A kind of transformer area theoretical line loss calculation method based on photovoltaic accommodation range identification

Abstract

The application discloses a kind of based on photovoltaic range of accommodation identification's district area theoretical line loss calculation method, specifically related to power system line loss calculation field, including the following steps: S1 according to preset frequency acquisition topological structure, load, photovoltaic and district area head end data, S2 eliminates abnormal value, fills in missing data and normalizes processing, S3 is based on node voltage method and establishes power flow equation, iteratively obtains node voltage amplitude and phase angle, S4 calculates voltage sensitivity factor, S5 calculates power transmission distribution factor, combined with voltage sensitivity factor to obtain photovoltaic accommodation comprehensive index, determine whether node is in the range of accommodation, S6 constructs topological graph data structure, and divides sub-district area using graph traversal algorithm, S7 calculates the equivalent resistance and theoretical line loss power of each sub-district area, and the sum is the entire district area theoretical line loss.The method improves the accuracy of theoretical line loss calculation of photovoltaic-containing district area by accurately identifying the range of photovoltaic accommodation, meets the needs of fine management of power system, and has strong practicality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system line loss calculation, more particularly, to a kind of based on photovoltaic consumption range identification's area theoretical line loss calculation method. BACKGROUND

[0002] Distributed photovoltaic power generation is widely used in low-voltage distribution network area with its clean and efficient characteristics, gradually changing the traditional single power supply mode of the area. As the terminal link of the power system and the user, the theoretical line loss calculation of the area is the core basis of the lean management, loss reduction and energy saving of the power grid. The traditional area theoretical line loss calculation method is designed based on the single power supply scenario of the power grid, mainly by analyzing the topology structure, line parameters and load distribution of the area to calculate the power loss. It has certain applicability in the pure load area before the access of photovoltaic.

[0003] However, when it is actually used, there are still some shortcomings, such as the photovoltaic user has the dual attributes of "load" and "power supply", its power generation may be consumed locally by other users in the area or fed back to the upper grid, the traditional method cannot accurately distinguish the direction of power flow and the path of energy flow, and the calculated line loss is easy to be miscounted, which leads to calculation deviation. The output of photovoltaic is intermittent and volatile due to factors such as light intensity and weather, the power flow in the area presents a bidirectional flow characteristic, the traditional model is based on the steady-state power flow assumption, cannot dynamically track the real-time changes of voltage and current, and is difficult to reflect the dynamic characteristics of line loss caused by photovoltaic fluctuation. The traditional method calculates the line loss as a single power supply area, does not consider the local consumption characteristics of photovoltaic energy, such as the preferential consumption of adjacent users, ignores the influence of the difference of power flow in different areas on the loss, and leads to low line loss calculation accuracy. SUMMARY

[0004] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present application provide a kind of based on photovoltaic consumption range identification's area theoretical line loss calculation method, by the following scheme, to solve the problems that the traditional method cannot accurately distinguish the direction of power flow and the path of energy flow, the calculated line loss is easy to be miscounted, which leads to calculation deviation, the traditional model is based on the steady-state power flow assumption, cannot dynamically track the real-time changes of voltage and current, and is difficult to reflect the dynamic characteristics of line loss caused by photovoltaic fluctuation, and the traditional method calculates the line loss as a single power supply area, does not consider the local consumption characteristics of photovoltaic energy, such as the preferential consumption of adjacent users, ignores the influence of the difference of power flow in different areas on the loss, and leads to low line loss calculation accuracy.

[0005] To achieve the above purpose, the present application provides the following technical scheme: a kind of based on photovoltaic consumption range identification's area theoretical line loss calculation method, comprising, S1: according to the preset frequency real-time acquisition area line loss data, the area line loss data includes topology structure data, load data, photovoltaic data and area head data;

[0006] S2: remove the outliers in S1 collected data, fill in the missing data using linear interpolation method and normalize the collected data of different dimensions;

[0007] S3: according to the data processed in S2, for the low-voltage distribution network containing photovoltaic, based on the node voltage method, the power flow equation is established, and the Newton-Raphson method is used for iterative calculation to obtain the amplitude and phase angle of each node voltage;

[0008] S4: based on the power system power flow equation, the voltage sensitivity factor is calculated;

