Method for reducing harmonic distortion of input current of Vienna rectifier of charging module of electric vehicle

Abstract

The invention provides a method for reducing input current harmonic distortion of a Vienna rectifier of an electric vehicle charging module. Belongs to the technical field of power electronic switching, and comprises the following steps: comparing an actual DC voltage with a reference DC voltage, calculating an error signal, and processing the calculated error signal through a voltage regulator to generate a reference voltage; and generating a three-phase current reference signal according to the phase and the amplitude of the power grid voltage. Through the technical scheme of the invention, the low-order current harmonic of the source side current can be selectively eliminated without depending on current / voltage conversion, a phase-locked loop or a space vector modulation module, so that the calculation requirement is remarkably reduced; due to the fact that the calculation requirement is obviously reduced, the transient response speed of the method is higher.

Description

Technical Field

[0001] The invention proposes a method for reducing the harmonic distortion of input current of a Vienna rectifier of an electric vehicle charging module, and belongs to the technical field of power electronic switching. Background Art

[0002] Rectifiers are often used as the first-end equipment for grid-connected operation. Their nonlinear properties can cause many problems to the grid, such as increased reactive power loss and grid current harmonic pollution. Grid voltage disturbances can directly affect the output voltage of Vienna rectifiers, resulting in reduced system efficiency and reliability.

[0003] In a 1500V high-voltage charging system, input voltage stability is critical to the normal operation of the subsequent LLC converter, especially when the input voltage comes from the previous Vienna rectifier. Since the LLC converter relies on a stable input voltage to provide efficient and stable power conversion, grid voltage fluctuations or other power instability factors will have a profound impact on the performance and stability of the charging module. Summary of the invention

[0004] The present invention provides a method for reducing the harmonic distortion of the input current of the Vienna rectifier of the electric vehicle charging module, so as to solve the problems mentioned in the above background technology:

[0005] The present invention proposes a method for reducing harmonic distortion of input current of a Vienna rectifier of an electric vehicle charging module, the method comprising:

[0006] S1, comparing the actual DC voltage with the reference DC voltage, calculating an error signal, and processing the calculated error signal through a voltage regulator to generate a reference voltage;

[0007] S2, generating a three-phase current reference signal according to the phase and amplitude of the grid voltage;

[0008] S3, compare the actual current with the reference current to generate a current error signal, process the generated error signal through the improved proportional resonant controller, and output a modulation signal , used to control the switch;

[0009] S4. Compare the voltage difference between the upper and lower bridge arms, calculate the neutral point voltage imbalance value, and use the PI controller to adjust the imbalance value to generate a neutral point balance control signal ;

[0010] S5. and The control signals Sabc are superimposed to generate the final control signal Sabc; and the optimized switching signal is output through the sinusoidal pulse width modulation method; the switching devices of the Vienna rectifier are controlled through the control signal Sabc to adjust the current on the grid side.

[0011] The present invention proposes a method for reducing harmonic distortion of input current of a Vienna rectifier of an electric vehicle charging module, the method further comprising:

[0012] Constructing a three-level collaborative control architecture, wherein the three-level collaborative control architecture includes an improved proportional resonant current control loop, an outermost voltage tracking control loop, and an innermost voltage balancing control loop;

[0013] In the improved proportional resonant current control loop, a combined structure of a fundamental wave tracking module and a multi-resonant peak parallel compensator is adopted to directly control the three-phase current in the abc coordinate system;

[0014]

[0015] in, Used to track the fundamental current component, It is used to filter out the 3rd, 5th and 7th low-order harmonics, where n is the harmonic order. , , are proportional gain, resonant gain and damping coefficient respectively; Represents the second-order dynamic characteristics; Represents the resonant frequency; among them, the fundamental wave tracking ; Harmonic tracking ;

[0016] In the outermost voltage tracking control loop, the DC side output voltage error is converted into a normalized reference current signal through a PI controller; specifically including:

[0017] Generate synchronous angular frequency based on the first phase voltage , generate symmetrical three-phase reference current signals through coordinate transformation , , ;

[0018] In the innermost voltage balance control loop, the positive and negative bus voltage difference is derived according to Kirchhoff's current law With zero sequence component The relationship is:

[0019]

[0020] and will Add to modulating signal , , , to adjust the neutral point current , to dynamically balance the positive and negative bus voltages;

[0021] Generate the final modulated signal , driving the Vienna rectifier switching device through sinusoidal pulse width modulation; Represents the basic modulation signal.

[0022] Beneficial effects of the present invention:

[0023] (1) The technical solution of the present invention can selectively eliminate low-order current harmonics of the source side current without relying on current / voltage conversion, phase-locked loop (PLL) or space vector modulation (SVM) modules, thereby significantly reducing the computational requirements; due to the significant reduction in computational requirements, the transient response speed of the proposed method is faster.

[0024] (2) In addition, the technical solution helps to remove selected low-order harmonics in the input current. Therefore, in the case where the grid voltage contains harmonic pollution, the technical solution can effectively reduce the total harmonic distortion (THD) of the input current.

[0025] (3) In addition, voltage balancing is achieved by using a simple PI controller to generate a voltage balancing sequence and adding it to the modulation signal. This technical solution not only effectively reduces the THD of the source side current, but also balances the voltage at the output end. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a principle block diagram of the Vienna rectifier of the present invention;

[0027] Figure 2 is a complete control diagram of the Vienna rectifier using PR control of the present invention;

[0028] Figure 3 is a block diagram of an improved PR controller of the present invention;

[0029] Figure 4 It is a principle block diagram of a current reference signal generator when the grid voltage is asymmetric according to the present invention;

[0030] Figure 5 is a control flow chart of the present invention;

[0031] Figure 6 This is the control effect diagram when the three-phase input voltage is unbalanced;

[0032] Figure 7 This is a control effect diagram when the three-phase input voltage is interfered by harmonics. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0034] Figure 1 FIG. 1 is a schematic block diagram of a preferred embodiment of the Vienna rectifier of the present invention. Figure 1 As shown, the Vienna rectifier of the present invention is composed of a three-phase input, three inductors, three groups of rectifier bridge arms, three groups of bidirectional switches and positive and negative bus capacitors.

[0035] , as well as Indicates the instantaneous value of the three-phase grid voltage, corresponding to Real-time voltage signal between phases a, b, c and the neutral point or reference point, , , is the three-phase input current, and are the positive and negative bus currents respectively, is the neutral point current, is the load current.

[0036] By controlling the duty cycle of the three groups of switch tubes, synchronous current control and zero-sequence current control can be achieved. Among them, synchronous current control makes the input current and the grid voltage have the same frequency and phase, ensuring that the current waveform is close to a sine wave, and zero-sequence current control balances the DC link voltage by adjusting the neutral point current, reducing current imbalance and improving the power factor.

[0037] In the Vienna rectifier, the source side voltage can be expressed as:

[0038] (1)

[0039] In the formula, , , is the source side voltage, E, Measure the amplitude and angular frequency of the voltage being sourced.

[0040] The state space equation of the Vienna rectifier input side can be expressed as:

[0041] (2)

[0042] In the formula, , , is the voltage at the three ports A, B, and C of the Vienna rectifier.

[0043] The terminal voltage of the rectifier depends on the switching state of the switch and the polarity of the input current. Ignoring the voltage difference Δv between Vdc1 and Vdc2, the function of the terminal voltage for the current polarity and the switching state can be expressed as:

[0044] (3)

[0045] In the formula, , , It is the conduction state of the corresponding phase switch tube (when the switch tube is turned on , , =1).

[0046] Taking the average value of a switching cycle, the average duty cycle of phases a, b, and c can be expressed as:

[0047] (4)

[0048] In the formula, It represents the average conduction time of a three-phase switch tube in a switching cycle. and It is the sinusoidal component and zero-sequence component of the duty cycle of the three phases a, b, and c.

