High-speed permanent magnet synchronous motor position identification method

Abstract

The invention discloses a high-speed permanent magnet synchronous motor position identification method, which comprises the following steps of: sampling a, b and c three-phase current of a motor, performing Clarke conversion on the obtained current to obtain alpha-axis and beta-axis current on a two-phase static coordinate system, estimating output voltage of the alpha-axis and beta-axis according to SVPWM (Space Vector Pulse Width Modulation) conduction time calculated in the previous control period, and identifying the position of the high-speed permanent magnet synchronous motor according to the output voltage of the alpha-axis and beta-axis. A position estimation reference quantity is obtained by directly processing current and voltage, the angle and the rotating speed of the position estimation reference quantity can be calculated by using a phase-locked loop, and the position information of the motor is calculated according to the angle and the rotating speed. And the position identification precision under a low carrier frequency ratio is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of motor control, and particularly relates to a high-speed permanent magnet synchronous motor position identification method. BACKGROUND

[0002] High-speed motors have the advantages of high power density and high reliability when driving high-speed loads, and are mainly applied to the fields of flywheel energy storage, aerospace and electric vehicles. Among them, high-speed permanent magnet synchronous motors become the type of motor with the highest power density due to the use of permanent magnet excitation, and are widely used in the above fields. Since the response speed and reliability of the rotor position sensor are difficult to guarantee at high speed, high-speed permanent magnet synchronous motors mostly use position sensorless control methods. The commonly used position identification method based on sliding film observer has small calculation amount and good stability at high speed, but the observation signal has chattering. The introduction of a filter can suppress chattering, but when the motor works in the super high speed or low load frequency ratio (the ratio of the control frequency to the motor fundamental frequency) working condition, the chattering frequency of the signal is close to the motor operating fundamental frequency, and it is difficult to effectively filter out, and the introduction of the filter also brings the problem of phase lag of position identification.

[0003] To solve the error problem of high-speed permanent magnet synchronous motor position identification, the existing solutions mainly solve it from two aspects of compensating the sliding film observer algorithm error and using non-sliding film observer algorithm. Patent CN114826042B proposes to inject a high-frequency disturbance into the rotor position estimation signal based on the sliding film observer method, and extract the response of the disturbance signal from the q-axis current signal, so as to compensate the position signal. The signal does not need to use motor parameters and can compensate the rotor signal error caused by various factors at one time, but this method needs to inject a high-frequency position signal, and when the motor fundamental frequency is high or the load frequency ratio is low, the injected signal cannot meet the position compensation requirement and may interfere with the normal operation of the motor. Patent CN116488514B uses a reduced-order Kalman filter to obtain motor position and angle estimation values, which reduces the calculation burden of the Kalman filter, but still needs to calculate a third-order Kalman filter algorithm in real time, which is complex and difficult to adjust. Patent CN113078851B uses a flux calculation method based on a current model to improve the flux observer of the current model method, which has high anti-interference ability, but this method uses the estimated position of the last period when calculating the rotor position of the current period, so the estimation result at low load frequency ratio still has the problem of phase lag. SUMMARY

[0004] The purpose of the present application is to provide a high-speed permanent magnet synchronous motor position identification method to solve the identification error problem of the existing position identification method when working at low load frequency ratio.

[0005] The technical solution for achieving the purpose of the present application is:

[0006] A high-speed permanent magnet synchronous motor position identification method, the motor rotor position is obtained by the following formula and rotating speed :

[0007] ;

[0008] ;

[0009] wherein and respectively are the discretized permanent magnet synchronous motor position estimation reference quantity angle and rotating speed calculated by phase-locked loop, is the inductance on the two-phase static coordinate system, is the resistance of the stator winding.

[0010] Compared with the prior art, the present application has the following advantages:

[0011] The present application designs a high-speed permanent magnet synchronous motor position identification method, which obtains the position estimation reference quantity by directly processing the current and voltage, avoiding the chattering problem of using sliding film observer, and the present application uses the output characteristics of the voltage source inverter in the reference quantity calculation to obtain the calculation formula not affected by the discretization error, improving the position identification accuracy under low carrier frequency ratio. In the case of motor temperature or skin effect causing winding resistance change, the position identification accuracy of the present method is not affected. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is the overall flowchart of the method of the present application.

[0013] Figure 2 is the motor control block diagram applying the method of the present application (in the dashed box). DETAILED DESCRIPTION

[0014] The present application will be further described below in combination with the drawings and specific embodiments.

[0015] In combination with Figure 1 , Figure 2 , Figure 1 is the overall flowchart of the method of the present application, Figure 2 is the motor control block diagram applying the method of the present application (in the dashed box), and the variables marked in the figure are all sampling values. The position identification method of a high-speed permanent magnet synchronous motor of the present embodiment comprises the following steps:

[0016] Step 1: Current and voltage acquisition and transformation

[0017] Sample the three-phase current a, b, c of the motor , , The Clarke transformation of the obtained current gives the currents of the α-axis and the β-axis in the two-phase static coordinate system , The output voltage of the α-axis and the β-axis is estimated according to the SVPWM conduction time calculated in the last control period , .

