A method for extracting positive and negative sequence components of motor harmonic current based on SOGI

Abstract

This invention discloses a method for extracting positive and negative sequence components of motor harmonic current based on SOGI. By preprocessing the dq-axis current in a synchronous rotating coordinate system by subtracting a setpoint, the fundamental DC component is eliminated, overcoming the limitation of traditional SOGI in filtering DC components. An MRF-SOGI module is built, utilizing the hysteresis-free harmonic extraction characteristics of SOGI to generate orthogonal signal pairs. Linear computation is used to accurately extract the instantaneous values ​​of positive and negative sequence harmonic currents of the motor, particularly suitable for extracting the 5th negative sequence and 7th positive sequence harmonic components. This method features low computational complexity, fast dynamic response, and high extraction accuracy. The resonant frequency can be adaptively adjusted according to the motor's electrical angular velocity, making it suitable for various motors using field-oriented control. It requires no modification to existing control system hardware, achieving both precise harmonic current suppression and controllable harmonic current injection, thus possessing both engineering practicality and versatility.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, specifically relating to a method for extracting positive and negative sequence components of motor harmonic current based on SOGI. Background Technology

[0002] In the field of motor control, especially in permanent magnet synchronous motor control systems employing FOC (Field-Oriented Control) strategies, factors such as inverter dead time, transistor voltage drop, and inherent motor nonlinearity can lead to a large number of positive and negative sequence harmonic components in the motor stator current. These harmonic components not only reduce motor operating efficiency and increase losses but also affect motor control accuracy and stability. Therefore, accurately and quickly extracting the positive and negative sequence components of the motor harmonic current is a crucial prerequisite for achieving harmonic suppression and optimizing motor control performance.

[0003] In existing technologies, the extraction methods for positive and negative sequence components of harmonic current mainly include the averaging method, the identification method based on fast Fourier transform, the multi-synchronous rotating coordinate system with low-pass filtering, and the quasi-resonant filtering (QR). Among them, the averaging method, the fast Fourier transform method, and the multi-synchronous rotating coordinate system with low-pass filtering method [Liao Yong, Zhen Shuai, Liu Ren. Suppressing torque pulsation of permanent magnet synchronous motor by harmonic injection [J]. Proceedings of the CSEE, 2011, 31(21): 119-127] have defects such as high computational complexity and poor real-time performance; the extraction method based on QR [Tang Zhen, Zhang Peng, Yu Zichun. PMSM current control method based on quasi-proportional resonant disturbance observer [J]. Micromotors, 2025, 53(09): 65-70] are greatly affected by the motor model, have low extraction accuracy, and cannot separate positive and negative sequence harmonic components.

[0004] Second-order generalized integrators (SOGIs) possess advantages such as simple structure, low computational complexity, and strong frequency adaptability, and have been applied in signal filtering and fundamental frequency extraction in motor control. However, in current technologies, SOGIs are mainly used for phase-locked loops in power grids and harmonic extraction in two-phase stationary coordinate systems of motors (which involves more complex designs). There is currently no technical solution to directly apply SOGIs to synchronous rotating coordinate systems to achieve direct extraction of the positive and negative sequence components of motor harmonic currents. This cannot meet the requirements of FOC (Field-Oriented Control) motors for real-time, accurate, and universal harmonic extraction. Therefore, there is an urgent need for a method that can overcome the shortcomings of existing technologies, adapt to FOC control scenarios, and directly extract the positive and negative sequence components of harmonic currents. Summary of the Invention

[0005] To address the shortcomings of existing technologies, such as low accuracy, poor real-time performance, complex calculations, and limited applicability of motor harmonic current positive and negative sequence components extraction, this invention provides a method for extracting motor harmonic current positive and negative sequence components based on SOGI. This method enables direct extraction of the positive and negative sequence components of harmonic current, improves extraction accuracy and real-time performance, reduces computational complexity, and is compatible with all motors using FOC control and equipped with a synchronous rotating coordinate system.

