Low-speed synchronous motor sensorless control method for rotating square wave voltage injection

Abstract

The invention discloses a low-speed synchronous motor position sensorless control method for rotating square wave voltage injection, and relates to the technical field of motor control. The invention aims to solve the problems that the existing position sensorless control method needs motor parameters for parameter setting, and the introduction of a filter limits the bandwidth of a system, so that the dynamic performance of the system is reduced; and the ellipse fitting technology reduces the dynamic performance. The method comprises the following steps: injecting a rotating square wave voltage into a gamma-delta axis of the low-speed synchronous reluctance motor to obtain high-frequency induction current of an alpha-beta axis, and constructing an elliptical orbit equation based on the high-frequency induction current; reconstructing the high-frequency induction current, and compensating the current elliptic orbit distortion by using the reconstructed current; estimating a coefficient of the elliptic trajectory equation by applying a least square method; performing sine and cosine angle processing on the included angle # imgabs0 # between the deqe and the alpha-beta coordinate system; and estimating the position and speed of the rotor by adopting Q-PLL, and realizing sensorless control of the low-speed synchronous reluctance motor by utilizing the estimated values of the position and speed of the rotor.

Description

Technical Field

[0001] The invention belongs to the technical field of motor control. Background Art

[0002] Synchronous reluctance motor (SynRM) has the characteristics of simple structure, low cost and strong overload capacity. It has been widely used in industrial drive and electric vehicle applications in recent years. Accurate rotor position is the key to achieve high-performance synchronous motor control. However, the application of position sensors increases the cost, so it is of practical significance to study its position sensorless control method.

[0003] At present, the main position sensorless control methods are observer-based methods and high-frequency injection-based methods. The observer-based method obtains position information by estimating the stator flux or extended back electromotive force (EEMF). However, the stator flux estimation is affected by the insufficient signal-to-noise ratio when the motor is running at low speed, and the amplitude of the EEMF is proportional to the rotor speed. Therefore, the observer method is suitable for medium and high speed areas.

[0004] In order to expand the speed range of position sensorless control, a method based on high-frequency injection has been proposed. The method based on high-frequency injection extracts the rotor position by observing the high-frequency induced current caused by the high-frequency injection signal through an observer. However, the demodulation of high-frequency current inevitably introduces a specific filter, which complicates the system and reduces the dynamic performance. In addition, in order to obtain excellent control performance, the observer parameters need to be accurately designed according to the motor parameters. However, when the motor parameters change, especially when the inductance parameters change due to magnetic saturation, the observer parameters are mismatched, causing the system bandwidth to change and reducing the dynamic performance of the controller.

[0005] In recent years, ellipse fitting technology has been applied to position sensorless control due to its advantages such as easy parameter tuning and no need for motor parameters. This method injects a rotating voltage vector into the stator winding and estimates the rotor position based on the spatial relationship between the long semi-axis of the elliptical high-frequency induced current trajectory and the rotor direct axis. In order to extract the high-frequency elliptical current trajectory, the current method needs to introduce a high-pass filter in the signal demodulation, which reduces the dynamic performance of the control system.

[0006] Based on the introduction of the above background technology, it can be seen that the current position sensorless control method requires motor parameters for parameter tuning, and the introduction of filters limits the system bandwidth, resulting in a decrease in the dynamic performance of the system. Although the existing ellipse fitting technology avoids the need for motor parameters to tune the controller, if the filter is not introduced, the general formula of the ellipse equation whose center is not at the origin must be used. The equation is relatively complex and the amount of estimated parameter calculation is large. Although the introduction of the filter simplifies the general formula of the equation, it reduces the dynamic performance. Summary of the invention

[0007] The present invention aims to solve the problems that the existing position sensorless control method requires motor parameters for parameter setting, the introduction of filters limits the system bandwidth, and causes a decrease in the dynamic performance of the system; and the ellipse fitting technology reduces the dynamic performance. A position sensorless control method for a low-speed synchronous reluctance motor based on rotating square wave voltage injection is now provided.

