阅读说明：本技术 一种三相开关磁阻电机四象限复合转速控制方法 (Four-quadrant composite rotating speed control method for three-phase switched reluctance motor ) 是由 宋受俊 刘家良 袁瑞林 崔启文 窦满峰 刘卫国 于 2021-08-23 设计创作，主要内容包括：本发明公开了一种三相开关磁阻电机四象限复合转速控制方法。对模型预测控制方法进行改进,使其具有在线调节关断角的能力,并通过与无差拍控制方法相结合,形成一种三相开关磁阻电机复合转速控制方法,在双向作用区采用改进后的模型预测控制方法,在单相作用区采用无差拍控制方法。针对开关磁阻电机无法通过电流反向输出制动转矩的问题,将复合转速控制方法扩展至制动运行工况,进而获得一种三相开关磁阻电机四象限复合转速控制方法。本发明所公开的方法可以在抑制转矩波动的同时实现三相开关磁阻电机的四象限运行,并且还能够兼顾电机的效率,对于开关磁阻电机的四象限转速伺服应用具有重要的意义。(The invention discloses a four-quadrant composite rotating speed control method of a three-phase switched reluctance motor. The model prediction control method is improved to have the capability of adjusting the turn-off angle on line, and is combined with the dead-beat control method to form a three-phase switch reluctance motor composite rotating speed control method. Aiming at the problem that the switched reluctance motor cannot reversely output the braking torque through current, the composite rotating speed control method is expanded to the braking operation working condition, and then the four-quadrant composite rotating speed control method of the three-phase switched reluctance motor is obtained. The method disclosed by the invention can realize the four-quadrant operation of the three-phase switched reluctance motor while inhibiting the torque fluctuation, can also consider the efficiency of the motor, and has important significance for the four-quadrant rotating speed servo application of the switched reluctance motor.)

1. A four-quadrant composite rotating speed control method for a three-phase switch reluctance motor is characterized in that a model prediction control method is improved, and is combined with a dead-beat control method, then the model prediction control method is expanded to a brake operation working condition, torque fluctuation is inhibited, and meanwhile four-quadrant rotating speed control of the three-phase switch reluctance motor is achieved, and the method is achieved by the following steps:

the method comprises the following steps: judging the action area and the single-phase action area of the phase winding of the switched reluctance motor, and turning to the second step, the double-phase action area and the third step;

step two: in a positive rotation single-phase action area, no matter under an electric working condition or a braking working condition, a dead beat control method is adopted; by psi (k +1) ═ psi (k) + [ U_dcD-i(k)R]T_sEstimating the flux linkage of two demagnetized phases at the next sampling time, wherein psi (k +1) is the flux linkage of the phase at the next sampling time, psi (k) is the flux linkage of the phase at the current sampling time, and U_dcIs the bus voltage, D is the duty cycle, i (k) is the phase current at the current sampling time, R is the phase resistance, T_sIs a sampling period; by θ (k +1) ═ θ (k) + ω T_sEstimating the rotor positions of two demagnetizing phases at the next sampling moment, wherein theta (k +1) is the rotor position at the next sampling moment, theta (k) is the rotor position at the current sampling moment, and omega is the rotating speed of the motor; and obtaining phase currents of the two demagnetizing phases at the next sampling moment through a lookup table i (psi, theta) by utilizing the flux linkage and the rotor position of the two demagnetizing phases at the next sampling moment, and obtaining phase torque T of the two demagnetizing phases at the next sampling moment through a lookup table T (i, theta)_o1(k +1) and T_o2(k + 1); through T_refi(k+1)＝T_ref(k)-T_o1(k+1)-T_o2(k +1) calculating a reference torque of the excitation phase at the next sampling moment, which isMiddle T_refi(k +1) is the reference torque of the excitation phase at the next sampling instant, T_ref(k) The total reference torque of the current sampling moment obtained by the rotating speed ring; by T_refi(k +1), obtaining the reference current of the excitation phase at the next sampling moment through a lookup table i (T, theta), and obtaining the reference flux linkage psi of the excitation phase at the next sampling moment through a lookup table psi (i, theta)_refi(k + 1); by making use of psi_refi(k +1) by U_i(k)＝i(k)R+[ψ_refi(k+1)-ψ_i(k)]/T_sObtaining the phase voltage U to be applied to the excitation phase at the current sampling moment_i(k) Wherein ψ_i(k) The phase flux linkage of the excitation phase for the current sampling moment and then through D_i(k)＝U_i(k)/U_dcObtaining the duty ratio D of the excitation phase pulse width modulation control signal at the current sampling moment_i(k) Applying the pulse width modulation control signal to a switch tube corresponding to excitation in the power converter to complete control; for the single-phase action zone of the reverse rotation, no matter the electric working condition or the braking working condition, compared with the single-phase action zone of the forward rotation, the control process of the single-phase action zone of the reverse rotation only has the difference of an excitation phase sequence; defining phases of a three-phase switched reluctance motor as an A phase, a B phase and a C phase respectively, wherein the excitation phase sequence of positive rotation is A-B-C, and the phase sequence of reverse rotation is A-C-B;

