synchronous motor The model predicts the output current i _αi (k+1) and i _βi (k+1) at time k+1;

Step 6. Substitute the output current i _αi (k+1), i _βi (k+1)i _β obtained in step 5 and the equivalent counter electromotive force e _α and e _β obtained in step 2 into the stator flux linkage of the permanent magnet synchronous motor The prediction model predicts the stator flux linkage ψ _αi (k+1) and ψ _βi (k+1) at time k+1 and calculates the stator flux amplitude ψ _si (k+1);

Step 7. Substitute the output current i _αi (k+1), i _βi (k+1) obtained in step 5 and the stator flux linkage ψ _αi (k+1) and ψ _βi (k+1) obtained in step 6 into the permanent The torque prediction model of the magnetic synchronous motor is calculated to obtain the torque T _ei (k+1) of the permanent magnet synchronous motor;

Step 8. Set the reference motor torque according to the load requirement and according to the reference motor torque Calculate reference stator flux linkage

Step 9. Calculate the reference motor torque Subtract the absolute value of the torque T _ei (k+1) obtained in step 7 to obtain the torque target function g _Ti , and calculate the reference stator flux linkage Subtract the absolute value of the stator flux amplitude ψ _si (k+1) obtained in step 6 to obtain the stator flux objective function g _ψi ;

Step 10: Carry out two-norm standardization on the torque objective function g _Ti and the stator flux linkage objective function g _ψi obtained in step 9 respectively, and calculate a new objective function G _i by means of fusion;

Step 11: Compare the value of the objective function G _i , use the voltage vector V _i (S _a S _b S _c ) corresponding to the smallest objective function G _i as the optimal vector, and use the optimal vector to control the permanent magnet synchronous motor .

Preferably, the three-phase currents i _a , i _b , and i _c in the step 1 are transformed through coordinate transformation to obtain the output currents i _α and i _β in the static αβ coordinate system as:

Preferably, the method for obtaining the current id and current _iq of the _d -axis and q-axis in the step 2 is:

Among them, _θr is the rotor position angle of the permanent magnet synchronous motor;

The equivalent counter electromotive force mathematical model of the permanent magnet synchronous motor is:

Among them, ω _r is the angular velocity of the permanent magnet synchronous motor, ψ _f is the permanent magnet flux linkage of the permanent magnet synchronous motor, L _d and L _q are the stator inductance of the permanent magnet synchronous motor.

Preferably, the method for obtaining the voltage vector V _i (S _a S _b S _c ) in the step 3 is:

S _a =1 means that the upper switch of the a-phase bridge arm of the bidirectional AC-DC converter is turned on, and the lower switch is turned off;

S _a =0 means that the upper switch of the a-phase bridge arm of the bidirectional AC-DC converter is turned off, and the lower switch is turned on;

S _b = 1 means that the upper switch of the b-phase bridge arm of the bidirectional AC-DC converter is turned on, and the lower switch is turned off;

S _b = 0 means that the upper switch of the b-phase bridge arm of the bidirectional AC-DC converter is turned off, and the lower switch is turned on;

S _c =1 means that the upper switch of the c-phase bridge arm of the bidirectional AC-DC converter is turned on, and the lower switch is turned off;

S _c =0 means that the upper switch of the c-phase bridge arm of the bidirectional AC-DC converter is turned off, and the lower switch is turned on;

If S _a =0, S _b =0, S _c =0, the voltage vector is recorded as V ₀ (000);

If S _a =1, S _b =0, S _c =0, the voltage vector is denoted as V ₁ (100);

If S _a =1, S _b =1, S _c =0, the voltage vector is recorded as V ₂ (110);

If S _a =0, S _b =1, S _c =0, the voltage vector is recorded as V ₃ (010);

If S _a =0, S _b =1, S _c =1, the voltage vector is recorded as V ₄ (011);

If S _a =0, S _b =0, S _c =1, the voltage vector is recorded as V ₅ (001);

If S _a =1, S _b =0, S _c =1, the voltage vector is recorded as V ₆ (101);

If S _a =1, S _b =1, S _c =1, the voltage vector is denoted as V ₇ (111).

