Capacitor voltage feedback active damping method for suppressing resonant frequency shift of current source rectifier
Patent Information
- Application Number
- CN202611186453.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-06
- Publication Date
- 2026-09-25
AI Technical Summary
[0004]发明目的：针对电流源型整流器交流侧LC滤波器在数字控制延时条件下容易产生谐振峰，以及传统电容电压反馈有源阻尼方法存在虚拟电抗分量、导致实际谐振频率偏离LC滤波器固有谐振频率的问题，本发明提供一种抑制电流源型整流器谐振频率偏移的电容电压反馈有源阻尼方法，使电流源型整流器具有较好的谐振抑制能力和稳定运行性能
[0038]有益效果：本发明提供的抑制电流源型整流器谐振频率偏移的电容电压反馈有源阻尼方法，相对于现有技术，具有如下优势：1、本发明采用电容电压反馈有源阻尼方法，无需在滤波器支路中增加额外阻尼电阻，避免了无源阻尼带来的附加功率损耗；2、本发明采用SOGI型滤波器替代传统高通滤波器，并通过相位补偿抵消数字控制延时引起的相位滞后，使有源阻尼通道在谐振频率处接近纯阻性，从而减小虚拟电抗分量；3、本发明能够在有效抑制LC滤波器谐振峰的同时，减小实际谐振频率相对于固有谐振频率的偏移，提高电流源型整流器的稳定性和控制可靠性。
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Abstract
Description
Technical Field
[0001] This invention relates to a capacitor voltage feedback active damping method for suppressing the resonant frequency shift of a current source rectifier, belonging to the field of power electronic control technology. Background Technology
[0002] With the development of new energy power generation, energy storage systems, and high-performance power electronic interface equipment, current source rectifiers are widely used in medium- and high-power power conversion applications due to their advantages such as high input power factor, continuous DC current, and strong short-circuit protection. To suppress high-frequency harmonics generated by switching modulation, LC filters are typically installed on the AC side of current source rectifiers. However, LC filters are prone to generating resonance peaks near their inherent resonant frequency, affecting grid-side current quality and system stability. Traditional passive damping methods require the addition of damping resistors, resulting in additional power losses.
[0003] While active damping with capacitor voltage feedback can suppress resonance by constructing a virtual impedance, the damping branch generates virtual reactance due to sampling calculation delay and PWM modulation delay, causing the actual resonant frequency to deviate from the inherent resonant frequency. Traditional high-pass filters are unable to compensate for this phase lag. Therefore, it is necessary to propose an active damping method that can suppress the resonance peak and reduce the resonant frequency shift. Summary of the Invention
[0004] Purpose of the invention: To address the problems of resonance peaks easily generated in the AC side LC filter of current source rectifiers under digital control delay conditions, and the virtual reactance component in traditional capacitor voltage feedback active damping methods that cause the actual resonant frequency to deviate from the inherent resonant frequency of the LC filter, this invention provides a capacitor voltage feedback active damping method to suppress the resonant frequency deviation of current source rectifiers, thereby enabling current source rectifiers to have better resonance suppression capability and stable operation performance.
[0005] Technical solution: To achieve the above objectives, the technical solution adopted by this invention is as follows.
[0006] A capacitor voltage feedback active damping method for suppressing the resonant frequency shift of a current source rectifier includes:
[0007] Step 1: Establish a three-phase current source PWM rectifier model with LC filter, calculate the sampling delay and PWM modulation delay, and obtain a digital control system model with digital control delay.
[0008] Step 2: Select the input filter capacitor voltage as the active damping feedback quantity, construct an active damping branch based on capacitor voltage feedback, and analyze the virtual impedance characteristics under digital control delay.
[0009] Step 3: Determine the mechanism of the resonant frequency shift of the LC filter based on the equivalent virtual reactance component in the virtual impedance characteristics;
[0010] Step 4: Replace the traditional high-pass filter with an SOGI type damping filter, and determine the center angular frequency and phase compensation angle of the SOGI type damping filter according to the inherent resonant frequency of the LC filter and the digital control delay, so that the equivalent virtual reactance component is zero at the resonant frequency, thereby making the virtual impedance tend to be purely resistive near the resonant frequency.
