阅读说明：本技术 一种电动汽车永磁同步电机的参数辨识方法 (Parameter identification method for permanent magnet synchronous motor of electric vehicle ) 是由 刘晓刚 田雷 徐劲力 卢杰 黄丰云 于 2019-11-11 设计创作，主要内容包括：本发明公开了一种电动汽车永磁同步电机的参数辨识方法,包括判断电动汽车的永磁同步电机是否需要进行参数辨识；当需要进行参数辨识时,向永磁同步电机的交轴期望电流中注入一低频小幅值正弦电流信号,并由调节器对交轴期望电流、直轴期望电流、交轴电压以及直轴电压进行自动调节；通过转速传感器测量永磁同步电机的转速和位置信号,通过电流传感器采集永磁同步电机的三相电流并转换为直轴反馈电流和交轴反馈电流,将数据实时传递至参数辨识环节；通过参数辨识环节对永磁同步电机进行参数辨识,直至参数收敛。本发明可在电机任何运行状态下进行参数辨识,可以很好地满足不同结构永磁同步电机的控制要求,而且辨识出的参数准确,适用范围广。(The invention discloses a parameter identification method of a permanent magnet synchronous motor of an electric automobile, which comprises the steps of judging whether the permanent magnet synchronous motor of the electric automobile needs to be subjected to parameter identification; when parameter identification is needed, a low-frequency small-amplitude sinusoidal current signal is injected into the quadrature axis expected current of the permanent magnet synchronous motor, and the quadrature axis expected current, the direct axis expected current, the quadrature axis voltage and the direct axis voltage are automatically adjusted by an adjuster; measuring rotating speed and position signals of the permanent magnet synchronous motor through a rotating speed sensor, acquiring three-phase current of the permanent magnet synchronous motor through a current sensor, converting the three-phase current into direct-axis feedback current and quadrature-axis feedback current, and transmitting data to a parameter identification link in real time; and performing parameter identification on the permanent magnet synchronous motor through a parameter identification link until the parameters are converged. The invention can identify the parameters under any running state of the motor, can well meet the control requirements of permanent magnet synchronous motors with different structures, and has accurate identified parameters and wide application range.)

1. A parameter identification method for a permanent magnet synchronous motor of an electric vehicle is characterized by comprising the following steps:

detecting the running state of the electric automobile, and judging whether a permanent magnet synchronous motor of the electric automobile needs to carry out parameter identification;

when the permanent magnet synchronous motor is judged to need parameter identification, injecting a low-frequency small-amplitude sinusoidal current signal into the quadrature axis expected current of the permanent magnet synchronous motor, and automatically adjusting the quadrature axis expected current, the direct axis expected current, the quadrature axis expected voltage and the direct axis expected voltage by an adjuster to enable the quadrature axis current, the direct axis expected current, the quadrature axis expected voltage and the direct axis expected voltage to be in a sinusoidal fluctuation state and keep the output torque constant;

acquiring rotating speed and position signals of the permanent magnet synchronous motor through a rotating speed sensor, acquiring three-phase current of the permanent magnet synchronous motor through a current sensor, converting the three-phase current into direct-axis feedback current and quadrature-axis feedback current, and transmitting the direct-axis feedback current, the quadrature-axis feedback current, the rotating speed of a rotor, direct-axis expected voltage and quadrature-axis expected voltage to a parameter identification link in real time after low-pass filtering;

and identifying the parameters of the permanent magnet synchronous motor by a recursive least square method with a forgetting factor preset in the parameter identification link until the parameters are converged.

2. The method for identifying the parameters of the PMSM of the electric vehicle according to claim 1, wherein the parameters include direct-axis inductance, quadrature-axis inductance, stator resistance and rotor flux linkage amplitude.

3. The method for identifying the parameters of the PMSM of the electric vehicle as claimed in claim 2, wherein the method for judging whether the PMSM of the electric vehicle needs to identify the parameters comprises the following steps:

when the electric automobile is cold started, starting a parameter identification system;

when the variation amplitude of the rotating speed or the torque of the permanent magnet synchronous motor of the electric automobile exceeds a preset value, starting a parameter identification system;

and when the duration of the electric automobile under the stable operation working condition exceeds a preset time length, starting the parameter identification system, wherein the electric automobile is indicated to be under the stable operation working condition when the variation amplitude of the rotating speed and the torque of the electric automobile does not exceed a preset value in a preset time period.

