A high-speed motor harmonic suppression system based on a virtual even fractional order repetitive controller

Abstract

The present application relates to a kind of high-speed motor harmonic suppression system based on virtual even fractional order repetitive controller, the definition of virtual fundamental frequency is proposed, and even harmonic repetitive controller is designed, only the control of even harmonic of virtual fundamental frequency can improve control frequency, enhance dynamic performance;Fractional order delay link based on second-order Lagrange interpolation is used, the decimal part of delay coefficient is fitted, the deviation of system resonance frequency and actual harmonic frequency is reduced, and the accuracy of harmonic suppression is improved;Secondly, low-pass filter with linear phase is used, and low-pass filter is removed from the inner mode of repetitive control, the phase of lag can be accurately compensated, and the tracking error of current harmonic in high frequency band is reduced.The present application can speed up the dynamic response of harmonic suppression, improve the accuracy of harmonic suppression and enhance the robustness of system, so as to effectively reduce motor loss.The system can not only be used for conventional speed motor, but also be more suitable for high-speed and super-speed motor harmonic suppression.

Description

Technical Field

[0001] This invention belongs to the technical field of motor current harmonic suppression, specifically relating to a high-speed motor harmonic suppression system based on a virtual even-order fractional repetitive controller, used to suppress multi-order current harmonics of high-speed motors in AC speed regulation, servo drive and other systems. Background Technology

[0002] High-speed permanent magnet motors, due to their advantages such as compact structure, high energy density, high operating efficiency, and high reliability, have gradually become the mainstream drive unit for AC speed control and servo systems, and are widely used in molecular pumps, centrifugal compressors, electric vehicle drive systems, aerospace, and home appliances. During high-speed operation, the stator current contains a large number of harmonic components, causing severe distortion of the current waveform, resulting in significant losses and severe temperature rise in the motor. Furthermore, fluctuations in motor output torque, unstable speed, and current spikes are also related to current harmonics. Effectively suppressing harmonics is crucial for reducing the temperature of high-speed motors and enhancing their control performance.

[0003] Currently, methods for suppressing current harmonics can be divided into two categories based on the causes of harmonic generation: motor design and control algorithms. Regarding motor design, this type of method reduces air gap magnetic field distortion and suppresses spatial harmonics by improving the design, optimizing electromagnetic parameters, and refining winding distribution and cogging structure. Regarding control algorithms, the main approach is to suppress time harmonics generated by inverter nonlinear characteristics such as switching transistor voltage drop and dead time by optimizing the motor drive algorithm. Repetitive controllers based on the internal model principle can suppress periodic disturbances containing multiple frequency components and are suitable for suppressing multiple harmonics at once. However, conventional repetitive controllers have many problems in practical control systems and are mostly used in grid-connected inverters and inverter power supplies, rarely being validated for their effectiveness in high-speed motors.

[0004] Therefore, in view of the limitations of using conventional repetitive controllers for harmonic suppression, for multi-parameter, strongly coupled, and ultra-high-speed motors, based on the analysis of the harmonic mathematical model, it is necessary to combine the characteristics of high rotational frequency to make up for the shortcomings of traditional single-structure repetitive controllers, and rationally design new composite repetitive controllers to enhance system robustness, improve harmonic suppression accuracy, accelerate convergence speed, and more effectively suppress harmonics and reduce losses.

[0005] Conventional repetitive controllers have the following disadvantages:

[0006] First, conventional repetitive controllers suppress all harmonic components equally, increasing computational complexity and wasting resources. Meanwhile, the presence of N delay units in the internal model also reduces the dynamic performance of conventional repetitive controllers, resulting in slow convergence and long response time.

[0007] Secondly, for conventional repetitive controllers, when the number of delay units N is a fraction, N needs to be approximated to the nearest integer, which reduces the gain of the conventional repetitive controller at each harmonic frequency and seriously affects the harmonic suppression accuracy. Therefore, conventional repetitive controllers can only achieve harmonic suppression at certain fixed frequencies and cannot achieve harmonic suppression at arbitrary frequencies.