[0011] Step 5: Superimpose the output of the active damping branch onto the rectifier modulation control channel, and determine the active damping coefficient through discrete domain stability analysis to ensure that the poles of the closed-loop system are located in the stable region, thereby achieving resonant frequency offset suppression and stable control.
[0012] Specifically, step 1 includes the following sub-steps:
[0013] Step 1.1: Establish the main circuit model of a three-phase current source PWM rectifier with LC filter;
[0014] Step 1.2: Based on the AC side filter inductance of the rectifier and filter capacitor The inherent resonant angular frequency of the LC filter is determined to be... ;
[0015] Step 1.3: Establish the AC side current of the rectifier. Current to grid side The transfer function, and the AC side current of the rectifier. to input filter capacitor voltage The transfer function;
[0016] Step 1.4: Consider the sampling calculation delay and PWM modulation delay, and establish a digital control delay model.
[0017] Specifically, step 2 includes the following sub-steps:
[0018] Step 2.1: Select the input filter capacitor voltage As an active damping feedback quantity, through the active damping coefficient After being combined with the damping filter, it forms an active damping branch;
[0019] Step 2.2: Calculate the equivalent virtual impedance and equivalent damping current of the active damping branch;
[0020] Step 2.3: In a traditional active damping branch, a high-pass filter is used in the damping filter. ;
[0021] Step 2.4, and Substituting into the equivalent virtual impedance expression, we obtain the virtual impedance in the frequency domain as follows: ;
[0022] Step 2.5: Set the virtual impedance Decomposed into equivalent virtual resistance components and equivalent virtual reactance component .
[0023] Specifically, step 3 includes the following sub-steps:
[0024] Step 3.1: Based on the equivalent virtual reactance component This is equivalent to being connected in parallel to the filter capacitor. Virtual reactor branches at both ends;
[0025] Step 3.2: Add the filter capacitor Connected in parallel with the virtual reactance branch, the equivalent filter capacitor is obtained. ;
[0026] Step 3.3: Based on the equivalent filter capacitance Determine the actual resonant angular frequency ;
[0027] Step 3.4: Determine the LC filter resonant frequency offset mechanism based on the above relationships: digital control delay. This causes the active damping branch to no longer be equivalent to a pure virtual resistance, but instead generates an equivalent virtual reactance component. The equivalent virtual reactance component Change the filter capacitor Equivalent filter capacitor This changes the actual resonant angular frequency of the LC filter. Therefore, the goal of suppressing the resonant frequency shift is to make Satisfying Thus This allows for the suppression of the resonant frequency shift in a three-phase current source PWM rectifier.
[0028] Specifically, step 4 includes the following sub-steps:
[0029] Step 4.1: Replace the high-pass filter used in the traditional damping filter with an SOGI type damping filter;
[0030] Step 4.2: Set the center angular frequency of the SOGI type damped filter. Equal to the natural resonant angular frequency of the LC filter ;
[0031] Step 4.3, Consider digital control delay The SOGI type damping filter was obtained in At this time, the total phase of the active damping branch ;
[0032] Step 4.4: Set the phase compensation angle satisfy This is to achieve zero total phase of the active damping channel at the resonant frequency, thereby suppressing the resonant frequency shift of the current source rectifier.
[0033] For the body, step 5 includes the following sub-steps:
[0034] Step 5.1: Discretize the SOGI-type damped filter obtained in Step 4 using the Tustin transform;
[0035] Step 5.2, regarding the current transfer function Input filter capacitor voltage transfer function Digital control delay Discretize the data;
[0036] Step 5.3: Based on the discretization results, establish the system's discrete domain open-loop transfer function;
[0037] Step 5.4: Use the Routh stability criterion to analyze and determine the active damping coefficient that makes the open-loop system stable. The range of values for the active damping coefficient, i.e., the stable region, is illustrated using root locus plots. The influence of changes on the stability of the closed-loop system is investigated. The optimal active damping coefficient is selected within the stable region to achieve LC resonant peak suppression, reduction of resonant frequency offset, and stable control of the current source rectifier.