[0006] A method for extracting positive and negative sequence components of motor harmonic current based on SOGI includes the following steps: (1) Collect the three-phase current, mechanical speed and rotor position angle of the motor; (2) Obtain the dq axis current through coordinate transformation and perform DC component removal preprocessing on it; (3) Input the pre-processed dq-axis current into SOGI to obtain the dq-axis harmonic current and quadrature signal corresponding to the resonant frequency; (4) Perform linear operations on the dq axis harmonic current and the orthogonal signal to obtain the instantaneous values ​​of the positive and negative sequence harmonic currents of the target frequency in the dq coordinate system.

[0007] Furthermore, in step (2), constant phase amplitude transformation or constant power transformation is used to transform the three-phase current to the dq coordinate system to obtain the corresponding dq axis current.

[0008] Furthermore, in step (2), the DC component of the dq-axis current is preprocessed by eliminating the DC component using the following expression:

[0009] in: i d and i q These are the d-axis current and q-axis current of the motor, respectively. and These are the d-axis current reference values ​​and the q-axis current reference values, respectively. i derror and i qerror These are the pre-processed d-axis current and q-axis current, respectively.

[0010] Furthermore, the transfer function of SOGI in step (3) is as follows:

[0011]

[0012] in: K This is the gain coefficient of SOGI. ω g The resonant frequency, sFor the Laplace operator, i derror and i qerror These are the preprocessed d-axis current and q-axis current, respectively. i dh and i qh These are the d-axis harmonic current and q-axis harmonic current corresponding to the resonant frequency, respectively. qi dh and qi qh These are the d-axis orthogonal signals and q-axis orthogonal signals corresponding to the resonant frequency, respectively.

[0013] Furthermore, in step (4), the dq-axis harmonic current and quadrature signal are linearly calculated using the following expression:

[0014] in: and 6 respectively k The d-axis and q-axis components of the -1st negative sequence harmonic current. and 6 respectively k The d-axis and q-axis components of the +1st positive sequence harmonic current. k It is a positive integer.

[0015] Furthermore, the resonant frequency is 6 times the electrical angular frequency of the motor. k By setting the multiplier, the positive and negative sequence harmonic currents of the corresponding frequency can be extracted.

[0016] Furthermore, by inputting the instantaneous values ​​of the extracted positive and negative sequence harmonic currents in the dq coordinate system into the motor control system, the goal of harmonic current suppression or accurate harmonic current injection can be achieved.

[0017] A computer device includes a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the above-described SOGI-based method for extracting positive and negative sequence components of motor harmonic current.

[0018] A computer-readable storage medium storing a computer program, which, when executed by a processor, implements the above-described SOGI-based method for extracting positive and negative sequence components of motor harmonic current.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: 1. Direct extraction of positive and negative sequence components. This invention directly applies a second-order generalized integrator to a synchronous rotating coordinate system, eliminating the need for complex coordinate transformation iterations or multiple filtering steps. It can directly extract the positive and negative sequence components of the motor harmonic current, simplifying the extraction process, reducing computational complexity, and improving real-time extraction performance.

[0020] 2. High extraction accuracy. The SOGI method used in this invention has frequency adaptive capability, which can adaptively adjust parameters according to the motor operating conditions, effectively filtering out the fundamental component and noise interference, accurately separating the positive and negative sequence components of the harmonic current, and achieving extraction accuracy superior to existing traditional methods; simulation verification shows that the optimal method is selected. K The value is designed to balance convergence speed and accuracy, and the maximum error of harmonic extraction is within 5% under multiple operating conditions of the motor.

[0021] 3. Wide applicability. The method of this invention is applicable to all motors that use FOC control and have a synchronous rotating coordinate system, especially permanent magnet synchronous motors. No customized modifications are required for specific motor types, making it highly versatile.

[0022] 4. Easy to integrate and implement. The method of this invention has a simple structure and low computational load, and can be directly integrated into the existing motor FOC control system without the need for a large number of new hardware devices, resulting in low implementation cost and easy engineering application.

[0023] 5. Improved motor control performance. By accurately extracting the positive and negative sequence components of harmonic current, this invention provides reliable support for motor harmonic suppression, torque ripple suppression, and other control strategies, effectively reducing motor losses and improving motor operating efficiency and control stability. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the control flow of the method for extracting positive and negative sequence components of motor harmonic current according to the present invention.

