A reactive power and voltage control method and system for photovoltaic inverters

Abstract

This invention relates to the technical field of power grid dispatching, specifically to a method and system for reactive power and voltage control of photovoltaic (PV) inverters. The method includes: analyzing the changes in irradiance in the corresponding irradiated areas of each PV inverter in the PV grid, and the harmonic interference intensity in the monitoring voltage signals of each PV inverter, to determine the external interference index of each PV inverter; analyzing the changes in circuit impedance and reactive power corresponding to each PV inverter in the PV grid, to determine the internal interference index of each PV inverter; correcting the corresponding initial droop coefficient based on the external and internal interference indices of each PV inverter to obtain the target droop coefficient of each PV inverter; and controlling the reactive power and voltage of the PV inverters in the PV grid based on the target droop coefficient of each PV inverter. This invention can improve the overall reactive power control effect of the PV grid.

Description

Technical Field

[0001] This invention relates to the technical field of power grid dispatching, and specifically to a reactive power and voltage control method and system for photovoltaic inverters. Background Technology

[0002] With the development of new renewable energy fields and the continuous improvement of photovoltaic power generation technology, photovoltaic power generation units have become a major source of power supply for the power grid. However, unlike traditional thermal power generation units, photovoltaic power generation units are severely affected by the environment, and their power generation exhibits strong random fluctuations and intermittency. This causes photovoltaic power generation units to impact the power grid when connected to the grid, affecting electrical variables such as reactive voltage and reactive power. Therefore, it is necessary to implement reasonable voltage control for distributed photovoltaic power generation units when connected to the grid to ensure the operational stability of the power grid.

[0003] A photovoltaic (PV) inverter is a controllable power electronic device with reactive power regulation and compensation functions, capable of simultaneously regulating the voltage at the PV grid connection point and the reactive power of the grid. In distributed PV grids, the sunlight conditions around the PV generators vary, necessitating the use of droop control strategies to control the reactive power of the PV inverters corresponding to each generator. However, traditional droop control strategies, based on a constant droop coefficient, provide unified control of the reactive power of multiple PV inverters, making it difficult to adapt to complex actual sunlight conditions. This results in poor overall reactive power control performance of the PV grid. Summary of the Invention

[0004] The purpose of this invention is to provide a reactive power and voltage control method and system for photovoltaic inverters, which solves the technical problem of poor reactive power control effect of existing technologies on the overall photovoltaic power grid.

[0005] In a first aspect, one embodiment of the present invention provides a reactive power voltage control method for a photovoltaic inverter, the method comprising: The changes in irradiance in the irradiance area corresponding to each photovoltaic inverter in the photovoltaic grid and the harmonic interference intensity in the monitoring voltage signal of each photovoltaic inverter in the photovoltaic grid are analyzed to determine the external interference index of each photovoltaic inverter. Analyze the circuit impedance and reactive power changes of each photovoltaic inverter in the photovoltaic grid to determine the internal interference index of each photovoltaic inverter. The target droop coefficient for each photovoltaic inverter is obtained by correcting the corresponding initial droop coefficient based on the external interference index and internal interference index of each photovoltaic inverter. The reactive voltage of the photovoltaic inverters in the photovoltaic grid is controlled based on the target droop coefficient of each photovoltaic inverter.

[0006] In some embodiments, the analysis of the changes in irradiance in the irradiated areas corresponding to each photovoltaic inverter in the photovoltaic grid, and the harmonic interference intensity in the monitoring voltage signals of each photovoltaic inverter in the photovoltaic grid, to determine the external interference index of each photovoltaic inverter, includes: During the monitoring period, the changes in light intensity of the corresponding irradiated areas of each photovoltaic inverter in the photovoltaic grid at adjacent times are analyzed to determine multiple light intensity change factors corresponding to each photovoltaic inverter. Calculate the average value of multiple light intensity variation factors corresponding to each photovoltaic inverter to obtain the light intensity variation characteristic value of each photovoltaic inverter; During the monitoring period, the proportion of harmonic energy in the monitoring voltage signal of each photovoltaic inverter in the photovoltaic grid is analyzed to determine the harmonic interference characteristic value of each photovoltaic inverter. The external interference index of each photovoltaic inverter is determined based on the characteristic values ​​of light intensity variation and harmonic interference of each inverter.

[0007] In some embodiments, the step of analyzing the changes in irradiance intensity of the irradiated areas corresponding to each photovoltaic inverter in the photovoltaic grid at adjacent times during the monitoring period, in order to determine multiple irradiance variation factors corresponding to each photovoltaic inverter, includes: During the monitoring period, the absolute difference in light intensity of the illuminated area corresponding to each photovoltaic inverter at adjacent times is calculated to obtain multiple light intensity change values ​​corresponding to each photovoltaic inverter. Among the multiple light intensity change values ​​corresponding to each photovoltaic inverter, the ratio of each light intensity change value corresponding to each photovoltaic inverter to the light intensity at the corresponding monitoring time is calculated to obtain multiple light intensity change factors corresponding to each photovoltaic inverter.

