A method for suppressing wideband current harmonics in permanent magnet synchronous motors

Abstract

This invention belongs to the field of permanent magnet synchronous motor technology and relates to a wide-frequency domain current harmonic suppression method for permanent magnet synchronous motors. The method includes: acquiring the q-axis and d-axis currents of the motor and subtracting them from a given target current value to obtain a current error signal; using closed-loop Fourier transform to extract harmonic components from the current error signal and generating a harmonic compensation voltage signal; using linear active disturbance rejection control (ADC) to control the q-axis and / or d-axis currents to generate a voltage control signal; fusing the harmonic compensation voltage signal and the voltage control signal, and then generating an inverter control signal after passing through SVPWM, which is applied to the motor to achieve full-frequency domain optimized control of the motor current. This invention combines linear ADC with closed-loop Fourier transform in parallel design, taking into account the synergistic suppression capability of low-frequency disturbances and high-frequency harmonics, achieving effective suppression of target harmonics even when the motor speed changes, thus improving the system's adaptability under varying operating conditions.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet synchronous motor technology and relates to a method for suppressing wide-frequency current harmonics in permanent magnet synchronous motors. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in high-performance servo systems and electric drive systems due to their high efficiency, high power density, and excellent dynamic performance. However, in actual operation, the motor current is not only affected by control commands but also by various factors such as inverter nonlinearity, motor structural asymmetry, flux linkage distortion, and load disturbances, resulting in the presence of multi-frequency harmonic components in the stator current. These harmonics cause electromagnetic torque fluctuations, leading to increased motor vibration and noise, and decreased control accuracy.

[0003] To address these issues, Linear Active Disturbance Rejection Control (LADRC) treats all uncertainties in the system as a "total disturbance" through a Linear Extended State Observer (LESO) and estimates and compensates for them in real time. Using LADRC for current loop control of a motor can suppress harmonics in the motor to a certain extent.

[0004] However, LADRC is less effective at suppressing high-frequency harmonics and mainly relies on increasing the bandwidth of the extended state observer to enhance the estimation of high-frequency disturbances. However, increasing the bandwidth can lead to amplification of system noise and even cause stability problems. Summary of the Invention

[0005] This invention proposes a wide-frequency-domain current harmonic suppression method for permanent magnet synchronous motors. By combining closed-loop Fourier transform (CFT) and linear active disturbance rejection control (LADRC) techniques, and fully considering the amplitude-frequency characteristics, the method utilizes the suppression effect of CFT on harmonics of specific frequencies to overcome the shortcomings of existing LADRC methods in high-frequency harmonic suppression, thereby improving the full-frequency-domain harmonic suppression capability of the motor system. The specific technical solution is as follows:

[0006] A method for suppressing wideband current harmonics in a permanent magnet synchronous motor includes:

[0007] Step S1: Obtain the motor's... The current error signal is obtained by subtracting the d-axis current and the d-axis current from the given target current value.

[0008] Step S2: Use closed-loop Fourier transform to extract the harmonic components in the current error signal and generate a harmonic compensation voltage signal.

[0009] Step S3: Use linear active disturbance rejection control to... The current of the axial and / or d-axis is controlled to generate a voltage control signal;

[0010] Step S4: The harmonic compensation voltage signal and the voltage control signal are fused together, and after passing through SVPWM, the control signal of the inverter is generated and applied to the motor to achieve full-frequency domain optimized control of the motor current.

[0011] Further, step S2 specifically includes:

[0012] In a synchronous rotating coordinate system, the orthogonality principle of trigonometric functions is used to multiply the current error signal by the unit sine signal and the unit cosine signal corresponding to the harmonic frequency to be extracted.

[0013] The multiplied signals are then passed through low-pass filters to remove high-frequency AC components, resulting in DC components.

[0014] Using a closed-loop regulation mechanism based on a PI controller, the DC component is compared with a zero reference value, and the difference is input to the PI controller to generate the regulation amount.

[0015] The output of the PI controller is multiplied by the unit sine signal and the unit cosine signal respectively, and the two results are superimposed and amplified by the gain coefficient to obtain the harmonic compensation voltage signal.

