阅读说明：本技术 一种车用永磁同步电机矢量弱磁控制方法 (Vector flux weakening control method for vehicle permanent magnet synchronous motor ) 是由 李静 及非凡 陈雨薇 于 2021-03-22 设计创作，主要内容包括：本发明公开了一种车用永磁同步电机矢量弱磁控制方法,该方法包括电流闭环调节模块、调制比偏差计算模块、电流指令角度补偿模块、电流角度预设模块、电流指令角度限制比较器和电流给定矢量修正模块。本发明调节方向永远是弱磁向,不会出现反复调节造成的失稳；引入dq电流同时修正,可以将抗电压饱和的压力分摊至dq电流,避免因单轴电流调节过多而导致输出转矩偏差过大；在保证驱动系统安全的同时,尽可能减小弱磁控制环节对驱动系统输出转矩的影响。(The invention discloses a vehicle permanent magnet synchronous motor vector flux weakening control method which comprises a current closed loop adjusting module, a modulation ratio deviation calculating module, a current instruction angle compensating module, a current angle presetting module, a current instruction angle limiting comparator and a current given vector correcting module. The adjusting direction of the invention is always the weak magnetic direction, so that the instability caused by repeated adjustment can not occur; the dq current is introduced and corrected simultaneously, so that the voltage saturation resistant pressure can be distributed to the dq current, and overlarge output torque deviation caused by excessive single-shaft current adjustment is avoided; the influence of the flux weakening control link on the output torque of the driving system is reduced as much as possible while the safety of the driving system is ensured.)

1. A vehicle permanent magnet synchronous motor vector flux weakening control method is characterized by comprising a current closed loop adjusting module, a modulation ratio deviation calculating module, a current instruction angle compensating module, a current angle presetting module, a current instruction angle limiting comparator and a current given vector correcting module;

the input of the current closed-loop regulating module is a dq current instruction output by the current given vector correcting module, and the dq current instruction is output after passing through the proportional-integral controller;

the input of the modulation ratio deviation calculation module is a dq voltage command output by the current closed-loop regulation module, and the desired modulation ratio is obtained through square and evolutionMI _ref Then, the maximum modulation ratio of the control system to the expected maximum modulation ratioMI _max Making difference, making low-pass filter, and outputting modulation ratio deviation deltaMI；

The input of the current instruction angle compensation module is the modulation ratio deviation output by the modulation ratio deviation calculation module, and the correction angle is output after the modulation ratio deviation passes through the proportional-integral compensator;

the current angle presetting module is used for presetting a current angle;

the current instruction angle limiting comparator is used for limiting the current angle after the angle compensation is corrected and output by the current instruction angle compensation module to be above the current angle preset by the current angle presetting module;

the current given vector correction module is used for calculating a dq current instruction after flux weakening control based on a current angle preset by the current angle preset module.

2. The vehicle PMSM vector flux weakening control method according to claim 1, characterized in that in the current closed loop regulation module, dq current command i is used_dref、i_qrefAnd the deviation of the feedback of the dq current is respectively obtained by a proportional-integral controller to obtain a dq voltage instruction.

3. The vehicle PMSM vector flux weakening control method according to claim 2, wherein in said modulation ratio deviation calculating module,MI _max andMI _ref delta difference ofMI ₀Comprises the following steps:

△MI ₀=MI _ref - MI _max

wherein the content of the first and second substances,v _{d_ref} 、v _{q_ref} in order to be a dq voltage command,V _dc is the bus voltage.

4. The vehicle permanent magnet synchronous motor vector flux weakening control method according to claim 3, wherein in said current command angle compensation module, a correction angle Δ θ:

wherein the content of the first and second substances,k _p 、k _i the proportional coefficient and the integral coefficient of the proportional-integral compensator.

5. The vehicle permanent magnet synchronous motor vector flux-weakening control method according to claim 4, wherein the current angle presetting module limits the orientation of the motor by drawing a maximum torque current ratio (MTPA) current angle curve, and presets the current angle as theta _pre 。

6. The vehicle permanent magnet synchronous motor vector flux weakening control method according to claim 5, wherein said current command angle limitation comparator is configured to limit a current angle to:

θ+△θ≥θ _pre

where θ is the current angle before field weakening control.