4. The method for identifying parameters of the PMSM of the electric vehicle as claimed in claim 3, wherein the regulators comprise a torque regulator, a direct-axis current regulator and a quadrature-axis current regulator, wherein,

the torque regulator is used for regulating the quadrature axis expected current to control the torque, the direct axis expected current is calculated after the quadrature axis expected current is input into the MTPA module, the direct axis current regulator controls the direct axis current by regulating the direct axis expected voltage, and the quadrature axis current regulator controls the quadrature axis current by regulating the quadrature axis expected voltage.

5. The method for identifying the parameters of the PMSM of the electric vehicle as claimed in claim 4, wherein the step of acquiring the rotation speed and position signals of the PMSM by the rotation speed sensor, acquiring the three-phase current of the PMSM by the current sensor, converting the three-phase current into the direct axis feedback current and the quadrature axis feedback current, and transmitting the direct axis feedback current, the quadrature axis feedback current, the rotation speed of the rotor, the direct axis expected voltage and the quadrature axis expected voltage to the parameter identification link in real time comprises the steps of:

acquiring rotating speed and position signals of the permanent magnet synchronous motor through a rotating speed sensor;

the method comprises the steps that current of a permanent magnet synchronous motor is collected through a current sensor, low-pass filtering is carried out on the current, and the current is output to a three-phase static-two-phase rotating coordinate transformation link, wherein the current at least comprises A-phase stator current and B-phase stator current;

in the three-phase static-two-phase rotating coordinate transformation link, the A-phase stator current and the B-phase stator current in the three-phase static coordinate system are transformed through Park transformation and Clerk transformation to obtain direct-axis feedback current and quadrature-axis feedback current in the quadrature-direct-axis rotating coordinate system, and the obtained direct-axis feedback current and quadrature-axis feedback current are respectively input into a direct-axis current regulator and a quadrature-axis current regulator;

obtaining quadrature axis expected voltage through the quadrature axis current regulator according to the difference value of the quadrature axis expected current and the quadrature axis feedback current, and obtaining direct axis expected voltage through the direct axis current regulator according to the difference value of the direct axis expected current and the direct axis feedback current;

and transmitting the direct axis feedback current, the quadrature axis feedback current, the rotating speed, the direct axis expected voltage and the quadrature axis expected voltage to a parameter identification link in real time.

6. The method for identifying the parameters of the permanent magnet synchronous motor of the electric automobile according to claim 5, wherein the parameter identification equation of the permanent magnet synchronous motor is as follows:

wherein u is_dAnd u_qRespectively representing desired voltage values of the direct axis and the quadrature axis, i_dAnd i_qRespectively representing direct and quadrature axis feedback current values, L_dAnd L_qRespectively representing direct and quadrature inductance values, R_sRepresenting stator resistance value, ω_eWhich represents the value of the electrical angular velocity of the rotor,representing the rotor flux linkage amplitude.

7. The method for identifying the parameters of the permanent magnet synchronous motor of the electric automobile according to claim 6, wherein the parameter identification equation is converted into an equation in accordance with a recursive least square format with forgetting factors after being discretized.

8. The method for identifying the parameters of the permanent magnet synchronous motor of the electric automobile according to claim 7, wherein the discrete parameter identification equation is as follows:

wherein u is_d(k)And u_q(k)Respectively representing the direct axis desired voltage value and the quadrature axis desired voltage value at the time k,

9. The method for identifying parameters of the permanent magnet synchronous motor of the electric vehicle according to claim 8, wherein the step of identifying the parameters of the permanent magnet synchronous motor through a preset discrete parameter identification equation in a parameter identification link until the parameters converge further comprises the following steps:

and storing the calculated parameters and using the parameters as initial values for parameter identification of the permanent magnet synchronous motor next time.

Technical Field

The invention relates to the technical field of motor control, in particular to a parameter identification method for a permanent magnet synchronous motor of an electric vehicle.

Background

The permanent magnet synchronous motor is widely applied in the field of new energy vehicles and the industrial field due to the advantages of high efficiency, high power density and the like. In the operation process of the permanent magnet synchronous motor, four important parameters, namely direct axis inductance, quadrature axis inductance, stator resistance and rotor flux linkage amplitude, can change along with different operation conditions, and the change of the parameters can directly influence the efficiency and stability of a motor control system. For the driving motor of the electric automobile, the rotating speed and the torque of the driving motor of the electric automobile are constantly changed, and the electric automobile has high requirements on the efficiency and the stability of a driving system, so that the online parameter identification of the permanent magnet synchronous motor is needed on the electric automobile, and the performance of a control system is improved by improving the accuracy of parameters.