[0008] A method for controlling a low-speed synchronous reluctance motor without a position sensor based on rotating square wave voltage injection comprises:

[0009] Injecting a rotating square wave voltage into the γδ axis of the low-speed synchronous reluctance motor to obtain a high-frequency induced current of the αβ axis, and constructing an elliptical trajectory equation based on the high-frequency induced current;

[0010] Reconstructing the high-frequency induced current of the αβ axis, and using the reconstructed current signal to compensate for the current elliptical trajectory distortion caused by non-zero speed in the historical cycle and the current cycle;

[0011] According to the compensated current, the coefficients of the elliptical trajectory equation are estimated by using the least square method;

[0012] Using the estimated values ​​of the coefficients of the ellipse trajectory equation to calculate d e q e Angle with αβ coordinate system Perform sine and cosine angle processing, the d e q e The coordinate system is the magnetic salient pole coordinate system;

[0013] Based on the angle and d axis and d e The angle between the axes θ m , Q-PLL is used to estimate the rotor position and speed, and the estimated values ​​of the rotor position and speed are used to realize position sensorless control of the low-speed synchronous reluctance motor.

[0014] Furthermore, the above-mentioned injecting a rotating square wave voltage into the γδ axis of the low-speed synchronous reluctance motor to obtain a high-frequency induced current of the αβ axis includes:

[0015] The expression of the rotating square wave voltage is:

[0016]

[0017] Among them, u αh and u βh are the high-frequency injection voltages of the α and β axes respectively, n is the voltage injection period, ω inj is the angular velocity of the γδ axis, T s is the PWM signal period, T(·) is the coordinate transformation matrix, uγδh is the rotating square wave voltage vector injected into the γδ axis, U h is the amplitude of the rotating square wave voltage injected into the γδ axis, and k is the control period;

[0018] The expression of the high frequency induced current of the αβ axis is:

[0019]

[0020] Among them, p is the differential operator, i αh and i βh are the high frequency induced currents of the α and β axes respectively, and They are d e and q e The differential inductance of the axis, θ inj is the angle between the α axis and the γ axis, θ e is the α axis and d e The angle between the axes, l Σ is the average value of dq axis inductance, l Δ is the half difference of dq axis inductance.

[0021] Furthermore, the above-mentioned construction of the elliptical trajectory equation includes:

[0022] The expression of the elliptical trajectory equation is:

[0023] A(pi αh ) 2 +Bpi αh pi βh +C(pi βh ) 2 =1,

[0024] Among them, A, B, and C are the coefficients of the elliptical trajectory equation.

[0025] Furthermore, the above-mentioned reconstruction of the high-frequency induced current of the αβ axis includes:

[0026] The reconstructed equation for the high-frequency induced current signal is:

[0027]

[0028] Among them, I αβh The high-frequency current vector reconstructed for the αβ axis, i αβ is the sampling current vector of αβ axis, i αβh is the high-frequency induced current vector before reconstruction of the αβ axis, n is the voltage injection period, and p is the differential operator;

[0029] The reconstruction equation for the fundamental frequency current signal is:

[0030]

[0031] Among them, I αβb is the fundamental current vector reconstructed for the αβ axis, and k is the control period.

[0032] Furthermore, the above-mentioned compensation of the current elliptical trajectory distortion caused by the non-zero speed in the historical cycle and the current cycle using the reconstructed current signal includes:

[0033] The non-zero speed distortion compensation method for the current data in the historical voltage injection cycle is:

[0034]

[0035] in, is the compensated αβ axis current vector, is the estimated speed of the nth voltage injection cycle, T(·) is the coordinate transformation matrix, T s is the PWM signal period;

[0036] The non-zero speed distortion compensation method for the current data in the current voltage injection cycle is:

[0037]

[0038] Furthermore, the least square method is used to estimate the coefficients of the elliptical trajectory equation according to the compensated current, including:

[0039] The least squares method estimates the coefficients of the ellipse trajectory equation as follows:

[0040] y=ΦΘ,

[0041] in,

[0042] and are the compensated α and β axis currents respectively, A, B, C are the coefficients of the elliptical trajectory equation, and N is the total number of voltage injection cycles; the estimated values ​​of the elliptical trajectory equation coefficients are:

[0043]

[0044] are the estimated values ​​of A, B, and C respectively.