7. The vector flux-weakening control method for the permanent magnet synchronous motor for the vehicle as claimed in claim 6, wherein in said current given vector correction module, the dq current command is calculatedi _dref 、i _qref ：

Therein,. mu.giAnd | is the current magnitude before the field weakening control.

Technical Field

The invention belongs to the field of permanent magnet synchronous motor control, and particularly relates to a vehicle permanent magnet synchronous motor vector flux weakening control method.

Background

In a control system of an embedded permanent magnet synchronous motor (IPMSM) for a vehicle, because the IPMSM which is a controlled object in an actual application scene inevitably changes, a control parameter which is solidified in advance in a control program is invalid, so that the voltage saturation is caused by insufficient flux weakening of the motor during high-speed operation, and the stability of a motor driving system is endangered.

The embedded permanent magnet synchronous motor has the characteristics of high power density, wide operating range and high efficiency, and is widely used for a driving motor of an electric automobile; the torque equation is as follows:

（1）

wherein the content of the first and second substances,is the electromagnetic torque of the motor;the number of the magnetic pole pairs of the motor is counted;is rotor permanent magnet flux;is the q-axis current, and is,is the d-axis current;is a d-axis inductor;is a q-axis inductor; during the normal driving of the IPMSM,>0,>0,<0,<。

from the above equation, the torque and the current are in positive correlation, but different dq-axis current combinations correspond to different torques, and each fixed current amplitude has a specific set of dq current combinations to enable the motor to output the maximum torque at the current. Dq-axis inductance after current is greater than a certain range due to magnetic field saturation、The current can be changed, and the change range can reach as much as 200 percent at most. The variation of these parameters makes it difficult or even impossible to solve online for the optimal dq current combination at each current. Therefore, in the vehicle motor control, the optimal current combination corresponding to each torque is generally obtained through testing and calibration by an experimental method. The line connecting all such current combinations in the full torque range is called the maximum torque to current ratio (MTPA) curve of the IPMSM.

In addition, the operation of the automotive IPMSM relies on the inverter converting the bus of the power battery into three-phase alternating current, which means that the motor terminal voltage is constrained by the direct current bus; the voltage equation for IPMSM is:

=+- （2）

=++)

wherein the content of the first and second substances,is the d-axis voltage of the motor,is the motor q-axis voltage;as the resistance of the stator,is the electrical angular velocity of the motor.

At high speed steady state, terminal voltage of motorThe magnitude of (d) is approximately:

||= （3）

when the rotating speed of the motor is increased, the voltage of the motor terminal is increased, when the voltage exceeds the amplitude of the alternating voltage provided by the bus voltage, the field weakening control is needed, and the maximum alternating voltage provided by the current bus is the voltage limitThe expression is generally:

wherein the content of the first and second substances,in order to be the bus voltage,the maximum modulation ratio (maximum modulation index) of the motor control system is generally around 1 and is 1.1027 at most.

In order to obtain a current combination which can meet a torque equation and can also meet voltage limitation, dq current combinations corresponding to each torque under different buses and rotating speeds are still obtained through calibration by means of experiments; and then, the data are made into a table and stored in a digital control chip, and the torque commands under different rotating speeds and bus voltages are converted into corresponding dq current commands through table lookup when the motor runs in real time.

The premise that the process can work normally is that the current combination obtained by calibrating the prototype experiment can be suitable for each motor in the same model; in practical applications, the following aspects may make this assumption no longer true:

1. the inconsistency of the motor can be caused by inevitable processes and materials when the motor is produced in batches;

2. when the rotational variation offset of the motor generates deviation, even under the condition that a current regulator normally works, the directional deviation of a controlled upper magnetic field can be caused, and further the actual dq current in the motor is inconsistent with the expected current command;

3. the change of the environmental temperature can affect the magnetic linkage of the permanent magnet, and when the temperature is reduced, the change of the environmental temperature can causeRise, resulting in a scaled dq currentThe flow instructions no longer satisfy the voltage limits.

Therefore, in order to enhance the robustness of the high-speed operation region of the electric drive control system, a flux weakening control link is generally added.