[0016] Furthermore, the harmonics to be extracted include the 6k harmonic and the 12k harmonic.

[0017] Furthermore, step S3 specifically includes:

[0018] for The axis is used to reconstruct the controlled object into the following integral cascaded standard form:

[0019]

[0020] make For the input of the motor system, This is to control the output, i.e., the voltage control signal. The nominal value of the control gain is usually taken as... , = For the total current disturbance, then... The shaft current loop system can be described by the following first-order linear extended state-space equation:

[0021]

[0022] Selecting state variables track Axis current, state variables A second-order linear extended state observer (LESO) is constructed by tracking the total perturbation, and the equation expression is as follows:

[0023]

[0024] In the formula For observation error, For observer gain;

[0025] The observer poles are configured using the bandwidth parameterization method, which unifies the poles of the LESO characteristic equation to the observer bandwidth in the left half-plane. At this point, the relationship between the gain parameter and the bandwidth is:

[0026]

[0027] By adjusting a single parameter This allows for a balance between observation speed and noise suppression capability; It will be able to converge quickly to the total disturbance. ; after obtaining the total disturbance estimate Then, it is canceled out through the feedforward channel, thereby linearizing the originally nonlinear controlled object into an integral cascade type;

[0028] The expression for linear active disturbance rejection control is as follows:

[0029] ;

[0030] For the corresponding Reference value for shaft current.

[0031] Furthermore, the harmonic compensation voltage signal and the voltage control signal are fused by linear superposition.

[0032] Furthermore, in step S4, the control voltage obtained after fusion is input into the SVPWM module after inverse Parker transformation to generate the control signal for the inverter.

[0033] Furthermore, at a fixed motor speed, the open-loop gain of the low-frequency system is dominated by linear active disturbance rejection control, while at high-frequency harmonics, local high-gain peaks are formed by closed-loop Fourier transform through modulation and demodulation.

[0034] Furthermore, under variable speed motor conditions: at low speeds, the harmonic frequencies fall within the observer bandwidth of the linear active disturbance rejection control (ADC), and harmonic suppression is achieved collaboratively by the ADC and the closed-loop Fourier transform; at high speeds, the harmonic frequencies exceed the observer bandwidth, the observer's estimation capability weakens, but the closed-loop Fourier transform can still independently achieve harmonic compensation; and the frequency selection characteristics of the closed-loop Fourier transform can be adaptively adjusted with the fundamental frequency, and the high-gain peak value moves synchronously with the harmonic frequency.

[0035] The beneficial effects of this invention include:

[0036] (1) Achieve precise suppression of specific harmonics: This invention performs real-time analysis of the current error signal through closed-loop Fourier transform, and can accurately extract the 6th and 12th characteristic harmonic components in a synchronous rotating coordinate system. It also generates corresponding compensation signals through closed-loop adjustment, thereby achieving fixed-point suppression of specific frequency harmonics, which significantly reduces the current harmonic content and improves the current waveform quality.

[0037] (2) Coordinated suppression capability of low-frequency disturbances and high-frequency harmonics: The present invention combines linear active disturbance rejection control and closed-loop Fourier transform in parallel design. The active disturbance rejection control is used to suppress low-frequency broadband disturbances such as parameter changes and load disturbances, while the closed-loop Fourier transform is used to suppress specific high-frequency harmonics. This separates and coordinates the processing of disturbances in different frequency bands, thereby overcoming the shortcomings of traditional single control methods that are difficult to take into account the full frequency domain performance, and realizing the comprehensive optimization control of motor current in the full frequency domain.

[0038] (3) It has good self-adaptive capability under variable speed conditions: The characteristic frequency of the closed-loop Fourier transform in this invention can be adjusted with the motor speed so that it always maintains a corresponding relationship with the harmonic frequency. Therefore, it can still effectively suppress the target harmonic when the motor speed changes, thereby improving the system's adaptability under variable operating conditions. Attached Figure Description

[0039] Figure 1 This is a block diagram illustrating the principle of closed-loop Fourier transform (CFT) harmonic extraction and suppression in an embodiment of the present invention.

