Method for calculating voltage out-of-limit after photovoltaic access to power distribution network, terminal and storage medium

Abstract

The application provides a voltage out-of-limit calculation method for photovoltaic access to a power distribution network, a terminal and a storage medium. The calculation method comprises the following steps: obtaining voltage source parameters, line parameters and distribution transformer parameters of the power distribution network, and constructing a power distribution network topology model; constructing multiple distributed photovoltaic access schemes, and obtaining photovoltaic output curves of various photovoltaic access schemes; the distributed photovoltaic access scheme comprises an access position and an access capacity; constructing multiple load distribution schemes, and obtaining load fitting curves of various load distribution schemes; the load distribution scheme comprises a load proportion allocated to each node of the power distribution network; based on the photovoltaic output curve of each photovoltaic access scheme, the load fitting curve of each load distribution scheme and the power distribution network topology model, the voltage out-of-limit situation of various photovoltaic access power distribution network scenarios is simulated and calculated. The application can simulate various operating states of a simulation model for a power distribution network, and the power distribution network topology model has strong applicability and replicability.

Description

Technical Field

[0001] This application relates to the field of power flow calculation technology, and in particular to a method, terminal and storage medium for calculating voltage over-limit after photovoltaic grid connection. Background Technology

[0002] The integration of distributed generation (DG) sources into the distribution network increases the randomness and uncertainty of the grid, potentially leading to reverse power flow. This alters the traditional grid structure and operating mode of the power system, significantly impacting network losses and steady-state voltage distribution. It may reduce the reliability of power supply, increase the system's load-carrying capacity, and cause voltage fluctuations and flicker. Therefore, it is necessary to accurately calculate the power flow distribution of the distribution network after DG integration to simulate the network's operating state and analyze its potential impact.

[0003] In practice, it has been found that the integration of distributed power sources has a significant impact on voltage deviations, especially voltage over-limit issues, causing overvoltage problems in local power grids and posing a considerable risk to the safe and reliable operation of the power grid. Moreover, due to the diverse structures and configurations of power grids, it is difficult to effectively calculate various operational data of the distribution network, making it impossible to provide effective solutions to the voltage over-limit problem. Summary of the Invention

[0004] This application provides a method, terminal, and storage medium for calculating voltage over-limit after photovoltaic grid connection, in order to solve the problem in the prior art that it is difficult to fully simulate all operating states of the distribution network with a single model.

[0005] Firstly, this application provides a method for calculating voltage exceedance after photovoltaic power is connected to the distribution network, the calculation method comprising:

[0006] Obtain the voltage source parameters, line parameters, and transformer parameters of the distribution network, and construct the distribution network topology model;

[0007] Multiple distributed photovoltaic (PV) grid connection schemes are constructed, and PV output curves for each scheme are obtained; the distributed PV grid connection schemes include grid connection location and grid connection capacity.

[0008] Multiple load allocation schemes are constructed, and load fitting curves for each scheme are obtained; the load allocation scheme includes the load proportion allocated to each node of the distribution network.

[0009] Based on the photovoltaic output curves of each photovoltaic access scheme, the load fitting curves of each load distribution scheme, and the distribution network topology model, the voltage over-limit situations of various photovoltaic access distribution network scenarios are simulated and calculated.

[0010] In a second aspect, this application provides a terminal including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method as described in the first aspect or any possible implementation thereof.

[0011] Thirdly, this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method as described in the first aspect or any possible implementation thereof.

[0012] This application provides a method, terminal, and storage medium for calculating voltage over-limit after photovoltaic (PV) access to a distribution network. By constructing a distribution network topology model, and building various distributed PV access schemes and various load distribution schemes based on the distribution network topology model, the voltage over-limit situation of various PV access scenarios is simulated and calculated based on the obtained PV output curves of various PV access schemes, load fitting curves of various load distribution schemes, and the distribution network topology model. This enables the simulation of various operating states of the distribution network on a single simulation model. Furthermore, the distribution network topology model has rich components, comprehensive scenarios, and strong applicability and reproducibility. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a flowchart illustrating the implementation of the voltage over-limit calculation method after photovoltaic grid connection provided in this application embodiment;

[0015] Figure 2 This is a topology diagram of the power distribution network provided in the embodiments of this application;

[0016] Figure 3 This is a diagram of the 10KV distribution network topology provided in the embodiments of this application;

[0017] Figure 4 This is a schematic diagram illustrating the setting of the voltage source parameter range provided in an embodiment of this application;

[0018] Figure 5 This is a schematic diagram illustrating the setting of the line parameter range provided in an embodiment of this application;

[0019] Figure 6 This is a schematic diagram illustrating the setting of the distribution transformer parameter range provided in an embodiment of this application;

[0020] Figure 7 This is a functional design schematic diagram of the photovoltaic output curve provided in the embodiments of this application;

[0021] Figure 8 This is a schematic diagram of the design of load / energy storage access location and ratio provided in the embodiments of this application;

[0022] Figure 9 This is a schematic diagram illustrating the setting of the maximum allowable reverse load rate preset percentage provided in the embodiments of this application;

[0023] Figure 10 This is a schematic diagram of the node configuration ratio of the input load provided in the embodiments of this application;

[0024] Figure 11 This is a schematic diagram of the load distribution curve provided in an embodiment of this application;

[0025] Figure 12 This is a schematic diagram illustrating the functional settings of the load fitting curve provided in an embodiment of this application;

[0026] Figure 13 This is a schematic diagram of the voltage over-limit calculation device after photovoltaic grid connection provided in the embodiments of this application;

[0027] Figure 14 This is a schematic diagram of the terminal provided in the embodiments of this application. Detailed Implementation

[0028] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the following description will be provided in conjunction with the accompanying drawings and specific embodiments.

[0030] Figure 1 The implementation flowchart of the voltage over-limit calculation method after photovoltaic grid connection provided in the embodiments of this application is described in detail below:

[0031] In step 101, the voltage source parameters, line parameters, and transformer parameters of the distribution network are obtained, and the distribution network topology model is constructed.