step three: in the biphasic region, by (tau/2-theta)_o) Omega and psi_o/U_dcThe magnitude relation between the two determines whether the demagnetizing phase needs to enter a complete turn-off state, wherein tau is the polar distance of the rotor, and theta_oFor demagnetising the rotor position, psi_oIs a demagnetized phase flux linkage; when (tau/2-theta)_o)/ω＞ψ_o/U_dcWhen the demagnetization phase does not need to enter a complete turn-off state, the step four is carried out, and when the step is (tau/2-theta)_o)/ω≤ψ_o/U_dcWhen the demagnetization phase needs to enter a complete turn-off state, a dead-beat control method of a single-phase action area is adopted, and the step II is carried out;

step four: the switched reluctance motor rotates forwards, and a model prediction control method is adopted in a double-phase action area no matter under the electric working condition or the braking working condition and when a demagnetization phase does not need to enter a complete turn-off state; suppose that the flux linkage ψ (k +1) of each phase at the next sampling time is equal to the current samplingThe flux linkage ψ (k) at the time passes θ (k +1) to θ (k) + ω T_sEstimating the rotor position of each phase at the next sampling moment; obtaining phase current of each phase at the next sampling moment through a lookup table i (psi, theta) by utilizing psi (k +1) and theta (k +1), obtaining phase torque of each phase at the next sampling moment through a lookup table T (i, theta), and obtaining total torque T (k +1) of the motor at the next sampling moment through accumulation; when | T_ref(k) If | T (k +1) |, the duty ratio of the excitation phase pulse width modulation control signal is selected from a finite set {0,1/8,1/4,3/8,1/2,5/8,3/4,7/8,1}, and ψ (k +1) ═ ψ (k) + [ U +1 |_dcD-i(k)R]T_sEstimating the phase flux linkage of the excitation phase at the next sampling moment, obtaining the phase current of the excitation phase at the next sampling moment through a lookup table i (psi, theta) by utilizing psi (k +1) and theta (k +1), and obtaining the phase torque T of the excitation phase at the next sampling moment through a lookup table T (i, theta)_i(k + 1); through T_refo(k+1)＝T_ref(k)-T_i(k +1) obtaining the reference torque T of the demagnetizing phase at the next sampling moment_refo(k +1), and obtaining the phase current i of the demagnetized phase at the next sampling moment through a lookup table i (T, theta) and psi (i, theta)_o(k +1) and the phase flux linkage psi_o(k +1) by flux linkage through U_o(k)＝i(k)R+[ψ_o(k+1)-ψ_o(k)]/T_sObtaining the phase voltage U to be applied to the demagnetization phase at the current sampling moment_o(k) Wherein ψ_o(k) Demagnetizing the phase flux linkage of the phase at the current sampling moment and then passing through D_o(k)＝U_o(k)/U_dcObtaining the duty ratio of a demagnetization phase pulse width modulation control signal at the current sampling moment; when | T_ref(k) Selecting duty ratio of demagnetizing phase pulse width modulation control signal from finite set {0, -1/8, -1/4, -3/8, -1/2, -5/8, -3/4, -7/8, -1}, where negative duty ratio indicates that applied phase voltage is negative, by ψ (k +1) ═ ψ (k) + [ U +1) |_dcD-i(k)R]T_sEstimating the phase flux linkage of the demagnetizing phase at the next sampling moment, obtaining the phase current of the demagnetizing phase at the next sampling moment through a lookup table i (psi, theta) by utilizing psi (k +1) and theta (k +1), and obtaining the phase torque T of the demagnetizing phase at the next sampling moment through a lookup table T (i, theta)_o(k + 1); through T_refi(k+1)＝T_ref(k)-T_o(k +1) obtaining a reference for the excitation phase at the next sampling instantTorque T_refi(k +1), and obtaining the phase current i of the excitation phase at the next sampling moment by looking up the tables i (T, theta) and psi (i, theta)_i(k +1) and the phase flux linkage psi_i(k +1) by