[0008] In addition, since the motor speed is very high, the corresponding harmonic frequency is also very high. Conventional repetitive controllers are limited by the bandwidth of the low-pass filter, and the amplitude will be attenuated in the high-frequency region. At the same time, the low-pass filter will also introduce phase lag, and the lag phase will increase with the frequency, and the trend of change cannot be accurately known. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a high-speed motor harmonic suppression system based on a virtual even-order fractional repetitive controller. This system can accurately and quickly suppress harmonics, improve the motor current waveform, effectively reduce motor losses, enhance control performance, and reduce the content of multi-order current harmonics generated by the nonlinear characteristics of the inverter in motor drive control. This invention improves upon conventional repetitive controllers by proposing a virtual fundamental frequency, introducing a fractional fitting stage, and designing an external filter structure, thus forming a high-speed motor harmonic suppression system.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A high-speed motor harmonic suppression system based on a virtual even-order fractional repetitive controller includes: hardware and software components;

[0012] The hardware component includes a DC bus, an IGBT inverter circuit, and a permanent magnet motor; the software component includes a space vector PWM module, a coordinate transformation module, an inverse coordinate transformation module, a speed regulation module, a current regulation module, and a virtual even-order fractional repetitive control module.

[0013] The DC bus is powered by a DC power supply, and the bus voltage U dc The inverter circuit is powered by an integrated power module containing IGBT switching transistors, which output control current to drive the permanent magnet motor. The permanent magnet motor, consisting of the motor body, is the controlled object. The space vector PWM module controls the inverter circuit by generating three-phase PWM signals. The coordinate transformation module transforms the motor current from the ABC three-phase coordinate system to the dq coordinate system for current control. The inverse coordinate transformation module transforms the control quantity from the dq coordinate system to the α-β coordinate system to generate three-phase PWM signals. The speed regulation module and the current regulation module control the speed and current respectively. The virtual even-order fractional repetitive control module tracks the current harmonics to obtain the control quantity.

[0014] The high-speed electrode harmonic suppression system adopts a speed-current dual closed-loop control method, utilizing a speed regulation unit and a current regulation unit for closed-loop control of speed and current respectively; based on the d-axis current i d =0 vector control, based on the d-axis and q-axis current regulation units respectively, with virtual even-order fractional repetitive controllers connected in parallel, the output control quantity is used to suppress current harmonics.

[0015] Furthermore, the system includes an even-order harmonic repetitive control gain, a delay element composed of an integer delay part and a fractional delay part, a low-pass filter, and a phase compensator. By constructing even-order harmonic repetitive control, the delay time is reduced and the system response is accelerated. Polynomial fitting is performed on the fractional delay element to ensure that the resonant frequency of the repetitive control is consistent with the current harmonic frequency, thereby improving the harmonic suppression accuracy. The low-pass filter adopts a linear phase filter to accurately compensate for the phase delay, and the low-pass filter is moved out of the repetitive control inner mode to ensure that the high-speed motor harmonic suppression system has good harmonic suppression characteristics in the high-frequency region.

[0016] Furthermore, the virtual even-order fractional repetitive controller introduces a virtual fundamental frequency, which is three times the true fundamental frequency. The even-order repetitive control is constructed by setting the delay time using the virtual fundamental frequency, generating infinite gain only at the even-order harmonic frequency of the virtual fundamental frequency, without suppressing other order harmonic currents. The control frequency of the virtual even-order fractional repetitive controller is twice the virtual fundamental frequency and six times the true fundamental frequency, effectively improving the convergence speed of harmonic suppression and shortening the system response time.

[0017] Furthermore, in the virtual even-order fractional-order repetitive controller, the fractional-order delay element is fitted using a Lagrange interpolation polynomial to accurately approximate the delay element composed of the fractional part of the ratio of the system sampling frequency to the even-number multiple of the virtual fundamental frequency. Moreover, when the motor fundamental frequency changes, the coefficient of the fractional-order delay element is changed to achieve accurate compensation of the fractional part, so that the resonant frequency of the repetitive control is consistent with the harmonic frequency, thereby improving the harmonic suppression accuracy.