[0040] Figure 2 This is a block diagram of the q-axis current loop CFT-LADRC composite control according to an embodiment of the present invention;

[0041] Figure 3 This is the open-loop Bode plot of the q-axis current loop CFT-LADRC composite control system using the method of this invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and technical effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0043] This embodiment provides a method for suppressing current harmonics in a permanent magnet synchronous motor based on closed-loop Fourier transform and active disturbance rejection control. This method operates on the motor current control loop, because the motor's... shaft current loop and The technical steps for shaft current loops are completely identical, and will be described below. Taking the shaft current loop as an example, its specific implementation process is explained, including the following steps:

[0044] Step S1: Current modeling and error signal construction:

[0045] In a synchronous rotating coordinate system, the voltage dynamics of a permanent magnet synchronous motor can be expressed as:

[0046]

[0047] In the formula These are the motor's nominal resistance, direct-axis inductance, quadrature-axis inductance, electric speed, and magnetic flux linkage; for The actual value of the shaft current; for The actual value of the shaft current.

[0048] Considering non-ideal factors such as parameter perturbation, inverter dead-time effect, motor cogging torque, and flux harmonics, the voltage balance equation of a permanent magnet synchronous motor can be expressed as:

[0049]

[0050] in, This refers to the disturbances present in the system.

[0051] The actual three-phase current of the motor is collected and obtained through coordinate transformation. The actual value of the shaft current is compared with the given target value to obtain... Shaft current error:

[0052]

[0053] in For real-time current error, This is a reference value for the current. for The actual value of the shaft current. The shaft error signal serves as the input for subsequent control modules.

[0054] Step S2, Closed-Loop Fourier Transform (CFT) Harmonic Extraction and Suppression: The basic idea of ​​CFT is to extract and suppress harmonics from... Axis current tracking error Harmonic components are extracted and a compensation voltage is generated and fed forward. On the voltage of the shaft. Due to The principle of shaft harmonic suppression and The axis is consistent; the following text only applies to the same axis. Shaft error signal of The analysis focuses on the extraction and compensation process of subharmonics.

[0055] definition The shaft current tracking error is:

[0056]

[0057] In the formula, and They are respectively The amplitudes of the subharmonic waves are decomposed using sine and cosine Fourier transforms. To separate these coefficients, the orthogonality principle of trigonometric functions is used to isolate the errors. Multiply by a synchronously rotating unit sine wave signal respectively Sum and cosine signals .

[0058] According to the product-sum formula, the multiplied signal contains a DC component and... The results for the second harmonic component are as follows:

[0059]

[0060] like Figure 1 As shown, after the signal passes through a low-pass filter (LPF) with a low cutoff frequency, the high-frequency AC components are filtered out, leaving only the DC components proportional to the harmonic amplitude. and .

[0061] Using a closed-loop regulation mechanism based on a PI controller, the extracted DC component is... and The difference is compared with a zero reference value and fed into a set of parallel PI controllers. The PI controllers use their regulation to force the extracted harmonic amplitude coefficients to approach zero in steady state, thereby generating a regulation amount to cancel out harmonics.

[0062] Finally, multiply the output of the PI controller by... and Reconstruct the data and then sum the two results using a gain factor. Amplification yields the final harmonic compensation voltage:

[0063]

[0064] The compensation voltage The output voltage reference value is superimposed onto the current loop in a feedforward manner. or superior.

[0065] Step S3: Linear Active Disturbance Rejection Control (LADRC) Disturbance Observation and Compensation: Construct an extended state observer based on active disturbance rejection control, treating motor parameter changes, load disturbances, and unmodeled dynamics as the total system disturbance. Using the actual current input signal and the system output signal, estimate the total disturbance in real time and generate the corresponding disturbance compensation for subsequent control.