[0038] Beneficial Effects: The capacitor voltage feedback active damping method for suppressing the resonant frequency shift of a current source rectifier provided by this invention has the following advantages compared with the prior art: 1. This invention uses a capacitor voltage feedback active damping method, eliminating the need to add an extra damping resistor in the filter branch, thus avoiding the additional power loss caused by passive damping; 2. This invention uses an SOGI-type filter to replace the traditional high-pass filter, and compensates for the phase lag caused by digital control delay through phase compensation, making the active damping channel close to pure resistivity at the resonant frequency, thereby reducing the virtual reactance component; 3. This invention can effectively suppress the resonant peak of the LC filter while reducing the shift of the actual resonant frequency relative to the inherent resonant frequency, improving the stability and control reliability of the current source rectifier. Attached Figure Description
[0039] Figure 1 This is a diagram of the three-phase CSR topology of the present invention.
[0040] Figure 2 This invention employs a proportional capacitor voltage feedforward active damping current source rectifier system. Domain model.
[0041] Figure 3 This is an equivalent block diagram of the current source rectifier using proportional capacitor voltage feedforward active damping in this invention.
[0042] Figure 4 This is the active damping equivalent circuit model in this invention.
[0043] Figure 5 This is an equivalent block diagram of the current source rectifier using an SOGI-type filter in this invention.
[0044] Figure 6 This is the Bode plot of the transfer function of the LC filter in this invention.
[0045] Figure 7 The source damping coefficient of the closed-loop system poles in this invention The changing root locus diagram.
[0046] Figure 8 This is the system Bode plot of the SOGI type filter in this invention.
[0047] Figure 9 This is a schematic diagram of the simulation results of output voltage, grid voltage, and grid current in the embodiment.
[0048] Figure 10 The image shows the steady-state waveform of the grid-side current when an SOGI-type filter with active damping control is used in the embodiment.
[0049] Figure 11 The figure shows the FFT analysis results of the grid-side current of the SOGI type filter used in the embodiment.
[0050] Figure 12 The image shows the steady-state waveform of the grid-side current when a high-pass filter with active damping control is used in the embodiment.
[0051] Figure 13 The figure shows the FFT analysis results of the high-pass filter network-side current used in the embodiment. Detailed Implementation
[0052] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0053] A capacitor voltage feedback active damping method for suppressing the resonant frequency shift of a current source rectifier is applied to a CSR system, and its main circuit is as follows: Figure 1 As shown, the system's inner current control block diagram is as follows: Figure 5 As shown.
[0054] like Figure 1 As shown, the system includes an AC power supply. AC side filter inductor and filter capacitor CSR power conversion unit, output-side filter inductor and filter capacitor DC load The digital control section of the system includes a current controller, an active damping branch based on capacitor voltage feedback, an SOGI-type damping filter, a phase compensation stage, a digital delay stage, and a PWM modulation module. The modulation control signal output from the current controller and the output signal from the active damping branch work together to generate a three-phase bridge arm switching signal, thus achieving stable control of the current source rectifier.
[0055] like Figures 1-8 As shown, the indirect current control method for a current source rectifier in this invention is as follows.
[0056] Step 1: Establish a three-phase current source PWM rectifier model with LC filter, and consider the sampling calculation delay and PWM modulation delay to obtain a digital control system model with digital control delay.
[0057] Step 2: Select the input filter capacitor voltage as the active damping feedback quantity, construct an active damping branch based on capacitor voltage feedback, and analyze the virtual impedance characteristics of the active damping branch under digital delay to obtain the equivalent virtual resistance component and the equivalent virtual reactance component.