[0032] For the topology of the distribution network, see [link to relevant documentation]. Figure 2Along the distribution network feeder L, each centralized load is considered as a node and numbered accordingly. There are N nodes, and the voltage of the nth node is V. n The voltage at the beginning of the line is V0, and the standard voltage of the line is V. N The line impedance between each node is the same, and the line impedance between adjacent nodes is Z = R + jX; the load of the distribution network system is evenly distributed at the feeder points of the lines, and the load power is denoted as Pl + jQ. l The capacity of the distributed power system connected at node i is P. pv +jQ pv express.

[0033] In this embodiment of the application, a distribution network topology model is constructed, and voltage parameters, line parameters, and transformer parameters of the distribution network are set in the distribution network topology model so that the distribution network topology model meets the actual situation.

[0034] In one possible implementation, step 101 may include:

[0035] Set up voltage sources, distribution network feeders, distributed photovoltaic access points, distribution transformer access points, and voltage detection points, and draw the topology of the distribution network;

[0036] Based on the obtained voltage source parameters, line parameters, and transformer parameters of the distribution network, parameters are set for the topology of the distribution network to construct a distribution network topology model;

[0037] Among them, voltage source parameters include voltage level, actual operating voltage, resistance, reactance, and impedance; line parameters include conductor type, resistance per unit length, reactance per unit length, and susceptance per unit length; distribution transformer parameters include rated capacity, short-circuit voltage percentage, short-circuit loss, no-load loss, no-load current percentage, number of taps in the high-voltage side tap range, unit adjustment of the high-voltage side tap, and current tap position on the high-voltage side.

[0038] See Figure 3 Set up voltage sources, 10KV feeders, distributed photovoltaic access points, 10KV distribution transformer access points, and voltage detection points, and draw the topology of the distribution network.

[0039] according to Figure 3 The distribution network topology is determined, and the voltage source parameters, line parameters, and transformer parameters of the distribution network are obtained respectively. Corresponding basic parameters are then set for the distribution network topology, as follows:

[0040] First, see Figure 4 The voltage source parameter setting parameters include voltage level (kV), actual operating voltage (kV), resistance (Ω), reactance (Ω), and their ratio impedance (Ω).

[0041] Second, see Figure 5 The parameter setting range for 10kV lines includes conductor type, resistance per unit length (Ω), impedance per unit length (Ω), and susceptance per unit length (μS).

[0042] Third, see Figure 6 The parameter setting range for a 10kV distribution transformer includes rated capacity (kVA), short-circuit voltage percentage (%), short-circuit loss (kW), no-load loss (kW), no-load current percentage (%), number of taps on the high-voltage side, unit adjustment of the high-voltage side taps (%), and the current tap position on the high-voltage side.

[0043] By setting the topology and basic parameters of the distribution network as described above, the topology model of the distribution network required in the embodiments of this application is constructed.

[0044] In step 102, multiple distributed photovoltaic access schemes are constructed, and the photovoltaic output curves of each photovoltaic access scheme are obtained; the distributed photovoltaic access schemes include the access location and the access capacity.

[0045] Distributed photovoltaic power generation is a type of power source that provides power support to the system.

[0046] Based on the topology model of the distribution network constructed in step 101 and the setting of basic parameters, multiple distributed photovoltaic access schemes are constructed, and different distributed photovoltaic access schemes are connected to the distribution network to obtain the photovoltaic output curves corresponding to different distributed photovoltaic access schemes.

[0047] In this embodiment, the photovoltaic output curve can be designed as either a preset value or a custom value. Technicians can choose between the preset value and the custom curve style according to actual needs. For specific settings, please refer to [link to relevant documentation]. Figure 7 .

[0048] A photovoltaic (PV) output curve is a characteristic expression of how the output power changes over time. The power emitted by PV fluctuates, with external factors depending on light intensity, angle of illumination, duration of illumination, and the purity of the silicon-based material (affecting efficiency), while internal factors depend on hot spot effects, potential-induced degradation effects, and microcracks in the solar cells.

[0049] In one possible implementation, distributed photovoltaic access schemes can include front-end distribution, mid-end distribution, back-end distribution, uniform distribution, and custom distribution.

[0050] In this application embodiment, the distributed photovoltaic access scheme includes access location and access capacity. The access scheme may include centralized front-end distribution, centralized mid-end distribution, centralized back-end distribution, uniform distribution, and custom distribution.

[0051] Distributed photovoltaic (PV) grid connection methods are flexible and versatile, with various variations in connection capacity and location. One of the protection measures advocated in this application is the method for setting up distributed PV grid connection methods, which is mainly divided into five categories: concentrated distribution at the front end, concentrated distribution at the middle end, concentrated distribution at the back end, uniform distribution, and custom distribution. The five distributed PV grid connection schemes in this application embodiment are typical states simulated based on the actual load / PV grid connection situation. See [link / reference]. Figure 8 Specifically:

[0052] (1) The design scheme of the front-end distribution is: Node 1 is configured with 50%, Node 2 with 30%, Node 3 with 20%, the first three nodes are in decreasing order, and the remaining nodes are not connected.

[0053] (2) The design scheme of central distribution in the middle section is as follows: Node 5 is configured with 25%, Node 6 with 50%, Node 7 with 35%, the three middle points form a "single camel hump" shape, and the other nodes are not connected.

[0054] (3) The design scheme of centralized distribution in the back end is: 40% of the nodes are configured in node 8, 60% of the nodes are configured in node 9, and the remaining nodes are not connected.

[0055] (4) The uniform distribution design scheme is as follows: the configuration of each node is 12.5%.

[0056] (5) The design scheme of the custom distribution is to supplement the shortcomings of the first four schemes. Any value can be set according to actual needs, and the sum of the proportions can be 100%.

[0057] For example, a distribution network line has a total distributed photovoltaic capacity of 100kWp. Its distributed photovoltaic access scheme is concentrated in the front end distribution, that is, the first node is allocated a capacity of 50kWp, the second node is allocated a capacity of 30kWp, and the third node is allocated a capacity of 20kWp.

