High-frequency signal extraction system and method for high-frequency injection method position sensorless control

Abstract

The invention discloses a high-frequency signal extraction system and method for high-frequency injection method position sensorless control. Relates to a signal processing method. In order to overcome the problem that high-frequency response current signals extracted by a second-order band-pass filter can be delayed and distorted to a great extent in an existing high-frequency injection method position sensorless control method, the system comprises a sampling module, a signal processing module and a signal processing module, the sampling module is used for sampling in real time to obtain a real-time measurement value of a dq-axis current signal of the motor, and the sampling frequency is two times of the high-frequency square wave injection frequency; the high-frequency extraction module is used for subtracting the delay measurement value from the real-time measurement value to obtain a high-frequency output signal, and the pure delay filter is used for filtering the high-frequency output signal; and the frequency of the input / output signal of the pure delay filter is set to be equal to the injection frequency of the high-frequency square wave.

Description

Technical Field

[0001] The invention relates to a signal processing method. Background Art

[0002] PMSM (Permanent Magnet Synchronous Motor) vector control can achieve precise speed control, good torque response, and thus obtain operating characteristics similar to those of a DC motor. However, vector control requires a more complex rotation coordinate transformation and real-time acquisition of the position information of the PMSM rotor. Therefore, the implementation of vector control requires the use of a higher-precision position sensor, such as a resolver, photoelectric encoder, etc.

[0003] Conventional position sensors increase the weight and volume of the PMSM control system, as well as the maintenance cost, and are susceptible to the effects of humidity, coldness, and other environmental factors. Therefore, a position sensorless control strategy can be adopted, that is, the position information of the motor is estimated by using the electrical signals such as the voltage and current of the motor. The high-frequency square wave injection method is a position sensorless control strategy that is widely used in the zero and low-speed stages of PMSM. The basic principle is to inject a square wave signal of the switching frequency into the rotating shaft system of the motor, and estimate the rotor position by extracting the PMSM high-frequency current signal. Since the high-frequency response current signal contains a fundamental frequency signal, a high-frequency signal with the same frequency as the injected signal, and a higher-frequency noise signal, a second-order bandpass filter is usually required to filter the high-frequency response current signal.

[0004] The amplitude-frequency characteristic and phase-frequency characteristic curves of the existing second-order bandpass filter are as follows: Figure 1 As shown. Its amplitude-frequency characteristic and phase-frequency characteristic are relatively steep near the center frequency, and it is sensitive to changes in the frequency of the high-frequency response current. In actual applications, PMSM will inevitably experience factors such as speed changes and load changes. In these cases, the frequency of the high-frequency response current will change to a certain extent, causing the frequency of the high-frequency response current to deviate from the center point. The high-frequency response current signal extracted by the bandpass filter will have a large degree of delay and distortion, which has an adverse effect on the extraction of the rotor position. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem that in the existing high-frequency injection method for position sensorless control, the high-frequency response current signal extracted by the second-order bandpass filter will have a large degree of delay and distortion, and provide a high-frequency signal extraction system and method for high-frequency injection method for position sensorless control.

[0006] The present invention provides a high-frequency signal extraction system for high-frequency injection method position sensorless control, comprising:

[0007] The sampling module is used to obtain the real-time measurement value of the motor dq axis current signal through real-time sampling:

[0008] The sampling frequency is twice the high-frequency square wave injection frequency;

[0009] And delay one sampling cycle to obtain the delayed measurement value of the motor dq axis current signal:

[0010] The high-frequency extraction module is used to subtract the delay measurement value from the real-time measurement value to obtain a high-frequency output signal:

[0011] Pure delay filter, used to filter high-frequency output signals;

[0012] The frequency of the input / output signal of the pure delay filter is set to be equal to the high frequency square wave injection frequency.

