A beatless method based on current feedback frequency compensation

Abstract

This invention relates to a beat-free method based on current feedback frequency compensation, comprising the following steps: configuring an AD sampling module for sampling the three-phase current i of the motor in the main topology of the traction converter of a high-speed train. a i b i c Data acquisition is performed; a low-pass filter is configured to filter out the high-frequency harmonic components of the three-phase current, in order to obtain a frequency of ω. e and 2ω g -ω e The current component; a bandpass filter is configured to perform bandpass filtering on the current component to obtain a frequency of ω. e The fundamental current component; the current component and the fundamental current component are subjected to a first processing to obtain a low-frequency current harmonic component; the low-frequency current harmonic component and the fundamental current component are subjected to a second processing to obtain a processing result; a resonant controller is configured to perform closed-loop processing on the processing result to obtain a compensation frequency, wherein the compensation frequency is used to correct the modulated wave in the modulation stage to suppress beat frequency phenomenon.

Description

Technical Field

[0001] This invention belongs to the field of beat frequency suppression methods, and particularly relates to a beat frequency-free method based on current feedback frequency compensation. Background Technology

[0002] The high-speed train is powered by a single-phase overhead contact line, inevitably generating secondary pulsating power, resulting in a secondary pulsating voltage with a frequency of 2ωg (100Hz) on the DC bus. This secondary pulsating voltage couples with a modulated wave of frequency ωe, and after modulation by the three-phase inverter, generates a low-order beat frequency voltage component with a frequency of 2ωg - ωe at the output phase voltage. Because the motor is an inductive load, even a small-amplitude low-order beat frequency voltage can cause the motor to generate a large-amplitude harmonic current, thus producing torque pulsation and the beat frequency phenomenon.

[0003] Existing technology detects the DC bus voltage, calculates a compensation frequency related to the DC bus in an open-loop manner, and superimposes this compensation frequency onto the motor's fundamental frequency. This can suppress low-order beat frequency voltages caused by secondary pulsating voltages and eliminate motor torque pulsation. However, existing methods for feedforward frequency compensation based on open-loop detection of the DC bus voltage are affected by non-ideal factors such as PWM delay and control delay, resulting in limited compensation accuracy at low switching frequencies and an inability to effectively suppress beat frequency phenomena.

[0004] This invention proposes a beat-free algorithm based on current feedback frequency compensation to suppress beat frequency phenomena and reduce motor torque ripple and motor current harmonics. By detecting the three-phase current of the motor and then performing low-pass and band-pass filtering sequentially, a variable consistent with the DC bus voltage ripple frequency is obtained. This variable is then subjected to resonant control to obtain the frequency requiring compensation. This achieves closed-loop frequency compensation, avoiding the influence of non-ideal factors such as PWM delay and control delay, and ensuring the accuracy of the compensation frequency. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a beatless method based on current feedback frequency compensation.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a beat-frequency-free method based on current feedback frequency compensation, characterized in that it includes the following steps: configuring an AD sampling module (1) for sampling the three-phase current i of the motor in the main topology of the EMU traction converter. a i b i c Collect data;

[0007] Configure a low-pass filter (2) to filter out the high-frequency harmonic components of the three-phase current in order to obtain a frequency of ω. e and 2ω g-ω e current component i a-LPF i b-LPF i c-LPF ;

[0008] Configure a bandpass filter (3) to perform bandpass filtering on the current component to obtain a frequency of ω. e The fundamental current component i a-BPF i b-BPF i c-BPF ;

[0009] The current component and the fundamental current component are subjected to a first processing to obtain the low-frequency current harmonic component i. a-low i b-low i c-low ;

[0010] The low-frequency current harmonic component and the fundamental current component are subjected to a second processing to obtain the processing result.

[0011] Configure a resonant controller (4) to perform closed-loop processing on the processing result to obtain the compensation frequency f. beat Wherein, the compensation frequency f beat Used to correct the modulated wave during the modulation stage to suppress beat frequency phenomena.

[0012] Furthermore, the current component can be expressed as:

[0013]

[0014]

[0015]

[0016] In the above formula, A and B represent the fundamental amplitude and the lower harmonic amplitude, respectively, and are used to represent variables, ω. e For the modulation wave frequency, 2ω g This represents the pulsation frequency.

[0017] Furthermore, the fundamental current component can be expressed as:

[0018]

[0019]

[0020]

[0021] Further, the first process involves subtracting the current component from the fundamental current component to obtain a frequency of 2ω. g -ω eThe low-frequency current harmonic components, wherein the low-frequency current harmonic components can be expressed as:

[0022]

[0023]

[0024]

[0025] Further, the second processing involves multiplying the current component and the fundamental current component to obtain the processing result, which can be expressed as:

[0026]

[0027]

[0028]

[0029] Furthermore, the compensation frequency f beat To obtain it, follow these steps:

[0030] The processing results are summed to obtain the summation result:

[0031]

[0032] Based on the resonant controller (4), closed-loop control is performed on the summation result to output at the compensation frequency f. beat The closed-loop control mode of the resonant controller (4) can be expressed as follows:

[0033]

[0034] In the above formula, ω c For the resonant bandwidth, K R This is the resonant gain.

[0035] The beneficial technical effects of this invention are as follows:

[0036] (1) The compensation frequency obtained by the present invention reflects the influence of the secondary pulsating voltage of the DC bus on the motor current. Therefore, the motor current state is fed back in a closed loop and is not affected by the switching frequency. The algorithm has strong robustness.

[0037] (2) This invention will M sum Perform resonance control and output result f beat This is superimposed on the output frequency of the motor controller, thereby eliminating low-order beat frequency voltage. Attached Figure Description

[0038] The present invention includes the following figures:

[0039] The accompanying drawings are provided to better understand the invention and are not intended to unduly limit the scope of the invention. Wherein:

[0040] Figure 1 This invention applies to the main topology of the traction converter in a high-speed train.