[0058] In one possible implementation, after acquiring and constructing multiple distributed photovoltaic grid connection schemes, the method may further include:

[0059] The preset percentage of the maximum allowable reverse load rate after various distributed photovoltaic (PV) systems are connected to the distribution network is set; the preset percentage of the maximum allowable reverse load rate is used to prevent load backflow after distributed PV systems are connected to the distribution network.

[0060] After distributed photovoltaic (PV) grid connections are established, as the connected capacity increases, the 10kV distribution network topology model will experience changes in power flow direction, i.e., load backflow. At this time, it is necessary to set the maximum allowable reverse load rate to prevent load backflow after distributed PV grid connections are established.

[0061] The understanding of load feedback is as follows: Under normal circumstances, the system provides power to the distribution network, and each power user in the distribution network consumes active and reactive power. When distributed power sources are connected to the distribution network, if the power provided by the power source meets the load demand of the users in the grid and there is a surplus, the load will be fed back to the upper-level grid, that is, the reverse transmission of active and reactive power.

[0062] See Figure 9 The preset percentages for the maximum permissible reverse load rate are 0%, 20%, 40%, 60%, and 80%, and custom values ​​can also be set. According to relevant technical standards for distributed power source access and grid operation safety standards, the maximum reverse load rate of the equipment should not exceed 80%, therefore the custom value should be any value less than 80.

[0063] If the maximum reverse load rate exceeds 80%, it has the same harmful effect as the forward load rate exceeding 80%. It indicates that the system load is too high, that is, the power value is too high. The heat generation of power transmission and transformation equipment and system losses will increase significantly. Long-term operation will affect the entire life cycle of the equipment. Moreover, excessive losses reduce economic efficiency, which is detrimental to the power supply company. Therefore, the dispatching and operation and maintenance management departments of power supply companies have set a limit of 80% load rate.

[0064] In the embodiments of this application, the preset percentage of the maximum allowable reverse load rate is accurately determined. This is achieved by limiting the photovoltaic access capacity and by using scheduling operation strategies to ensure system power balance. The scheduling operation strategies include which time periods photovoltaics can be connected to the grid and which time periods photovoltaics need to be disconnected from the grid. These strategies need to be formulated by calculating the system power balance.

[0065] In step 103, multiple load allocation schemes are constructed, and load fitting curves for each load allocation scheme are obtained; the load allocation scheme includes the load ratio allocated to each node of the distribution network.

[0066] Based on the topology model of the distribution network constructed in step 101 and the setting of basic parameters, multiple load allocation schemes are constructed, and different load allocation schemes are assigned to the distribution network to obtain the load fitting curves of various load allocation schemes.

[0067] The second solution proposed in this application is a simulation curve design for multi-scenario load access methods. Since the access load of each node has great differences and diversity, this application can simulate the distribution of various types of load access to the greatest extent.

[0068] In one possible implementation, the load distribution scheme may include average distribution, decreasing distribution, increasing distribution, convex distribution, concave distribution, and custom distribution.

[0069] In this application embodiment, the load distribution scheme design includes average distribution, decreasing distribution, increasing distribution, convex distribution, concave distribution, and custom distribution. The node configuration ratios for each type are detailed below. Figure 10 The corresponding load distribution curve diagram can be found in [reference needed]. Figure 11 The specific ratio is set as follows:

[0070] (1) The average distribution ratio is set as follows: the ratio of each node is 12.5%.

[0071] (2) The decreasing distribution ratio is set as follows: 20% for node 2, 18% for node 3, 16% for node 4, 14% for node 5, 11% for node 6, 9% for node 7, 7% for node 8, and 5% for node 9, in a decreasing manner, and no other nodes are set.

[0072] (3) The incremental distribution setting ratio is as follows: Node 2 is set to 5%, Node 3 to 7%, Node 4 to 9%, Node 5 to 11%, Node 6 to 14%, Node 7 to 16%, Node 8 to 18%, Node 9 to 20%, in an incremental manner, and the remaining nodes are not set.

[0073] (4) The convex distribution setting ratio is: 4% for node 2, 12% for node 3, 16% for node 4, 18% for node 5, 18% for node 6, 16% for node 7, 12% for node 8, and 4% for node 9.

[0074] (5) The setting ratio of the concave distribution is: 24% for node 2, 14% for node 3, 7% for node 4, 5% for node 5, 5% for node 6, 7% for node 7, 14% for node 8, and 24% for node 9.

[0075] (6) The custom distribution setting ratio is: to supplement the shortcomings of the first five setting schemes, any ratio can be set according to actual needs, and the sum of the ratios is 100%.

[0076] In one possible implementation, obtaining load fitting curves for various load allocation schemes may include:

[0077] For each load distribution scheme, the corresponding load value, load ratio and access method are set based on multiple load characteristics. Based on the load value, access method and load ratio of each node corresponding to the load distribution scheme, the load fitting curve of the load distribution scheme is obtained. The load characteristics include industrial load, commercial load, residential load and agricultural load.

[0078] After setting the load curve type in this embodiment, it is necessary to further perform curve fitting according to four load characteristics to obtain the load fitting curves corresponding to various load allocation schemes. The four load characteristics are defined as: industrial load, commercial load, residential load, and agricultural load. The parameters that need to be set include load value (kW), load percentage (%), and connection method. After determining the various load parameters, the fitted load fitting curve is output. See details... Figure 12 .

