Voltage feedforward control method and device, grid-connected converter, electronic equipment and readable storage medium

Abstract

This application discloses a voltage feedforward control method, device, grid-connected converter, electronic equipment, and computer-readable storage medium, belonging to the field of power electronic control technology. The method includes: acquiring the voltage signal and output current signal at the common coupling point of the grid-connected converter; extracting the fundamental frequency component of the voltage signal; weighting and fusing the original voltage component and the fundamental frequency component based on preset weighting coefficients to generate a hybrid feedforward signal; and combining this with a current closed-loop control signal to generate a modulation signal to control the converter. This application, through a hybrid weighted feedforward mechanism, achieves a trade-off between weak grid stability, dynamic response performance, and grid voltage background harmonic suppression capability by adjusting only a single parameter, while ensuring error-free fundamental frequency tracking. This resolves the technical contradiction that traditional solutions cannot simultaneously address multiple performance indicators.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a voltage feedforward control method, device, grid-connected converter, electronic equipment, and readable storage medium. Background Technology

[0002] As a key interface between renewable energy generation systems and the power grid, the control performance of grid-connected converters directly affects power quality and system stability. To suppress the impact of grid voltage distortion on grid-connected current, point of common coupling (PCC) voltage feedforward control is a widely used technique.

[0003] However, in weak grid operation scenarios where grid impedance cannot be ignored, the feedforward control schemes in related technologies have inherent limitations. Specifically, to ensure the stability of the system under weak grid conditions, it is often necessary to suppress or modify the effect of feedforward control, but this usually directly weakens its core capabilities of improving dynamic response and suppressing grid background harmonics. Summary of the Invention

[0004] This application provides a power grid voltage feedforward control method, device, grid-connected converter, electronic device, and readable storage medium, which realizes feedforward control that can effectively coordinate system stability, dynamic performance, and harmonic suppression capability under weak power grid conditions, so as to at least partially solve the above-mentioned technical problems.

[0005] In a first aspect, embodiments of this application provide a voltage feedforward control method, including: Based on the voltage signal at the common coupling point of the grid-connected converter, the fundamental frequency component of the voltage signal is extracted; Based on preset weighting coefficients, the original component of the voltage signal is fused with the fundamental frequency component to generate a hybrid feedforward signal; A current closed-loop control signal is generated based on the output grid-connected current signal of the grid-connected converter. Based on the current closed-loop control signal and the hybrid feedforward signal, a modulation signal for controlling the grid-connected converter is generated.

[0006] Optionally, the value of the weighting coefficient is determined based on at least one of the following performance requirements of the grid-connected converter under weak grid conditions: stability, dynamic response performance, and grid voltage harmonic suppression capability.

[0007] Optionally, the weighting coefficient shall be no less than the larger of the minimum value determined to meet the dynamic response performance requirements of the grid-connected converter and the minimum value determined to meet the grid voltage harmonic suppression capability requirements, and shall not exceed the maximum allowable value determined to meet the weak grid stability requirements.

[0008] Optionally, the step of extracting the fundamental frequency component of the voltage signal based on the voltage signal at the common coupling point of the grid-connected converter includes: The voltage signal is subjected to fundamental frequency separation processing to obtain the phase-locked angle and the positive-sequence component and negative-sequence component of the fundamental frequency; The fundamental frequency positive sequence component and the fundamental frequency negative sequence component are combined by coordinate synthesis to obtain the fundamental frequency component of the voltage signal.

[0009] Optionally, the step of performing fundamental frequency separation processing on the voltage signal to obtain the phase-locked angle and the positive-sequence component and negative-sequence component of the fundamental frequency includes: The voltage signal is subjected to phase-locked loop and positive / negative sequence decoupling processing, and the decoupled components are filtered to obtain the fundamental frequency positive sequence component and the fundamental frequency negative sequence component.

[0010] Optionally, the step of performing coordinate synthesis processing on the fundamental frequency positive-sequence component and the fundamental frequency negative-sequence component to obtain the fundamental frequency component of the voltage signal includes: The fundamental frequency positive sequence component and the fundamental frequency negative sequence component are respectively transformed to two-phase stationary coordinate systems by inverse coordinate transformation and then added together to obtain the fundamental frequency component of the voltage signal.

[0011] Optionally, the step of fusing the original component of the voltage signal with the fundamental frequency component based on a preset weighting coefficient to generate a hybrid feedforward signal includes: The hybrid feedforward signal is obtained by adding the product of the original component and the weighting coefficient, and the product of the fundamental frequency component and a compensation coefficient; wherein the sum of the compensation coefficient and the weighting coefficient is 1.

[0012] Optionally, the step of generating a current closed-loop control signal based on the output grid-connected current signal of the grid-connected converter includes: Based on the phase-locked angle, the output grid-connected current signal is subjected to closed-loop adjustment in a rotating coordinate system synchronized with the grid voltage, and the adjusted signal is inversely transformed to a stationary coordinate system to generate the current closed-loop control signal.

[0013] Secondly, embodiments of this application also provide a voltage feedforward control device, comprising: The fundamental frequency extraction module is used to receive the voltage signal at the common coupling point of the grid-connected converter and extract the fundamental frequency component of the voltage signal. The weighted feedforward synthesis module is used to receive the original component of the voltage signal and the fundamental frequency component output by the fundamental frequency extraction module, and to fuse the original component of the voltage signal and the fundamental frequency component based on a preset weighting coefficient to generate a hybrid feedforward signal. The current control module is used to receive the output grid-connected current signal of the grid-connected converter and generate a current closed-loop control signal. The modulation signal generation module is used to receive the hybrid feedforward signal output by the weighted feedforward synthesis module and the current closed-loop control signal output by the current control module, and generate a modulation signal for controlling the grid-connected converter based on the current closed-loop control signal and the hybrid feedforward signal.

[0014] Thirdly, embodiments of this application also provide a grid-connected converter, including a power conversion circuit and the aforementioned voltage feedforward control device, wherein the voltage feedforward control device is used to generate a modulation signal to drive the power conversion circuit.

[0015] Fourthly, embodiments of this application also provide an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described method.

[0016] Fifthly, embodiments of this application also provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the above-described method.

[0017] This embodiment of the application adjusts the weighting coefficients to construct the feedforward signal as a weighted combination of the original voltage signal and its fundamental frequency component. This ensures that regardless of the weighting coefficient values, the hybrid feedforward signal always contains a fundamental frequency information path composed of the fundamental frequency component, thereby guaranteeing zero steady-state error tracking of the fundamental frequency command. By adjusting the weighting coefficients... k A compromise is achieved between the stability of weak power grids, dynamic response performance, and the ability to suppress background harmonics of grid voltage. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart of the voltage feedforward control method provided in an exemplary embodiment of this disclosure; Figure 2 This is a schematic diagram of the output sequence impedance Bode plot of the grid-connected converter provided in the exemplary embodiments of this disclosure under different weighting coefficients; Figure 3 This disclosure provides, through exemplary embodiments, the grid-connected current corresponding to different weighting coefficients under the condition of sudden changes in three-phase grid voltage. dSchematic diagram of axis component response waveform; Figure 4 This is a schematic diagram of the grid-connected current waveform and total harmonic distortion rate corresponding to different weighting coefficients when the grid voltage contains background harmonics, provided by an exemplary embodiment of this disclosure. Figure 5 This is a schematic diagram of the grid-connected current simulation waveforms corresponding to different weighting coefficients under a weak grid condition with a short-circuit ratio of 2, provided by an exemplary embodiment of this disclosure. Figure 6 This is a schematic diagram of the structure of the voltage feedforward control device provided in an exemplary embodiment of this disclosure; Figure 7 This is a schematic diagram of the implementation structure of the voltage feedforward control device provided in an exemplary embodiment of this disclosure; Figure 8 This is a schematic diagram of the implementation structure of the baseband separation unit provided in an exemplary embodiment of this disclosure; Figure 9 This is a schematic diagram of the structure of a grid-connected converter provided in an exemplary embodiment of this disclosure. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0022] "A and / or B" includes the following three combinations: A only, B only, and a combination of A and B.