The existing parameter identification methods for the permanent magnet synchronous motor comprise a least square method, a model reference adaptive method, a Kalman filtering method and the like, and the methods have a common problem of identifying equation underrank. Parameter identification is generally performed using the following equation (1):

in the formula u_dAnd u_qRepresenting the direct and quadrature voltages, i, respectively_dAnd i_qRespectively representing direct and quadrature currents, L_dAnd L_qRespectively representing direct and quadrature inductances, R_sRepresenting stator resistance, ω_eWhich is indicative of the electrical angular velocity of the rotor,

representing the rotor flux linkage amplitude. When the motor running state is stable, the direct-axis current and the quadrature-axis current change slowly, so that in order to avoid expanding current measurement errors by a differential term, the current differential term is generally ignored, and the above equation is simplified into equation (2):

it can be seen that the identification equation is of the second order, but the number of the parameters to be identified is four, that is, the identification equation is not of rank, and the accurate parameters cannot be identified. The solving methods comprise the following steps:

(1) reducing the parameters to be identified. Considering two of the four parameters as fixed quantities and recognizing only the remaining two parameters, such a scheme may cause the recognition result to deviate from the true value.

(2) The order of the equation is increased by adding an equation, such as by measuring a torque value, using the torque equation as an identification equation. This solution requires the use of additional sensors, increases costs and is not easy to implement.

(3) The method adopts other means to obtain a certain parameter value, such as measuring the winding temperature through a temperature sensor, and obtaining the resistance value at the current temperature according to the physical characteristics of the winding, thereby increasing the cost.

(4) The high-frequency current is injected into the winding, and the parameter value is deduced through the response of the measuring system, so that the scheme has large calculation amount, complex process and high requirement on the performance of the controller.

Thus, the prior art has yet to be improved and enhanced.

Disclosure of Invention

In view of the above disadvantages of the prior art, an object of the present invention is to provide a method for identifying parameters of a permanent magnet synchronous motor of an electric vehicle, which can identify the parameters under various current states, and the identified parameters are accurate.

In order to achieve the purpose, the invention adopts the following technical scheme:

a parameter identification method for an electric vehicle permanent magnet synchronous motor comprises the following steps:

detecting the running state of the electric automobile, and judging whether a permanent magnet synchronous motor of the electric automobile needs to carry out parameter identification;

when the permanent magnet synchronous motor is judged to need parameter identification, injecting a low-frequency small-amplitude sinusoidal current signal into the quadrature axis expected current of the permanent magnet synchronous motor, and automatically adjusting the quadrature axis expected current, the direct axis expected current, the quadrature axis expected voltage and the direct axis expected voltage by an adjuster to enable the quadrature axis current, the direct axis expected current, the quadrature axis expected voltage and the direct axis expected voltage to be in a sinusoidal fluctuation state and keep the output torque constant;

acquiring rotating speed and position signals of the permanent magnet synchronous motor through a rotating speed sensor, acquiring three-phase current of the permanent magnet synchronous motor through a current sensor, converting the three-phase current into direct-axis feedback current and quadrature-axis feedback current, and transmitting the direct-axis feedback current, the quadrature-axis feedback current, the rotating speed of a rotor, direct-axis expected voltage and quadrature-axis expected voltage to a parameter identification link in real time after low-pass filtering;

and identifying the parameters of the permanent magnet synchronous motor by a recursive least square method with a forgetting factor preset in the parameter identification link until the parameters are converged.

Preferably, in the parameter identification method for the permanent magnet synchronous motor of the electric vehicle, the parameters include direct axis inductance, quadrature axis inductance, stator resistance and rotor flux linkage amplitude.

Preferably, in the method for identifying parameters of a permanent magnet synchronous motor of an electric vehicle, the method for determining whether the permanent magnet synchronous motor of the electric vehicle needs to identify parameters includes:

when the electric automobile is cold started, starting a parameter identification system;

when the variation amplitude of the rotating speed or the torque of the permanent magnet synchronous motor of the electric automobile exceeds a preset value, starting a parameter identification system;

and when the duration of the electric automobile under the stable operation working condition exceeds a preset time length, starting the parameter identification system, wherein the electric automobile is indicated to be under the stable operation working condition when the variation amplitude of the rotating speed and the torque of the electric automobile does not exceed a preset value in a preset time period.