[0009] S5: calculate the power transmission distribution factor, combine the voltage sensitivity factor calculated in S4 to calculate the comprehensive index of photovoltaic consumption, if the comprehensive index of photovoltaic consumption of the node exceeds the threshold value, it is determined that the node is within the range of photovoltaic consumption;

[0010] S6: construct a topological graph data structure, use graph traversal algorithm, start from the photovoltaic access node, judge whether the adjacent node is within the range of consumption according to the comprehensive index of photovoltaic consumption, gradually determine the boundary of the entire consumption area, and complete the substation area division;

[0011] S7: for each substation area, first calculate the equivalent resistance of the substation area, calculate the theoretical line loss power of the substation area based on the equivalent resistance, and the theoretical line loss of the entire substation area is the sum of the theoretical line loss of each substation area.

[0012] Preferably, the topological structure data refers to the connection relationship and line parameters of transformers, lines and user nodes in the substation, including line resistance R and reactance X, the line resistance R is calculated according to the formula R=ρL / S, wherein ρ is the resistivity of the conductor, L is the length of the line, and S is the cross-sectional area of the conductor;

[0013] For three-phase overhead lines, the unit length reactance value X0 can be obtained according to the formula:

[0014] , wherein D m is the geometric mean distance of three-phase conductor, r′ is the calculation radius of the conductor, μ r is the relative magnetic permeability of the conductor material, for cable lines, the unit length reactance value X0 is obtained according to the technical parameters provided by the cable manufacturer;

[0015] The load data includes real-time active power P load , reactive power Q load and power factor cosφ load of each user node, the collection frequency is set to 15 minutes, the voltage and current signals of the user end are collected and analyzed through the smart meter, and the power calculation formula P load =UIcosφload Q load =UIsinφ load The load data is calculated, where U is the voltage and I is the current;

[0016] The photovoltaic data includes voltage U0, current I0, active power P0, and reactive power Q0 at the head end of the transformer substation. The data is collected once every 15 minutes, and the collection method is as follows: A high-precision power monitoring terminal is installed at the head end of the transformer substation. The voltage and current analog signals are collected through sensors. After A / D conversion and digital signal processing, the active power and reactive power data are obtained using the power calculation formula.

[0017] Preferably, the outlier removal method is as follows:

[0018] For voltage, current, and power data, if the value exceeds ±20% of the normal range, it is considered an anomaly and discarded. For voltage data, if... , If the average value of the voltage data is not the average value, it is considered abnormal. The same applies to current and power data. After abnormal values ​​are identified, they are verified and corrected by querying historical data or data from nearby nodes.

[0019] The method for filling in the missing data is as follows:

[0020] For a missing user active power data at a certain moment, let the power values ​​at adjacent moments t1 and t2 be P1 and P2 respectively, then the power at that moment... , where t is the time when data is missing;

[0021] The normalization process is as follows:

[0022] The collected data of different dimensions are normalized. For X, the normalization formula is: , where X min and X max These are the minimum and maximum values ​​of the data, respectively.

[0023] Preferably, the method for constructing the power flow equations is as follows:

[0024] Suppose there are n nodes in the transformer area, including photovoltaic access nodes and ordinary load nodes, and the injected power S of node i is... i =P i +jQ i Node voltage V i =U i ∠θ i Then the nodal power equation is:

[0025] , where Y ij For the nodal admittance matrix elements, Z ij The impedance between nodes i and j For a photovoltaic access node, the injected power P is the conjugate of the voltage at node j. i and Q i Determined by photovoltaic output, i.e., P i =P pv Q i =Q pv For ordinary load nodes, P i = P load Q i = Q load P pv Q refers to the active power output of the photovoltaic grid connection node. pv The reactive power output of the photovoltaic grid connection node;

[0026] The solution process for the power flow equations is as follows:

[0027] First, the Jacobian matrix J is constructed. The elements of the Jacobian matrix are determined based on the partial derivatives of the power equation with respect to voltage magnitude and phase angle. The power flow equation is solved iteratively. In each iteration, the power deviation ΔP is calculated based on the current node voltage value. i ΔQ i By solving the linear equation system ΔX=J 1. Update the node voltage using ΔS, where ΔX is the correction for voltage magnitude and phase angle, and ΔS is the power deviation vector, until the power deviation meets the convergence condition. , To achieve the set convergence accuracy, the voltage amplitude U at each node is obtained. i and phase angle θ i .