[0018] Step two: calculate the position estimation reference

[0019] According to the relationship between the current, the voltage and the counter electromotive force of the hidden pole permanent magnet synchronous motor

[0020]

[0021] The following can be obtained

[0022]

[0023] Wherein, is the stator voltage in the two-phase static coordinate system, is the stator current in the two-phase static coordinate system, is the counter electromotive force in the two-phase static coordinate system, , respectively represent the counter electromotive force of the α-axis and the β-axis in the two-phase static coordinate system, is the inductance in the two-phase static coordinate system, is the resistance of the stator winding, is the differential factor.

[0024] From the above formula, the voltage is filtered through a low-pass filter , and the current is subtracted, that is, the value of the counter electromotive force filtered by the same filter is obtained. Select as the position estimation reference of the permanent magnet synchronous motor , and

[0025]

[0026] Under the SVPWM control of the voltage source inverter, the inverter outputs several voltage vectors to synthesize a specific output voltage in each control period. Because only the value of the parameter at the beginning of the control period is concerned in the control system, it can be approximately considered that the output voltage is constant in each control period. The discrete calculation formula of is obtained by solving the differential equation

[0027]

[0028] Wherein, is the sampling period, For the intermediate variable (initial value is 0), add after the variable to indicate the value of the variable at the kth sampling time.

[0029] Step three: phase-locked loop calculation of the angle and speed and thus calculate the motor position information

[0030] Using the phase-locked loop, the angle of and the speed (angular velocity) can be calculated Since the speed of change of the electrical parameters of the motor is much greater than the speed of change of the motor speed, it can be considered that the speed of the motor is basically unchanged within the time required for the phase-locked loop to converge, and from the definition of in step two , the relationship between and the permanent magnet flux of the motor

[0031]

[0032] where is the permanent magnet flux in the two-phase stationary coordinate system , represents the permanent magnet flux in the α-axis and β-axis of the two-phase stationary coordinate system, respectively is the imaginary unit.

[0033] Therefore, the motor rotor position and speed can be obtained by the following formula

[0034]

[0035]

[0036] The following will explain that when the permanent magnet motor uses d-axis command current vector control, the position recognition accuracy of the present method is not affected by the error of winding resistance R.

[0037] Let the measured winding resistance be ( ), at this time the definition is changed to (the position estimation reference quantity obtained by filtering the back EMF ):

[0038]

[0039] Since is also used when calculating , the calculated from ​is the real value.

[0040] The position estimation reference quantity calculated at this time (equivalent to The position estimation reference quantity obtained by filtering is

[0041]

[0042] According to the relationship between the two-phase synchronous coordinate system and the two-phase stationary coordinate system, we have

[0043]

[0044] where , , are the d-axis current, q-axis current and q-axis counter electromotive force in the two-phase synchronous coordinate system, respectively. Since the d-axis of the two-phase synchronous coordinate system is positioned along the flux linkage direction, the d-axis counter electromotive force in the two-phase synchronous coordinate system is 0.

[0045] Let the rotor angle identified at this time be ,

[0046]

[0047] Let the intermediate quantity , the above formula can be transformed into

[0048]

[0049] When there is an angle error , using the vector control of will adjust the measured current on the d-axis identified to 0, which will adjust the real d-axis current to at this time , so that , indicating that even if there is an error in the winding resistance, the position identification angle will still converge to the real value when the system is stable.

Claims

1. A high-speed permanent magnet synchronous motor position identification method, characterized in that, The motor rotor position is obtained by the following formula and rotational speed : wherein and are discretized position estimation reference quantities of the permanent magnet synchronous motor angle and speed calculated by a phase-locked loop, are inductances in a two-phase stationary coordinate system, are resistances of the stator windings.

2. The high-speed permanent magnet synchronous motor position identification method according to claim 1, characterized in that, Discretized position estimation reference for permanent magnet synchronous motor For: wherein, is a sampling period, is an intermediate variable, is the stator current in the two-phase stationary coordinate system at the kth sampling instant, is the stator voltage in the two-phase stationary coordinate system at the k-1th sampling instant.

3. The high-speed permanent magnet synchronous motor position identification method according to claim 1, characterized in that, The stator voltage in two-phase stationary coordinate system is obtained by the following formula: wherein is the counter EMF in the two-phase stationary coordinate system, , and respectively represent the counter EMF on the α-axis and β-axis of the two-phase stationary coordinate system.

4. The high-speed permanent magnet synchronous motor position identification method according to claim 1, characterized in that, The stator current in two-phase stationary coordinate system is obtained by Clarke transformation of sampling motor three-phase current.

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