Method and device for correcting position estimation of permanent magnet synchronous motor

Abstract

The position estimation correction method of the permanent magnet synchronous motor comprises the following steps: 1) acquiring current and voltage of the motor at a set rotating speed, and inputting the current and voltage into a back electromotive force observer to obtain back electromotive force; 2) in the current compensation period, correcting the back electromotive force according to the current compensation coefficient, inputting a phase-locked loop to estimate the position and the rotating speed of a motor rotor, and obtaining a torque instruction current; (3) entering the next compensation period, judging whether the compensation period is not finished or not, if so, adding a set compensation step length to the compensation coefficient of the previous compensation period to obtain the compensation coefficient of the current compensation period, and entering the step (2); if not, outputting a compensation coefficient corresponding to the minimum torque current; and 4) correcting the back electromotive force in the step 1) based on the compensation coefficient in the step 3) to obtain the corrected back electromotive force, and inputting the corrected back electromotive force into a phase-locked loop to estimate the actual position and rotating speed of the motor rotor at the set rotating speed. The rotor position estimation precision is improved.

Description

Technical Field

[0001] The present invention relates to the field of motor position estimation, and in particular to a correction method and device for position estimation of a permanent magnet synchronous motor. Background Art

[0002] The high-performance vector control of permanent magnet synchronous motors requires accurate rotor position and speed information, but the installation of mechanical sensors will increase system cost, size and weight, and have strict requirements on the use environment. Position sensorless control technology collects relevant electrical signals from the motor and builds a position observation model to estimate the rotor position and speed.

[0003] At present, according to the different speed adaptation ranges, they can be roughly divided into two categories: one method is a position estimation method suitable for starting / low-speed operation, including high-frequency signal injection method based on rotor salient pole characteristics, current-frequency ratio control and voltage-frequency ratio control, etc.; the other method is a model method suitable for medium and high-speed position sensorless control, that is, using the magnetic flux or back electromotive force information of fundamental frequency excitation to obtain the rotor speed and position.

[0004] In the development of medium and high speed sensorless control algorithms, the back-EMF model method is generally used to observe the rotor position in real time. The accuracy of the position observer based on the model method depends on the accuracy of the motor parameters. In actual applications, the motor parameters used in the position observer are constant values, but the actual motor parameters are affected by factors such as ambient temperature and working conditions, and will change greatly, ultimately affecting the accuracy of position estimation.

[0005] In addition, the accuracy of rotor position estimation is easily affected by non-ideal factors such as loop filter delay, current sampling deviation, inverter nonlinearity, and rotor magnetic field spatial harmonics. Summary of the invention

[0006] The main purpose of the present invention is to overcome the position estimation error caused by inaccurate motor parameters, control loop delay and other uncertain factors in the prior art, and to propose a correction method and device for position estimation of a permanent magnet synchronous motor to improve the accuracy of rotor position estimation.

[0007] The present invention adopts the following technical solution:

[0008] A correction method for position estimation of a permanent magnet synchronous motor, a motor vector control method based on speed closed-loop control controls the motor operation, sets a compensation interval of the compensation coefficient of the motor at a set speed, and the rest includes:

[0009] 1) Obtain the current and voltage of the motor in a two-phase stationary coordinate system at a set speed, and input them into the back electromotive force observer to obtain the back electromotive force;

[0010] 2) Under the current compensation cycle, the back electromotive force is corrected according to the current compensation coefficient to obtain a corrected back electromotive force, the corrected back electromotive force is input into a phase-locked loop to estimate the position and speed of the motor rotor, and the motor is controlled based on the estimated position and speed of the rotor to obtain the torque command current output by the speed loop of the motor;

[0011] 3) Entering the next compensation cycle, judging whether the compensation cycle has not ended according to the compensation interval, if so, increasing the compensation coefficient of the previous compensation cycle by the set compensation step length to obtain the compensation coefficient of the current compensation cycle, and entering step 2); if not, outputting the compensation coefficient of the compensation cycle corresponding to the minimum torque current as the compensation coefficient under the set speed;

[0012] 4) Based on the compensation coefficient at the set speed, the back electromotive force at the set speed in step 1) is corrected to obtain a corrected back electromotive force, and the corrected back electromotive force is input into a phase-locked loop to estimate the actual position and speed of the motor rotor at the set speed.