[0018] Furthermore, in the virtual even-order fractional repetitive controller, the low-pass filter adopts an FIR filter with linear phase characteristics, which not only realizes the function of a low-pass filter, but also has a linear relationship between its phase and frequency, which facilitates analysis and accurate compensation; at the same time, by moving the FIR filter out of the internal mode of the repetitive controller, the tracking error of the harmonic suppression system for harmonics in the high-frequency region is effectively reduced, the harmonic suppression capability of the system in the high-frequency region is improved, and the system response bandwidth is increased.

[0019] The principle of this invention is as follows: A repetitive controller based on internal model control can embed the mathematical model of external system signals into the internal control loop. It generates infinite gain at the system's harmonic frequencies (i.e., at external disturbances), thereby achieving zero steady-state error tracking of these disturbances. This makes it suitable for suppressing periodic disturbances containing multiple frequency components. Based on the principle of the repetitive controller, and after analyzing the mathematical model of current harmonics, this invention, combined with the high-frequency characteristics of motors, overcomes the shortcomings of conventional repetitive controllers to create a novel repetitive controller. This improves suppression accuracy, accelerates dynamic performance, and more effectively suppresses multi-order current harmonics.

[0020] The advantages of this invention compared to the prior art are:

[0021] (1) This invention introduces infinite gain only at the even harmonic frequency of the virtual fundamental frequency, without suppressing the odd harmonics of the virtual fundamental frequency, which can enhance the robustness of the system; at the same time, it increases the control frequency of the repetitive controller, which can effectively accelerate the convergence speed of harmonic suppression and improve the dynamic response capability of the system.

[0022] (2) The fractional delay stage proposed in this invention can accurately fit the fractional part of the delay coefficient, improve the harmonic suppression accuracy, and realize harmonic suppression at any speed.

[0023] (3) The present invention designs a low-pass filter with linear phase characteristics, which facilitates accurate compensation for the phase lag generated by the low-pass filter. At the same time, moving it out of the controller internal mode can increase the system bandwidth and enhance the suppression effect on high-frequency current harmonics.

[0024] Based on the above advantages, the present invention is suitable for harmonic suppression of high-speed and ultra-high-speed motors, effectively reducing motor losses caused by harmonics. Attached Figure Description

[0025] Figure 1 This is a block diagram of the overall structure of the harmonic suppression system of the present invention;

[0026] Figure 2 This is a block diagram of the basic internal model structure of the even-order harmonic repetitive controller of the present invention;

[0027] Figure 3 This is a block diagram of the second-order Lagrange interpolation fitting method of the present invention;

[0028] Figure 4(a) shows the low-pass filter structure of a conventional repetitive controller;

[0029] Figure 4(b) shows the low-pass filter structure of the present invention;

[0030] Figure 5 This is a block diagram of the virtual even-order fractional repetitive controller structure of the present invention. Detailed Implementation

[0031] The invention will be further described below with reference to the accompanying drawings.

[0032] like Figures 1-5 As shown, the implementation method of the high-speed motor harmonic suppression system based on a virtual even-order fractional repetitive controller of the present invention is as follows: The harmonic suppression system adopts a speed-current dual closed-loop form, based on the d-axis current i d Vector control with a value of 0 is implemented by connecting a virtual even-order fractional-order repetitive controller in parallel with the d-axis and q-axis current loop PI controllers respectively. The resulting control quantity is used to suppress current harmonics. The virtual even-order fractional-order repetitive controller includes an even-order harmonic repetitive control gain, a delay fitting element, and a low-pass filter. By constructing the even-order harmonic repetitive control, the delay time is reduced and the system response is accelerated. Polynomial fitting is performed on the fractional-order delay element to ensure that the resonant frequency of the repetitive controller is consistent with the current harmonic frequency, thereby improving the harmonic suppression accuracy. The low-pass filter uses a linear phase filter to accurately compensate for the phase delay, and the low-pass filter is moved out of the repetitive controller's internal model to ensure that the system still has good harmonic suppression characteristics in the high-frequency range.

