Distribution line voltage detection method based on photovoltaic inverter

Abstract

The invention discloses a power distribution line voltage detection method based on photovoltaic inverters, and relates to the technical field of voltage detection, a plurality of voltage detection access points are selected on a power distribution line, the photovoltaic inverters are deployed to collect power characterization data of each line segment where the current power distribution line is located and equipment operation data of the photovoltaic inverters, and the power characterization data and the equipment operation data of the photovoltaic inverters are acquired; and constructing an equivalent circuit model of the current distribution line, and inputting the real-time periodic detection voltage of each voltage detection access point of the current distribution line in a data acquisition period into the equivalent circuit model to obtain the voltage periodic evolution trend of each voltage detection access point on the distribution line. According to the method, voltage detection access points of which the voltage periodic evolution trend does not conform to the normal trend are screened out, a voltage early warning instruction is generated and sent back to the photovoltaic inverter, the photovoltaic inverter adjusts the line voltage of the corresponding line segment, whether the photovoltaic inverter successfully completes the adjustment of the line voltage is judged, and if yes, the voltage detection access points of which the voltage periodic evolution trend does not conform to the normal trend are judged. And determining whether to perform auxiliary voltage regulation or not according to a judgment result.

Description

Technical Field

[0001] The present invention relates to the technical field of voltage detection, and in particular to a method for detecting voltage of a power distribution line based on a photovoltaic inverter. Background Art

[0002] In the existing distribution line management technology, voltage stability and regulation are one of the key factors to ensure the quality of power supply. Only when the distribution line is at a stable and required voltage can the distribution line be integrated into the power grid. However, traditional voltage regulation methods often rely on limited monitoring points, which leads to incomplete monitoring of the distribution line voltage status and low regulation efficiency. Especially after the distributed photovoltaic power generation system is connected to the distribution network, the voltage fluctuation is more complicated, which puts higher requirements on the voltage regulation technology.

[0003] At present, although photovoltaic inverters have certain data collection and control capabilities, they are mainly used in maximum power point tracking (MPPT) and power conversion, and have not fully utilized their potential in voltage monitoring and control. In addition, the existing voltage monitoring lacks in-depth analysis of the voltage cycle evolution trend, and cannot timely detect and warn of voltage anomalies, which makes it impossible to achieve accurate voltage control. Therefore, a voltage monitoring method is urgently needed to ensure that distribution lines can be efficiently connected to the power grid. Summary of the invention

[0004] In order to solve the above problems, the object of the present invention is to provide a distribution line voltage detection method based on a photovoltaic inverter.

[0005] The purpose of the present invention can be achieved by the following technical solution: A method for detecting voltage of a distribution line based on a photovoltaic inverter comprises the following steps: Step S1: Select a number of voltage detection access points on the distribution line, and deploy a photovoltaic inverter at each voltage detection access point, so that the photovoltaic inverter collects the power characterization data of the line segment where the current distribution line is located, as well as the equipment operation data of the photovoltaic inverter itself; Step S2: constructing an equivalent circuit model corresponding to the current distribution line according to the power characterization data and the equipment operation data; Step S3: setting a data collection cycle, inputting the corresponding real-time periodic detection voltage at each voltage detection access point of the current distribution line within a data collection cycle into the equivalent circuit model, and then obtaining the voltage periodic evolution trend of each voltage detection access point on the distribution line from the equivalent circuit model; Step S4: Screen out the voltage detection access points whose voltage cycle evolution trend does not conform to the normal trend, generate corresponding voltage warning instructions, and transmit the voltage warning instructions back to the photovoltaic inverter, so that the photovoltaic inverter adjusts the line voltage of the corresponding line segment; Step S5: determining whether the photovoltaic inverter has successfully completed the adjustment of the line voltage on the corresponding line segment, and determining whether to perform auxiliary voltage regulation based on the determination result.

[0006] Furthermore, the process of selecting a number of voltage detection access points on the distribution line and deploying a photovoltaic inverter at each voltage detection access point includes: The distribution line includes a line section corresponding to the main distribution line and a line section corresponding to the branch distribution line. Voltage detection access points are selected on the main distribution line and the branch distribution line respectively. Several voltage detection access points on the line sections corresponding to the main distribution line and the branch distribution line are numbered respectively, and the numbers are recorded as i and j respectively, wherein i=1, 2, 3, ..., n, j=1, 2, 3, ..., m, and n and m are both natural numbers greater than 0; A photovoltaic inverter is deployed at each voltage detection access point, and it is determined whether the photovoltaic inverter is in normal working condition. If so, no operation is performed. If not, the working information of the photovoltaic inverter in abnormal working condition is copied to generate an inverter working report, and sent to the preset maintenance database. The fault type of the current photovoltaic inverter and the corresponding maintenance parameters for solving the current fault are matched from the maintenance database, and the maintenance parameters are transmitted back to the corresponding photovoltaic inverter. The photovoltaic inverter performs maintenance according to the maintenance parameters until the photovoltaic inverter is transformed into a normal working state.