[0013] Set the compensation zone [m0, m1] of the compensation coefficient of the motor at the set speed, the current compensation cycle is k, △m is the compensation step length, and judge whether the compensation cycle has not ended according to the compensation interval, as follows:

[0014] judge If yes, it means the compensation cycle has not ended. The compensation coefficient of the previous compensation cycle is increased by the set compensation step size to obtain the compensation coefficient m of the current compensation cycle. s =m0+k△m; if not, it means the compensation cycle is over.

[0015] In step 2), in the current compensation cycle, the corrected back electromotive force for:

[0016]

[0017] in, is the back EMF before correction, is the estimated speed of the motor, T s is the control period, m s It is the compensation coefficient in the current replenishment cycle.

[0018] In step 4), the corrected back electromotive force for:

[0019]

[0020] in, is the back EMF before correction, is the estimated speed of the motor, T s is the control period, m s It is the compensation coefficient at the set speed.

[0021] A compensation interval of the compensation coefficient of the motor at rated speed is set, and the compensation coefficient at the rated speed is obtained through steps 1)-3); based on the compensation coefficient at the rated speed, the back electromotive force at the rated speed is corrected to obtain a corrected back electromotive force, and the corrected back electromotive force is input into a phase-locked loop to estimate the actual position and speed of the motor rotor at the rated speed.

[0022] According to the compensation coefficient at the rated speed, the compensation interval of the compensation coefficient at other speeds is set, and then the compensation coefficient at the other speeds is obtained through steps 1) to 3), and the back electromotive force at the other speeds is corrected based on the compensation coefficient at the other speeds to obtain the corrected back electromotive force, and the corrected back electromotive force is input into a phase-locked loop to estimate the actual position and speed of the motor rotor at the other speeds.

[0023] The compensation interval [m s -△

[0024] m s ,m s +△m s ],△m s is the set interval value, m s is the compensation coefficient at rated speed.

[0025] A correction device for position estimation of a permanent magnet synchronous motor, comprising:

[0026] An acquisition module is used to acquire the voltage and current of the motor in a two-phase stationary coordinate system at a set speed, as well as the torque command current output by the speed loop of the motor;

[0027] A back electromotive force observer, which obtains the back electromotive force at the set speed according to the voltage and the current in the two-phase stationary coordinate system;

[0028] A compensation module, which sets a compensation interval corresponding to the set speed, increases the compensation coefficient of the previous compensation cycle by a set compensation step length every same compensation cycle to obtain a compensation coefficient of the current compensation cycle and records the torque command current, and uses the compensation coefficient of the compensation cycle corresponding to the minimum torque command current as the compensation coefficient of the set speed;

[0029] A correction module, which corrects the back electromotive force according to a compensation coefficient of the set speed;

[0030] The phase-locked loop estimates the actual position and speed of the motor rotor at the set speed according to the corrected back electromotive force.

[0031] The compensation module searches for the compensation coefficient of the set speed, specifically comprising the following steps:

[0032] Step a: In the current compensation cycle, the back electromotive force is corrected according to the current compensation coefficient to obtain a corrected back electromotive force, the corrected back electromotive force is input into a phase-locked loop to estimate the position and speed of the motor rotor, and the motor is controlled based on the estimated position and speed of the rotor to obtain the torque command current output by the speed loop of the motor;

[0033] Step b enters the next compensation cycle, and determines whether the compensation cycle has not ended according to the compensation interval. If so, the compensation coefficient of the previous compensation cycle is increased by the set compensation step to obtain the compensation coefficient of the current compensation cycle, and enters step a; if not, the compensation coefficient of the compensation cycle corresponding to the minimum torque current is output as the compensation coefficient under the set speed.

[0034] A compensation interval of the compensation coefficient of the motor at the rated speed is set, and the compensation coefficient at the rated speed is obtained through a step compensation module; the back electromotive force at the rated speed is corrected based on the compensation coefficient at the rated speed to obtain a corrected back electromotive force, and the corrected back electromotive force is input into the phase-locked loop to estimate the actual position and speed of the motor rotor at the rated speed.