[0079] The operation of fitting the load curve involves calculating by superimposing data in a time sequence, that is, adding the data for each corresponding time period to form a new data sequence. The fitting formula can be expressed as: {P1, P2, ..., P...} n}={P i1 +P j1 P i2 +P j2 , ..., P in +P jn}

[0080] In this application embodiment, the role of the load fitting curve design for multiple load access methods is as follows: In reality, the load characteristic curve of a 10KV power grid has uncertainties and diversity, and cannot be replaced by an ideal model. In order to simulate various forms of power grid operation to the greatest extent, the state characteristics of distributed photovoltaic grid access and the state characteristics of load distribution are taken into account, and typical curve types such as average distribution, decreasing distribution, increasing distribution, convex distribution and concave distribution are designed as a way to quickly select in the simulation. At the same time, a custom type is also designed to facilitate the operator to realize and meet more diverse input curve type requirements, thereby improving the scope of application of this application embodiment.

[0081] In step 104, based on the photovoltaic output curve of each photovoltaic access scheme, the load fitting curve of each load distribution scheme, and the distribution network topology model, the voltage over-limit situation of various photovoltaic access distribution network scenarios is simulated and calculated.

[0082] Based on the distribution network topology model constructed in step 101, the photovoltaic output curves for each distributed photovoltaic access scheme constructed in step 102, and the load fitting curves for each load allocation scheme constructed in step 103, the voltage over-limit situations for various photovoltaic access distribution network scenarios are simulated and calculated. The simulation results include raw data (voltage values) and analytical data (voltage over-limit ratio).

[0083] Among them, the determination of voltage over-limit situations: According to the provisions of the national standard "Power Quality Supply Voltage Permissible Deviation", the permissible deviation of three-phase supply voltage of 10KV and below is ±7% of the nominal system voltage.

[0084] In one possible implementation, step 104 may include:

[0085] For each photovoltaic (PV) grid connection scheme, the voltage drop under the sole effect of the distributed PV is simulated and calculated based on the PV output curve and distribution network topology model of the scheme.

[0086] Under this photovoltaic access scheme, based on the distribution network topology model, the load fitting curves of each load allocation scheme, and the voltage drop under the individual action of the distributed photovoltaic, the voltage deviation between the line voltage and the standard line voltage of the distribution network corresponding to each load allocation scheme is simulated and calculated after the photovoltaic access scheme is connected to the distribution network.

[0087] Calculate the percentage of voltage deviation corresponding to each load distribution scheme under this photovoltaic access scheme in the voltage corresponding to the distribution network voltage level, and determine whether the percentage is less than the preset voltage allowable deviation;

[0088] If, under this photovoltaic access scheme, the percentage of voltage deviation corresponding to the load distribution scheme is less than the preset allowable voltage deviation, then it is determined that there is no voltage over-limit situation in the distribution network scenario corresponding to the load distribution scheme under this photovoltaic access scheme.

[0089] If, under the photovoltaic access scheme, the percentage of voltage deviation corresponding to the load distribution scheme is not less than the preset allowable voltage deviation, then it is determined that a voltage over-limit situation has occurred in the distribution network scenario corresponding to the load distribution scheme under the photovoltaic access scheme.

[0090] Based on the distribution network topology model constructed in step 101 and the photovoltaic output curves corresponding to various photovoltaic access schemes constructed in step 102, the voltage drop under the sole action of distributed photovoltaic is simulated and calculated. Then, under the photovoltaic access scheme, based on the distribution network topology model constructed in step 101, the load fitting curves of various load distribution schemes constructed in step 103, and the voltage drop under the sole action of distributed photovoltaic, the voltage deviation between the line voltage and the line standard voltage of the distribution network corresponding to each load distribution scheme after the photovoltaic access scheme is connected to the distribution network is simulated and calculated. Based on the voltage deviation calculated by simulation, the percentage of the voltage in the voltage level corresponding to the distribution network voltage level is calculated, and it is determined whether the percentage is less than the preset voltage allowable deviation. If the percentage is less than the preset voltage allowable deviation, it is determined that there is no voltage limit violation in the distribution network scenario corresponding to the load distribution scheme under the photovoltaic access scheme. If the percentage is not less than the preset voltage allowable deviation, it is determined that there is a voltage limit violation in the distribution network scenario corresponding to the load distribution scheme under the photovoltaic access scheme. In this embodiment, the preset voltage allowable deviation is set to ±7%.

[0091] In one possible implementation, based on the photovoltaic output curve of the photovoltaic access scheme and the distribution network topology model, simulation calculations of the voltage drop under the sole effect of the distributed photovoltaic system can include:

[0092] The voltage drop under the sole effect of this distributed photovoltaic system is calculated using the first formula, which is:

[0093]

[0094] Where, ΔV pvj Let R be the voltage drop at node j under the sole effect of this distributed photovoltaic system, R be the line resistance between adjacent nodes in the distribution network, X be the line reactance between adjacent nodes in the distribution network, and P be the voltage drop at node j. pv Let Q be the active power of the distributed photovoltaic system connected to the i-th node of the distribution network. pv V represents the reactive power of the distributed photovoltaic system connected to the i-th node of the distribution network. N Here, is the standard voltage of the line, j is the j-th node of the distribution network, i is the i-th node of the distribution network, and N is the number of nodes in the distribution network.

[0095] See Figure 2 Before the distributed power system is connected, the voltage drop between two adjacent nodes is:

[0096]

[0097] Where, ΔV n-1，n V is the voltage drop between two adjacent nodes. n-1 V is the voltage at the (n-1)th node. n Let ρ be the voltage at the nth node, Pl be the active power of the load, and Q be the active power of the load. l R is the reactive power of the load, R is the circuit resistance, and X is the line reactance.

[0098] Under the sole action of the system power source, the voltage V at node j in the distribution network j The voltage drop ΔV between the system power supply voltage V0 and the voltage V0 0，j The expression is shown in formula (2):

[0099]

[0100] In this embodiment, when considering the effect of distributed power systems on the distribution network alone, the power supply side of the distribution network needs to be short-circuited first. The impedance in the distribution network lines is relatively small compared to the load, so the effect of distributed power systems on voltage deviation is mainly reflected in the lines before point i. For the lines after point i, distributed power systems have no direct effect on voltage deviation, but due to the connection of distributed power systems, they may have a voltage-raising effect, which will indirectly affect the voltage deviation of each point after point i. Therefore, it is stipulated here that the effect of distributed power systems on voltage drop is negative.

[0101] Based on formulas (1) and (2), and according to the photovoltaic output curve and distribution network topology model of the photovoltaic access scheme, the voltage drop ΔV of node j under the sole action of the distributed photovoltaic system is simulated and calculated. pvj .

[0102] In one possible implementation, based on the distribution network topology model, the load fitting curves for each load allocation scheme, and the voltage drop under the sole effect of the distributed photovoltaic system, simulation calculations are performed to determine the voltage deviation between the line voltage and the standard line voltage of the distribution network corresponding to each load allocation scheme after the photovoltaic system is connected to the distribution network according to the photovoltaic access scheme. This may include:

[0103] The voltage deviation between the line voltage and the standard line voltage of the distribution network corresponding to each load distribution scheme after the photovoltaic access scheme is connected to the distribution network is calculated using the second formula. The second formula is as follows:

[0104]

[0105] Where, ΔU j Vj is the voltage deviation at node j in the distribution network, V0 is the line-start voltage, Pl is the active power of the distribution network load, and Q0 is the voltage deviation at node j in the distribution network. l This refers to the reactive power of the load in the distribution network.

[0106] See Figure 2 Based on formula (2), the voltage deviation ΔU′ at node j of an ideal distribution network without distributed generation systems is calculated. j The calculation formula (3) is as follows:

[0107]

[0108] According to formula (3), using the circuit superposition theorem, the voltage deviation ΔU at node j between the line voltage and the line standard voltage of the distribution network corresponding to each load distribution scheme after the photovoltaic access scheme is connected to the distribution network is simulated and calculated. j .

[0109] As shown in the second formula, the access capacity and location of distributed generation systems both affect the voltage deviation at distribution network nodes. The voltage deviation at nodes on distribution network feeders is closely related to the structural characteristics of the distribution network and the access status of distributed generation systems. However, the access of distributed generation systems always raises the node voltage of the distribution network. When the access capacity of the distributed generation system is small, its output power supply to the load reduces the active and reactive power supplied by the system, thus reducing the voltage deviation on the line. When the access capacity of the distributed generation system increases to a certain value, it may change the direction of active and reactive power on the line, causing the voltage deviation to increase with the increase of the access capacity of the distributed generation system.

[0110] The location, capacity, and type of distributed power source access all affect steady-state voltage deviation: Distributed photovoltaic access at the end of the line will produce a better voltage support effect, and the voltage support effect increases with the increase of capacity; compared with centralized access, decentralized access is less likely to cause voltage over-limit.

[0111] In one possible implementation, if, under the photovoltaic access scheme, the percentage of voltage deviation corresponding to a load distribution scheme is not less than a preset allowable voltage deviation, then after determining that a voltage exceedance has occurred in the distribution network scenario corresponding to the load distribution scheme under the photovoltaic access scheme, the method may further include:

[0112] When it is determined that the distribution network scenario corresponding to the photovoltaic access scheme has exceeded the limit, the voltage at the beginning of the distribution network line is adjusted, or the system power factor of the photovoltaic access scheme is adjusted, or energy storage is added to the distribution network. The photovoltaic output curve, the load fitting curve of each load distribution scheme, and the distribution network topology model are returned, and the step of simulating and calculating the voltage exceeding the limit for various photovoltaic access distribution network scenarios continues until the percentage of voltage deviation corresponding to a load distribution scheme is less than the preset voltage allowable deviation. It is then determined that there is no voltage exceeding the limit for the distribution network scenario corresponding to the load distribution scheme under the photovoltaic access scheme.

[0113] When it is determined that the distribution network scenario corresponding to the photovoltaic access scheme has exceeded the limit, the system power factor of the photovoltaic access scheme and any one of the following is adjusted: the line starting voltage V0 of the distribution network, the system power factor of the photovoltaic access scheme and energy storage. Then, the process returns to step 104 and continues until the percentage of voltage deviation corresponding to the load distribution scheme is less than the preset voltage allowable deviation, i.e., less than ±7%. In this case, it is determined that there is no voltage exceeding the limit in the distribution network scenario corresponding to the load distribution scheme under the photovoltaic access scheme.

[0114] In one possible implementation, after acquiring and constructing multiple distributed photovoltaic grid connection schemes, the method may further include:

[0115] Construct various configuration ratio distribution patterns of energy storage facilities in the power distribution network, and obtain the charging and discharging strategy curves for various configuration ratio distribution patterns; the configuration ratio distribution patterns include access location and access capacity.

[0116] Accordingly, step 104 may include:

[0117] Based on the photovoltaic output curves of each photovoltaic access scheme, the charging and discharging strategy curves of each energy storage facility in the distribution network, the load fitting curves of each load allocation scheme, and the distribution network topology model, the voltage over-limit situations of various photovoltaic access distribution network scenarios are simulated and calculated.

[0118] In this embodiment, the energy storage is an electrochemical energy storage battery. The battery has the functions of charging and discharging and is an electrical energy storage unit. Its function is to store electrical energy when the system power supply is sufficient and the power balance is in surplus, and to discharge when the system power supply is insufficient to provide power to the system.

[0119] See Figure 8 In this embodiment, the configuration ratio distribution of energy storage facilities at each node is the same as that of the distributed photovoltaic (PV) grid connection scheme. The configuration ratio distribution includes both the grid connection location and the grid connection capacity. Similarly, the design of the charge / discharge strategy curves for various configuration ratio distributions includes both preset and custom options, which is the same as the setting of the PV output curve corresponding to the distributed PV grid connection scheme. (See [link to relevant documentation]). Figure 7 It is important to note that the energy storage configuration ratio data tracks the access capacity data of distributed photovoltaic (PV) grid connection schemes.

[0120] Accordingly, when simulating voltage over-limit situations in various photovoltaic grid connection scenarios, in addition to step 104, it is also necessary to add the charging and discharging strategy curve of the configuration ratio distribution of each energy storage facility in the grid to make the simulation results more accurate.

[0121] The difference between distributed photovoltaic and energy storage in this application embodiment is that when photovoltaic power generation is in surplus, energy storage charges; when photovoltaic power generation is insufficient or not generated, energy storage discharges. The two are used in combination to provide a continuous power supply to the system, and to a certain extent solve the fluctuations and peak impacts caused by the unstable photovoltaic output state.

[0122] This application provides a method for calculating voltage exceedance after photovoltaic (PV) access to a distribution network. By constructing a distribution network topology model, and building various distributed PV access schemes and load distribution schemes based on the distribution network topology model, the method simulates and calculates voltage exceedance scenarios for various PV access scenarios based on the obtained PV output curves of various PV access schemes, load fitting curves of various load distribution schemes, and the distribution network topology model. This method enables the simulation of various operating states of the distribution network on a single simulation model. Furthermore, the distribution network topology model has rich components, comprehensive scenarios, and strong applicability and reproducibility.

[0123] The following implementation example illustrates the voltage over-limit calculation method for photovoltaic grid connection described above.

[0124] Simulation calculations are performed using a concave load distribution as an example.

[0125] The first step is to set the photovoltaic output curve and load fitting curve, and calculate the voltage value of each node.

[0126] Table 1. Photovoltaic Output and Overall Load

[0127]

[0128]

[0129] The maximum load is 2384kW, occurring at 14:00, and the minimum load is 376kW, occurring at 2:00 and 3:00. Based on the maximum allowable active power of 8833kW, the maximum load rate of the line is 26.99%.

[0130] The load is distributed in a convex shape along the line, and the time-series load at each time point is as follows:

[0131] Table 2. Time-series load (kW) at each node

[0132]

[0133] The second step is to monitor the voltage of each node after the distributed photovoltaic system is connected to the distribution network. The photovoltaic capacity is 4768 kW (tw times the maximum load). The timing voltage of the nodes is shown in Table 3. Some nodes experienced overvoltage, and the highest voltage occurred at 7 o'clock.

[0134] Table 3. Time-series voltages (kV) at each node when photovoltaic power is connected to twice the maximum load.

[0135]

[0136] At this point, a voltage limit violation occurred at 7:00 AM. The highest and lowest voltage values ​​for each node are shown in Table 4.

[0137] Table 4. Maximum and minimum voltages (kV) at each node when photovoltaic power is connected to twice the maximum load.

[0138]

[0139] The number of nodes that exceed the limit and the ratio of nodes that exceed the limit are shown in Table 5.

[0140] Table 5. Exceeding Nodes and Exceeding Proportions When Photovoltaic Connection Reaches 2 Times Maximum Load

[0141]

[0142] The third step is power monitoring. The active power flowing through the beginning (inflow line) and end (outflow line) of each line is shown in Table 6. The maximum reverse active power is 4378.38kW and the maximum reverse load rate is 49.57%.

[0143] Table 6. Time-series power (kW) of each branch when photovoltaic power is connected at twice the maximum load.

[0144]

[0145] Step 4: Analysis of solutions for voltage exceeding limits

[0146] (1) Adjusting the voltage at the beginning of the distribution network lines

[0147] The problem of voltage exceeding limits can be solved by adjusting the voltage, as shown in Table 7.

[0148] Table 7 shows how to solve the voltage over-limit problem by adjusting the starting voltage.

[0149]

[0150] The changes in the maximum voltage at each node during the initial voltage adjustment process are shown in Table 8.

[0151] Table 8. Changes in the highest voltage at each node when adjusting the starting voltage.

[0152]

[0153] (2) Adjusting the system power factor of the photovoltaic access scheme

[0154] The problem of voltage exceeding limits can be solved by adjusting the photovoltaic power factor, as shown in Table 9.

[0155] Table 9 shows how to solve the voltage limit problem by adjusting the photovoltaic power factor.

[0156]

[0157] The changes in the maximum voltage at each node during the power factor adjustment process are shown in Table 10.

[0158] Table 10 shows the changes in maximum voltage at each node during the adjustment of photovoltaic power factor.

[0159]

[0160] (3) Increase energy storage

[0161] The problem of voltage exceeding limits can be solved by adding energy storage on the line, as shown in Table 11.

[0162] Table 11 shows how to solve voltage over-limit problems by increasing energy storage.

[0163]

[0164] The changes in the maximum voltage at each node during the energy storage capacity adjustment process are shown in Table 12.

[0165] Table 12: Changes in the highest voltage at each node during the addition of energy storage.

[0166]

[0167] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0168] The following are device embodiments of this application. For details not described in detail, please refer to the corresponding method embodiments described above.

[0169] Figure 13 A schematic diagram of the voltage over-limit calculation device after photovoltaic grid connection provided in an embodiment of this application is shown. For ease of explanation, only the parts related to the embodiment of this application are shown, and are described in detail below:

[0170] like Figure 13 As shown, the voltage over-limit calculation device 13 after photovoltaic grid connection includes:

[0171] Module 131 is used to obtain voltage source parameters, line parameters, and transformer parameters of the distribution network and construct the distribution network topology model.

[0172] The first setting module 132 is used to construct various distributed photovoltaic access schemes and obtain the photovoltaic output curves of various photovoltaic access schemes; the distributed photovoltaic access schemes include the access location and access capacity;

[0173] The second setting module 133 is used to construct multiple load allocation schemes and obtain load fitting curves for each load allocation scheme; the load allocation scheme includes the load ratio allocated to each node of the distribution network;

[0174] The calculation module 134 is used to simulate and calculate the voltage over-limit situation of various photovoltaic access distribution network scenarios based on the photovoltaic output curve of each photovoltaic access scheme, the load fitting curve of each load distribution scheme and the distribution network topology model.

[0175] This application provides a voltage limit calculation device for photovoltaic (PV) grid connections. By constructing a grid topology model, and building various distributed PV access schemes and load distribution schemes based on the grid topology model, the device simulates and calculates voltage limit violations in various PV grid connection scenarios based on the obtained PV output curves of various PV access schemes, load fitting curves of various load distribution schemes, and the grid topology model. This allows for the simulation of various operating states of the grid on a single simulation model. Furthermore, the grid topology model has rich components, comprehensive scenarios, and strong applicability and reproducibility.

[0176] In one possible implementation, the building module can specifically be used for:

[0177] Set up voltage sources, distribution network feeders, distributed photovoltaic access points, distribution transformer access points, and voltage detection points, and draw the topology of the distribution network;

[0178] Based on the obtained voltage source parameters, line parameters, and transformer parameters of the distribution network, parameters are set for the topology of the distribution network to construct a distribution network topology model;

[0179] Among them, voltage source parameters include voltage level, actual operating voltage, resistance, reactance, and impedance; line parameters include conductor type, resistance per unit length, reactance per unit length, and susceptance per unit length; distribution transformer parameters include rated capacity, short-circuit voltage percentage, short-circuit loss, no-load loss, no-load current percentage, number of taps in the high-voltage side tap range, unit adjustment of the high-voltage side tap, and current tap position on the high-voltage side.

[0180] In one possible implementation, distributed photovoltaic (PV) access schemes include centralized front-end distribution, centralized mid-end distribution, centralized back-end distribution, uniform distribution, and custom distribution;

[0181] After building the modules, the device may also include:

[0182] The third setting module is used to set the preset percentage of the maximum allowable reverse load rate after various distributed photovoltaic systems are connected to the distribution network; the preset percentage of the maximum allowable reverse load rate is used to prevent load backflow after distributed photovoltaic systems are connected to the distribution network.

[0183] In one possible implementation, the load distribution scheme includes average distribution, decreasing distribution, increasing distribution, convex distribution, concave distribution, and custom distribution;

[0184] The second settings module can be used for:

[0185] For each load distribution scheme, the corresponding load value, load ratio and access method are set based on multiple load characteristics. Based on the load value, access method and load ratio of each node corresponding to the load distribution scheme, the load fitting curve of the load distribution scheme is obtained. The load characteristics include industrial load, commercial load, residential load and agricultural load.

[0186] In one possible implementation, the computation module can specifically be used for:

[0187] For each photovoltaic (PV) grid connection scheme, the voltage drop under the sole effect of the distributed PV is simulated and calculated based on the PV output curve and distribution network topology model of the scheme.

[0188] Under this photovoltaic access scheme, based on the distribution network topology model, the load fitting curves of each load allocation scheme, and the voltage drop under the individual action of the distributed photovoltaic, the voltage deviation between the line voltage and the standard line voltage of the distribution network corresponding to each load allocation scheme is simulated and calculated after the photovoltaic access scheme is connected to the distribution network.

[0189] Calculate the percentage of voltage deviation corresponding to each load distribution scheme under this photovoltaic access scheme in the voltage corresponding to the distribution network voltage level, and determine whether the percentage is less than the preset voltage allowable deviation;

[0190] If, under this photovoltaic access scheme, the percentage of voltage deviation corresponding to the load distribution scheme is less than the preset allowable voltage deviation, then it is determined that there is no voltage over-limit situation in the distribution network scenario corresponding to the load distribution scheme under this photovoltaic access scheme.

[0191] If, under the photovoltaic access scheme, the percentage of voltage deviation corresponding to the load distribution scheme is not less than the preset allowable voltage deviation, then it is determined that a voltage over-limit situation has occurred in the distribution network scenario corresponding to the load distribution scheme under the photovoltaic access scheme.

[0192] In one possible implementation, after the computing module, the device may further include:

[0193] The adjustment module is used to adjust the line-end voltage of the distribution network when it is determined that the distribution network scenario corresponding to the photovoltaic access scheme has exceeded the limit. Alternatively, it can adjust the system power factor of the photovoltaic access scheme or add energy storage in the distribution network. The module returns the photovoltaic output curve, the load fitting curve and the distribution network topology model based on each photovoltaic access scheme. The simulation calculation of voltage limit exceeding situations for various photovoltaic access distribution network scenarios continues until the percentage of voltage deviation corresponding to a load distribution scheme is less than the preset voltage allowable deviation. At this point, it is determined that there is no voltage limit exceeding situation in the distribution network scenario corresponding to the load distribution scheme under the photovoltaic access scheme.

[0194] In one possible implementation, based on the photovoltaic output curve of the photovoltaic access scheme and the distribution network topology model, simulation calculations of the voltage drop under the sole effect of the distributed photovoltaic system can include:

[0195] The voltage drop under the sole effect of this distributed photovoltaic system is calculated using the first formula, which is:

[0196]

[0197] Where, ΔV pvj Let R be the voltage drop at node j under the sole effect of this distributed photovoltaic system, R be the line resistance between adjacent nodes in the distribution network, X be the line reactance between adjacent nodes in the distribution network, and P be the voltage drop at node j. pv Let Q be the active power of the distributed photovoltaic system connected to the i-th node of the distribution network. pv V represents the reactive power of the distributed photovoltaic system connected to the i-th node of the distribution network. N Here, is the standard voltage of the line, j is the j-th node of the distribution network, i is the i-th node of the distribution network, and N is the number of nodes in the distribution network;

[0198] Based on the distribution network topology model, the load fitting curves for each load allocation scheme, and the voltage drop under the sole effect of the distributed photovoltaic system, the simulation calculation is performed to determine the voltage deviation between the line voltage and the standard line voltage of the distribution network corresponding to each load allocation scheme after the photovoltaic system is connected to the distribution network according to the photovoltaic access scheme. This can include:

[0199] The voltage deviation between the line voltage and the standard line voltage of the distribution network corresponding to each load distribution scheme after the photovoltaic access scheme is connected to the distribution network is calculated using the second formula. The second formula is as follows:

[0200]

[0201] Where, ΔU j V is the voltage deviation at node j in the distribution network, V0 is the voltage at the beginning of the line, and P is the voltage deviation at node j. l Q represents the active power of the load in the distribution network.l This refers to the reactive power of the load in the distribution network.