Preferably, in the parameter identification method of the permanent magnet synchronous motor of the electric vehicle, the regulator includes a torque regulator, a direct-axis current regulator and a quadrature-axis current regulator, wherein,

the torque regulator is used for regulating the quadrature axis expected current to control the torque, the direct axis expected current is calculated after the quadrature axis expected current is input into the MTPA module, the direct axis current regulator controls the direct axis current by regulating the direct axis expected voltage, and the quadrature axis current regulator controls the quadrature axis current by regulating the quadrature axis expected voltage.

Preferably, in the method for identifying parameters of a permanent magnet synchronous motor of an electric vehicle, the step of acquiring the rotating speed and position signals of the permanent magnet synchronous motor through a rotating speed sensor, acquiring the three-phase current of the permanent magnet synchronous motor through a current sensor, converting the three-phase current into the direct axis feedback current and the quadrature axis feedback current, and transmitting the direct axis feedback current, the quadrature axis feedback current, the rotating speed of the rotor, the direct axis expected voltage and the quadrature axis expected voltage to the parameter identification link in real time includes:

acquiring rotating speed and position signals of the permanent magnet synchronous motor through a rotating speed sensor;

the method comprises the steps that current of a permanent magnet synchronous motor is collected through a current sensor, low-pass filtering is carried out on the current, and the current is output to a three-phase static-two-phase rotating coordinate transformation link, wherein the current at least comprises A-phase stator current and B-phase stator current;

in the three-phase static-two-phase rotating coordinate transformation link, the A-phase stator current and the B-phase stator current are transformed through Park transformation and Clerk transformation to obtain direct-axis feedback current and quadrature-axis feedback current under a quadrature-direct-axis rotating coordinate system, and the obtained direct-axis feedback current and quadrature-axis feedback current are respectively input into a direct-axis current regulator and a quadrature-axis current regulator;

obtaining quadrature axis expected voltage through the quadrature axis current regulator according to the difference value of the quadrature axis expected current and the quadrature axis feedback current, and obtaining direct axis expected voltage through the direct axis current regulator according to the difference value of the direct axis expected current and the direct axis feedback current;

and transmitting the direct axis feedback current, the quadrature axis feedback current, the rotating speed, the direct axis expected voltage and the quadrature axis expected voltage to a parameter identification link in real time.

Preferably, in the parameter identification method for the permanent magnet synchronous motor of the electric vehicle, a parameter identification equation of the permanent magnet synchronous motor is as follows:

wherein u is_dAnd u_qRespectively representing desired voltage values of the direct axis and the quadrature axis, i_dAnd i_qRespectively representing direct and quadrature axis feedback current values, L_dAnd L_qRespectively representing direct and quadrature inductance values, R_sRepresenting stator resistance value, ω_eWhich represents the value of the electrical angular velocity of the rotor,

representing the rotor flux linkage amplitude.

Preferably, in the parameter identification method of the permanent magnet synchronous motor of the electric vehicle, the parameter identification equation is converted into an equation in accordance with a recursive least square format with forgetting factors after being dispersed.

Preferably, in the parameter identification method of the permanent magnet synchronous motor of the electric vehicle, the parameter identification equation after dispersion is as follows:

wherein u is_d(k)And

respectively representing the direct axis desired voltage value and the quadrature axis desired voltage value at the time k,and

respectively representing the direct axis feedback current value and the quadrature axis feedback current value at the time k,and

respectively representing the direct axis feedback current value and the quadrature axis feedback current value at the time k-1, L_dAnd L_qRespectively representing direct and quadrature inductance values, R_sThe value of the resistance of the stator is represented,

representing the value of the rotor electrical angular velocity at time k,representing the rotor flux linkage amplitude.

Preferably, in the method for identifying parameters of a permanent magnet synchronous motor of an electric vehicle, the step of identifying parameters of the permanent magnet synchronous motor by a preset discrete parameter identification equation in a parameter identification link further includes:

and storing the calculated parameters and using the parameters as initial values for parameter identification of the permanent magnet synchronous motor next time.