[0007] Furthermore, the process of collecting the power characterization data of the line segment where the current distribution line is located and the equipment operation data of the photovoltaic inverter itself includes: When the photovoltaic inverters at all voltage detection access points are in normal working state, a sampling period corresponding to each photovoltaic inverter is set. In each sampling period, the photovoltaic inverters deployed in each line segment are used to collect power characterization data under the corresponding line segment; Power characterization data includes line impedance, line load, and harmonic frequency; In each line segment where the distribution line is located, the photovoltaic inverter collects its corresponding equipment operation data in real time. The equipment operation data includes the inverter output voltage, inverter output current and inverter output power.

[0008] Furthermore, the process of constructing an equivalent circuit model corresponding to the current distribution line according to the power characterization data and the equipment operation data includes: According to the line topology structure of the current distribution line, a corresponding initial topology circuit sub-model is constructed for a number of line segments included in the current distribution line, and the line impedance, line load and harmonic frequency corresponding to each line segment are used as the first modeling filling data, and the inverter output voltage, inverter output current and inverter output power of the photovoltaic inverter deployed corresponding to each line segment are used as the second modeling filling data; Establishing a functional relationship expression of the line impedance, line load and harmonic frequency corresponding to each line segment over time, establishing a functional relationship expression of the inverter output voltage, inverter output current and inverter output power of the photovoltaic inverter corresponding to each line segment over time, and establishing a functional expression of the mutual influence of power characterization data and equipment operation data on the line voltage corresponding to the current line segment, and performing model training on the initial topology circuit sub-model of the corresponding line segment based on all functional relationship expressions of each line segment, the first modeling filling data and the second modeling filling data; After the model training is completed, the initial topological circuit sub-model corresponding to each line segment is converted into the final equivalent topological circuit sub-model under the corresponding line segment, and the equivalent topological circuit sub-models of all line segments under the current distribution line are fused to construct the equivalent circuit model corresponding to the current distribution line.

[0009] Furthermore, a data collection cycle is set, and the real-time periodic detection voltage corresponding to each voltage detection access point of the current distribution line within a data collection cycle is input into the equivalent circuit model, and then the voltage periodic evolution trend of each voltage detection access point on the distribution line is obtained from the equivalent circuit model. The process includes: Set the data collection period and record it as T 采集 ; Yes 采集 =[t1, t2], where t1 is the start time of the data collection cycle, and t2 is the end time of the data collection cycle; Set the detection frequency, and record the detection frequency as f, where f is a natural number greater than 0; At the start time of the cycle corresponding to t1, according to the detection frequency f, the voltage of several frequencies corresponding to each voltage detection access point where the current distribution line is located is collected, and the collection time corresponding to each frequency voltage is recorded. At the end time of the cycle corresponding to t2, the collection of several frequency voltages at several collection times corresponding to the current data collection cycle is completed; Summarize all the frequency voltages of each voltage detection access point in a data acquisition cycle, and then use them as the real-time periodic detection voltage of the corresponding voltage detection access point, and input the real-time periodic detection voltage of each voltage detection access point into the equivalent circuit model; The equivalent circuit model maps the frequency voltages corresponding to several acquisition moments to the model coordinate system, and maps the critical voltage threshold corresponding to the current line segment obtained by the equivalent circuit model to the model coordinate system, and draws a voltage change trend diagram of the corresponding line segment on the model coordinate system according to the frequency voltages at several acquisition moments; The critical voltage threshold includes a critical minimum voltage threshold and a critical maximum voltage threshold; The acquisition times above the critical maximum voltage threshold and the acquisition times below the critical minimum voltage threshold in the voltage change trend diagram of each line segment are counted, and the time period composed of all acquisition times above the critical maximum voltage threshold and below the critical minimum voltage threshold is summarized, so as to obtain the voltage fluctuation duration when the corresponding voltage of each line segment is abnormal.