[0033] like Figure 1 As shown, the high-speed motor harmonic suppression system based on a virtual even-order fractional repetitive controller of the present invention includes hardware and software components. The hardware component mainly comprises a DC bus, an IGBT inverter circuit, and a permanent magnet motor; the software component mainly comprises a space vector PWM module, a coordinate transformation module, an inverse coordinate transformation module, a speed regulation module, a current regulation module, and a virtual even-order fractional repetitive control module. dc This is the bus voltage, which supplies power to the inverter circuit; the IGBT inverter circuit is composed of integrated power modules, which internally contain IGBT switching transistors and output control current to drive the permanent magnet motor; the permanent magnet motor, composed of the motor body, is the controlled object. The space vector PWM module controls the inverter circuit by generating three-phase PWM signals; the coordinate transformation module converts the motor current i u i v i w Current i transformed from the ABC three-phase coordinate system to the dq coordinate system d and i q Used for current control; the inverse coordinate transformation module transforms the control quantity from the dq coordinate system to the α-β coordinate system to generate a three-phase PWM signal; the speed regulation module and the current regulation module perform closed-loop control of speed and current respectively, where ω ref The reference speed is ω, and the actual speed fed back is i. dref i is the d-axis reference current. qref The current is the q-axis reference current; the virtual even-order fractional repetitive control module tracks the current harmonics to obtain control quantities for suppressing the current harmonics.

[0034] like Figure 2 The diagram shown is a basic internal model structure block diagram of the even-order harmonic repetitive controller of this invention. Existing conventional repetitive controllers calculate the delay period based on the fundamental frequency of the motor rotation. However, current harmonics are represented as 6n harmonics in the dq coordinate system. Therefore, the processing of non-6n harmonics in conventional repetitive controllers increases the delay time, significantly consuming system hardware computing resources, reducing convergence speed, and hindering harmonic suppression during high-speed motor operation. Considering that the harmonic frequency is 3 times the fundamental frequency (3ω... r If the frequency is an even multiple of ω′, then this invention introduces a “virtual base frequency” ω′. r , i.e. ω′ r =3ω r Construct an even-order repetitive controller to suppress only the virtual fundamental frequency ω′ r The 2nth harmonic. R in (s) represents the input quantity of the internal mold structure, R out (s) represents the output of the internal model structure. The expression for the internal model structure of this even-order harmonic repetitive controller is as follows:

[0035]

[0036] Where N' is the control coefficient of the even-order harmonic repetitive controller, N′=f s / f′ r =T′ r / T s =2π / (ω′) r ·T s ), f s f is the system sampling frequency. r f′ is the fundamental frequency of the motor's rotation. r For virtual baseband, T s Let T′ be the system sampling time. r Let s be the virtual period, representing the complex variable of the internal model structure transfer function in the continuous domain. The virtual fundamental even-order harmonic repetitive controller operates only at the 6nth harmonic frequency. Compared to conventional repetitive controllers, this invention can reduce the delay time to N′ / 6 sampling periods, and the control frequency is 6 times that of conventional repetitive controllers, significantly improving the control frequency of the repetitive controller.

[0037] like Figure 3 The diagram shown is a block diagram of the second-order Lagrange interpolation fitting method of the present invention. This represents a complete delay unit. When N′ / 2 is not an integer, it can be decomposed into an integer part Z and a fractional part F. F is a fractional delay element. Since F is a fraction, a fractional delay element cannot be directly implemented in engineering. Therefore, the fractional delay element can be approximated by the Lagrange interpolation method, as shown in equation (2). This can make the resonant frequency of the repetitive control consistent with the frequency of the current harmonics, thereby improving the accuracy of harmonic suppression.

[0038]

[0039] In the formula, m is the order of the Lagrange interpolation polynomial, and L... i Let m be the coefficients of each term in the polynomial, and j be the calculation factor. A higher order m results in a better fit to the polynomial, but also significantly increases the computational load. In high-speed motor control systems, rapid parameter adjustment is required; therefore, this invention uses second-order Lagrange interpolation to approximate the fractional-order delay element. That is:

[0040]

[0041] In the formula, L0, L1 and L2 are the coefficients of the three subterms of the second-order Lagrange interpolation polynomial.