Compared with the prior art, the parameter identification method of the permanent magnet synchronous motor of the electric automobile comprises the steps of judging whether the permanent magnet synchronous motor of the electric automobile needs to be subjected to parameter identification; when parameter identification is needed, a low-frequency small-amplitude sinusoidal current signal is injected into quadrature-axis current of the permanent magnet synchronous motor, and the regulator automatically regulates quadrature-axis expected current, direct-axis expected current, quadrature-axis voltage and direct-axis voltage; acquiring rotating speed and position signals of the permanent magnet synchronous motor through a rotating speed sensor, converting three-phase current of the acquired permanent magnet synchronous motor into direct-axis feedback current and quadrature-axis feedback current, and transmitting data to a parameter identification link in real time; and performing parameter identification on the permanent magnet synchronous motor through a parameter identification link until the parameters are converged. The invention can identify the parameters under any running state of the motor, can well meet the control requirements of permanent magnet synchronous motors with different structures such as embedded type, surface-mounted type and the like, and has accurate identified parameters and wide application range.

Drawings

Fig. 1 is a flowchart of a parameter identification method for a permanent magnet synchronous motor of an electric vehicle according to a preferred embodiment of the present invention;

FIG. 2 is a schematic block diagram of a parameter identification method for a permanent magnet synchronous motor of an electric vehicle according to a preferred embodiment of the present invention;

fig. 3 is a flowchart of the step S300 in the method for identifying parameters of a permanent magnet synchronous motor of an electric vehicle according to the present invention;

FIG. 4 is a torque simulation diagram during normal operation of the motor;

FIG. 5 is a current simulation diagram during normal operation of the motor;

FIG. 6 is a simulation variation diagram of torque during parameter identification according to the parameter identification method for the PMSM of the electric vehicle provided by the invention;

FIG. 7 is a simulation variation diagram of current during parameter identification according to the parameter identification method for the permanent magnet synchronous motor of the electric vehicle provided by the invention;

FIG. 8 is a diagram illustrating a direct axis inductance identification result of a preferred embodiment of the method for identifying parameters of a PMSM of an electric vehicle according to the present invention;

FIG. 9 is a cross-axis inductance identification result diagram of a preferred embodiment of the method for identifying parameters of a PMSM of an electric vehicle according to the present invention;

FIG. 10 is a diagram illustrating a rotor flux linkage identification result of the method for identifying parameters of a PMSM of an electric vehicle according to the present invention in an embodiment of the present invention;

fig. 11 is a diagram of a rotor resistance identification result of a preferred embodiment of the method for identifying parameters of a permanent magnet synchronous motor of an electric vehicle according to the present invention.

Detailed Description

The invention provides a parameter identification method for a permanent magnet synchronous motor of an electric vehicle, which is further described in detail below by referring to the attached drawings and embodiments in order to make the purpose, technical scheme and effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to fig. 1 and fig. 2, the method for identifying parameters of a permanent magnet synchronous motor of an electric vehicle according to the present embodiment includes the following steps:

s100, detecting the running state of the electric automobile, and judging whether a permanent magnet synchronous motor of the electric automobile needs to be subjected to parameter identification;

s200, when the permanent magnet synchronous motor is judged to need parameter identification, injecting a low-frequency small-amplitude sinusoidal current signal into the quadrature axis expected current of the permanent magnet synchronous motor, and automatically adjusting the quadrature axis expected current, the direct axis expected current, the quadrature axis expected voltage and the direct axis expected voltage by an adjuster to enable the quadrature axis current, the direct axis expected current, the quadrature axis expected voltage and the direct axis expected voltage to be in a sinusoidal fluctuation state and keep the output torque constant;

s300, acquiring rotating speed and position signals of the permanent magnet synchronous motor through a rotating speed sensor, acquiring three-phase current of the permanent magnet synchronous motor through a current sensor, converting the three-phase current into direct axis feedback current and quadrature axis feedback current, and transmitting the direct axis feedback current, the quadrature axis feedback current, the rotating speed of a rotor, direct axis expected voltage and quadrature axis expected voltage to a parameter identification link in real time after low-pass filtering;

s400, identifying parameters of the permanent magnet synchronous motor through a recursive least square method with a forgetting factor preset in a parameter identification link until the parameters are converged.

In a preferred embodiment, the parameters include direct axis inductance, quadrature axis inductance, stator resistance, and rotor flux linkage magnitude.