Preferably, the method for obtaining the stator voltages u _αi and u _βi of the permanent magnet synchronous motor in the step 4 is:

Where, i=0,1,2,3,4,5,6,7, S _ai is the switch state S _a corresponding to the voltage vector V _i (S _a S _b S _c ), and S _bi is the voltage vector V _i ( The switch state S _b corresponding to S _a S _b S _c ), and S _ci is the switch state S _c corresponding to the voltage vector V _i (S _a S _b S _c ).

Preferably, the discrete current prediction model of the permanent magnet synchronous motor in the step five is:

Among them, e _α and e _β are the equivalent back electromotive force of the permanent magnet synchronous motor, T _s is the sampling period, R _s is the stator resistance of the permanent magnet synchronous motor, and L _q is the stator inductance of the permanent magnet synchronous motor;

The stator flux linkage prediction model of the permanent magnet synchronous motor in the described step 6 is:

Among them, ω _r is the angular velocity of the permanent magnet synchronous motor;

The method for obtaining the stator flux linkage amplitude ψ _si (k+1) in the step six is:

The torque prediction model of the permanent magnet synchronous motor in the described step 7 is:

Among them, n _p is the number of pole pairs of the permanent magnet synchronous motor.

Preferably, the reference motor torque is utilized in said step eight Calculating Reference Flux Linkage The method is:

Among them, ψ _f is the permanent magnet flux linkage of the permanent magnet synchronous motor.

Preferably, the method for obtaining the torque target function _gTi and the stator flux linkage target function _gψi in the step 9 is:

Preferably, the method for obtaining the objective function G _i in the step ten is:

Beneficial effects produced by this technical solution: By adopting the two objective functions of torque and flux linkage, the torque and flux linkage control of the permanent magnet synchronous motor can be realized without weight coefficients, which not only reduces the complexity of system design and debugging Degree, and help to reduce torque ripple, improve torque control accuracy.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is the overall structural block diagram of the present invention.

Figure 2 is the simulation result of the literature [Xu Yanping, Li Yuanyuan, Zhou Qin. Dual-model predictive torque control strategy for permanent magnet synchronous motors [J]. Power Electronics Technology, 2018,52(06):37-39]; (a) is the simulation result diagram of torque error and torque, (b) is the simulation result diagram of flux linkage error and flux linkage.

Fig. 3 is the simulation result figure of the present invention; (a) is the simulation result figure of torque error and torque, (b) is the simulation result figure of flux linkage error and flux linkage.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

As shown in Figure 1, a non-weight coefficient predictive torque control method for permanent magnet synchronous motors, the steps are as follows:

Step 1. Sampling the three-phase currents i _a , i _b , i _c of the permanent magnet synchronous motor at time k, the angular velocity ω _r of the permanent magnet synchronous motor, and the rotor position angle θ _r , and using the formula (1) to convert the three-phase current i _a , i _b , i _c obtain the output current i _α and i _β in the static αβ coordinate system through coordinate transformation:

Step 2. Use the rotor position angle θ _r in step 1 to perform coordinate transformation on the output currents i _α and i _β according to the formula (2) to obtain the d-axis current i _d and the q-axis current i _q respectively:

Then substituting angular velocity ω _r , rotor position angle θ _r and d-axis current i _d into the equivalent back electromotive force mathematical model of the permanent magnet synchronous motor, the equivalent back electromotive force e _α and e _β of the permanent magnet synchronous motor are calculated, as shown in the formula (3) as shown:

Among them, ψ _f is the permanent magnet flux linkage of the permanent magnet synchronous motor, and L _d and L _q are the stator inductance of the permanent magnet synchronous motor.