[0035] It can be seen from the above description of the present invention that, compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The method and device of the present invention set the compensation interval and compensation period, adaptively obtain the compensation coefficient by tracking the minimum torque command current, correct the back electromotive force observed by the back electromotive force observer based on the compensation coefficient, and use a phase-locked loop to estimate the position of the rotor based on the corrected back electromotive force, thereby effectively improving the accuracy of rotor position estimation.

[0037] 2. The method and device of the present invention meet the requirements of adaptive compensation time and speed by reasonably setting the compensation step size and controlling the compensation cycle while ensuring the stability of the vector control system.

[0038] 3. The method and device of the present invention, under rated speed conditions, set a slightly larger compensation interval to perform back electromotive force adaptive phase deviation correction, find the compensation coefficient corresponding to the minimum torque current, and use the compensation coefficient as the compensation reference value; considering that the compensation coefficient changes less under different speed conditions, when adaptively compensating the position at other speeds, a smaller error compensation interval can be set based on the compensation reference value to achieve fast position error compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The flowchart of adaptively obtaining compensation coefficients of the present invention;

[0040] Figure 2 The torque command current relationship when there is a position estimation error in the present invention;

[0041] Figure 3 A flowchart of obtaining compensation coefficients for different speeds of the present invention;

[0042] Figure 4 It is the principle diagram of the device of the present invention.

[0043] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. DETAILED DESCRIPTION

[0044] The present invention is further described below through specific implementation modes.

[0045] See also Figure 1 , a correction method for position estimation of a permanent magnet synchronous motor, a motor vector control method based on speed closed-loop control, i.e., FOC control algorithm, is used to control the operation of the motor. The compensation interval [m0, m1] of the compensation coefficient of the motor at a set speed is pre-set, for example, to [-1, 1], and the remaining steps include the following:

[0046] 1) Obtain the current and voltage of the motor in a two-phase stationary coordinate system at a set speed, and input them into the back-EMF observer to obtain the back-EMF. The back-EMF is the induced electromotive force generated when the motor rotor magnetic field moves relative to the stator winding. Its amplitude and frequency are directly related to the rotor position and speed. The back-EMF observer monitors the stator current and voltage of the motor in real time when it is running, and calculates the back-EMF signal corresponding to the motor rotor position based on the mathematical model of the motor.

[0047] 2) In the current compensation cycle, the back electromotive force is corrected according to the current compensation coefficient to obtain the corrected back electromotive force, and the corrected back electromotive force is input into the phase-locked loop to estimate the position and speed of the motor rotor. Based on the estimated rotor position and speed, the motor is controlled to operate and the torque command current output by the motor's speed loop is obtained.

[0048] In this embodiment, the number of compensation cycles is preset. It is assumed that the current compensation cycle is k and the next compensation cycle is k+1. The duration of each compensation cycle is the same. The actual duration of the compensation cycle should not be too small or too large. If it is too small, the vector control system will become unstable, and if it is too large, the adaptive compensation speed will be too slow. △m is the compensation step length. The compensation step length should not be too small or too large. Although a small compensation step length improves the compensation accuracy, the time required for adaptive compensation will be longer. Although a large compensation step length improves the compensation accuracy, the optimal compensation coefficient may not be found, and it may also cause excessive steady-state jitter.

[0049] The initial value of the compensation coefficient can be set according to the actual situation and made within the set compensation interval. In this embodiment, the initial value of the supplementary coefficient is taken as the lower limit value of the compensation interval.

[0050] In the current compensation cycle, the corrected back electromotive force for:

[0051]

[0052] in, is the back EMF before correction, is the estimated motor speed, T s is the control period, m s It is the compensation coefficient in the current replenishment cycle.

[0053] Controlling the operation of the motor based on the estimated rotor position and speed and obtaining the torque command current output by the speed loop of the motor refers to using the FOC control algorithm to control the operation of the motor based on the estimated rotor position and speed and obtaining the torque command current output by the speed loop when the motor is working.