[0008] In some embodiments, analyzing the proportion of harmonic energy in the monitoring voltage signals of each photovoltaic inverter in the photovoltaic grid during the monitoring period to determine the harmonic interference characteristic value of each photovoltaic inverter includes: During the monitoring period, the monitoring voltage signal of each photovoltaic inverter is subjected to fast Fourier transform to obtain the voltage spectrum data of each photovoltaic inverter. Based on the voltage spectrum data of each photovoltaic inverter, determine the fundamental voltage energy and total voltage energy of each photovoltaic inverter; Calculate the difference between the total voltage energy and the fundamental voltage energy of each photovoltaic inverter to obtain the voltage harmonic energy of each photovoltaic inverter; Calculate the ratio of voltage harmonic energy to total voltage energy for each photovoltaic inverter to obtain the harmonic interference characteristic value for each photovoltaic inverter.

[0009] In some embodiments, determining the external interference index of each photovoltaic inverter based on the light intensity variation characteristic value and harmonic interference characteristic value of each photovoltaic inverter includes: The light intensity variation characteristic value of each photovoltaic inverter is normalized to obtain the light intensity variation normalized value of each photovoltaic inverter, wherein the light intensity variation characteristic value and the light intensity variation normalized value are positively correlated. The normalized value of light intensity variation and the harmonic interference characteristic value of each photovoltaic inverter are weighted and calculated to obtain the external interference index of each photovoltaic inverter. The weight of the harmonic interference characteristic value is greater than the weight of the normalized value of light intensity variation.

[0010] In some embodiments, the analysis of the circuit impedance and reactive power changes corresponding to each photovoltaic inverter in the photovoltaic grid, and the determination of the internal interference index of each photovoltaic inverter, includes: During the monitoring period, the degree of reactive power fluctuation of each photovoltaic inverter is analyzed, and the power fluctuation characteristic value of each photovoltaic inverter is determined. The circuit impedance of each photovoltaic inverter is normalized to obtain the impedance characteristic value of each photovoltaic inverter. The internal interference index of each photovoltaic inverter is determined based on the power fluctuation characteristic value and impedance characteristic value of each photovoltaic inverter.

[0011] In some embodiments, analyzing the reactive power fluctuation of each photovoltaic inverter during the monitoring period and determining the power fluctuation characteristic value of each photovoltaic inverter includes: During the monitoring period, the dispersion coefficient of reactive power of each photovoltaic inverter is determined as the power fluctuation characteristic value of each photovoltaic inverter.

[0012] In some embodiments, the power fluctuation characteristic value is positively correlated with the internal interference index, and the impedance characteristic value is negatively correlated with the internal interference index.

[0013] In some embodiments, the step of correcting the initial droop coefficient corresponding to the external interference index and internal interference index of each photovoltaic inverter to obtain the target droop coefficient of each photovoltaic inverter includes: Based on the external interference index of each photovoltaic inverter, an external interference correction value is determined for each photovoltaic inverter. When the external interference index is greater than or equal to the index threshold, the corresponding external interference correction value is a first value. When the external interference index is less than the index threshold, the corresponding external interference correction value is a second value. The first value is greater than the second value, and the second value is greater than or equal to 1. Calculate the product of the external interference correction value, the internal interference index and the corresponding initial droop coefficient for each photovoltaic inverter to obtain the target droop coefficient for each photovoltaic inverter.

[0014] Secondly, another embodiment of the present invention provides a reactive voltage control system for a photovoltaic inverter, the system comprising: The external interference analysis module analyzes the changes in light intensity in the corresponding light areas of each photovoltaic inverter in the photovoltaic grid, as well as the harmonic interference intensity in the monitoring voltage signals of each photovoltaic inverter in the photovoltaic grid, and determines the external interference index of each photovoltaic inverter. The internal interference analysis module is used to analyze the circuit impedance and reactive power changes of each photovoltaic inverter in the photovoltaic grid and determine the internal interference index of each photovoltaic inverter. The droop coefficient determination module is used to correct the corresponding initial droop coefficient based on the external interference index and internal interference index of each photovoltaic inverter, so as to obtain the target droop coefficient of each photovoltaic inverter. The control module is used to control the reactive voltage of the photovoltaic inverters in the photovoltaic grid according to the target droop coefficient of each photovoltaic inverter.