flux linkage through U_i(k)＝i(k)R+[ψ_i(k+1)-ψ_i(k)]/T_sObtaining the phase voltage U to be applied to the excitation phase at the current sampling moment_i(k) Then through D_i(k)＝U_i(k)/U_dcObtaining the duty ratio of the excitation phase pulse width modulation control signal at the current sampling moment; in both cases, the number in the finite set is selected as the duty cycle of the excitation phase or the demagnetization phase, based on the principle that the cost function J is q_iI+q_e{[(τ/2-θ)/ω-ψ_o/U_dc]/T_s-1-f}²The value of (a) is the minimum, wherein I is the square sum of the phase currents of the excitation phase and the demagnetization phase at the next moment, f is an integer from 1 to 9 and corresponds to 9 duty ratios in the two finite sets, and the larger the absolute value of the duty ratio is, the smaller f is; generating pulse width modulation control signals according to the duty ratios of the excitation phase and the demagnetization phase obtained under the two conditions, and applying the pulse width modulation control signals to the switching tubes of the corresponding phases in the power converter respectively to complete control; when the switched reluctance motor rotates reversely, no matter under the electric working condition or the braking working condition, in a double-phase action area and a demagnetizing phase does not need to enter a complete turn-off state, the control process of the switched reluctance motor is only different from that of the double-phase action area of the forward rotation in the field excitation phase sequence; the phases of the three-phase switched reluctance motor are defined as an A phase, a B phase and a C phase respectively, the excitation phase sequence of forward rotation is A-B-C, and the phase sequence of reverse rotation is A-C-B.

Technical Field

The invention relates to a four-quadrant composite rotating speed control method for a three-phase switched reluctance motor, and belongs to the field of motor control.

Background

The switched reluctance motor becomes one of the choices of various occasions needing to drive the motor by virtue of the characteristics of simple structure, low cost, extremely high reliability and the like, and has good application prospect in the fields of aerospace, general industry, new energy traffic, equipment manufacturing and the like. However, the electromagnetic characteristics of the switched reluctance motor are highly nonlinear due to the special double salient pole structure and the highly saturated magnetic circuit, the control difficulty of the switched reluctance motor is greatly increased, and the advantageous performance of the switched reluctance motor is difficult to be fully exerted by the traditional methods such as angle position control, current chopping control, voltage pulse width modulation control and the like.

In practical applications, the electric drive system is often required to track a dynamic reference speed, which requires the electric machine to have the capability of four-quadrant operation, i.e., to operate in an electric operating condition or a braking operating condition under different steering. At present, the research on the control method of the switched reluctance motor mostly focuses on the suppression of torque fluctuation, and methods such as direct torque control, direct instantaneous torque control, torque distribution function control and the like are developed, however, the research on the control method of four-quadrant operation is still few. In view of the above, the invention discloses a four-quadrant composite rotating speed control method for a three-phase switched reluctance motor, which can realize four-quadrant operation of the motor while inhibiting torque fluctuation, can also consider the efficiency of the motor, and has important significance for four-quadrant rotating speed servo application of the switched reluctance motor.