[0058] Step 3: Based on the equivalent virtual reactance component in the virtual impedance characteristics, analyze its influence on the equivalent parameters of the input filter capacitor, and determine the mechanism by which the actual resonant frequency of the LC filter shifts relative to its inherent resonant frequency.
[0059] Step 4: Replace the traditional high-pass filter with an SOGI-type damping filter, and determine the center angular frequency and phase compensation angle of the SOGI-type damping filter based on the inherent resonant frequency of the LC filter and the digital control delay, so that the equivalent virtual reactance component is zero at the resonant frequency, thereby making the virtual impedance tend to be purely resistive near the resonant frequency.
[0060] Step 5: Superimpose the output of the active damping branch onto the rectifier modulation control channel, and determine the active damping parameters through discrete domain stability analysis to ensure that the poles of the closed-loop system are located in the stable region, thereby achieving LC resonance peak suppression, reduction of resonance frequency offset, and stable control of the current source rectifier.
[0061] Step 1, establishing a three-phase current source PWM rectifier model with LC filter, and considering sampling calculation delay and PWM modulation delay, specifically includes the following steps.
[0062] Step 1.1: Establish the main circuit model of a three-phase current source PWM rectifier with an LC filter, where... This is the grid voltage. For grid-side current, This is the AC side current of the rectifier. ; , These are the AC side filter inductor and filter capacitor of the rectifier, respectively.
[0063] Step 1.2: Based on the AC side filter inductance of the rectifier and filter capacitor Determine the inherent resonant angular frequency of the LC filter. :
[0064]
[0065] in: This is the inherent resonant frequency of the LC filter.
[0066] Step 1.3: Establish the AC side current of the rectifier. Current to grid side The transfer function, and the AC side current of the rectifier. to input filter capacitor voltage The transfer functions are as follows:
[0067]
[0068]
[0069] in: Let be the current transfer function. The input filter capacitor voltage transfer function. For the Laplace operator.
[0070] Step 1.4: Express the sampling delay transfer function for one sampling period as follows:
[0071]
[0072] The PWM modulation delay transfer function is expressed as:
[0073]
[0074] Based on the above sampling delay and PWM modulation delay, the total digital control delay of the system is obtained as follows:
[0075]
[0076] in: The sampling period is For the Laplace operator.
[0077] Step 2 involves selecting the input filter capacitor voltage as the feedback quantity, constructing an active damping branch, and analyzing the virtual impedance characteristics under digital control delay. Specifically, it includes the following steps.
[0078] Step 2.1: Select the input filter capacitor voltage As an active damping feedback quantity, through the active damping coefficient and damping filter This forms a damping feedback branch, whose equivalent damping current is expressed as:
[0079]
[0080] Step 2.2: Based on the active damping branch, its equivalent virtual impedance is obtained as follows:
[0081]
[0082] in, This is the equivalent virtual impedance of the active damping branch across the filter capacitor.
[0083] Step 2.3: In a traditional active damping branch, a high-pass filter is used as the damping filter, and its transfer function is:
[0084]
[0085] in: This is the cutoff angular frequency of the high-pass filter.
[0086] Step 2.4, and Substitution The virtual impedance in the frequency domain is obtained as follows:
[0087]
[0088] make Then the virtual impedance in the frequency domain is:
[0089]
[0090] in: ω is the sampling period, and ω is the angular frequency.
[0091] Step 2.5: Set the virtual impedance Decomposed into equivalent virtual resistance components and equivalent virtual reactance component ,Right now:
[0092]
[0093] in:
[0094]
[0095]
[0096] Step 3, based on the equivalent virtual reactance component The mechanism of LC filter resonant frequency shift is determined by the following steps.
[0097] Step 3.1: Based on the equivalent virtual reactance component obtained in Step 2 This is equivalent to being connected in parallel to the filter capacitor. The virtual reactance branches at both ends, where the input filter capacitor impedance is:
[0098]
[0099] The impedance of the virtual reactance branch is:
[0100]
[0101] Step 3.2: Add the filter capacitor Connected in parallel with the virtual reactance branch, the equivalent filter capacitor is obtained:
[0102]
[0103] in: The equivalent filter capacitor is considered after taking into account the virtual reactance branch.
