Permanent magnet auxiliary synchronous reluctance motor sensorless control method capable of effectively reducing high-frequency torque ripple

Abstract

The invention discloses a permanent magnet auxiliary synchronous reluctance motor sensorless control method capable of effectively reducing high-frequency torque pulsation. Aiming at high-frequency torque ripple caused by a traditional high-frequency signal injection method, by changing the high-frequency signal injection direction, under MTPA control, a corresponding high-frequency response current vector is tangent to a constant torque curve, and the high-frequency torque ripple can be effectively reduced. In order to solve the problem of position estimation errors caused by cross coupling, the rotor position is estimated through a phase-locked loop after the d-axis inductance Ld, the q-axis inductance Lq and the dq-axis mutual inductance Ldq which are measured in an offline mode are combined to be processed, and the influence of the cross coupling effect on position estimation is eliminated.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of electric transmission, in particular to a permanent magnet auxiliary synchronous reluctance motor position sensorless control method capable of effectively reducing high-frequency torque pulsation. BACKGROUND

[0002] Permanent magnet synchronous motors have been widely applied due to small size, light weight and high efficiency, but are prone to demagnetization under complex working conditions such as high temperature. The synchronous reluctance motor has the advantages of high efficiency and simple control, and the rotor is free of permanent magnets, thus avoiding the risk of demagnetization, but the magnetic field must be established through a certain current, so the power factor is low. By embedding a weak magnetic ferrite in the rotor barrier of the synchronous reluctance motor to establish an auxiliary magnetic field, the low power factor of the synchronous reluctance motor is overcome, and the manufacturing cost and high-temperature demagnetization risk of the motor are greatly reduced. This kind of motor is called permanent magnet auxiliary synchronous reluctance motor. The traditional vector control system uses mechanical sensors to obtain rotor position and speed information, which increases the cost and reduces the reliability, so the permanent magnet auxiliary synchronous reluctance motor position sensorless control has high research significance.

[0003] The high-frequency signal injection method is widely used in low-speed position sensorless control due to the characteristics of not depending on motor parameters and not needing back electromotive force. However, when the load is large and the cross-coupling effect is strong, the traditional high-frequency signal injection method will produce a large position estimation error, which seriously affects the operation performance. At the same time, due to the injection of an additional high-frequency signal, various adverse effects will be caused to the system, such as increased loss, electromagnetic noise, etc., especially the high-frequency signal injection will produce a large high-frequency current, thereby causing a large high-frequency torque pulsation.

[0004] In view of the above problems, the application designs a permanent magnet auxiliary synchronous reluctance motor position sensorless control method capable of effectively reducing high-frequency torque pulsation, which can accurately estimate the rotor position and greatly reduce the high-frequency torque pulsation. SUMMARY

[0005] The application aims to provide a permanent magnet auxiliary synchronous reluctance motor position sensorless control method capable of effectively reducing high-frequency torque pulsation. In view of the high-frequency torque pulsation caused by the traditional high-frequency signal injection method, the direction of the injected high-frequency signal is changed, and under MTPA control, the corresponding high-frequency current vector is along the tangent direction of the torque contour, so that the torque pulsation can be greatly reduced. In view of the position estimation error caused by cross-coupling, the d-axis inductance L d , q-axis inductance L q and dq-axis mutual inductance L dq are combined with the measured d-axis current id and q-axis current iq to calculate the rotor position, so that the position estimation error caused by cross-coupling can be greatly reduced. After processing, the rotor position is estimated through a phase-locked loop, which can eliminate the influence of cross-coupling effect on position estimation.

[0006] The technical solution to achieve the purpose of this invention is: a sensorless control method for a permanent magnet assisted synchronous reluctance motor that effectively reduces high-frequency torque ripple, comprising the following steps:

[0007] S1: Constructing a sensorless vector control system for a permanent magnet assisted synchronous reluctance motor based on a high-frequency square wave injection method. The high-frequency square wave voltage signal is estimated in the synchronous rotating coordinate system. axis α M Angle injection, based on the detection of three-phase stator current, yields an estimated fundamental frequency current in the synchronous rotating coordinate system. and high frequency current

[0008] S2: Combining α M And the d-axis inductance L measured offline d q-axis inductance L q dq axis mutual inductance L dq right After processing, the estimated rotor position is obtained using a phase-locked loop. This eliminates the impact of cross-coupling on estimation accuracy while reducing torque ripple caused by high-frequency signal injection.