Disclosure of Invention

The invention discloses a four-quadrant composite rotating speed control method of a three-phase switch reluctance motor, which is characterized in that a model prediction control method is improved and combined with a dead-beat control method, and then the model prediction control method is expanded to a brake operation working condition, so that the four-quadrant rotating speed control of the three-phase switch reluctance motor is realized while torque fluctuation is inhibited, and the method is realized by the following steps:

the method comprises the following steps: judging the action area and the single-phase action area of the phase winding of the switched reluctance motor, and turning to the second step, the double-phase action area and the third step;

step two: in a positive rotation single-phase action area, no matter under an electric working condition or a braking working condition, a dead beat control method is adopted; by psi (k +1) ═ psi (k) + [ U_dcD-i(k)R]T_sEstimating the flux linkage of two demagnetized phases at the next sampling time, wherein psi (k +1) is the flux linkage of the phase at the next sampling time, psi (k) is the flux linkage of the phase at the current sampling time, and U_dcIs the bus voltage, D is the duty cycle, i (k) is the phase current at the current sampling time, R is the phase resistance, T_sIs a sampling period; by θ (k +1) ═ θ (k) + ω T_sEstimating the rotor positions of two demagnetizing phases at the next sampling moment, wherein theta (k +1) is the rotor position at the next sampling moment, theta (k) is the rotor position at the current sampling moment, and omega is the rotating speed of the motor; and obtaining phase currents of the two demagnetizing phases at the next sampling moment through a lookup table i (psi, theta) by utilizing the flux linkage and the rotor position of the two demagnetizing phases at the next sampling moment, and obtaining phase torque T of the two demagnetizing phases at the next sampling moment through a lookup table T (i, theta)_o1(k +1) and T_o2(k + 1); through T_refi(k+1)＝T_ref(k)-T_o1(k+1)-T_o2(k +1) calculating a reference torque for the excitation phase at the next sampling instant, where T_refi(k +1) is the reference torque of the excitation phase at the next sampling instant, T_ref(k) The total reference torque of the current sampling moment obtained by the rotating speed ring; by T_refi(k +1), obtaining the reference current of the excitation phase at the next sampling moment through a lookup table i (T, theta), and obtaining the reference flux linkage psi of the excitation phase at the next sampling moment through a lookup table psi (i, theta)_refi(k + 1); by making use of psi_refi(k +1) by U_i(k)＝i(k)R+[ψ_refi(k+1)-ψ_i(k)]/T_sObtaining the phase voltage U to be applied to the excitation phase at the current sampling moment_i(k) Wherein ψ_i(k) The phase flux linkage of the excitation phase for the current sampling moment and then through D_i(k)＝U_i(k)/U_dcObtaining the duty ratio D of the excitation phase pulse width modulation control signal at the current sampling moment_i(k) Applying the pulse width modulation control signal to a switch tube corresponding to excitation in the power converter to complete control; for the single-phase action zone of the reverse rotation, no matter the electric working condition or the braking working condition, compared with the single-phase action zone of the forward rotation, the control process of the single-phase action zone of the reverse rotation only has the difference of an excitation phase sequence; defining phases of a three-phase switched reluctance motor as an A phase, a B phase and a C phase respectively, wherein the excitation phase sequence of positive rotation is A-B-C, and the phase sequence of reverse rotation is A-C-B;

step three: in the biphasic region, by (tau/2-theta)_o) Omega and psi_o/U_dcThe magnitude relation between the two determines whether the demagnetizing phase needs to enter a complete turn-off state, wherein tau is the polar distance of the rotor, and theta_oFor demagnetising the rotor position, psi_oIs a demagnetized phase flux linkage; when (tau/2-theta)_o)/ω＞ψ_o/U_dcWhen the demagnetization phase does not need to enter a complete turn-off state, the step four is carried out, and when the step is (tau/2-theta)_o)/ω≤ψ_o/U_dcWhen the demagnetization phase needs to enter a complete turn-off state, a dead-beat control method of a single-phase action area is adopted, and the step II is carried out;