In a preferred embodiment, the regulators include a torque regulator, a direct current regulator, and a quadrature current regulator, wherein,

the torque regulator is used for regulating the quadrature axis expected current to control the torque, the direct axis expected current is calculated after the quadrature axis expected current is input into the MTPA module, the direct axis current regulator controls the direct axis current by regulating the direct axis expected voltage, and the quadrature axis current regulator controls the quadrature axis current by regulating the quadrature axis expected voltage.

Specifically, the parameter identification method provided by the invention can be used for various running states of the permanent magnet synchronous motor, and the parameter identification can be completed in the normal running process of the electric automobile without running in the state that the direct-axis current is 0, and the output torque is not influenced. The system for realizing the parameter identification method comprises a torque control part and a parameter identification part. In the torque control part, the input of the system is the expected torque, the speed regulator regulates the quadrature axis expected current component according to the difference value of the expected torque and the feedback torque, then the quadrature axis expected current component is input into an MTPA module (a motor maximum torque current ratio control module), and the direct axis expected current component which accords with the MTPA current track is obtained through calculation, so that the motor operation efficiency is improved. Then, errors of quadrature-axis current components and errors of direct-axis current components are respectively adjusted through a quadrature-axis current regulator and a direct-axis current regulator, and quadrature-axis expected voltage and direct-axis expected voltage are output; then, an SVPWM module (space voltage vector pulse width modulation module) generates high and low level signals for controlling the on-off of a power device of the inverter according to the direct axis expected voltage, the quadrature axis expected voltage and the position signal of the motor rotor, and the inverter further converts the direct current into alternating current for driving the permanent magnet synchronous motor so that the motor outputs expected torque.

Further, since the current and voltage of the direct axis and the quadrature axis of the motor are substantially maintained stable when the motor operates in a state where the torque and the rotation speed are stable, four parameters cannot be identified according to the equations (1) and (2). Therefore, in this embodiment, a sinusoidal current signal, preferably a low-frequency small-amplitude current signal, is additionally injected into the quadrature-axis reference current of the permanent magnet synchronous motor, the additionally injected current signal is equivalent to an external disturbance, which may cause a change in the output torque of the motor, and at the same time, in order to make the output torque equal to the desired torque, the control system adjusts the quadrature-axis desired current and the direct-axis desired current through the torque adjuster, so that the torque does not fluctuate greatly. Namely, a sinusoidal current signal is additionally injected into the quadrature axis desired current, so that the four quantities of the quadrature axis desired current, the direct axis desired current, the quadrature axis desired voltage and the direct axis desired voltage are subjected to sinusoidal fluctuation, but the torque is not subjected to large fluctuation. When each electric signal is fluctuated by injecting a current signal, feedback current, voltage and rotating speed signals are measured by a sensor, and measured data are transmitted to a parameter identification link in real time, and a preset program in the parameter identification link identifies motor parameters in real time according to the data.

By adopting the identification method provided by the embodiment, the vehicle can finish parameter identification in the normal running process, and the output torque is not influenced. The permanent magnet synchronous motor of the electric automobile can be divided into two different control modes of MTPA and weak magnetism, current can deviate from an ideal MTPA and weak magnetism track when a current injection method is used for parameter identification, and the calculation amount of a controller can be increased when the parameter identification is carried out. And the parameter identification system does not need to work continuously, and the system judges whether the parameter identification system needs to be started or not by detecting the actual running state of the vehicle.

Preferably, the method for judging whether the permanent magnet synchronous motor of the electric vehicle needs to perform parameter identification comprises the following steps:

when the electric automobile is cold started, starting a parameter identification system;

when the variation amplitude of the rotating speed or the torque of the permanent magnet synchronous motor of the electric automobile exceeds a preset value, starting a parameter identification system;

and when the duration of the electric automobile under the stable operation working condition exceeds a preset time length, starting the parameter identification system, wherein the electric automobile is indicated to be under the stable operation working condition when the variation amplitude of the rotating speed and the torque of the electric automobile does not exceed a preset value in a preset time period.