[0054] 3) Enter the next compensation cycle, and determine whether the compensation cycle has not ended according to the compensation interval. If so, increase the compensation coefficient of the previous compensation cycle by the set compensation step to obtain the compensation coefficient of the current compensation cycle, and enter step 2); if not, output the compensation coefficient of the compensation cycle corresponding to the minimum torque command current as the compensation coefficient at the set speed.

[0055] In this embodiment, judging whether the compensation period has not ended according to the compensation interval specifically includes the following:

[0056] judge If yes, it means the compensation cycle has not ended. The compensation coefficient of the previous compensation cycle is increased by the set compensation step size to obtain the compensation coefficient m of the current compensation cycle. s =m0+k△m; if not, it means the compensation cycle is over.

[0057] in, Represents the maximum number of compensation cycles calculated based on the compensation interval and compensation step. When , it means that the maximum number of compensation cycles has not been reached and it is necessary to enter the next compensation cycle; Indicates the maximum number of times the current compensation period exceeds the compensation period.

[0058] See also Figure 2 Based on the speed closed-loop vector control, under the same load conditions, when the estimated rotor position has no error, the torque command current is the minimum; when there is an error in the estimated rotor position, the required torque command current will become larger, and the larger the error, the larger the torque command current. Figure 2 shown.

[0059] Based on this principle, the present invention adaptively obtains the compensation coefficient m by tracking the minimum torque command current. s , and then obtain an accurate estimated rotor position. Specifically, each compensation cycle may have a corresponding compensation coefficient and torque command current, multiple compensation cycles may correspond to multiple compensation coefficients and multiple torque command currents, and multiple torque command currents are compared, and the compensation coefficient of the compensation cycle corresponding to the minimum torque command current is used as the compensation coefficient under the set speed.

[0060] 4) Based on the compensation coefficient at the set speed, the back electromotive force at the set speed in step 1) is corrected to obtain a corrected back electromotive force, and the corrected back electromotive force is input into a phase-locked loop to estimate the actual position and speed of the motor rotor at the set speed.

[0061] In this step, the compensation coefficient at the set speed obtained in step 3) is used to correct the back electromotive force at the set speed. for:

[0062]

[0063] in, is the back EMF before correction, is the estimated motor speed, T s is the control period, m s It is the compensation coefficient at the set speed.

[0064] In this embodiment, see Figure 3 In order to achieve error compensation at various speeds, the compensation interval of the compensation coefficient of the motor at the rated speed is first set, and the compensation coefficient at the rated speed is obtained through steps 1)-3). The back electromotive force at the rated speed is corrected based on the compensation coefficient at the rated speed to obtain the corrected back electromotive force, and the corrected back electromotive force is input into the phase-locked loop to estimate the actual position and speed of the motor rotor at the rated speed.

[0065] Afterwards, the compensation coefficient at the rated speed is used as the compensation reference value. Considering that the compensation coefficient changes less under different speed conditions, when adaptively compensating the position at other speeds, a smaller error compensation interval can be set based on the compensation reference value to achieve fast position error compensation. That is, the compensation interval of the compensation coefficient at other speeds is set according to the compensation reference value, and then the compensation coefficient at other speeds is obtained through steps 1) to 3), and the back electromotive force at other speeds is corrected based on the compensation coefficient at other speeds to obtain the corrected back electromotive force, and the corrected back electromotive force is input into the phase-locked loop to estimate the actual position and speed of the motor rotor at other speeds.

[0066] Specifically, the compensation interval of the compensation coefficient at other speeds is set according to the compensation coefficient at the rated speed [m s -△m s ,m s +△m s ],△m s is the set interval value (for example, 0.1), m s is the compensation coefficient at rated speed.

[0067] Based on this, the present invention further proposes a correction device for position estimation of a permanent magnet synchronous motor, which is used to implement the correction method for position estimation of a permanent magnet synchronous motor, comprising:

[0068] The acquisition module is used to collect the voltage and current of the motor in the two-phase stationary coordinate system at the set speed, as well as the torque command current output by the motor's speed loop. Figure 4 , where u αβ 、i αβ Represent the voltage and current of the two-phase stationary coordinate system respectively, Represent the voltage and current after coordinate transformation respectively.