[0028] Preferably, the voltage sensitivity factor includes K. U,P and K U,Q , where K U,P The effect of photovoltaic active power output on node voltage amplitude is defined as follows: That is, the node voltage U affects the photovoltaic active power output P. pv The partial derivatives of K U,Q The effect of photovoltaic reactive power output on the node voltage amplitude is defined as the effect of node voltage U on photovoltaic reactive power output Q. pv The partial derivatives;

[0029] For a given photovoltaic (PV) connection point, calculate the voltage sensitivity of other nodes in the system. When the absolute value of the influence of the PV active power output of node j on the voltage amplitude is |K U,P,j | and the absolute value of the influence of photovoltaic reactive power output at node j on voltage amplitude | K U,Q,j| If the threshold is exceeded, it is preliminarily considered that the node may be within the photovoltaic power consumption range.

[0030] Preferably, the power transfer distribution factor (PTDF) ij,k The mathematical expression used to quantify the impact of changes in injected power at node k on power transmission in branch ij is as follows:

[0031] , where P ij P represents the active power of branch ij. k Represents the injected active power at node k;

[0032] The calculation method for the comprehensive photovoltaic power consumption index is as follows:

[0033] K U,P,j K represents the active power-voltage sensitivity of node j. U,Q,j This represents the reactive power-voltage sensitivity of node j.

[0034] Preferably, the method for dividing the sub-platform areas is as follows:

[0035] A1: Constructing the topology graph data structure:

[0036] Based on the power network of a certain distribution area, each power node is abstracted as a vertex in the graph, and the lines between nodes are used as edges of the graph. The data structure records the type of vertex, including photovoltaic access node, ordinary load node, and the impedance and capacity of the edges.

[0037] A2: Determine the starting point for traversal:

[0038] The graph traversal algorithm starts from the access nodes of each photovoltaic power source within the transformer area.

[0039] A3: Execution graph traversal algorithm:

[0040] Starting from the initial photovoltaic access node, visit the node and mark it as visited;

[0041] Check all adjacent nodes of this node, and determine whether the adjacent nodes are within the absorption range based on the following comprehensive indicators:

[0042] Power balance index: Calculate the difference between the load demand of adjacent nodes and the output power of photovoltaic power sources. If the difference is within the allowable range, the power balance condition is met.

[0043] Voltage quality index: The voltage quality condition is met by calculating the voltage offset of adjacent nodes after they are connected to the photovoltaic power source.

[0044] Line capacity index: After including adjacent nodes in the absorption range, assess whether the power transmission of the connecting line exceeds its rated capacity. If it does not exceed the rated capacity, the line capacity condition is met.

[0045] If an adjacent node meets all the above comprehensive indicators, it will be included in the current photovoltaic power consumption range, and a depth-first search will continue to be performed on the adjacent node, repeating the above judgment process. If it does not meet the requirements, the search in the direction of the adjacent node will be stopped.

[0046] A4: Determine the boundaries of the wastewater treatment area:

[0047] Once the above judgment and search have been completed for all reachable nodes starting from the initial photovoltaic access node, the set of nodes that have been visited and included in the absorption range and their connecting lines constitute the absorption area of ​​the photovoltaic power source. Record the boundary nodes and lines of this area to complete the division of a sub-station area.

[0048] A5: Cyclicly divide all sub-stations:

[0049] For each photovoltaic power access node within the distribution area, repeat steps A3-A4 until the absorption range of all photovoltaic power sources is determined, thus dividing the entire distribution area into multiple sub-distribution areas containing single photovoltaic power source absorption areas.

[0050] Preferably, the equivalent resistance calculation model for the sub-station area is as follows:

[0051] Where m is the number of branch roads within the sub-platform area, P iend Q iend P represents the active and reactive power at the end of branch i. s Q s R represents the active and reactive power at the head end of the substation area. i Let be the resistance of branch i;

[0052] The theoretical line loss power calculation model for the substation area is as follows:

[0053] ΔP loss =I s 2 R eq , where I s The current at the head end of the sub-station area can be obtained from the injected current at the head end node of the sub-station area in the power flow calculation results.