[0010] Furthermore, the voltage detection access points whose voltage cycle evolution trend does not conform to the normal trend are screened out, and corresponding voltage warning instructions are generated, and the voltage warning instructions are transmitted back to the photovoltaic inverter. The photovoltaic inverter adjusts the line voltage of the corresponding line segment. The process includes: Set the critical fluctuation duration threshold corresponding to the voltage fluctuation duration; When the voltage fluctuation duration of a voltage detection access point corresponding to a certain line segment in the distribution line is greater than or equal to the critical fluctuation duration threshold, it is judged that the voltage cycle evolution trend of the current voltage detection access point does not conform to the normal trend; when the voltage fluctuation duration of a voltage detection access point corresponding to a certain line segment in the distribution line is less than the critical fluctuation duration threshold, it is judged that the voltage cycle evolution trend of the current voltage detection access point conforms to the normal trend; When the voltage cycle evolution trend of the voltage detection access point does not conform to the normal trend, a corresponding voltage warning instruction is generated according to the number of the line segment where the voltage detection access point is located, and the voltage warning instruction is transmitted back to the photovoltaic inverter deployed at the corresponding line segment; When the photovoltaic inverter receives the voltage warning instruction, it adjusts the active power and reactive power of the current line segment, thereby completing the adjustment of the line voltage corresponding to the current line segment.

[0011] Furthermore, the process of determining whether the photovoltaic inverter has successfully completed the adjustment of the line voltage on the corresponding line segment includes: Set the grid-connected voltage range corresponding to when the distribution line is connected to the grid; For each line segment included in the distribution line, after adjusting the active power and reactive power within the upper and lower limit power range of the active power and reactive power configured by the photovoltaic inverter, if the line voltage of the line segment is still not in the grid-connected voltage interval, it is judged that the photovoltaic inverter has not successfully completed the adjustment of the line voltage on the corresponding line segment; if the line voltage of the line segment is in the grid-connected voltage interval, it is judged that the photovoltaic inverter has successfully completed the adjustment of the line voltage on the corresponding line segment.

[0012] Furthermore, the process of determining whether to perform auxiliary voltage regulation according to the judgment result includes: If the line voltage of a certain line segment is not in the grid-connected voltage interval, the line voltage of the corresponding line segment does not meet the grid-connected voltage; otherwise, the line voltage of the corresponding line segment meets the grid-connected voltage; When the line voltage of a line segment in the distribution line does not meet the grid-connected voltage, it is determined that the corresponding line segment needs auxiliary voltage regulation. When the line voltage of all line segments in the distribution line meets the grid-connected voltage, it is determined that the current distribution line can be connected to the grid.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. By deploying photovoltaic inverters at multiple voltage detection access points on the distribution line, it is possible to comprehensively collect power characterization data and equipment operation data of each line segment, realize comprehensive monitoring of the voltage state of the distribution network, and build an equivalent circuit model. It can more accurately simulate and analyze the voltage state of each voltage detection access point on the distribution line, providing a solid theoretical basis for voltage regulation.

[0014] 2. By analyzing the voltage cycle evolution trend, it is possible to predict potential voltage problems and take regulatory measures in advance to avoid the impact of abnormal voltage on the power grid and power-consuming equipment. It can screen out voltage detection access points with abnormal voltage cycle evolution trends, generate voltage warning instructions, and perform real-time voltage adjustment through photovoltaic inverters, thereby improving the response speed and accuracy of voltage regulation. It can determine whether the photovoltaic inverter has successfully completed the voltage adjustment, and decide whether to perform auxiliary voltage regulation based on the results to ensure that the final line voltage of the distribution line can meet the grid connection requirements, thereby successfully completing the operation of connecting the distribution line to the grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0016] like Figure 1 As shown, a distribution line voltage detection method based on a photovoltaic inverter includes the following steps: Step S1: Select a number of voltage detection access points on the distribution line, and deploy a photovoltaic inverter at each voltage detection access point, so that the photovoltaic inverter collects the power characterization data of the line segment where the current distribution line is located, as well as the equipment operation data of the photovoltaic inverter itself; Step S2: constructing an equivalent circuit model corresponding to the current distribution line according to the power characterization data and the equipment operation data; Step S3: setting a data collection cycle, inputting the corresponding real-time periodic detection voltage at each voltage detection access point of the current distribution line within a data collection cycle into the equivalent circuit model, and then obtaining the voltage periodic evolution trend of each voltage detection access point on the distribution line from the equivalent circuit model; Step S4: Screen out the voltage detection access points whose voltage cycle evolution trend does not conform to the normal trend, generate corresponding voltage warning instructions, and transmit the voltage warning instructions back to the photovoltaic inverter, so that the photovoltaic inverter adjusts the line voltage of the corresponding line segment; Step S5: determining whether the photovoltaic inverter has successfully completed the adjustment of the line voltage on the corresponding line segment, and determining whether to perform auxiliary voltage regulation based on the determination result.

[0017] It should be further explained that, in the specific implementation process, the process of selecting a number of voltage detection access points on the distribution line and deploying a photovoltaic inverter at each voltage detection access point includes: The distribution line includes line segments corresponding to the main distribution line and line segments corresponding to the branch distribution line, and corresponding voltage detection access points are selected on the main distribution line and the branch distribution line respectively, and then a plurality of voltage detection access points are selected on the distribution line; A number of voltage detection access points on the line segment corresponding to the main distribution line are numbered, and the number is recorded as i, then i = 1, 2, 3, ..., n, and a number of voltage detection access points on the line segment corresponding to the branch distribution line are numbered, and the number is recorded as j, then j = 1, 2, 3, ..., m, where n and m are both natural numbers greater than 0; A photovoltaic inverter is deployed at each voltage detection access point, and it is determined whether the photovoltaic inverter is in a normal working state. If so, no operation is performed. If not, the working information of the photovoltaic inverter currently in an abnormal working state is recorded, a corresponding inverter working report is generated, and the inverter working report is sent to a preset maintenance database; The fault type of the photovoltaic inverter currently in abnormal working state and the maintenance parameters corresponding to the current fault are matched from the maintenance database, and the maintenance parameters are transmitted back to the corresponding photovoltaic inverter. The photovoltaic inverter performs maintenance according to the maintenance parameters until the photovoltaic inverter is transformed into a normal working state.

[0018] It should be further explained that, in the specific implementation process, the process of the photovoltaic inverter collecting the power characterization data of the line segment where the current distribution line is located, as well as the equipment operation data of the photovoltaic inverter itself, includes: When the photovoltaic inverters at all voltage detection access points are in normal working state, a sampling period corresponding to each photovoltaic inverter is set. In each sampling period, the photovoltaic inverters deployed in each line segment are used to collect power characterization data under the corresponding line segment; The power characterization data includes line impedance, line load and harmonic frequency; The line impedance includes the line resistance and line reactance corresponding to each line segment in the distribution line; In each line segment where the distribution line is located, the photovoltaic inverter collects its corresponding equipment operation data in real time. The equipment operation data includes the inverter output voltage, inverter output current and inverter output power; For the line segments belonging to the main distribution line, the inverter output voltage, inverter output current and inverter output power corresponding to the photovoltaic inverter on the line segment are respectively marked as V[i], A[i] and W[i]; For the line segments belonging to the branch distribution lines, the inverter output voltage, inverter output current and inverter output power corresponding to the photovoltaic inverter on the line segments are respectively identified as V[j], A[j] and W[j]; Among them, for the power characterization data corresponding to each line segment, the number of the photovoltaic inverter on the line segment is associated and bound with its power characterization data as an identity authentication identifier of the power characterization data.

[0019] It should be further explained that, in the specific implementation process, the process of constructing the equivalent circuit model corresponding to the current distribution line according to the power characterization data and the equipment operation data includes: According to the line topology structure of the current distribution line, a corresponding initial topology circuit sub-model is constructed for a number of line segments included in the current distribution line, and the line impedance, line load and harmonic frequency corresponding to each line segment are used as the first modeling filling data, and the inverter output voltage, inverter output current and inverter output power of the photovoltaic inverter deployed corresponding to each line segment are used as the second modeling filling data; Establishing a functional relationship expression of the line impedance, line load and harmonic frequency corresponding to each line segment over time, establishing a functional relationship expression of the inverter output voltage, inverter output current and inverter output power of the photovoltaic inverter corresponding to each line segment over time, and establishing a functional expression of the mutual influence of power characterization data and equipment operation data on the line voltage corresponding to the current line segment, and performing model training on the initial topology circuit sub-model of the corresponding line segment based on all functional relationship expressions of each line segment, the first modeling filling data and the second modeling filling data; After the model training is completed, the initial topological circuit sub-model corresponding to each line segment is converted into the final equivalent topological circuit sub-model under the corresponding line segment, and the equivalent topological circuit sub-models of all line segments under the current distribution line are fused to construct the equivalent circuit model corresponding to the current distribution line.

[0020] Setting a model authentication index corresponding to the initial topology circuit sub-model of each line segment, the model authentication index includes a convergence interval corresponding to the model convergence rate, an accuracy range corresponding to the model accuracy, and a fitting interval corresponding to the model fitting rate; When the model convergence rate of the initial topology circuit sub-model corresponding to the line segment is in the convergence interval, the model accuracy is within the accuracy range, and the model fitting rate is in the fitting interval, the initial topology circuit sub-model corresponding to the current line segment is judged to have successfully completed model training. Otherwise, continue to iterate the initial topology circuit sub-model for model training until the three conditions are met at the same time, then stop model training.

[0021] It should be further explained that, in the specific implementation process, a data collection cycle is set, and the real-time periodic detection voltage corresponding to each voltage detection access point of the current distribution line within a data collection cycle is input into the equivalent circuit model, and then the voltage cycle evolution trend of each voltage detection access point on the distribution line is obtained from the equivalent circuit model. The process includes: Set the data collection period and record it as T 采集 ; Yes 采集 =[t1, t2], where t1 is the start time of the data collection cycle and t2 is the end time of the data collection cycle; Set the detection frequency, and record the detection frequency as f, where f is a natural number greater than 0; At the start time of the cycle corresponding to t1, according to the detection frequency f, the voltage of several frequencies corresponding to each voltage detection access point where the current distribution line is located is collected, and the collection time corresponding to each frequency voltage is recorded. At the end time of the cycle corresponding to t2, the collection of several frequency voltages at several collection times corresponding to the current data collection cycle is completed; Summarize all the frequency voltages of each voltage detection access point in a data acquisition cycle, and then use them as the real-time periodic detection voltage of the corresponding voltage detection access point, and input the real-time periodic detection voltage of each voltage detection access point into the equivalent circuit model; A voltage change trend graph of the real-time periodic detection voltage corresponding to each voltage detection access point is constructed by the equivalent circuit model. The voltage change trend graph is used to record the periodic evolution trend of the line voltage corresponding to the current voltage detection access point; The equivalent circuit model maps the frequency voltages corresponding to several acquisition moments to the model coordinate system, and maps the critical voltage threshold corresponding to the current line segment obtained by the equivalent circuit model to the model coordinate system. According to the frequency voltages at several acquisition moments, a voltage change trend diagram of the corresponding line segment is drawn on the model coordinate system. The critical voltage threshold comprises a critical minimum voltage threshold and a critical maximum voltage threshold; The critical voltage threshold corresponding to each line segment in the distribution line is set by the equivalent circuit model according to the line impedance, line load and harmonic frequency under the corresponding line segment, and the inverter output voltage, inverter output current and inverter output power corresponding to the photovoltaic inverter, that is, the critical voltage threshold corresponding to each line segment is not exactly the same.

[0022] Count the acquisition times above the critical maximum voltage threshold and the acquisition times below the critical minimum voltage threshold in the voltage change trend diagram of each line segment, and summarize the time period composed of all acquisition times above the critical maximum voltage threshold and below the critical minimum voltage threshold, so as to obtain the voltage fluctuation duration when the corresponding voltage of each line segment is abnormal; In the voltage change trend diagram corresponding to each line segment, all acquisition moments when the frequency voltage is less than or equal to the critical maximum voltage threshold and greater than or equal to the critical minimum voltage threshold are marked as normal voltage moments, and the time period composed of all normal voltage moments is summarized as the voltage stabilization time of the corresponding line segment.

[0023] It should be noted that the line voltage of the line segment at all the collection moments corresponding to the voltage fluctuation duration is in an abnormal state, and it is necessary to adjust its line voltage so that the final line voltage of the current line segment meets the grid-connected voltage for the distribution line to be connected to the grid. The line voltage of the line segment at all the collection moments corresponding to the voltage stabilization duration is in a normal state, and there is no need to make any adjustment to its line voltage, and the line voltage of the line segment has met the grid-connected voltage.

[0024] It should be further explained that, in the specific implementation process, the voltage detection access points whose voltage cycle evolution trend does not conform to the normal trend are screened out, and the corresponding voltage warning instructions are generated, and the voltage warning instructions are transmitted back to the photovoltaic inverter. The photovoltaic inverter adjusts the line voltage of the corresponding line segment. The process includes: Set the critical fluctuation duration threshold corresponding to the voltage fluctuation duration; When the voltage fluctuation duration of a voltage detection access point corresponding to a certain line segment in the distribution line is greater than or equal to the critical fluctuation duration threshold, it is judged that the voltage cycle evolution trend of the current voltage detection access point does not conform to the normal trend; when the voltage fluctuation duration of a voltage detection access point corresponding to a certain line segment in the distribution line is less than the critical fluctuation duration threshold, it is judged that the voltage cycle evolution trend of the current voltage detection access point conforms to the normal trend; When the voltage cycle evolution trend of the voltage detection access point does not conform to the normal trend, a corresponding voltage warning instruction is generated according to the number of the line segment where the voltage detection access point is located, and the voltage warning instruction is transmitted back to the photovoltaic inverter deployed at the corresponding line segment; When the photovoltaic inverter receives the voltage warning instruction, the photovoltaic inverter adjusts the active power and reactive power of the current line segment, wherein the photovoltaic inverter pre-configures the upper and lower limit power ranges of the active power and reactive power; The acquisition time when the voltage of all frequencies in the voltage change trend diagram corresponding to the line segment is less than the critical minimum voltage threshold is marked as the voltage increase time, and the acquisition time when the voltage of all frequencies in the line segment is greater than the critical maximum voltage threshold is marked as the voltage reduction time; At the boost moment, the active power regulation performed by the photovoltaic inverter is: increasing the active power output, the photovoltaic inverter increases the active power output of the line segment at the current moment, and then increases the frequency voltage at the corresponding moment, until the frequency voltage at the current moment is between the critical minimum voltage threshold and the critical maximum voltage threshold; the corresponding reactive power regulation is: the photovoltaic inverter provides capacitive reactive power to the line segment at the current moment; At the voltage reduction moment, the active power regulation performed by the photovoltaic inverter is: reducing the active power output, the photovoltaic inverter reduces the active power output of the line segment at the current moment, and then reduces the frequency voltage at the corresponding moment, until the frequency voltage at the current moment is between the critical minimum voltage threshold and the critical maximum voltage threshold; the corresponding reactive power regulation is: the photovoltaic inverter provides inductive reactive power to the line segment at the current moment; When the frequency voltage of the line segment at all boost moments and voltage reduction moments is adjusted, the adjustment of the line voltage corresponding to the current line segment is completed.

[0025] It should be noted that photovoltaic inverters play a vital regulating role in distribution lines. Photovoltaic inverters convert the direct current generated by photovoltaic panels that play a role in generating electricity in distribution lines into alternating current, and adjust the line voltage of the line segment in which they are located in the distribution line so that the final voltage of the distribution line meets the grid-connected voltage, allowing the distribution line to be successfully connected to the power grid.

[0026] It should be further explained that, in the specific implementation process, the process of judging whether the photovoltaic inverter has successfully completed the adjustment of the line voltage on the corresponding line segment includes: Set the grid-connected voltage range corresponding to when the distribution line is connected to the grid; For each line segment included in the distribution line, after adjusting the active power and reactive power within the upper and lower limit power range of the active power and reactive power configured by the photovoltaic inverter, if the line voltage of the line segment is still not in the grid-connected voltage interval, it is judged that the photovoltaic inverter has not successfully completed the adjustment of the line voltage on the corresponding line segment; if the line voltage of the line segment is in the grid-connected voltage interval, it is judged that the photovoltaic inverter has successfully completed the adjustment of the line voltage on the corresponding line segment.

[0027] It should be further explained that, in the specific implementation process, the process of determining whether to perform auxiliary voltage regulation according to the judgment result includes: If the line voltage of a certain line segment is not in the grid-connected voltage interval, the line voltage of the corresponding line segment does not meet the grid-connected voltage; otherwise, the line voltage of the corresponding line segment meets the grid-connected voltage; When the line voltage of a line segment in the distribution line does not meet the grid-connected voltage, it is determined that the corresponding line segment needs to be regulated by auxiliary voltage. When the line voltage of all line segments in the distribution line meets the grid-connected voltage, it is determined that the current distribution line can be connected to the grid. The content of auxiliary voltage regulation is: install an intelligent distribution terminal for all line segments in the distribution line whose line voltage does not meet the grid-connected voltage. The intelligent distribution terminal changes the line voltage of the corresponding line segment by changing the line resistance and line reactance on the line segment where it is installed. When the line voltage is in the grid-connected voltage interval corresponding to the grid-connected voltage, the auxiliary voltage regulation corresponding to the current line segment is stopped. When the line voltages of all line segments in the distribution line meet the grid-connected voltage, the auxiliary voltage regulation is ended and the distribution line is connected to the power grid.

[0028] The above embodiments are only used to illustrate the technical method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical method of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A distribution line voltage detection method based on photovoltaic inverter, characterized in that: The following steps are involved: Step S1: Select a number of voltage detection access points on the distribution line, and deploy a photovoltaic inverter at each voltage detection access point, so that the photovoltaic inverter collects the power characterization data of the line segment where the current distribution line is located, as well as the equipment operation data of the photovoltaic inverter itself; Step S2: constructing an equivalent circuit model corresponding to the current distribution line according to the power characterization data and the equipment operation data; Step S3: setting a data collection cycle, inputting the corresponding real-time periodic detection voltage at each voltage detection access point of the current distribution line within a data collection cycle into the equivalent circuit model, and then obtaining the voltage periodic evolution trend of each voltage detection access point on the distribution line from the equivalent circuit model; Step S4: Screen out the voltage detection access points whose voltage cycle evolution trend does not conform to the normal trend, generate corresponding voltage warning instructions, and transmit the voltage warning instructions back to the photovoltaic inverter, so that the photovoltaic inverter adjusts the line voltage of the corresponding line segment; Step S5: determining whether the photovoltaic inverter has successfully completed the adjustment of the line voltage on the corresponding line segment, and determining whether to perform auxiliary voltage regulation based on the determination result.

2. A method for detecting voltage of a distribution line based on a photovoltaic inverter according to claim 1, characterized in that: The process of selecting several voltage detection access points on the distribution line and deploying a photovoltaic inverter at each voltage detection access point includes: The distribution line includes a line section corresponding to the main distribution line and a line section corresponding to the branch distribution line. Voltage detection access points are selected on the main distribution line and the branch distribution line respectively. Several voltage detection access points on the line sections corresponding to the main distribution line and the branch distribution line are numbered respectively, and the numbers are recorded as i and j respectively, wherein i=1, 2, 3, ..., n, j=1, 2, 3, ..., m, and n and m are both natural numbers greater than 0; A photovoltaic inverter is deployed at each voltage detection access point, and it is determined whether the photovoltaic inverter is in normal working condition. If so, no operation is performed. If not, the working information of the photovoltaic inverter in abnormal working condition is copied to generate an inverter working report, and sent to the preset maintenance database. The fault type of the current photovoltaic inverter and the corresponding maintenance parameters for solving the current fault are matched from the maintenance database, and the maintenance parameters are transmitted back to the corresponding photovoltaic inverter. The photovoltaic inverter performs maintenance according to the maintenance parameters until the photovoltaic inverter is transformed into a normal working state.

3. A method for detecting voltage of a distribution line based on a photovoltaic inverter according to claim 2, characterized in that: The process of collecting the power characterization data of the line segment where the current distribution line is located and the equipment operation data of the photovoltaic inverter itself includes: When the photovoltaic inverters at all voltage detection access points are in normal working state, a sampling period corresponding to each photovoltaic inverter is set. In each sampling period, the photovoltaic inverters deployed in each line segment are used to collect power characterization data under the corresponding line segment; Power characterization data includes line impedance, line load, and harmonic frequency; In each line segment where the distribution line is located, the photovoltaic inverter collects its corresponding equipment operation data in real time. The equipment operation data includes the inverter output voltage, inverter output current and inverter output power.

4. A method for detecting voltage of a distribution line based on a photovoltaic inverter according to claim 3, characterized in that: The process of constructing an equivalent circuit model corresponding to the current distribution line based on power characterization data and equipment operation data includes: According to the line topology structure of the current distribution line, a corresponding initial topology circuit sub-model is constructed for a number of line segments included in the current distribution line, and the line impedance, line load and harmonic frequency corresponding to each line segment are used as the first modeling filling data, and the inverter output voltage, inverter output current and inverter output power of the photovoltaic inverter deployed corresponding to each line segment are used as the second modeling filling data; Establishing a functional relationship expression of the line impedance, line load and harmonic frequency corresponding to each line segment over time, establishing a functional relationship expression of the inverter output voltage, inverter output current and inverter output power of the photovoltaic inverter corresponding to each line segment over time, and establishing a functional expression of the mutual influence of power characterization data and equipment operation data on the line voltage corresponding to the current line segment, and performing model training on the initial topology circuit sub-model of the corresponding line segment based on all functional relationship expressions of each line segment, the first modeling filling data and the second modeling filling data; After the model training is completed, the initial topological circuit sub-model corresponding to each line segment is converted into the final equivalent topological circuit sub-model under the corresponding line segment, and the equivalent topological circuit sub-models of all line segments under the current distribution line are fused to construct the equivalent circuit model corresponding to the current distribution line.