[0049] The output voltage of the Vienna rectifier Divided into and , output capacitor , The capacity is C. According to Kirchhoff's current law, the output current of the Vienna rectifier can be expressed as:

[0050] (7)

[0051] Solving equation (7) yields:

[0052] (8)

[0053] The currents i1 and i2 of the positive and negative busbars are equal to the current flowing through the upper bridge arm diode and the current flowing through the lower bridge arm diode respectively:

[0054] (9)

[0055] The current flowing through the upper arm diode and the current flowing through the lower arm diode can be expressed as:

[0056] (10)

[0057] From formula (10), we can get:

[0058] (11)

[0059] From formula (4) and formula (10), we can get:

[0060] (12)

[0061] The DC side current and midpoint current can be expressed as:

[0062] (13)

[0063] Substituting formula (4) and formula (13) into formula (8), we can obtain:

[0064] (14)

[0065] In order to maintain the DC voltage balance, the neutral point injects current It should always be zero in each pulse interval. Therefore, from the perspective of voltage balance, the optimal zero-sequence component can be expressed as:

[0066] (15)

[0067] Assumptions:

[0068] (16)

[0069] Then formula (14) can be simplified as:

[0070] (17)

[0071] Ignoring all harmonic components and under unity power factor conditions, equation (17) can be further simplified to:

[0072] (18)

[0073] In the formula is the phase current peak value, and formula (18) establishes the zero-sequence component of the three-phase duty cycle The voltage difference between positive and negative busbars The PI controller designed based on this relationship balances the positive and negative bus voltages by adjusting the zero-sequence component of the three-phase duty cycle.

[0074] Figure 2 It is a complete control diagram of the Vienna rectifier using PR control of the present invention, including an improved PR control loop for three-phase current control, an outermost voltage control loop for reference voltage tracking, and an innermost voltage balancing loop for output capacitor voltage balancing.

[0075] The output voltage controller is designed using a standard PI controller. The output of the PI controller is multiplied by the normalized source voltage (amplitude 1) to generate a three-phase reference current signal. To ensure that the reference current is in phase with the measured current, grid synchronization is required.

[0076] The improved PR controller is able to track the reference current signal and helps to remove selected low-order harmonics in the input-side current.

[0077] Voltage balancing is achieved by using a simple PI controller to generate a voltage balancing sequence and adding it to the modulation signal. This control method not only effectively reduces the THD of the source-side current, but also balances the voltage at the output.

[0078] Figure 3 : is the block diagram of the improved PR controller of the present invention. The input of the quasi-PR controller H1 is the current reference value and the actual current measurement value, which can be expressed as:

[0079] (5)

[0080] The standard PR controller cannot reduce the order current harmonics to a great extent. Therefore, an additional shunt compensator is required in parallel with H1. The additional shunt compensator H2 can be expressed as:

[0081] (6)

[0082] The error between the current reference value and the actual current measurement value is input into the PR controller H1, and the output of the PR controller is divided by the DC voltage to obtain a three-phase modulation signal , and . The PR controller H1 is able to track the fundamental component of the current reference value. The transfer function H1 has an attenuation effect on other harmonics except the fundamental component, but it cannot completely remove the 3-nth order low-order current harmonics. Therefore, an additional PR controller H2 is required in parallel with H1. H1 is used to track the fundamental component, and H2 is used to filter out low-order harmonics from the source side current. The larger the low-order harmonic order n, the more parallel loops there are.

[0083] Figure 4This is a principle block diagram of the current reference signal generator when the grid voltage is asymmetric in the present invention. In the case of unbalanced grid, the amplitudes of the source voltages of each phase may be different, which will lead to inconsistency in the reference current amplitude, which may cause a large current imbalance. Therefore, each phase source voltage must be normalized separately to generate a balanced reference current signal with an amplitude of 1. For the phase imbalance problem, the angular frequency (voltage vector angle θ) is generated by the first phase voltage. The angular frequency is used to generate a three-phase reference current signal with appropriate phase correction. In the current control process, the current symmetry of all phases is ensured to achieve current balance.

[0084] Figure 6 and Figure 7 They are respectively the control effect diagram when the three-phase input voltage is unbalanced and the control effect diagram when the three-phase input voltage is disturbed by harmonics. It can be seen that under the disturbance of the grid voltage, the method proposed by the present invention effectively eliminates the harmonic distortion of the input current.

[0085] One embodiment of the present invention, as Figure 5 As shown, a method for reducing harmonic distortion of input current of a Vienna rectifier of an electric vehicle charging module, characterized in that the method comprises:

[0086] S1, compare the actual DC voltage with the reference DC voltage, calculate the error signal, and process the calculated error signal through a voltage regulator (PI controller) to generate a reference voltage;

[0087] S2, generating a three-phase current reference signal according to the phase and amplitude of the grid voltage;

[0088] S3, compare the actual current with the reference current to generate a current error signal, process the generated error signal through an improved proportional resonance (PR) controller, and output a modulation signal , used to control the switch;

[0089] S4. Compare the voltage difference between the upper and lower bridge arms, calculate the neutral point voltage imbalance value, and use the PI controller to adjust the imbalance value to generate a neutral point balance control signal ;

[0090] S5. and The control signals are superimposed to generate a final control signal Sabc; and an optimized switching signal is output through a sinusoidal pulse width modulation (SPWM) method; the switching devices of the Vienna rectifier are controlled through the control signal Sabc to adjust the current on the grid side.

[0091] The working principle of the above technical solution is: compare the actual DC voltage with the preset reference DC voltage to obtain an error signal. This error signal is processed by a voltage regulator (PI controller) to generate a reference voltage. The PI controller can adjust the output according to the size and rate of change of the error, thereby achieving precise control of the DC voltage; according to the phase and amplitude of the grid voltage, a three-phase current reference signal is generated through a corresponding algorithm. These reference signals are used to guide the current output of the rectifier so that it remains in phase with the grid voltage, thereby meeting the requirements of power factor correction; the actual current is compared with the reference current to generate a current error signal. This error signal is processed by an improved proportional resonant (PR) controller. The PR controller has a high gain for error signals at specific frequencies (such as the grid base frequency), so it can effectively reduce the current harmonic distortion at this frequency. The processed signal is converted into a modulated signal , used to control the switching devices of the rectifier; compare the voltage difference between the upper and lower bridge arms to calculate the neutral point voltage imbalance value. This imbalance value is adjusted by the PI controller to generate a neutral point balance control signal The signal is used to adjust the conduction state of the switching device to maintain the balance of the midpoint potential. The balance of the midpoint potential is very important for reducing the harmonic content and improving the power quality; and neutral point balance control signal The control signal Sabc is generated by superposition. This signal is converted into a driving signal for the switching device through the sinusoidal pulse width modulation (SPWM) method. The SPWM method can accurately control the on and off time of the switching device, thereby achieving precise regulation of the rectifier input current.

[0092] The effect of the above technical solution is: by comparing the actual DC voltage with the reference DC voltage and processing it with a PI controller, an accurate reference voltage can be generated. This closed-loop control method can adjust the output voltage of the rectifier in real time to ensure that it remains stable under grid voltage disturbances; the stable DC output voltage helps to reduce the harmonic distortion of the rectifier input current, thereby improving the power quality of the entire power system; generating a three-phase current reference signal based on the phase and amplitude of the grid voltage can ensure that the current waveform of the rectifier is in phase with the grid voltage. This helps to achieve power factor correction, reduce reactive power loss, and improve the efficiency of the power system; using an improved PR controller to process the current error signal can significantly improve the control system's response speed and control accuracy to specific frequencies (such as the grid base frequency). This helps to quickly adjust the input current of the rectifier under grid voltage disturbance and reduce harmonic distortion; Compared with the traditional proportional-integral (PI) controller, the PR controller has better control performance at a specific frequency and can better adapt to the fluctuation and change of grid voltage; By comparing the voltage difference between the upper and lower bridge arms, calculating the neutral point voltage imbalance value, and then adjusting it with the PI controller, a neutral point balance control signal can be generated. This helps to maintain the neutral point potential balance of the three-level converter and prevent the increase of harmonic content caused by the drift of the neutral point potential; Neutral point voltage balance control is one of the key measures to reduce the harmonic distortion of the rectifier input current, which can significantly improve the stability and reliability of the system; The SPWM method is used to output the optimized switching signal, which can accurately control the on and off time of the rectifier switch device. This helps to reduce switching losses and improve the efficiency of the rectifier; At the same time, the SPWM method can also realize the precise adjustment of the rectifier input current and further reduce harmonic distortion; The modulation signal and the neutral point balance control signal are superimposed to generate the final control signal Sabc. This control signal synthesis method can comprehensively consider the requirements of voltage closed-loop control, current closed-loop control and neutral point voltage balance control, and realize effective regulation of the rectifier input current.