[0023] The use of "applies to" or "configured to" in this application implies open and inclusive language, which does not exclude the applicability to or configuration to devices performing additional tasks or steps. Additionally, the use of "based on" implies openness and inclusivity, because processes, steps, calculations, or other actions "based on" one or more of the stated conditions or values ​​may in practice be based on additional conditions or values ​​beyond those stated.

[0024] In this application, the term "exemplary" is used to mean "used as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use this application. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that this application can be made without using these specific details. In other instances, well-known structures and processes are not described in detail to avoid obscuring the description of this application with unnecessary detail. Therefore, this application is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.

[0025] The grid voltage feedforward control method for grid-connected converters provided in this application can be applied to grid-connected power generation systems that include renewable energy sources. In such systems, the electrical energy generated by power generation units (such as photovoltaic arrays, wind turbines, etc.) is fed into the grid-connected converter via a DC link. This grid-connected converter mainly includes a power conversion circuit, a filter circuit connected to its AC side, and a control device. The control device receives the grid voltage signal from the point of common coupling and the grid-connected output current signal of the converter, and executes the control method provided in this application to generate a corresponding modulation signal. This modulation signal is used to drive the power switching devices in the power conversion circuit, thereby converting the electrical energy on the DC link side into AC power synchronized with the grid, and feeding it into the grid via the filter circuit, achieving high-quality grid connection. Optionally, such grid-connected power generation systems may include photovoltaic grid-connected converters, wind power converters, energy storage converters, and other equipment or systems.

[0026] This embodiment provides a voltage feedforward control method, such as... Figure 1 As shown, it includes the following steps: Step S101: Extract the fundamental frequency component of the voltage signal based on the voltage signal at the common coupling point of the grid-connected converter.

[0027] The voltage signal at the point of common coupling can be in three-phase form or in two-phase form after coordinate transformation. The purpose of extracting the fundamental frequency component is to obtain a signal that can accurately reflect the fundamental component of the grid voltage and whose dynamic characteristics are controllable.

[0028] In one specific embodiment, the voltage signal is subjected to phase-locked loop (PLL), decoupling, and filtering processes to extract the fundamental frequency component of the grid voltage signal. For example, the voltage phase can be obtained through a PLL circuit, and high-frequency harmonic components can be filtered out using a filter (such as a low-pass filter) to separate the fundamental frequency component.

[0029] Step S102: Based on preset weighting coefficients, the original components of the voltage signal and the fundamental frequency component are fused to generate a hybrid feedforward signal.

[0030] The weighting coefficient is an adjustable parameter, with a value ranging from, for example, 0 to 1. The weighted combination can be a linear combination. This can be achieved by adjusting... k The value allows for flexible adjustment of the ratio of the original voltage signal (containing all spectral information) to the pure fundamental frequency signal in the feedforward path.

[0031] Step S103: Generate a current control signal based on the output grid-connected current signal of the grid-connected converter.

[0032] This step enables the grid-connected current to accurately track a given reference command. In one specific embodiment, a closed-loop control strategy is employed, namely, generating a current closed-loop control signal. For example, the three-phase grid-connected current output from the converter can be acquired, compared with a current reference value, and the resulting error signal is adjusted by a controller (such as a proportional-integral controller) to ultimately generate a control signal for correcting the current.

[0033] Step S104: Generate a modulation signal for controlling the grid-connected converter based on the current control signal and the hybrid feedforward signal.

[0034] In one specific embodiment, the synthesis method involves adding the two signals together. For example, in the same coordinate system (e.g., two stationary phases). αβ In a coordinate system, the current control signal is added to the corresponding components of the hybrid feedforward signal, and the resulting sum signal can be used as the input of modulation algorithms such as space vector pulse width modulation (SVPWM) to generate pulse signals that drive power switching devices.

[0035] This application's embodiments introduce an adjustable weighting coefficient. k The feedforward signal is constructed as a weighted combination of the original voltage signal and its fundamental frequency component, regardless of the weighting coefficients. k The values ​​are determined so that the hybrid feedforward signals all contain a fundamental frequency information path composed of fundamental frequency components, thereby ensuring zero steady-state error tracking of the fundamental frequency command; by adjusting the weighting coefficients... k A compromise is achieved between the stability of weak power grids, dynamic response performance, and the ability to suppress background harmonics of grid voltage.

[0036] In some embodiments, weighting coefficients k The value of is determined based on at least one of the performance requirements of the grid-connected converter under weak grid conditions: stability, dynamic response performance, and grid voltage harmonic suppression capability.

[0037] In this embodiment, the weighting coefficient kThe value of is not an arbitrarily chosen empirical value, but a key design parameter directly related to the core performance indicators of the system. First, it is necessary to clarify the specific performance requirements of the converter for these three (or some of them) indicators under the target application scenario, such as the dynamic performance corresponding to the maximum current overshoot under voltage surges. Then, through modeling (such as establishing an output impedance model of the converter) and simulation analysis, the following is studied... k The influence of value changes on various performance indicators.

[0038] By adjusting k The value can be used to systematically adjust the proportion of the original signal and the fundamental frequency signal in the feedforward. When it is necessary to enhance the ability to quickly suppress grid voltage fluctuations or background harmonics, the value can be increased. k The value can be increased by raising the original proportional feedforward ratio; when it is necessary to prioritize ensuring the system stability margin under weak grid conditions, the value can be reduced. k The value is mainly achieved by relying on fundamental frequency feedforward, which does not affect the stability of mid-to-high frequencies. Therefore, this method effectively coordinates and optimizes the three key and mutually restrictive performance indicators of weak grid stability, dynamic response performance, and grid harmonic suppression capability under a single control framework, solving the technical problem that feedforward control schemes in related technologies cannot simultaneously take into account the above-mentioned multi-objective performance.

[0039] In some embodiments, the weighting coefficient is set to be no less than the larger of the minimum value determined to meet the dynamic response performance requirements of the grid-connected converter and the minimum value determined to meet the grid voltage harmonic suppression capability requirements, and no more than the maximum allowable value determined to meet the weak grid stability requirements.

[0040] Specifically, weighting coefficients k The range of values ​​for satisfies: max ( k min1 , k min2 ) ≤ k ≤ k max ,in, k max This is the maximum allowable value determined based on the output sequence impedance model of the grid-connected converter and the stability requirements of a weak power grid. k min1 This is the minimum dynamic performance value determined based on the maximum allowable overshoot of the grid-connected current under the condition of sudden voltage changes. k min2 This is the minimum harmonic suppression value determined based on the maximum permissible total harmonic distortion (THD) of the grid-connected current.

[0041] k max This can be determined through stability analysis. k min1 andk min2 The weighting coefficients can be determined based on dynamic performance or harmonic suppression requirements. The determination of the weighting coefficients will be explained below with reference to the attached figures. k The process and principle of how the value is obtained will be explained.