step four: the switched reluctance motor rotates forwards, and a model prediction control method is adopted in a double-phase action area no matter under the electric working condition or the braking working condition and when a demagnetization phase does not need to enter a complete turn-off state; assuming that the flux linkage ψ (k +1) of each phase at the next sampling time is equal to the flux linkage ψ (k) at the current sampling time, by θ (k +1) ═ θ (k) + ω T_sEstimating the rotor position of each phase at the next sampling moment; obtaining phase current of each phase at the next sampling moment through a lookup table i (psi, theta) by utilizing psi (k +1) and theta (k +1), obtaining phase torque of each phase at the next sampling moment through a lookup table T (i, theta), and obtaining total torque T (k +1) of the motor at the next sampling moment through accumulation; when | T_ref(k) If | T (k +1) |, the duty ratio of the excitation phase pulse width modulation control signal is selected from a finite set {0,1/8,1/4,3/8,1/2,5/8,3/4,7/8,1}, and ψ (k +1) ═ ψ (k) + [ U +1 |_dcD-i(k)R]T_sEstimating the phase flux linkage of the excitation phase at the next sampling moment, obtaining the phase current of the excitation phase at the next sampling moment through a lookup table i (psi, theta) by utilizing psi (k +1) and theta (k +1), and obtaining the phase current of the excitation phase at the next sampling moment through a lookup table T (i, theta)Torque T_i(k + 1); through T_refo(k+1)＝T_ref(k)-T_i(k +1) obtaining the reference torque T of the demagnetizing phase at the next sampling moment_refo(k +1), and obtaining the phase current i of the demagnetized phase at the next sampling moment through a lookup table i (T, theta) and psi (i, theta)_o(k +1) and the phase flux linkage psi_o(k +1) by flux linkage through U_o(k)＝i(k)R+[ψ_o(k+1)-ψ_o(k)]/T_sObtaining the phase voltage U to be applied to the demagnetization phase at the current sampling moment_o(k) Wherein ψ_o(k) Demagnetizing the phase flux linkage of the phase at the current sampling moment and then passing through D_o(k)＝U_o(k)/U_dcObtaining the duty ratio of a demagnetization phase pulse width modulation control signal at the current sampling moment; when | T_ref(k) Selecting duty ratio of demagnetizing phase pulse width modulation control signal from finite set {0, -1/8, -1/4, -3/8, -1/2, -5/8, -3/4, -7/8, -1}, where negative duty ratio indicates that applied phase voltage is negative, by ψ (k +1) ═ ψ (k) + [ U +1) |_dcD-i(k)R]T_sEstimating the phase flux linkage of the demagnetizing phase at the next sampling moment, obtaining the phase current of the demagnetizing phase at the next sampling moment through a lookup table i (psi, theta) by utilizing psi (k +1) and theta (k +1), and obtaining the phase torque T of the demagnetizing phase at the next sampling moment through a lookup table T (i, theta)_o(k + 1); through T_refi(k+1)＝T_ref(k)-T_o(k +1) obtaining the reference torque T of the excitation phase at the next sampling moment_refi(k +1), and obtaining the phase current i of the excitation phase at the next sampling moment by looking up the tables i (T, theta) and psi (i, theta)_i(k +1) and the phase flux linkage psi_i(k +1) by flux linkage through U_i(k)＝i(k)R+[ψ_i(k+1)-ψ_i(k)]/T_sObtaining the phase voltage U to be applied to the excitation phase at the current sampling moment_i(k) Then through D_i(k)＝U_i(k)/U_dcObtaining the duty ratio of the excitation phase pulse width modulation control signal at the current sampling moment; in both cases, the number in the finite set is selected as the duty cycle of the excitation phase or the demagnetization phase, based on the principle that the cost function J is q_iI+q_e{[(τ/2-θ)/ω-ψ_o/U_dc]/T_s-1-f}²Has the smallest value, wherein I is the next momentF is an integer from 1 to 9, and corresponds to 9 duty ratios in the two finite sets, wherein the larger the absolute value of the duty ratio is, the smaller f is; generating pulse width modulation control signals according to the duty ratios of the excitation phase and the demagnetization phase obtained under the two conditions, and applying the pulse width modulation control signals to the switching tubes of the corresponding phases in the power converter respectively to complete control; when the switched reluctance motor rotates reversely, no matter under the electric working condition or the braking working condition, in a double-phase action area and a demagnetizing phase does not need to enter a complete turn-off state, the control process of the switched reluctance motor is only different from that of the double-phase action area of the forward rotation in the field excitation phase sequence; the phases of the three-phase switched reluctance motor are defined as an A phase, a B phase and a C phase respectively, the excitation phase sequence of forward rotation is A-B-C, and the phase sequence of reverse rotation is A-C-B.

Drawings

Fig. 1 is a flow chart of a four-quadrant composite rotating speed control method of a switched reluctance motor.

Fig. 2 shows a judgment basis of the action area of the phase winding in the forward electromotive state of the three-phase 12/8-pole switched reluctance motor.

Detailed Description

The technical scheme of the invention is explained in detail in the following by combining the drawings and specific examples. The motor used in the embodiment is a three-phase 12/8-pole switched reluctance motor, and works in a forward electric state, and the implementation flow of the four-quadrant composite rotating speed control method disclosed by the invention on the motor is shown in fig. 1, and the specific steps are as follows:

the method comprises the following steps: judging the action area and the single-phase action area of the phase winding of the switched reluctance motor, and turning to the second step, the double-phase action area and the third step; for the three-phase 12/8 pole switched reluctance motor used in the example, the phase winding active area is determined according to the diagram of fig. 2 in the forward electromotive state.

Step two: adopting a dead beat control method to convert psi (k +1) into psi (k) + [ U_dcD-i(k)R]T_sEstimating flux linkage of two demagnetized phases at the next sampling time by using theta (k +1) as theta (k) + omega T_sEstimating the rotor positions of two demagnetizing phases at the next sampling moment; and obtaining the next sampling moment through a lookup table i (psi, theta) by utilizing the flux linkage and the rotor position of two demagnetizing phases at the next sampling momentThe phase currents of the two demagnetizing phases are obtained, and the phase torques T of the two demagnetizing phases at the next sampling moment are obtained through a lookup table T (i, theta)_o1(k +1) and T_o2(k + 1); through T_refi(k+1)＝T_ref(k)-T_o1(k+1)-T_o2(k +1) calculating the reference torque T of the excitation phase at the next sampling moment_refi(k + 1); by T_refi(k +1), obtaining the reference current of the excitation phase at the next sampling moment through a lookup table i (T, theta), and obtaining the reference flux linkage psi of the excitation phase at the next sampling moment through a lookup table psi (i, theta)_refi(k + 1); by making use of psi_refi(k +1) by U_i(k)＝i(k)R+[ψ_refi(k+1)-ψ_i(k)]/T_sObtaining the phase voltage U to be applied to the excitation phase at the current sampling moment_i(k) Then through D_i(k)＝U_i(k)/U_dcObtaining the duty ratio D of the excitation phase pulse width modulation control signal at the current sampling moment_i(k) Applying the pulse width modulation control signal to a switch tube corresponding to excitation in the power converter to complete control;

step three: in the biphasic region, by (tau/2-theta)_o) Omega and psi_o/U_dcThe magnitude relation between the two phases determines whether the demagnetizing phase needs to enter a complete turn-off state; for the three-phase 12/8 pole switched reluctance machine used in the example, the rotor pole pitch was 45 °, when (22.5 ° - θ)_o)/ω＞ψ_o/U_dcWhen the demagnetization phase does not need to enter a complete turn-off state, the step four is carried out, and when (22.5-theta) is carried out_o)/ω≤ψ_o/U_dcWhen the demagnetization phase needs to enter a complete turn-off state, a dead-beat control method of a single-phase action area is adopted, and the step II is carried out;

step four: by adopting the model predictive control method, assuming that the flux linkage ψ (k +1) of each phase at the next sampling time is equal to the flux linkage ψ (k) at the current sampling time, by changing θ (k +1) to θ (k) + ω T_sEstimating the rotor position of each phase at the next sampling moment; obtaining phase current of each phase at the next sampling moment through a lookup table i (psi, theta) by utilizing psi (k +1) and theta (k +1), obtaining phase torque of each phase at the next sampling moment through a lookup table T (i, theta), and obtaining total torque T (k +1) of the motor at the next sampling moment through accumulation; when | T_ref(k) If | T (k +1) |, the duty ratio of the excitation phase pulse width modulation control signal is selected from a finite set {0,1/8,1/4,3/8,1/2,5/8,3/4,7/8,1}, and ψ (k +1) ═ ψ (k) + [ U +1 |_dcD-i(k)R]T_sEstimating the phase flux linkage of the excitation phase at the next sampling moment, obtaining the phase current of the excitation phase at the next sampling moment through a lookup table i (psi, theta) by utilizing psi (k +1) and theta (k +1), and obtaining the phase torque T of the excitation phase at the next sampling moment through a lookup table T (i, theta)_i(k + 1); through T_refo(k+1)＝T_ref(k)-T_i(k +1) obtaining the reference torque T of the demagnetizing phase at the next sampling moment_refo(k +1), and obtaining the phase current i of the demagnetized phase at the next sampling moment through a lookup table i (T, theta) and psi (i, theta)_o(k +1) and the phase flux linkage psi_o(k +1) by flux linkage through U_o(k)＝i(k)R+[ψ_o(k+1)-ψ_o(k)]/T_sObtaining the phase voltage U to be applied to the demagnetization phase at the current sampling moment_o(k) Then through D_o(k)＝U_o(k)/U_dcObtaining the duty ratio of a demagnetization phase pulse width modulation control signal at the current sampling moment; when | T_ref(k) When | ≦ T (k +1) |, the duty ratio of the demagnetization phase pulse width modulation control signal is selected from the finite set {0, -1/8, -1/4, -3/8, -1/2, -5/8, -3/4, -7/8, -1}, and the duty ratio is determined by ψ (k +1) ═ ψ (k) + [ U ], (k) |_dcD-i(k)R]T_sEstimating the phase flux linkage of the demagnetizing phase at the next sampling moment, obtaining the phase current of the demagnetizing phase at the next sampling moment through a lookup table i (psi, theta) by utilizing psi (k +1) and theta (k +1), and obtaining the phase torque T of the demagnetizing phase at the next sampling moment through a lookup table T (i, theta)_o(k + 1); through T_refi(k+1)＝T_ref(k)-T_o(k +1) obtaining the reference torque T of the excitation phase at the next sampling moment_refi(k +1), and obtaining the phase current i of the excitation phase at the next sampling moment by looking up the tables i (T, theta) and psi (i, theta)_i(k +1) and the phase flux linkage psi_i(k +1) by flux linkage through U_i(k)＝i(k)R+[ψ_i(k+1)-ψ_i(k)]/T_sObtaining the phase voltage U to be applied to the excitation phase at the current sampling moment_i(k) Then through D_i(k)＝U_i(k)/U_dcObtaining the duty ratio of the excitation phase pulse width modulation control signal at the current sampling moment; to be provided withIn the two cases, the different numbers in the finite set are selected as the duty ratio to compare, so that the cost function J is q_iI+q_e{[(τ/2-θ)/ω-ψ_o/U_dc]/T_s-1-f}²The minimum value of (A) is the optimal solution; and generating pulse width modulation control signals according to the acquired duty ratio, and applying the pulse width modulation control signals to corresponding switch tubes in the power converter respectively to finish control.