[0104] Step 3.3: Based on the equivalent filter capacitance Determine the actual resonant angular frequency:
[0105]
[0106] The inherent resonant angular frequency of the LC filter is:
[0107]
[0108] Step 3.4: Determine the LC filter resonant frequency offset mechanism based on the above relationships: digital control delay. This causes the active damping branch to no longer be equivalent to a pure virtual resistance, but instead generates an equivalent virtual reactance component. The equivalent virtual reactance component Change the filter capacitor Equivalent filter capacitor This changes the actual resonant angular frequency of the LC filter. Therefore, the goal of suppressing the resonant frequency shift is to make The following conditions must be met:
[0109]
[0110] Thus:
[0111]
[0112] This enables the suppression of the resonant frequency shift of a three-phase current source PWM rectifier.
[0113] Step 4 involves replacing the traditional high-pass filter with an SOGI-type filter, and determining its center angular frequency and phase compensation angle based on the inherent resonant frequency of the LC and the digital control delay, so that the virtual impedance tends to be purely resistive near the resonant frequency. Specifically, this includes the following steps.
[0114] Step 4.1: Replace the traditional high-pass filter with an SOGI-type damped filter. The SOGI-type damped filter is represented as follows:
[0115]
[0116] in: This is the inherent resonant angular frequency of the LC filter. Here is the damping coefficient of the SOGI type damped filter. For phase compensation angle, This is the center angular frequency of the SOGI type damped filter.
[0117] Step 4.2: Set the center angular frequency of the SOGI type damped filter to equal the natural resonant frequency of the LC filter, that is:
[0118]
[0119] And order:
[0120]
[0121] SOGI type damping filter in At that time, there were:
[0122]
[0123] Simplifying, we get:
[0124]
[0125] Therefore, it can be seen that the SOGI type damping filter in Provide phase advance .
[0126] Step 4.3, Considering the digital control delay:
[0127]
[0128] Digital control delay exist At this point, the phase lag is:
[0129]
[0130] in:
[0131]
[0132] Therefore, SOGI type damping filters in At this point, the total phase of the active damping branch is:
[0133]
[0134] Step 4.4: Ensure the phase compensation angle satisfies:
[0135]
[0136] but:
[0137]
[0138] When the total phase of the active damping branch at the resonant frequency is zero, the active damping branch is equivalent to a pure resistive branch at the resonant frequency, and its equivalent virtual reactance component is zero. This reduces the impact of the parallel virtual reactance on the input filter capacitor.
[0139]
[0140] This ensures that the actual resonant angular frequency satisfies:
[0141]
[0142] This achieves the suppression of the resonant frequency shift of the current source rectifier.
[0143] Step 5 involves superimposing the output of the active damping branch onto the rectifier modulation control channel and determining the active damping parameters to achieve resonant frequency offset suppression and stable control. Specifically, this includes the following steps.
[0144] Step 5.1: Discretize the SOGI-type damped filter obtained in Step 4 using the Tustin transform:
[0145]
[0146] The SOGI-type damped filter in the discrete domain is obtained:
[0147]
[0148] in, The sampling period is It is a discrete-domain operator.
[0149] Step 5.2: Transform the current transfer function using the ZOH transformation. Transform into discrete form The input filter capacitor voltage transfer function is obtained through the ZOH transformation. Transform into discrete form Delay for digital control Discretization process is performed to obtain .
[0150] Step 5.3: Based on the discretized components, establish the open-loop transfer function of the system in the discrete domain:
[0151]
[0152] in: Here is the transfer function of the current controller. This represents the equivalent gain of the PWM stage in the rectifier.
[0153] Step 5.4: To determine the boundary of the system's stable region, ... The denominator factor is written as:
[0154]
[0155] in: , , , , , The denominator factor of the open-loop transfer function is Polynomial coefficients in a domain expression; For discrete complex variables.