Step 3. Obtain the voltage vector V _i (S _a S _b S _c ) output by the voltage source inverter according to the switching states S _a , S _b , and S _c of the voltage source inverter, where i=0,1, 2, 3, 4, 5, 6, 7, the value of switch state S _a , S _b , S _c is equal to 0 or 1:

S _a =1 means that the upper switch of the a-phase bridge arm of the bidirectional AC-DC converter is turned on, and the lower switch is turned off;

S _a =0 means that the upper switch of the a-phase bridge arm of the bidirectional AC-DC converter is turned off, and the lower switch is turned on;

S _b = 1 means that the upper switch of the b-phase bridge arm of the bidirectional AC-DC converter is turned on, and the lower switch is turned off;

S _b = 0 means that the upper switch of the b-phase bridge arm of the bidirectional AC-DC converter is turned off, and the lower switch is turned on;

S _c =1 means that the upper switch of the c-phase bridge arm of the bidirectional AC-DC converter is turned on, and the lower switch is turned off;

S _c =0 means that the upper switch of the c-phase bridge arm of the bidirectional AC-DC converter is turned off, and the lower switch is turned on;

If S _a =0, S _b =0, S _c =0, the voltage vector is recorded as V ₀ (000);

If S _a =1, S _b =0, S _c =0, the voltage vector is denoted as V ₁ (100);

If S _a =1, S _b =1, S _c =0, the voltage vector is recorded as V ₂ (110);

If S _a =0, S _b =1, S _c =0, the voltage vector is recorded as V ₃ (010);

If S _a =0, S _b =1, S _c =1, the voltage vector is recorded as V ₄ (011);

If S _a =0, S _b =0, S _c =1, the voltage vector is recorded as V ₅ (001);

If S _a =1, S _b =0, S _c =1, the voltage vector is recorded as V ₆ (101);

If S _a =1, S _b =1, S _c =1, the voltage vector is denoted as V ₇ (111).

Therefore, the eight voltage vectors output by the voltage source inverter are recorded as V ₀ (000), V ₁ (100), V ₂ (110), V ₃ (010), V ₄ (011), V ₅ (001 ), V ₆ (101) and V ₇ (111).

Step 4. According to the DC voltage U _dc of the voltage source inverter, perform coordinate transformation on the switching states S _a , S _b , and S _c corresponding to the voltage vector V _i (S _a S _b S _c ) in step 3 to obtain the inverter The output voltage of the device, that is, the stator voltage u _αi and u _βi of the permanent magnet synchronous motor, as shown in formula (4):

Among them, i=0,1,2,3,4,5,6,7, S _ai is equal to the switch state S _a corresponding to the voltage vector V _i (S _a S _b S _c ), and S _bi is equal to the voltage vector V _i ( The switch state S _b corresponding to S _a S _b S _c ), S _ci is equal to the switch state S _c corresponding to the voltage vector V _i (S _a S _b S _c ).

Step 5. Substitute the output current i _α , i _β obtained in step 1, the equivalent back electromotive force e _α , e _β obtained in step 2, and the stator voltage u _αi , u _βi obtained in step 4 into the discrete current prediction of the permanent magnet synchronous motor The model predicts the output current i _αi (k+1) and i _βi (k+1) at time k+1, as shown in formula (5):

Among them, i=0,1,2,3,4,5,6,7, T _s is the sampling period, R _s is the stator resistance of the permanent magnet synchronous motor, and L _q is the stator inductance of the permanent magnet synchronous motor.

Step 6. Substitute the output current i _αi (k+1), i _βi (k+1) obtained in step 5 and the equivalent counter electromotive force e _α and e _β obtained in step 2 into the stator flux linkage prediction model of the permanent magnet synchronous motor Predict the stator flux linkage ψ _αi (k+1) and ψ _βi (k+1) at time k+1 and calculate the stator flux amplitude ψ _si (k+1), as shown in formula (6) and formula (7) Show:

Among them, i=0,1,2,3,4,5,6,7, e _α and e _β are the equivalent counter electromotive force of the permanent magnet synchronous motor, ω _r is the angular velocity of the permanent magnet synchronous motor.

