A sensorless noise reduction control method for permanent magnet synchronous motor with random frequency high-frequency triangular wave voltage injection

Abstract

The present invention discloses a method for position sensorless noise reduction control of a permanent magnet synchronous motor using random frequency high-frequency triangular wave voltage injection. This method randomly injects two high-frequency triangular wave voltage signals of different frequencies into an estimated rotor reference frame. The two injected voltage signals of different frequencies follow the principle of equal volt-second area to ensure that the induced current amplitudes are equal. The high-frequency signal is used to excite the saturated salient polarity of the motor, and the estimated position angle and estimated speed are extracted from the high-frequency current response. The motor is demodulated through two rotational transformations and absolute value conversion, and then normalized to eliminate the influence of the injection amplitude and related parameters. Finally, the observation is completed through an orthogonal phase-locked loop. The position angle and estimated speed are estimated to achieve position sensorless control of the permanent magnet synchronous motor at low speed. This method can effectively reduce the maximum noise at the injection frequency and expand the power spectrum density of the high-frequency current, thereby reducing the audible noise caused by the high-frequency current.

Description

Technical Field

[0001] The present invention belongs to the field of permanent magnet synchronous motor drive control applications, and in particular relates to a position sensorless noise reduction control method for a permanent magnet synchronous motor with random frequency high frequency triangular wave voltage injection. Background Art

[0002] Permanent magnet synchronous motors (PMSMs) offer advantages such as high efficiency, high power density, and a wide speed regulation range, making them widely used in aerospace, electric vehicles, servo control systems, and other fields. Vector control, a high-performance control method for PMSMs, requires decoupling rotor position angle information, typically obtained through mechanically mounted position sensors. However, this approach increases cost and reduces reliability. To address this issue, researchers have proposed sensorless control strategies.

[0003] Currently, there are two main types of sensorless position control methods for permanent magnet synchronous motors: 1. High-frequency signal injection based on motor saliency, suitable for low speeds; and 2. Fundamental wave analysis based on the motor model, suitable for high speeds. High-frequency signal injection methods can be categorized by the injection axis: rotating injection in a two-phase stationary coordinate system and pulse injection in a rotating coordinate system. Pulse injection can be further categorized by the injected waveform into sinusoidal and square wave injection. Pulse injection offers excellent control performance at low speeds, but high-frequency signal injection generates high-frequency noise, limiting its applicability. To address this issue, relevant scholars have conducted extensive research. The Chinese invention patent "A Permanent Magnet Synchronous Motor Rotor Position Observer Using Random Frequency High-Frequency Square Wave Voltage Injection" (Patent No.: 201710249453.1) discloses a permanent magnet synchronous motor rotor position observer using random frequency high-frequency square wave voltage injection. This method randomly injects two square wave voltages of different frequencies into the rotor reference frame, expanding the current power spectral density, reducing discrete spikes, and minimizing noise. The Chinese invention patent, "A method for suppressing high-frequency noise in a permanent magnet motor rotor position observer with random sinusoidal injection considering digital control delay" (Patent No. 201810916733.8), discloses a method for suppressing high-frequency noise in a permanent magnet motor rotor position observer with random sinusoidal injection considering digital control delay. This method randomly injects two sinusoidal voltages of different frequencies into the rotor reference frame. By selecting the appropriate frequency, discrete spikes are eliminated and noise is reduced. However, the noise at the injection frequency is higher for both sine and square wave injections. Summary of the Invention

[0004] Purpose of the invention: To address the problems that mechanical position sensors increase costs and reduce reliability, and at the same time reduce the noise caused by high-frequency injection and the maximum noise at the injection frequency, a position sensorless noise reduction control method for permanent magnet synchronous motors with random frequency high-frequency triangular wave voltage injection is proposed to reduce noise and realize position sensorless operation of permanent magnet synchronous motors at low speeds.

[0005] Technical solution: To achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a position sensorless noise reduction control method for a permanent magnet synchronous motor using random frequency high frequency triangular wave voltage injection, comprising the following steps:

[0007] Step 1: Generate a random frequency high-frequency triangular wave voltage signal, using two high-frequency triangular wave voltage signals with different frequencies;

[0008] Step 2: inject the voltage signal into the estimated reference frame and inject the random frequency high frequency triangle wave voltage signal into the estimated d-axis;

[0009] Step 3: Demodulate the position angle and speed: The high-frequency current response is processed and normalized to reduce the impact of injection amplitude and parameters on the position estimation. A position error signal is obtained through an orthogonal phase-locked loop (PLL). Finally, the estimated electrical angular velocity is obtained through a proportional-integral (PI) controller. The estimated position angle is obtained by integrating the electrical angular velocity.