[0025] Figure 2 This is a schematic diagram of the control flow of a typical SOGI.

[0026] Figure 3 This is a schematic diagram illustrating the relative relationship between the dq coordinate system and the SOGI coordinate system in this invention.

[0027] Figure 4 This is a schematic diagram of the simulation waveform for extracting positive sequence harmonic current in Embodiment 1 of the present invention.

[0028] Figure 5 This is a control flow diagram of the motor current loop in Embodiment 2 of the present invention.

[0029] Figure 6 A schematic diagram of current loop control for harmonic current injection in a traditional multi-synchronous rotating coordinate system.

[0030] Figure 7 This is a schematic diagram of the simulated waveform of harmonic injection in Embodiment 2 of the present invention. Detailed Implementation

[0031] To describe the present invention in more detail, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] The present invention is based on the SOGI method for extracting positive and negative sequence components of motor harmonic current (denoted as MRF-SOGI). It extracts positive and negative sequence harmonic currents (signals) by constructing orthogonal signal pairs using a second-order generalized integrator in the dq synchronous rotating coordinate system. This is the core idea of ​​the present invention.

[0033] Example 1 In this embodiment, the three-phase currents of the permanent magnet synchronous motor are extracted separately. i a , i b , i c Taking the negative-sequence fifth harmonic component and the positive-sequence seventh harmonic component as examples of their corresponding sixth harmonic components in a synchronously rotating coordinate system along the dq axis. Clearly, this embodiment does not mean that the present invention can only be used to extract the 5th and 7th harmonics; it can be used for all 6th harmonics. k -1st order negative sequence harmonic current and 6 k The +1 positive sequence harmonic current can be changed simply by altering the resonant frequency of the second-order generalized integrator.

[0034] like Figure 1 As shown, the method for extracting positive and negative sequence harmonic currents of a motor in this embodiment includes the following steps: Step S1: Sample the three-phase current of the motor and obtain the current rotor position angle of the motor through the encoder. With mechanical speed For the extreme logarithm is P The motor, its electrical angle With electrical angular frequency for:

[0035] Step S2: Using the transformation matrix from the three-phase stationary coordinate system to the orthogonal synchronous rotating coordinate system (dq coordinate system), the components of the three-phase current in the orthogonal coordinate system are obtained. In this embodiment, constant phase amplitude transformation is used uniformly. For constant power transformation, there is no essential difference and it will not change the core logic of the method for extracting positive and negative sequence components of motor harmonic current in this invention.

[0036] The coordinate transformation expression is as follows:

[0037] Step S3: To eliminate the interference of DC components on the harmonic extraction accuracy of MRF-SOGI (because SOGI itself does not have DC attenuation characteristics and cannot filter out DC bias), it is necessary to process the orthogonal current components obtained after coordinate transformation. i d , i q Perform DC component rejection preprocessing.

[0038] The fundamental current loop of the current control system is currently in normal operation. At this time, the fundamental component (i.e., the DC component) in the dq axis current can quickly converge to the current setpoint within a finite time. and (The original output setpoint of the velocity loop). Therefore, this embodiment preprocesses the transformed dq-axis current by subtracting the corresponding target value from the dq current. and Obtain the error signal of the dq current. i derror and i qerror ,Right now:

[0039] This is one of the key features of the present invention, which ensures that the subsequent typical SOGI can effectively extract the harmonic components in the current and reduce the influence of the DC component of the dq current (corresponding to the fundamental component of the three-phase current).

[0040] Step S4: Input the current deviation signal into SOGI to obtain the harmonic current corresponding to the resonant frequency. i dh , i qh and their corresponding orthogonal signals qi dh , qi qh .

[0041] like Figure 2 As shown, a typical SOGI includes integration and feedback processes to form a resonant circuit, which can track the resonant frequency without hysteresis. ω g Harmonic signals at the location.