Step 7. Substitute the output current i _αi (k+1), i _βi (k+1) obtained in step 5 and the stator flux linkage ψ _αi (k+1) and ψ _βi (k+1) obtained in step 6 into the permanent The torque prediction model of the magnetic synchronous motor calculates the torque T _ei (k+1) of the permanent magnet synchronous motor, as shown in formula (8):

Among them, i=0,1,2,3,4,5,6,7, n _p is the number of pole pairs of the permanent magnet synchronous motor.

Step 8. Set the reference motor torque according to the load requirement and according to the reference motor torque The reference stator flux linkage is calculated by formula (9)

Among them, n _p is the number of pole pairs of the permanent magnet synchronous motor, ψ _f is the permanent magnet flux linkage of the permanent magnet synchronous motor, and L _q is the stator inductance of the permanent magnet synchronous motor.

Step 9. Calculate reference stator flux linkage Subtract the absolute value of the stator flux amplitude ψ _si (k+1) obtained in step 6 to obtain the stator flux objective function g _ψi , and calculate the reference motor torque Subtract the absolute value of the torque T _ei (k+1) obtained in step 7 to obtain the torque target function g _Ti , as shown in formula (10):

Wherein, i=0,1,2,3,4,5,6,7.

Step 10: Perform two-norm standardization on the torque objective function g _Ti and the stator flux objective function g _ψi obtained in step 9 respectively, and calculate the new objective function G _i by means of fusion, as shown in formula (11) :

Wherein, i=0,1,2,3,4,5,6,7.

Step 11. Compare the value of the objective function G _i , take the voltage vector V _i (S _a S _b S _c ) corresponding to the smallest objective function G _i as the most effective vector, and use the most effective vector to control the permanent magnet synchronous motor .

In order to verify the effectiveness of the present invention, simulation verification is carried out with the traditional permanent magnet synchronous motor predictive torque control scheme. During the simulation, the DC side voltage U _dc of the grid-connected inverter is 600V, the motor stator resistance R _s is 0.0154Ω, the permanent magnet flux linkage ψ _f is 1.5Wb, the d-axis inductance L _d is 4mH, and the q-axis inductance L _q is 9mH, the number of motor pole pairs n _p is 3, the reference motor torque is 300Nm. Figure 2 shows the simulation results of the literature [Xu Yanping, Li Yuanyuan, Zhou Qin. Dual-model predictive torque control strategy for permanent magnet synchronous motors [J]. Power Electronics Technology, 2018,52(06):37-39], Figure 3 The simulation results of the present invention are given. As shown in Figure 2, due to the lack of a mature weight factor design theory in the traditional PMSM predictive torque control scheme, it is difficult to obtain the optimal stator flux linkage and torque control effect at the same time, that is, the torque error and the rotational speed The wave form of moment and the wave form fluctuation of flux linkage error and flux linkage are all relatively large; As shown in Figure 3, the present invention has obtained a new one because of having set up two objective functions of torque and flux linkage, and by two-norm standardization The objective function without the weight coefficient realizes the torque and flux linkage control of the permanent magnet synchronous motor, and reduces the torque error and the waveform of the torque, as well as the fluctuation range of the flux linkage error and the flux linkage. The invention does not need weight coefficients, which not only reduces the complexity of system design and debugging, but also helps to reduce torque ripple and improve torque control precision.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (9)