[0015] Thirdly, in another embodiment of the present invention, an electronic device is provided, including a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the steps of the method described in the first aspect.

[0016] Fourthly, in another embodiment of the present invention, a computer-readable storage medium is provided, on which a computer program is stored, which, when executed by a processor, implements the steps of the method described in the first aspect.

[0017] The present invention has the following beneficial effects: This invention analyzes the changes in illuminance in the corresponding illuminated areas of each photovoltaic inverter in a photovoltaic power grid, as well as the harmonic interference intensity in the monitoring voltage signals of each photovoltaic inverter, to dynamically assess the severity of external interference to each photovoltaic inverter from both the illuminance and harmonic interference dimensions. It then further analyzes the changes in circuit impedance and reactive power corresponding to each photovoltaic inverter in the photovoltaic power grid to dynamically assess the severity of internal disturbances caused by the inverter's own structure from both impedance and reactive power dimensions. Finally, it comprehensively corrects the initial droop coefficient of each photovoltaic inverter by integrating external interference and internal disturbances, determining a target droop coefficient suitable for each inverter's actual operating conditions. Based on this, it controls the reactive voltage of the photovoltaic inverters within the photovoltaic power grid, thereby improving the overall reactive power control effect of the photovoltaic power grid. Attached Figure Description

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

[0019] Figure 1 This is a flowchart illustrating a reactive voltage control method for a photovoltaic inverter provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of a reactive voltage control system for a photovoltaic inverter provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0020] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a reactive power voltage control method and system for photovoltaic inverters proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] The following description, in conjunction with the accompanying drawings, details a specific scheme for a reactive voltage control method and system for photovoltaic inverters provided by the present invention.

[0023] This invention provides a reactive power voltage control method for photovoltaic inverters, such as... Figure 1 As shown, the method includes: Step S1: Analyze the changes in irradiance in the irradiated areas corresponding to each photovoltaic inverter in the photovoltaic grid, as well as the harmonic interference intensity in the monitoring voltage signals of each photovoltaic inverter in the photovoltaic grid, and determine the external interference index of each photovoltaic inverter.

[0024] In this invention, the photovoltaic grid should be understood as a network composed of multiple photovoltaic power generation units in a distributed networking manner, wherein each photovoltaic power generation unit is equipped with a photovoltaic inverter.

[0025] In a distributed photovoltaic grid, the different locations of each photovoltaic power generation unit result in different light intensities. Coupled with the intermittent and fluctuating nature of light intensity changes, the harmonic interference generated by the differences in intermittent light fluctuations among the photovoltaic power generation units will vary to some extent.

[0026] In addition to the differences in intermittent light fluctuations, the electromagnetic interference experienced by each photovoltaic power generation unit varies due to their different locations. This results in certain differences in harmonic interference caused by factors other than intermittent light fluctuations among the photovoltaic power generation units.

[0027] However, it should be noted that simply analyzing the monitoring voltage signals of each photovoltaic inverter in the photovoltaic grid to assess the degree of harmonic interference experienced by each inverter carries a significant risk of error (such as measurement errors in the collected monitoring voltage signals, or certain faults in the collected monitoring voltage signals). By introducing the risk of changes in the light intensity of the corresponding irradiated area of ​​the photovoltaic inverter through the above measures, the harmonic interference intensity obtained from the analysis of the monitoring voltage signals can be compensated in combination with the real environment, thereby suppressing the measurement errors introduced by external interference and making the final determined external interference index more accurate and reliable.

[0028] The external interference index indicates the severity of harmonic interference affecting the voltage data of the corresponding photovoltaic inverter. A higher external interference index indicates more severe harmonic interference affecting the voltage data of the corresponding photovoltaic inverter.

[0029] The more severe the harmonic interference on the voltage data of the photovoltaic inverter, the greater the difficulty in controlling the reactive voltage of the photovoltaic inverter (manifested as a large deviation between the calculated control amount and the actual required control amount). Therefore, when controlling the reactive voltage output of the photovoltaic inverter, adaptive compensation can be made by referring to the harmonic interference it is subjected to, so as to suppress the control error introduced by the harmonic interference.

[0030] Specifically, the analysis of the changes in irradiance in the irradiated areas corresponding to each photovoltaic inverter in the photovoltaic grid, and the harmonic interference intensity in the monitoring voltage signals of each photovoltaic inverter in the photovoltaic grid, to determine the external interference index of each photovoltaic inverter, includes: During the monitoring period, the changes in light intensity of the corresponding irradiated areas of each photovoltaic inverter in the photovoltaic grid at adjacent times are analyzed to determine multiple light intensity change factors corresponding to each photovoltaic inverter. Calculate the average value of multiple light intensity variation factors corresponding to each photovoltaic inverter to obtain the light intensity variation characteristic value of each photovoltaic inverter; During the monitoring period, the proportion of harmonic energy in the monitoring voltage signal of each photovoltaic inverter in the photovoltaic grid is analyzed to determine the harmonic interference characteristic value of each photovoltaic inverter. The external interference index of each photovoltaic inverter is determined based on the characteristic values ​​of light intensity variation and harmonic interference of each inverter.

[0031] The process of analyzing the changes in irradiance in the corresponding irradiance areas of each photovoltaic inverter in the photovoltaic grid at adjacent times during the monitoring period, in order to determine multiple irradiance variation factors corresponding to each photovoltaic inverter, includes: During the monitoring period, the absolute difference in light intensity of the illuminated area corresponding to each photovoltaic inverter at adjacent times is calculated to obtain multiple light intensity change values ​​corresponding to each photovoltaic inverter. Among the multiple light intensity change values ​​corresponding to each photovoltaic inverter, the ratio of each light intensity change value corresponding to each photovoltaic inverter to the light intensity at the corresponding monitoring time is calculated to obtain multiple light intensity change factors corresponding to each photovoltaic inverter.

[0032] The monitoring period is a time period that starts from the current time and traces back to a set duration (such as 5 minutes or 10 minutes), or it is a time period that is one of multiple consecutive time periods divided into the time domain according to a set period (such as 10 minutes).

[0033] The solar-powered inverter's corresponding illumination area should be understood as the solar-sensitive area of ​​the solar-powered inverter corresponding to the solar power generation unit.

[0034] It should be understood that the larger the characteristic value of light intensity variation of the photovoltaic inverter, the more drastic the change in light intensity of the photovoltaic inverter during the monitoring period, which means that the degree of intermittent fluctuation of light in the corresponding light area of ​​the photovoltaic inverter is more serious, and the more serious the harmonic interference on the voltage data of the photovoltaic inverter is.

[0035] For example, the first in the photovoltaic grid The characteristic value of light intensity variation of a photovoltaic inverter It can be represented as:

[0036] in, This indicates the total number of monitoring times included in the monitoring period. Indicates the first The photovoltaic inverter during the monitoring period The light intensity at each monitoring time Indicates the first The photovoltaic inverter during the monitoring period The light intensity at each monitoring time This represents a constant whose value ranges from 0.001 to 0.01 (avoiding zero in the denominator). Indicates the first The photovoltaic inverter during the monitoring period Light intensity change factor corresponding to each monitoring time.

[0037] The process of analyzing the proportion of harmonic energy in the monitoring voltage signals of each photovoltaic inverter in the photovoltaic grid during the monitoring period to determine the harmonic interference characteristic value of each photovoltaic inverter includes: During the monitoring period, the monitoring voltage signal of each photovoltaic inverter is subjected to fast Fourier transform to obtain the voltage spectrum data of each photovoltaic inverter. Based on the voltage spectrum data of each photovoltaic inverter, determine the fundamental voltage energy and total voltage energy of each photovoltaic inverter; Calculate the difference between the total voltage energy and the fundamental voltage energy of each photovoltaic inverter to obtain the voltage harmonic energy of each photovoltaic inverter; Calculate the ratio of voltage harmonic energy to total voltage energy for each photovoltaic inverter to obtain the harmonic interference characteristic value for each photovoltaic inverter.

[0038] Wherein, the fundamental voltage energy is the square of the amplitude of the fundamental frequency (50Hz) in the voltage spectrum data of the corresponding photovoltaic inverter, and the total voltage energy is the sum of the squares of the amplitudes of each harmonic frequency in the voltage spectrum data of the corresponding photovoltaic inverter. In this invention, the harmonic frequency is an integer multiple (greater than or equal to 2) of the fundamental frequency.

[0039] It should be understood that the larger the harmonic interference characteristic value, the more severe the harmonic interference reflected in the transmitted voltage data of the corresponding photovoltaic inverter.

[0040] For example, the first in the photovoltaic grid Harmonic interference characteristic value of a photovoltaic inverter It can be represented as:

[0041] in, Indicates the first The amplitude of the fundamental frequency in the voltage spectrum data of a photovoltaic inverter. Indicates the first The voltage fundamental energy of a photovoltaic inverter Indicates the first Total voltage energy of each photovoltaic inverter.

[0042] Specifically, determining the external interference index of each photovoltaic inverter based on its light intensity variation characteristic value and harmonic interference characteristic value includes: The light intensity variation characteristic value of each photovoltaic inverter is normalized to obtain the light intensity variation normalized value of each photovoltaic inverter, wherein the light intensity variation characteristic value and the light intensity variation normalized value are positively correlated. The normalized value of light intensity variation and the harmonic interference characteristic value of each photovoltaic inverter are weighted and calculated to obtain the external interference index of each photovoltaic inverter. The weight of the harmonic interference characteristic value is greater than the weight of the normalized value of light intensity variation.

[0043] In this invention, the characteristic value of light intensity variation of photovoltaic inverter is normalized to a range of 0-1, thereby eliminating the dimensional difference between light intensity data and spectral energy data and ensuring the accuracy of the calculated external interference index.

[0044] For example, the first in the photovoltaic grid External interference index of a photovoltaic inverter It can be represented as:

[0045] in, This represents the weight corresponding to the normalized value of the light intensity change. The weights corresponding to the harmonic interference eigenvalues ​​are represented. Indicates the first Normalized value of light intensity variation of a photovoltaic inverter This is a natural constant. In this example, based on experience, we can... and Set them to 0.3 and 0.7 respectively.

[0046] Step S2: Analyze the circuit impedance and reactive power changes of each photovoltaic inverter in the photovoltaic grid to determine the internal interference index of each photovoltaic inverter.

[0047] Specifically, the analysis of the circuit impedance and reactive power changes corresponding to each photovoltaic inverter in the photovoltaic power grid, and the determination of the internal interference index of each photovoltaic inverter, includes: During the monitoring period, the degree of reactive power fluctuation of each photovoltaic inverter is analyzed, and the power fluctuation characteristic value of each photovoltaic inverter is determined. The circuit impedance of each photovoltaic inverter is normalized to obtain the impedance characteristic value of each photovoltaic inverter. The internal interference index of each photovoltaic inverter is determined based on the power fluctuation characteristic value and impedance characteristic value of each photovoltaic inverter.

[0048] The circuit impedance of a photovoltaic inverter is specifically the equivalent impedance of the power branch where the photovoltaic inverter is located (a branch consisting of its corresponding photovoltaic power generation unit and several loads powered by the photovoltaic power generation unit).

[0049] The power fluctuation characteristic value is positively correlated with the internal interference index, and the impedance characteristic value is negatively correlated with the internal interference index.

[0050] Specifically, by analyzing the fluctuation of reactive power output by each photovoltaic inverter, the degree of change in the load and / or operating status of the photovoltaic power generation unit in the power branch where the photovoltaic inverter is located can be assessed. The higher the fluctuation of reactive power output by the photovoltaic inverter, the more frequent the changes in the operating status of each device in the power branch where the photovoltaic inverter is located. In this case, the droop coefficient of the photovoltaic inverter should be increased to adapt to the frequent changes in the operating status of each device in the power branch where the photovoltaic inverter is located, so as to improve the response speed of reactive voltage control.

[0051] The circuit impedance of a photovoltaic (PV) inverter reflects its sensitivity to reactive power voltage regulation. The smaller the circuit impedance, the weaker the sensitivity of the PV inverter to reactive power voltage regulation. In this case, increasing the droop factor of the PV inverter adaptively can improve its sensitivity to reactive power voltage regulation, thereby improving the accuracy of adjusting the reactive power voltage output by the PV inverter. On the other hand, the larger the circuit impedance, the stronger the sensitivity of the PV inverter to reactive power voltage regulation. In this case, appropriately reducing the droop factor of the PV inverter can avoid the problem of oversensitivity to reactive power voltage regulation, thereby avoiding sudden changes in reactive power voltage during regulation and ensuring the overall operational stability of the photovoltaic power grid.

[0052] For example, the first in the photovoltaic grid Impedance characteristic value of a photovoltaic inverter It can be represented as:

[0053] in, Indicates the first The circuit impedance of a photovoltaic inverter This represents the largest circuit impedance among the multiple photovoltaic inverters in the photovoltaic power grid.

[0054] Furthermore, the step of analyzing the reactive power fluctuation of each photovoltaic inverter during the monitoring period and determining the power fluctuation characteristic value of each photovoltaic inverter includes: During the monitoring period, the dispersion coefficient of reactive power of each photovoltaic inverter is determined as the power fluctuation characteristic value of each photovoltaic inverter.

[0055] In the above setup, by collecting multiple reactive power data from each photovoltaic inverter at multiple monitoring times and calculating the dispersion coefficient of the reactive power of each photovoltaic inverter, the power fluctuation of each photovoltaic inverter can be quickly and accurately quantified.

[0056] For example, the first in the photovoltaic grid Power fluctuation characteristics of a photovoltaic inverter It can be represented as:

[0057] in, Indicates the first The standard deviation of multiple reactive power data collected by a photovoltaic inverter during the monitoring period. Indicates the first The average value of multiple reactive power data collected by a photovoltaic inverter during the monitoring period.

[0058] The first in the photovoltaic grid Internal interference index of a photovoltaic inverter It can be represented as:

[0059] in, This represents the Sigmoid function.

[0060] Step S3: Correct the initial droop coefficient corresponding to the external interference index and internal interference index of each photovoltaic inverter to obtain the target droop coefficient of each photovoltaic inverter.

[0061] Specifically, the initial droop coefficient for each photovoltaic inverter is the droop coefficient determined for each photovoltaic inverter based on the droop control strategy provided by existing technology.

[0062] In this invention, the initial droop coefficient ranges from [0.01, 0.05], and users can make an adaptive selection based on the actual voltage conditions of the photovoltaic grid where each photovoltaic inverter is located.

[0063] Specifically, the step of correcting the initial droop coefficient corresponding to the external interference index and internal interference index of each photovoltaic inverter to obtain the target droop coefficient of each photovoltaic inverter includes: Based on the external interference index of each photovoltaic inverter, an external interference correction value is determined for each photovoltaic inverter. When the external interference index is greater than or equal to the index threshold, the corresponding external interference correction value is a first value. When the external interference index is less than the index threshold, the corresponding external interference correction value is a second value. The first value is greater than the second value, and the second value is greater than or equal to 1. Calculate the product of the external interference correction value, the internal interference index and the corresponding initial droop coefficient for each photovoltaic inverter to obtain the target droop coefficient for each photovoltaic inverter.

[0064] In the above settings, the strength of harmonic interference is distinguished by setting the exponential threshold, and the external interference correction value of the initial droop coefficient is dynamically adjusted according to the different strengths of harmonic interference to suppress the over-correction problem in the case of weak harmonic interference.

[0065] In application, the second value can be set to a fixed value, while the first value can be set to a variable value (dynamically adjusted according to the value of the external interference index) to suppress the overcorrection problem under weak harmonic interference while dynamically adapting to the correction requirements under strong harmonic interference.

[0066] For example, the first in the photovoltaic grid External interference correction value for a photovoltaic inverter It can be represented as:

[0067] in, This indicates the aforementioned index threshold (based on experience). The value can be set to 0.3).

[0068] Furthermore, the first in the photovoltaic grid Target droop coefficient for a photovoltaic inverter It can be represented as:

[0069] in, Indicates the first The initial droop factor of a photovoltaic inverter.

[0070] Step S4: Control the reactive voltage of the photovoltaic inverters in the photovoltaic grid according to the target droop coefficient of each photovoltaic inverter.

[0071] Specifically, after determining the target droop coefficient for each photovoltaic inverter based on the aforementioned process, the target droop coefficient for each photovoltaic inverter, along with the standard reactive voltage, standard reactive power, and reactive power limiting of each photovoltaic inverter, are input into the control module (also known as the control chip) of the corresponding photovoltaic inverter. The chip then calculates the required reactive power based on its own droop control algorithm and executes the output, thereby completing the control of the corresponding reactive voltage.

[0072] In summary, this invention analyzes the changes in illuminance in the illuminated areas corresponding to each photovoltaic inverter in a photovoltaic power grid, as well as the harmonic interference intensity in the monitoring voltage signals of each photovoltaic inverter, to dynamically assess the severity of external interference to each photovoltaic inverter from both the illuminance and harmonic interference dimensions. Furthermore, it analyzes the changes in circuit impedance and reactive power corresponding to each photovoltaic inverter in the photovoltaic power grid to dynamically assess the severity of internal disturbances caused by the inverter's own structure from both impedance and reactive power dimensions. Finally, it comprehensively corrects the initial droop coefficient of each photovoltaic inverter by integrating external interference and internal disturbances, determining a target droop coefficient suitable for each inverter's actual operating conditions. Based on this, it controls the reactive voltage of the photovoltaic inverters within the photovoltaic power grid, thereby improving the overall reactive power control effect of the photovoltaic power grid.

[0073] This invention also provides a reactive power and voltage control system for photovoltaic inverters, such as... Figure 2 As shown, the reactive power and voltage control system 200 for the photovoltaic inverter includes: The external interference analysis module 201 analyzes the changes in light intensity in the corresponding light areas of each photovoltaic inverter in the photovoltaic grid, as well as the harmonic interference intensity in the monitoring voltage signals of each photovoltaic inverter in the photovoltaic grid, and determines the external interference index of each photovoltaic inverter. The internal interference analysis module 202 is used to analyze the circuit impedance and reactive power changes of each photovoltaic inverter in the photovoltaic grid and determine the internal interference index of each photovoltaic inverter. The droop coefficient determination module 203 is used to correct the corresponding initial droop coefficient based on the external interference index and internal interference index of each photovoltaic inverter, so as to obtain the target droop coefficient of each photovoltaic inverter. The control module 204 is used to control the reactive voltage of the photovoltaic inverters in the photovoltaic grid according to the target droop coefficient of each photovoltaic inverter.

[0074] It should be noted that the system provided in the above embodiments is only an example of the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the computer equipment can be divided into different functional modules to complete all or part of the functions described above. In addition, the reactive voltage control system for photovoltaic inverters and the reactive voltage control method for photovoltaic inverters provided in the above embodiments belong to the same concept, and their specific implementation process can be found in the method embodiments, which will not be repeated here.

[0075] This invention also provides an electronic device. Please refer to [link to relevant documentation]. Figure 3The electronic device may include a processor 301, a memory 302, and a program 3021 stored in the memory 302 and capable of running on the processor 301.

[0076] When program 3021 is executed by processor 301, it can achieve the following: Figure 1 Any steps in the corresponding method embodiments and the achievement of the same beneficial effects will not be repeated here.

[0077] Those skilled in the art will understand that all or part of the steps of the methods described in the above embodiments can be implemented by hardware related to program instructions, and the program can be stored in a readable medium.

[0078] This invention also provides a readable storage medium storing a computer program, which, when executed by a processor, can perform the above-described functions. Figure 1 Any step in the corresponding method embodiment can achieve the same technical effect, and will not be repeated here to avoid repetition.

[0079] The computer-readable storage medium of this invention can be any combination of one or more computer-readable media. The computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. For example, a computer-readable storage medium can be an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media include: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this document, a computer-readable storage medium can be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0080] Computer-readable signal media may include data signals propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. Computer-readable signal media may also be any computer-readable medium other than computer-readable storage media, capable of sending, propagating, or transmitting programs for use by or in connection with an instruction execution system, apparatus, or device.

[0081] The program code contained on the storage medium can be transmitted using any suitable medium, including but not limited to wireless, wire, optical fiber, RF, etc., or any suitable combination thereof.

[0082] Computer program code for performing the operations of this invention can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, as well as conventional procedural programming languages ​​such as "C" or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or terminal. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0083] This invention also provides a computer program product that, when run on a computer, causes the computer to perform the aforementioned steps to implement the reactive voltage control method and system for photovoltaic inverters provided in the above embodiments.

[0084] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0085] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A reactive power and voltage control method for photovoltaic inverters, characterized in that, The method includes: The changes in irradiance in the irradiance area corresponding to each photovoltaic inverter in the photovoltaic grid and the harmonic interference intensity in the monitoring voltage signal of each photovoltaic inverter in the photovoltaic grid are analyzed to determine the external interference index of each photovoltaic inverter. Analyze the circuit impedance and reactive power changes of each photovoltaic inverter in the photovoltaic grid to determine the internal interference index of each photovoltaic inverter. The target droop coefficient for each photovoltaic inverter is obtained by correcting the corresponding initial droop coefficient based on the external interference index and internal interference index of each photovoltaic inverter. The reactive voltage of the photovoltaic inverters in the photovoltaic grid is controlled according to the target droop coefficient of each photovoltaic inverter. The analysis of the changes in irradiance in the corresponding irradiance areas of each photovoltaic inverter in the photovoltaic power grid, and the harmonic interference intensity in the monitoring voltage signals of each photovoltaic inverter in the photovoltaic power grid, determines the external interference index of each photovoltaic inverter, including: During the monitoring period, the changes in light intensity of the corresponding irradiated areas of each photovoltaic inverter in the photovoltaic grid at adjacent times are analyzed to determine multiple light intensity change factors corresponding to each photovoltaic inverter. Calculate the average value of multiple light intensity variation factors corresponding to each photovoltaic inverter to obtain the light intensity variation characteristic value of each photovoltaic inverter; During the monitoring period, the proportion of harmonic energy in the monitoring voltage signal of each photovoltaic inverter in the photovoltaic grid is analyzed to determine the harmonic interference characteristic value of each photovoltaic inverter. The external interference index of each photovoltaic inverter is determined based on the characteristic values ​​of light intensity variation and harmonic interference of each inverter. The analysis of the circuit impedance and reactive power changes corresponding to each photovoltaic inverter in the photovoltaic power grid determines the internal interference index of each photovoltaic inverter, including: During the monitoring period, the degree of reactive power fluctuation of each photovoltaic inverter is analyzed, and the power fluctuation characteristic value of each photovoltaic inverter is determined. The circuit impedance of each photovoltaic inverter is normalized to obtain the impedance characteristic value of each photovoltaic inverter. Based on the power fluctuation characteristic value and impedance characteristic value of each photovoltaic inverter, the internal interference index of each photovoltaic inverter is determined. The process of correcting the initial droop coefficient corresponding to the external interference index and internal interference index of each photovoltaic inverter to obtain the target droop coefficient of each photovoltaic inverter includes: Based on the external interference index of each photovoltaic inverter, an external interference correction value is determined for each photovoltaic inverter. When the external interference index is greater than or equal to the index threshold, the corresponding external interference correction value is a first value. When the external interference index is less than the index threshold, the corresponding external interference correction value is a second value. The first value is greater than the second value, and the second value is greater than or equal to 1. Calculate the product of the external interference correction value, the internal interference index and the corresponding initial droop coefficient for each photovoltaic inverter to obtain the target droop coefficient for each photovoltaic inverter.

2. The reactive power and voltage control method for a photovoltaic inverter according to claim 1, characterized in that, During the monitoring period, the changes in irradiance of the corresponding irradiated areas of each photovoltaic inverter in the photovoltaic grid at adjacent times are analyzed to determine multiple irradiance variation factors corresponding to each photovoltaic inverter, including: During the monitoring period, the absolute difference in light intensity of the illuminated area corresponding to each photovoltaic inverter at adjacent times is calculated to obtain multiple light intensity change values ​​corresponding to each photovoltaic inverter. Among the multiple light intensity change values ​​corresponding to each photovoltaic inverter, the ratio of each light intensity change value corresponding to each photovoltaic inverter to the light intensity at the corresponding monitoring time is calculated to obtain multiple light intensity change factors corresponding to each photovoltaic inverter.

3. The reactive power and voltage control method for a photovoltaic inverter according to claim 1, characterized in that, During the monitoring period, the proportion of harmonic energy in the monitoring voltage signals of each photovoltaic inverter in the photovoltaic grid is analyzed to determine the harmonic interference characteristic value of each photovoltaic inverter, including: During the monitoring period, the monitoring voltage signal of each photovoltaic inverter is subjected to fast Fourier transform to obtain the voltage spectrum data of each photovoltaic inverter. Based on the voltage spectrum data of each photovoltaic inverter, determine the fundamental voltage energy and total voltage energy of each photovoltaic inverter; Calculate the difference between the total voltage energy and the fundamental voltage energy of each photovoltaic inverter to obtain the voltage harmonic energy of each photovoltaic inverter; Calculate the ratio of voltage harmonic energy to total voltage energy for each photovoltaic inverter to obtain the harmonic interference characteristic value for each photovoltaic inverter.

4. The reactive voltage control method for a photovoltaic inverter according to claim 1, characterized in that, The determination of the external interference index for each photovoltaic inverter based on its light intensity variation characteristic value and harmonic interference characteristic value includes: The light intensity variation characteristic value of each photovoltaic inverter is normalized to obtain the light intensity variation normalized value of each photovoltaic inverter, wherein the light intensity variation characteristic value and the light intensity variation normalized value are positively correlated. The normalized value of light intensity variation and the harmonic interference characteristic value of each photovoltaic inverter are weighted and calculated to obtain the external interference index of each photovoltaic inverter. The weight of the harmonic interference characteristic value is greater than the weight of the normalized value of light intensity variation.

5. The reactive voltage control method for a photovoltaic inverter according to claim 1, characterized in that, During the monitoring period, the fluctuation degree of reactive power of each photovoltaic inverter is analyzed, and the power fluctuation characteristic value of each photovoltaic inverter is determined, including: During the monitoring period, the dispersion coefficient of reactive power of each photovoltaic inverter is determined as the power fluctuation characteristic value of each photovoltaic inverter.

6. The reactive voltage control method for a photovoltaic inverter according to claim 1, characterized in that, The power fluctuation characteristic value is positively correlated with the internal interference index, and the impedance characteristic value is negatively correlated with the internal interference index.

7. A reactive voltage control system for a photovoltaic inverter, used to implement the reactive voltage control method for a photovoltaic inverter as described in any one of claims 1-6, characterized in that, The system includes: The external interference analysis module analyzes the changes in light intensity in the corresponding light areas of each photovoltaic inverter in the photovoltaic grid, as well as the harmonic interference intensity in the monitoring voltage signals of each photovoltaic inverter in the photovoltaic grid, and determines the external interference index of each photovoltaic inverter. The internal interference analysis module is used to analyze the circuit impedance and reactive power changes of each photovoltaic inverter in the photovoltaic grid and determine the internal interference index of each photovoltaic inverter. The droop coefficient determination module is used to correct the corresponding initial droop coefficient based on the external interference index and internal interference index of each photovoltaic inverter, so as to obtain the target droop coefficient of each photovoltaic inverter. The control module is used to control the reactive voltage of the photovoltaic inverters in the photovoltaic grid according to the target droop coefficient of each photovoltaic inverter.

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