[0093] In one embodiment of the present invention, the S1 includes:

[0094] S11, collecting the DC side voltage of the Vienna rectifier in real time through a high-precision DC voltage sensor, and smoothing the collected voltage signal through an analog low-pass filter;

[0095] S12, based on the adaptive filtering algorithm, dynamically adjust the filter cutoff frequency according to the power grid fluctuation;

[0096] S13, according to system requirements and load conditions, based on grid standards and the rated power of the rectifier and through a programming interface, setting a stable reference DC voltage value;

[0097] S14, comparing the actual DC voltage value with the reference DC voltage value, calculating an error signal, and converting the analog error signal into a digital signal through an analog-to-digital converter;

[0098] S15. According to the system response speed and stability requirements, an adaptive PI control strategy is used to dynamically adjust the parameters (proportional gain and integral gain) of the existing PI controller according to the size and change trend of the error signal.

[0099] The working principle of the above technical solution is: use a high-precision DC voltage sensor to collect the DC side voltage of the Vienna rectifier in real time. This sensor can provide high-precision voltage measurement to ensure the accuracy of subsequent processing; the collected voltage signal is smoothed by an analog low-pass filter. The low-pass filter can filter out high-frequency noise and interference, making the voltage signal more stable, which is conducive to subsequent comparison and processing; the cutoff frequency of the filter is dynamically adjusted according to the power grid fluctuation. Power grid fluctuations may cause interference components of different frequencies to appear in the voltage signal. The cutoff frequency of the filter can be adjusted in real time through the adaptive filtering algorithm to effectively filter out these interference components and maintain the purity of the voltage signal; the adaptive filtering algorithm can automatically adjust the filter parameters according to the real-time situation of power grid fluctuations without manual intervention, which improves the automation and response speed of the system; based on system requirements and load conditions, a stable reference DC voltage value is set through the programming interface. This value is determined based on the grid standard and the rated power of the rectifier to ensure that the rectifier can output a stable DC voltage under normal working conditions; the reference voltage value is set using a programming interface (such as a programming interface of a digital signal processor or a microcontroller), which is convenient, flexible and easy to modify; the actual DC voltage value is compared with the reference DC voltage value to calculate the error signal. This error signal reflects the difference between the actual voltage and the expected voltage, and is the basis for the subsequent control algorithm to adjust the rectifier output; the analog error signal is converted into a digital signal through an analog-to-digital converter. The analog-to-digital converter can convert a continuous analog signal into a discrete digital signal, which is convenient for subsequent digital signal processing and control algorithm implementation; according to the system response speed and stability requirements, an adaptive PI control strategy is used to dynamically adjust the parameters (proportional gain and integral gain) of the existing PI controller according to the size and change trend of the error signal. The adaptive PI control strategy can automatically adjust the controller parameters according to the real-time situation of the error signal to achieve a faster and more stable control effect; the adjustment of the proportional gain and integral gain can affect the response speed and steady-state error of the controller. By dynamically adjusting these parameters, the controller can maintain good control performance under different working conditions.

[0100] The effects of the above technical solution are as follows: the DC side voltage of the Vienna rectifier is collected in real time through a high-precision DC voltage sensor, ensuring the accuracy of the collected data; the collected voltage signal is smoothed by an analog low-pass filter, effectively filtering out high-frequency noise and interference, and improving the stability of the signal; the cut-off frequency of the filter is dynamically adjusted according to the grid fluctuation situation, further enhancing the system's adaptability to grid fluctuations; the application of the adaptive filtering algorithm enables the system to maintain a stable DC side voltage output when the grid fluctuates; based on the grid standard and the rated power of the rectifier, a stable reference DC voltage value is set through the programming interface; this set value provides a clear goal for the system, allowing the system to respond quickly and adjust the DC side voltage to reach the set value; the actual DC voltage value is compared with the reference DC voltage value to calculate the error signal; The analog error signal is converted into a digital signal through an analog-to-digital converter, which provides a basis for subsequent digital processing; according to the system response speed and stability requirements, an adaptive PI control strategy is used to process the error signal; the adaptive PI control strategy can dynamically adjust the parameters (proportional gain and integral gain) of the PI controller according to the size and change trend of the error signal, thereby accelerating the response speed of the system; the application of the adaptive PI control strategy enables the system to dynamically adjust the parameters of the PI controller according to different working conditions and load conditions; this dynamic adjustment capability enhances the system's adaptability to different working conditions and load conditions; this technical solution is not only applicable to Vienna rectifiers, but can also be extended to other types of rectifiers and power electronic equipment; by adjusting and optimizing relevant parameters and algorithms, this technical solution can adapt to different application scenarios and requirements.

[0101] In one embodiment of the present invention, the S15 includes:

[0102] Analyze the adaptive PI control strategy, including its working principle, advantages and performance in different application scenarios, and select the most suitable adaptive PI control strategy based on the system response speed and stability requirements, combined with the characteristics of Vienna rectifier and load conditions;

[0103] Through signal processing techniques such as wavelet transform or empirical mode decomposition (EMD), the digital error signal converted by the analog-to-digital converter is feature extracted to obtain its size, change trend and potential frequency components;

[0104] Preprocess the extracted error signal features, such as filtering and denoising; establish a dynamic adjustment model for PI controller parameters (proportional gain and integral gain) based on the system dynamics model and adaptive PI control strategy;

[0105] Based on the parameter adjustment algorithm, the parameters of the PI controller are calculated and updated in real time according to the characteristics and change trends of the error signal;

[0106] Use simulation software or actual system to evaluate the effect of PI controller after parameter adjustment; evaluate the effect of parameter adjustment by comparing indicators such as system response speed, stability and DC voltage fluctuation before and after adjustment.

[0107] According to the evaluation results, the parameter adjustment model, algorithm and adaptive PI control strategy are optimized and iterated.

[0108] The working principle of the above technical solution is: This strategy combines the advantages of traditional PI control and adaptive control, and adjusts PI parameters (proportional gain and integral gain) in real time to adapt to changes in system characteristics and load conditions. According to the system response speed and stability requirements, combined with the characteristics and load conditions of the Vienna rectifier, the most suitable adaptive PI control strategy is selected to improve the efficiency and stability of the rectifier. Use signal processing techniques such as wavelet transform or empirical mode decomposition (EMD) to extract features of the digital error signal converted by the analog-to-digital converter; obtain the size, change trend and potential frequency components of the error signal to provide a basis for subsequent parameter adjustment; perform preprocessing operations such as filtering and denoising on the extracted error signal features to improve the accuracy and reliability of feature extraction; establish a dynamic adjustment model for PI controller parameters based on the system dynamics model and adaptive PI control strategy; calculate and update the parameters of the PI controller in real time according to the characteristics and change trend of the error signal; use simulation software or actual system to evaluate the effect of the PI controller after parameter adjustment; evaluate the effect of parameter adjustment by comparing indicators such as system response speed, stability and DC voltage fluctuation before and after adjustment; optimize and iterate the parameter adjustment model, algorithm and adaptive PI control strategy based on the evaluation results.

[0109] The effect of the above technical solution is: by deeply analyzing and selecting the most suitable adaptive PI control strategy for Vienna rectifier, PI parameters can be adjusted in real time to adapt to changes in system characteristics and load conditions. This adaptive capability significantly improves the response speed and stability of the system, ensuring that excellent control effects can be maintained under various working conditions; the use of advanced signal processing technology to extract and preprocess the error signal can more accurately reflect the actual state of the system. This helps the accuracy and stability of subsequent parameter adjustments, thereby further improving system performance; the PI controller parameter dynamic adjustment model established based on the system dynamics model and the adaptive PI control strategy can reflect changes in system status in real time, and dynamically adjust PI parameters according to the characteristics and change trends of the error signal. This mechanism enables the system to quickly adapt to load changes and power grid fluctuations and maintain a stable control effect; the use of an efficient parameter adjustment algorithm can calculate and update the parameters of the PI controller in real time according to the characteristics of the error signal. This algorithm has good robustness and adaptability, and can maintain a stable control effect under various working conditions; the effect of the PI controller after parameter adjustment is evaluated using simulation software or an actual system, and the system performance difference before and after adjustment can be intuitively compared. This evaluation method helps to quickly identify potential problems and optimize them, improving the overall performance of the system; optimizing and iterating the parameter adjustment model, algorithm, and adaptive PI control strategy based on the evaluation results can continuously improve the control effect and stability of the system. This continuous optimization mechanism enables the system to continuously adapt to new working conditions and load changes and maintain the best control state.

[0110] In one embodiment of the present invention, the S2 includes:

[0111] S21. Obtain the phase and amplitude of the grid voltage through the phase-locked loop technology, and design the three-phase sinusoidal current waveform according to the power factor correction requirements;

[0112] S22, based on the predictive current control technology, the current reference value of the next cycle is calculated in advance according to the predicted value of the grid voltage and the system demand;

[0113] S23. Generate a three-phase current reference signal by combining the phase and amplitude of the grid voltage and the system power demand.

[0114] The working principle of the above technical solution is as follows: First, the phase and amplitude of the grid voltage are accurately obtained through the phase-locked loop (PLL) technology. The phase-locked loop can track the frequency and phase of the grid voltage in real time, providing a basis for the subsequent current waveform design; according to the requirements of power factor correction (PFC), a three-phase sinusoidal current waveform is designed. These waveforms should be in phase with the grid voltage waveform to ensure that the rectifier absorbs the maximum active power and the minimum reactive power from the grid, thereby achieving power factor correction; based on the historical data of the grid voltage and possible future changes, the grid voltage of the next cycle is predicted. This can be achieved through digital signal processing (DSP) technology or machine learning algorithms; based on the predicted value of the grid voltage and system requirements (such as load changes, power output requirements, etc.), the current reference value of the next cycle is calculated in advance using predictive current control technology. This advance calculation helps the rectifier respond to changes in grid voltage and load more quickly and improve the dynamic performance of the system; combined with the phase and amplitude of the grid voltage and the system power requirements, a three-phase current reference signal is generated. These signals are used as inputs to the current controller to guide the regulation of the actual current; in actual applications, the grid may have unbalanced and harmonic problems. Therefore, it is necessary to perform appropriate compensation and filtering on the reference current signal to reduce these adverse effects. Compensation can include adding additional current components to balance the grid current, while filtering can remove high-frequency harmonic components in the reference current signal; the three-phase current reference signal after compensation and filtering is sent to the current controller (such as a proportional resonant controller or a hysteresis current controller) for comparison with the actual current and generating a control signal, thereby adjusting the switching state of the rectifier so that the actual current tracks the reference current.

[0115] The effects of the above technical solutions are as follows: the phase and amplitude of the grid voltage are accurately obtained through the phase-locked loop technology, which provides an accurate basis for designing the three-phase sinusoidal current waveform; the three-phase sinusoidal current waveform designed according to the power factor correction requirements ensures that the rectifier absorbs the maximum active power and the minimum reactive power from the grid, thereby improving the power factor; the designed three-phase sinusoidal current waveform itself has a low harmonic content, which helps to reduce the harmonic pollution of the rectifier to the grid; at the same time, appropriate compensation and filtering of the reference current signal can further reduce the harmonic components and improve the power quality; based on the predictive current control technology, the current reference value of the next cycle can be calculated in advance, so that the rectifier can respond more quickly to changes in grid voltage and load; this ability to calculate in advance helps to improve the dynamic performance of the system and make the whole The rectifier can quickly adjust the output current and maintain stable operation when the load suddenly changes or the power grid fluctuates; considering the influence of power grid imbalance and harmonics, the reference current signal is properly compensated and filtered to enhance the rectifier's adaptability to power grid fluctuations; this adaptability enables the rectifier to maintain stable operation in the case of power grid imbalance or harmonics, thereby improving the robustness of the system; the generated three-phase current reference signal is used as the input of the current controller to accurately guide the regulation of the actual current; this precise guidance helps to reduce current fluctuations and errors and improve the accuracy of current control; precise current control helps to reduce energy loss in the rectification process and improve energy conversion efficiency; at the same time, the optimized current waveform and reduced harmonic content also help to reduce additional power loss and further improve the overall efficiency of the rectifier.

[0116] In one embodiment of the present invention, S3 includes:

[0117] S31, collecting three-phase current in real time through a current sensor, and comparing it with a reference current signal to obtain a current error signal;

[0118] S32, based on the PR controller, a zero-static-error control is performed for a specific frequency (such as base frequency), and an adaptive frequency tracking mechanism is used to enable the PR controller to automatically adapt to changes in the grid frequency;

[0119] S33, converting the output of the PR controller into a modulation signal for controlling the switching devices of the Vienna rectifier; and performing amplitude limiting processing on the modulation signal.

[0120] The working principle of the above technical solution is: the three-phase current is collected in real time through the current sensor. The sampling mode of the current sensor is located on the AC side of the inverter. Regardless of the switching state of the inverter, the current always flows through the three-phase circuit. Therefore, the current sensor sampling has no requirements for the sampling time, which can ensure that the accurate current value is collected; the collected three-phase current is compared with the reference current signal to obtain the current error signal. This step is the key in the control process. It reflects the difference between the actual current and the expected current and provides a basis for subsequent control; the PR controller is a control strategy for accurately tracking AC signals, and its transfer function usually consists of a proportional term and a resonant term. The proportional term is used to ensure the tracking accuracy of the DC component, while the resonant term is used to improve the tracking performance of the AC component. By introducing a resonant term with the same frequency as the signal to be tracked, the PR controller can achieve accurate tracking of the AC signal; and perform zero-static error control for a specific frequency (such as the base frequency). This means that the PR controller can eliminate the steady-state error at the specified frequency and make the actual current as close to the reference current signal as possible; the grid frequency may change due to various factors. Through the adaptive frequency tracking mechanism, the PR controller can automatically adapt to changes in the grid frequency to ensure the accuracy and stability of the control; the output of the PR controller is converted into a modulation signal to control the switching devices of the Vienna rectifier. This step is to convert the output of the control algorithm into an actual execution signal to achieve control of the rectifier switching devices; the modulation signal is limited to avoid exceeding the safe operating range of the switching devices. This is to protect the switching devices from damage by excessive voltage or current and ensure the reliable operation of the rectifier.

[0121] The effect of the above technical solution is: the three-phase current is collected in real time by the current sensor, and compared with the reference current signal, so that the current error signal can be quickly obtained. This real-time feedback mechanism enables the control system to adjust in time, thereby improving the accuracy of current control; based on the PR controller, the specific frequency (such as the base frequency) is controlled without static error, which can eliminate the steady-state error at the specified frequency. This means that the actual current can track the reference current signal more accurately, thereby improving the accuracy of current control; the grid frequency may change due to various factors. Through the adaptive frequency tracking mechanism, the PR controller can automatically adapt to changes in the grid frequency. This adaptability enables the control system to remain stable when the grid frequency fluctuates, thereby enhancing the grid adaptability of the rectifier; the output of the PR controller is converted into a modulated signal and limited to avoid exceeding the safe operating range of the switching device. This protection measure can prevent the switching device from being damaged by excessive voltage or current, thereby improving the stability of the system; since the PR controller is used for static error control and has adaptive frequency tracking capabilities, the technical solution can achieve efficient current control. This helps reduce energy loss and improve the overall efficiency of the rectifier. This technical solution is not only applicable to Vienna rectifiers, but can also be extended to other types of rectifiers and power electronic devices. By adjusting and optimizing relevant parameters and algorithms, this technical solution can adapt to different application scenarios and needs.

[0122] In one embodiment of the present invention, the S32 includes:

[0123] According to the system requirements, select the quasi-PR controller, which can effectively compensate for the static error of the system and achieve zero static error control; set the center frequency of the PR controller according to the base frequency of the power grid (such as 50Hz or 60Hz) and other system characteristics. and bandwidth ;generally, can be set to the corresponding angular frequency of the grid fundamental frequency, and Then make adjustments based on the system's requirements for dynamic response and stability;

[0124] Use phase-locked loop (PLL) or fast Fourier transform (FFT) to detect the change of grid frequency in real time; dynamically adjust the center frequency of PR controller through adaptive algorithm based on the detected grid frequency ;

[0125] Compare the three-phase current collected by the current sensor in real time with the reference current signal to obtain a current error signal; the error signal reflects the difference between the current current and the expected current;

[0126] The current error signal is input into the PR controller, and the output signal of the controller is calculated according to the transfer function and the set parameters of the PR controller;

[0127] Combining the adaptive frequency tracking mechanism with the PR controller to form a complete control system, which automatically adjusts the parameters of the PR controller according to the changes in the grid frequency;

[0128] Use simulation software such as MATLAB / Simulink to simulate and test the integrated control system; verify the effectiveness and stability of the adaptive frequency tracking mechanism by simulating different grid frequency change scenarios;

[0129] At the same time, the output signal of the PR controller is limited.