[0042] Please see Figure 2 The grid-connected converter provided in this application embodiment has different weighting coefficients. k The following is a schematic diagram of the output sequence impedance Bode plot. Figure 2 As shown, when the weighting coefficients k The amplitude-frequency and phase-frequency characteristic curves of the output impedance of the grid-connected converter are shown when the values ​​are 1, 0.5, and 0, respectively. According to the impedance stability criterion, system stability can be evaluated by the phase relationship between the converter output impedance and the grid impedance at the intersection frequency. Under the weak grid impedance characteristic with a short-circuit ratio (SCR, the ratio of grid short-circuit capacity to converter rated capacity) of 2, it can be observed that as the weighting coefficient increases... k As the frequency decreases, the phase of the converter output impedance gradually increases near the cutoff frequency. Specifically, when... k When = 1, the phase margin is negative (e.g., -11°), and the system becomes unstable; when k When = 0.5, the phase margin turns positive (e.g., 4°); when k When the weighting factor is 0, the phase margin increases further (e.g., by 14°). This indicates that reducing the weighting factor... k It helps improve the stability of grid-connected converters under weak grid conditions.

[0043] Based on the above principles, in order to meet the preset weak network adaptability target, such as requiring the system to have a certain phase margin under the target short-circuit ratio, the weighting coefficients that can ensure system stability can be solved by analyzing the converter output impedance model. k Maximum allowed value k max . k max These are the boundary conditions for stability.

[0044] Please see Figure 3 The different weighting coefficients provided in this application embodiment are for the condition of sudden voltage changes (e.g., 60° phase shift) in a three-phase power grid. k Corresponding grid current d A schematic diagram of the axis component response waveform. (See diagram below.) Figure 3 As shown, comparison k From the current response under the three conditions of =1, 0.5, and 0, it can be seen that as... k The decrease in value, grid-connected current dThe transient overshoot or peak value of the axis components increases significantly, for example, in other embodiments of this application, under the condition of a 60° change in three-phase grid voltage. k =1 indicates an overshoot of approximately 46%. k At a value of 0.5, the overshoot is approximately 57%. k When the value is 0, the overshoot is approximately 69%. k When the weighting factor is 0, the peak current may exceed the safety threshold, posing a risk of instantaneous overcurrent. This indicates that a larger weighting factor... k It helps to suppress current surges caused by sudden voltage changes in the power grid, and improves the dynamic response performance and anti-disturbance capability of the system.

[0045] Therefore, based on the specific requirements of the system for dynamic performance, such as specifying the maximum allowable overshoot of the grid-connected current when the grid voltage changes abruptly, the minimum weighting coefficient value that can meet this dynamic performance index can be determined through simulation or experiment. k min1 .

[0046] Please refer to Figure 4 The different weighting coefficients provided in the embodiments of this application when the grid voltage contains background harmonics. k The corresponding grid-connected current waveform and its total harmonic distortion (THD) diagram are shown below. Figure 4 As shown, with the weighting coefficients k As the voltage decreases, the distortion of the grid-connected current waveform intensifies, and its THD value gradually increases. When k When = 1, the feedforward has the strongest harmonic compensation effect and the lowest THD; when k When the weighting factor decreases, the proportional component in the feedforward weakens, reducing its ability to suppress background harmonics and leading to a deterioration in the grid-connected current quality. This indicates that a larger weighting factor... k It can more effectively suppress the impact of background harmonics on grid-connected current and improve current quality.

[0047] Therefore, based on the system's requirements for the harmonic content of the grid-connected current, such as specifying the maximum allowable THD, the minimum weighting coefficient value that can meet the harmonic suppression requirement can be determined through analysis or testing. k min2 .

[0048] Based on the above analysis, the weighting coefficients k The value of is constrained by three factors: weak network stability (upper limit), dynamic performance (lower limit), and grid harmonic immunity (lower limit). Among these, the stability constraint requires... k ≤ k max This is to ensure stable system operation under weak network conditions. Dynamic performance constraints require... k ≥ k min1This is to ensure that the current response does not become excessive during dynamic processes such as voltage surges. Harmonic immunity constraints require... k ≥ k min2 This is to ensure sufficient suppression of background harmonics in the power grid.

[0049] Therefore, in order to simultaneously consider the weak grid adaptability, dynamic performance, and disturbance immunity requirements of grid-connected converters, the weighting coefficients are... k The final range of values ​​should be determined as follows: max ( k min1 , k min2 ) ≤ k ≤ k max The method for establishing this range allows the control strategy of this application to be controlled by an adjustable parameter ( k This systematically and quantitatively achieves the optimization and trade-off of multiple performance objectives.

[0050] Please see Figure 5 This application provides embodiments of different weighting coefficients under weak network conditions with SCR=2. k The corresponding grid-connected current simulation waveform diagram. (See diagram below.) Figure 5 As shown, the waveform verifies the above analysis: when k When = 1, the current diverges, and the system is unstable; when k =0.5 and k When =0, the current tends to stabilize, and k The smaller the value, the smaller the overshoot in the steady-state convergence process, but combined with... Figure 3 It can be seen that its dynamic disturbance rejection capability will be weakened.

[0051] In some embodiments, extracting the fundamental frequency component of the voltage signal based on the voltage signal at the common coupling point of the grid-connected converter includes: The voltage signal is subjected to fundamental frequency separation processing to obtain the phase-locked angle and the positive-sequence and negative-sequence components of the fundamental frequency; The fundamental frequency positive-sequence component and the fundamental frequency negative-sequence component are combined by coordinate synthesis to obtain the fundamental frequency component of the voltage signal.

[0052] In some embodiments, the voltage signal undergoes fundamental frequency separation processing to obtain the phase-locked angle and the positive-sequence and negative-sequence components of the fundamental frequency, including: The voltage signal is subjected to phase-locked loop and positive / negative sequence decoupling processing, and the decoupled components are filtered to obtain the fundamental frequency positive sequence component and the fundamental frequency negative sequence component.

[0053] Specifically, filtering the decoupled components is called low-pass filtering.

[0054] First, the grid voltage signal is subjected to phase-locked loop processing to obtain the phase angle (i.e., phase-locked angle) of its fundamental component in real time. θ This is the foundation for achieving synchronous operation with the power grid and all subsequent processing based on rotating coordinate transformation. Phase-locked loops (PLLs) can be implemented using various types of PLLs.

[0055] Because real-world power grids may exhibit imbalances, voltage components simultaneously contain both positive-sequence and negative-sequence elements. Positive-negative sequence decoupling processing separates these components. For example, using the symmetric component method, specific transformation matrices are constructed, or a dual-channel processing structure is employed, to extract voltage components in both the positive-sequence and negative-sequence rotating coordinate systems, respectively.

[0056] In the decoupled positive-sequence and negative-sequence rotating coordinate systems, the fundamental frequency voltage component appears as a DC or low-frequency AC signal, while harmonic interference appears as a high-frequency signal. Therefore, low-pass filtering of the decoupled signal can effectively filter out high-frequency harmonics, thus obtaining a pure fundamental frequency positive-sequence voltage component (e.g., in the positive-sequence rotating coordinate system). dq In the coordinate system u dp_filter , u qp_filter ) and the fundamental frequency negative sequence voltage component (e.g., in negative sequence rotation) dq In the coordinate system u dn_filter , u qn_filter The cutoff frequency of a low-pass filter is typically set slightly above the fundamental frequency to strike a balance between maintaining dynamic response and filtering out harmonics.

[0057] In some embodiments, the step of performing phase-locked loop and positive / negative sequence decoupling processing on the voltage signal includes: The voltage signal is phase-locked and decoupled in terms of positive and negative sequence by decoupling the dual synchronous reference coordinate system phase-locked loop.

[0058] In some embodiments, the fundamental frequency positive-sequence component and the fundamental frequency negative-sequence component are subjected to coordinate synthesis to obtain the fundamental frequency component of the voltage signal, including: The fundamental frequency positive-sequence component and the fundamental frequency negative-sequence component are respectively transformed to two-phase stationary coordinate systems and then added together to obtain the fundamental frequency component of the voltage signal.

[0059] Specifically, the above-mentioned positive-sequence rotating coordinate system voltage components after low-pass filtering ( u dp_filter , u qp_filter By inverse Park transformation, the system is transformed back to a two-phase stationary coordinate system. αβ (coordinate system), to obtain the corresponding positive sequence fundamental frequency filter component ( uαp_filter , u βp_filter Similarly, the filtered negative-order rotating coordinate system voltage components ( u dn_filter , u qn_filter Perform an inverse Park transform to obtain the negative-order fundamental frequency filter component. u αn_filter , u βn_filter ).

[0060] The positive-sequence fundamental frequency filter components and the negative-sequence fundamental frequency filter components in the stationary coordinate system are added together accordingly, i.e., the calculation is performed. u α_filter = u αp_filter + u αn_filter as well as u β_filter = u βp_filter + u βn_filter 。 The signal obtained in the two-phase stationary coordinate system u α_filter and u β_filter This refers to the final extracted grid voltage fundamental frequency filter component, which contains the fundamental positive and negative sequence information.

[0061] In this embodiment, through the aforementioned processing steps of phase-locked loop, positive-negative sequence decoupling, filtering, inverse transformation, and synthesis, a pure fundamental frequency component can be extracted from the complex actual power grid voltage with high precision and high dynamics. This fundamental frequency component does not contain mid-to-high frequency harmonics; therefore, when used as part of the feedforward, it does not introduce additional mid-to-high frequency coupling paths to the control system. This ensures that the feedforward channel formed by this fundamental frequency component effectively compensates for the fundamental voltage while minimizing potential negative impacts on the system's stability in the mid-to-high frequency range.

[0062] It should be noted that the above processing can be implemented using various algorithms or hardware logic. One specific implementation method is to use a decoupled dual-synchronous reference coordinate system phase-locked loop, the detailed structure and workflow of which will be described in detail in the subsequent embodiments of the device with reference to the accompanying drawings.

[0063] In some embodiments, based on preset weighting coefficients, the original component of the voltage signal and the fundamental frequency component are fused to generate a hybrid feedforward signal, including: Combine the original components with the weighting coefficients k The product of the fundamental frequency component and the compensation coefficient (1- kThe products of (1-) are added together to obtain the hybrid feedforward signal. Among them, the compensation coefficient (1-) k ) and weighting coefficients k The sum is 1.

[0064] Specifically, the original components of the voltage signal are weighted and fused with the fundamental frequency component, which is achieved through the following formula: U FeedForward = k U org + (1- k ) U filter in, U org For the original components, U filter For the fundamental frequency component, U FeedForward It is a mixed feedforward signal.

[0065] parameter k These are preset weighting coefficients, with values ​​between 0 and 1. When k When =1, the hybrid feedforward signal U FeedForward Completely equal to the original voltage signal U org This is the traditional pure proportional feedforward; when k When =0, U FeedForward Completely equal to the fundamental frequency component U filter This is a pure fundamental frequency feedforward; when 0 < k <1 hour, U FeedForward This is a linear mixture of the two.

[0066] U org and U filter They need to be expressed in the same coordinate system, for example, both are two-phase stationary coordinate systems ( αβ The components in a coordinate system. In a specific embodiment, the weighted fusion is calculated in a two-phase stationary coordinate system using the following formula: u α _ FeedForward = k u α + (1 - k ) uα _ filter u β _ FeedForward = k u β + (1 - k ) u β _ filter in, u α _ FeedForward , u β _ FeedForward To mix the components of the feedforward signal, u α , u β These are the components of the original voltage signal. u α _ filter , u β _ filter This is the fundamental frequency component.

[0067] The linear weighting formula described above clearly defines the ratio of the original signal to the fundamental frequency signal in the synthesis, ensuring that the gain of the fundamental frequency channel is always (1- k ), structurally ensuring that regardless of k Regardless of how the value changes, the gain contribution of the entire feedforward path to the fundamental voltage component is at least (1- k ).

[0068] In some embodiments, a current closed-loop control signal is generated based on the output grid-connected current signal of the grid-connected converter, including: Based on the phase-locked angle, the output grid-connected current signal is subjected to closed-loop regulation in a rotating coordinate system synchronized with the grid voltage, and the regulated signal is inversely transformed to a stationary coordinate system to generate a current closed-loop control signal.

[0069] The current closed-loop control signal generated based on the output grid-connected current signal utilizes the synchronization information (phase-locked angle) obtained from the grid voltage signal to achieve precise and rapid tracking and regulation of the grid-connected current in a coordinate system that is easy to control.

[0070] Based on the phase-locked angle, the output grid-connected current signal is subjected to closed-loop regulation in a rotating coordinate system synchronized with the grid voltage to achieve high-performance control of the AC grid-connected current. Specifically, the phase-locked angle (…) obtained from the base frequency extraction step is used… θ The collected three-phase output grid-connected current signal (i 2a , i 2b , i 2c Transform from a three-phase stationary coordinate system to a coordinate system that rotates synchronously with the grid fundamental voltage (usually called a coordinate system). dq (Rotating coordinate system). In this rotating coordinate system, the fundamental grid current, which is originally a sinusoidal alternating current, is converted into a relatively easy-to-control direct current or a slowly changing variable. Subsequently, closed-loop regulation is implemented on the current signal in this rotating coordinate system. The purpose of the closed-loop regulation is to enable the actual grid-connected current to quickly and accurately track the given current control target. In a specific embodiment, the current feedback component in the rotating coordinate system (e.g., d Axial components i 2d and q Axial components i 2q ) and the corresponding current command value (such as the grid-connected current output reference value) I 2d_ref and I 2q_ref The error signal is obtained by comparing the two signals, and then processed by an appropriate regulator (e.g., a proportional-integral controller) to generate a voltage control command in the rotating coordinate system (e.g., ...). u id , u iq ).

[0071] After completing closed-loop regulation and generating the corresponding control signal in the rotating coordinate system, the signal needs to be converted back to the stationary coordinate system (usually two-phase) used when the controller finally outputs the modulation signal. αβ (Stationary coordinate system). This transformation is also based on phase-locked angles ( θ This is performed by executing a coordinate transformation operation that is the opposite of the aforementioned transformation (e.g., inverse Park transformation), changing the control signals in the rotating coordinate system. u id , u iq The current closed-loop control signal in the stationary coordinate system is obtained after transformation. u iα , u iβ ).

[0072] By employing a closed-loop regulation strategy based on a rotating coordinate system using phase-locked angles, this embodiment effectively achieves zero steady-state error tracking of the grid-connected current to the command value and high-performance dynamic response. Converting AC control into DC regulation simplifies controller design and improves control accuracy. The generation of this current closed-loop control signal is independent of the aforementioned hybrid weighted feedforward signal, yet they remain synchronized through shared phase-locked angle information. Both are ultimately synthesized in a stationary coordinate system, ensuring the system's steady-state tracking performance and inherent stability through current closed-loop control, while voltage feedforward provides rapid compensation for grid disturbances. These two elements complement each other, forming a complete control system. The specific implementation of the closed-loop regulation (such as the type of regulator used) can be selected and designed according to actual performance requirements and is not limited to a particular form.

[0073] In some embodiments, a modulation signal for controlling the grid-connected converter is generated based on the current closed-loop control signal and the hybrid feedforward signal, including: The current closed-loop control signal and the hybrid feedforward signal are added together to obtain the modulation signal in the two-phase stationary coordinate system.

[0074] Specifically, the current closed-loop control signal (e.g., when both phases are stationary) will be used. αβ Represented in coordinate system as u iα , u iβ ) and the hybrid feedforward signal (represented in the same coordinate system as u α _ FeedForward and u β _ FeedForward The synthesis is performed by adding components on the same coordinate axes. The final two-phase stationary coordinate system modulated voltage signal is calculated using the following formula: u cα = u iα + u α _ FeedForward u cβ = u iβ + u β _ FeedForward in, u cα and u cβ This refers to the component of the modulation signal used to control the converter in the two-phase stationary coordinate system.

[0075] This addition operation achieves the parallel superposition of feedforward and feedback in the control system. Current closed-loop control signal. u iα , u iβ It primarily undertakes the control functions generated by the system to eliminate grid-connected current errors, and is responsible for ensuring system stability, steady-state accuracy, and command tracking capability. Hybrid feedforward signal. u α _ FeedForward and u β _ FeedForward This primarily provides active and rapid compensation for measurable disturbances (i.e., grid voltage). The output of the control system can be considered as the superposition of the tracking response to the reference input and the compensation response to the disturbance input. Through adder synthesis, the final modulation voltage command of the converter simultaneously includes the dynamic and steady-state components of the closed-loop regulation, as well as the real-time disturbance compensation component provided by the feedforward channel. This achieves faster and more accurate integrated control of the grid-connected current and effectively enhances the system's immunity to grid voltage fluctuations.

[0076] The obtained modulation signal u cα and u cβ Typically, the signal needs to undergo a subsequent modulation stage before it can be converted into a pulse signal that actually drives the power switching devices (such as IGBTs and MOSFETs) of the converter to turn on and off. In one specific embodiment, the modulation method is space vector pulse width modulation (SVPWM). This modulation stage receives... u cα and u cβ As an input voltage vector command, the duty cycle and conduction sequence of each power switch are calculated according to a specific algorithm, and finally the corresponding drive pulse sequence is generated to control the desired voltage waveform output on the AC side of the converter.

[0077] Please see Figure 6 This is a schematic diagram of the voltage feedforward control device 20 provided in an embodiment of this application. The device 20 can be implemented in software, hardware, or a combination of both. For example... Figure 6 As shown, the device 20 includes: The fundamental frequency extraction module 21 is used to receive the voltage signal at the common coupling point of the grid-connected converter, extract and output the fundamental frequency component of the voltage signal.

[0078] The weighted feedforward synthesis module 22 is used to receive the original component of the voltage signal and the fundamental frequency component output by the fundamental frequency extraction module 21, and to fuse the original component of the voltage signal and the fundamental frequency component according to the preset weighting coefficients to generate and output a hybrid feedforward signal.

[0079] The current control module 23 is used to receive the output grid-connected current signal of the grid-connected converter and generate a current closed-loop control signal.

[0080] The modulation signal generation module 24 is used to receive the hybrid feedforward signal output by the weighted feedforward synthesis module 22 and the current closed-loop control signal output by the current control module 23, and generate a modulation signal for controlling the grid-connected converter based on the hybrid feedforward signal and the current closed-loop control signal.

[0081] It should be noted that, Figure 6 Each of the functional modules shown can be implemented by one or more processors (such as digital signal processors (DSPs), microcontrollers (MCUs), field-programmable gate arrays (FPGAs), or application-specific integrated circuits (ASICs)) executing program instructions stored in one or more memories.

[0082] In one specific implementation, device 20 can be integrated into the controller of a grid-connected converter, which includes a processor and memory.

[0083] The voltage feedforward control device 20 separates the pure fundamental frequency component from the grid voltage signal through the fundamental frequency extraction module 21, and then fuses it with the original voltage component according to adjustable weights through the weighted feedforward synthesis module 22 to form a hybrid feedforward signal. This hybrid feedforward signal is then synthesized with the closed-loop control signal generated by the current control module 23 in the modulation signal generation module 24. This structure allows the device to flexibly adjust the proportion of dynamic response components and stability components in the feedforward channel by a single weighting coefficient while ensuring accurate tracking of the grid voltage fundamental frequency. This effectively coordinates the operating stability, dynamic response speed, and suppression capability of grid voltage background harmonics of the grid-connected converter under weak grid conditions, overcoming the shortcomings of traditional feedforward schemes that cannot simultaneously achieve the above multiple performance indicators.

[0084] Please also refer to Figure 7 This is a schematic diagram of the implementation structure of the voltage feedforward control device provided in the embodiments of this application.

[0085] like Figure 7 As shown, the input terminal of the baseband extraction module 21 is used to receive the three-phase voltage signal from the common coupling point (PCC) of the grid-connected converter 30. u a , u b , u c ), which is the original component of the voltage signal.

[0086] In some embodiments, the fundamental frequency extraction module 21 includes a fundamental frequency separation unit 210 and a coordinate synthesis unit 211. The fundamental frequency separation unit 210 receives a voltage signal, performs fundamental frequency separation processing on the voltage signal, and outputs the phase-locked angle and the positive-sequence and negative-sequence components of the fundamental frequency. The coordinate synthesis unit 211 receives the positive-sequence and negative-sequence components of the fundamental frequency output by the fundamental frequency separation unit 210, performs coordinate synthesis processing on the positive-sequence and negative-sequence components of the fundamental frequency, and outputs the fundamental frequency component of the voltage signal.

[0087] Specifically, the baseband separation unit 210 first uses a phase-locked loop (PLL) to separate the input three-phase voltage ( u a , u b , u c Phase-locked loop (PLL) processing is performed to generate a rotation angle synchronized with the grid fundamental voltage. θ That is, the phase-locked angle. Simultaneously, the baseband separation unit 210 will also separate the three-phase voltage ( u a , u b , u c The fundamental frequency (FFM) is decomposed into positive-sequence and negative-sequence components, and harmonic components are filtered out to obtain pure fundamental positive-sequence and fundamental negative-sequence components. These components are typically decomposed in a rotating coordinate system (FFM). dq In coordinate system, it is represented as u dp_filter , u qp_filter (positive sequence fundamental frequency component) and u dn_filter , u qn_filter (Negative sequence fundamental frequency component).

[0088] In some embodiments, the coordinate synthesis unit 211 is used to perform inverse coordinate transformation on the fundamental frequency positive sequence component and the fundamental frequency negative sequence component respectively to the two-phase stationary coordinate system and then add them together to output the fundamental frequency component of the voltage signal.

[0089] In one specific embodiment, the coordinate synthesis unit 211 internally includes a first coordinate inverse transformer 2111, a second coordinate inverse transformer 2112, a first adder 2113, and a second adder 2114. The first coordinate inverse transformer 2111 is used to convert the fundamental frequency positive sequence component output by the fundamental frequency separation unit 210 (…) u dp_filter , u qp_filter Through inverse Park transformation, it is transformed to a two-phase stationary coordinate system. αβ Voltage components in coordinate system ( u αp_filter ,u βp_filter The second coordinate inverse transformer 2112 is used to convert the fundamental frequency negative sequence component output by the fundamental frequency separation unit 210 ( u dn_filter , u qn_filter Through inverse Park transformation, it is transformed to a two-phase stationary coordinate system. αβ Voltage components in coordinate system ( u αn_filter , u βn_filter Subsequently, the first adder 2113 converts the voltage component output by the first coordinate inverse transformer 2111 into a voltage component. u αp_filter , u αn_filter The output is the fundamental frequency filtered component of the grid voltage in the two-phase stationary coordinate system. u α_filter The second adder 2114 converts the voltage component output by the second coordinate inverse transformer 2112 into ( ). u βp_filter , u βn_filter The output is the fundamental frequency filtered component of the grid voltage in the two-phase stationary coordinate system. u β_filter ).

[0090] In some embodiments, the weighted feedforward synthesis module 22 includes a computation unit 220 for combining the original components with weighting coefficients. k The product of the fundamental frequency component and the coefficient (1- k The product of ) and the sum of them yields the hybrid feedforward signal.

[0091] The weighted feedforward synthesis module 22 has two input terminals: the first input terminal is directly connected to the voltage signal input terminal to receive the original three-phase PCC voltage. u a , u b , u c The second input terminal is connected to the output terminal of the baseband extraction module 21 and is used to receive the baseband filtered component. u α_filter , u β_filter The weighted feedforward synthesis module 22 linearly fuses the original components of the voltage signal with the fundamental frequency component according to the preset weighting coefficient k (0 ≤ k ≤ 1).

[0092] In one specific embodiment, the arithmetic unit 220 includes a first weighted calculator 2201, a second weighted calculator 2202, a third adder 2203, a fourth adder 2204, and a third coordinate inverse transformer 2205. The third coordinate inverse transformer 2205 (such as a Clark transformer) is used to convert the original three-phase voltage ( u a , u b , u c ) converted to voltage components in a two-phase stationary coordinate system ( u α , u β The first weighted calculator 2201 (i.e., the first input terminal of the arithmetic unit 220) receives the voltage components in the two-phase stationary coordinate system output by the coordinate synthesis unit 211. u α , u β ), using weighting coefficients k Perform weighted calculations to generate the corresponding first weighted voltage ( k u α ) and second weighted voltage ( k u β The second weighted calculator 2202 (i.e., the second input terminal of the arithmetic unit 220) receives the grid voltage fundamental frequency filtered component in the two-phase stationary coordinate system output by the fundamental frequency extraction module 21. u α_filter , u β_filter ), using weighting coefficient 1- k Perform weighted calculations to generate the corresponding third weighted voltage (1- k ) u α_filter and the fourth weighted voltage (1- k ) u β_filter The third adder 2203 will convert the first weighted voltage generated by the first weighted calculator 2201 into a single weighted voltage. k u α ) and the third weighted voltage (1-) generated by the second weighted calculator 2202 k ) u α_filter The first mixed feedforward signal is generated by summing the signals. uα_FeedForward The fourth adder 2204 will add the second weighted voltage generated by the first weighted calculator 2201. k u β ) and the fourth weighted voltage (1-) generated by the second weighted calculator 2202 k ) u β_filter The second mixed feedforward signal is generated by summing the signals. u β_FeedForward ).

[0093] That is, the arithmetic unit 220 calculates and generates the hybrid feedforward signal in a two-phase stationary coordinate system using the following formula: u α _ FeedForward = k u α + (1 - k ) u α _ filter u β _ FeedForward = k u β + (1 - k ) u β _ filter The arithmetic unit 220 uses an adjustable weighting coefficient. k It flexibly allocates the contributions of the original voltage signal (containing all dynamic information) and the pure fundamental frequency signal in the feedforward channel, thereby providing the possibility of achieving a trade-off between stability and dynamic performance.

[0094] In some embodiments, the current control module 23 includes: The closed-loop adjustment unit 230 is used to perform closed-loop adjustment of the output grid-connected current signal in a rotating coordinate system that is synchronized with the grid voltage, based on the phase-locked angle output by the base frequency separation unit 210. The coordinate inverse transformation unit 231 is used to inversely transform the adjusted signal to the stationary coordinate system to generate a current closed-loop control signal.

[0095] Specifically, the input terminal of the current control module 23 is used to receive the three-phase output grid-connected current signal of the grid-connected converter 30. i2a , i 2b , i 2c Simultaneously, it receives the phase-locked angle from the baseband extraction module 21. θ This enables closed-loop control of the grid-connected current, allowing it to quickly and accurately track the given current command.

[0096] In one specific embodiment, the closed-loop control unit 230 includes a fourth coordinate inverse transformer 2300, a first comparator 2301, a second comparator 2302, a first proportional-integral (PI) controller 2303, and a second PI controller 2304. Figure 7 As shown, the fourth coordinate inverse transformer 2300 (Park transform) is based on the phase-locked angle. θ The three-phase current ( i 2a , i 2b , i 2c Transform to a rotating coordinate system dq (coordinate system), to obtain the current feedback component ( i 2d , i 2q Subsequently, the first comparator 2301 feeds back the current component ( i 2d ) and the given current reference value ( I 2d_ref The comparison is performed, and the comparison result is input to the first PI controller 2303. The first PI controller 2303 adjusts the error signal according to the comparison result to generate a voltage control signal in the rotating coordinate system. u id The second comparator 2302 will feed back the current component (). i 2q ) and the given current reference value ( I 2q_ref The comparison is performed, and the comparison result is input to the second PI controller 2304. The second PI controller 2304 adjusts the error signal according to the comparison result to generate a voltage control signal in the rotating coordinate system. u iq The coordinate inverse transformation unit 231 (e.g., Park) is based on the phase-locked angle. θ The voltage control signal in the rotating coordinate system ( u id , u iq The inverse transformation back to the two-phase stationary coordinate system outputs a closed-loop control signal for the current. u iα , uiβ ).

[0097] The current control module 23 uses PI control in a rotating coordinate system to achieve zero steady-state error tracking of AC current and achieves synchronization of coordinate transformation through phase-locked angle to ensure control accuracy.

[0098] The modulation signal generation module 24 includes two input terminals: the first input terminal is connected to the output terminal of the weighted feedforward synthesis module 22, and receives the mixed feedforward signal ( u α _ FeedForward , u β _ FeedForward The second input terminal is connected to the output terminal of the current control module 23 to receive the current closed-loop control signal. u iα , u iβ The mixed feedforward signal is combined with the closed-loop control signal to generate the modulation signal that ultimately drives the power device.

[0099] In one specific embodiment, the modulation signal generation module 24 internally includes a fifth adder 241 and a sixth adder 242. The fifth adder 241 is used to convert the received mixed feedforward signal output by the weighted feedforward synthesis module 22 into a single signal. u α _ FeedForward ) and the current closed-loop control signal output by the current control module 23 ( u iα ), and then perform addition to generate a modulated signal ( u cα The sixth adder 242 is used to combine the received weighted feedforward synthesis module 22 output another mixed feedforward signal (). u β _ FeedForward ) and another current closed-loop control signal output by current control module 23 ( u iβ ), and then add them together to generate another modulated signal ( u cβ ).

[0100] That is, the modulation signal generation module 24 calculates the final two-phase stationary coordinate system modulation voltage signal using the following formula: u cα = u iα + u α _ FeedForward u cβ =u iβ + u β _ FeedForward In one specific embodiment, the voltage feedforward control circuit 20 further includes a space vector pulse width modulation (SVPWM) unit 25, used to receive a two-phase stationary coordinate system modulated voltage signal generated by the modulation signal generation module 24. u cα , u cβ The voltage feedforward control circuit 20 generates a pulse sequence with a specific duty cycle, which is the switching signal that drives the power switching devices (such as IGBTs) in the grid-connected converter 30 to turn on and off. The voltage feedforward control circuit 20 combines fast disturbance compensation with precise tracking control in a closed loop. It converts the continuous control voltage signal into discrete switching actions through SVPWM, thereby controlling the converter output to achieve the desired voltage and current.

