A voltage and power self-adaptive control method for photovoltaic access to a power distribution network

Abstract

The application relates to a voltage and power self-adaptive control method and system for photovoltaic access to a power distribution network, which comprises the following steps: adjusting the power output of a photovoltaic power station according to active power and reactive power instructions issued by a regulation center; and adjusting the reactive power output of a photovoltaic inverter according to the voltage of a grid-connected point. The technical scheme provided by the application can self-adaptively adjust the active and reactive power outputs after the photovoltaic receives the instructions issued by the regulation center, and can provide reactive power compensation for the power grid according to the node voltage out-of-limit information when no instruction is issued, so that the safe operation level of the power grid is improved.

Description

Technical Field

[0001] This invention relates to a voltage and power adaptive control method for photovoltaic grid connection, belonging to the field of power system automation technology. Background Technology

[0002] With the increasing proportion of distributed photovoltaic (PV) power grids being connected to the distribution network, distributed PV has become an indispensable regulatory resource.

[0003] In traditional distributed photovoltaic (PV) grid-connected systems, most controllers suppress grid voltage and frequency fluctuations by controlling the active and reactive power outputs of the PV inverters. However, these controllers cannot adaptively adjust their control modes according to changes in grid conditions.

[0004] Currently, there is no technology that can adaptively adjust the photovoltaic control mode based on grid demand and photovoltaic operating status, thereby adaptively controlling voltage, reactive power, and active power. Summary of the Invention

[0005] Purpose of the invention: To address the shortcomings of existing technologies, the purpose of this invention is to propose a voltage and power adaptive control method for photovoltaic grid integration. This method provides reactive power compensation to the grid when voltage disturbances occur. After receiving instructions from the control center, it can adaptively adjust the power output to improve the safe operation level of the grid.

[0006] Technical solution: A voltage and power adaptive control method for photovoltaic grid connection, the control method specifically includes the following steps:

[0007] Step 1: Determine the control mode based on the grid connection point voltage information, the instructions issued by the control center, and the photovoltaic operating status;

[0008] Step 2: In power control mode, after receiving instructions from the control center, the photovoltaic power station determines the power adjustment amount;

[0009] Step 3: In voltage control mode, determine the reactive power regulation of the photovoltaic power station.

[0010] Furthermore, in step 1, determining the control mode based on grid connection point voltage information, instructions issued by the control center, and photovoltaic operating status specifically includes:

[0011] The input signals are hierarchically classified to determine the input value of the photovoltaic operating status as dP(t) / dt, the input values ​​of the commands issued by the control center as ΔP and ΔQ, and the grid connection point voltage information as ΔV(t).

[0012] Based on the obtained input signal, the input signal is fuzzified;

[0013] Design membership functions and determine control modes;

[0014] Where dP(t) / dt is the rate of change of photovoltaic active power, ΔP and ΔQ are the changes in active power and reactive power, and ΔV(t) is the difference between the grid connection point voltage and the reference voltage.

[0015] Furthermore, the priority of the input signals is determined according to the following rules:

[0016] ① Instructions issued by the control center have the highest priority and will be responded to first;

[0017] ② The grid connection point voltage signal has the next highest priority and will be analyzed for its adaptability to the photovoltaic operating status;

[0018] The input signal is blurred using the following function:

[0019] The safe voltage range for the grid connection point is set to [0.97U]. ref 1.03U ref The upper limit of voltage is 1.07U. ref The lower limit is 0.93U. ref Five fuzzy subsets are selected: undervoltage VUV, low voltage UV, normal voltage N, high voltage OV, and overvoltage VOV; the universe of discourse is [-X,X], where X is the maximum voltage deviation of the power grid, and it is fuzzified using a trigonometric function.

[0020] The photovoltaic active power change rate dP(t) / dt is selected as the photovoltaic state signal, and five fuzzy subsets are selected: rapid decrease VL, decrease L, normal fluctuation N, increase H and rapid increase VH; the universe of discourse is [-Y,Y], where Y is the maximum active power fluctuation of the system, and it is fuzzified using a triangular function;

[0021] Design the membership function according to the following rules to determine the control mode:

[0022] The control center issues the highest priority instructions. When ΔP and ΔQ are not 0, the inverter is in power control mode.

[0023] Select the inverter reactive power output as the fuzzy language output quantity, and set 5 output modes: fast reactive power output HSQ, output reactive power SQ, normal operation N, reactive power absorption AQ, and fast reactive power absorption HAQ; both input quantities contain 5 fuzzy subsets, and a total of 25 rules need to be established. These 5 output modes are collectively referred to as voltage control modes.