[0054] The technical effects and advantages of this invention are as follows:

[0055] This invention constructs a comprehensive index by using voltage sensitivity factor and power transmission distribution factor, and combines it with graph traversal algorithm to accurately identify the actual photovoltaic power consumption area, clearly distinguishing between "photovoltaic power supply area" and "grid power supply area", thus avoiding statistical distortion of line loss caused by multiple power sources;

[0056] This invention is based on real-time collected photovoltaic power output, load and voltage and current data. It solves the power flow equation iteratively using the Newton-Raphson method and dynamically updates the node voltage and phase angle. It can respond in real time to the power flow changes caused by photovoltaic power output fluctuations and ensure that the line loss calculation is consistent with the actual operating state.

[0057] This invention divides a transformer substation into multiple sub-substations containing a single photovoltaic absorption area. It uses an improved equivalent resistance method to calculate the line loss of each sub-substation separately, fully considering the local power flow characteristics of different areas. Compared with the traditional overall calculation method, the line loss calculation error is significantly reduced, providing a more accurate basis for transformer substation loss reduction and upgrading. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0059] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] As attached Figure 1 The method shown is a method for calculating the theoretical line loss of a photovoltaic distribution area based on the identification of the photovoltaic grid absorption range, including:

[0061] S1: Real-time collection of transformer area line loss data according to a preset frequency. The transformer area line loss data includes topology data, load data, photovoltaic data, and transformer area head-end data.

[0062] The topology data refers to the connection relationship of transformers, lines, and user nodes within the distribution area, as well as line parameters, including line resistance R and reactance X. Specifically, it is obtained through the power GIS system or on-site survey and measurement. The line resistance R is calculated based on the conductor material, cross-sectional area, and length, according to the formula R=ρL / S, where ρ is the conductor resistivity, L is the line length, and S is the conductor cross-sectional area.

[0063] The reactance X is determined by the line structure, conductor arrangement, and frequency, and can be calculated using empirical formulas or specialized software. Specifically, in terms of empirical formula calculation, for a three-phase overhead line, the reactance value X0 per unit length can be calculated using the following formula:

[0064] Perform the calculation, where D m r is the geometric mean distance between the three phase conductors (in meters), r′ is the calculated radius of the conductor (in meters), and μ is the geometric mean distance between the three phase conductors. rThe relative permeability of the conductor material (μ of copper conductor) r =1, aluminum wire μ r =1); For cable lines, the reactance value per unit length X0 is obtained from the technical parameters provided by the cable manufacturer.

[0065] The load data includes the real-time active power P of each user node. load Reactive power Q load and power factor cosφ load The data collection frequency is set to once every 15 minutes. Through the smart meter, voltage and current signals at the user end are collected and analyzed, and the power calculation formula P is used. load =UIcosφ load Q load =UIsinφ load The load data is calculated, where U is the voltage and I is the current;

[0066] The photovoltaic data includes voltage U0, current I0, active power P0, and reactive power Q0 at the beginning of the transformer substation. The data is collected once every 15 minutes. The data collection method is as follows: A high-precision power monitoring terminal is installed at the beginning of the transformer substation. The voltage and current analog signals are collected by the sensor. After A / D conversion and digital signal processing, the active power and reactive power data are obtained using the power calculation formula.

[0067] S2: Remove outliers from the data collected in S1, fill in the missing data using linear interpolation, and normalize the collected data of different dimensions.

[0068] The method for removing outliers is as follows:

[0069] For voltage, current, and power data, if the value exceeds ±20% of the normal range, it is considered an anomaly and discarded. For voltage data, if... , If the average value of the voltage data is not the average value, it is considered abnormal. The same applies to current and power data. After abnormal values ​​are identified, they are verified and corrected by querying historical data or data from nearby nodes.

[0070] The method for filling in the missing data is as follows:

[0071] For a missing user active power data at a certain moment, let the power values ​​at adjacent moments t1 and t2 be P1 and P2 respectively, then the power at that moment... , where t is the time when data is missing;

[0072] The normalization process is as follows:

[0073] The collected data of different dimensions are normalized. For X, the normalization formula is: , where X min and X max These are the minimum and maximum values ​​of the data, respectively.

[0074] S3: Based on the data processed in S2, for a low-voltage distribution network containing photovoltaics, power flow equations are established based on the nodal voltage method, and iterative calculations are performed using the Newton-Raphson method to obtain the voltage amplitude and phase angle of each node;

[0075] The method for constructing the power flow equations is as follows:

[0076] Suppose there are n nodes in the transformer area, including photovoltaic access nodes and ordinary load nodes, and the injected power S of node i is... i =P i +jQ i Node voltage V i =U i ∠θ i Then the nodal power equation is:

[0077] , where Y ij For the nodal admittance matrix elements, Z ij The impedance between nodes i and j For a photovoltaic access node, the injected power P is the conjugate of the voltage at node j. i and Q i Determined by photovoltaic output, i.e., P i =P pv Q i =Q pv For ordinary load nodes, P i = P load Q i = Q load P pv Q refers to the active power output of the photovoltaic (PV) grid connection node, reflecting the active power transmitted by PV equipment to the grid. pv It refers to the reactive power output of photovoltaic access nodes, reflecting the photovoltaic equipment's ability to regulate the reactive power of the power grid;

[0078] The solution process for the power flow equations is as follows:

[0079] First, the Jacobian matrix J is constructed. The elements of the Jacobian matrix are determined based on the partial derivatives of the power equation with respect to voltage magnitude and phase angle. The power flow equation is solved iteratively. In each iteration, the power deviation ΔP is calculated based on the current node voltage value. i ΔQ i By solving the linear equation system ΔX=J 1. Update the node voltage using ΔS, where ΔX is the correction for voltage magnitude and phase angle, and ΔS is the power deviation vector, until the power deviation meets the convergence condition. , To achieve the set convergence accuracy, the voltage amplitude U at each node is obtained. i and phase angle θ i This provides key parameters for subsequent calculations of theoretical line loss in transformer substations.

[0080] S4: Calculate the voltage sensitivity factor based on the power flow equations of the power system;

[0081] The voltage sensitivity factor includes K U,P and K U,Q This is used to quantify the impact of photovoltaic active and reactive power output on node voltage amplitude, thereby assisting in identifying the photovoltaic absorption range. K is used to... U,P The effect of photovoltaic active power output on node voltage amplitude is defined as follows: That is, the node voltage U affects the photovoltaic active power output P. pv The partial derivatives of K U,Q The effect of photovoltaic reactive power output on node voltage amplitude is defined as follows: That is, the node voltage U affects the photovoltaic reactive power output Q. pv The partial derivatives of these two factors are derived by performing partial derivative operations on the power flow equations and using the rules of complex number operations and the properties of partial derivatives.

[0082] It should be further explained that, for a given photovoltaic access point, when calculating the voltage sensitivity of other nodes in the system, the absolute value of the influence of the photovoltaic active power output of node j on the voltage amplitude is |K U,P,j |K (i.e., the absolute value of the influence of photovoltaic reactive power output at node j on voltage amplitude) U,Q,j | If the value exceeds the set threshold, it is preliminarily considered that the node may be within the absorption range of the photovoltaic system, providing a key basis for subsequent accurate calculation of the theoretical line loss of the transformer area.

[0083] S5: Calculate the power transmission distribution factor and combine it with the voltage sensitivity factor calculated in S4 to calculate the comprehensive photovoltaic absorption index. If the comprehensive photovoltaic absorption index of a node exceeds the threshold, the node is determined to be within the photovoltaic absorption range.

[0084] The power transfer distribution factor PTDF ij,k The mathematical expression used to quantify the impact of changes in injected power at node k on power transmission in branch ij is as follows:

[0085] , where P ij P represents the active power of branch ij. k Represents the injected active power at node k;

[0086] The calculation method for the comprehensive photovoltaic power consumption index is as follows:

[0087] K U,P,j K represents the active power-voltage sensitivity of node j, reflecting the degree to which the voltage at node j is sensitive to active power injection. U,Q,j This represents the reactive power-voltage sensitivity of node j, reflecting the degree to which the voltage at node j is sensitive to reactive power injection.

[0088] S6: Construct a topology graph data structure, use a graph traversal algorithm, starting from the photovoltaic access node, determine the adjacent nodes within the absorption range based on the comprehensive photovoltaic absorption index, gradually determine the boundary of the entire absorption area, and complete the sub-area division;

[0089] The method for dividing the sub-platform areas is as follows:

[0090] A1: Constructing the topology graph data structure:

[0091] Based on the power network of a certain distribution area, each power node is abstracted as a vertex in the graph, and the lines between nodes are used as edges of the graph. The data structure records the type of vertex, including photovoltaic access node, ordinary load node, and the impedance and capacity of the edges.

[0092] A2: Determine the starting point for traversal:

[0093] The graph traversal algorithm starts from the access nodes of each photovoltaic power source within the transformer area.

[0094] A3: Execution graph traversal algorithm:

[0095] Starting from the initial photovoltaic access node, visit the node and mark it as visited;

[0096] Check all adjacent nodes of this node, and determine whether the adjacent nodes are within the absorption range based on the following comprehensive indicators:

[0097] Power balance index: Calculate the difference between the load demand of adjacent nodes and the output power of photovoltaic power sources. If the difference is within the allowable range, such as not exceeding ±20% of the node load, then the power balance condition is met.

[0098] Voltage quality index: The voltage deviation of adjacent nodes after connecting to photovoltaic power is calculated. If the voltage deviation is within the specified standard range, such as ±7% of the rated voltage, then the voltage quality condition is met.

[0099] Line capacity index: After including adjacent nodes in the absorption range, assess whether the power transmission of the connecting line exceeds its rated capacity. If it does not exceed the rated capacity, the line capacity condition is met.

[0100] If an adjacent node meets all the above comprehensive indicators, it will be included in the current photovoltaic power consumption range, and a depth-first search will continue to be performed on the adjacent node, repeating the above judgment process. If it does not meet the requirements, the search in the direction of the adjacent node will be stopped.

[0101] A4: Determine the boundaries of the wastewater treatment area:

[0102] Once the above judgment and search have been completed for all reachable nodes starting from the initial photovoltaic access node, the set of nodes that have been visited and included in the absorption range and their connecting lines constitute the absorption area of ​​the photovoltaic power source. Record the boundary nodes and lines of this area to complete the division of a sub-station area.

[0103] A5: Cyclicly divide all sub-stations:

[0104] For each photovoltaic power access node within the distribution area, repeat steps A3-A4 until the absorption range of all photovoltaic power sources is determined, thus dividing the entire distribution area into multiple sub-distribution areas containing single photovoltaic power source absorption areas.

[0105] S7: For each sub-area, first calculate the equivalent resistance of the sub-area, and then calculate the theoretical line loss power of the sub-area based on the equivalent resistance. The theoretical line loss of the entire sub-area is the sum of the theoretical line losses of each sub-area.

[0106] The equivalent resistance calculation model for the sub-station area is as follows:

[0107] Where m is the number of branch roads within the sub-platform area, P iend Q iend P represents the active and reactive power at the end of branch i. s Q s R represents the active and reactive power at the head end of the substation area. i Let be the resistance of branch i;

[0108] The theoretical line loss power calculation model for the substation area is as follows:

[0109] ΔP loss =I s 2 R eq , where I s The current at the head end of the sub-station area can be obtained from the injected current at the head end node of the sub-station area in the power flow calculation results.

[0110] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0111] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating the theoretical line loss of a photovoltaic distribution area based on the identification of photovoltaic grid absorption range, characterized in that, include: S1: Real-time collection of transformer area line loss data according to a preset frequency. The transformer area line loss data includes topology data, load data, photovoltaic data, and transformer area head-end data. S2: Remove outliers from the data collected in S1, fill in the missing data using linear interpolation, and normalize the collected data of different dimensions. S3: Based on the data processed in S2, for a low-voltage distribution network containing photovoltaics, power flow equations are established based on the nodal voltage method, and iterative calculations are performed using the Newton-Raphson method to obtain the voltage amplitude and phase angle of each node; S4: Calculate the voltage sensitivity factor based on the power flow equations of the power system; S5: Calculate the power transmission distribution factor and combine it with the voltage sensitivity factor calculated in S4 to calculate the comprehensive photovoltaic absorption index. If the comprehensive photovoltaic absorption index of a node exceeds the threshold, the node is determined to be within the photovoltaic absorption range. S6: Construct a topology graph data structure, use a graph traversal algorithm, starting from the photovoltaic access node, determine whether the adjacent nodes are within the absorption range based on the comprehensive photovoltaic absorption index, gradually determine the boundary of the entire absorption area, and complete the sub-area division; S7: For each substation area, first calculate the equivalent resistance of the substation area, and then calculate the theoretical line loss power of the substation area based on the equivalent resistance. The theoretical line loss of the entire substation area is the sum of the theoretical line losses of each substation area.

2. The method for calculating the theoretical line loss of a transformer substation based on photovoltaic absorption range identification according to claim 1, characterized in that: The topology data refers to the connection relationship of transformers, lines, and user nodes within the distribution area, as well as line parameters, including line resistance R and reactance X. The line resistance R is calculated based on the conductor material, cross-sectional area, and length using the formula R=ρL / S, where ρ is the conductor resistivity, L is the line length, and S is the conductor cross-sectional area. For three-phase overhead lines, the reactance per unit length X0 is determined by the formula: Perform the calculation, where D m Let r be the geometric mean distance between the three phase conductors, r′ be the calculated radius of the conductor, and μ be the distance between the conductors. r X0 represents the relative permeability of the conductor material. For cable lines, the reactance value per unit length X0 is obtained from the technical parameters provided by the cable manufacturer. The load data includes the real-time active power P of each user node. load Reactive power Q load and power factor cosφ load The data collection frequency is set to once every 15 minutes. Through the smart meter, voltage and current signals at the user end are collected and analyzed, and the power calculation formula P is used. load =UIcosφ load Q load =UIsinφ load The load data is calculated, where U is the voltage and I is the current; The photovoltaic data includes voltage U0, current I0, active power P0, and reactive power Q0 at the head end of the transformer substation. The data is collected once every 15 minutes, and the collection method is as follows: A high-precision power monitoring terminal is installed at the head end of the transformer substation. The voltage and current analog signals are collected through sensors. After A / D conversion and digital signal processing, the active power and reactive power data are obtained using the power calculation formula.

3. The method for calculating the theoretical line loss of a transformer substation based on photovoltaic absorption range identification according to claim 1, characterized in that: The method for removing outliers is as follows: For voltage, current, and power data, if the value exceeds ±20% of the normal range, it is considered an anomaly and discarded. For voltage data, if... , If the average value of the voltage data is not the average value, it is considered abnormal. The same applies to current and power data. After abnormal values ​​are identified, they are verified and corrected by querying historical data or data from nearby nodes. The method for filling in the missing data is as follows: For a missing user active power data at a certain moment, let the power values ​​at adjacent moments t1 and t2 be P1 and P2 respectively, then the power at that moment... , where t is the time when data is missing; The normalization process is as follows: The collected data of different dimensions are normalized. For X, the normalization formula is: , where X min and X max These are the minimum and maximum values ​​of the data, respectively.

4. The method for calculating the theoretical line loss of a transformer substation based on photovoltaic absorption range identification according to claim 1, characterized in that: The method for constructing the power flow equations is as follows: Suppose there are n nodes in the transformer area, including photovoltaic access nodes and ordinary load nodes, and the injected power S of node i is... i =P i +jQ i Node voltage V i =U i ∠θ i Then the nodal power equation is: , where Y ij For the nodal admittance matrix elements, Z ij The impedance between nodes i and j For a photovoltaic access node, the injected power P is the conjugate of the voltage at node j. i and Q i Determined by photovoltaic output, i.e., P i =P pv Q i =Q pv For ordinary load nodes, P i = P load Q i = Q load P pv Q refers to the active power output of the photovoltaic grid connection node. pv The reactive power output of the photovoltaic grid connection node; The solution process for the power flow equations is as follows: First, the Jacobian matrix J is constructed. The elements of the Jacobian matrix are determined based on the partial derivatives of the power equation with respect to voltage magnitude and phase angle. The power flow equation is solved iteratively. In each iteration, the power deviation ΔP is calculated based on the current node voltage value. i ΔQ i By solving the linear equation system ΔX=J 1. Update the node voltage using ΔS, where ΔX is the correction for voltage magnitude and phase angle, and ΔS is the power deviation vector, until the power deviation meets the convergence condition. , To achieve the set convergence accuracy, the voltage amplitude U at each node is obtained. i and phase angle θ i .