[0130] The working principle of the above technical solution is as follows: according to the system requirements, a quasi-PR controller that can compensate for static errors and achieve zero-static error control is selected. This controller has the ability to track specific frequency signals without static errors, and is suitable for application scenarios such as power grid frequency control; the center frequency and bandwidth of the PR controller are accurately set according to the base frequency of the power grid (such as 50Hz or 60Hz) and other system characteristics. The center frequency is usually set to the corresponding angular frequency of the base frequency of the power grid, and the bandwidth is adjusted according to the system's requirements for dynamic response speed and stability; using technologies such as phase-locked loop (PLL) or fast Fourier transform (FFT) to detect changes in power grid frequency in real time and accurately. These technologies can capture small fluctuations in power grid frequency and provide basic data for subsequent adaptive adjustments; based on the detected power grid frequency, the center frequency of the PR controller is dynamically adjusted through an adaptive algorithm. This adjustment ensures that the PR controller always keeps consistent with the power grid frequency, thereby maintaining the effect of zero-static error control; the three-phase current is collected in real time by the current sensor, and compared with the reference current signal to obtain the current error signal. This error signal reflects the difference between the current and the expected current and is the basis for the controller to make adjustments. The current error signal is input into the PR controller, and the output signal of the controller is calculated according to the transfer function of the PR controller and the set parameters (including the adjusted center frequency and bandwidth). This output signal is used to guide the switching devices of the Vienna rectifier to act to eliminate the current error. The adaptive frequency tracking mechanism is combined with the PR controller to form a complete control system. This system can automatically adjust the parameters of the PR controller according to the changes in the grid frequency to achieve zero-static control. The integrated control system is simulated and tested using simulation software such as MATLAB / Simulink. The effectiveness and stability of the adaptive frequency tracking mechanism are verified by simulating different grid frequency change scenarios. These tests can ensure that the control system has good performance and reliability in practical applications. The output signal of the PR controller is limited to prevent the control signal from exceeding the tolerance range of the Vienna rectifier switching device. This treatment can protect the switching device from damage and ensure the safe operation of the system.

[0131] The effect of the above technical solution is: by selecting a quasi-PR controller, the technical solution can effectively compensate for the static error of the system and achieve zero-static error control. This means that the system can track the desired current value more accurately, reduce current fluctuations and errors, and thus improve the control accuracy and stability of the entire system. This is crucial for power electronic systems that require high-precision current control. By using technologies such as phase-locked loop (PLL) or fast Fourier transform (FFT) to detect changes in grid frequency in real time, and dynamically adjusting the center frequency w_0 of the PR controller through an adaptive algorithm, the technical solution realizes adaptive tracking of grid frequency changes. This adaptive capability enables the system to maintain a stable control effect when the grid frequency fluctuates, enhancing the robustness and adaptability of the system. By comparing the three-phase current collected by the current sensor in real time with the reference current signal, a current error signal is obtained, and the error signal is input into the PR controller for processing. The technical solution can quickly respond to the current error and calculate a suitable control signal to eliminate the error. This optimization process enables the system to have a faster response speed and higher control efficiency. The integrated control system is simulated and tested using simulation software such as MATLAB / Simulink. By simulating different grid frequency change scenarios, the effectiveness and stability of the adaptive frequency tracking mechanism are verified. This simulation test method can fully verify and optimize the system before actual application to ensure that the system can maintain reliable control effects under various working conditions. The output signal of the PR controller is limited to prevent the control signal from exceeding the tolerance range of the Vienna rectifier switching device. This protection measure can effectively prevent the switching device from being damaged due to overcurrent, extend the service life of the equipment, and reduce the maintenance cost of the system.

[0132] In one embodiment of the present invention, the S4 includes:

[0133] S41, real-time monitoring of the voltage difference between the upper and lower bridge arms of the Vienna rectifier, and amplification of the voltage difference signal through a differential amplifier; and calculation of the neutral point voltage unbalance value as a basis for neutral point balance control;

[0134] S42, based on the PI controller, the neutral point balance control signal is calculated according to the neutral point voltage unbalance value, and the integral separation PI control strategy is adopted to stop the integral action when the error signal is small. At the same time, an anti-saturation mechanism is introduced to avoid control failure caused by integrator saturation;

[0135] S43: superimpose the neutral point balance control signal and the basic modulation signal to generate a final control signal.

[0136] The working principle of the above technical solution is: the system monitors the voltage difference between the upper and lower bridge arms of the Vienna rectifier in real time. This step is the basis of neutral point balance control. By accurately measuring the voltage difference, key data can be provided for subsequent control; the voltage difference signal is amplified by the differential amplifier. The differential amplifier can effectively extract and amplify the tiny voltage difference signal, thereby improving the accuracy and sensitivity of the measurement; the amplified voltage difference signal is processed to calculate the neutral point voltage imbalance value. This value reflects the degree of deviation of the neutral point voltage of the Vienna rectifier and is an important basis for neutral point balance control; the PI controller consists of a proportional term and an integral term, and can calculate the control signal according to the error signal. The proportional term is used to quickly respond to changes in the error signal, while the integral term is used to eliminate steady-state errors. In this embodiment, an integral separation PI control strategy is adopted. When the error signal is small, the integral action is stopped to avoid over-regulation of the integrator when the error is close to zero. This strategy helps to improve the stability and response speed of the control system. In order to avoid control failure caused by integrator saturation, the system introduces an anti-saturation mechanism. When the integrator reaches saturation, the mechanism can limit the further integration of the integrator, thereby preventing the control signal from exceeding the safe operating range of the switching device; the neutral point balance control signal is calculated based on the neutral point voltage imbalance value and the output of the PI controller. This signal will be used to adjust the state of the switching device of the Vienna rectifier to achieve balanced control of the neutral point voltage; the basic modulation signal is the modulation signal required for the normal operation of the Vienna rectifier, which is used to control the opening and closing of the switching device; the neutral point balance control signal is superimposed on the basic modulation signal to generate the final control signal. This step integrates the requirements of neutral point balance control into the normal operation of the Vienna rectifier, thereby achieving balanced control of the neutral point voltage.

[0137] The effect of the above technical solution is: by real-time monitoring of the voltage difference between the upper and lower bridge arms of the Vienna rectifier and amplifying the voltage difference signal using a differential amplifier, the imbalance information of the neutral point voltage can be accurately obtained. The use of the differential amplifier improves the accuracy and sensitivity of the measurement and provides a reliable data basis for subsequent control; the amplified voltage difference signal is processed to calculate the neutral point voltage imbalance value and serve as the basis for neutral point balance control. This precise calculation method enables the control system to more accurately identify the imbalance state of the neutral point voltage and take effective control measures; the calculation of the neutral point balance control signal based on the PI controller can achieve a rapid response to the neutral point voltage imbalance. The proportional term and the integral term of the PI controller work together to enable the control system to quickly adjust and reduce the error when the error is large; when the error is small, it can remain stable and avoid over-adjustment; the integral separation PI control strategy is adopted to stop the integral action when the error signal is small. This strategy avoids the over-adjustment of the integrator when the error is close to zero, thereby enhancing the stability of the control system. At the same time, it also improves the response speed of the control system, allowing the control system to reach a stable state faster; an anti-saturation mechanism is introduced to avoid control failure caused by integrator saturation. When the integrator reaches saturation, the anti-saturation mechanism can limit the further integration of the integrator, thereby preventing the control signal from exceeding the safe operating range of the switching device. This improves the reliability and safety of the control system; through precise neutral point balance control, the neutral point voltage of the Vienna rectifier can be balanced to reduce voltage fluctuations and imbalance. This helps to reduce the power loss of the rectifier, improve energy conversion efficiency, and extend the service life of the rectifier; the balance control of the neutral point voltage can also improve the output quality of the Vienna rectifier. Stable output voltage and current waveforms help reduce harmonic and noise interference and improve the output stability and reliability of the rectifier. This technical solution has a wide range of applicability and can adapt to different application scenarios and needs. By adjusting the parameters and algorithms of the PI controller, flexible response to different loads and grid conditions can be achieved to meet the needs of various complex application scenarios.

[0138] In one embodiment of the present invention, S5 includes:

[0139] S51, based on the SPWM algorithm, the control signal is converted into a driving signal of the switching device. At the same time, the modulation range is expanded and the dynamic performance of the system is improved through modulation technology;

[0140] S52, performing dead time compensation and harmonic suppression processing on the generated switching signal; wherein the dead time compensation takes into account the switching speed of the switching device and the influence of the dead time; the harmonic suppression processing reduces the harmonic content through a filter or a harmonic elimination algorithm, etc.;

[0141] S53, outputting the optimized switch signal to the switch device of the Vienna rectifier through the isolation drive circuit;

[0142] S54, controlling the switch device of the Vienna rectifier according to the control signal to accurately adjust the current on the grid side;

[0143] S55. Feedback the grid-side current value in real time through the current sensor to form a closed-loop control system. The closed-loop control system compares the fed-back current value with the reference current signal and continuously corrects the control signal.

[0144] The working principle of the above technical solution is: based on the sinusoidal pulse width modulation (SPWM) algorithm, the control signal is converted into a driving signal for the switching device. The SPWM algorithm generates a driving signal of a PWM waveform by comparing the sinusoidal wave modulation signal and the high-frequency triangular wave carrier signal, thereby controlling the on and off of the switching device; during the conversion process, the modulation range is expanded by modulation technology to improve the dynamic performance of the system. This includes adjusting the amplitude and phase of the modulation wave, and optimizing the frequency and waveform of the carrier signal, so as to achieve more precise control of the switching device; considering the switching speed and dead time of the switching device, the generated switching signal is compensated for the dead time. The existence of dead time is to avoid short circuit caused by the simultaneous conduction of the upper and lower switching devices of the same bridge arm. By accurately calculating and compensating the dead time, the switching loss and electromagnetic interference can be reduced, and the efficiency of the rectifier can be improved; the harmonic content can be reduced by using methods such as filters or harmonic elimination algorithms. Harmonics are an inevitable problem in the rectification process, which will increase the pollution of the power grid and the loss of the rectifier. Through effective harmonic suppression processing, the harmonic content can be reduced, the output quality of the rectifier and the stability of the power grid can be improved; the optimized switching signal is output to the switching device of the Vienna rectifier through the isolation drive circuit. The function of the isolation drive circuit is to isolate the electrical connection between the control signal and the switching device, and protect the control system from the influence of high voltage and large current; the switching device of the Vienna rectifier is controlled according to the control signal to accurately adjust the current on the grid side. By adjusting the on and off time of the switching device, the output voltage and current waveform of the rectifier can be controlled, so as to achieve accurate regulation of the current on the grid side; the current value of the grid side is fed back in real time through the current sensor to form a closed-loop control system. The function of the current sensor is to monitor the current changes on the grid side in real time, and convert these changes into electrical signals to feed back to the control system; the closed-loop control system compares the feedback current value with the reference current signal and continuously corrects the control signal. By comparing the actual current value with the expected reference current signal, the control system can calculate the error and adjust the control signal according to this error to reduce the error and achieve the expected current value.

[0145] The effect of the above technical solution is as follows: the technical solution converts the control signal into the driving signal of the switching device based on the sinusoidal pulse width modulation (SPWM) algorithm. The SPWM algorithm can generate high-quality PWM waveforms to ensure accurate control of the switching device; through modulation technology, the modulation range is expanded to improve the dynamic performance of the system. This means that the system can respond to changes in current and voltage more quickly, thereby improving the stability and reliability of the rectifier; considering the switching speed and dead time of the switching device, the generated switching signal is compensated for the dead time. This step can reduce switching losses, because the existence of dead time will cause the switching device to generate additional power consumption during the conduction and shutdown process; at the same time, dead time compensation can also reduce electromagnetic interference (EMI), because it reduces the possibility of simultaneous conduction of the switching device, thereby reducing potential short-circuit current and electromagnetic noise; through methods such as filters or harmonic elimination algorithms, the harmonic content is reduced. Harmonics are inevitable problems in the rectification process, they will increase the pollution of the power grid and the loss of the rectifier; effective harmonic suppression processing can reduce the harmonic content, improve the output quality of the rectifier and the stability of the power grid. This is of great significance for protecting power grid equipment, reducing power grid losses and improving power quality; the optimized switching signal is output to the switching device of the Vienna rectifier through the isolation drive circuit. The isolation drive circuit can ensure the electrical isolation between the control signal and the switching device, thereby protecting the control system from high voltage and high current; this improves the safety of the control system and ensures the precise control of the switching device. Because the isolation drive circuit can prevent the control signal from being affected by the electromagnetic interference and noise generated by the switching device; the switching device of the Vienna rectifier is controlled according to the control signal to accurately adjust the current on the grid side. This step is the core of the rectifier's work, which determines the output current and voltage waveform of the rectifier; by accurately controlling the on and off time of the switching device, the current on the grid side can be accurately adjusted. This is of great significance for maintaining the stability of the grid and improving the power quality; the current value on the grid side is fed back in real time through the current sensor to form a closed-loop control system. The closed-loop control system can continuously correct the control signal based on the feedback current value and the reference current signal; this step improves the accuracy and stability of the control. Because the closed-loop control system can detect changes in grid-side current in real time and adjust the control signal according to these changes, thus ensuring that the output current of the rectifier always remains within the desired range.

[0146] In one embodiment of the present invention, the method further comprises:

[0147] Constructing a three-level coordinated control architecture, wherein the three-level coordinated control architecture includes an improved proportional resonance (PR) current control loop, an outermost voltage tracking control loop, and an innermost voltage balancing control loop;

[0148] In the improved proportional resonant current control loop, a combined structure of a fundamental wave tracking module and a multi-resonant peak parallel compensator is adopted to directly control the three-phase current in the abc coordinate system;

[0149]

[0150] in, Used to track the fundamental current component, It is used to filter out the 3rd, 5th and 7th low-order harmonics, where n is the harmonic order. , , are proportional gain, resonant gain and damping coefficient respectively; Represents the second-order dynamic characteristics; Represents the resonant frequency; among them, the fundamental wave tracking ; Harmonic tracking ; In the outermost voltage tracking control loop, the DC side output voltage error is converted into a normalized reference current signal through a PI controller; specifically including:

[0151] Generate synchronous angular frequency based on the first phase voltage , generate symmetrical three-phase reference current signals through coordinate transformation , , ;

[0152] In the innermost voltage balance control loop, the positive and negative bus voltage difference is derived according to Kirchhoff's current law With zero sequence component The relationship is:

[0153]

[0154] and will Add to modulating signal , , , to adjust the neutral point current , to dynamically balance the positive and negative bus voltages;

[0155] Generate the final modulated signal , driving the Vienna rectifier switching device through sinusoidal pulse width modulation (SPWM); Represents the modulation signal.

[0156] The working principle of the above technical solution is as follows: the control architecture includes an improved proportional resonant (PR) current control loop, an outermost voltage tracking control loop and an innermost voltage balancing control loop. These three loops work together to ensure that the Vienna rectifier can operate stably and efficiently; in the improved proportional resonant current control loop, a combination structure of a fundamental wave tracking module and a multi-resonant peak parallel compensator is used to directly control the three-phase current in the abc coordinate system. Used to track the fundamental current component to ensure that the rectifier can accurately follow the waveform of the input voltage, thereby achieving high power factor operation. It is used to filter out low-order harmonics such as the 3rd, 5th, and 7th order to reduce the harmonic content of the input current and improve the power quality; the control parameters in this loop include proportional gain, resonant gain, and damping coefficient. The selection of these parameters is critical to the stability and performance of the system. The DC side output voltage error is converted into a normalized reference current signal through a PI controller. This helps to ensure that the output voltage of the rectifier can stably track the set value. The synchronous angular frequency θ is generated based on the first phase voltage, and a symmetrical three-phase reference current signal is generated through coordinate transformation. These signals serve as inputs to the current control loop to guide the current regulation of the rectifier. The relationship between the positive and negative bus voltage difference and the zero-sequence component is derived according to Kirchhoff's current law. This step is the key to ensuring the dynamic balance of the positive and negative bus voltages of the rectifier. Added to the original modulated signal , , To generate the final modulation signal This regulation process is achieved by adjusting the neutral point current To achieve the balance of positive and negative bus voltages. Use sinusoidal pulse width modulation technology to drive the switching devices of the Vienna rectifier. SPWM technology can accurately control the on and off of the switching devices, thereby achieving efficient energy conversion and precise control of the output voltage.