1. a permanent magnet synchronous motor non-weight coefficient predictive torque control method, is characterized in that, its steps are as follows: Step 1. Sampling the three-phase currents ia, ib, ic of the permanent magnet synchronous motor at time k, the angular velocity ω _r of the permanent magnet synchronous motor, and the rotor position angle θ _r , and _calculating the three-phase currents _{i a , i b ,} i _c obtains the output current i _α and i _β in the static αβ coordinate system through coordinate transformation; Step 2. Use the rotor position angle θ _r in step 1 to perform coordinate transformation on the output currents i _α and i _β to obtain d-axis current i _d and q-axis current i _q respectively, and then convert the angular velocity ω _r and rotor The position angle θ _r and the d-axis current i _d are substituted into the equivalent back electromotive force mathematical model of the permanent magnet synchronous motor, and the equivalent back electromotive force e _α and e _β of the permanent magnet synchronous motor are calculated; Step 3. Obtain the voltage vector V _i (S _a S _b S _c ) output by the voltage source inverter according to the switching states S _a , S _b , and S _c of the voltage source inverter, where i=0,1, 2, 3, 4, 5, 6, 7, the values of switch states S _a , S _b , and S _c are equal to 0 or 1; Step 4. According to the DC voltage U _dc of the voltage source inverter, perform coordinate transformation on the switching states S _a , S _b , and S _c corresponding to the voltage vector V _i (S _a S _b S _c ) in step 3 to obtain the inverter The output voltage of the device, that is, the stator voltage u _αi and u _βi of the permanent magnet synchronous motor; Step 5. Substitute the output current i _α , i _β obtained in step 1, the equivalent back electromotive force e _α , e _β obtained in step 2, and the stator voltage u _αi , u _βi obtained in step 4 into the discrete current prediction of the permanent magnet synchronous motor The model predicts the output current i _αi (k+1) and i _βi (k+1) at time k+1; Step 6. Substitute the output current i _αi (k+1), i _βi (k+1)i _β obtained in step 5 and the equivalent counter electromotive force e _α and e _β obtained in step 2 into the stator flux linkage of the permanent magnet synchronous motor The prediction model predicts the stator flux linkage ψ _αi (k+1) and ψ _βi (k+1) at time k+1 and calculates the stator flux amplitude ψ _si (k+1); Step 7. Substitute the output current i _αi (k+1), i _βi (k+1) obtained in step 5 and the stator flux linkage ψ _αi (k+1) and ψ _βi (k+1) obtained in step 6 into the permanent The torque prediction model of the magnetic synchronous motor is calculated to obtain the torque T _ei (k+1) of the permanent magnet synchronous motor; Step 8. Set the reference motor torque according to the load requirement and according to the reference motor torque Calculate reference stator flux linkage Step 9. Calculate the reference motor torque Subtract the absolute value of the torque T _ei (k+1) obtained in step 7 to obtain the torque target function g _Ti , and calculate the reference stator flux linkage Subtract the absolute value of the stator flux amplitude ψ _si (k+1) obtained in step 6 to obtain the stator flux objective function g _ψi ; Step 10: Carry out two-norm standardization on the torque objective function g _Ti and the stator flux linkage objective function g _ψi obtained in step 9 respectively, and calculate a new objective function G _i by means of fusion; Step 11: Compare the value of the objective function G _i , use the voltage vector V _i (S _a S _b S _c ) corresponding to the smallest objective function G _i as the optimal vector, and use the optimal vector to control the permanent magnet synchronous motor . 2. The non-weight coefficient predictive torque control method for permanent magnet synchronous motors according to claim 1, wherein the three-phase currents _ia , _ib , and _ic in the step 1 are obtained by coordinate transformation to obtain the static αβ coordinates The output currents i _α and i _β under the system are: 3. permanent magnet synchronous motor according to claim 1 has no weight coefficient predictive torque control method, it is characterized in that, the obtaining method of the electric current i _d and electric current i _q of d axis and q axis in described step 2 is: Among them, _θr is the rotor position angle of the permanent magnet synchronous motor; The equivalent counter electromotive force mathematical model of the permanent magnet synchronous motor is: Among them, ω _r is the angular velocity of the permanent magnet synchronous motor, ψ _f is the permanent magnet flux linkage of the permanent magnet synchronous motor, L _d and L _q are the stator inductance of the permanent magnet synchronous motor. 