[0066] The controlled object is reconstructed into the following integral-continuous standard form:

[0067]

[0068] make For system input, To control the output, The nominal value of the control gain is usually taken as... , = For the total current disturbance, then The shaft current loop system can be described by the following first-order linear extended state-space equation:

[0069]

[0070] To achieve real-time estimation and compensation of the total disturbance, a second-order linear extended state observer (LESO) is designed. State variables are selected... Tracking system actual output That is, current State variables Tracking total disturbance Construct the following observer equation:

[0071]

[0072] In the formula For observation error, For the observer gain. To simplify the parameter tuning process, the bandwidth parameterization method is used to configure the observer poles, uniformly configuring the poles of the LESO characteristic equation in the left half-plane observer bandwidth. At this point, the relationship between the gain parameter and the bandwidth is:

[0073]

[0074] By adjusting a single parameter This allows for a balance between observation speed and noise suppression capability. It will be able to converge quickly to the total disturbance. After obtaining the total disturbance estimate Then, it is canceled out through a feedforward channel, thereby linearizing the originally nonlinear controlled object into an integral cascade type.

[0075] The control rates of LADRC are as follows:

[0076] .

[0077] Step S4: Function of control signals and system operation mechanism.

[0078] by Taking the shaft current loop as an example, the overall control law of the system The fundamental frequency control voltage of LADRC Harmonic compensation voltage of CFT Linear superposition:

[0079]

[0080] Similarly, the control voltage is obtained. ,but and Obtained through the inverse Park transformation and ,Will and The input space vector pulse width modulation (SVPWM) module generates inverter control signals, which are then used by the inverter to drive the motor.

[0081] In this process, LADRC achieves robust suppression of broadband disturbances in the system, while CFT provides high-gain compensation at the target harmonic frequencies, thus effectively suppressing the 6th and 12th harmonics without affecting system stability. The entire control system structure is as follows: Figure 2 As shown, the LADRC and CFT are connected in parallel to form a CFT-LADRC composite control system, achieving full-frequency domain optimized control of the motor current. The equivalent transfer function of the composite controller can be expressed as:

[0082]

[0083] in:

[0084]

[0085]

[0086] When the motor fundamental frequency The open-loop Bode plots of the CFT-LADRC composite control system at 20Hz, 40Hz, 60Hz, and 80Hz are shown below. Figure 3 As shown, the theoretical correctness of the method of the present invention is proven.

[0087] At a fixed rotational speed, the open-loop gain of the low-frequency system is dominated by LADRC. Its high and low-frequency gains can effectively suppress parameter perturbations and load disturbances, ensuring the steady-state and dynamic performance of the system. At high-frequency harmonics (such as the 6th and 12th harmonics), CFT forms local high-gain peaks through modulation and demodulation. Based on the internal mode principle, the system can achieve zero steady-state error suppression of harmonics at this frequency, realizing precise compensation.

[0088] Under variable speed conditions, such as at low speeds with a fundamental frequency of 20Hz, the characteristic harmonic frequency falls within the bandwidth of the LADRC observer. Harmonic suppression is achieved collaboratively by LADRC and CFT, resulting in better performance. At high speeds, the characteristic harmonic frequency exceeds the LADRC bandwidth, weakening the LESO estimation capability. However, CFT can still independently achieve harmonic compensation. Furthermore, the frequency selectivity of CFT can adaptively adjust with the fundamental frequency, and the high-gain peak shifts synchronously with the harmonic frequency, ensuring harmonic suppression capability under variable speed conditions.

[0089] In terms of stability, CFT only introduces local gain enhancement near the characteristic harmonic frequency, having minimal impact on the phase characteristics at the system cutoff frequency. The stability of the composite system remains dominated by LADRC. At different speeds, the system phase margin remains essentially consistent and always stays within the stable range, without compromising the original stability. Furthermore, as the CFT compensation signal is a known control input, it will not be misinterpreted as disturbance cancellation by the extended state observer, ensuring the decoupling and stability of the composite control.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the implementation process of the present invention has been described in detail above, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for suppressing wide-frequency-domain current harmonics in a permanent magnet synchronous motor, characterized in that, include: Step S1: Obtain the motor's... The current error signal is obtained by subtracting the d-axis current and the d-axis current from the given target current value. Step S2: Use closed-loop Fourier transform to extract the harmonic components in the current error signal and generate a harmonic compensation voltage signal. Step S3: Use linear active disturbance rejection control to... The current of the axial and / or d-axis is controlled to generate a voltage control signal; Step S4: The harmonic compensation voltage signal and the voltage control signal are fused together, and after passing through SVPWM, the control signal of the inverter is generated and applied to the motor to achieve full-frequency domain optimized control of the motor current.