[0042] Figures 4(a) and 4(b) show a comparative schematic diagram of low-pass filter structures. Figure 4(a) shows the low-pass filter structure of a conventional repetitive controller, and Figure 4(b) shows the low-pass filter structure of the present invention. It can be seen that the position and type of the low-pass filter of the present invention are different from those of the conventional repetitive controller.

[0043] The transfer function expression in Figure 4(a) is:

[0044]

[0045] The transfer function expression in Figure 4(b) is:

[0046]

[0047] Define variable ω c Given the cutoff frequency of the low-pass filter, comparing the denominators of equations (4) and (5), it can be seen that only when the harmonic frequency ω is... k ∈(0,ω c When the frequency is as low as possible below the cutoff frequency, the low-pass filter F(s) can be approximated as a constant 1, and the denominator of equation (4) will be close to 0, so that the conventional repetitive controller can effectively suppress harmonic interference.

[0048] For equation (5), since the low-pass filter F(s) is moved to the outside of the repetitive controller internal model structure, the denominator does not contain F(s). The condition that the denominator is close to 0 is not limited by the bandwidth of the low-pass filter, which improves the accuracy of the system resonant frequency tracking the harmonic frequency in the high-frequency band, thereby enhancing the system's harmonic suppression capability in the high-frequency band. In the mid-low frequency band, the denominator of equation (5) also maintains a small deviation from 0, which also ensures the system's good harmonic suppression performance in the mid-low frequency band.

[0049] To further reduce harmonic tracking error, the low-pass filter F(s) shown in Figure 4(b) is a linear-phase FIR filter, which satisfies the characteristics of a low-pass filter and whose phase is linearly related to the frequency. The general expression for the FIR filter F(z) is as follows:

[0050]

[0051] Where K represents the order of the FIR filter, b(i) represents the coefficients of the FIR filter, and z represents the complex variable in the discrete domain. When b(i) is even-symmetric about (K-1) / 2, the phase of the FIR filter can be expressed as follows:

[0052]

[0053] Here, arg[] represents the operator for calculating the phase of F(z). For frequencies ω∈(0,ω... c The phase lag of a conventional low-pass filter increases significantly with increasing frequency, and the trend of this change cannot be accurately determined; while F(s) is an FIR filter with linear phase, and the phase lag is... It is proportional to the frequency ω, which can be accurately determined and compensated for, eliminating the frequency tracking error caused by the phase lag of the low-pass filter and increasing the system bandwidth.

[0054] like Figure 5 The diagram shown is a block diagram of the virtual even-order fractional-order repetitive controller structure of the present invention, with the d-axis current loop as an example. e Even-order harmonic repetitive control gain, The delay stage comprises an integer delay and a fractional delay. F(s) is an FIR low-pass filter, and C(s) is a phase compensator. These stages together constitute the virtual even-order harmonic fractional repetitive controller G. vefrc (s). Furthermore, i d,q Indicates the d-axis and q-axis feedback current, i d,qref G represents the reference current for the d-axis and q-axis. c(s) represents the current regulation module, D(s) represents the current harmonic disturbance, and G(s) represents the transfer function of the permanent magnet motor. By constructing even-order harmonic repetitive control, the delay time can be reduced and the system response can be accelerated. Polynomial fitting is performed on the fractional-order delay element to ensure that the resonant frequency of the repetitive control is consistent with the current harmonic frequency, thereby improving the harmonic suppression accuracy. The low-pass filter F(s) adopts a linear-phase FIR filter, which can accurately compensate for the phase delay and shift F(s) out of the repetitive control inner mode to ensure that the system still has good harmonic suppression characteristics in the high-frequency region. By adding a virtual even-order fractional-order repetitive controller to the overall control system, the 6nth harmonic generated by the nonlinear characteristics of the inverter in the d-axis and q-axis current loops can be effectively suppressed.