Specifically, when the electric vehicle is in cold start, the parameter identification system is started, the design parameters of the permanent magnet synchronous motor are used as initial values to identify the parameters, and the identified parameters are used as actual parameters to control the motor. And when the system detects and judges that the stable operation working condition is entered, stopping parameter identification, and taking the identified parameters as actual parameters of the stable operation stage. When the torque or the rotating speed of the electric automobile is greatly changed, a parameter identification system is started, the parameters obtained by the previous identification are used as initial values to identify the parameters, and the parameters obtained by the identification are used as actual parameters to control the motor. And when the system judges that the electric automobile enters the stable operation working condition, stopping parameter identification, and taking the identified parameters as the actual parameters of the stable operation stage. When the duration of the electric automobile under a stable operation condition reaches a preset value, starting parameter identification, taking the parameters obtained by the previous identification as initial values to carry out parameter identification, stopping parameter identification after parameter convergence, and using new parameter values for a control system. Therefore, the method provided by the invention is suitable for various running states of the motor, and can well meet the control requirements of the permanent magnet synchronous motor.

Further, referring to fig. 3, the step S300 specifically includes:

s301, acquiring rotating speed and position signals of the permanent magnet synchronous motor through a rotating speed sensor;

s302, collecting current of the permanent magnet synchronous motor through a current sensor, carrying out low-pass filtering, and outputting the current to a three-phase static-two-phase rotating coordinate transformation link, wherein the current comprises A-phase stator current and B-phase stator current;

s303, converting the A-phase stator current and the B-phase stator current under the three-phase static coordinate system to obtain a direct-axis feedback current and a quadrature-axis feedback current under the quadrature-direct-axis rotating coordinate system through Park conversion and Clerk conversion in the three-phase static-two-phase rotating coordinate conversion link, and respectively inputting the obtained direct-axis feedback current and the quadrature-axis feedback current into a direct-axis current regulator and a quadrature-axis current regulator;

s304, obtaining quadrature axis expected voltage through the quadrature axis current regulator according to the difference value of the quadrature axis expected current and the quadrature axis feedback current, and obtaining direct axis expected voltage through the direct axis current regulator according to the difference value of the direct axis expected current and the direct axis feedback current;

s305, transmitting the direct axis feedback current, the quadrature axis feedback current, the rotating speed, the direct axis expected voltage and the quadrature axis expected voltage to a parameter identification link in real time.

Specifically, referring to fig. 2 and 3 together, the difference between the desired torque input by the system and the feedback torque of the motor is obtained through a torque regulator to obtain a quadrature desired current Iq and input into a quadrature current regulator, the quadrature desired current Iq is calculated through an MTPA module to obtain a direct desired current Id, the direct desired current Id is input into a direct current regulator, during parameter identification, the currents Ia and Ib of the motor are detected through current sensors, then the direct feedback current Id and the quadrature feedback current Iq are obtained through a coordinate transformation link transformation, and then the direct feedback current Id and the quadrature feedback current Iq are respectively input into the direct current regulator and the quadrature current regulator, so that the difference between the quadrature desired current Iq and the quadrature feedback current Iq is obtained through the quadrature current regulator to obtain a quadrature desired voltage Uq, and the difference between the direct reference current Id and the direct feedback current Id is obtained through the direct current regulator to obtain a direct desired voltage Ud (ii) a Meanwhile, a rotating speed signal (rotor electrical angular speed) omega e of the permanent magnet synchronous motor is acquired through a photoelectric encoder, and then Id, Iq, Ud, Uq and omega e are transmitted to a parameter identification link in real time.

Further, the parameter identification link may be configured to perform parameter identification, and the parameter identification of the permanent magnet synchronous motor is performed based on a parameter identification equation, specifically, the parameter identification equation of the permanent magnet synchronous motor is as follows:

wherein u is_dAnd u_qRespectively representing desired voltage values of the direct axis and the quadrature axis, i_dAnd i_qRespectively representing direct and quadrature axis feedback current values, L_dAnd L_qRespectively representing direct and quadrature inductance values, R_sRepresenting stator resistance value, ω_eWhich represents the value of the electrical angular velocity of the rotor,

the rotor flux linkage amplitude is expressed, and since the originally stable and unchangeable alternating-axis and direct-axis current components are changed into the amount of sine fluctuation along with time through current injection, the current differential terms cannot be ignored, so that the equation (3) needs to be discretized.