[0009] Compared with the prior art, the significant advantages of this invention are:

[0010] 1) By changing the direction of the injected high-frequency signal, the high-frequency current vector under MTPA control is made to follow the tangent direction of the torque contour line, which greatly reduces the torque pulsation caused by the injection of additional signal.

[0011] 2) Combined with the offline measured d-axis inductance L d q-axis inductance L q dq axis mutual inductance L dq right After processing, the rotor position is estimated through a phase-locked loop, thus eliminating the influence of cross-coupling effect on position estimation. Attached Figure Description

[0012] Figure 1 This is the overall control block diagram of the present invention.

[0013] Figure 2 This is a schematic diagram of a filterless separation of fundamental frequency and high-frequency current.

[0014] Figure 3 This is a schematic diagram showing the positional relationship between the stationary coordinate system, the actual synchronous rotating coordinate system, the estimated synchronous rotating coordinate system, and the injection position of the high-frequency square wave voltage signal.

[0015] Figure 4 The figure shows the maximum torque current ratio operating point.

[0016] Figure 5 The figure shows the principle of the observer. DETAILED DESCRIPTION

[0017] The application will be described in further detail below with reference to the drawings.

[0018] Figure 1 The figure shows the vector control block diagram of the proposed sensorless control of permanent magnet assisted synchronous reluctance machine which effectively reduces the high frequency torque ripple, which can be divided into two steps: first, from the estimated synchronous rotating coordinate system Axis α M The angle injects a high frequency square wave voltage signal, and the method shown is used to obtain the fundamental frequency current Figure 2 and the high frequency current in the estimated synchronous rotating coordinate system Combined with α M and the offline measured d-axis inductance L d , q-axis inductance L q , dq-axis mutual inductance L dq , the processing of is used to obtain the estimated rotor position

[0019] First, the mathematical model of the permanent magnet assisted synchronous reluctance machine in the low speed condition is established, and the high frequency signal is injected:

[0020]

[0021] In equation (1), L d and L q are the dq-axis inductances, L dq and L qd are the dq-axis mutual inductances, and L dq and L qd are usually considered to be equal. u dh , u qh , i dh , i qh represent the high frequency voltage and current on the dq-axis, respectively.

[0022] According to the equation shown in Figure 3 , the injected voltage signal is transformed to the estimated synchronous rotating coordinate system axis:

[0023]

[0024] In equation (2), i and i are the estimated synchronous rotating coordinate system The high-frequency voltage signal of the shaft, α M To estimate the injection direction of high-frequency square wave voltage in a synchronous rotating coordinate system The included angle of the axis, V i Let n be the amplitude of the injected square wave voltage, and n be the discrete sampling time.

[0025] Then The voltage signal on the axis is transformed into the actual synchronous rotating coordinate system dq:

[0026]

[0027] In equation (3), To estimate the angle of the actual synchronous rotating coordinate system in advance,

[0028] Substituting equation (3) into equation (1) yields the high-frequency current response of the actual synchronous rotating coordinate system:

[0029]

[0030] Transform the high-frequency current in the actual synchronous rotating coordinate system to the estimated synchronous rotating coordinate system:

[0031]

[0032] Therefore, the envelope of the high-frequency response current signal in the synchronous rotating coordinate system can be estimated as follows:

[0033]