4. The non-weight coefficient predictive torque control method of permanent magnet synchronous motor according to claim 1, wherein the method for obtaining the voltage vector V _i (S _a S _b S _c ) in the step 3 is: S _a =1 means that the upper switch of the a-phase bridge arm of the bidirectional AC-DC converter is turned on, and the lower switch is turned off; S _a =0 means that the upper switch of the a-phase bridge arm of the bidirectional AC-DC converter is turned off, and the lower switch is turned on; S _b = 1 means that the upper switch of the b-phase bridge arm of the bidirectional AC-DC converter is turned on, and the lower switch is turned off; S _b = 0 means that the upper switch of the b-phase bridge arm of the bidirectional AC-DC converter is turned off, and the lower switch is turned on; S _c =1 means that the upper switch of the c-phase bridge arm of the bidirectional AC-DC converter is turned on, and the lower switch is turned off; S _c =0 means that the upper switch of the c-phase bridge arm of the bidirectional AC-DC converter is turned off, and the lower switch is turned on; If S _a =0, S _b =0, S _c =0, the voltage vector is recorded as V ₀ (000); If S _a =1, S _b =0, S _c =0, the voltage vector is denoted as V ₁ (100); If S _a =1, S _b =1, S _c =0, the voltage vector is recorded as V ₂ (110); If S _a =0, S _b =1, S _c =0, the voltage vector is recorded as V ₃ (010); If S _a =0, S _b =1, S _c =1, the voltage vector is recorded as V ₄ (011); If S _a =0, S _b =0, S _c =1, the voltage vector is recorded as V ₅ (001); If S _a =1, S _b =0, S _c =1, the voltage vector is recorded as V ₆ (101); If S _a =1, S _b =1, S _c =1, the voltage vector is denoted as V ₇ (111). 5. according to claim 1 or 4 described permanent magnet synchronous motor non-weight coefficient predictive torque control method, it is characterized in that, the obtaining method of the stator voltage u _αi and u _βi of the permanent magnet synchronous motor in the described step 4 is : Where, i=0,1,2,3,4,5,6,7, S _ai is the switch state S _a corresponding to the voltage vector V _i (S _a S _b S _c ), and S _bi is the voltage vector V _i ( The switch state S _b corresponding to S _a S _b S _c ), and S _ci is the switch state S _c corresponding to the voltage vector V _i (S _a S _b S _c ). 6. the non-weight coefficient predictive torque control method of permanent magnet synchronous motor according to claim 5, is characterized in that, the discrete current prediction model of permanent magnet synchronous motor in the described step 5 is: Among them, e _α and e _β are the equivalent back electromotive force of the permanent magnet synchronous motor, T _s is the sampling period, R _s is the stator resistance of the permanent magnet synchronous motor, and L _q is the stator inductance of the permanent magnet synchronous motor; The stator flux linkage prediction model of the permanent magnet synchronous motor in the described step 6 is: Among them, ω _r is the angular velocity of the permanent magnet synchronous motor; The method for obtaining the stator flux linkage amplitude ψ _si (k+1) in the step six is: The torque prediction model of the permanent magnet synchronous motor in the described step 7 is: Among them, n _p is the number of pole pairs of the permanent magnet synchronous motor. 7. The non-weight coefficient predictive torque control method of permanent magnet synchronous motor according to claim 6, characterized in that, in the step eight, reference motor torque is utilized Calculating Reference Flux Linkage The method is: Among them, ψ _f is the permanent magnet flux linkage of the permanent magnet synchronous motor. 8. The non-weight coefficient predictive torque control method of permanent magnet synchronous motor according to claim 7, is characterized in that, the acquisition method of the torque target function _gTi and the stator flux linkage target function _gψi in the said step 9 is : 9. The non-weight coefficient predictive torque control method of permanent magnet synchronous motor according to claim 8, characterized in that, the method for obtaining the objective function _Gi in the step ten is: