Methods, devices, and equipment for grid impedance detection and power quality optimization of grid-connected inverters

Abstract

This application relates to a method, apparatus, and device for grid impedance detection and power quality optimization in a grid-connected inverter. The method includes: performing a first impedance estimation of the grid based on background harmonics at the grid connection point to obtain an impedance estimate; obtaining a disturbance amplitude parameter based on the impedance estimate, which is negatively correlated with the impedance estimate; when the disturbance amplitude parameter is zero, performing a first impedance estimation based on the background harmonics to obtain an updated impedance estimate; when the disturbance amplitude parameter is not zero, controlling the inverter to inject a disturbance signal into the grid based on the disturbance amplitude parameter; after injection, performing a second impedance estimation of the grid based on current data, voltage data, and disturbance frequency at the grid connection point to obtain a second impedance estimate; and returning to the step of obtaining the disturbance amplitude parameter based on the updated impedance estimate. This method enables high-precision detection of grid impedance while ensuring system stability.

Description

Technical Field

[0001] This application relates to the field of power technology, and in particular to a method, apparatus, computer equipment, computer-readable storage medium, and computer program product for grid impedance detection and power quality optimization of a grid-connected inverter. Background Technology

[0002] With the increasing proportion of renewable energy, grid-connected inverters are gradually gaining widespread application due to their excellent voltage support capabilities in weak grid environments. Grid-connected inverters typically require stability control and adaptive parameter tuning based on grid strength. Grid impedance, as a crucial indicator of grid strength, is critical to the operational stability of grid-connected inverters. Related technologies typically employ passive or active methods for grid impedance detection. However, the accuracy of passive impedance detection is easily affected by background harmonics, while active methods can negatively impact the power quality of the inverter's output, making it difficult to achieve high-precision grid impedance detection while ensuring system stability. Summary of the Invention

[0003] Therefore, it is necessary to provide a method, apparatus, computer equipment, computer-readable storage medium, and computer program product for grid impedance detection and power quality optimization of grid-connected inverters to address the aforementioned technical problems.

[0004] Firstly, this application provides a method for grid impedance detection and power quality optimization of a grid-connected inverter, including:

[0005] The first impedance estimate of the power grid is obtained by performing a first impedance estimate on the power grid based on the background harmonics at the grid connection point;

[0006] Based on the impedance estimate, the disturbance amplitude parameter for injecting disturbance into the power grid is obtained; wherein, the disturbance amplitude parameter is negatively correlated with the impedance estimate;

[0007] When the disturbance amplitude parameter is zero, the first impedance estimate of the power grid is performed based on the background harmonics at the grid connection point to obtain the updated impedance estimate of the power grid.

[0008] If the disturbance amplitude parameter is not zero, the inverter is controlled to inject a disturbance signal into the power grid according to the disturbance amplitude parameter.

[0009] After the disturbance signal is injected, a second impedance estimate is performed on the power grid based on the current and voltage data of the grid connection point and the disturbance frequency of the disturbance signal to obtain an updated impedance estimate of the power grid.

[0010] Based on the updated impedance estimate, the process returns to the step of obtaining the disturbance amplitude parameters for disturbance injection into the power grid based on the impedance estimate, until a preset stop condition is met.

[0011] In one embodiment, the step of performing a second impedance estimation on the power grid based on the current and voltage data at the grid connection point and the disturbance frequency of the disturbance signal to obtain an updated impedance estimate of the power grid includes: processing the current and voltage data using the Geitzer algorithm to calculate the imaginary part of the current, the real part of the current, the imaginary part of the voltage, and the real part of the voltage at the disturbance frequency; obtaining the resistive component and the inductive reactance component of the power grid based on the imaginary part of the current, the real part of the current, the imaginary part of the voltage, and the real part of the voltage at the disturbance frequency; and obtaining the updated impedance estimate of the power grid based on the resistive component and the inductive reactance component.

[0012] In one embodiment, obtaining the disturbance amplitude parameter for injecting disturbance into the power grid based on the impedance estimate includes: obtaining the short-circuit ratio of the power grid based on the impedance estimate, the rated capacity of the inverter, and the rated voltage of the grid connection point; determining the disturbance amplitude parameter to be zero when the short-circuit ratio is not greater than a first threshold; obtaining the disturbance amplitude parameter corresponding to the short-circuit ratio based on a preset mapping relationship between the short-circuit ratio and the disturbance amplitude parameter when the short-circuit ratio is greater than the first threshold and less than a second threshold; the disturbance amplitude parameter is greater than zero and less than a preset upper limit of the disturbance amplitude parameter; and determining the disturbance amplitude parameter to be the upper limit of the disturbance amplitude parameter when the short-circuit ratio is not less than the second threshold.

[0013] In one embodiment, after obtaining the updated impedance estimate of the power grid, the method further includes: adjusting the control parameters of the inverter based on the updated impedance estimate.

[0014] In one embodiment, the control parameters include virtual impedance, harmonic compensation coefficient, and reactive power droop coefficient; wherein the virtual impedance is positively correlated with the impedance estimate, the harmonic compensation coefficient is positively correlated with the impedance estimate, and the reactive power droop coefficient is positively correlated with the impedance estimate.

[0015] In one embodiment, the perturbation frequency is 75 Hz.

[0016] Secondly, this application also provides a grid impedance detection and power quality optimization device for a grid-connected inverter, comprising:

[0017] The first estimation module is used to perform a first impedance estimation on the power grid based on the background harmonics at the grid connection point, and obtain the impedance estimate of the power grid.

[0018] The first acquisition module is used to obtain the disturbance amplitude parameter for injecting disturbance into the power grid based on the impedance estimate; wherein the disturbance amplitude parameter is negatively correlated with the impedance estimate;

[0019] The second estimation module is used to perform a first impedance estimation of the power grid based on the background harmonics at the grid connection point when the disturbance amplitude parameter is zero, so as to obtain the updated impedance estimate of the power grid.

[0020] The disturbance injection module is used to control the inverter to inject a disturbance signal into the power grid according to the disturbance amplitude parameter when the disturbance amplitude parameter is not zero.

[0021] The third estimation module is used to perform a second impedance estimation on the power grid based on the current and voltage data of the grid connection point and the disturbance frequency of the disturbance signal after the disturbance signal is injected, so as to obtain an updated impedance estimate of the power grid.

[0022] The second acquisition module is used to return the step of obtaining the disturbance amplitude parameter for disturbance injection into the power grid based on the updated impedance estimate, until a preset stop condition is met.

[0023] Thirdly, this application also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to perform the following steps:

[0024] The first impedance estimate of the power grid is obtained by performing a first impedance estimate on the power grid based on the background harmonics at the grid connection point;

[0025] Based on the impedance estimate, the disturbance amplitude parameter for injecting disturbance into the power grid is obtained; wherein, the disturbance amplitude parameter is negatively correlated with the impedance estimate;

[0026] When the disturbance amplitude parameter is zero, the first impedance estimate of the power grid is performed based on the background harmonics at the grid connection point to obtain the updated impedance estimate of the power grid.

[0027] If the disturbance amplitude parameter is not zero, the inverter is controlled to inject a disturbance signal into the power grid according to the disturbance amplitude parameter.

[0028] After the disturbance signal is injected, a second impedance estimate is performed on the power grid based on the current and voltage data of the grid connection point and the disturbance frequency of the disturbance signal to obtain an updated impedance estimate of the power grid.

[0029] Based on the updated impedance estimate, the process returns to the step of obtaining the disturbance amplitude parameters for disturbance injection into the power grid based on the impedance estimate, until a preset stop condition is met.

[0030] Fourthly, this application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the following steps:

[0031] The first impedance estimate of the power grid is obtained by performing a first impedance estimate on the power grid based on the background harmonics at the grid connection point;

[0032] Based on the impedance estimate, the disturbance amplitude parameter for injecting disturbance into the power grid is obtained; wherein, the disturbance amplitude parameter is negatively correlated with the impedance estimate;

[0033] When the disturbance amplitude parameter is zero, the first impedance estimate of the power grid is performed based on the background harmonics at the grid connection point to obtain the updated impedance estimate of the power grid.

[0034] If the disturbance amplitude parameter is not zero, the inverter is controlled to inject a disturbance signal into the power grid according to the disturbance amplitude parameter.

[0035] After the disturbance signal is injected, a second impedance estimate is performed on the power grid based on the current and voltage data of the grid connection point and the disturbance frequency of the disturbance signal to obtain an updated impedance estimate of the power grid.

[0036] Based on the updated impedance estimate, the process returns to the step of obtaining the disturbance amplitude parameters for disturbance injection into the power grid based on the impedance estimate, until a preset stop condition is met.

[0037] Fifthly, this application also provides a computer program product, including a computer program that, when executed by a processor, performs the following steps:

[0038] The first impedance estimate of the power grid is obtained by performing a first impedance estimate on the power grid based on the background harmonics at the grid connection point;

[0039] Based on the impedance estimate, the disturbance amplitude parameter for injecting disturbance into the power grid is obtained; wherein, the disturbance amplitude parameter is negatively correlated with the impedance estimate;

[0040] When the disturbance amplitude parameter is zero, the first impedance estimate of the power grid is performed based on the background harmonics at the grid connection point to obtain the updated impedance estimate of the power grid.

[0041] If the disturbance amplitude parameter is not zero, the inverter is controlled to inject a disturbance signal into the power grid according to the disturbance amplitude parameter.

[0042] After the disturbance signal is injected, a second impedance estimate is performed on the power grid based on the current and voltage data of the grid connection point and the disturbance frequency of the disturbance signal to obtain an updated impedance estimate of the power grid.

[0043] Based on the updated impedance estimate, the process returns to the step of obtaining the disturbance amplitude parameters for disturbance injection into the power grid based on the impedance estimate, until a preset stop condition is met.

[0044] The aforementioned grid impedance detection and power quality optimization method, apparatus, computer equipment, computer-readable storage medium, and computer program product for grid-connected inverters first perform a first impedance estimation of the grid based on the background harmonics at the grid connection point to obtain an impedance estimate of the grid. Then, based on this impedance estimate, a disturbance amplitude parameter for injecting disturbance into the grid is obtained. This disturbance amplitude parameter is negatively correlated with the impedance estimate. Specifically, when the disturbance amplitude parameter is zero, a first impedance estimation is performed on the grid based on the background harmonics at the grid connection point to obtain an updated impedance estimate of the grid. When the disturbance amplitude parameter is not zero, the inverter is controlled to inject a disturbance signal into the grid based on the disturbance amplitude parameter. After the disturbance signal is injected, current and voltage data at the grid connection point are collected. Then, based on the current data, voltage data, and the disturbance frequency of the disturbance signal, a second impedance estimation is performed on the grid to obtain an updated impedance estimate of the grid. Finally, based on the updated impedance estimate, the process returns to obtaining the disturbance amplitude parameter for injecting disturbance into the grid based on the impedance estimate, until a preset stop condition is met. This scheme first estimates the grid impedance based on the background harmonics at the grid connection point to obtain its impedance estimate. Then, based on the impedance estimate, it obtains the disturbance amplitude parameter for injecting disturbances into the grid. Based on the impedance estimate, it can dynamically adjust the magnitude of the injected harmonics. By making the disturbance amplitude parameter negatively correlated with the impedance estimate, it can use a larger disturbance magnitude under strong grid conditions to ensure the detection signal-to-noise ratio. Under weak grid conditions, it automatically reduces the disturbance amplitude to avoid excitation power oscillation. Under extremely weak grid conditions, it switches to a passive observation mode for impedance detection based on background harmonics. It can achieve disturbance intensity adjustment based on grid strength self-adaptation. This avoids the limitations on impedance detection accuracy caused by weak background harmonics and avoids the instability of grid-connected inverters in weak grid environments. It can achieve high-precision detection of grid impedance while ensuring the stability of the system's power quality. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a flowchart illustrating a grid impedance detection and power quality optimization method for a grid-connected inverter in one embodiment.

[0047] Figure 2 This is a schematic diagram of the process for obtaining the updated impedance estimate in one embodiment;

[0048] Figure 3 This is a schematic diagram of the impedance extraction simulation results in one embodiment;

[0049] Figure 4 The current spectrum diagram of the inverter output current before and after the injection of a disturbance current signal in one embodiment;

[0050] Figure 5 This is a schematic diagram illustrating the application environment of a grid impedance detection and power quality optimization method for a grid-connected inverter in one embodiment.

[0051] Figure 6 This is a schematic diagram of the decision logic for the disturbance amplitude parameter in one embodiment;

[0052] Figure 7 This is a schematic diagram of the processing procedure of the power coordination control module in one embodiment;

[0053] Figure 8 This is a structural block diagram of a grid impedance detection and power quality optimization device for a grid-connected inverter in one embodiment.

[0054] Figure 9 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0056] It should be noted that the terms "first," "second," etc., used in this application can be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from the second element. The terms "comprising" and "having," and any variations thereof, used in this application, are intended to cover non-exclusive inclusion. The term "multiple" used in this application refers to two or more. The term "and / or" used in this application refers to one of the embodiments, or any combination of multiple embodiments.

[0057] In one embodiment, such as Figure 1As shown, a method for grid impedance detection and power quality optimization of a grid-connected inverter is provided. This embodiment illustrates the application of this method to a terminal. It is understood that this method can also be applied to a server, and further to a system including both a terminal and a server, and implemented through interaction between the terminal and the server. Exemplarily, the terminal can be a digital controller. In this embodiment, the method includes the following steps:

[0058] Step S101: Perform a first impedance estimation on the power grid based on the background harmonics at the grid connection point to obtain the impedance estimate of the power grid.

[0059] When starting impedance detection, the background harmonics at the inverter's grid connection point can be used to perform a first impedance estimation of the power grid, thereby obtaining an estimated impedance value for the power grid. This first impedance estimation can be a passive impedance detection method.

[0060] For example, the terminal can be connected to a voltage and current sampling unit, which can control the voltage and current sampling unit to sample the current and voltage at the point of common coupling (PCC) to obtain the current and voltage data of the PCC. Then, the components corresponding to the background harmonics can be extracted from the data, and the impedance estimate of the power grid can be calculated by the least squares method.

[0061] Step S102: Based on the impedance estimate, obtain the disturbance amplitude parameters for the disturbance injection into the power grid; wherein, the disturbance amplitude parameters are negatively correlated with the impedance estimate.

[0062] The Short-Circuit Ratio (SCR) is a crucial indicator for measuring the relationship between short-circuit capacity and equipment capacity in a power system. When using fixed equipment (e.g., fixed transformers), a higher grid impedance results in a lower SCR, indicating a weaker grid. Therefore, the estimated grid impedance directly reflects the grid's strength. Based on this, this step can derive the disturbance amplitude parameter for grid disturbance injection based on the impedance estimate. Grid disturbance injection can refer to injecting a disturbance signal of a specific frequency into the grid via an inverter. The disturbance amplitude parameter can be used to control the amplitude of the disturbance signal output by the inverter. For example, the disturbance amplitude parameter can directly indicate the amplitude of the disturbance signal or it can be an amplitude coefficient used to adjust the rated amplitude of the signal.

[0063] For example, the terminal may be pre-configured with a mapping relationship between the grid impedance amplitude and the disturbance amplitude parameter. In this step, the corresponding disturbance amplitude parameter can be obtained by mapping based on the impedance estimate. For example, the configuration form of this mapping relationship may include, but is not limited to, mapping tables, mapping functions, etc. For example, when the impedance estimate is sufficiently large (e.g., greater than a preset threshold), the parameter value of the disturbance amplitude parameter can be determined to be zero.

[0064] When the value of the disturbance amplitude parameter is zero, the process can proceed to step S103; when the value of the disturbance amplitude parameter is not zero, the process can proceed to step S104.

[0065] Step S103: When the disturbance amplitude parameter is zero, perform a first impedance estimation on the power grid based on the background harmonics at the grid connection point to obtain the updated impedance estimate of the power grid.

[0066] In this case, when the disturbance amplitude parameter is zero, there is no need to inject a disturbance signal into the grid. The background harmonics at the grid connection point can be used directly to perform the first impedance estimation through a passive impedance detection method to obtain the updated impedance estimate.

[0067] Step S104: When the disturbance amplitude parameter is not zero, control the inverter to inject a disturbance signal into the grid according to the disturbance amplitude parameter.

[0068] When the disturbance amplitude parameter is not zero, the terminal can obtain the amplitude of the disturbance signal based on the disturbance amplitude parameter. For example, the disturbance signal can be a current signal of a specific frequency, such as an interharmonic signal of a preset frequency. For example, when the disturbance amplitude parameter directly indicates the amplitude of the disturbance signal, the terminal can directly obtain the amplitude of the disturbance signal based on the disturbance amplitude parameter. When the disturbance amplitude parameter is an amplitude coefficient used to adjust the rated amplitude of the signal, the terminal can multiply the disturbance amplitude parameter by the preset rated amplitude of the disturbance signal to obtain the amplitude of the disturbance signal.

[0069] For example, taking the disturbance signal as a current signal, the terminal can obtain the amplitude of the disturbance signal according to the disturbance amplitude parameter, superimpose it on the current inner loop reference value, and then output it to the current inner loop controller of the inverter. The current inner loop controller can generate the modulation reference value of the pulse width modulation (PWM) modulator according to the current inner loop reference value and the actual current, and drive the inverter to inject the disturbance signal into the grid through the PWM modulator.

[0070] Step S105: After the disturbance signal is injected, a second impedance estimate is performed on the power grid based on the current and voltage data at the grid connection point and the disturbance frequency of the disturbance signal, so as to obtain the updated impedance estimate of the power grid.

[0071] After the disturbance signal is injected, the terminal can control the voltage and current sampling unit to continuously collect the current and voltage of the phase corresponding to the injected disturbance signal at the point of common coupling (PCC) to obtain the current and voltage data of the PCC. For example, the sampling frequency of the current and voltage data can be 10kHz.

[0072] After obtaining the current and voltage data at the grid connection point, the current and voltage components corresponding to the disturbance frequency can be extracted from the current and voltage data based on the disturbance frequency of the disturbance signal. The impedance of the power grid is then calculated based on this, resulting in an updated impedance estimate. For example, the current and voltage components can be extracted using a Fourier transform-based method.

[0073] For example, the current component corresponding to the disturbance frequency may include the real part of the current. and the virtual part The voltage component may include the real part of the voltage. Imaginary part of voltage Based on the current and voltage components, the resistance component of the power grid at the disturbance frequency f can be calculated using the following formula. and resistance components :

[0074]

[0075]

[0076] Considering that the inductive reactance of the power grid is proportional to the frequency, the inductive reactance corresponding to the disturbance frequency f is converted to the 50Hz power frequency inductive reactance:

[0077]

[0078] The power grid resistance component at power frequency Frequency-independent, can be used directly The final 50Hz power frequency impedance was obtained. Amplitude:

[0079]

[0080] Therefore, the amplitude of the power frequency impedance can be used as a basis. This yields the updated impedance estimate.

[0081] Step S106: Based on the updated impedance estimate, return to the step of obtaining the disturbance amplitude parameters for disturbance injection into the power grid based on the impedance estimate, until the preset stop condition is met.

[0082] After obtaining the updated impedance estimate through step S103 or step S105, the process can return to step S102 to obtain a new disturbance amplitude parameter based on the updated impedance estimate. Steps S102 to S106 can be executed cyclically until a preset stop condition is met. For example, the preset stop condition could be receiving an instruction to stop impedance detection, etc.

[0083] In the above-mentioned grid impedance detection and power quality optimization method for grid-connected inverters, the grid impedance is first estimated based on the background harmonics at the grid connection point to obtain its impedance estimate. Then, the disturbance amplitude parameter for injecting disturbances into the grid is obtained based on the impedance estimate. Based on the impedance estimate, the amplitude of the injected harmonics can be dynamically adjusted. By making the disturbance amplitude parameter negatively correlated with the impedance estimate, a larger disturbance amplitude can be used under strong grid conditions to ensure the detection signal-to-noise ratio. Under weak grid conditions, the disturbance amplitude is automatically reduced to avoid excitation power oscillation. Under extremely weak grid conditions, it switches to a passive observation mode for impedance detection based on background harmonics. This enables disturbance intensity adjustment based on grid strength self-adaptation. Thus, it avoids the limitation of impedance detection accuracy when the background harmonics are weak, and it also avoids the instability of grid-connected inverters in weak grid environments. It can achieve high-precision detection of grid impedance while ensuring the stability of the system's power quality.

[0084] In one exemplary embodiment, such as Figure 2 As shown, based on the current and voltage data at the grid connection point and the disturbance frequency of the disturbance signal, a second impedance estimate is performed on the power grid to obtain an updated impedance estimate of the power grid, which may include:

[0085] Step S201: Use the Gertz algorithm to process the current and voltage data, and calculate the imaginary part of the current, the real part of the current, the imaginary part of the voltage, and the real part of the voltage at the disturbance frequency.

[0086] In the second impedance estimation, the Goetzeel algorithm can be used to process the current and voltage data at the grid connection point to extract the circuit components (including the imaginary and real parts of the current) and voltage components (including the imaginary and real parts of the voltage) corresponding to the disturbance frequency. The Goetzeel algorithm is an efficient implementation method of the discrete Fourier transform based on a second-order infinite impulse response filter. Its core idea is to calculate the Fourier coefficients at a specified frequency point recursively. Compared with the traditional fast Fourier transform, it has the advantages of low computational cost, low storage resource consumption, and suitability for embedded real-time processing.

[0087] For example, current data and voltage data can each be a sampling sequence comprising multiple sampling points. For the sampling sequence x(n), the spectral components corresponding to the perturbation frequency can be calculated using the Gertz algorithm as follows:

[0088]

[0089]

[0090]

[0091] In the formula, N is the number of sampling points in the sampling sequence, k is the index corresponding to the perturbation frequency, x[n] is the sampled value of the nth input, and s[n] is the intermediate state variable of the nth step. The real part of the Fourier coefficients corresponding to the perturbation frequency of the sampled data. The sampled data represents the imaginary part of the Fourier coefficients corresponding to the perturbation frequency. During algorithm initialization, s[-1] = s[-2] = 0 can be set.

[0092] Specifically, by performing the aforementioned calculations on the current and voltage data respectively, the real part of the current corresponding to the disturbance frequency can be extracted from the current data. and the imaginary part of the current And extracting the real part of the voltage corresponding to the perturbation frequency from the voltage data. and the imaginary part of voltage .

[0093] Step S202: Based on the imaginary part of the current, the real part of the current, the imaginary part of the voltage, and the real part of the voltage at the disturbance frequency, the resistive component and the inductive reactance component of the power grid are obtained.

[0094] Among them, based on the imaginary part of the current at the disturbance frequency Real part of current Imaginary part of voltage and the real part of the voltage The resistance component of the power grid at the disturbance frequency f can be calculated using the following formula. and resistance components :

[0095]

[0096]

[0097] Considering that the inductive reactance of the power grid is proportional to the frequency, the inductive reactance corresponding to the disturbance frequency f is converted to the 50Hz power frequency inductive reactance: The power grid resistance component at power frequency Frequency-independent, can be used directly Therefore, the resistance component of the power grid at the 50Hz power frequency can be obtained. and resistance components .

[0098] Step S203: Based on the resistive and inductive components, obtain the updated impedance estimate of the power grid.

[0099] Among them, based on the resistance component of the power grid and resistance components It can calculate the 50Hz power frequency impedance of the power grid. Amplitude:

[0100]

[0101] Therefore, the amplitude of the power frequency impedance can be used as a basis. This yields the updated impedance estimate.

[0102] Please refer to the following: Figure 3 The figure shows the simulation results of impedance extraction at a 75Hz disturbance frequency. Using the grid impedance at 50Hz as a reference, after two power frequency cycles of iteration following changes in the actual grid impedance, the calculated impedance value obtained using the Gertz algorithm is close to the actual value. This allows for the calculation of impedance under different grid impedance conditions (different equivalent grid inductance L). g Equivalent resistance R of the power grid g The measurement accuracy requirements are met.

[0103] In this embodiment, by using the Gertz algorithm to extract the current and voltage components at the disturbance frequency, and then calculating the grid impedance based on these components, the computational burden can be reduced while ensuring the accuracy of impedance extraction. This is beneficial for improving the detection efficiency of grid impedance and reducing computational costs.

[0104] In an exemplary embodiment, obtaining the disturbance amplitude parameter for injecting disturbance into the power grid based on impedance estimation may include: obtaining the short-circuit ratio of the power grid based on impedance estimation, the rated capacity of the inverter, and the rated voltage of the grid connection point; determining the disturbance amplitude parameter to be zero when the short-circuit ratio is not greater than a first threshold; obtaining the disturbance amplitude parameter corresponding to the short-circuit ratio based on a preset mapping relationship between the short-circuit ratio and the disturbance amplitude parameter when the short-circuit ratio is greater than the first threshold and less than a second threshold; the disturbance amplitude parameter being greater than zero and less than a preset upper limit of the disturbance amplitude parameter; and determining the disturbance amplitude parameter to be the upper limit of the disturbance amplitude parameter when the short-circuit ratio is not less than the second threshold.

[0105] In this embodiment, the short-circuit ratio of the power grid can be obtained first based on the impedance estimate of the power grid, the rated capacity of the inverter, and the rated voltage of the grid connection point. Then, the corresponding disturbance amplitude parameter can be obtained based on the value of the short-circuit ratio.

[0106] For example, the short-circuit ratio of the power grid can be calculated using the following formula:

[0107]

[0108] In the formula, The short-circuit ratio of the power grid. This refers to the short-circuit capacity of the power grid at the grid connection point. The rated capacity of the inverter. The rated voltage of the grid connection point. To estimate the impedance of the power grid.

[0109] The short-circuit ratio (SCR) is an important indicator for measuring the relationship between short-circuit capacity and equipment capacity in a power system. The smaller the short-circuit ratio, the weaker the power grid. Therefore, the parameter value of the disturbance amplitude can be set to be positively correlated with the short-circuit ratio.

[0110] For example, a first threshold and a second threshold corresponding to the short-circuit ratio can be preset, and the numerical range of the short-circuit ratio can be divided into multiple intervals, including not greater than the first threshold, greater than the first threshold and less than the second threshold, and not less than the second threshold. Each interval can correspond to a different disturbance amplitude parameter value, so that after obtaining the short-circuit ratio of the power grid, the parameter value of the corresponding disturbance amplitude parameter can be obtained based on the interval in which the short-circuit ratio falls.

[0111] Specifically, when the short-circuit ratio is not greater than a first threshold, the value of the disturbance amplitude parameter can be determined to be zero; when the short-circuit ratio is not less than a second threshold, the value of the disturbance amplitude parameter is determined to be a preset upper limit of the disturbance amplitude parameter; and when the short-circuit ratio is greater than the first threshold and less than the second threshold, the disturbance amplitude parameter corresponding to the short-circuit ratio can be obtained according to the preset mapping relationship between the short-circuit ratio and the disturbance amplitude parameter. For example, when the short-circuit ratio is greater than the first threshold and less than the second threshold, the range of the disturbance amplitude parameter value can be greater than zero and less than the upper limit of the disturbance amplitude parameter, and the disturbance amplitude parameter value is positively correlated with the short-circuit ratio. For example, when the short-circuit ratio is greater than the first threshold and less than the second threshold, the preset mapping relationship between the short-circuit ratio and the disturbance amplitude parameter can be expressed as an increasing function, or as a mapping table including multiple short-circuit ratio sub-intervals and the corresponding disturbance amplitude parameter values.

[0112] In this embodiment, by calculating the short-circuit ratio of the power grid based on the impedance estimate, the short-circuit ratio can be used to intuitively reflect the strength characteristics of the power grid. Furthermore, by determining the parameter value of the disturbance amplitude parameter based on the relationship between the short-circuit ratio and the first and second thresholds, a larger disturbance signal can be injected into the power grid under strong power grid conditions based on the upper limit of the disturbance amplitude parameter to ensure the detection signal-to-noise ratio. Under weak power grid conditions, the amplitude of the disturbance signal is dynamically adjusted according to the short-circuit ratio to avoid excitation power oscillation. Under extremely weak power grid conditions, the parameter value of the disturbance amplitude parameter is set to zero, thereby switching to a passive impedance observation mode. This can solve the problem of "instability caused by detection behavior" in grid-connected inverters under weak power grid environments.

[0113] In one exemplary embodiment, after obtaining the updated impedance estimate of the power grid, the method may further include: adjusting the control parameters of the inverter based on the updated impedance estimate.

[0114] The inverter's control parameters can be used to control or regulate the inverter's output characteristics. In this embodiment, after obtaining the updated impedance estimate, the inverter's control parameters can be adjusted based on the impedance estimate to match the power quality of the inverter's output with the current grid operating conditions.

[0115] For example, the control parameters of the inverter may include one or more of the following: virtual impedance, harmonic compensation coefficient, and reactive power droop coefficient. The controller can determine the parameter values ​​of one or more control parameters based on the preset mapping relationship between the grid impedance amplitude and various control parameters, and write the new parameters into the corresponding registers. Through the inner current loop, outer voltage loop, and PWM modulator, these parameters are ultimately applied to the main circuit of the inverter to achieve closed-loop optimization of the output power quality.

[0116] For example, in this embodiment, the optimization process of the inverter's control parameters can be carried out synchronously with impedance detection. Each time a new impedance estimate is obtained, the control parameters are updated to ensure that the inverter always operates in the best control state that matches the current grid conditions.

[0117] In this embodiment, by adjusting the inverter's control parameters based on the updated impedance estimate, a closed-loop collaborative control architecture for impedance detection and power quality optimization can be constructed. The accurately calculated grid impedance value is fed back to the inverter's multi-loop controller in real time, forming a "detection-control" closed loop. Through this collaborative control, the inverter can automatically optimize the output power quality according to the grid strength.

[0118] In an exemplary embodiment, the control parameters include virtual impedance, harmonic compensation coefficient, and reactive power droop coefficient; wherein, virtual impedance is positively correlated with impedance estimate, harmonic compensation coefficient is positively correlated with impedance estimate, and reactive power droop coefficient is positively correlated with impedance estimate.

[0119] The control parameters adjusted based on the updated impedance estimates can include the inverter's virtual impedance, harmonic compensation coefficient, and reactive power droop coefficient. The virtual impedance indicates the analog impedance connected in series in the inverter control loop; increasing the virtual impedance enhances system damping to suppress oscillations caused by active and reactive power coupling in weak grid conditions. The harmonic compensation coefficient indicates the harmonic gain of the proportional resonance; increasing it enhances the suppression of background harmonics at the grid connection point and reduces the total voltage distortion rate. The reactive power droop coefficient is the slope coefficient in droop control; a larger coefficient indicates a stronger reactive power support capability of the inverter for the grid voltage, contributing to the stabilization of weak grid voltage.

[0120] In this embodiment, the virtual impedance, harmonic compensation coefficient, and reactive power droop coefficient can be obtained by mapping the impedance estimate based on the preset mapping relationship between the grid impedance amplitude and various control parameters. The virtual impedance, harmonic compensation coefficient, and reactive power droop coefficient are positively correlated with the impedance estimate; that is, the larger the grid impedance (the weaker the grid), the larger the values ​​of these three parameters. For example, the configuration of this mapping relationship can include, but is not limited to, mapping tables and mapping functions.

[0121] In this embodiment, by dynamically adjusting the virtual impedance, harmonic compensation coefficient, and reactive power droop coefficient based on the updated impedance estimate, the inverter can automatically optimize the output power quality according to the strength of the power grid.

[0122] In one exemplary embodiment, the perturbation frequency is 75 Hz.

[0123] Specifically, in active impedance detection methods, the selection of the disturbance frequency corresponding to the disturbance signal can easily lead to the following problems: If the disturbance frequency is too high, it can easily cause severe interference on the user side and significant nonlinearity in the high-frequency band of the power grid; if the disturbance frequency is too low, it can easily lead to long detection times and easy coupling with the system control bandwidth. More importantly, if the disturbance frequency coincides with the power frequency or its integer multiples of harmonics, the detection results are easily affected by background harmonic interference; while if the disturbance frequency is close to the system's inherent resonant frequency, it may be amplified or suppressed by the control loop, resulting in severe distortion of the measurement value. Based on this, in this embodiment, the disturbance frequency corresponding to the disturbance signal injected by the inverter into the grid is set to 75Hz. This avoids interference from the 50Hz power frequency and its integer multiples of harmonics, and is also far from the typical bandwidth range of the grid-connected inverter control loop, ensuring that the detection results are not affected by the dynamics of the control system itself.

[0124] Please refer to the following: Figure 4 , Figure 4Part (a) shows the current spectrum of the inverter output current before a 75Hz disturbance current signal is injected, where the total harmonic distortion (THD) is 1.41%. Figure 4 Part (b) shows the current spectrum of the inverter output current after a 75Hz disturbance current signal is injected, where the total harmonic distortion rate is 1.68%. Thus, after injecting a 75Hz disturbance signal, the total harmonic distortion rate of the inverter output current increases by less than 0.3%, which has a minimal impact on power quality.

[0125] In one exemplary embodiment, a method for grid impedance detection and power quality optimization of a grid-connected inverter is provided.

[0126] Specifically, the grid impedance detection and power quality optimization method for grid-connected inverters in this embodiment can be applied to, for example... Figure 5 The photovoltaic grid-connected power generation system shown includes a photovoltaic array, a grid-connected inverter, an LCL filter, a voltage and current sampling unit (not shown), and a digital controller. The photovoltaic array serves as the energy input, converting solar energy into DC power. The Boost circuit, located between the photovoltaic side and the DC bus, boosts the DC power output from the photovoltaic array and feeds it to the subsequent DC bus. The MPPT (Maximum Power Point Tracking) module calculates the optimal operating point in real time based on the output characteristics of the photovoltaic array and controls the Boost circuit to ensure the photovoltaic array operates stably near its maximum power point. The grid-connected inverter converts the DC power on the bus into AC power. It can be a three-level grid-connected inverter, including a three-level grid-connected inverter circuit and a PWM modulator. The digital controller controls the grid-connected inverter, outputting control commands and driving the three-level grid-connected inverter circuit via the PWM modulator to control the inverter output. The AC output of a grid-connected inverter can be connected to the power grid via an LCL filter.

[0127] In this embodiment, the grid impedance detection and power quality optimization method for the grid-connected inverter can be executed by a digital controller. For example... Figure 5 As shown, the digital controller can integrate an adaptive disturbance generation module, a first impedance estimation module, a Gertz algorithm extraction module, a second impedance estimation module, a grid state identification module, and a power coordinated control module. Specifically, the digital controller can control the voltage and current sampling unit to collect the three-phase voltage u_pcc_abc and grid current i_g_abc at the point of connection (PCC) in real time, and the sampled data can be sent to the digital controller.

[0128] For example, the modules within the digital controller can work collaboratively in the following sequence: First, the first impedance estimation module performs a first impedance estimation of the power grid based on the background harmonics at the grid connection point, obtaining the estimated impedance value of the power grid. Then, the power grid state identification module determines the current power grid strength level based on the impedance estimate. The adaptive disturbance generation module obtains the disturbance amplitude parameter for injecting disturbance into the power grid based on the current power grid strength level. Specifically, when the disturbance amplitude parameter is zero, the adaptive disturbance generation module determines that no disturbance signal needs to be injected into the power grid, allowing the first impedance estimation module to perform a first impedance estimation of the power grid again based on the background harmonics at the grid connection point, thus obtaining an updated impedance estimate of the power grid. When the disturbance amplitude parameter is not zero, the adaptive disturbance generation module controls the inverter to inject a disturbance signal into the power grid based on the disturbance amplitude parameter. After the disturbance signal is injected, the Gertz algorithm extraction module processes the current and voltage data at the grid connection point using the Gertz algorithm, calculating the imaginary part of the current, the real part of the current, the imaginary part of the voltage, and the real part of the voltage at the disturbance frequency. The second impedance estimation module obtains the resistive and inductive reactance components of the power grid based on the imaginary and real parts of the current, voltage, and current at the disturbance frequency. Then, based on these components, it obtains an updated impedance estimate of the power grid. Subsequently, the power grid state identification module, based on the updated impedance estimate output by either the first or second impedance estimation module, obtains new disturbance amplitude parameters for injecting disturbances into the power grid. The power coordinated control module dynamically adjusts the inverter's virtual impedance, harmonic compensation coefficient, and reactive power droop coefficient based on the current power grid strength level output by the power grid state identification module, and writes these parameters back to the controller parameter area, achieving closed-loop optimization of the inverter's output power quality. The disturbance frequency corresponding to the disturbance signal can be 75Hz.

[0129] For example, the grid state identification module can output the grid impedance estimate to the adaptive disturbance generation module and the power coordination control module to characterize the current grid strength level. For example, the grid state identification module can also calculate the grid short-circuit ratio based on the grid impedance estimate, the inverter's rated capacity, and the grid connection point's rated voltage, and output this short-circuit ratio to the adaptive disturbance generation module and the power coordination control module to characterize the current grid strength level. For example, the grid state identification module can also determine whether the grid is currently a strong grid, a weak grid, or an extremely weak grid based on the grid impedance estimate or short-circuit ratio, and output parameters characterizing the corresponding state to the adaptive disturbance generation module and the power coordination control module. For example, when the grid short-circuit ratio is greater than 5, it can be determined to be a strong grid; when the grid short-circuit ratio is between 1.5 and 5, it can be determined to be a weak grid; and when the grid short-circuit ratio is less than 1.5, it can be determined to be an extremely weak grid.

[0130] For example, the decision logic for the disturbance amplitude parameter can be as follows: Figure 6 As shown in the diagram, the grid state identification module outputs the grid impedance estimate to the adaptive disturbance generation module. The adaptive disturbance generation module uses a preset mapping table to determine the corresponding disturbance amplitude parameter based on the grid impedance estimate, where the disturbance amplitude parameter can be an amplitude coefficient. Subsequently, the adaptive disturbance generation module multiplies the amplitude coefficient by the rated disturbance current amplitude to generate a 75Hz disturbance current command, which is then superimposed on the inverter's inner current loop reference value. This command, after being adjusted by the current controller, drives the three-level inverter via the PWM modulator to inject a 75Hz disturbance current signal into the grid. Subsequently, the voltage and current components corresponding to the disturbance frequency can be extracted from the voltage and current data at the grid connection point, and the grid impedance can be calculated again. For example, taking a 100kW inverter as an example, the impedances of 0.08, 0.12, and 0.24Ω correspond to strong, weak, and extremely weak power grids, respectively, and the amplitudes of the injected disturbance current signals are 4.6A (disturbance amplitude parameter of 3%), 2.3A (disturbance amplitude parameter of 1.5%), and 0.8A (disturbance amplitude parameter of 0.5%).

[0131] For example, the power coordination control module can be achieved through, as shown in the example... Figure 7 The method shown optimizes the power quality of the inverter output. The grid condition identification module outputs the grid impedance estimate to the power coordination control module. The power coordination control module dynamically adjusts the inverter's virtual impedance, harmonic compensation coefficient, and reactive power droop coefficient based on a preset "grid impedance-control parameter" mapping table. After the control parameters are updated, the power coordination control module writes the new parameters into the corresponding registers of the digital controller and ultimately applies them to the inverter's main circuit through the inner current loop, outer voltage loop, and PWM modulator, achieving closed-loop optimization of the output power quality. This optimization process is performed synchronously with impedance detection; each new grid strength assessment result triggers a parameter update, ensuring the inverter always operates in the optimal control state that matches the current grid conditions.

[0132] For example, the digital controller can update the calculated grid impedance every two power frequency cycles to meet the real-time requirements of impedance detection.

[0133] In this embodiment, by introducing an adaptive disturbance regulation mechanism based on grid strength, the injection amplitude of the 75Hz disturbance signal is automatically reduced under weak grid conditions, and a passive observation mode is switched under extremely weak grid conditions. This fundamentally avoids the risk of power oscillation caused by fixed-strength disturbances, effectively ensuring the stable operation of the grid-connected inverter under full grid conditions. Simultaneously, by feeding back the precisely calculated grid impedance value to the controller in real time, the virtual impedance, harmonic compensation coefficient, and reactive power droop coefficient are dynamically adjusted. This enables the inverter to automatically optimize the output power quality according to grid strength, overcoming the shortcomings of existing technologies where detection results are only used for monitoring and are disconnected from control. Furthermore, the injection of the 75Hz non-characteristic frequency avoids interference from the power frequency and its integer multiples of harmonics, while ensuring low-frequency linearity under weak grid conditions. Combined with the Gertz algorithm for extracting current and voltage components, the computational burden is significantly reduced while maintaining extraction accuracy, demonstrating good engineering application value. Therefore, the solution in this embodiment can realize adaptive impedance detection and power quality co-optimization of grid-connected inverters under full grid operating conditions. The entire process operates in a closed loop within the digital controller, requiring no additional hardware, with a light computational burden and minimal impact on power quality. It effectively solves the technical problems of traditional technologies being prone to instability in weak grid conditions and the disconnect between detection and control.

[0134] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps. It is understood that the steps in different embodiments can be freely combined as needed, and all non-contradictory solutions formed by such combinations are within the scope of protection of this application.

[0135] Based on the same inventive concept, this application also provides a grid impedance detection and power quality optimization device for a grid-connected inverter, used to implement the grid impedance detection and power quality optimization method for the grid-connected inverter described above. The solution provided by this device is similar to the solution described in the above method. Therefore, the specific limitations of one or more grid impedance detection and power quality optimization device embodiments for grid-connected inverters provided below can be found in the limitations of the grid impedance detection and power quality optimization method for grid-connected inverters described above, and will not be repeated here.

[0136] In one exemplary embodiment, such as Figure 8 As shown, a grid impedance detection and power quality optimization device for a grid-connected inverter is provided, comprising:

[0137] The first estimation module 801 is used to perform a first impedance estimation on the power grid based on the background harmonics at the grid connection point, and obtain the impedance estimate of the power grid.

[0138] The first acquisition module 802 is used to obtain the disturbance amplitude parameter for disturbance injection into the power grid based on the impedance estimate; wherein the disturbance amplitude parameter is negatively correlated with the impedance estimate;

[0139] The second estimation module 803 is used to perform a first impedance estimation of the power grid based on the background harmonics at the grid connection point when the disturbance amplitude parameter is zero, so as to obtain the updated impedance estimate of the power grid.

[0140] The disturbance injection module 804 is used to control the inverter to inject a disturbance signal into the power grid according to the disturbance amplitude parameter when the disturbance amplitude parameter is not zero.

[0141] The third estimation module 805 is used to perform a second impedance estimation on the power grid based on the current and voltage data of the grid connection point and the disturbance frequency of the disturbance signal after the disturbance signal is injected, so as to obtain an updated impedance estimate of the power grid.

[0142] The second acquisition module 806 is used to return the step of obtaining the disturbance amplitude parameter for disturbance injection into the power grid based on the updated impedance estimate, until a preset stop condition is met.

[0143] In an exemplary embodiment, the third estimation module 805 is configured to: process the current data and the voltage data using the Gertz algorithm to calculate the imaginary part of the current, the real part of the current, the imaginary part of the voltage, and the real part of the voltage at the disturbance frequency; obtain the resistive component and the inductive reactance component of the power grid based on the imaginary part of the current, the real part of the current, the imaginary part of the voltage, and the real part of the voltage at the disturbance frequency; and obtain an updated impedance estimate of the power grid based on the resistive component and the inductive reactance component.

[0144] In an exemplary embodiment, the first acquisition module 802 is configured to: obtain the short-circuit ratio of the power grid based on the impedance estimate, the rated capacity of the inverter, and the rated voltage of the grid connection point; determine the disturbance amplitude parameter as zero when the short-circuit ratio is not greater than a first threshold; obtain the disturbance amplitude parameter corresponding to the short-circuit ratio based on a preset mapping relationship between the short-circuit ratio and the disturbance amplitude parameter when the short-circuit ratio is greater than the first threshold and less than a second threshold; the disturbance amplitude parameter is greater than zero and less than a preset upper limit of the disturbance amplitude parameter; and determine the disturbance amplitude parameter as the upper limit of the disturbance amplitude parameter when the short-circuit ratio is not less than the second threshold.

[0145] In one exemplary embodiment, the apparatus further includes a parameter adjustment module for adjusting the control parameters of the inverter based on the updated impedance estimate.

[0146] In an exemplary embodiment, the control parameters include virtual impedance, harmonic compensation coefficient, and reactive power droop coefficient; wherein the virtual impedance is positively correlated with the impedance estimate, the harmonic compensation coefficient is positively correlated with the impedance estimate, and the reactive power droop coefficient is positively correlated with the impedance estimate.

[0147] In one exemplary embodiment, the perturbation frequency is 75 Hz.

[0148] The various modules in the grid impedance detection and power quality optimization device of the aforementioned grid-type inverter can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware within or independently of the processor in a computer device, or stored in software within the memory of a computer device, so that the processor can call and execute the corresponding operations of each module.

[0149] In one exemplary embodiment, a computer device is provided, which may be a digital controller, and its internal structure diagram may be as follows: Figure 9As shown, this computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides the environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The I / O interfaces are used for exchanging information between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When the computer program is executed by the processor, it implements a method for grid impedance detection and power quality optimization in a grid-connected inverter.

[0150] Those skilled in the art will understand that Figure 9 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0151] In one embodiment, a computer device is also provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above method embodiments.

[0152] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon that, when executed by a processor, implements the steps in the above method embodiments.

[0153] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above method embodiments.

[0154] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0155] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0156] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0157] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for grid impedance detection and power quality optimization of a grid-connected inverter, characterized in that, The method includes: The first impedance estimate of the power grid is obtained by performing a first impedance estimate on the power grid based on the background harmonics at the grid connection point; Based on the impedance estimate, the disturbance amplitude parameter for injecting disturbance into the power grid is obtained; wherein, the disturbance amplitude parameter is negatively correlated with the impedance estimate; When the disturbance amplitude parameter is zero, the first impedance estimate of the power grid is performed based on the background harmonics at the grid connection point to obtain the updated impedance estimate of the power grid. If the disturbance amplitude parameter is not zero, the inverter is controlled to inject a disturbance signal into the power grid according to the disturbance amplitude parameter. After the disturbance signal is injected, a second impedance estimate is performed on the power grid based on the current and voltage data of the grid connection point and the disturbance frequency of the disturbance signal to obtain an updated impedance estimate of the power grid. Based on the updated impedance estimate, the process returns to the step of obtaining the disturbance amplitude parameters for the disturbance injection into the power grid based on the impedance estimate, until a preset stop condition is met.

2. The method according to claim 1, characterized in that, The step of performing a second impedance estimation on the power grid based on the current and voltage data at the grid connection point and the disturbance frequency of the disturbance signal to obtain an updated impedance estimate of the power grid includes: The current data and voltage data are processed using the Gertz algorithm to calculate the imaginary part of the current, the real part of the current, the imaginary part of the voltage, and the real part of the voltage at the disturbance frequency. Based on the imaginary part of the current, the real part of the current, the imaginary part of the voltage, and the real part of the voltage at the disturbance frequency, the resistive component and the inductive reactance component of the power grid are obtained. The updated impedance estimate of the power grid is obtained based on the resistive component and the inductive reactance component.

3. The method according to claim 1, characterized in that, The step of obtaining the disturbance amplitude parameters for injecting disturbance into the power grid based on the impedance estimate includes: Based on the impedance estimate, the rated capacity of the inverter, and the rated voltage of the grid connection point, the short-circuit ratio of the power grid is obtained; When the short-circuit ratio is not greater than the first threshold, the disturbance amplitude parameter is determined to be zero; When the short-circuit ratio is greater than a first threshold and less than a second threshold, the disturbance amplitude parameter corresponding to the short-circuit ratio is obtained according to the preset mapping relationship between the short-circuit ratio and the disturbance amplitude parameter; the disturbance amplitude parameter is greater than zero and less than the preset upper limit of the disturbance amplitude parameter. When the short-circuit ratio is not less than the second threshold, the disturbance amplitude parameter is determined to be the upper limit of the disturbance amplitude parameter.

4. The method according to claim 1, characterized in that, After obtaining the updated impedance estimate of the power grid, the process further includes: The control parameters of the inverter are adjusted based on the updated impedance estimate.

5. The method according to claim 4, characterized in that, The control parameters include virtual impedance, harmonic compensation coefficient, and reactive power droop coefficient; wherein, the virtual impedance is positively correlated with the impedance estimate, the harmonic compensation coefficient is positively correlated with the impedance estimate, and the reactive power droop coefficient is positively correlated with the impedance estimate.

6. The method according to any one of claims 1 to 5, characterized in that, The disturbance frequency is 75 Hz.

7. A grid impedance detection and power quality optimization device for a grid-connected inverter, characterized in that, The device includes: The first estimation module is used to perform a first impedance estimation on the power grid based on the background harmonics at the grid connection point, and obtain the impedance estimate of the power grid. The first acquisition module is used to obtain the disturbance amplitude parameter for injecting disturbance into the power grid based on the impedance estimate; wherein the disturbance amplitude parameter is negatively correlated with the impedance estimate; The second estimation module is used to perform a first impedance estimation of the power grid based on the background harmonics at the grid connection point when the disturbance amplitude parameter is zero, so as to obtain the updated impedance estimate of the power grid. The disturbance injection module is used to control the inverter to inject a disturbance signal into the power grid according to the disturbance amplitude parameter when the disturbance amplitude parameter is not zero. The third estimation module is used to perform a second impedance estimation on the power grid based on the current and voltage data of the grid connection point and the disturbance frequency of the disturbance signal after the disturbance signal is injected, so as to obtain an updated impedance estimate of the power grid. The second acquisition module is used to return the step of obtaining the disturbance amplitude parameter for disturbance injection into the power grid based on the updated impedance estimate, until a preset stop condition is met.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

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