阅读说明：本技术 一种电驱动系统永磁同步电机矢量弱磁控制系统 (Vector flux weakening control system of permanent magnet synchronous motor of electric drive system ) 是由 于淼 陆玲霞 齐冬莲 于 2020-07-09 设计创作，主要内容包括：本发明公开了一种电驱动系统永磁同步电机矢量弱磁控制系统,该系统由电流闭环调节模块、调制比偏差计算模块、电流特征点设定模块、电流补偿矢量角度计算模块、电流补偿矢量幅值计算模块、电流补偿矢量计算模块和电流指令修正模块组成。本发明以电机三相短路电流为弱磁调节的终点,在发生电压饱和时,均能使电机控制系统退出饱和；电机端部由于存在逆变器通过动力电池母线供电,其端部电压不会低至零,存在较大余量用于应对异常因素；通过引入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。本发明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 vector flux weakening control system of a permanent magnet synchronous motor of an electric drive system, which consists of a current closed loop adjusting module, a modulation ratio deviation calculating module, a current characteristic point setting module, a current compensation vector angle calculating module, a current compensation vector amplitude calculating module, a current compensation vector calculating module and a current instruction correcting module. The motor control system takes the three-phase short-circuit current of the motor as the end point of flux weakening regulation, and can be out of saturation when voltage saturation occurs; the inverter is arranged at the end part of the motor and is supplied with power through the power battery bus, the voltage at the end part of the motor cannot be reduced to zero, and a large margin is reserved for dealing with abnormal factors; by introducing the dq current and correcting simultaneously, the voltage saturation resistant pressure can be distributed to the dq current, and the phenomenon that the output torque deviation is overlarge due to the fact that the uniaxial current is adjusted too much is avoided. 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.)

1. A vector flux weakening control system of a permanent magnet synchronous motor of an electric drive system is characterized by comprising a current closed loop adjusting module, a modulation ratio deviation calculating module, a current characteristic point setting module, a current compensation vector angle calculating module, a current compensation vector amplitude calculating module, a current compensation vector calculating module, a current instruction correcting module and the like.

The current closed loop regulating module corrects the dq current instruction corrected by the current instruction correcting module

The modulation ratio deviation calculation module outputs a dq voltage command v to the current closed-loop regulation module_dref、v_drefThe desired modulation ratio MI is obtained by the following process_ref：

Wherein, V_dcIs the bus voltage; then the maximum modulation ratio MI of the motor control system is set_maxWith desired modulation ratio MI_refDifferencing to give Δ MI₀And finally, obtaining a modulation ratio deviation delta MI through a low-pass filter:

the current characteristic point setting module sets a d-axis bus current i when the three-phase end of the motor is short-circuited_{d_sc}Comprises the following steps:

wherein the content of the first and second substances,for rotor permanent magnet flux, L_dIs the d-axis inductance.

The current compensation vector amplitude calculation module takes the output modulation ratio deviation delta MI of the modulation ratio deviation calculation module as input, and performs proportional integral adjustment as follows to obtain a current vector compensation amplitude | delta i |:

wherein k is_pIs the proportional coefficient, k, of a proportional-integral controller_iIs the integral coefficient of a proportional-integral controller;

the current compensation vector angle calculation module calculates the current operating point (i)_dref，i_qref) To (i)_{d_sc}0) current compensation vector angle θ:

the current compensation vector calculation module calculates dq axis compensation component △ i according to the current vector compensation amplitude | Δ i | output by the current compensation vector amplitude calculation module and the current compensation vector angle θ output by the current compensation vector angle calculation module_dref、△i_drefThe following were used:

Δi_qref＝-|Δi|sinθ

Δi_dref＝|Δi|cosθ

the current command correction module outputs △ i of the current compensation vector calculation module_dref、△i_drefWith the original dq current command i_dref、i_drefThe superposition is carried out to obtain a modified dq current instruction

Technical Field

The invention belongs to the field of permanent magnet synchronous motor control, and particularly relates to a vector flux weakening control system of a permanent magnet synchronous motor of an electric drive system.

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.