In order to solve the problem of field weakening in motor control, patent document CN101855825B proposes a representative solution, as shown in fig. 1, a voltage deviation is obtained according to a difference between a voltage output by a current regulator and a voltage limit, and the deviation is processed through a proportional-integral (PI) element to obtain a current correction quantity Δ I_dThe current is superposed on the d-axis current setting, and the amplitude limit of the correction amount with the upper limit of 0 is made, so that the field weakening is deepened, and the purpose of field weakening control is achieved. According to formula (3), when)>When 0, increase the negative i_dThe output voltage can be reduced, i.e. this scheme is effective; but when)<When 0, continue to increase the negative i_dThen it will causeThe reverse increase causes the output voltage to further rise, and the voltage saturation phenomenon is more serious; therefore, it is necessary to ensure that the method is used)>0. However, in the motor control for vehicles, if this restriction is added, the reluctance torque of the motor in the high-speed region is not fully utilized, and the performance of the motor is sacrificed. By adopting the scheme, i is reduced when the voltage is saturated_dThe weak magnetic field can be deepened to enable the motor to be out of the voltage saturation state, but the method has a large influence on the output torque because only i is corrected_dLarger i is required_dThe correction amount, dq current combination, changes so greatly that it has a large influence on the output torque. Non-patent literature (T.M. Jahns, "Flux Weakening Regime OperThe first proposal of (a of an Interior Permanent-Magnet Synchronous Motor Drive', IEEE trans. on Ind. appl., vol. IA-23, No. 4, pp. 55-63, 1987) is to reduce i in weak magnetic regions_qBut regulating only a single current also faces the problem of a large impact on the output torque. No better prior art has been found to be able to effectively address the voltage saturation problem while having as little impact on output torque as possible.

Disclosure of Invention

The invention aims to provide a vector flux weakening control method for a permanent magnet synchronous motor for a vehicle, aiming at the defects of the prior art.

The purpose of the invention is realized by the following technical scheme: a vehicle permanent magnet synchronous motor vector flux weakening control method comprises a current closed loop adjusting module, a modulation ratio deviation calculating module, a current instruction angle compensating module, a current angle presetting module, a current instruction angle limiting comparator and a current given vector correcting module;

the input of the current closed-loop regulating module is a dq current instruction, and the dq voltage instruction is output after passing through the proportional-integral controller;

the input of the modulation ratio deviation calculation module is a dq voltage command output by the current closed-loop regulation module, and the desired modulation ratio is obtained through square and evolutionMI _ref Then, the maximum modulation ratio of the control system to the expected maximum modulation ratioMI _max Making a difference, and outputting a modulation ratio deviation after passing through a low-pass filter;

the input of the current instruction angle compensation module is the modulation ratio deviation output by the modulation ratio deviation calculation module, and the correction angle is output after the modulation ratio deviation passes through the proportional-integral compensator;

the current angle presetting module is used for presetting a current angle;

the current instruction angle limiting comparator is used for limiting the current angle after the angle compensation is corrected and output by the current instruction angle compensation module to be above the current angle preset by the current angle presetting module;

the current given vector correction module is used for calculating a dq current instruction after flux weakening control based on a current angle preset by the current angle preset module.

Further, in the current closed loop regulation module, a dq current command i is sent_dref、i_qrefAnd the deviation of the feedback of the dq current is respectively obtained by a proportional-integral controller to obtain a dq voltage instruction.

Further, in the modulation ratio deviation calculating module,MI _max andMI _ref delta difference ofMI ₀Comprises the following steps:

△MI ₀=MI _ref - MI _max

wherein v is_{d_ref}、v_{q_ref}Is the dq voltage command.

Further, in the current command angle compensation module, the correction angle Δ θ:

wherein k is_p、k_iThe proportional coefficient and the integral coefficient of the proportional-integral compensator.

Further, the current angle presetting module limits the orientation of the motor in maximum torque current ratio (MTPA) current angle curve drawing, and presets the current angle to theta _pre 。

Further, the current command angle limit comparator is configured to limit the current angle to:

θ+△θ≥θ _pre

where θ is the current angle before field weakening control.