[0042] SOGI has frequency adaptive capability, allowing for real-time input of the desired harmonic current frequency. In this embodiment, the frequency of the harmonic current in the three-phase current in the dq coordinate system is 6. kω e Therefore, the resonant frequency of SOGI needs to be set to 6kHz. ω e SOGI can extract 6 from the dq axis. k -1 and 6k The +1st three-phase harmonic current component is denoted as... v d6k , v q6k , qv d6k , qv q6k Because SOGI possesses excellent adaptive resonant frequency characteristics, therefore the resonant frequency... ω g It can change in real time to adapt to the real-time operating conditions of the motor. In this embodiment, the goal is to extract the 5th and 7th currents, therefore the input resonant frequency is 6. ω e .

[0043] Figure 2 In K Let SOGI be the gain coefficient, when K When the value of is large (1~10), SOGI can converge quickly, but the steady-state accuracy is poor; when K When the value is relatively small (0~1), SOGI convergence speed is slow, but the tracking accuracy of harmonic signals is high. The selected value in this embodiment... K The value is 0.1~0.5, balancing convergence speed and accuracy.

[0044] In the MRF-SOGI system, the orthogonal signal pairs are first separated by utilizing SOGI's hysteresis-free harmonic extraction capability. The SOGI transfer function is:

[0045] in: K For SOGI gain, ω g It is the resonant angular frequency. For a tracking signal that is in phase with the input, To be consistent with the input signal v Orthogonal (90° lag) o () signal.

[0046] Step S5: The quadrature pair signal output by SOGI (denoted as...) v d6k , v q6k , qv d6k , qv q6k By performing linear operations, the instantaneous values ​​of the positive and negative sequence harmonic currents of the target frequency in the dq coordinate system can be output; this operation is based on the relationship between multiple synchronous rotating coordinate systems, specifically: dq synchronous rotating coordinate system towards 6 k -1 rotation of the coordinate system and 6 kThe transformation matrix for the +1th rotation of the coordinate system is:

[0047]

[0048] After coordinate transformation, the corresponding harmonic current is equivalent to being mapped from the dq synchronous rotating coordinate system to the multi-synchronous rotating coordinate system, and is expressed as a DC component.

[0049] Since the frequencies of both positive and negative sequence harmonic currents in the dq coordinate system are 6... kω e Therefore, SOGI can separate harmonic currents that are a mixture of positive and negative sequence currents, through Figure 3 The coordinate system shown in the figure has a relative relationship, and d in the figure k q k for k Orthogonal coordinate axes of the secondary synchronous rotating coordinate system k The orthogonal component of the subharmonic current after coordinate transformation falls on d k q k On the axis, v kSOGI , qv kSOGI For the orthogonal axes output by SOGI, k The orthogonal component of the subharmonic current after passing through SOGI falls within v kSOGI , qv kSOGI On the axis, the relationship between the positive and negative sequence harmonic currents and the SOGI output signal can be obtained:

[0050] in: k =1,2,3…, for j Phase of the second harmonic current.

[0051] In this embodiment, it is equivalent to k When the value is 1, a specific linear operation expression is obtained:

[0052] After preprocessing, SOGI extraction, and linear operation, the orthogonal components of the negative-sequence 5th harmonic current and the 7th-sequence positive harmonic current vectors in the dq coordinate system can be obtained. i d5 , i q5 , i d7 , i q7Since this invention is based on SOGI and multiple rotating coordinate systems, it is called the MRF (Multi-Rotating Coordinate System)-SOGI Harmonic Current Extraction Method.

[0053] Figure 4 The Simulink simulation results q7_MSOGI used in this embodiment to extract the q-axis component of the positive sequence 7th current harmonic in the dq coordinate system of an SPM motor under multiple operating conditions (including sudden load increase and speed change). The simulation model parameters are shown in Table 1. Figure 4 q7_AVE in the figure is the result of extracting DC in the 7-time synchronous rotating coordinate system using the average value method and then transforming it back to the dq coordinate system. Its accuracy is extremely high and very close to the true value. It can be seen that the harmonic current extracted by this invention has a small deviation from the actual harmonic current and high extraction accuracy.