[0045] Furthermore, the above-mentioned use of the estimated values ​​of the elliptical trajectory equation coefficients to d e q e Angle with αβ coordinate system Perform sine and cosine angle processing, including:

[0046] Using the estimated values ​​of the coefficients of the ellipse trajectory equation to calculate d e q e Angle with αβ coordinate system The expressions for sine and cosine angle processing are:

[0047]

[0048] are the estimated values ​​of the coefficients A, B, and C of the elliptical trajectory equation respectively.

[0049] Furthermore, the expressions of the above trajectory equation coefficients A, B, and C are:

[0050]

[0051] in,

[0052] Furthermore, the above-mentioned angle-based and d axis and d e The angle between the axes θ m , using Q-PLL to estimate the rotor position and speed, including:

[0053] Rotor position estimate The expression is:

[0054]

[0055] Among them, k is the control period, i d and i q Table lookup values ​​pre-calculated and stored offline for d-axis and q-axis currents respectively;

[0056] Estimated rotor speed The expression is:

[0057]

[0058] Among them, T s is the PWM signal period.

[0059] Furthermore, the function expression of the above Q-PLL is:

[0060]

[0061] Among them, k p =2ξω n , is the damping coefficient, ω n is the bandwidth of Q-PLL, and s is the Laplace operator.

[0062] The method for controlling a low-speed synchronous reluctance motor without a position sensor based on rotating square wave voltage injection according to the present invention has the following beneficial effects:

[0063] 1. The high-frequency rotating voltage injection adopts the form of square wave voltage, and the high-frequency induced current signal is demodulated by current vector reconstruction. Compared with the traditional method of using filters for signal processing, the present invention does not increase the complexity of the control system and improves the dynamic performance of the system.

[0064] 2. It has the advantages of easy parameter setting and no need for motor parameters. The present invention compensates for the elliptical trajectory distortion caused by non-zero speed and can obtain accurate motor angle position estimation at different speeds.

[0065] 3. The position error caused by magnetic saturation is compensated by using a pre-calculated lookup table, and Q-PLL is used to obtain smooth rotor position and speed estimates. The position accuracy is significantly improved, and the angular position estimation error does not increase with the increase of load. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 is the high-frequency induced current in the αβ coordinate system when the motor is stationary;

[0067] Figure 2 Timing diagram for high frequency rotating square wave voltage injection and sampling;

[0068] Figure 3 The signal demodulation block diagram, (a) represents the high-frequency induced current extraction, (b) represents the fundamental current extraction;

[0069] Figure 4 Schematic diagram of high-frequency induced current ellipse fitting with compensation, (a) represents zero speed, (b) represents non-zero speed;

[0070] Figure 5 This is the flow chart of ellipse fitting with NZSD effect compensation;

[0071] Figure 6 It is the principle diagram of Q-PLL with magnetic saturation compensation function;

[0072] Figure 7 The block diagram of sensorless control based on high frequency rotating square wave voltage injection is shown;

[0073] Figure 8 Schematic diagram of the results under variable speed conditions, (a) indicates no compensation for NZSD effect, (b) indicates compensation for NZSD effect;

[0074] Fig. 9 Schematic diagram of the results under load variation conditions, (a) represents uncompensated magnetic saturation, and (b) represents compensated magnetic saturation. DETAILED DESCRIPTION

[0075] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0076] Reference Figures 1 to 5 Specifically describing this embodiment, a position sensorless control method for a low-speed synchronous reluctance motor based on rotating square wave voltage injection described in this embodiment includes:

[0077] Step 1: inject a rotating square wave voltage into the γδ axis rotating at a specific angular frequency to obtain the high-frequency induced current data of the αβ axis; introduce the magnetic salient pole coordinate system d e q e , and deduce the current elliptical trajectory equation. The details are as follows:

[0078] Combination Figure 2 It can be seen that the specific expression of the injected rotating square wave voltage equation is:

[0079]

[0080] in, u αh and u βh are the high-frequency injection voltages of the α and β axes, ω inj is the angular velocity of the γδ axis, U h is the amplitude of the rotating square wave voltage injected into the γδ axis, k is the control period, n is the number of voltage injection cycles, represents the coordinate transformation matrix, u γδh represents the rotating square wave voltage vector injected into the γδ axis, T s is the PWM signal period.

[0081] Introducing the magnetic salient pole coordinate system d e q e , the high-frequency induced current data expression of the αβ axis is obtained as follows:

[0082]

[0083] Among them, p is the differential operator, i αh and i βh are the high frequency induced currents of the α and β axes respectively, and They are d e ,qe The differential inductance of the axis, θ inj is the angle between the α axis and the γ axis, θ e is the α axis and d e The angle between the axes. represents the average value of dq axis inductance, Represents the dq-axis inductance half difference.

[0084] d e q e The relationship between the differential inductance of the axis and the differential inductance of the dq axis is:

[0085]

[0086] Among them, l d and l q are the differential inductances of the d and q axes, respectively, l dq is the cross saturation inductance of the dq axis, θ m is the d-axis and d e The angle between the axes (according to i d 、i q They are the table values ​​pre-calculated and stored offline for the d-axis and q-axis currents respectively).

[0087] Combination Figure 1 It can be seen that the trajectory equation of the high-frequency current is an ellipse, and the expression of the ellipse trajectory equation is:

[0088] A(pi αh ) 2 +Bpi αh pi βh +C(pi βh ) 2 =1,

[0089] Among them, the elliptic coefficients A, B, and C are expressed as:

[0090]

[0091]

[0092] Step 2, demodulate the high-frequency induced current data obtained in step 1, mainly to reconstruct the high-frequency current signal and the baseband current signal; and compensate for the current elliptical trajectory distortion caused by non-zero speed in the historical cycle and the current cycle to obtain a compensated current sample.

[0093] Combination Figure 3 It can be seen that the reconstruction equation for the high-frequency induced current signal is:

[0094]

[0095] Iαβh The high-frequency current vector reconstructed for the αβ axis, i αβ is the sampling current vector of αβ axis, i αβh is the high frequency induced current of αβ axis.

[0096] The reconstruction equation for the fundamental frequency current signal is:

[0097]

[0098] I αβb is the fundamental current of αβ axis.

[0099] Combination Figure 4 It can be seen that non-zero velocity distortion will affect the position estimation accuracy, so a current compensation method for NZSD (non-zero velocity distortion) is proposed, such as Figure 5 The flowchart is shown in FIG.

[0100] The non-zero speed distortion compensation method for the current data in the historical voltage injection cycle is:

[0101]

[0102] in, is the compensated αβ axis current vector, Represents the estimated speed of the nth voltage injection cycle, n=1, 2, ..., N, and N is the total number of voltage injection cycles.

[0103] The non-zero speed distortion compensation method for the current data in the current voltage injection cycle is:

[0104]

[0105] Step 3: Apply the least square method to the coefficients of the elliptical trajectory equation in step 1 according to the compensated current samples obtained in step 2.

[0106] The least squares method estimates the coefficients of the ellipse trajectory equation as follows:

[0107] y=ΦΘ,

[0108] in,

[0109] Estimated coefficients of the ellipse trajectory equation

[0110] Step 4: Perform sine and cosine angle processing, and then combine the θ obtained by the lookup table (LUT) m The rotor position and speed are estimated. In this step, the sine-cosine angle processing can obtain smooth rotor position and rotor speed estimates.