[0156] Step 5.5, by... Substitute factors into the denominator ,get:
[0157]
[0158] in: , , , , , The denominator factor of the open-loop transfer function is Polynomial coefficients in a domain expression; An auxiliary complex variable is introduced after the bilinear transformation to convert the stability problem of the discrete system into a continuous domain form that can be analyzed using the Routh stability criterion.
[0159] based on The Routh stability criterion is used for analysis to determine the active damping coefficient that ensures the stability of the open-loop system. The range of values for , also known as the stable region.
[0160] Step 5.6: Use root locus diagrams to illustrate the active damping coefficient. The influence of changes on the stability of the closed-loop system is investigated. The optimal active damping coefficient is selected within the stable region to achieve LC resonant peak suppression, reduction of resonant frequency offset, and stable control of the current source rectifier.
[0161] Furthermore, to verify the superiority of the method of the present invention, an embodiment of simulation analysis in MATLAB / Simulink is given, and the system parameters of the current source rectifier in this embodiment are shown in Table 1.
[0162] Table 1 System Parameters
[0163]
[0164] Furthermore, to verify the effectiveness of the capacitor voltage feedback active damping method for suppressing the resonant frequency shift of the current source rectifier proposed in this invention, a simulation analysis was performed on the system. The simulation results are as follows: Figures 9 to 13 As shown.
[0165] Figure 9 This is a schematic diagram showing the simulation results of the system output voltage, grid-side voltage, and grid-side current. Figure 9 It can be seen that the system output voltage It can be stably maintained near a given value; grid-side current With grid-side voltage Maintaining a good phase relationship indicates that the system can achieve stable AC-to-DC energy conversion and has good input current tracking performance.
[0166] Figure 10 This is a steady-state waveform of the three-phase current on the grid side when using an SOGI-type filter with active damping control. Figure 10 It can be seen that the current on the three-phase grid side , , The waveform remains largely symmetrical and relatively smooth, with no obvious resonance oscillations or distortions, indicating that the proposed SOGI-type capacitor voltage feedback active damping method can effectively suppress resonance caused by the LC filter.
[0167] Figure 11 This presents the FFT analysis results of the grid-side current when using an SOGI-type filter with active damping control. Figure 11 It can be seen that the fundamental frequency of the grid-side current is 50Hz, the fundamental amplitude is approximately 5.393A, and the total harmonic distortion (THD) is 1.67%. This result indicates that, using the method of this invention, the harmonic content of the grid-side current is lower, and the current waveform quality is higher.
[0168] Figure 12 This is a steady-state waveform of the three-phase grid-side current when using active damping control with a conventional filter. Figure 10 compared to, Figure 12 The three-phase current still exhibits certain waveform distortion and high-frequency ripple, indicating that although ordinary filters can play a certain active damping role, their ability to compensate for phase characteristics near the resonant frequency is insufficient, making it difficult to fully reduce the influence of virtual reactance caused by digital delay.
[0169] Figure 13 This presents the FFT analysis results of the grid-side current when using active damping control with a conventional filter. Figure 13 It can be seen that the fundamental frequency of the grid-side current is 50 Hz, the fundamental amplitude is about 5.398 A, and the total harmonic distortion (THD) of the current is 2.90%.
[0170] In summary, by adopting the SOGI-type capacitor voltage feedback active damping method proposed in this invention, the system output voltage is stable, the three-phase grid-side current is symmetrical and the waveform is smoother, and the total harmonic distortion of the current is significantly reduced. Compared with the active damping method of ordinary filters, this invention can more effectively compensate for the phase lag caused by digital control delay, making the active damping channel close to pure resistivity near the resonant frequency. This reduces the influence of virtual reactance components on the equivalent parameters of the LC filter, achieves resonance peak suppression and reduces resonant frequency offset, and improves the stability of the current source rectifier and the grid-side current quality.
[0171] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.