IPMSM has characteristics of large power density, wide operation range and high efficiency, and is widely used for a driving motor of an electric vehicle, and a torque equation thereof is as follows:

wherein, T_eIs the electromagnetic torque of the motor; p_nThe number of the magnetic pole pairs of the motor is counted;

is rotor permanent magnet flux; i.e. i_qIs a q-axis current, i_dIs the d-axis current; l is_dIs a d-axis inductor; l is_qIs a q-axis inductor; in the IPMSM normal driving process, T_e＞0,i_q＞0,i_d＞0,L_d＜L_q。

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. Due to magnetic field saturation, dq-axis inductance L after current is greater than a certain range_d、L_qThe 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 depends on the inverter converting the bus of the power battery into three-phase alternating current, which means that the terminal voltage of the motor is constrained by the direct current bus, and the voltage equation of the IPMSM is as follows:

wherein, V_dIs the d-axis voltage of the motor, V_qIs the motor q-axis voltage; r_sIs the stator resistance, omega is the electrical angular velocity of the motor; at high speed steady state, terminal voltage V of motor_sThe magnitude of (d) is approximately:

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 limit V_{s_lmt}The expression for the voltage limit is generally:

wherein, V_dcTo bus voltage, MI_maxThe maximum modulation ratio (maximum modulation ratio) 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 rotation variation offset of the motor generates deviation, the orientation deviation of a magnetic field on the control can be caused, and the actual dq current in the motor is inconsistent with the expected current command, even under the condition that a current regulator normally works;

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 cause

Rising, causing the scaled dq current command to no longer meet the voltage limit.

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.

For the problem of field weakening of motor control, patent CN101855825B of the present invention proposes a representative solution, that is, 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 I_dThe current correction is superimposed on the d-axis current setting, and the correction is limited to be 0 at the upper limit, so that the field weakening is deepened, and the purpose of field weakening control is achieved, as shown in fig. 1. According to formula (3), whenWhile increasing the negative i_dThe output voltage can be reduced, i.e. this scheme is effective. But whenWhile continuing to increase i in the negative direction_dThen V will be made_qThe reverse increase causes the output voltage to rise further, which in turn causes the voltage saturation phenomenon to be more severe. Therefore, it is necessary to ensure that the method is usedHowever, 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 dq current combination is changed so greatly that it has a large influence on the output torque. The literature (T.M. Jahns, "Flux Weak Region Operation of an Interior Permanent-Magnet Synchronous Motor Drive", IEEE trans. on Ind.appl., vol.IA-23, No.4, pp.55-63,1987) proposes a method for reducing i in the weak magnetic region_qThe method of (2), but regulating only a single current also faces the problem of the large impact on output torque mentioned in (2); the better prior art is not found for a while, namely, the problem of voltage saturation can be effectively solved, and the influence on the output torque is as small as possible.

Disclosure of Invention

The invention aims to provide a vector flux weakening control system of a permanent magnet synchronous motor of an electric drive system aiming at the defects of the prior art. In order to enhance the robustness of a high-speed operation area of the electric drive control system, a weak magnetic control link is added.

The purpose of the invention is realized by the following technical scheme: a vector flux weakening control system of a permanent magnet synchronous motor of an electric drive system is composed of a current closed loop adjusting module, a modulation ratio deviation calculating module, a current characteristic point setting module, a current compensation vector angle calculating module, a current compensation vector amplitude calculating module, a current compensation vector calculating module and a current instruction correcting module;

the current closed loop regulating module corrects the dq current instruction corrected by the current instruction correcting module

The input proportional-integral controller obtains a dq voltage command v_dref、v_dref；

The modulation ratio deviation calculation module outputs a dq voltage command v to the current closed-loop regulation module_dref、v_drefThe desired modulation ratio MI is obtained by the following process_ref：

Wherein, V_dcIs the bus voltage; then the maximum modulation ratio MI of the motor control system is set_maxWith desired modulation ratio MI_refDifferencing to give Δ MI₀And finally, obtaining a modulation ratio deviation delta MI through a low-pass filter:

the current characteristic point setting module sets a d-axis bus current i when the three-phase end of the motor is short-circuited_{d_sc}Comprises the following steps:

wherein the content of the first and second substances,for rotor permanent magnet flux, L_dIs a d-axis inductor;

the current compensation vector amplitude calculation module takes the output modulation ratio deviation delta MI of the modulation ratio deviation calculation module as input, and performs proportional integral adjustment as follows to obtain a current vector compensation amplitude | delta i |:

wherein k is_pIs the proportional coefficient, k, of a proportional-integral controller_iIs the integral coefficient of a proportional-integral controller;

the current compensation vector angle calculation module calculates the current operating point (i)_dref，i_qref) To (i)_{d_sc}0) current compensation vector angle θ:

the current compensation vector calculation module calculates dq axis compensation component △ i according to the current vector compensation amplitude | Δ i | output by the current compensation vector amplitude calculation module and the current compensation vector angle θ output by the current compensation vector angle calculation module_dref、△i_drefThe following were used:

Δi_qref＝-|Δi|sinθ

Δi_dref＝|Δi|cosθ

the current command correction module outputs △ i of the current compensation vector calculation module_dref、△i_drefWith the original dq current command i_dref、i_drefThe superposition is carried out to obtain a modified dq current instruction