5. The method for calculating the theoretical line loss of a transformer substation based on photovoltaic absorption range identification according to claim 1, characterized in that: The voltage sensitivity factor includes K U,P and K U,Q , where K U,P The effect of photovoltaic active power output on node voltage amplitude is defined as follows: That is, the node voltage U affects the photovoltaic active power output P. pv The partial derivatives of K U,Q The effect of photovoltaic reactive power output on node voltage amplitude is defined as follows: That is, the node voltage U affects the photovoltaic reactive power output Q. pv The partial derivatives; For a given photovoltaic (PV) connection point, calculate the voltage sensitivity of other nodes in the system. When the absolute value of the influence of the PV active power output of node j on the voltage amplitude is |K U,P,j | and the absolute value of the influence of photovoltaic reactive power output at node j on voltage amplitude | K U,Q,j | If the threshold is exceeded, it is preliminarily considered that the node may be within the photovoltaic power consumption range.

6. The method for calculating the theoretical line loss of a transformer substation based on photovoltaic absorption range identification according to claim 1, characterized in that: The power transfer distribution factor PTDF ij,k The mathematical expression used to quantify the impact of changes in injected power at node k on power transmission in branch ij is as follows: , where P ij P represents the active power of branch ij. k Represents the injected active power at node k; The calculation method for the comprehensive photovoltaic power consumption index is as follows: K U,P,j K represents the active power-voltage sensitivity of node j. U,Q,j This represents the reactive power-voltage sensitivity of node j.

7. The method for calculating the theoretical line loss of a transformer substation based on photovoltaic absorption range identification according to claim 1, characterized in that: The method for dividing the sub-platform areas is as follows: A1: Constructing the topology graph data structure: Based on the power network of a certain distribution area, each power node is abstracted as a vertex in the graph, and the lines between nodes are used as edges of the graph. The data structure records the type of vertex, including photovoltaic access node, ordinary load node, and the impedance and capacity of the edges. A2: Determine the starting point for traversal: Starting from the access nodes of each photovoltaic power source within the transformer area, the graph traversal algorithm is initiated. A3: Execution graph traversal algorithm: Starting from the initial photovoltaic access node, visit the node and mark it as visited; Check all adjacent nodes of this node, and determine whether the adjacent nodes are within the absorption range based on the following comprehensive indicators: Power balance index: Calculate the difference between the load demand of adjacent nodes and the output power of photovoltaic power sources. If the difference is within the allowable range, the power balance condition is met. Voltage quality index: The voltage quality condition is met by calculating the voltage offset of adjacent nodes after they are connected to the photovoltaic power source. Line capacity index: After including adjacent nodes in the absorption range, assess whether the power transmission of the connecting line exceeds its rated capacity. If it does not exceed the rated capacity, the line capacity condition is met. If an adjacent node meets all the above comprehensive indicators, it will be included in the current photovoltaic power consumption range, and a depth-first search will continue to be performed on the adjacent node, repeating the above judgment process. If it does not meet the requirements, the search in the direction of the adjacent node will be stopped. A4: Determine the boundaries of the wastewater treatment area: Once the above judgment and search have been completed for all reachable nodes starting from the initial photovoltaic access node, the set of nodes that have been visited and included in the absorption range and their connecting lines constitute the absorption area of ​​the photovoltaic power source. Record the boundary nodes and lines of this area to complete the division of a sub-station area. A5: Cyclicly divide all sub-stations: For each photovoltaic power access node within the distribution area, repeat steps A3-A4 until the absorption range of all photovoltaic power sources is determined, thus dividing the entire distribution area into multiple sub-distribution areas containing single photovoltaic power source absorption areas.

8. The method for calculating the theoretical line loss of a transformer substation based on photovoltaic absorption range identification according to claim 1, characterized in that: The equivalent resistance calculation model for the sub-station area is as follows: Where m is the number of branch roads within the sub-platform area, P iend Q iend P represents the active and reactive power at the end of branch i. s Q s R represents the active and reactive power at the head end of the substation area. i Let be the resistance of branch i; The theoretical line loss power calculation model for the substation area is as follows: ΔP loss =I s 2 R eq , where I s The current at the head end of the substation is obtained from the injected current at the head node of the substation in the power flow calculation results.

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