[0013] The present invention also provides a high-frequency signal extraction method for high-frequency injection method position sensorless control, the steps are as follows:

[0014] Step 1: Real-time sampling to obtain the real-time measurement value of the motor dq axis current signal:

[0015] The sampling frequency is twice the high-frequency square wave injection frequency;

[0016] Step 2: Delay one sampling cycle and sample to obtain the delayed measurement value of the motor dq axis current signal:

[0017] Step 3: Subtract the delay measurement value from the real-time measurement value to obtain a high-frequency output signal:

[0018] Step 4: Filter the high frequency output signal by a pure delay filter;

[0019] The frequency of the input / output signal of the pure delay filter is set to be equal to the high frequency square wave injection frequency.

[0020] The beneficial effects of the present invention are:

[0021] The high-frequency signal extraction system and method for high-frequency injection method position sensorless control of the present invention, the pure delay filter can effectively extract the injection frequency ω in The signal and injection frequency ω in The harmonic components near it, at the same time, the phase shift at this frequency is 0°, and the amplitude is doubled, which can effectively filter out low-frequency and DC components. In the high-frequency signal extraction link based on pure delay filter, the delay and attenuation of the signal can be reduced, and the anti-interference performance of the motor control system can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1The amplitude-frequency characteristic and phase-frequency characteristic curves of the existing second-order bandpass filter;

[0023] Figure 2 The present invention provides the amplitude-frequency characteristic and phase-frequency characteristic curves of the pure delay filter in the high-frequency signal extraction system and method for position sensorless control using the high-frequency injection method. DETAILED DESCRIPTION

[0024] The following will be combined with the 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, not 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 are within the scope of protection of the present invention.

[0025] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0026] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention. Specific implementation method 1

[0028] The high-frequency signal extraction system for high-frequency injection method position sensorless control of this embodiment includes:

[0029] The sampling module is used to obtain the real-time measurement value of the motor dq axis current signal through real-time sampling:

[0030] The sampling frequency is twice the high-frequency square wave injection frequency;

[0031] And delay one sampling cycle to obtain the delayed measurement value of the motor dq axis current signal:

[0032] The high-frequency extraction module is used to subtract the delay measurement value from the real-time measurement value to obtain a high-frequency output signal:

[0033] Pure delay filter, used to filter high-frequency output signals;

[0034] The frequency of the input / output signal of the pure delay filter is set to be equal to the high frequency square wave injection frequency.

[0035] Specifically, this embodiment is based on the high-frequency current signal extraction link of the pure delay filter.

[0036] The motor dq axis current signal equation consists of two parts:

[0037]

[0038] Among them, i df,i df is the fundamental current component on the dq axis system; i dh ,i qh is the high-frequency current component of the injection frequency on the dq axis system. The sampling frequency of the high-frequency current extraction link is set to twice the injection frequency, and the detected current is delayed by one sampling cycle, that is, half of the injection cycle. The high-frequency current signal can be obtained by subtracting the original motor dq axis current signal from the delayed motor dq axis current signal. Specific implementation method 2

[0040] This embodiment is a further explanation of the embodiment 1. In this embodiment, the sampling module obtains the real-time measurement value i of the motor dq axis current signal through the following formula: dq (k-1) and the delayed measurement value i dq (k);

[0041] i dq (k-1)=i dqf (k)-i dqh (k);

[0042] i dq (k) = i dqf (k)+i dqh (k);

[0043] Among them, i dqf (k) is the fundamental current component in the motor dq axis current signal; i dqh (k) is the high-frequency current component in the motor dq axis current signal.

[0044] This embodiment is completely identical to the first embodiment in terms of other technical features.

[0045] Specifically, since the high-frequency current frequency is much greater than the fundamental current frequency, it can be considered that the fundamental currents at adjacent sampling moments are equal, and the high-frequency current amplitudes are equal and the polarities are opposite. The current equations at adjacent moments are:

[0046]

[0047] Subtracting the current at time k from the motor dq axis current signal at time k-1 can obtain the high-frequency current signal:

[0048] 2i dqh (k) = i dq (k)-i dq (k-1).

[0049] The amplitude-frequency characteristic and phase-frequency characteristic curves of the pure delay filter are as follows: Figure 2 .