[0010] Furthermore, the waveform of the triangle wave in step 1 is:

[0011] Define the unit triangle wave function Φ tri (t,T):

[0012]

[0013] Where T is the period of the triangle wave, t m (t,T) is the remainder when t is divided by T.

[0014] Furthermore, the principle for generating the triangular wave voltage signal in step 1 is:

[0015] When using two high-frequency triangular wave voltage signals of different frequencies, in order to ensure that the amplitudes of the induced high-frequency currents are equal, the principle of equal volt-second area should be followed, that is, the product of the period and amplitude of the two signals should be equal.

[0016] Furthermore, in step 2, a random frequency triangle wave voltage signal is injected into the estimated d-axis:

[0017]

[0018]

[0019] Where u e dh and u e qh To estimate the high-frequency voltage of the dq axis, It means that a random selection is performed every time an injection cycle is completed, V R is the injected random frequency triangle wave voltage amplitude, T R is the injected random frequency triangle wave voltage period, V1 and V2 are the amplitudes of signals 1 and 2, and T1 and T2 are the periods of signals 1 and 2.

[0020] Furthermore, the waveform of the high-frequency current in step 3 is:

[0021] Define the unit quadratic function Φ qua (t,T):

[0022]

[0023] Furthermore, the high-frequency current response of step 3 is:

[0024] The motor phase current is sampled and transformed by abc / αβ (Clark) to obtain the current i in the two-phase stationary coordinate system. α and i β , making i α and i β The high-frequency current response signal i is extracted through a high-pass filter (HPF) αh and i βh , which can be expressed as:

[0025]

[0026]

[0027] Where i αh and i βh is the high-frequency current of the αβ axis. dh and L qh is the dq axis high frequency incremental inductance. Δθ is the estimation error, θ e is the actual position angle, is the estimated position angle, and

[0028] Furthermore, the specific process of processing the high-frequency current response in step 3 includes:

[0029] Define the measurement reference system d m -q m , which lags behind the estimated reference frame by 45°, and the induced current is projected into this reference frame:

[0030]

[0031] Where, and To measure the high frequency current in the reference frame, ΔL=(L qh –L dh) / 2,

[0032] When the error is small enough, the above formula is simplified to:

[0033]

[0034] Convert the above formula to absolute value, since L qh >ΔL, so L qh ±ΔLsin(2Δθ)>0 always holds true, and the following formula is obtained:

[0035]

[0036] Then project it back to the two-phase stationary coordinate system:

[0037]

[0038] Where, and is the demodulated αβ axis high frequency current.

[0039] Furthermore, the normalization step of step 3 includes:

[0040] When the error is small enough, the above formula is simplified to:

[0041]

[0042] In order to reduce the influence of injection amplitude and parameters on position estimation, normalization is performed:

[0043]

[0044] Where, and is the normalized current signal.

[0045] Furthermore, the position error signal of step 3 is:

[0046]

[0047] Where ε is the position error signal.

[0048] Finally, the estimated electrical angular velocity is obtained through a proportional-integral (PI) controller, and the estimated position angle can be obtained by integrating the electrical angular velocity.

[0049] Beneficial effects of the present invention:

[0050] 1) The present invention calculates and estimates the position angle and speed based on the principle of motor saturation saliency, eliminating the need for mechanically installed position sensors, reducing costs and improving reliability.

[0051] 2) To solve the problem of obtaining the position angle of the motor at zero and low speed, the present invention adopts a random frequency high-frequency triangular wave voltage injection method, and obtains the estimated position angle and speed of the motor by demodulating the high-frequency response current, thereby realizing position sensorless control of the permanent magnet synchronous motor.

[0052] 3) The fundamental frequency component of the voltage signal in the form of a triangular wave at the injection frequency is small, which can reduce the maximum noise at the injection frequency.

[0053] 4) Random frequency triangle wave voltage injection can expand the power spectrum density of the current and reduce discrete spikes, thereby reducing the high-frequency noise of fixed frequency triangle wave injection.