[0111] Using the estimated values ​​of the coefficients of the ellipse trajectory equation to calculate d e q e Angle with αβ coordinate system The expressions for sine and cosine angle processing are:

[0112]

[0113] Use Q-PLL (phase-locked loop) to estimate the rotor position and speed:

[0114] Rotor position estimate

[0115]

[0116] Estimated rotor speed

[0117]

[0118] The expression of the Q-PLL is:

[0119]

[0120] Among them, k p =2ξω n , is the damping coefficient, ω n is the bandwidth of Q-PLL, and s is the Laplace operator. Specific embodiments

[0122] To further illustrate the effectiveness of the method of the present invention and its specific implementation process, a specific implementation case of the present invention is given. A 3-kW synchronous reluctance motor is used as an experimental object, the control frequency is 10 kHz, the injection voltage amplitude is 30 V, and the angular frequency of the γδ coordinate system is 1700π.

[0123] Figure 6 The figure shows the principle diagram of Q-PLL with magnetic saturation compensation function. Smooth position and velocity estimation can be obtained through Q-PLL. Figure 7 Block diagram of the proposed rotating square-wave voltage injection based sensorless control.

[0124] exist Figure 8 In the example, the load is 100% rated load, and the speed command changes in steps of 100 rpm, from 0 to 300 rpm, and then back to 0 rpm. Due to the NZSD effect, the position error increases with the increase of speed, such as Figure 8 (a) At 300 rpm, the position error can reach 5.51°. After compensating for the NZSD effect, the position error is less than 1.21°.

[0125] exist Fig. 9 In the example, the speed is 100 rpm and the load is increased step by step from 25% to 100% and then back to 25% rated load. Fig. 9 (a) shows that magnetic saturation causes the position error to increase with load and causes the motor to lose control at 100% load. After compensation, Fig. 9 As shown in (b), the position accuracy is significantly improved and the motor works stably under rated load.

[0126] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A method for controlling a low-speed synchronous motor without a position sensor by rotating square wave voltage injection, characterized in that: include: Injecting a rotating square wave voltage into the γδ axis of the low-speed synchronous reluctance motor to obtain a high-frequency induced current of the αβ axis, and constructing an elliptical trajectory equation based on the high-frequency induced current; Reconstructing the high-frequency induced current of the αβ axis, and using the reconstructed current signal to compensate for the current elliptical trajectory distortion caused by non-zero speed in the historical cycle and the current cycle; According to the compensated current, the coefficients of the elliptical trajectory equation are estimated by using the least square method; Using the estimated values ​​of the coefficients of the ellipse trajectory equation to calculate d e q e Angle with αβ coordinate system Perform sine and cosine angle processing, the d e q e The coordinate system is the magnetic salient pole coordinate system; Based on the angle and d axis and d e The angle between the axes θ m , Q-PLL is used to estimate the rotor position and speed, and the estimated values ​​of the rotor position and speed are used to realize position sensorless control of the low-speed synchronous reluctance motor.

2. The method for controlling a low-speed synchronous motor without position sensor by rotating square wave voltage injection according to claim 1, characterized in that: The method of injecting a rotating square wave voltage into the γδ axis of the low-speed synchronous reluctance motor to obtain a high-frequency induced current of the αβ axis includes: The expression of the rotating square wave voltage is: Among them, u αh and u βh are the high-frequency injection voltages of the α and β axes respectively, n is the voltage injection period, ω inj is the angular velocity of the γδ axis, T s is the PWM signal period, T(·) is the coordinate transformation matrix, u γδh is the rotating square wave voltage vector injected into the γδ axis, U h is the amplitude of the rotating square wave voltage injected into the γδ axis, and k is the control period; The expression of the high frequency induced current of the αβ axis is: Among them, p is the differential operator, i αh and i βh are the high frequency induced currents of the α and β axes respectively, and They are d e and q e The differential inductance of the axis, θ inj is the angle between the α axis and the γ axis, θ e is the α axis and d e The angle between the axes, l Σ is the average value of dq axis inductance, l Δ is the half difference of dq axis inductance.