[0101] In some embodiments, the baseband separation unit 210 is a decoupled double synchronous reference frame (DDSRF-PLL).

[0102] Specifically, the DDSRF-PLL is a phase-locked loop structure containing two parallel Synchronous Reference Frames (SRFs), one locking the positive-sequence component and the other locking the negative-sequence component. Through an internal decoupling network, mutual interference between the positive and negative-sequence components can be effectively eliminated. Each SRF channel is followed by a low-pass filter to extract the corresponding positive-sequence or negative-sequence fundamental frequency DC component. Ultimately, the DDSRF-PLL can simultaneously output high-precision phase-locked angles. θ Fundamental frequency positive sequence component ( u dp_filter , u qp_filter ) and fundamental frequency negative sequence voltage component ( u dn_filter , u qn_filter ).

[0103] Please see Figure 8 This is a schematic diagram of the implementation structure of the baseband separation unit provided in the embodiments of this application.

[0104] Figure 8 Detailed illustration Figure 7 One specific implementation structure of the intermediate frequency separation unit 210 is to use a decoupled dual-synchronous reference coordinate system phase-locked loop. For example... Figure 8As shown, in one specific embodiment, the baseband separation unit 210 includes a positive-sequence synchronous rotating coordinate system transformation subunit (positive-sequence SRF) 2101, a negative-sequence synchronous rotating coordinate system transformation subunit (negative-sequence SRF) 2102, a positive-sequence channel decoupling calculation subunit 2103, a negative-sequence channel decoupling calculation subunit 2104, a positive-sequence low-pass filter (LPF) subunit 2105, a negative-sequence low-pass filter (LPF) subunit 2106, and a third PI controller 2107.

[0105] The positive sequence SRF 2101 is used to convert the input three-phase stationary coordinate system voltage signal ( u a , u b , u c Transform to a positive-sequence synchronous rotating coordinate system. dq + Coordinate system), output positive sequence signal ( v d+ , v q+ The negative-sequence SRF 2102 is used to convert the input three-phase stationary coordinate system voltage signal ( u a , u b , u c Transform to a negative-sequence synchronous rotating coordinate system. dq - Coordinate system), output negative sequence signal ( v d- , v q- Typically, the rotation direction of the negative-sequence SRF 2102 is opposite to that of the positive-sequence SRF 2101.

[0106] Before entering their respective low-pass filters, the outputs of the positive-sequence SRF 2101 ( v d+ , v q+ This will be added to or subtracted from a compensation term (decoupling term) from the negative-order channel decoupling computation subunit 2104. Similarly, the output of the negative-order SRF 2102 ( v d- , v q- It will also be calculated with a compensation term from the positive sequence channel decoupling calculation subunit 2103. These compensation terms are calculated based on the DC component (DC(-) or DC(+)) output from the other channel after low-pass filtering.

[0107] The positive-sequence channel signal after the above decoupling injection is fed into the positive-sequence LPF 2105 for filtering, extracting its fundamental frequency DC component, and the output is the fundamental frequency positive-sequence voltage component. u dp_filter , u qp_filter Similarly, the negative-sequence channel signal after decoupling injection is fed into a negative-sequence LPF 2106 for filtering, extracting its fundamental frequency DC component, and outputting the fundamental frequency negative-sequence voltage component. u dn_filter , u qn_filter ).

[0108] Positive-sequence LPF 2105 and negative-sequence LPF 2106 are respectively located at the output terminals of positive-sequence channel decoupling calculation subunit 2103 and negative-sequence channel decoupling calculation subunit 2104. In a rotating coordinate system, the positive-sequence component of the fundamental frequency is represented as a DC quantity, and the negative-sequence component of the fundamental frequency is also represented as a DC quantity (or a specific low-frequency AC quantity), while harmonics are represented as high-frequency quantities. Positive-sequence LPF 2105 and negative-sequence LPF 2106 are used to filter out these high-frequency harmonic components, thereby outputting a pure fundamental frequency positive-sequence DC voltage component. v d+ , v q+ ) and fundamental frequency negative sequence DC voltage component ( v d- , v q- ).

[0109] The fundamental positive sequence component of the positive sequence LPF 2105 output of the positive sequence channel ( u dp_filter , u qp_filter The decoupled calculation subunit 2104, which is fed back to the negative sequence channel, is used to calculate the compensation terms that need to be injected into the coordinate transformation output of the negative sequence SRF 2102.

[0110] The fundamental frequency negative sequence component output by the negative sequence LPF 2106 in the negative sequence channel ( u dn_filter , u qn_filter The decoupled calculation unit 2103, which is fed back to the positive sequence channel, is used to calculate the compensation terms that need to be injected into the coordinate transformation output of the positive sequence SRF 2102.

[0111] The positive sequence LPF 2105 output of the positive sequence channel q Axial components u qp_filterThe signal is fed into the third PI controller 2107. This third PI controller 2107, by adjusting the output angular frequency, forces the positive-sequence LPF output of the positive-sequence channel to... u qp_filter The angular frequency approaches zero, thus achieving precise phase-locked loop. The integrator integrates the angular frequency of the PI output to obtain the final phase-locked angle. θ The phase-locked angle θ On one hand, it serves as the output, and on the other hand, it is fed back to the positive-sequence SRF 2101 and the negative-sequence SRF 2102 for coordinate transformation, forming a closed-loop phase-locked loop.

[0112] The DDSRF-PLL, through the aforementioned cross-feedback decoupling network, utilizes the extracted DC information of one sequence component in real time to counteract the cross-coupling effect present in another sequence component conversion channel. This structure enables it to simultaneously, independently, and accurately extract pure fundamental positive-sequence and negative-sequence components even when the grid voltage is unbalanced. u dp_filter , u qp_filter )and( u dn_filter , u qn_filter ), and precise phase-locked angle θ .

[0113] This application also provides a grid-connected converter; please refer to [link to relevant documentation]. Figure 9 The grid-connected converter 90 includes a power conversion circuit 91 and a voltage feedforward control device 92 as described in any of the above embodiments. The voltage feedforward control device 92 is used to generate a modulation signal to drive the power conversion circuit 91.

[0114] For example, the power conversion circuit 91 is a three-phase full-bridge circuit composed of power switching devices such as IGBTs and MOSFETs. The signal acquisition module of the voltage feedforward control device 92 is connected to the voltage and current sensors at the grid connection point to acquire the grid voltage and output current signals. The modulation signal output from its modulation signal generation module is connected to the drive terminals of each power switching device in the power conversion circuit 91 to generate PWM waves that drive these switches to turn on and off, thereby controlling the AC side output voltage and current of the converter. The grid-connected converter 90 integrates the voltage feedforward control device 92 of this application; therefore, its operation fully follows the control logic described in the foregoing method and device embodiments, and will not be elaborated further here.

[0115] By employing the voltage feedforward control device 92 of this application, the grid-connected converter 90 can effectively weaken the positive feedback effect brought by the feedforward channel in complex grid environments, especially under weak grid conditions, by adjusting the weighting coefficient, thereby significantly improving the phase margin of the system and ensuring its stable operation even when the grid impedance is high, thus broadening the grid adaptability range of the converter. When encountering sudden changes in grid voltage (such as phase angle jumps during fault ride-through), the original voltage component retained in the feedforward quantity ( k >0) It can provide timely disturbance compensation, making the dynamic response of the converter output current rapid and the overshoot small, which greatly reduces the risk of instantaneous overcurrent and protection shutdown caused by slow response. At the same time, throughout the operation, this hybrid feedforward structure maintains the ability to suppress background harmonic voltage of the grid, which helps to control the harmonic distortion level of the grid-connected current and improve power quality.