[0069] The back electromotive force observer obtains the back electromotive force at a set speed according to the voltage and current obtained after coordinate transformation of the voltage and current in the two-phase stationary coordinate system. Figure 4 middle, is the back EMF output by the back EMF observer.

[0070] The compensation module sets the compensation interval corresponding to the set speed. Every same compensation cycle, the compensation coefficient of the previous compensation cycle is increased by the set compensation step to obtain the compensation coefficient of the current compensation cycle and record the torque command current. The compensation coefficient of the compensation cycle corresponding to the minimum torque command current is used as the compensation coefficient of the set speed.

[0071] The correction module corrects the back electromotive force according to the compensation coefficient of the set speed. The correction module corrects the back electromotive force using the calculation formula: in, is the corrected back EMF, is the back EMF before correction, is the estimated motor speed, T s is the control period, m s It is the compensation coefficient at the set speed.

[0072] The phase-locked loop estimates the actual position and speed of the motor rotor at a set speed based on the corrected back-EMF.

[0073] The compensation module searches for the compensation coefficient of the set speed, which specifically includes the following steps:

[0074] Step a: In the current compensation cycle, the back electromotive force is corrected according to the current compensation coefficient to obtain a corrected back electromotive force, the corrected back electromotive force is input into a phase-locked loop to estimate the position and speed of the motor rotor, the motor is controlled based on the estimated rotor position and speed, and the torque command current output by the speed loop of the motor is obtained;

[0075] Step b enters the next compensation cycle, and determines whether the compensation cycle has not ended according to the compensation interval. If so, the compensation coefficient of the previous compensation cycle is increased by the set compensation step to obtain the compensation coefficient of the current compensation cycle, and enters step a; if not, the compensation coefficient of the compensation cycle corresponding to the minimum torque current is output as the compensation coefficient at the set speed.

[0076] A compensation interval of the compensation coefficient of the motor at the rated speed is set, and the compensation coefficient at the rated speed is obtained through the compensation module; the back electromotive force at the rated speed is corrected based on the compensation coefficient at the rated speed to obtain the corrected back electromotive force, and the corrected back electromotive force is input into the phase-locked loop to estimate the actual position and speed of the motor rotor at the rated speed.

[0077] The device of this embodiment adopts step 1) to step 4) of the above-mentioned method for correcting the position estimation of a permanent magnet synchronous motor to realize the correction of the position estimation of the permanent magnet synchronous motor.

[0078] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A method for correcting position estimation of a permanent magnet synchronous motor, a motor vector control method based on speed closed-loop control to control the motor operation, characterized in that: Set the compensation range of the compensation coefficient of the motor at the set speed. The rest include: 1) Obtain the current and voltage of the motor in a two-phase stationary coordinate system at a set speed, and input them into the back electromotive force observer to obtain the back electromotive force; 2) Under the current compensation cycle, the back electromotive force is corrected according to the current compensation coefficient to obtain a corrected back electromotive force, the corrected back electromotive force is input into a phase-locked loop to estimate the position and speed of the motor rotor, and the motor is controlled based on the estimated position and speed of the rotor to obtain the torque command current output by the speed loop of the motor; 3) Entering the next compensation cycle, judging whether the compensation cycle has not ended according to the compensation interval, if so, increasing the compensation coefficient of the previous compensation cycle by the set compensation step length to obtain the compensation coefficient of the current compensation cycle, and entering step 2); if not, outputting the compensation coefficient of the compensation cycle corresponding to the minimum torque current as the compensation coefficient under the set speed; 4) Based on the compensation coefficient at the set speed, the back electromotive force at the set speed in step 1) is corrected to obtain a corrected back electromotive force, and the corrected back electromotive force is input into a phase-locked loop to estimate the actual position and speed of the motor rotor at the set speed.

2. A method for correcting position estimation of a permanent magnet synchronous motor as claimed in claim 1, characterized in that: Set the compensation zone [m0, m1] of the compensation coefficient of the motor at the set speed, the current compensation cycle is k, △m is the compensation step length, and judge whether the compensation cycle has not ended according to the compensation interval, as follows: judge If yes, it means the compensation cycle has not ended. The compensation coefficient of the previous compensation cycle is increased by the set compensation step size to obtain the compensation coefficient m of the current compensation cycle. s =m0+k△m; if not, it means the compensation cycle is over.