[0054] 5) The present invention is applicable to both surface-mounted and built-in permanent magnet synchronous motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Schematic diagram of position sensorless noise reduction control for random frequency high-frequency triangle wave voltage injection;

[0056] Figure 2 is the waveform of injected voltage and induced current;

[0057] Figure 3 This is the structural diagram of the observer;

[0058] Figure 4 PSD experimental analysis diagram; (a) is the first PSD experimental analysis diagram; (b) is the second PSD experimental analysis diagram; (c) is the third PSD experimental analysis diagram;

[0059] Figure 5 This is the result graph of running under medium load;

[0060] Figure 6 The figure shows the results of running under full load. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0062] like Figure 1 As shown, the present invention proposes a position sensorless noise reduction control method for a permanent magnet synchronous motor with random frequency high frequency triangular wave voltage injection.

[0063] The specific implementation steps of the proposed method for position sensorless noise reduction control of a permanent magnet synchronous motor using random frequency high-frequency triangular wave voltage injection include:

[0064] Step 1: Generate a random frequency high-frequency triangle wave voltage signal

[0065] Define the unit triangle wave function Φ tri (t,T):

[0066]

[0067] Where T is the period of the triangle wave, t m (t,T) is the remainder when t is divided by T.

[0068] like Figure 2 As shown, two high-frequency triangular wave voltage signals with different frequencies are used. In order to ensure that the amplitudes of the induced high-frequency currents are equal, the principle of equal volt-second area should be followed, that is, the product of the period and amplitude of the two signals should be equal.

[0069] Step 2: Inject the voltage signal into the estimated reference frame

[0070] Inject a random frequency triangle wave voltage on the estimated d-axis:

[0071]

[0072]

[0073] Where u e dh and u e qh To estimate the high-frequency voltage of the dq axis, It means that a random selection is performed every time an injection cycle is completed, V R is the injected random frequency triangle wave voltage amplitude, T R is the injected random frequency triangle wave voltage period, V1 and V2 are the amplitudes of signals 1 and 2, and T1 and T2 are the periods of signals 1 and 2.

[0074] Step 3: Demodulate position angle and speed

[0075] Define the unit quadratic function Φ qua (t,T):

[0076]

[0077] The motor phase current is sampled and transformed by abc / αβ (Clark) to obtain the current i in the two-phase stationary coordinate system. α and i β , making i α and i β The high-frequency current response signal i is extracted through a high-pass filter (HPF) αh and i βh , which can be expressed as:

[0078]

[0079] Where i αh and i βh is the high-frequency current of the αβ axis. dh and L qh is the dq axis high frequency incremental inductance. Δθ is the estimation error, θ e is the actual position angle, is the estimated position angle, and

[0080] Define the measurement reference system d m -q m , which lags behind the estimated reference frame by 45°, and the induced current is projected into this reference frame:

[0081]

[0082] Where, and To measure the high frequency current in the reference frame, ΔL=(L qh –L dh ) / 2, When the error is small enough, the above formula is simplified to:

[0083]

[0084] Convert the above formula to absolute value, since L qh >ΔL, so L qh ±ΔLsin(2Δθ)>0 always holds true, and the following formula is obtained:

[0085]

[0086] Then project it back to the two-phase stationary coordinate system:

[0087]

[0088] Where, and is the demodulated αβ axis high frequency current.

[0089] When the error is small enough, the above formula is simplified to:

[0090]

[0091] In order to reduce the influence of injection amplitude and parameters on position estimation, normalization is performed:

[0092]

[0093] Where, and is the normalized current signal.

[0094] Through an orthogonal phase-locked loop, the position error signal is obtained:

[0095]

[0096] Where ε is the position error signal.

[0097] Finally, the estimated electrical angular velocity is obtained through the proportional integral (PI) controller, and the estimated position angle can be obtained by integrating the electrical angular velocity. Figure 3 shown.

[0098] Figure 4 The PSD analysis results show that the maximum noise of the triangle wave at the injection frequency is lower. The random frequency triangle wave injection broadens the power spectrum density of the current, the discrete peak decreases, and the noise is reduced.

[0099] Figure 5 This is the experimental result of medium load operation. The estimated error is about 8°, which is relatively low and the control performance is good.