[0041] Figure 2 This is a schematic diagram of the overall framework of the beat-free method for current feedback frequency compensation of the present invention.

[0042] In the diagram, 1-AD sampling module, 2-low-pass filter, 3-band-pass filter; 4-resonant controller. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the accompanying drawings. This detailed description is an illustration in conjunction with exemplary embodiments of the invention, including various details of the embodiments to aid understanding, and should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0044] Figure 1 This invention pertains to the main topology of the traction converter in a high-speed train. The input to the traction converter is powered by single-phase AC, therefore the DC bus voltage obtained after rectification by the four-quadrant converter exhibits significant secondary pulsation. dc =U dc +△U dc sin(2ω g t+θ 100 A three-phase inverter converts DC bus voltage into three-phase AC power to drive a motor. Due to the presence of secondary pulsating voltage, low-order harmonics appear in the inverter output voltage, causing torque pulsation in the motor. To overcome this defect, this invention provides a beat-free method based on current feedback frequency compensation, specifically including the following steps:

[0045] The three-phase current i of the motor was obtained through AD sampling module 1. a i b i c Then, the three-phase alternating current is passed through a low-pass filter 2 to remove high-frequency harmonic components, retaining the frequency ω. e and 2ω g -ω e current component i a-LPF i b-LPF i c-LPF ,in

[0046]

[0047]

[0048]

[0049] In the above formula, A and B represent the fundamental amplitude and the lower harmonic amplitude, respectively, and are used to represent variables, ω. e For the modulation wave frequency, 2ω g Let ω be the pulsation frequency, t be time, and ω be the angle. The initial phase corresponding to the current in each phase.

[0050] The low-pass filtered current component is then band-pass filtered through band-pass filter 3 to obtain a frequency of ω. e The fundamental current component i a-BPF i b-BPF i c-BPF ;in,

[0051]

[0052]

[0053]

[0054] Then, the current component after low-pass filtering is subtracted from the fundamental current component to extract the frequency 2ω. g -ω e low-frequency current harmonic components i a-low i b-low i c-low ;in,

[0055]

[0056]

[0057]

[0058] Multiplying the lower harmonic components of each phase with the fundamental current component yields the corresponding product M. a M b M c ;in,

[0059]

[0060]

[0061]

[0062] The product of each phase contains a frequency of 2ω. g and 2ωg -2ω e The alternating current component. Among them, the frequency is 2ω. g The component is a zero-sequence component with a frequency of 2ω. g -2ω e The component is a negative sequence component, and the three phases are in balance. Therefore, M... a M b M c Adding the three variables together gives M. sum .in,

[0063]

[0064] M sum The frequency is consistent with the DC bus voltage pulsation frequency, reflecting the influence of the bus voltage pulsation on the motor; finally, a resonant controller 4 is used to control the M... sum The output of closed-loop control is the compensation frequency f. beat By correcting the modulated wave with this compensation frequency during the modulation stage, the low-order beat frequency voltage caused by the secondary pulsating voltage of the bus can be offset, thus suppressing the beat frequency phenomenon. The closed-loop control mode of the resonant controller 4 can be expressed as follows:

[0065]

[0066] In the above formula, ω c For the resonant bandwidth, K R Let be the resonant gain; this formula represents the transfer function of the resonant controller.

[0067] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0068] Obviously, the above examples of the present invention are merely illustrative of the present invention and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A beat-free method based on current feedback frequency compensation, characterized in that, Includes the following steps: Configure the AD sampling module (1) to sample the three-phase current of the motor in the main topology of the traction converter of the EMU. i a , i b , i c Collect data; Configure a low-pass filter (2) to filter out the high-frequency harmonic components of the three-phase current to obtain a frequency of ω e and 2 ω g - ω e Current component i a-LPF , i b-LPF , i c-LPF ; Configure a bandpass filter (3) to perform bandpass filtering on the current component to obtain a frequency of ω e fundamental current component i a-BPF , i b-BPF , i c-BPF ; The current component and the fundamental current component are subjected to a first processing to obtain the low-frequency current harmonic component. i a-low , i b-low , i c-low ; The low-frequency current harmonic component and the fundamental current component are subjected to a second processing to obtain the processing result. Configure a resonant controller (4) to perform closed-loop processing on the processing result to obtain the compensation frequency. f beat The compensation frequency f beat Used to correct the modulated wave during the modulation stage to suppress beat frequency phenomenon; The current component can be expressed as: ； ； ； In the above formula, A and B These refer to the fundamental frequency amplitude and the amplitude of lower harmonics, respectively, and are used to represent variables. ω e For the modulation wave frequency, 2 ω g The pulsation frequency; These are the three-phase currents of the motor. i a , i b , i c The initial phase; The fundamental current component can be expressed as: ; ; ; The first process is to subtract the current component from the fundamental current component to obtain a frequency of 2. ω g - ω e The low-frequency current harmonic components, wherein the low-frequency current harmonic components can be expressed as: ； ； ； The second processing step is to multiply the current component and the fundamental current component to obtain the processing result, which can be expressed as: ; ; 。 2. The beat-frequency-free method based on current feedback frequency compensation according to claim 1, characterized in that, The compensation frequency f beat To obtain it, follow these steps: The processing results are summed to obtain the summation result: ； The summation result is closed-loop controlled based on the resonant controller (4) to output the compensation frequency. f beat The closed-loop control mode of the resonant controller (4) can be expressed as follows: ； In the above formula, ω c For resonant bandwidth, K R This is the resonant gain.

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