3. A method for correcting position estimation of a permanent magnet synchronous motor as claimed in claim 1, characterized in that: In step 2), in the current compensation cycle, the corrected back electromotive force for: in, is the back EMF before correction, is the estimated speed of the motor, T s is the control period, m s It is the compensation coefficient in the current replenishment cycle.

4. A method for correcting position estimation of a permanent magnet synchronous motor as claimed in claim 1, characterized in that: In step 4), the corrected back electromotive force for: in, is the back EMF before correction, is the estimated speed of the motor, T s is the control period, m s It is the compensation coefficient at the set speed.

5. A method for correcting position estimation of a permanent magnet synchronous motor as claimed in claim 1, characterized in that: A compensation interval of the compensation coefficient of the motor at rated speed is set, and the compensation coefficient at the rated speed is obtained through steps 1)-3); based on the compensation coefficient at the rated speed, the back electromotive force at the rated speed is corrected to obtain a corrected back electromotive force, and the corrected back electromotive force is input into a phase-locked loop to estimate the actual position and speed of the motor rotor at the rated speed.

6. A method for correcting position estimation of a permanent magnet synchronous motor as claimed in claim 5, characterized in that: According to the compensation coefficient at the rated speed, the compensation interval of the compensation coefficient at other speeds is set, and then the compensation coefficient at the other speeds is obtained through steps 1) to 3), and the back electromotive force at the other speeds is corrected based on the compensation coefficient at the other speeds to obtain the corrected back electromotive force, and the corrected back electromotive force is input into a phase-locked loop to estimate the actual position and speed of the motor rotor at the other speeds.

7. A method for correcting position estimation of a permanent magnet synchronous motor as claimed in claim 6, characterized in that: The compensation interval [m s -△m s ,m s +△m s ],△m s is the set interval value, m s is the compensation coefficient at rated speed.

8. A correction device for position estimation of a permanent magnet synchronous motor, characterized in that: include: An acquisition module is used to acquire the voltage and current of the motor in a two-phase stationary coordinate system at a set speed, as well as the torque command current output by the speed loop of the motor; A back electromotive force observer, which obtains the back electromotive force at the set speed according to the voltage and the current in the two-phase stationary coordinate system; A compensation module, which sets a compensation interval corresponding to the set speed, increases the compensation coefficient of the previous compensation cycle by a set compensation step length every same compensation cycle to obtain a compensation coefficient of the current compensation cycle and records the torque command current, and uses the compensation coefficient of the compensation cycle corresponding to the minimum torque command current as the compensation coefficient of the set speed; A correction module, which corrects the back electromotive force according to a compensation coefficient of the set speed; The phase-locked loop estimates the actual position and speed of the motor rotor at the set speed according to the corrected back electromotive force.

9. A correction device for position estimation of a permanent magnet synchronous motor as claimed in claim 8, characterized in that: The compensation module searches for the compensation coefficient of the set speed, specifically comprising the following steps: Step a: In the current compensation cycle, the back electromotive force is corrected according to the current compensation coefficient to obtain a corrected back electromotive force, the corrected back electromotive force is input into a phase-locked loop to estimate the position and speed of the motor rotor, and the motor is controlled based on the estimated position and speed of the rotor to obtain the torque command current output by the speed loop of the motor; Step b enters the next compensation cycle, and determines whether the compensation cycle has not ended according to the compensation interval. If so, the compensation coefficient of the previous compensation cycle is increased by the set compensation step length to obtain the compensation coefficient of the current compensation cycle, and then enters step a; If not, the compensation coefficient of the compensation period corresponding to the minimum torque current is output as the compensation coefficient under the set speed.

10. A position estimation correction device for a permanent magnet synchronous motor as claimed in claim 9, characterized in that: A compensation interval of the compensation coefficient of the motor at the rated speed is set, and the compensation coefficient at the rated speed is obtained through a step compensation module; the back electromotive force at the rated speed is corrected based on the compensation coefficient at the rated speed to obtain a corrected back electromotive force, and the corrected back electromotive force is input into the phase-locked loop to estimate the actual position and speed of the motor rotor at the rated speed.

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