[0116] Therefore, the grid-connected converter 90 integrating the voltage feedforward control device 92 solves the technical problem that traditional solutions cannot simultaneously address the stability, dynamic performance, and harmonic immunity of weak grids, and is suitable for application scenarios such as wind power, photovoltaic inverters, and energy storage converters (PCS) that have high requirements for grid adaptability.

[0117] This application also provides an electronic device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the voltage feedforward control method described in any of the above embodiments.

[0118] When the electronic device is running, the processor executes a series of steps according to the stored program instructions, including signal acquisition, coordinate transformation, fundamental frequency extraction, weighted fusion calculation, PI adjustment, and PWM generation, to fully implement the feedforward control method described in this application. The resulting technical effects are the same as those achieved by the aforementioned methods, devices, and grid-connected converter embodiments, and will not be elaborated upon here.

[0119] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the voltage feedforward control method described in any of the above embodiments.

[0120] In the embodiments of this application, the storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM), etc.

[0121] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0122] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0123] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0124] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0125] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0126] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0127] Computer-readable media include both permanent and non-permanent, removable and non-removable media, which can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient media, such as modulated communication signals and carrier waves.

[0128] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0129] The above provides a detailed description of a voltage feedforward control method, apparatus, grid-connected converter, device, and computer-readable storage medium provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A voltage feedforward control method, characterized by, include: Based on the voltage signal at the common coupling point of the grid-connected converter, the fundamental frequency component of the voltage signal is extracted; Based on preset weighting coefficients, the original component of the voltage signal is fused with the fundamental frequency component to generate a hybrid feedforward signal; A current closed-loop control signal is generated based on the output grid-connected current signal of the grid-connected converter. Based on the current closed-loop control signal and the hybrid feedforward signal, a modulation signal for controlling the grid-connected converter is generated.

2. The method according to claim 1, characterized in that, The weighting coefficients are determined based on at least one of the following performance requirements of the grid-connected converter under weak grid conditions: stability, dynamic response performance, and grid voltage harmonic suppression capability.

3. The method according to claim 2, characterized in that, The weighting coefficient shall be no less than the larger of the minimum value determined to meet the dynamic response performance requirements of the grid-connected converter and the minimum value determined to meet the grid voltage harmonic suppression capability requirements, and shall not exceed the maximum allowable value determined to meet the weak grid stability requirements.

4. The method according to claim 1, characterized in that, The step of extracting the fundamental frequency component of the voltage signal based on the common coupling point of the grid-connected converter includes: The voltage signal is subjected to fundamental frequency separation processing to obtain the phase-locked angle and the positive-sequence component and negative-sequence component of the fundamental frequency; The fundamental frequency positive sequence component and the fundamental frequency negative sequence component are combined by coordinate synthesis to obtain the fundamental frequency component of the voltage signal.

5. The method according to claim 4, characterized in that, The step of performing fundamental frequency separation processing on the voltage signal to obtain the phase-locked angle and the positive-sequence and negative-sequence components of the fundamental frequency includes: The voltage signal is subjected to phase-locked loop and positive / negative sequence decoupling processing, and the decoupled components are filtered to obtain the fundamental frequency positive sequence component and the fundamental frequency negative sequence component.

6. The method according to claim 4, characterized in that, The step of performing coordinate synthesis of the fundamental frequency positive-sequence component and the fundamental frequency negative-sequence component to obtain the fundamental frequency component of the voltage signal includes: The fundamental frequency positive sequence component and the fundamental frequency negative sequence component are respectively transformed to two-phase stationary coordinate systems by inverse coordinate transformation and then added together to obtain the fundamental frequency component of the voltage signal.

7. The method according to claim 4, characterized in that, The step of fusing the original component of the voltage signal with the fundamental frequency component based on preset weighting coefficients to generate a hybrid feedforward signal includes: The hybrid feedforward signal is obtained by adding the product of the original component and the weighting coefficient, and the product of the fundamental frequency component and a compensation coefficient; wherein the sum of the compensation coefficient and the weighting coefficient is 1.

8. The method according to claim 4, characterized in that, The step of generating a current closed-loop control signal based on the output grid-connected current signal of the grid-connected converter includes: Based on the phase-locked angle, the output grid-connected current signal is subjected to closed-loop adjustment in a rotating coordinate system synchronized with the grid voltage, and the adjusted signal is inversely transformed to a stationary coordinate system to generate the current closed-loop control signal.

9. A voltage feedforward control device, characterized in that, include: The fundamental frequency extraction module is used to receive the voltage signal at the common coupling point of the grid-connected converter and extract the fundamental frequency component of the voltage signal. The weighted feedforward synthesis module is used to receive the original component of the voltage signal and the fundamental frequency component output by the fundamental frequency extraction module, and to fuse the original component and the fundamental frequency component based on a preset weighting coefficient to generate a hybrid feedforward signal. The current control module is used to receive the output grid-connected current signal of the grid-connected converter and generate a current closed-loop control signal. The modulation signal generation module is used to receive the hybrid feedforward signal output by the weighted feedforward synthesis module and the current closed-loop control signal output by the current control module, and generate a modulation signal for controlling the grid-connected converter based on the current closed-loop control signal and the hybrid feedforward signal.

10. The apparatus according to claim 9, characterized in that, The fundamental frequency extraction module includes: The fundamental frequency separation unit is used to receive the voltage signal, perform fundamental frequency separation processing on the voltage signal, and output the phase-locked angle and the positive-sequence component and the negative-sequence component of the fundamental frequency. The coordinate synthesis unit is used to receive the positive-sequence component and the negative-sequence component of the fundamental frequency output by the fundamental frequency separation unit, and to perform coordinate synthesis processing on the positive-sequence component and the negative-sequence component of the fundamental frequency to output the fundamental frequency component of the voltage signal.

11. The apparatus according to claim 10, characterized in that, The fundamental frequency separation unit is a phase-locked loop for decoupling dual synchronous reference coordinate systems.

12. The apparatus according to claim 10, characterized in that, The coordinate synthesis unit is used to perform inverse coordinate transformation on the fundamental frequency positive sequence component and the fundamental frequency negative sequence component respectively to a two-phase stationary coordinate system, and then add them together to output the fundamental frequency component of the voltage signal.

13. The apparatus according to claim 9, characterized in that, The weighted feedforward synthesis module includes a computation unit for adding the product of the original component and the weighting coefficient, and the product of the fundamental frequency component and a compensation coefficient, to obtain the hybrid feedforward signal; wherein the sum of the compensation coefficient and the weighting coefficient is 1.

14. The apparatus according to claim 10, characterized in that, The current control module includes: A closed-loop adjustment unit is used to perform closed-loop adjustment of the output grid-connected current signal in a rotating coordinate system that is synchronized with the grid voltage, based on the phase-locked angle output by the base frequency separation unit. The coordinate inverse transformation unit is used to inversely transform the adjusted signal to the stationary coordinate system to generate the current closed-loop control signal.

15. A grid-connected converter, characterized in that, It includes a power conversion circuit and a voltage feedforward control device as described in any one of claims 9 to 14, the voltage feedforward control device being used to generate a modulation signal to drive the power conversion circuit.

16. An electronic device, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the method as described in any one of claims 1 to 8.

17. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the method as described in any one of claims 1 to 8.

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