阅读说明：本技术 一种基于电流预测的适用于异步电机控制的死区补偿方法 (Dead zone compensation method suitable for asynchronous motor control based on current prediction ) 是由 张涛 张利娟 王泉策 李�东 王雷 杨璐 王喜乐 于 2021-09-25 设计创作，主要内容包括：本发明属于电机控制的死区补偿技术领域,具体为一种基于电流预测的适用于异步电机控制的死区补偿方法,解决了背景技术中的技术问题,其包括低速区死区补偿方法和高速区死区补偿方法,低速区死区补偿方法分为低速区电流预测和死区补偿两步,高速区死区补偿方法分为高速区电流预测和死区补偿两步。利用坐标变换和异步电机等效模型相结合的方式对电机电流进行预测,通过预测电机电流来进行死区补偿,通过本发明所述的死区补偿方法进行控制后,避免了本拍采样电流进行死区补偿时存在延迟的情况,能够准确检测电流过流点,能准确进行死区补偿；本发明所述方法考虑了开关器件IGBT的导通压降和开关管的开通关断延迟,进一步确保死区补偿准确性。(The invention belongs to the technical field of dead zone compensation of motor control, in particular to a dead zone compensation method based on current prediction and suitable for asynchronous motor control, which solves the technical problems in the background art and comprises a low-speed zone dead zone compensation method and a high-speed zone dead zone compensation method, wherein the low-speed zone dead zone compensation method comprises two steps of low-speed zone current prediction and dead zone compensation, and the high-speed zone dead zone compensation method comprises two steps of high-speed zone current prediction and dead zone compensation. The motor current is predicted by combining the coordinate transformation and the asynchronous motor equivalent model, dead zone compensation is carried out by predicting the motor current, and after the dead zone compensation method is used for controlling, the delay condition existing when dead zone compensation is carried out on the current sampled by the beat is avoided, the overcurrent point can be accurately detected, and the dead zone compensation can be accurately carried out; the method of the invention considers the conduction voltage drop of the switch device IGBT and the on-off delay of the switch tube, and further ensures the accuracy of dead zone compensation.)

1. A dead zone compensation method suitable for asynchronous motor control based on current prediction is characterized by comprising a low-speed zone dead zone compensation method and a high-speed zone dead zone compensation method;

i, the low-speed zone dead zone compensation method is completed in two steps:

the first step is as follows: low speed current prediction by dq axis current setpointThe three-phase current of the asynchronous motor is predicted, the calculation process is shown as the formula (1) to the formula (3), firstly, the angle phi required for coordinate transformation is calculated according to the formula (1),

φ＝θ+w_e*T_s (1)，

in the formula (1), theta represents the synchronous rotation angle of the racket; w is a_eRepresenting the electrical angular velocity of the motor; t is_sRepresents a sampling time; phi represents the synchronous rotation angle of the next beat; then setting the dq axis current to a given valueObtaining i by inverse Park coordinate transformation_{α_pre}、i_{β_pre}The calculation process is shown as the formula (2),

in the formula (2), i_{α_pre}、i_{β_pre}Respectively representing alpha and beta axis predicted current values; finally, obtaining a predicted value i of the current of the three-phase motor under a static coordinate system through 2/3 transformation_{A_pre}、i_{B_pre}And i_{C_pre}The calculation process is shown as the formula (3),

secondly, performing dead zone compensation on the predicted value of the current of the three-phase motor; in which the current of the A-phase motor is predicted to be i_{A_pre}The dead zone compensation method comprises the following steps: if i_{A_pre}>0, when upper tube V1 of arm A is on and lower tube V2 is off, the rising edge of upper tube V1 and the falling edge of lower tube V2 are setAre all advanced by T_{_dead}Time; if i_{A_pre}>0, when the upper tube V1 of the arm A is turned off and the lower tube V2 is turned on, the upper tube V1 and the lower tube V2 are not processed; if i_{A_pre}<0, when the upper tube V1 of the arm A is switched on and the lower tube V2 is switched off, the upper tube V1 and the lower tube V2 are not processed; if i_{A_pre}<0, when the upper tube V1 of arm A is turned off and the lower tube V2 is turned on, the rising edge of the upper tube V1 and the falling edge of the lower tube V2 are both advanced by T_{_dead}Time; for B-phase motor current prediction value i_{B_pre}And C phase motor current prediction value i_{C_pre}The dead zone compensation method is equal to the predicted value i of the current of the A-phase motor_{A_pre}The dead zone compensation method is the same;

II, the dead zone compensation method of the high-speed zone is completed in two steps:

the first step is as follows: predicting high-speed current, calculating the angle phi required by coordinate transformation according to formula (1), and predicting the weak magnetic current value i_{d_pre}And torque current predicted value i_{q_pre}Obtaining i by inverse Park coordinate transformation_{α_pre}、i_{β_pre}And finally obtaining a predicted value i of the current of the three-phase motor under the static coordinate system through 2/3 transformation in the calculation process shown as the formula (2)_{A_pre}、i_{B_pre}And i_{C_pre}The calculation process is shown as the formula (3);

wherein the weak magnetic current is predicted value i_{d_pre}And torque current predicted value i_{q_pre}The calculation process of (2) is as follows: according to the given value of the T-type equivalent circuit of the asynchronous motor to the dq axis currentThe dq-axis voltage equation of the asynchronous motor is predicted as shown in the formula (4) and the formula (5):

in the formula of U_d、U_qRespectively representing d and q axis voltages, and lambda is a flux linkage; r_s、L_s、L_m、L_rThe asynchronous motor comprises a stator resistor, a stator inductor, a mutual inductor and a rotor inductor of the asynchronous motor respectively;rate of change of field current through i_dAnd i_{d_pre}Obtaining a torque current change rate calculation formula (7) as shown in formula (6) and a torque current change rate calculation formula (7),

in the formula i_{d_pre}Representing the predicted value of the weak magnetic current; i.e. i_{q_pre}Representing a torque current predicted value; i.e. i_dRepresenting d-axis intrinsic beat excitation current, i_qRepresenting the q-axis local beat excitation current; formula (6) and formula (7) are taken into formula (4) and formula (5), respectively, to obtain:

i is obtained by the formulae (8) and (9)_{d_pre}And i_{q_pre}；

The second step is that: performing dead zone compensation on the predicted value of the current of the three-phase motor; the dead zone compensation method of the high-speed zone is the same as the dead zone compensation method of the three-phase motor current predicted value in the low-speed zone.

Technical Field

The invention belongs to the technical field of dead zone compensation of motor control, relates to an asynchronous motor, and particularly relates to a dead zone compensation method suitable for controlling the asynchronous motor based on current prediction.

Background

The inverter main circuit topology of the electric locomotive generally adopts a bridge circuit structure, as shown in fig. 1. The switching devices of the bridge arms adopt high-voltage-grade IGBTs, the IGBTs are not ideal devices and have turn-on and turn-off delays, so that certain dead time needs to be added into driving pulses of upper and lower IGBTs of the same bridge arm to ensure the reliable work of the switching devices, the turn-on and turn-off delays of the high-voltage-grade IGBTs are more serious, so that longer dead time needs to be added into the driving pulses of the upper and lower tubes to ensure the reliable work of the devices, the added dead time can cause the problem that the actual output voltage waveform is inconsistent with the theoretical voltage waveform, thereby causing the dead time effect, the dead time effect is analyzed by taking the A bridge arm as an example, the V1 and the V2 correspond to the upper and lower tubes of the A bridge arm, the V3 and the V4 correspond to the upper and lower tubes of the B bridge arm, the V5 and the V6 correspond to the upper and lower tubes of the C bridge arm, when the phase current of the A bridge arm is greater than zero, the actually output waveform of the inverter lacks a dead time pulse voltage, when the phase current A is less than zero, the waveform actually output by the inverter is increased by a dead zone pulse voltage compared with the theoretical value, so that the actual output voltage waveform is inconsistent with the theoretical waveform, a dead zone effect is generated, and the normal operation of the motor is influenced. The dead zone effect can generate harmonic voltage and current with different frequencies, so that the operation of the motor is influenced, and particularly, the dead zone effect is worse under the working condition of low speed and light load of the variable frequency speed control system, so that the dead zone needs to be compensated.

Dead-time compensation is typically performed in the prior art by determining the polarity of the load current, adding dead-time to the drive pulse. The method mainly has two problems: firstly, due to the digital control mode adopted by the inverter, delay can be generated in digital control, and the next beat of the calculation result of the beat can take effect, so that dead zone compensation performed according to the sampled current of the beat has delay, the current flowing point can not be accurately detected, and the dead zone compensation can not be accurately performed; secondly, the conduction voltage drop of the IGBT and the turn-on and turn-off delay of the switching tube are not considered, so that the dead zone compensation of the method is inaccurate.

Disclosure of Invention

The invention aims to solve the technical problem that dead zone compensation effect of a zero-crossing point accessory is poor due to the fact that a digital controller adopted by a frequency converter has certain delay and a calculation result of a beat is updated only when the next beat is carried out in a method of adding dead zone time to a driving pulse to carry out dead zone compensation by judging the polarity of load current, and provides a dead zone compensation method suitable for asynchronous motor control based on current prediction.

The technical means for solving the technical problems of the invention is as follows: a dead zone compensation method suitable for asynchronous motor control based on current prediction comprises a low-speed zone dead zone compensation method and a high-speed zone dead zone compensation method;

i, the low-speed zone dead zone compensation method is completed in two steps:

the first step is as follows: low speed current prediction by dq axis current setpointThe three-phase current of the asynchronous motor is predicted, the calculation process is shown as the formula (1) to the formula (3), firstly, the angle phi required for coordinate transformation is calculated according to the formula (1),

φ＝θ+w_e*T_s (1)，

in the formula (1), theta represents the synchronous rotation angle of the racket; w is a_eRepresenting the electrical angular velocity of the motor; t is_sRepresents a sampling time; phi represents the synchronous rotation angle of the next beat; then setting the dq axis current to a given valueObtaining i by inverse Park coordinate transformation_{α_pre}、i_{β_pre}The calculation process is shown as the formula (2),

in the formula (2), i_{α_pre}、i_{β_pre}Respectively representing alpha and beta axis predicted current values; finally, obtaining a predicted value i of the current of the three-phase motor under a static coordinate system through 2/3 transformation_{A_pre}、i_{B_pre}And i_{C_pre}The calculation process is shown as the formula (3),

secondly, performing dead zone compensation on the predicted value of the current of the three-phase motor; in which the current of the A-phase motor is predicted to be i_{A_pre}The dead zone compensation method comprises the following steps: if i_{A_pre}>0, when the upper tube V1 of arm A is switched on and the lower tube V2 is switched off, the rising edge of the upper tube V1 and the falling edge of the lower tube V2 are both advanced by T_{_dead}Time; if i_{A_pre}>0, when the upper tube V1 of the arm A is turned off and the lower tube V2 is turned on, the upper tube V1 and the lower tube V2 are not processed; if i_{A_pre}<0, when the upper tube V1 of the arm A is switched on and the lower tube V2 is switched off, the upper tube V1 and the lower tube V2 are not processed; if i_{A_pre}<0, when the upper tube V1 of arm A is turned off and the lower tube V2 is turned on, the rising edge of the upper tube V1 and the falling edge of the lower tube V2 are both advanced by T_{_dead}Time; for B-phase motor current prediction value i_{B_pre}And C phase motor current prediction value i_{C_pre}The dead zone compensation method is equal to the predicted value i of the current of the A-phase motor_{A_pre}The dead zone compensation method is the same;

II, the dead zone compensation method of the high-speed zone is completed in two steps:

the first step is as follows: predicting high-speed current, calculating the angle phi required by coordinate transformation according to formula (1), and predicting the weak magnetic current value i_{d_pre}And torque current predicted value i_{q_pre}Obtaining i by inverse Park coordinate transformation_{α_pre}、i_{β_pre}And finally obtaining a predicted value i of the current of the three-phase motor under the static coordinate system through 2/3 transformation in the calculation process shown as the formula (2)_{A_pre}、i_{B_pre}And i_{C_pre}The calculation process is shown as the formula (3);

wherein the weak magnetic current is predicted value i_{d_pre}And torque current predicted value i_{q_pre}The calculation process of (2) is as follows: according to the given value of the T-type equivalent circuit of the asynchronous motor to the dq axis currentThe dq-axis voltage equation of the asynchronous motor is predicted as shown in the formula (4) and the formula (5):

in the formula of U_d、U_qRespectively representing d and q axis voltages, and lambda is a flux linkage; r_s、L_s、L_m、L_rThe asynchronous motor comprises a stator resistor, a stator inductor, a mutual inductor and a rotor inductor of the asynchronous motor respectively;rate of change of field current through i_dAnd i_{d_pre}Obtaining a torque current change rate calculation formula (7) as shown in formula (6) and a torque current change rate calculation formula (7),

in the formula i_{d_pre}Representing the predicted value of the weak magnetic current; i.e. i_{q_pre}RepresentsA predicted value of torque current; i.e. i_dRepresenting d-axis intrinsic beat excitation current, i_qRepresenting the q-axis local beat excitation current; formula (6) and formula (7) are taken into formula (4) and formula (5), respectively, to obtain:

i is obtained by the formulae (8) and (9)_{d_pre}And i_{q_pre}；

The second step is that: performing dead zone compensation on the predicted value of the current of the three-phase motor; the dead zone compensation method of the high-speed zone is the same as the dead zone compensation method of the three-phase motor current predicted value in the low-speed zone.

The invention has the beneficial effects that: the motor current is predicted by combining the coordinate transformation and the asynchronous motor equivalent model, dead zone compensation is carried out by predicting the motor current, and after the dead zone compensation method is used for controlling, the delay condition existing when dead zone compensation is carried out on the current sampled by the beat is avoided, the overcurrent point can be accurately detected, and the dead zone compensation can be accurately carried out; the method of the invention considers the conduction voltage drop of the switch device IGBT and the on-off delay of the switch tube, and further ensures the accuracy of dead zone compensation.

Drawings

Fig. 1 is a main circuit diagram of a three-phase inverter in the background art.

Fig. 2 is a vector control block diagram of a low-speed stage of a three-phase inverter, wherein a dashed box is a control block diagram of the low-speed zone dead zone compensation method according to the present invention.

FIG. 3 shows predicted values i of currents of A-phase motors of three-phase inverters_{A_pre}>0, wherein a waveform diagram of the dead zone compensation process when the upper tube V1 of the A-phase arm is conducted and the lower tube V2 is turned off (a) is a three-phase inverter A-phase arm topological structure, b) is a theoretical waveform diagram, c) is a waveform diagram after dead zone compensation is carried out, d) is a dead zone diagram that the waveform of c) passes through an svpwm generatorWaveform after module processing).

FIG. 4 shows predicted values i of currents of A-phase motors of three-phase inverters_{A_pre}>0, the waveform diagram of the dead zone compensation process when the upper tube V1 of the A-arm is turned off and the lower tube V2 is turned on (wherein a) is a three-phase inverter A-phase arm topological structure, b) is a theoretical waveform diagram, c) is a waveform diagram after dead zone compensation is carried out, and d) is a waveform diagram after the waveform of c) is processed by a dead zone module of an svpwm generator).

FIG. 5 shows predicted values i of currents of A-phase motors of three-phase inverters_{A_pre}<0, wherein a waveform diagram of the dead zone compensation process when the upper tube V1 of the A-arm is conducted and the lower tube V2 is turned off (a) is a three-phase inverter A-phase arm topological structure, b) is a theoretical waveform diagram, c) is a waveform diagram after dead zone compensation is carried out, and d) is a waveform diagram after the waveform of c) is processed by a dead zone module of the svpwm generator).

FIG. 6 shows predicted values i of currents of A-phase motors of three-phase inverters_{A_pre}<0, the waveform diagram of the dead zone compensation process when the upper tube V1 of the A-arm is turned off and the lower tube V2 is turned on (wherein a) is a three-phase inverter A-phase arm topological structure, b) is a theoretical waveform diagram, c) is a waveform diagram after dead zone compensation is carried out, and d) is a waveform diagram after the waveform of c) is processed by a dead zone module of an svpwm generator).

Fig. 7 is a vector control block diagram of a high-speed stage of a three-phase inverter, wherein a dashed box is a control block diagram of the high-speed zone dead zone compensation method according to the present invention.

Detailed Description

Referring to fig. 1 to 7, a dead-time compensation method for asynchronous motor control based on current prediction according to the present invention will be described in detail.

A dead zone compensation method suitable for asynchronous motor control based on current prediction comprises a low-speed zone dead zone compensation method and a high-speed zone dead zone compensation method;

and i, the low-speed zone dead zone compensation method is completed in two steps (when the speed is lower than the rated speed, the low-speed zone), as shown in fig. 2:

the first step is as follows: low speed current prediction by dq axis current setpointThe three-phase current of the asynchronous motor is predicted, the calculation process is shown as the formula (1) to the formula (3), firstly, the angle phi required for coordinate transformation is calculated according to the formula (1),

φ＝θ+w_e*T_s (1)，

in the formula (1), theta represents the synchronous rotation angle of the racket; w is a_eRepresenting the electrical angular velocity of the motor; t is_sRepresents a sampling time; phi represents the synchronous rotation angle of the next beat; then setting the dq axis current to a given valueObtaining i by inverse Park coordinate transformation_{α_pre}、i_{β_pre}The calculation process is shown as the formula (2),

in the formula (2), i_{α_pre}、i_{β_pre}Respectively representing alpha and beta axis predicted current values; finally, obtaining a predicted value i of the current of the three-phase motor under a static coordinate system through 2/3 transformation_{A_pre}、i_{B_pre}And i_{C_pre}The calculation process is shown as the formula (3),

secondly, performing dead zone compensation on the predicted value of the current of the three-phase motor; in which the current of the A-phase motor is predicted to be i_{A_pre}The dead zone compensation method comprises the following steps:

if i_{A_pre}>0, and the upper tube V1 of arm A is conducted and the lower tube V2 is turned off, the topological structure of arm A and the theoretical waveform diagram when the upper tube V1 is conducted and the lower tube V2 is turned off, V) can be known from a) and b) in FIG. 3_AOFor the voltage between the bridge arms AO, the rising edge of the upper tube V1 and the falling edge of the lower tube V2 are both advanced by T_{_dead}The waveform after time, dead zone compensation is shown as c) in FIG. 3, and dead zone compensation is shown as FIG. 2The latter current is supplied to the svpwm generator whose dead-band module continues the processing of the waveform in c), only the rising edge of the upper tube V1 is delayed by T, as can be seen from d) in fig. 3_{_dead}The falling edge of lower tube V2 remains unchanged;

if i_{A_pre}>0, and the upper tube V1 of the arm A is turned off and the lower tube V2 is turned on, from a) and b) in FIG. 4, the topological structure of the arm A and the theoretical waveform diagram when the upper tube V1 is turned off and the lower tube V2 is turned on can be known, and the waveform diagram after dead zone compensation is as shown in c) in FIG. 4 without processing the upper tube V1 and the lower tube V2, and is consistent with the theoretical waveform diagram, as shown in FIG. 2, the current after dead zone compensation is transmitted to the svpwm generator, the dead zone module of the svpwm generator continues processing the waveform in c), and as can be seen from d) in FIG. 4, only the rising edge of the lower tube V2 is delayed by T_{_dead}The falling edge of the upper tube V1 remains unchanged;

if i_{A_pre}<0, when the upper tube V1 of the arm A is conducted and the lower tube V2 is turned off, according to a) and b) in FIG. 5, the topological structure of the arm A and the theoretical waveform diagram when the upper tube V1 is conducted and the lower tube V2 is turned off can be known, and the waveform diagram after dead zone compensation is as shown in c) in FIG. 5 without processing the upper tube V1 and the lower tube V2, and is consistent with the theoretical waveform diagram, as shown in FIG. 2, the current after dead zone compensation is transmitted to the svpwm generator, the dead zone module of the svpwm generator continuously processes the waveform in c), and as can be seen from d) in FIG. 5, only the rising edge of the upper tube V1 is delayed by T_{_dead}The falling edge of lower tube V2 remains unchanged;

if i_{A_pre}<0, when the upper tube V1 of the arm A is turned off and the lower tube V2 is turned on, the topological structure of the arm A and the theoretical waveform diagrams when the upper tube V1 is turned off and the lower tube V2 is turned on can be known from a) and b) in FIG. 6, and the rising edge of the upper tube V1 and the falling edge of the lower tube V2 are both advanced by T_{_dead}The time, dead zone compensated waveform diagram is shown in c) of fig. 6, as shown in fig. 2, the dead zone compensated current is supplied to the svpwm generator, the dead zone module of the svpwm generator processes the waveform in c), and according to d) of fig. 6, only the falling edge of the upper tube V1 is kept unchanged, and the rising edge of the lower tube V2 is delayed by T_{_dead}Time; for B-phase motor current prediction value i_{B_pre}And C phase motor current prediction value i_{C_pre}The dead zone compensation method is equal to the predicted value i of the current of the A-phase motor_{A_pre}The dead zone compensation method is the same;

II, completing the dead zone compensation method of the high-speed zone in two steps (belonging to the high-speed zone above the rated speed), as shown in FIG. 7:

the first step is as follows: predicting high-speed current, calculating the angle phi required by coordinate transformation according to formula (1), and predicting the weak magnetic current value i_{d_pre}And torque current predicted value i_{q_pre}Obtaining i by inverse Park coordinate transformation_{α_pre}、i_{β_pre}And finally obtaining a predicted value i of the current of the three-phase motor under the static coordinate system through 2/3 transformation in the calculation process shown as the formula (2)_{A_pre}、i_{B_pre}And i_{C_pre}The calculation process is shown as the formula (3);

wherein the weak magnetic current is predicted value i_{d_pre}And torque current predicted value i_{q_pre}The calculation process of (2) is as follows: according to the given value of the T-type equivalent circuit of the asynchronous motor to the dq axis currentThe dq-axis voltage equation of the asynchronous motor is predicted as shown in the formula (4) and the formula (5):

in the formula of U_d、U_qRespectively representing d and q axis voltages, and lambda is a flux linkage; r_s、L_s、L_m、L_rThe asynchronous motor comprises a stator resistor, a stator inductor, a mutual inductor and a rotor inductor of the asynchronous motor respectively;rate of change of field current through i_dAnd i_{d_pre}Obtaining a torque current change rate calculation formula (7) as shown in formula (6) and a torque current change rate calculation formula (7),

in the formula i_{d_pre}Representing the predicted value of the weak magnetic current; i.e. i_{q_pre}Representing a torque current predicted value; i.e. i_dRepresenting d-axis intrinsic beat excitation current, i_qRepresenting the q-axis local beat excitation current; formula (6) and formula (7) are taken into formula (4) and formula (5), respectively, to obtain:

i is obtained by the formulae (8) and (9)_{d_pre}And i_{q_pre}；

The second step is that: performing dead zone compensation on the predicted value of the current of the three-phase motor; the dead zone compensation method of the high-speed zone is the same as the dead zone compensation method of the three-phase motor current predicted value in the low-speed zone.

While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.