[0100] Figure 6 This is the experimental result of full load operation. The estimated error is about 12°, and the control performance is good.

[0101] The above embodiments are intended only to illustrate the design concepts and features of the present invention, and are intended to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. Therefore, any equivalent changes or modifications based on the principles and design concepts disclosed in the present invention are intended to fall within the scope of protection of the present invention.

Claims

1. A method for controlling the noise reduction of a permanent magnet synchronous motor without position sensor by injecting a random frequency high-frequency triangular wave voltage, characterized in that: The following steps are involved: Step 1: Generate a random frequency high-frequency triangular wave voltage signal, using two high-frequency triangular wave voltage signals with different frequencies; Step 2: inject the voltage signal into the estimated reference frame and inject the random frequency high frequency triangle wave voltage signal into the estimated d-axis; Step 3: Demodulate the position angle and speed: The high-frequency current response is processed and normalized to reduce the impact of injection amplitude and parameters on the position estimation. A position error signal is obtained through an orthogonal phase-locked loop (PLL). Finally, the estimated electrical angular velocity is obtained through a proportional-integral (PI) controller. The estimated position angle is obtained by integrating the electrical angular velocity. The specific process of processing the high-frequency current response in step 3 includes: Define the measurement reference system d m -q m , which lags behind the estimated reference frame by 45°, and the induced current is projected into this reference frame: Where, and To measure the high frequency current in the reference frame, ΔL=(L qh –L dh ) / 2, When the error is small enough, the above formula is simplified to: Convert the above formula to absolute value, since L qh >ΔL, so L qh ±ΔLsin(2Δθ)>0 always holds true, and the following formula is obtained: Then project it back to the two-phase stationary coordinate system: Where, and is the demodulated αβ axis high frequency current; The normalization steps in step 3 include: When the error is small enough, the above formula is simplified to: In order to reduce the influence of injection amplitude and parameters on position estimation, normalization is performed: Where, and is the normalized current signal; The position error signal in step 3 is: Where ε is the position error signal.

2. The method for controlling the noise reduction of a permanent magnet synchronous motor without position sensor by injecting a random frequency high frequency triangular wave voltage according to claim 1, characterized in that: The waveform of the triangle wave in step 1 is: Define the unit triangle wave function Φ tri (t,T): Where T is the period of the triangle wave, t m (t,T) is the remainder when t is divided by T.

3. The method for controlling the noise reduction of a permanent magnet synchronous motor without position sensor by injecting a random frequency high frequency triangular wave voltage according to claim 1, characterized in that: The principle of generating the triangular wave voltage signal in step 1 is: When using two high-frequency triangular wave voltage signals of different frequencies, in order to ensure that the amplitudes of the induced high-frequency currents are equal, the principle of equal volt-second area should be followed, that is, the product of the period and amplitude of the two signals should be equal.

4. The method for controlling the noise reduction of a permanent magnet synchronous motor without position sensor by injecting a random frequency high frequency triangular wave voltage according to claim 1, characterized in that: In step 2, a random frequency triangle wave voltage signal is injected into the estimated d-axis: Where u e dh and u e qh To estimate the high-frequency voltage of the dq axis, It means that a random selection is performed every time an injection cycle is completed, V R is the injected random frequency triangle wave voltage amplitude, T R is the injected random frequency triangle wave voltage period, V1 and V2 are the amplitudes of signals 1 and 2, and T1 and T2 are the periods of signals 1 and 2.

5. The method for controlling the noise reduction of a permanent magnet synchronous motor without position sensor by injecting a random frequency high frequency triangular wave voltage according to claim 1, characterized in that: The waveform of the high-frequency current in step 3 is: Define the unit quadratic function Φ qua (t,T):

6. The method for controlling the noise reduction of a permanent magnet synchronous motor without position sensor by injecting a random frequency high frequency triangular wave voltage according to claim 1, characterized in that: The high-frequency current response of step 3 is: The motor phase current is sampled and transformed by abc / αβ (Clark) to obtain the current i in the two-phase stationary coordinate system. α and i β , making i α and i β The high-frequency current response signal i is extracted through a high-pass filter (HPF) αh and i βh , which can be expressed as: Where i αh and i βh is the high-frequency current of αβ axis, L dh and L qh is the dq axis high frequency incremental inductance, Δθ is the estimation error, θ e is the actual position angle, is the estimated position angle, and

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