[0157] The effect of the above technical solution is: by adopting a combined structure of a fundamental wave tracking module and a multi-resonance peak parallel compensator in an improved proportional resonance (PR) current control loop, the three-phase current can be directly and accurately controlled in the abc coordinate system. Used to track the fundamental current component to ensure that the rectifier can accurately follow the waveform of the input voltage, thereby achieving high power factor operation; It is used to filter out low-order harmonics such as the 3rd, 5th, and 7th order, effectively reduce the harmonic content of the input current, improve the power quality, and meet international harmonic standards. The selection of control parameters such as proportional gain, resonant gain, and damping coefficient is crucial to the stability and performance of the system. Through reasonable parameter design, the accuracy of current control and the stability of the system can be further improved. In the outermost voltage tracking control loop, the DC side output voltage error is converted into a normalized reference current signal through a PI controller. This design helps to ensure that the output voltage of the rectifier can stably track the set value and improve the accuracy and stability of voltage control. The synchronous angular frequency θ is generated based on the first phase voltage, and a symmetrical three-phase reference current signal is generated through coordinate transformation. These signals, as inputs to the current control loop, can guide the rectifier to perform precise current regulation, thereby further enhancing the effect of voltage tracking. In the innermost voltage balance control loop, the relationship between the positive and negative bus voltage difference and the zero-sequence component is derived according to Kirchhoff's current law. By adjusting , which can realize the neutral point current Accurately control the positive and negative bus voltages to achieve dynamic balance. Added to the original modulated signal , , The final modulation signal is generated The switching devices of the Vienna rectifier are driven by sinusoidal pulse width modulation (SPWM) technology, which ensures that the rectifier can operate stably and efficiently under various working conditions.

[0158] In one embodiment of the present invention, the execution steps of the improved PR current control loop include:

[0159] Input current error signal Pass in sequence and , output modulation signal ; Represents the three-phase reference current signal; Indicates the three-phase actual current signal;

[0160] The parallel compensator The resonant frequency is set to the harmonic frequency to be suppressed and can be extended to higher harmonics.

[0161] The working principle of the above technical solution is: first, calculate the three-phase current error signal , that is, the reference current signal The actual current signal The current error signal Input to fundamental wave tracking module middle. The function of is to track the fundamental current component to ensure that the rectifier can accurately follow the waveform of the input voltage. The processed signal is then input to the parallel compensator middle. The resonant frequency is set to the harmonic frequency to be suppressed, such as the 3rd, 5th, 7th and other low-order harmonics, and its resonant frequency can be extended to higher-order harmonics. The function of the filter is to filter out the harmonics of these specific frequencies to reduce the harmonic content of the input current. and The processed signal is finally output as a modulated signal These modulation signals will be used to control the switching devices of the Vienna rectifier to achieve accurate current control. The improved PR current control loop is realized by It can track the fundamental current component to ensure that the rectifier can accurately follow the waveform of the input voltage and achieve high power factor operation. Filter out harmonics of specific frequencies, reduce the harmonic content of input current, and improve power quality. The resonant frequency can be set according to the harmonic frequency to be suppressed, which provides great flexibility. The resonant frequency can filter out different harmonics to meet different application requirements. Due to the combined structure of the fundamental tracking module and the multi-resonance peak parallel compensator, the improved PR current control loop can achieve precise control of the three-phase current. This helps to improve the performance and stability of the rectifier and ensure stable and efficient operation under various working conditions.

[0162] The effect of the above technical solution is: by calculating the input current error signal , that is, the reference current signal The actual current signal The difference between the input current and the output current ensures the accuracy of current control. This step is the basis of the current control loop and provides accurate input for subsequent processing. The input current error signal is passed through and to be processed. It is mainly responsible for tracking the fundamental current component to ensure that the rectifier can accurately follow the input voltage waveform and achieve high power factor operation. As a parallel compensator, its resonant frequency is set to the harmonic frequency to be suppressed, effectively filtering out these harmonics and further improving the accuracy of current control. The resonant frequency can be flexibly set according to actual needs, not only limited to low-order harmonics such as 3rd, 5th, 7th, etc., but also extended to higher-order harmonics. This flexibility enables the control loop to suppress harmonic problems in different application scenarios in a targeted manner. By accurately suppressing harmonics of specific frequencies, the improved PR current control loop significantly reduces the harmonic content of the input current, reduces harmonic pollution to the power grid, and improves the quality of power. This is of great significance for protecting power grid equipment and ensuring stable operation of the power grid. The improved PR current control loop reduces current fluctuations and overshoots by accurately controlling the current, thereby enhancing the stability of the system. This is crucial to ensure that the rectifier can operate stably under various operating conditions. Because the control loop has high precision and harmonic suppression capabilities, it can better cope with external interference factors such as load changes and power grid fluctuations, and improves the robustness of the system. This enables the rectifier to maintain excellent performance in various complex environments.

[0163] In one embodiment of the present invention, in the voltage tracking control loop, the method for normalizing the grid voltage is:

[0164] The voltage amplitude of each phase is independently normalized to unity, that is, , , ,in , , is the measured amplitude of each phase voltage; , as well as Indicates the instantaneous value of the three-phase grid voltage, corresponding to Real-time voltage signal between phase a, b, c and neutral point or reference point;

[0165] Using the phase-locked loop (PLL) alternative, the first phase voltage vector angle Generates a synchronous frequency to ensure that the reference current is in phase with the grid voltage.

[0166] The working principle of the above technical solution is: the amplitude of each phase voltage (such as phase a, phase b, and phase c) is independently normalized to the unit value. A certain phase-locked loop (PLL) alternative is adopted, which can generate the synchronization frequency using the first phase voltage vector angle θ. Normalization is achieved by dividing the instantaneous value of each phase voltage by its corresponding measured amplitude. This process converts the amplitude of each phase voltage to a unit value (i.e., 1 or a value close to 1), which facilitates subsequent comparison and control. Using the phase-locked loop (PLL) alternative, by detecting the first phase voltage vector angle θ of the grid voltage, a synchronization signal with the same frequency as the grid voltage can be generated. The specific implementation of the phase-locked loop (PLL) alternative may involve a variety of circuits and technologies, such as phase detectors, filters, voltage-controlled oscillators, etc., which work together to achieve phase locking and frequency synchronization. After obtaining the normalized phase voltages and synchronization frequencies, the control system can begin to perform the voltage tracking control task. By comparing the difference between the actual voltage and the reference voltage (which may be generated based on the synchronous frequency), the control system can adjust its output (such as the duty cycle of the PWM signal, etc.) to control the output voltage and current of the inverter or other power electronic equipment. The ultimate goal is to make the actual voltage consistent with the reference voltage in both phase and amplitude, thereby achieving voltage tracking control.

[0167] The effect of the above technical solution is that the voltage amplitude of each phase is independently normalized to the unit value, eliminating the influence of the voltage amplitude difference on the control system. The normalized voltage signal is easier to process and compare, which improves the accuracy and response speed of the control system. The synchronization frequency is generated by using the first phase voltage vector angle θ to ensure the phase consistency of the reference current and the grid voltage. This synchronization mechanism reduces the phase error and improves the stability and accuracy of the voltage tracking control. The normalization process makes the control system more adaptable to the fluctuation of the grid voltage. Even if the grid voltage changes, the normalized voltage signal can still remain relatively stable, thereby ensuring the stable operation of the control system. The use of a phase-locked loop (PLL) alternative avoids the complexity of the traditional PLL design. This alternative may be implemented based on a simpler circuit or algorithm, reducing system cost and design difficulty. Ensuring that the reference current is in phase with the grid voltage helps to optimize the current waveform and reduce the harmonic content. This not only improves the power quality, but also helps to reduce the loss and heat of power electronic equipment. Through precise voltage tracking control, the effective use of the grid voltage is achieved. This helps to improve the energy utilization rate of the entire power system and reduce energy waste. Normalization and synchronous frequency generation simplify the debugging process of the control system. Engineers can more easily adjust system parameters to achieve the best control effect. When a system failure occurs, normalization and synchronous frequency generation provide clearer fault indications; help engineers quickly locate and solve problems, and reduce maintenance costs and time.

[0168] In one embodiment of the present invention, in the voltage balance control loop, the zero sequence component The generation satisfies:

[0169] Derivation of neutral point current according to Kirchhoff's law With positive and negative bus current , The relationship is:

[0170]

[0171] By adjusting Make Approaches zero in each switching cycle, Represents the switch state variable, thereby achieving .