[0034] In formula (6) To estimate the high-frequency response current envelope in the synchronous rotating coordinate system; ΔT is the period of the high-frequency square wave voltage. It can be seen that equation (6) includes the current envelope generated by α. M Therefore, traditional signal demodulation algorithms based on q-axis current response are no longer applicable. The demodulation algorithm proposed in this paper requires the use of α M α is given below M The calculation formula and basis are as follows: Figure 4 As shown, when no high-frequency square wave voltage is injected, the motor operates stably at the MTPA operating point, which is point B in the figure. At this time, the current vector is vector OB, and there is no high-frequency torque pulsation. With the injection of high-frequency square wave voltage, the motor will generate a high-frequency response current, which is represented by i in the current plane. d and i q The periodic change. At this time, by i d and i qThe synthesized current vector oscillates periodically around the fundamental current vector OB. The maximum amplitude of the positive oscillation is defined as the current vector OC, and the maximum amplitude of the negative oscillation is defined as the current vector OA. Since we are concerned with the peak-to-peak value of the torque ripple, we only consider the maximum amplitude of the current oscillation in the positive and negative directions. We then define the current vector i on the current plane... d and i q The periodically changing trajectory is defined as the current fluctuation trajectory, i.e., trajectories BC and BA. The angle between the current fluctuation trajectory and the positive d-axis is defined as λ. When the current fluctuation trajectory is tangent to the constant torque curve, i.e., λ and β... M When they are equal, the high-frequency torque ripple is minimized. The following gives α. M The calculation formula, when hour:

[0035]

[0036] In equation (8), β M =θ MTPA -π / 2, θ MTPA The angle between the stator current vectors under MTPA control.

[0037] As can be seen from equation (6), when the high-frequency square wave voltage injection angle is α M At that time, the rotor position estimation error in the high-frequency response current envelope of both the d-axis and q-axis is related to the injection angle α. M Due to coupling, it cannot be directly extracted. Here, the high-frequency response current envelopes of the d-axis and q-axis are projected onto the direction perpendicular to the injection angle:

[0038]

[0039] In equation (9), P represents the projection of the high-frequency response current envelope onto the direction perpendicular to the injection angle. Parameters A and B can be calculated, and the required inductance value can be obtained by looking up a table based on the current operating conditions. After the above transformation, Already with α M Separating the two positions, when the position error is sufficiently small, the position error can be approximated as:

[0040]

[0041] like Figure 5 As shown, after obtaining the position error, a phase-locked loop can be used to control it to 0, thereby achieving sensorless control.

Claims

1. A sensorless control method for a permanent magnet assisted synchronous reluctance motor that effectively reduces high-frequency torque ripple, characterized in that, Includes the following steps: S1: Constructing a sensorless vector control system for a permanent magnet assisted synchronous reluctance motor based on a high-frequency square wave injection method. The high-frequency square wave voltage signal is estimated in the synchronous rotating coordinate system. axis α M Angle injection, based on the detection of three-phase stator current, yields an estimated fundamental frequency current in the synchronous rotating coordinate system. and high frequency current S2: Combining α M And the d-axis inductance L measured offline d q-axis inductance L q dq axis mutual inductance L dq right After processing, the estimated rotor position is obtained using a phase-locked loop. This eliminates the impact of cross-coupling on estimation accuracy while reducing torque ripple caused by high-frequency signal injection.

2. The sensorless control method for a permanent magnet assisted synchronous reluctance motor that effectively reduces high-frequency torque ripple according to claim 1, characterized in that: In step S1, the sensorless vector control system uses the estimated rotor position. With the estimated rotational speed As for speed feedback, the control strategy employs maximum torque-to-current ratio control. α M Stator current vector angle θ under MTPA control MTPA and L d L q L dq Calculations show that, through α M Transform the square wave voltage signal to the estimated synchronous rotating coordinate system. The fundamental frequency current is injected after being superimposed on the fundamental voltage in the shaft. A filterless separation method is used to obtain the fundamental frequency current from the acquired three-phase currents. and high frequency current 3. The sensorless control method for a permanent magnet assisted synchronous reluctance motor to effectively reduce high-frequency torque ripple according to claim 1, characterized in that: In step S2, combined with α M And the d-axis inductance L measured offline d q-axis inductance L q dq axis mutual inductance L dq right After processing, the estimated rotor position can be obtained using a phase-locked loop. and estimate electric angular velocity

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