[0050] The pure delay filter can effectively extract point A (injection frequency ω in The signal and injection frequency ω in The harmonic components near it, at the same time, the phase shift at this frequency is 0°, and the amplitude is doubled, which can effectively filter out the low-frequency and DC components. Specific implementation method three

[0052] This implementation is a further description of implementation one or two. In this implementation, the pure delay filter is a bandpass filter, and the transfer function of the pure delay filter in the s domain is:

[0053] G(s)=1-e -τs

[0054] Wherein, τ is the time characteristic of the input / output signal of the pure delay filter; s = jω, j is the sign of the imaginary part;

[0055] The amplitude-frequency characteristic is:

[0056] L(ω)=G(jω)=2|sin(τω / 2)|

[0057] The phase-frequency characteristic is:

[0058]

[0059] The other technical features of this embodiment are exactly the same as those of embodiment one or two.

[0060] Specifically, the transfer function of the pure delay filter in the s domain is:

[0061] G(s)=1-e -τs

[0062] Substituting s=jω into the above formula, we get:

[0063] G(jω)=1-cos(τω)+jsin(τω)

[0064] The amplitude-frequency characteristic and phase-frequency characteristic can be obtained as:

[0065] L(ω)=G(jω)=2|sin(τω / 2)|

[0066]

[0067] pass Figure 1 and Figure 2 By comparison, it can be seen that the amplitude-frequency and phase-frequency characteristics of the pure delay filter near the specified point A frequency are smoother than those of the existing second-order bandpass filter. When the frequency of the high-frequency response current fluctuates in a small range due to factors such as load, the signal extracted by the pure delay filter will not have a large delay and distortion, and the sensorless control system can still operate normally. Specific implementation method four

[0069] This embodiment is a further explanation of the third embodiment. In this embodiment, the number of pure delay filters is two or more;

[0070] The output signal of the previous pure delay filter serves as the input signal of the next pure delay filter.

[0071] The other technical features of this embodiment are exactly the same as those of the third embodiment.

[0072] Specifically, according to the above analysis, the delay filters can be cascaded to increase the signal amplitude by four times, thereby improving the signal-to-noise ratio of the high-frequency current and the filtering effect of the fundamental frequency signal. Specific implementation method five

[0074] The high-frequency signal extraction method for high-frequency injection method position sensorless control of this embodiment has the following steps:

[0075] Step 1: Real-time sampling to obtain the real-time measurement value of the motor dq axis current signal:

[0076] The sampling frequency is twice the high-frequency square wave injection frequency;

[0077] Step 2: Delay one sampling cycle and sample to obtain the delayed measurement value of the motor dq axis current signal:

[0078] Step 3: Subtract the delay measurement value from the real-time measurement value to obtain a high-frequency output signal:

[0079] Step 4: Filter the high frequency output signal by a pure delay filter;

[0080] The frequency of the input / output signal of the pure delay filter is set to be equal to the high frequency square wave injection frequency. Specific implementation method 6

[0082] This embodiment is a further explanation of the fifth embodiment. In this embodiment, in step 1, the real-time measurement value i of the motor dq axis current signal is obtained by the following formula: dq (k-1) and the delayed measurement value i dq (k);

[0083] i dq (k-1)=i dqf (k)-i dqh (k);

[0084] i dq (k) = i dqf (k)+i dqh (k);

[0085] Among them, i dqf (k) is the fundamental current component in the motor dq axis current signal; i dqh (k) is the high-frequency current component in the motor dq axis current signal.

[0086] The other technical features of this embodiment are exactly the same as those of embodiment five. Specific implementation method seven

[0088] This embodiment is an improved description of the fifth or sixth embodiment. In this embodiment, the pure delay filter is a bandpass filter, and the transfer function of the pure delay filter in the s domain is:

[0089] G(s)=1-e -τs

[0090] Wherein, τ is the time characteristic of the input / output signal of the pure delay filter; s = jω, j is the sign of the imaginary part;

[0091] The amplitude-frequency characteristic is:

[0092] L(ω)=G(jω)=2|sin(τω / 2)|

[0093] The phase-frequency characteristic is:

[0094]

[0095] The other technical features of this embodiment are exactly the same as those of embodiment five or six. Specific implementation method eight

[0097] This embodiment is a further explanation of the seventh embodiment. In this embodiment, the number of pure delay filters is two or more;

[0098] The output signal of the previous pure delay filter serves as the input signal of the next pure delay filter.