[0024] Furthermore, in step 2, under power control mode, after receiving instructions from the control center, the photovoltaic power station determines the power adjustment amount, specifically including:

[0025] When a photovoltaic power station receives an active power regulation command, it determines the reactive power output regulation amount.

[0026] When a photovoltaic power station receives a reactive power regulation command, it determines the active power output regulation amount.

[0027] Furthermore, determining the reactive power output adjustment amount when the photovoltaic power station receives an active power command includes:

[0028] The reactive power output regulation ΔQ of the photovoltaic inverter is determined by the following formula. PV :

[0029]

[0030] In the formula, U PV U represents the voltage value at the photovoltaic grid connection point. ref S represents the reference voltage. PV This indicates the reactive voltage sensitivity value corresponding to this node.

[0031] Furthermore, determining the active power output adjustment amount when the photovoltaic power station receives a reactive power command includes:

[0032] The active voltage sensitivity matrix S is determined by the following formula. PV :

[0033]

[0034] In the formula, J Pδ J Qδ J PU J QU It is a submatrix of the Jacobian matrix;

[0035] The active power output regulation ΔP of a photovoltaic power station is determined by the following formula. PV :

[0036]

[0037] In the formula, U PV U represents the voltage value at the photovoltaic grid connection point. ref Indicates the reference voltage. This indicates the active voltage sensitivity value corresponding to this node.

[0038] Furthermore, in step 3, under voltage control mode, determining the reactive power regulation of the photovoltaic power station specifically includes:

[0039] Considering the fluctuation of photovoltaic power output, the low-voltage distribution nodes are divided into zones;

[0040] Identify key voltage nodes and key photovoltaic power plants within the zone;

[0041] Based on the voltage status of key nodes, determine the reactive power regulation of the photovoltaic power station.

[0042] Furthermore, the zoning process for low-voltage distribution network nodes includes:

[0043] The reactive voltage sensitivity matrix S of the distribution network is obtained by the following formula:

[0044] S = [J Qδ J Pδ -1 J PU -J QU ] -1

[0045] J Pδ J Qδ J PU J QU It is a submatrix of the Jacobian matrix;

[0046] The power flow calculation equations for the distribution network are as follows:

[0047]

[0048] In the formula: ΔQ and ΔP are the reactive power and active power injected into the node, and Δδ and ΔU are the changes in the node voltage phase angle and magnitude.

[0049] Under typical power flow conditions, the voltage values ​​at each node are:

[0050] U i =[U1,U2,...,U k ,...,U n-1 ] i

[0051] In the formula: k represents a node under power flow state i, U k This represents the voltage value at node k;

[0052] Assuming a typical power flow states are extracted, p i Let represent the statistical probability of power flow state i, then we define the correction coefficient for power flow state i at k nodes. for:

[0053]

[0054] Based on the reactive voltage sensitivity matrix S, the electrical distance matrix element d is calculated using the Euclidean distance method. ij :

[0055]

[0056] By calculating the correction values ​​for the electrical distance under each power flow condition, we obtain the electrical distance matrix D considering photovoltaic fluctuations:

[0057]

[0058] The partition objective function f is set as follows:

[0059]

[0060] In the formula, d inner d represents the electrical distance between nodes within a partition. out This represents the electrical distance between nodes outside the partition and nodes inside the partition, where α1 and α2 are weighting coefficients, and max represents finding the maximum value.

[0061] The distribution network nodes are partitioned according to the following procedure:

[0062] ① Initialize the distribution network, treating each node as a cluster;

[0063] ② Merge the two clusters with the smallest inter-cluster electrical distance in sequence, calculate the objective function value at this time, and form a new cluster;

[0064] ③ Randomly select a cluster connected to the newly generated partition and incorporate it into the partition. Calculate the objective function at this point. The partition result is when the objective function is maximized.

[0065] Furthermore, the process of locating key voltage nodes and key photovoltaic power plants within the partition includes:

[0066] Determine the critical voltage node using the following formula

[0067]

[0068] In the formula, i represents the i-th node partition obtained, k represents the voltage node in partition i, and max represents the maximum over-limit voltage.

[0069] Within the obtained partition, each node is divided into a set of normal voltage nodes and an overvoltage node set. The node with the most severe voltage over-limit in the k nodes of the i-th partition is identified and marked as a critical voltage node.

[0070] Key photovoltaic power plants are determined by the following formula.

[0071] Based on the reactive voltage sensitivity matrix S, identify the photovoltaic power station with the highest sensitivity corresponding to the key voltage node.

[0072]

[0073] In the formula, This indicates the obtained critical voltage node. represents an element in the reactive voltage sensitivity matrix, and max represents finding the maximum value.

[0074] Furthermore, determining the reactive power regulation of the photovoltaic power plant based on the voltage state of key nodes includes:

[0075] The reactive power regulation Q of a photovoltaic power station is determined by the following formula. need :

[0076]

[0077] In the formula, V i max For critical voltage node exceeding the limit, S max This refers to the reactive voltage sensitivity corresponding to key photovoltaic power plants.

[0078] Beneficial effects: After adding the adaptive controller to the photovoltaic control unit, it can reasonably adjust the active and reactive power output of the inverter according to the grid status and its own operating status, enhance the controllability of photovoltaic power output, suppress the voltage rise caused by photovoltaic grid connection, and enhance the stability of power system operation. Attached Figure Description

[0079] Figure 1 This is a flowchart of a voltage and power adaptive control method for photovoltaic grid connection according to the present invention;

[0080] Figure 2 This is a schematic diagram of the voltage and power adaptive control system structure for photovoltaic grid connection according to the present invention;

[0081] Figure 3 It is a fuzzy representation of the grid voltage;

[0082] Figure 4 It is a fuzzy representation of the active power of a photovoltaic system. Detailed Implementation

[0083] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0084] like Figure 1 As shown, the present invention provides an adaptive control method for voltage, reactive power, and active power of photovoltaic power grid connected to a distribution network. The method includes the following steps:

[0085] Step 1: Determine the control mode based on the grid connection point voltage information, the instructions issued by the control center, and the photovoltaic operating status;

[0086] Step 2: In power control mode, after receiving instructions from the control center, the photovoltaic power station determines the power adjustment amount;

[0087] Step 3: In voltage control mode, determine the reactive power regulation of the photovoltaic power station.

[0088] If a power control command is issued from the superior authority, power control takes priority. If there is no power control command from the superior authority, the control objective is to control the voltage at the grid connection point.

[0089] Step 1: Determine the control mode based on grid connection point voltage information, instructions issued by the control center, and photovoltaic operating status.

[0090] In specific implementation, the grid connection point voltage information is as follows:

[0091] The photovoltaic grid connection point voltage real-time monitoring device monitors the grid connection point voltage value and calculates the difference between the grid connection point voltage and the rated voltage.

[0092] The control center issued the following instructions:

[0093] The photovoltaic communication device receives active power adjustment commands ΔP and reactive power adjustment commands ΔQ issued by the superior authority.

[0094] The photovoltaic operating status is as follows:

[0095] The photovoltaic power output real-time monitoring device monitors the photovoltaic active power output and calculates the photovoltaic active power change rate by using a differential method.

[0096] The determination of the control mode specifically refers to:

[0097] The priority of input signals is determined according to the following rules:

[0098] ① The instructions issued by the control center have the highest priority and will be responded to first.

[0099] ② The grid connection point voltage signal has the next highest priority and will be analyzed for its adaptability to the photovoltaic operating status.

[0100] The input signal is blurred using the following function:

[0101] According to GB / T 12325—2008 "Power Quality - Permissible Deviation of Supply Voltage", the safe voltage range at the grid connection point is set to [0.97U]. ref 1.03U ref The upper limit of voltage is 1.07U. ref The lower limit is 0.93U. refFive fuzzy subsets are selected: undervoltage (VUV), low voltage (UV), normal voltage (N), high voltage (OV), and overvoltage (VOV). The universe of discourse is [-X, X], where X is the maximum voltage deviation of the power grid, and it is fuzzified using a trigonometric function as shown below. Figure 3 As shown, where A i =0.07U ref B i =0.03U ref U ref This is the reference voltage.

[0102] The photovoltaic active power change rate dP(t) / dt is chosen as the photovoltaic state signal, and five fuzzy subsets are selected: rapid decrease (VL), decrease (L), normal fluctuation (N), increase (H), and rapid increase (VH). The universe of discourse is [-Y, Y], where Y is the maximum active power fluctuation of the system, and it is fuzzified using triangular functions as follows: Figure 4 As shown, where C i =0.08kW / min, D i =0.033kW / min.

[0103] Design the membership function according to the following rules to determine the control mode:

[0104] Since the control center issues the highest priority instructions, the inverter is in power control mode when ΔP and ΔQ are not 0.

[0105] The inverter's reactive power output is selected as the fuzzy language output quantity, and five output modes are defined: Fast Reactive Power Output (HSQ), Reactive Power Output (SQ), Normal Operation (N), Reactive Power Absorption (AQ), and Fast Reactive Power Absorption (HAQ). Both input quantities contain five fuzzy subsets, requiring a total of 25 rules to be established, as shown in the table below:

[0106]

[0107] These five output modes are collectively referred to as voltage control modes.

[0108] Step 2: In power control mode, after receiving instructions from the control center, the photovoltaic power station determines the power adjustment amount.

[0109] In power control mode, when the photovoltaic power station receives a reactive power command, it determines the active power output adjustment amount; when the photovoltaic power station receives an active power command, it determines the reactive power output adjustment amount.

[0110] When a photovoltaic power station receives a reactive power command, it determines the active power output adjustment amount, specifically:

[0111] The active voltage sensitivity matrix S is determined by the following formula. PV :

[0112]

[0113] In the formula, J Pδ J Qδ J PU J QU It is a submatrix of the Jacobian matrix.

[0114] The active power output regulation ΔP of a photovoltaic power station is determined by the following formula. PV :

[0115]

[0116] In the formula, U PV U represents the voltage value at the photovoltaic grid connection point. ref Indicates the reference voltage. This indicates the active voltage sensitivity value corresponding to this node.

[0117] In step 2, when the photovoltaic power station receives the active power command, it determines the reactive power output adjustment amount, specifically as follows:

[0118] The reactive power output regulation ΔQ of the photovoltaic inverter is determined by the following formula. PV :

[0119]

[0120] In the formula, U PV U represents the voltage value at the photovoltaic grid connection point. ref S represents the reference voltage. PV This indicates the reactive voltage sensitivity value corresponding to this node.

[0121] Step 3: In voltage control mode, determine the reactive power regulation of the photovoltaic power station.

[0122] In voltage control mode, considering the fluctuation of photovoltaic output, the low-voltage distribution network is divided into zones; key voltage nodes and key photovoltaic power plants are identified within each zone; based on the voltage status of the key nodes, the reactive power regulation of the photovoltaic power plants is determined.

[0123] In step 3, under voltage control mode, considering the fluctuation of photovoltaic output, the low-voltage distribution network is divided into zones, specifically as follows:

[0124] The reactive voltage sensitivity matrix S of the distribution network is obtained by the following formula:

[0125] The power flow calculation equations for the distribution network are shown below:

[0126]

[0127] In the formula: ΔQ and ΔP are the reactive and active power injected into the node, Δδ and ΔU are the changes in the node voltage phase angle and amplitude, respectively; J Pδ J Qδ J PU J QU It is a submatrix of the Jacobian matrix.

[0128] S = [J Qδ J Pδ -1 J PU -J QU ] -1

[0129] The electrical distance matrix D, which takes into account photovoltaic fluctuations, is obtained by the following formula:

[0130] Under typical power flow conditions, the voltage values ​​at each node are:

[0131] U i =[U1,U2,...,U k ,...,U n-1 ] i

[0132] In the formula: k represents a node under power flow state i, U k This represents the voltage value at node k. Assume a typical power flow states are extracted, and p... i Let represent the statistical probability of power flow state i, then we define the correction coefficient for power flow state i at k nodes. for:

[0133]

[0134] Based on the reactive voltage sensitivity matrix S, the electrical distance matrix element d is calculated using the Euclidean distance method. ij :

[0135]

[0136] The correction values ​​of the electrical distance under each power flow condition are obtained to obtain the electrical distance matrix D considering the photovoltaic fluctuations.

[0137]

[0138] The partition objective function f is set as follows:

[0139]

[0140] In the formula, d inner d represents the electrical distance between nodes within a partition. out This represents the electrical distance between nodes outside the partition and nodes inside the partition. α1 and α2 are weighting coefficients, and max indicates finding the maximum value.

[0141] The distribution network nodes are partitioned according to the following procedure:

[0142] ① Initialize the distribution network, treating each node as a cluster;

[0143] ② Merge the two clusters with the smallest inter-cluster electrical distance in sequence, calculate the objective function value at this time, and form a new cluster;

[0144] ③ Randomly select a cluster connected to the newly generated partition and incorporate it into the partition. Calculate the objective function at this point. The partition result is when the objective function is maximized.

[0145] In step 3, key voltage nodes and key photovoltaic nodes are identified within the partition, specifically as follows:

[0146] Determine the critical voltage node using the following formula

[0147]

[0148] In the formula, i represents the i-th node partition obtained, k represents the voltage node in partition i, and max represents the maximum over-limit voltage.

[0149] Within the obtained partitions, each node is divided into a set of normal voltage nodes and an overvoltage node set. The node with the most severe voltage over-limit in the k nodes of the i-th partition is identified and marked as a critical voltage node.

[0150] Key photovoltaic power plants are determined by the following formula.

[0151] Based on the reactive voltage sensitivity matrix S, identify the photovoltaic power station with the highest sensitivity corresponding to the key voltage node.

[0152]

[0153] In the formula, This indicates the obtained critical voltage node. represents an element in the reactive voltage sensitivity matrix, and max represents finding the maximum value.

[0154] In step 3, the reactive power regulation of the photovoltaic power station is determined based on the voltage status of key nodes, specifically as follows:

[0155] The reactive power regulation Q of a photovoltaic power station is determined by the following formula. need :

[0156]

[0157] In the formula, V i max For critical voltage node exceeding the limit, Smax This refers to the reactive voltage sensitivity corresponding to key photovoltaic power plants.

[0158] like Figure 2 As shown, the present invention also includes a voltage and power adaptive control system for photovoltaic grid connection, the system comprising:

[0159] The determination module is used to determine the control mode of the photovoltaic power station based on grid information, instructions issued by the control center, and the photovoltaic operating status.

[0160] The regulation module is used to adjust the active and reactive power of the photovoltaic power station based on a determined control mode and grid information.

[0161] Specifically, the determining module is used to: determine the priority of the input signal; perform fuzzification processing on the input signal; design a membership function; and determine the control mode.

[0162] Specifically, the adjustment module includes:

[0163] The first calculation unit is used to calculate the active and reactive power adjustment of the photovoltaic power station when it receives instructions from the control center under the power control mode.

[0164] The second calculation unit is used to calculate the reactive power regulation of the photovoltaic power station under voltage control mode.

[0165] Specifically, the first computing unit is used for:

[0166] When a photovoltaic power station receives a reactive power command, it determines the active power output adjustment amount; when a photovoltaic power station receives an active power command, it determines the reactive power output adjustment amount.

[0167] Specifically, the second calculation unit is used to: obtain the electrical distance matrix D considering photovoltaic fluctuations; set the partition objective function f to partition the distribution network nodes; find the key voltage nodes and key photovoltaic nodes in the partition; and determine the reactive power regulation amount of the photovoltaic power station based on the voltage state of the key nodes.

[0168] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for adaptive voltage and power control of photovoltaic power grid integration, characterized in that, The control method specifically includes the following steps: Step 1: Determine the control mode based on the grid connection point voltage information, instructions issued by the control center, and the photovoltaic operating status. This specifically includes: The input signal is hierarchically and hierarchically analyzed to determine the input value of the photovoltaic operating status. The input value for determining the instructions issued by the control center is... , The grid connection point voltage information is ; Based on the obtained input signal, the input signal is fuzzified; Design membership functions to determine control modes; in, The rate of change of photovoltaic active power. , These are the changes in active power and reactive power. This is the difference between the grid connection point voltage and the reference voltage; Step 2: In power control mode, after receiving instructions from the control center, the photovoltaic power station determines the specific power adjustment amount, including: When a photovoltaic power station receives an active power regulation command, it determines the reactive power output regulation amount, including: Determine the reactive power output regulation of the photovoltaic inverter using the following formula. : ， In the formula, This indicates the voltage value at the photovoltaic grid connection point. Indicates the reference voltage. This indicates the reactive voltage sensitivity value corresponding to this node; When a photovoltaic power station receives a reactive power regulation command, it determines the active power output regulation amount, including: The active voltage sensitivity matrix is ​​determined by the following formula. : ， In the formula, It is a submatrix of the Jacobian matrix; The active power output regulation of a photovoltaic power station is determined by the following formula. : ， In the formula, This indicates the voltage value at the photovoltaic grid connection point. Indicates the reference voltage. This indicates the active voltage sensitivity value corresponding to this node; Step 3: In voltage control mode, determine the reactive power regulation of the photovoltaic power station.

2. The voltage and power adaptive control method for photovoltaic grid connection according to claim 1, characterized in that: The priority of input signals is determined according to the following rules: ① Instructions issued by the control center have the highest priority and will be responded to first; ② The grid connection point voltage signal has the next highest priority and will be analyzed for its adaptability to the photovoltaic operating status; The input signal is blurred using the following function: Set the grid connection point safety voltage range as follows: The upper limit of voltage is The lower limit is Five fuzzy subsets are selected: undervoltage (VUV), low voltage (UV), normal voltage (N), high voltage (OV), and overvoltage (VOV); the universe of discourse is... , The maximum voltage deviation of the power grid is taken and its fuzzy representation is obtained using a trigonometric function; Select the photovoltaic active power change rate As a signal characterizing the photovoltaic state, five fuzzy subsets are selected: rapidly decreasing VL, decreasing L, normal fluctuation N, increasing H, and rapidly increasing VH; the universe of discourse is... , The maximum active power fluctuation of the system is represented by a triangular function in a fuzzy manner; Design the membership function according to the following rules to determine the control mode: The control center issues the highest priority instructions, when , When the value is not 0, the inverter is in power control mode; Select the inverter reactive power output as the fuzzy language output quantity, and set 5 output modes: fast reactive power output HSQ, output reactive power SQ, normal operation N, reactive power absorption AQ, and fast reactive power absorption HAQ; both input quantities contain 5 fuzzy subsets, and a total of 25 rules need to be established. These 5 output modes are collectively referred to as voltage control modes.

3. The voltage and power adaptive control method for photovoltaic grid connection according to claim 1, characterized in that, In step 3, under voltage control mode, determining the reactive power regulation of the photovoltaic power station specifically includes: Considering the fluctuations in photovoltaic power output, the low-voltage distribution network nodes are divided into zones. Identify key voltage nodes and key photovoltaic power plants within the zone; Based on the voltage status of key nodes, determine the reactive power regulation of the photovoltaic power station.

4. The voltage and power adaptive control method for photovoltaic grid connection according to claim 3, characterized in that, The partitioning process for low-voltage distribution network nodes includes: The reactive voltage sensitivity matrix of the distribution network is obtained by the following formula. : ， It is a submatrix of the Jacobian matrix; The power flow calculation equations for the distribution network are as follows: ， In the formula: and For the reactive and active power injected into the node, and For the changes in the phase angle and magnitude of the node voltage; Under typical power flow conditions, the voltage values ​​at each node are: ， In the formula: Indicates the current state At a certain node below, express The voltage value of the node; Assuming a total of A typical trend. Indicates the current state The statistical probability is then defined as follows: Node flow status Correction factor below for: ； Based on the reactive voltage sensitivity matrix Calculation of electrical distance matrix elements based on Euclidean distance method : ， By calculating the correction values ​​for the electrical distance under each power flow condition, an electrical distance matrix considering photovoltaic fluctuations is obtained. : ； Set the partition objective function as follows : ， In the formula, This indicates the electrical distance between nodes within a partition. This indicates the electrical distance between nodes outside the partition and nodes inside the partition. , These are the weighting coefficients. This indicates finding the maximum value; The distribution network nodes are partitioned according to the following procedure: ① Initialize the distribution network, treating each node as a cluster; ② Merge the two clusters with the smallest inter-cluster electrical distance in sequence, calculate the objective function value at this time, and form a new cluster; ③ Randomly select a cluster connected to the newly generated partition and incorporate it into the partition. Calculate the objective function at this point. The partition result is when the objective function is maximized.

5. The voltage and power adaptive control method for photovoltaic grid connection according to claim 3, characterized in that, The process of identifying key voltage nodes and key photovoltaic power plants within a given region includes: Determine the critical voltage node using the following formula : ， In the formula, Indicates the obtained first Each node is partitioned. Indicates partition For voltage nodes within the range, max represents finding the maximum over-limit voltage; Within the obtained partition, each node is divided into sets of normal voltage nodes and overvoltage nodes, and the first... Each partition The node with the most severe voltage overshoot among all nodes is marked as the critical voltage node. Key photovoltaic power plants are determined by the following formula. : Based on reactive voltage sensitivity matrix Identify the photovoltaic power plants with the highest sensitivity corresponding to critical voltage nodes. ， In the formula, This indicates the obtained critical voltage node. represents an element in the reactive voltage sensitivity matrix, and max represents finding the maximum value.

6. The voltage and power adaptive control method for photovoltaic grid connection according to claim 3, characterized in that, The determination of reactive power regulation of the photovoltaic power station based on the voltage state of key nodes includes: The reactive power regulation of a photovoltaic power station is determined by the following formula. : ， In the formula, For critical voltage nodes exceeding the limit, This refers to the reactive voltage sensitivity corresponding to key photovoltaic power plants.

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