Further, in the current given vector correction module, a dq current command i is calculated_dref、i_qref：

Therein,. mu.giAnd | is the current magnitude before the field weakening control.

The invention has the following beneficial effects:

1. the adjusting direction of the invention is always the weak magnetic direction, so that the instability caused by repeated adjustment can not occur;

2. according to the invention, dq current is introduced and corrected simultaneously, so that the voltage saturation resistant pressure can be distributed to the dq current, and overlarge output torque deviation caused by excessive single-axis current adjustment is avoided;

3. the invention can ensure the safety of the driving system and reduce the influence of the flux weakening control link on the output torque of the driving system as much as possible.

Drawings

FIG. 1 is a block diagram of a prior art topology for flux weakening control;

FIG. 2 is a block diagram of the overall topology of the present invention;

FIG. 3 is a schematic diagram of a modulation ratio deviation calculation procedure;

FIG. 4 is a schematic diagram of a current command angle compensation module;

FIG. 5 is a schematic diagram of a preset angle setting module for setting a preset angle; wherein the unit of the current is A;

FIG. 6 is a schematic view of current angle correction in the weak magnetic region;

FIG. 7 is a schematic diagram illustrating the current angle variation trend before and after correction; wherein, 1 is before correction, and 2 is after correction;

fig. 8 is a comparison graph of current angles before and after correction.

Detailed Description

As shown in fig. 2, the method for controlling vector flux weakening of a permanent magnet synchronous motor for a vehicle according to the present invention includes:

1. the current closed-loop regulating module: this section is the dependency module of the present invention, which functions to pass dq current commandsi _dref 、i _qref The deviation fed back by the dq current respectively passes through a proportional integral PI controller to obtain a dq voltage instructionv _dqref 。

2. Modulation ratio deviation calculation module: as shown in figure 3 of the drawings,MI _ref closed loop regulation by currentThe dq voltage command square and the square of the module output are obtained as follows:

wherein the content of the first and second substances,v _{d_ref} 、v _{q_ref} is composed ofv _dqref The dq component of (a) of (b),V _dc is the bus voltage; then the maximum modulation ratio is controlled by the desired control systemMI _max To desired modulation ratioMI _ref Making a difference to obtain deltaMI ₀：

△MI ₀=MI _ref - MI _max

Then the modulation ratio deviation delta is obtained through a Low Pass Filter (LPF)MI(ii) a The low-pass filter is used for removing high-frequency noise in the dq current closed-loop regulation module, so that the output flux weakening control device can smooth the correction quantity of the output current and prevent the torque of the motor from relatively large fluctuation.

3. The current instruction angle compensation module: as shown in fig. 4, the output Δ of the module is calculated as the modulation ratio deviationMIFor input, after passing through a proportional integral PI compensator, the output is a correction angle delta theta:

wherein the content of the first and second substances,k _p 、k _i the proportional coefficient and the integral coefficient of the proportional-integral compensator.

4. The current angle presetting module: as shown in FIG. 5, the maximum torque current ratio MTPA current angle curve is plotted and limited for the standard motor orientation, the value is assigned at MTPA (1000) rpm according to the dq current curve, and the current angle is preset to be theta _pre 。

5. Current command angle limit comparator: limiting the angle compensated by the current instruction angle compensation module to the preset angle theta of the current angle preset module _pre Above, theta + DELTAtheta ≧ theta _pre (ii) a Where θ is the angle of the current vector before field weakening.

6. Current given vector correction module (sin/cos): combining a current angle presetting module to calculate the current after the dq axis is subjected to weak magnetismi _dref 、i _qref The following were used:

therein,. mu.giAnd | is the magnitude of the current vector before field weakening. As shown in fig. 6, starting from the weak magnetic inflection point indicated by an arrow, the current command angle limit comparator and the current given vector correction module start to act, and the dq current operation curve is changed by a corresponding angle. As shown in fig. 7, the current angle is automatically corrected in the weak magnetic region. As shown in fig. 8, when the slope of the curve is not 1, it means that the actual angle is larger than the predetermined angle θ _pre The current is given to the vector correction module from 120 degrees later to correct the angle, and the circle is the correction effect.