[0054] Table 1

[0055] Compared with the average value method mentioned above, this invention has a smaller computational load, lower memory requirements for the control chip, and can converge quickly under multiple motor operating conditions (rapid dynamic response). It also has adaptive performance for multiple motor speeds (i.e., electrical frequencies) and high accuracy in harmonic current extraction (the extraction errors of both harmonic current amplitude and phase are much less than 5%).

[0056] Example 2 Figure 5 The control flow for a motor harmonic current suppression or hysteresis-free and steady-state error-free harmonic current injection control system using the MRF-SOGI module is as follows: (1) Same as steps S1 to S5 in Example 1, obtain i d , i q , θ e , ω e The harmonic components of the positive and negative sequence harmonic current vectors in the dq orthogonal coordinate system are obtained using MRF-SOGI. i d5 , i q5 , i d7 , i q7 .

[0057] (2) For the fundamental current part of the control system, a PI (proportional-integral) controller (usually requiring decoupling) or ADRC (active disturbance rejection controller) is used to implement the current loop control function. and It is the dq current reference value, which is the output of the speed loop in the front end.

[0058] (3) For the harmonic current suppression (or injection) part of the control system, this embodiment sets the resonant angular frequency of SOGI to 6. ω e By pairing the orthogonal signals after linear operations i dq5 , i dq7 Transformation using the transformation matrix in step S5 of Example 1 (i.e. Figure 5 The coordinate systems dq-d5q5 and dq-d7q7 are rotated to the 5th and 7th synchronous coordinate systems, respectively. i d5 , i q5 , i d7 , i q7 It will be represented as direct flow.

[0059] (4) The transformed harmonic current is controlled using a PI controller or ADRC, with the given DC reference being... , , , Transform the controller output back to the dq0 synchronous rotating coordinate system to obtain... u dh , u qh This is then added to the controller output of the fundamental current loop to obtain the d-axis and q-axis reference voltages in the dq coordinate system. Through the dq0-abc transformation, the three-phase reference input voltage is finally obtained. , , The actual input voltage is obtained through a PWM (Pulse Width Modulation) or SVPWM (Space Vector Pulse Width Modulation) inverter. u a , u b , u c .

[0060] If the harmonic current reference value is set to 0, the main function of this system is to suppress the sixth harmonic component in the dq current. The harmonic extraction capability of MRF-SOGI is not fully utilized, and its advantage over the traditional harmonic suppression method using a Q-PR (quasi-proportional resonance) controller is not significant. If the harmonic current reference value is not 0, the main function of this system is to actively inject positive and negative sequence harmonic currents of specific amplitude and phase. This embodiment uses MRF-SOGI to extract harmonic current, avoiding the dependence on the motor model of the traditional Q-PR injection method, and eliminating the need to consider amplitude and phase frequency compensation of the system; only gain adjustment is required. KThe design is simple and quick.

[0061] Figure 6 For traditional multi-synchronous rotating coordinate system positive and negative sequence harmonic current injection control structures, the traditional method involves... i a , i b , i c Transform them into a multi-synchronous rotating coordinate system respectively to obtain... i d , i q , i d5 , i q5 , i d7 , i q7 For fundamental current i d , i q The fundamental control voltage is obtained through a current controller. u d , u q For harmonic currents, the DC component is first extracted using an LPF (low-pass filter), and then the DC component is input to a current controller to obtain the harmonic control voltage. u d5 , u q5 , u d7 , u q7 The control voltage is transformed back to the three-phase stationary coordinate system and superimposed to obtain the given three-phase voltage. , , The three-phase voltage of the actual input motor is obtained through an inverter. The main drawback of the traditional method is that the LPF introduces additional hysteresis, which leads to a deterioration in the dynamic performance of the system. In addition, the filtering performance of ordinary digital filters is limited, and they often cannot separate the DC component well, which can lead to overall system instability in severe cases.

[0062] Based on this embodiment, MRF-SOGI has high extraction accuracy and rapid dynamic response, and inherits the characteristic of SOGI's harmonic extraction without hysteresis. As a result, the system has a fast convergence speed, stronger harmonic suppression capability, and stronger harmonic tracking capability.