3. The method for controlling a low-speed synchronous motor without position sensor by rotating square wave voltage injection according to claim 2, characterized in that: The constructing of the elliptical trajectory equation comprises: The expression of the elliptical trajectory equation is: A(pi αh ) 2 +Bpi αh pi βh +C(pi βh ) 2 1, Among them, A, B, and C are the coefficients of the elliptical trajectory equation.

4. The method for controlling a low-speed synchronous motor without position sensor by rotating square wave voltage injection according to claim 1, characterized in that: The reconstructing the high-frequency induced current of the αβ axis includes: The reconstructed equation for the high-frequency induced current signal is: Among them, I αβh The high-frequency current vector reconstructed for the αβ axis, i αβ is the sampling current vector of αβ axis, i αβh is the high-frequency induced current vector before reconstruction of the αβ axis, n is the voltage injection period, and p is the differential operator; The reconstruction equation for the fundamental frequency current signal is: Among them, I αβb is the fundamental current vector reconstructed for the αβ axis, and k is the control period.

5. The method for controlling a low-speed synchronous motor without position sensor by rotating square wave voltage injection according to claim 4, characterized in that: The method of using the reconstructed current signal to compensate for the current elliptical trajectory distortion caused by the non-zero speed in the historical cycle and the current cycle includes: The non-zero speed distortion compensation method for the current data in the historical voltage injection cycle is: in, is the compensated αβ axis current vector, is the estimated speed of the nth voltage injection cycle, T(·) is the coordinate transformation matrix, T s is the PWM signal period; The non-zero speed distortion compensation method for the current data in the current voltage injection cycle is:

6. The method for controlling a low-speed synchronous motor without position sensor by rotating square wave voltage injection according to claim 1, characterized in that: The method of estimating the coefficients of the elliptical trajectory equation using the least square method according to the compensated current includes: The least squares method estimates the coefficients of the ellipse trajectory equation as follows: y=ΦΘ, in, and are the compensated α and β axis currents respectively, A, B, C are the coefficients of the elliptical trajectory equation, and N is the total number of voltage injection cycles; the estimated value of the elliptical trajectory equation coefficient is: are the estimated values ​​of A, B, and C respectively.

7. The method for controlling a low-speed synchronous motor without position sensor by rotating square wave voltage injection according to claim 1, characterized in that: The method of using the estimated value of the elliptical trajectory equation coefficient to d e q e Angle with αβ coordinate system Perform sine and cosine angle processing, including: Using the estimated values ​​of the coefficients of the ellipse trajectory equation to calculate d e q e Angle with αβ coordinate system The expressions for sine and cosine angle processing are: are the estimated values ​​of the coefficients A, B, and C of the elliptical trajectory equation respectively.

8. The method for controlling a low-speed synchronous motor without position sensor by rotating square wave voltage injection according to claim 3, 6 or 7, characterized in that: The expressions of the trajectory equation coefficients A, B, and C are: in, 9. The method for controlling a low-speed synchronous motor without position sensor by rotating square wave voltage injection according to claim 1, characterized in that: The angle based and d axis and d e The angle between the axes θ m , using Q-PLL to estimate the rotor position and speed, including: Rotor position estimate The expression is: Among them, k is the control period, i d and i q Table lookup values ​​pre-calculated and stored offline for d-axis and q-axis currents respectively; Estimated rotor speed The expression is: Among them, T s is the PWM signal period.

10. The method for controlling a low-speed synchronous motor without position sensor by rotating square wave voltage injection according to claim 9, characterized in that: The function expression of the Q-PLL is: Among them, k p =2ξω n , is the damping coefficient, ω n is the bandwidth of Q-PLL, and s is the Laplace operator.

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