[0099] The other technical features of this embodiment are exactly the same as those of embodiment seven.

[0100] 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 features of the various dependent claims and 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 the individual embodiments may be used in other embodiments.

Claims

1. A high-frequency signal extraction system for high-frequency injection method position sensorless control, characterized in that: include: The sampling module is used to obtain the real-time measurement value of the motor dq axis current signal through real-time sampling: The sampling frequency is twice the high-frequency square wave injection frequency; And delay one sampling cycle to obtain the delayed measurement value of the motor dq axis current signal: The high-frequency extraction module is used to subtract the delay measurement value from the real-time measurement value to obtain a high-frequency output signal: A pure delay filter, used for filtering the high frequency output signal; The frequency of the input / output signal of the pure delay filter is set to be equal to the high frequency square wave injection frequency.

2. The high-frequency signal extraction system for high-frequency injection method position sensorless control according to claim 1, characterized in that: The sampling module obtains the real-time measurement value i of the motor dq axis current signal through the following formula: dq (k-1) and the delayed measurement value i dq (k); i dq (k-1)=i dqf (k)-i dqh (k); i dq (k)=i dqf (k)+i dqh (k); Among them, i dqf (k) is the fundamental current component in the motor dq axis current signal; i dqh (k) is the high-frequency current component in the motor dq axis current signal.

3. The high-frequency signal extraction system for high-frequency injection method position sensorless control according to claim 1 or 2, characterized in that: The pure delay filter is a bandpass filter, and the transfer function of the pure delay filter in the s domain is: G(s)=1-e -τs Wherein, τ is the time characteristic of the input / output signal of the pure delay filter; s = jω, j is the sign of the imaginary part; The amplitude-frequency characteristic is: L(ω)=G(jω)=2|sin(τω / 2)| The phase-frequency characteristic is:

4. The high-frequency signal extraction system for high-frequency injection method position sensorless control according to claim 3, characterized in that: The number of the pure delay filters is two or more; The output signal of the previous pure delay filter serves as the input signal of the next pure delay filter.

5. A high-frequency signal extraction method for high-frequency injection method position sensorless control, characterized in that: Here are the steps: Step 1: Real-time sampling to obtain the real-time measurement value of the motor dq axis current signal: The sampling frequency is twice the high-frequency square wave injection frequency; Step 2: Delay one sampling cycle and sample to obtain the delayed measurement value of the motor dq axis current signal: Step 3: Subtract the delay measurement value from the real-time measurement value to obtain a high-frequency output signal: Step 4: filtering the high frequency output signal by a pure delay filter; The frequency of the input / output signal of the pure delay filter is set to be equal to the high frequency square wave injection frequency.

6. The high-frequency signal extraction system for high-frequency injection method position sensorless control according to claim 5, characterized in that: In step 1, the real-time measurement value i of the motor dq axis current signal is obtained by the following formula: dq (k-1) and the delayed measurement value i dq (k); i dq (k-1)=i dqf (k)-i dqh (k); i dq (k)=i dqf (k)+i dqh (k); Among them, i dqf (k) is the fundamental current component in the motor dq axis current signal; i dqh (k) is the high-frequency current component in the motor dq axis current signal.

7. The high-frequency signal extraction method for high-frequency injection method position sensorless control according to claim 5 or 6, characterized in that: The pure delay filter is a bandpass filter, and the transfer function of the pure delay filter in the s domain is: G(s)=1-e -τs Wherein, τ is the time characteristic of the input / output signal of the pure delay filter; s = jω, j is the sign of the imaginary part; The amplitude-frequency characteristic is: L(ω)=G(jω)=2|sin(τω / 2)| The phase-frequency characteristic is:

8. The high-frequency signal extraction method for high-frequency injection method position sensorless control according to claim 7, characterized in that: The number of the pure delay filters is two or more; The output signal of the previous pure delay filter serves as the input signal of the next pure delay filter.

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