[0063] The system shown in this embodiment was simulated in Simulink. The controlled object was an SPMSM (surface-mounted permanent magnet synchronous motor). The inverter had a 10μs dead zone, and the simulation step size was 10. -7s, to perform harmonic current injection control, Figure 7 The waveforms of harmonic current in the corresponding synchronous rotating coordinate system are shown. In the figure, d5, q5, d7, and q7 are the DC components of the d and q axes in the 5th and 7th synchronous rotating coordinate systems of the motor, respectively. The motor is in an acceleration state before 0.03s, and the motor speed stabilizes after 0.03s. It can be seen that the harmonic current in the motor quickly converges to the given value after stabilization. A constant torque load is suddenly applied at 0.1s, and the target speed is halved at 0.2s. It can be seen that the harmonic current in the motor can converge quickly under various operating conditions.

[0064] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. Those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A method for extracting positive and negative sequence components of motor harmonic current based on SOGI, characterized in that, Includes the following steps: (1) Collect the three-phase current, mechanical speed and rotor position angle of the motor; (2) Obtain the dq axis current through coordinate transformation and perform DC component removal preprocessing on it; (3) Input the pre-processed dq-axis current into SOGI to obtain the dq-axis harmonic current and quadrature signal corresponding to the resonant frequency; (4) Perform linear operations on the dq axis harmonic current and the orthogonal signal to obtain the instantaneous values ​​of the positive and negative sequence harmonic currents of the target frequency in the dq coordinate system.

2. The method for extracting positive and negative sequence components of motor harmonic current based on SOGI according to claim 1, characterized in that: In step (2), constant phase amplitude transformation or constant power transformation is used to transform the three-phase current to the dq coordinate system to obtain the corresponding dq axis current.

3. The method for extracting positive and negative sequence components of motor harmonic current based on SOGI according to claim 1, characterized in that, In step (2), the DC component of the dq-axis current is preprocessed by eliminating the following expression: in: i d and i q These are the d-axis current and q-axis current of the motor, respectively. and These are the d-axis current reference values ​​and the q-axis current reference values, respectively. i derror and i qerror These are the pre-processed d-axis current and q-axis current, respectively.

4. The method for extracting positive and negative sequence components of motor harmonic current based on SOGI according to claim 1, characterized in that, The transfer function of SOGI in step (3) is as follows: in: K This is the gain coefficient of SOGI. ω g The resonant frequency, s For the Laplace operator, i derror and i qerror These are the preprocessed d-axis current and q-axis current, respectively. i dh and i qh These are the d-axis harmonic current and q-axis harmonic current corresponding to the resonant frequency, respectively. qi dh and qi qh These are the d-axis orthogonal signals and q-axis orthogonal signals corresponding to the resonant frequency, respectively.

5. The method for extracting positive and negative sequence components of motor harmonic current based on SOGI according to claim 1, characterized in that, In step (4), the dq-axis harmonic current and quadrature signal are linearly calculated using the following expression: in: and 6 respectively k The d-axis and q-axis components of the -1st negative sequence harmonic current. and 6 respectively k The d-axis and q-axis components of the +1st positive sequence harmonic current. k It is a positive integer. i dh and i qh These are the d-axis harmonic current and q-axis harmonic current corresponding to the resonant frequency, respectively. qi dh and qi qh These are the d-axis orthogonal signals and q-axis orthogonal signals corresponding to the resonant frequency, respectively.

6. The method for extracting positive and negative sequence components of motor harmonic current based on SOGI according to claim 5, characterized in that: The resonant frequency is 6 times the electrical angular frequency of the motor. k By setting the multiplier, the positive and negative sequence harmonic currents of the corresponding frequency can be extracted.

7. The method for extracting positive and negative sequence components of motor harmonic current based on SOGI according to claim 1, characterized in that: By inputting the instantaneous values ​​of the extracted positive and negative sequence harmonic currents in the dq coordinate system into the motor control system, the goal of harmonic current suppression or accurate harmonic current injection can be achieved.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: The processor is used to execute the computer program to implement the SOGI-based method for extracting positive and negative sequence components of motor harmonic current as described in any one of claims 1 to 7.

9. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by the processor, it implements the SOGI-based method for extracting positive and negative sequence components of motor harmonic current as described in any one of claims 1 to 7.

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