Claims
1. A capacitor voltage feedback active damping method for suppressing the resonant frequency shift of a current source rectifier, characterized in that: Includes the following steps: Step 1: Establish a three-phase current source PWM rectifier model with LC filter, calculate the sampling delay and PWM modulation delay, and obtain a digital control system model with digital control delay. Step 2: Select the input filter capacitor voltage as the active damping feedback quantity, construct an active damping branch based on capacitor voltage feedback, and analyze the virtual impedance characteristics under digital control delay. Step 3: Determine the mechanism of the resonant frequency shift of the LC filter based on the equivalent virtual reactance component in the virtual impedance characteristics; Step 4: Replace the traditional high-pass filter with an SOGI type damping filter, and determine the center angular frequency and phase compensation angle of the SOGI type damping filter according to the inherent resonant frequency of the LC filter and the digital control delay, so that the equivalent virtual reactance component is zero at the resonant frequency, thereby making the virtual impedance tend to be purely resistive near the resonant frequency. Step 5: Superimpose the output of the active damping branch onto the rectifier modulation control channel, and determine the active damping coefficient through discrete domain stability analysis to ensure that the poles of the closed-loop system are located in the stable region, thereby achieving resonant frequency offset suppression and stable control.
2. The capacitor voltage feedback active damping method for suppressing the resonant frequency shift of a current source rectifier according to claim 1, characterized in that: Step 1 includes the following sub-steps: Step 1.1: Establish the main circuit model of a three-phase current source PWM rectifier with an LC filter; denot the grid voltage as... The grid-side current is denoted as The AC side current of the rectifier is denoted as The AC side filter inductor and filter capacitor of the rectifier are respectively denoted as... and , ; Step 1.2: Based on the AC side filter inductance of the rectifier and filter capacitor The inherent resonant angular frequency of the LC filter is determined to be... ;in, This is the inherent resonant frequency of the LC filter; Step 1.3: Establish the AC side current of the rectifier. Current to grid side The transfer function, and the AC side current of the rectifier. to input filter capacitor voltage The transfer functions are as follows: ， ， Step 1.4: Express the sampling delay transfer function for one sampling period as follows: ， Step 1.5: Combine with PWM modulation delay transfer function And sampling calculation delay transfer function The digital control delay transfer function is expressed as: ， in: Let be the current transfer function. The input filter capacitor voltage transfer function. To calculate the delay transfer function for sampling, PWM modulation delay transfer function For digital control delay transfer function, The sampling period is For the Laplace operator.
3. The capacitor voltage feedback active damping method for suppressing the resonant frequency shift of a current source rectifier according to claim 1, characterized in that: Step 2 includes the following sub-steps: Step 2.1: Select the input filter capacitor voltage As an active damping feedback quantity, through the active damping coefficient After being combined with the damping filter, an active damping branch is formed. The equivalent damping current can be expressed as: ， in: The equivalent damping current generated by the active damping branch. Let be the transfer function of the damped filter; Step 2.2: Based on the active damping branch, calculate the equivalent virtual impedance as follows: ， in: This is the equivalent virtual impedance of the active damping branch across the filter capacitor. Step 2.3: In a traditional active damping branch, a high-pass filter is used as the damping filter, and its transfer function is: ， in: Let be the transfer function of the high-pass filter. This is the cutoff angular frequency of the high-pass filter; Step 2.4, and Substitution The virtual impedance in the frequency domain is obtained as ;make Then the virtual impedance in the frequency domain is Where ω is the angular frequency; Step 2.5: Set the virtual impedance It can be decomposed into an equivalent virtual resistance component and an equivalent virtual reactance component, namely: ， ， ， in: For the equivalent virtual resistance component, This is the equivalent virtual reactance component.