[0055] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A high-speed motor harmonic suppression system based on a virtual even-order fractional repetitive controller, characterized in that, include: Hardware and software components; The hardware component includes a DC bus, an IGBT inverter circuit, and a permanent magnet motor; the software component includes a space vector PWM module, a coordinate transformation module, an inverse coordinate transformation module, a speed regulation module, a current regulation module, and a virtual even-order fractional repetitive control module. The DC bus is powered by a DC power supply, and the bus voltage... U dc The inverter circuit is powered by an integrated power module containing IGBT switching transistors, which output control current to drive the permanent magnet motor. The permanent magnet motor, consisting of the motor body, is the controlled object. The space vector PWM module controls the inverter circuit by generating three-phase PWM signals. The coordinate transformation module transforms the motor current from the ABC three-phase coordinate system to the dq coordinate system for current control. The inverse coordinate transformation module transforms the control quantity from the dq coordinate system to the α-β coordinate system to generate three-phase PWM signals. The speed regulation module and the current regulation module control the speed and current respectively. The virtual even-order fractional repetitive control module tracks the current harmonics to obtain the control quantity. The high-speed motor harmonic suppression system adopts a speed-current dual closed-loop control form, which uses a speed regulation unit and a current regulation unit to perform closed-loop control on speed and current respectively. Based on d-axis current i d =0 vector control, based on the d-axis and q-axis current regulation units respectively, connects virtual even-order fractional repetitive controllers in parallel, and the output control quantity is used to suppress current harmonics; The virtual even-order fractional repetitive controller introduces a virtual fundamental frequency, which is three times the true fundamental frequency. The even-order repetitive control is constructed by setting the delay time with the virtual fundamental frequency. Infinite gain is generated only at the even-order harmonic frequency of the virtual fundamental frequency, without suppressing other order harmonic currents. In the virtual even-order fractional repetitive controller, the fractional delay element is fitted using a Lagrange interpolation polynomial; and when the motor fundamental frequency changes, the fractional part is accurately compensated by changing the coefficients of the fractional delay element, so that the resonant frequency of the repetitive control remains consistent with the harmonic frequency. In the virtual even-order fractional repetitive controller, the low-pass filter is an FIR filter with linear phase characteristics, and the FIR filter is moved out of the internal model of the repetitive controller.

2. The high-speed motor harmonic suppression system based on a virtual even-order fractional repetitive controller according to claim 1, characterized in that: It includes even-order harmonic repetitive control gain, a delay element consisting of integer and fractional delay parts, a low-pass filter, and a phase compensator; by constructing even-order harmonic repetitive control, the delay time is reduced and the system response is accelerated; polynomial fitting is performed on the fractional delay element to make the resonant frequency of the repetitive control consistent with the current harmonic frequency, thereby improving the harmonic suppression accuracy. The low-pass filter uses a linear phase filter to accurately compensate for the phase delay, and the low-pass filter is moved out of the repetitive control inner mode to ensure that the high-speed motor harmonic suppression system has good harmonic suppression characteristics in the high-frequency region.

3. The high-speed motor harmonic suppression system based on a virtual even-order fractional repetitive controller according to claim 2, characterized in that: The control frequency of the virtual even-order fractional repetitive controller is twice the virtual fundamental frequency and six times the true fundamental frequency, which effectively improves the convergence speed of harmonic suppression and shortens the system response time.

4. The high-speed motor harmonic suppression system based on a virtual even-order fractional repetitive controller according to claim 1, characterized in that: The fractional delay stage is fitted using a Lagrange interpolation polynomial to accurately approximate the delay stage consisting of the fractional part of the ratio of the system sampling frequency to the even multiple of the virtual fundamental frequency.

5. The high-speed motor harmonic suppression system based on a virtual even-order fractional repetitive controller according to claim 2, characterized in that: FIR filters with linear phase characteristics not only function as low-pass filters, but their phase is also linearly related to the frequency, which facilitates analysis and accurate compensation. By moving the FIR filter out of the internal mode of the repetitive controller, the tracking error of the harmonic suppression system in the high-frequency region can be effectively reduced, the harmonic suppression capability of the system in the high-frequency region can be improved, and the system response bandwidth can be increased.

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