Specifically, in this embodiment, the parameter identification equation is converted into an equation conforming to a recursive least square format with a forgetting factor after being discretized, and the recursive minimum multiplication algorithm with the forgetting factor is as in equation (4):

therefore, equation (3) is discretized and converted to an equation conforming to the least squares format as shown in equation (5):

wherein u is_d(k)And

respectively representing the direct axis desired voltage value and the quadrature axis desired voltage value at the time k,

and

respectively representing the direct axis feedback current value and the quadrature axis feedback current value at the time k,

andrespectively representing the direct axis feedback current value and the quadrature axis feedback current value at the time k-1, L_dAnd L_qRespectively representing direct and quadrature inductance values, R_sThe value of the resistance of the stator is represented,

representing the value of the rotor electrical angular velocity at time k,

representing the rotor flux linkage amplitude. In the equation (5), the process is as follows,

corresponds to theta in equation (3)_(k)The parameter vector is identified;

corresponds to y_(k)；

Correspond to

And (5) substituting the measured data into the data to carry out iterative operation according to the equation (4) and the equation (5) until the parameters are converged.

In a preferred embodiment, after the step S400, the method further includes:

and storing the calculated parameters and using the parameters as initial values for parameter identification of the permanent magnet synchronous motor next time.

Further, in the simulation verification, the motor parameters are shown in the following table:

the target torque is set to 40Nm, and simulation data of normal running of the motor are shown in FIGS. 4 and 5, wherein the torque is stabilized at 40Nm, the fluctuation is small, the direct-axis current is-14.5A, the quadrature-axis current is 22A, and the MTPA current track is formed. Fig. 6 and 7 show simulation data for injecting a sinusoidal current signal with amplitude of 2A and frequency of 2Hz into the quadrature axis. The torque was still stabilized at 40Nm at this time, and no torque ripple occurred, as in the torque effect when no current was injected. This is achieved byThe time direct axis current and the quadrature axis current are fluctuated, and the fluctuation frequency is the same as the frequency of the injection signal. FIGS. 8, 9, 10, and 11 show the direct-axis inductance Ld, quadrature-axis inductance Lq, and the rotor flux linkage, respectivelyAnd the recognition result of the rotor resistance Rs, the 4 parameters can be converged to the vicinity of the true value in a short time from the image. The table below shows the identification results of the parameters at each time point, and it can be seen from the table that the identification results are already very close to the true values at 0.8s, where the true value of the direct-axis inductance is 0.006, the identification value is 0.00626, and the error is 4.3%; the quadrature axis inductance true value is 0.015, the identification value is 0.01503, and the error is 0.2%; the true value of the rotor flux linkage is 0.175, the identification value is 0.18699, and the error is 6.9%; the real value of the stator resistance is 0.2, the identification value is 0.19249, the error is 3.8%, and the error is small, so that the method can be widely applied.

Time(s)	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8
									Ld(H)	0.00756	0.00661	0.00647	0.00640	0.00636	0.00635	0.00635	0.00626
Lq(H)	0.01498	0.01497	0.01497	0.01501	0.01502	0.01503	0.01503	0.01503
									φ(Wb)	0.20475	0.19205	0.19004	0.18900	0.18855	0.18837	0.18813	0.18699
Rs(Ω)	0.21639	0.18957	0.18869	0.19324	0.19295	0.19063	0.19267	0.19249

In summary, the parameter identification method for the permanent magnet synchronous motor of the electric vehicle provided by the invention includes the steps of judging whether the permanent magnet synchronous motor of the electric vehicle needs to perform parameter identification; when parameter identification is needed, a low-frequency small-amplitude sinusoidal current signal is injected into the quadrature axis expected current of the permanent magnet synchronous motor, and the regulator automatically regulates the quadrature axis expected current, the direct axis expected current, the quadrature axis expected voltage and the direct axis expected voltage; acquiring rotating speed and position signals of the permanent magnet synchronous motor through a rotating speed sensor, converting three-phase current of the acquired permanent magnet synchronous motor into direct-axis feedback current and quadrature-axis feedback current, and transmitting data to a parameter identification link in real time; and performing parameter identification on the permanent magnet synchronous motor through a parameter identification link until the parameters are converged. The invention can identify the parameters under any running state of the motor, can well meet the control requirements of permanent magnet synchronous motors with different structures such as embedded type, surface-mounted type and the like, and has accurate identified parameters and wide application range.

It should be understood that equivalents and modifications of the technical solution and inventive concept thereof may occur to those skilled in the art, and all such modifications and alterations should fall within the scope of the appended claims.