[0172] The principle and effect of the above technical solution are: by adjusting the zero sequence component , so that the neutral point current Approaching zero during each switching cycle, this helps reduce voltage fluctuations in the system. When it approaches zero, the charge exchange between the positive and negative bus bars decreases, thus maintaining the positive and negative bus bar voltages. and This voltage stability is crucial for the stable operation of the power system, especially in situations where high voltage accuracy is required. , can optimize the current distribution in the system. In a three-phase power system, unbalanced current distribution may cause problems such as equipment overheating and reduced efficiency. , can make the three-phase current more balanced, thereby improving the overall efficiency and stability of the system. When it decreases, the energy loss in the system will also decrease accordingly. This is because The reduction of means that the charge exchange between the positive and negative busbars is reduced, thereby reducing the loss of energy during transmission. This is of great significance for improving the energy efficiency of the power system and reducing energy waste. By accurately controlling the voltage balance and current distribution, this technical solution can enhance the reliability of the system. In the power system, the instability of voltage and current may cause equipment failure, system shutdown and other problems. This technical solution helps to reduce the occurrence of these problems by maintaining voltage balance and optimizing current distribution, thereby improving the reliability and stability of the system. This technical solution is not only applicable to three-phase power systems, but can also be extended to other multi-phase power systems. In addition, it can also be combined with other power control technologies, such as PWM (pulse width modulation) control, SVG (static var generator) control, etc., to achieve more complex power control goals.

[0173] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for reducing harmonic distortion of input current of Vienna rectifier of electric vehicle charging module, characterized in that: The method comprises: S1, comparing the actual DC voltage with the reference DC voltage, calculating an error signal, and processing the calculated error signal through a voltage regulator to generate a reference voltage; S2, generating a three-phase current reference signal according to the phase and amplitude of the grid voltage; S3, compare the actual current with the reference current to generate a current error signal, process the generated error signal through the improved proportional resonant controller, and output a modulation signal , used to control the switch; S4. Compare the voltage difference between the upper and lower bridge arms, calculate the neutral point voltage imbalance value, and use the PI controller to adjust the imbalance value to generate a neutral point balance control signal ; S5. and The control signals Sabc are superimposed to generate the final control signal Sabc; and the optimized switching signal is output through the sinusoidal pulse width modulation method; the switching devices of the Vienna rectifier are controlled through the control signal Sabc to adjust the current on the grid side.

2. According to claim 1, a method for reducing harmonic distortion of input current of Vienna rectifier of electric vehicle charging module is characterized in that: Said S1 comprises: S11, collecting the DC side voltage of the Vienna rectifier in real time through a high-precision DC voltage sensor, and smoothing the collected voltage signal through an analog low-pass filter; S12, based on the adaptive filtering algorithm, dynamically adjust the filter cutoff frequency according to the power grid fluctuation; S13, according to system requirements and load conditions, based on grid standards and the rated power of the rectifier, and setting the reference DC voltage value through the programming interface; S14, comparing the actual DC voltage value with the reference DC voltage value, calculating an error signal, and converting the analog error signal into a digital signal through an analog-to-digital converter; S15. According to the system response speed and stability requirements, an adaptive PI control strategy is used to dynamically adjust the parameters of the existing PI controller according to the size and change trend of the error signal.

3. According to claim 1, a method for reducing harmonic distortion of input current of Vienna rectifier of electric vehicle charging module is characterized in that: The S2 comprises: S21. Obtain the phase and amplitude of the grid voltage through the phase-locked loop technology, and design the three-phase sinusoidal current waveform according to the power factor correction requirements; S22, based on the predictive current control technology, the current reference value of the next cycle is calculated in advance according to the predicted value of the grid voltage and the system demand; S23. Generate a three-phase current reference signal by combining the phase and amplitude of the grid voltage and the system power demand.

4. A method for reducing harmonic distortion of input current of Vienna rectifier of electric vehicle charging module according to claim 1, characterized in that: The S3 includes: S31, collecting three-phase current in real time through a current sensor, and comparing it with a reference current signal to obtain a current error signal; S32, based on the PR controller, zero-static-error control is performed for a specific frequency, and the PR controller is automatically adapted to the change of the grid frequency through an adaptive frequency tracking mechanism; S33, converting the output of the PR controller into a modulation signal for controlling the switching devices of the Vienna rectifier; and performing amplitude limiting processing on the modulation signal.

5. A method for reducing harmonic distortion of input current of Vienna rectifier of electric vehicle charging module according to claim 1, characterized in that: The S4 comprises: S41, real-time monitoring of the voltage difference between the upper and lower bridge arms of the Vienna rectifier, and amplification of the voltage difference signal through a differential amplifier; and calculation of the neutral point voltage unbalance value; S42, based on the PI controller, the neutral point balance control signal is calculated according to the neutral point voltage unbalance value, and the integral separation PI control strategy is adopted to stop the integral action when the error signal is small; S43: superimpose the neutral point balance control signal and the basic modulation signal to generate a final control signal.

6. A method for reducing harmonic distortion of input current of Vienna rectifier of electric vehicle charging module according to claim 1, characterized in that: The S5 comprises: S51, based on the SPWM algorithm, the control signal is converted into a driving signal of the switching device. At the same time, the modulation range is expanded and the dynamic performance of the system is improved through modulation technology; S52, performing dead time compensation and harmonic suppression processing on the generated switching signal; wherein the dead time compensation takes into account the switching speed of the switching device and the influence of the dead time, and the harmonic suppression processing reduces the harmonic content through a filter or a harmonic elimination algorithm; S53, outputting the optimized switch signal to the switch device of the Vienna rectifier through the isolation drive circuit; S54, controlling the switch device of the Vienna rectifier according to the control signal to adjust the current on the grid side; S55. Feedback the grid-side current value in real time through the current sensor to form a closed-loop control system. The closed-loop control system compares the fed-back current value with the reference current signal and continuously corrects the control signal.

7. A method for reducing harmonic distortion of input current of Vienna rectifier of electric vehicle charging module according to claim 1, characterized in that: The method further comprises: Constructing a three-level collaborative control architecture, wherein the three-level collaborative control architecture includes an improved proportional resonant current control loop, an outermost voltage tracking control loop, and an innermost voltage balancing control loop; In the improved proportional resonant current control loop, a combined structure of a fundamental wave tracking module and a multi-resonant peak parallel compensator is adopted to directly control the three-phase current in the abc coordinate system; in, Used to track the fundamental current component, It is used to filter out the 3rd, 5th and 7th low-order harmonics, where n is the harmonic order. , , are proportional gain, resonant gain and damping coefficient respectively; Represents the second-order dynamic characteristics; Represents the resonant frequency; among them, the fundamental wave tracking ; Harmonic tracking ; In the outermost voltage tracking control loop, the DC side output voltage error is converted into a normalized reference current signal through a PI controller; specifically including: Generate synchronous angular frequency based on the first phase voltage , generate symmetrical three-phase reference current signals through coordinate transformation , , ; In the innermost voltage balance control loop, the positive and negative bus voltage difference is derived according to Kirchhoff's current law With zero sequence component The relationship is: and will Add to modulating signal , , , to adjust the neutral point current , dynamically balance the positive and negative bus voltages; generate the final modulation signal , driving the Vienna rectifier switching devices through sinusoidal pulse width modulation.

8. A method for reducing harmonic distortion of input current of Vienna rectifier of electric vehicle charging module according to claim 7, characterized in that: The execution steps of the improved PR current control loop include: Input current error signal Pass and , output modulation signal ; Represents the three-phase reference current signal; Represents the actual three-phase current signal; the parallel compensator The resonant frequency is set to the harmonic frequency to be suppressed and can be extended to higher harmonics.

9. A method for reducing harmonic distortion of input current of Vienna rectifier of electric vehicle charging module according to claim 7, characterized in that: In the voltage tracking control loop, the method for normalizing the grid voltage is: The voltage amplitude of each phase is independently normalized to unity, that is, , , ,in , , is the measured amplitude of each phase voltage; , as well as It represents the instantaneous value of the three-phase grid voltage, corresponding to the real-time voltage signal between phases a, b, c and the neutral point or reference point; through the phase-locked loop alternative solution, the first phase voltage vector angle is used Generates a synchronous frequency to ensure that the reference current is in phase with the grid voltage.

10. A method for reducing harmonic distortion of input current of Vienna rectifier of electric vehicle charging module according to claim 7, characterized in that: In the voltage balance control loop, the zero sequence component The generation of satisfies: According to Kirchhoff's law, the neutral point current is derived With positive and negative bus current , The relationship is: By adjusting Make Approaches zero in each switching cycle, Represents the switch state variable, thereby achieving .

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