2. The method for suppressing wide-frequency current harmonics in a permanent magnet synchronous motor as described in claim 1, characterized in that, Step S2 specifically includes: In a synchronous rotating coordinate system, the current error signal is multiplied by the unit sine and unit cosine signals corresponding to the harmonic frequencies to be extracted, respectively, using the orthogonality principle of trigonometric functions. The multiplied signals are then passed through low-pass filters to remove the high-frequency AC components, resulting in the DC components. Using a closed-loop regulation mechanism based on a PI controller, the DC component is compared with a zero reference value, and the difference is input to the PI controller to generate the regulation amount. The output of the PI controller is multiplied by the unit sine signal and the unit cosine signal respectively, and the two results are superimposed and amplified by the gain coefficient to obtain the harmonic compensation voltage signal.

3. The method for suppressing wide-frequency current harmonics in a permanent magnet synchronous motor as described in claim 2, characterized in that, The harmonics to be extracted include the 6k harmonic and the 12k harmonic.

4. The method for suppressing wide-frequency current harmonics in a permanent magnet synchronous motor as described in claim 1, characterized in that, Step S3 specifically includes: for The axis is used to reconstruct the controlled object into the following integral cascaded standard form: make For the input of the motor system, This is to control the output, i.e., the voltage control signal. The nominal value of the control gain is usually taken as... , = For the total current disturbance, then... The shaft current loop system can be described by the following first-order linear extended state-space equation: Selecting state variables track Axis current, state variables A second-order linear extended state observer (LESO) is constructed by tracking the total perturbation, and the equation expression is as follows: In the formula For observation error, For observer gain; The observer poles are configured using the bandwidth parameterization method, which unifies the poles of the LESO characteristic equation to the observer bandwidth in the left half-plane. At this point, the relationship between the gain parameter and the bandwidth is: By adjusting a single parameter This allows for a balance between observation speed and noise suppression capability; It will be able to converge quickly to the total disturbance. ; after obtaining the total disturbance estimate Then, it is canceled out through the feedforward channel, thereby linearizing the originally nonlinear controlled object into an integral cascade type; The expression for linear active disturbance rejection control is as follows: ； For the corresponding Reference value for shaft current.

5. The method for suppressing wide-frequency current harmonics in a permanent magnet synchronous motor as described in claim 1, characterized in that, The harmonic compensation voltage signal and the voltage control signal are fused by linear superposition.

6. The method for suppressing wide-frequency current harmonics in a permanent magnet synchronous motor as described in claim 1, characterized in that, In step S4, the control voltage obtained after fusion is input into the SVPWM module after inverse Parker transformation to generate the control signal for the inverter.

7. The method for suppressing wide-frequency current harmonics in a permanent magnet synchronous motor as described in claim 1, characterized in that, At a fixed motor speed, the open-loop gain of the low-frequency system is dominated by linear active disturbance rejection control, while at high-frequency harmonics, the local high gain peak is formed by closed-loop Fourier transform through modulation and demodulation.

8. The method for suppressing wide-frequency current harmonics in a permanent magnet synchronous motor as described in claim 1, characterized in that, Under variable speed operation of the motor: at low speed, the harmonic frequency falls within the observer bandwidth of the linear active disturbance rejection control, and harmonic suppression is completed by the linear active disturbance rejection control and the closed-loop Fourier transform in tandem; at high speed, the harmonic frequency exceeds the observer bandwidth, the observer estimation capability is weakened, but the closed-loop Fourier transform can still independently achieve harmonic compensation; and the frequency selection characteristic of the closed-loop Fourier transform can be adaptively adjusted with the fundamental frequency, and the high gain peak moves synchronously with the harmonic frequency.

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