4. The active damping method with capacitor voltage feedback for suppressing the resonant frequency shift of a current source rectifier according to claim 1, characterized in that: Step 3 includes the following sub-steps: Step 3.1: Based on the equivalent virtual reactance component This is equivalent to being connected in parallel to the filter capacitor. The virtual reactance branches at both ends, then the input filter capacitor impedance for: ， Virtual reactance branch impedance for: ， Step 3.2: Add the filter capacitor Connected in parallel with the virtual reactance branch, the equivalent filter capacitor is obtained: ， in: The equivalent filter capacitor is taken into account after considering the virtual reactance branch; Step 3.3: Based on the equivalent filter capacitance Determine the actual resonant angular frequency for: ， The inherent resonant angular frequency of the LC filter for: ， Step 3.4: Determine the LC filter resonant frequency offset mechanism based on the above relationships: digital control delay. This causes the active damping branch to no longer be equivalent to a pure virtual resistance, but instead generates an equivalent virtual reactance component. The equivalent virtual reactance component Change the filter capacitor Equivalent filter capacitor This changes the actual resonant angular frequency of the LC filter. Therefore, the goal of suppressing the resonant frequency shift is to make Satisfying Thus This allows for the suppression of the resonant frequency shift in a three-phase current source PWM rectifier.
5. The active damping method with capacitor voltage feedback for suppressing resonant frequency shift in a current source rectifier according to claim 1, characterized in that: Step 4 includes the following sub-steps: Step 4.1: Replace the traditional high-pass filter with an SOGI-type damped filter. The transfer function of the SOGI-type damped filter is expressed as: ， in: Here is the damping coefficient of the SOGI type damped filter. For phase compensation angle, This is the center angular frequency of the SOGI type damped filter; Step 4.2, set the center angular frequency Equal to the natural resonant angular frequency of the LC filter and order Then the SOGI type damped filter in At that time, there were: ， Simplifying, we get: ， Therefore, it can be seen that the SOGI type damping filter in The phase at the point is ahead of ; Step 4.3, Consider digital control delay Digital control delay exist The phase lag introduced at this point is: ， in: ， Therefore, SOGI type damping filters in At this point, the total phase of the active damping branch is: ， Step 4.4: Set the phase compensation angle satisfy: ， but: ， When the total phase of the active damping branch at the resonant frequency is zero, the active damping branch is equivalent to a purely resistive branch at the resonant frequency, and its equivalent virtual reactance component is zero. Therefore: ， This leads to the actual resonant angular frequency satisfy: ， This achieves the suppression of the resonant frequency shift of the current source rectifier.
6. The capacitor voltage feedback active damping method for suppressing the resonant frequency shift of a current source rectifier according to claim 1, characterized in that: Step 5 includes the following sub-steps: Step 5.1: Apply the Tustin transform. The SOGI-type damped filter obtained in step 4 is discretized to obtain the SOGI-type damped filter in the discrete domain. ; Step 5.2: Transform the current transfer function using the ZOH transformation. Transform into discrete form The input filter capacitor voltage transfer function is obtained through the ZOH transformation. Transform into discrete form Delay for digital control Discretization process is performed to obtain ; Step 5.3: Based on the discretization results, establish the open-loop transfer function of the system. : ， in: Here is the transfer function of the current controller. This represents the equivalent gain of the PWM stage in the rectifier. Step 5.4: To find the boundary of the stable region, the open-loop transfer function is... Denominator factor Written as: ， in: , , , , , The denominator factor of the open-loop transfer function is Polynomial coefficients in a domain expression; For discrete-domain complex variables; Step 5.5, Substitute factors into the denominator ,get: ， in: , , , , , The denominator factor of the open-loop transfer function is Polynomial coefficients in a domain expression; An auxiliary complex variable is introduced after the bilinear transformation to transform the stability problem of the discrete system into a continuous domain form that can be analyzed using the Routh stability criterion. based on The Routh stability criterion is used for analysis to determine the active damping coefficient that ensures the stability of the open-loop system. The range of values for , i.e., the stable region; Step 5.6: Use root locus diagrams to illustrate the active damping coefficient. The influence of changes on the stability of the closed-loop system is investigated. The optimal active damping coefficient is selected within the stable region to achieve LC resonant peak suppression, reduction of resonant frequency offset, and stable control of the current source rectifier.