The invention has the beneficial effects that: the invention relates to a voltage feedforward-based end short-circuit protection system of a permanent magnet synchronous motor for a vehicle, which can reduce the influence of a flux-weakening control link on the output torque of a driving system as much as possible while ensuring the safety of the driving system, and specifically comprises the following steps:

1. the three-phase short-circuit current of the motor is taken as the end point of flux weakening regulation, no matter where the current motor operates, the current motor is not limited by the prior artWhen voltage saturation occurs, the motor control system can exit saturation;

2. the three-phase short-circuit current of the motor is taken as the end point of the flux weakening regulation, the output voltage of the point is zero under the ideal condition, and the point is the limit point of the flux weakening operation of the motor; in fact, the end part of the motor is supplied with power through the power battery bus by the inverter, and the voltage of the end part of the motor is not reduced to zero, so that the invention has a large margin which can be used for dealing with abnormal factors such as flux linkage change of a motor rotor, rotation variation offset deviation and the like which can cause voltage saturation at a high speed;

3. by introducing the dq current and correcting simultaneously, the voltage saturation resistant pressure can be distributed to the dq current, and the phenomenon that the output torque deviation is overlarge due to the fact that the uniaxial current is adjusted too much is avoided.

Drawings

FIG. 1 is a schematic diagram of a prior art flux weakening control system;

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

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

FIG. 4 is a schematic of a current compensation vector angle transformation;

fig. 5 is a schematic diagram of a current compensation vector magnitude transformation.

Detailed Description

As shown in fig. 2, the vector flux weakening control system for the permanent magnet synchronous motor of the electric drive system of the present invention includes a current closed loop adjusting module, a modulation ratio deviation calculating module, a current characteristic point setting module, a current compensation vector angle calculating module, a current compensation vector amplitude calculating module, a current compensation vector calculating module, and a current instruction modifying module, and specifically includes:

(1) the current closed-loop regulating module: dq current instruction corrected by current instruction correction module

The input proportional integral PI controller obtains a dq voltage instruction v_dref、v_dref。

Wherein, K_pd、K_pqRespectively, a d-axis proportional coefficient, a q-axis proportional coefficient, K of the proportional integral PI controller_id、K_iqD-axis integral coefficient q-axis integral coefficient, i of proportional integral PI controller_d、i_qRespectively are dq axis feedback currents collected in real time in the operation of the proportional-integral controller.

(2) As shown in fig. 3, the modulation ratio deviation calculation module: dq voltage instruction v output by current closed loop regulation module_dref、v_drefSquaring and post-evolution, multiplying

Divided by the bus voltage V_dcTo obtain a desired modulation ratio MI_ref：

Maximum modulation ratio MI of motor control system_maxWith desired modulation ratio MI_refTo make a difference, here MI_maxIs settable with a theoretical limit of 0.635; let Δ MI₀＝MI_ref-MI_maxAnd then the modulation ratio deviation delta MI is obtained through a Low Pass Filter (LPF). The low-pass filter is used for removing high-frequency noise in the dq current regulator, so that the output flux weakening control system can smooth the output current correction amount and prevent the motor torque from having large fluctuation.

(3) The current characteristic point setting module: i.e. i_{d_sc}The output voltage of the motor is 0 which is the weak magnetic limit point of the motor and the theoretical value is as follows:

wherein the content of the first and second substances,

for rotor permanent magnet flux, L_dIs the d-axis inductance.Due to saturation effect, i_{d_sc}Will change due to the change of d-axis inductance, but in the high-speed operation region of the motor, i is in steady state_{d_sc}Substantially a fixed value; it is to be noted that i_{d_sc}Which may be greater than the maximum current allowed by the motor drive system, and the scenario used by the present invention is that the short circuit current is less than the maximum current, which is also a common feature of automotive high-speed IPMSM motors.

(4) As shown in fig. 4, the current compensation vector magnitude calculation module: and (3) taking the modulation ratio deviation delta MI as an input, and performing proportional integral PI regulation to obtain a current vector compensation amplitude | delta i |:

wherein k is_pIs the proportional coefficient, k, of a proportional-integral controller_iIs the integral coefficient of a proportional integral controller.

(5) As shown in fig. 5, the current compensation vector angle calculation module: calculating the current operating point (i)_dref，i_qref) To (i)_{d_sc}0) current compensation vector angle θ;

(6) the current compensation vector calculation module: calculating a dq axis compensation component Delta i based on the current vector compensation magnitude Delta i in the module (4) and the current compensation vector angle theta in the module (5)_dref、Δi_drefAs follows

Δi_qref＝-|Δi|sinθ

Δi_dref＝|Δi|cosθ

(7) A current instruction correction module: output delta i of current compensation vector calculation module_dref、Δi_drefWith the original dq current command i_dref、i_drefThe superposition is carried out to obtain a modified dq current instruction