5. A method for detecting voltage of a distribution line based on a photovoltaic inverter according to claim 4, characterized in that: The process of setting a data collection cycle, inputting the corresponding real-time periodic detection voltage at each voltage detection access point of the current distribution line within a data collection cycle into the equivalent circuit model, and then obtaining the voltage periodic evolution trend of each voltage detection access point on the distribution line from the equivalent circuit model includes: Set the data collection period and record it as T 采集 ; Yes 采集 =[t1, t2], where t1 is the start time of the data collection cycle, and t2 is the end time of the data collection cycle; Set the detection frequency, and record the detection frequency as f, where f is a natural number greater than 0; At the start time of the cycle corresponding to t1, according to the detection frequency f, the voltage of several frequencies corresponding to each voltage detection access point where the current distribution line is located is collected, and the collection time corresponding to each frequency voltage is recorded. At the end time of the cycle corresponding to t2, the collection of several frequency voltages at several collection times corresponding to the current data collection cycle is completed; Summarize all the frequency voltages of each voltage detection access point in a data acquisition cycle, and then use them as the real-time periodic detection voltage of the corresponding voltage detection access point, and input the real-time periodic detection voltage of each voltage detection access point into the equivalent circuit model; The equivalent circuit model maps the frequency voltages corresponding to several acquisition moments to the model coordinate system, and maps the critical voltage threshold corresponding to the current line segment obtained by the equivalent circuit model to the model coordinate system, and draws a voltage change trend diagram of the corresponding line segment on the model coordinate system according to the frequency voltages at several acquisition moments; The critical voltage threshold includes a critical minimum voltage threshold and a critical maximum voltage threshold; The acquisition times above the critical maximum voltage threshold and the acquisition times below the critical minimum voltage threshold in the voltage change trend diagram of each line segment are counted, and the time period composed of all acquisition times above the critical maximum voltage threshold and below the critical minimum voltage threshold is summarized, so as to obtain the voltage fluctuation duration when the corresponding voltage of each line segment is abnormal.

6. A method for detecting voltage of a distribution line based on a photovoltaic inverter according to claim 5, characterized in that: The process of selecting voltage detection access points whose voltage cycle evolution trend does not conform to the normal trend, generating corresponding voltage warning instructions, transmitting the voltage warning instructions back to the photovoltaic inverter, and adjusting the line voltage of the corresponding line segment by the photovoltaic inverter includes: Set the critical fluctuation duration threshold corresponding to the voltage fluctuation duration; When the voltage fluctuation duration of a voltage detection access point corresponding to a certain line segment in the distribution line is greater than or equal to the critical fluctuation duration threshold, it is judged that the voltage cycle evolution trend of the current voltage detection access point does not conform to the normal trend; when the voltage fluctuation duration of a voltage detection access point corresponding to a certain line segment in the distribution line is less than the critical fluctuation duration threshold, it is judged that the voltage cycle evolution trend of the current voltage detection access point conforms to the normal trend; When the voltage cycle evolution trend of the voltage detection access point does not conform to the normal trend, a corresponding voltage warning instruction is generated according to the number of the line segment where the voltage detection access point is located, and the voltage warning instruction is transmitted back to the photovoltaic inverter deployed at the corresponding line segment; When the photovoltaic inverter receives the voltage warning instruction, it adjusts the active power and reactive power of the current line segment, thereby completing the adjustment of the line voltage corresponding to the current line segment.

7. A method for detecting voltage of a power distribution line based on a photovoltaic inverter according to claim 6, characterized in that: The process of judging whether the photovoltaic inverter has successfully completed the adjustment of the line voltage on the corresponding line segment includes: Set the grid-connected voltage range corresponding to when the distribution line is connected to the grid; For each line segment included in the distribution line, after adjusting the active power and reactive power within the upper and lower limit power range of the active power and reactive power configured by the photovoltaic inverter, if the line voltage of the line segment is still not in the grid-connected voltage interval, it is judged that the photovoltaic inverter has not successfully completed the adjustment of the line voltage on the corresponding line segment; if the line voltage of the line segment is in the grid-connected voltage interval, it is judged that the photovoltaic inverter has successfully completed the adjustment of the line voltage on the corresponding line segment.

8. A method for detecting voltage of a power distribution line based on a photovoltaic inverter according to claim 7, characterized in that: The process of determining whether to perform auxiliary voltage regulation based on the judgment result includes: If the line voltage of a certain line segment is not in the grid-connected voltage interval, the line voltage of the corresponding line segment does not meet the grid-connected voltage; otherwise, the line voltage of the corresponding line segment meets the grid-connected voltage; When the line voltage of a line segment in the distribution line does not meet the grid-connected voltage, it is determined that the corresponding line segment needs auxiliary voltage regulation. When the line voltage of all line segments in the distribution line meets the grid-connected voltage, it is determined that the current distribution line can be connected to the grid.

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