[0202] In one possible implementation, after the first setting module, the device may further include:

[0203] The fourth configuration module is used to construct the configuration ratio distribution patterns of various energy storage facilities in the distribution network and obtain the charging and discharging strategy curves of various configuration ratio distribution patterns; the configuration ratio distribution patterns include access location and access capacity.

[0204] Accordingly, the calculation module can be used for:

[0205] Based on the photovoltaic output curves of each photovoltaic access scheme, the charging and discharging strategy curves of each energy storage facility in the distribution network, the load fitting curves of each load allocation scheme, and the distribution network topology model, the voltage over-limit situations of various photovoltaic access distribution network scenarios are simulated and calculated.

[0206] Figure 14 This is a schematic diagram of the terminal provided in an embodiment of this application. For example... Figure 14 As shown, the terminal 14 in this embodiment includes: a processor 140, a memory 141, and a computer program 142 stored in the memory 141 and executable on the processor 140. When the processor 140 executes the computer program 142, it implements the steps in the above embodiments of the voltage over-limit calculation method after photovoltaic grid connection, for example... Figure 1 Steps 101 to 104 are shown. Alternatively, when the processor 140 executes the computer program 142, it implements the functions of each module in the above-described device embodiments, for example... Figure 13 The functions of modules 131 to 134 are shown.

[0207] For example, the computer program 142 can be divided into one or more modules, which are stored in the memory 141 and executed by the processor 140 to complete this application. The one or more modules / units can be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program 142 in the terminal 14. For example, the computer program 142 can be divided into... Figure 13 Modules 131 to 134 are shown.

[0208] The terminal 14 may be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. The terminal 14 may include, but is not limited to, a processor 140 and a memory 141. Those skilled in the art will understand that... Figure 14This is merely an example of terminal 14 and does not constitute a limitation on terminal 14. It may include more or fewer components than shown, or combine certain components, or different components. For example, the terminal may also include input / output devices, network access devices, buses, etc.

[0209] The processor 140 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0210] The memory 141 can be an internal storage unit of the terminal 14, such as a hard disk or memory of the terminal 14. The memory 141 can also be an external storage device of the terminal 14, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the terminal 14. Furthermore, the memory 141 can include both internal storage units and external storage devices of the terminal 14. The memory 141 is used to store the computer program and other programs and data required by the terminal. The memory 141 can also be used to temporarily store data that has been output or will be output.

[0211] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0212] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0213] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0214] In the embodiments provided in this application, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling or direct coupling or communication connection may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0215] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0216] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0217] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above-described embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium. When executed by a processor, the computer program can implement the steps of the voltage over-limit calculation method embodiments for photovoltaic grid connection described above. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc. It should be noted that the content contained in the computer-readable medium may be appropriately added to or subtracted from the content as required by the legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium may not include electrical carrier signals and telecommunication signals.

[0218] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for calculating voltage exceedances after photovoltaic power is connected to a distribution network, characterized in that, The calculation method includes: Obtain the voltage source parameters, line parameters, and transformer parameters of the distribution network, and construct the distribution network topology model; Multiple distributed photovoltaic (PV) grid connection schemes are constructed, and PV output curves for each scheme are obtained; the distributed PV grid connection schemes include grid connection location and grid connection capacity. Multiple load allocation schemes are constructed, and load fitting curves for each scheme are obtained; the load allocation scheme includes the load proportion allocated to each node of the distribution network. Based on the photovoltaic output curve of each photovoltaic access scheme, the load fitting curve of each load distribution scheme, and the distribution network topology model, the voltage over-limit situation of various photovoltaic access distribution network scenarios is simulated and calculated. The voltage drop under the sole effect of this distributed photovoltaic system is calculated using the first formula, which is: in, For the nodes under the sole action of this distributed photovoltaic system Voltage drop, The resistance value of the line between adjacent nodes of the power distribution network. The line reactance value between adjacent nodes of the distribution network. For the first in the distribution network The active power of distributed photovoltaic systems connected to each node. For the first distribution network The reactive power of distributed photovoltaic systems connected to each node. This is the standard voltage for the line. For the first distribution network 1 node For the first distribution network 1 node The number of nodes in the power distribution network; The voltage deviation between the line voltage and the standard line voltage of the distribution network corresponding to each load distribution scheme after the photovoltaic access scheme is connected to the distribution network is calculated using the second formula: in, For the nodes of the distribution network Voltage deviation, This is the voltage at the beginning of the line. The active power of the load in the aforementioned distribution network. The reactive power of the load in the distribution network is denoted as .

2. The voltage over-limit calculation method after photovoltaic grid connection according to claim 1, characterized in that, The process of obtaining voltage source parameters, line parameters, and distribution transformer parameters of the distribution network, and constructing a distribution network topology model, includes: Set up voltage sources, distribution network feeders, distributed photovoltaic access points, distribution transformer access points, and voltage detection points, and draw the topology of the distribution network; Based on the obtained voltage source parameters, line parameters, and transformer parameters of the distribution network, parameters are set for the topology of the distribution network to construct a distribution network topology model; The voltage source parameters include voltage level, actual operating voltage, resistance, reactance, and impedance; the line parameters include conductor type, resistance per unit length, reactance per unit length, and susceptance per unit length; the transformer parameters include rated capacity, short-circuit voltage percentage, short-circuit loss, no-load loss, no-load current percentage, number of taps in the high-voltage side tap range, unit adjustment of the high-voltage side tap, and the current tap position on the high-voltage side.

3. The voltage over-limit calculation method after photovoltaic grid connection according to claim 1, characterized in that, The distributed photovoltaic (PV) access schemes include front-end distribution, mid-end distribution, back-end distribution, uniform distribution, and custom distribution; after acquiring and constructing multiple distributed PV access schemes, the method further includes: The preset percentage of the maximum allowable reverse load rate after various distributed photovoltaic (PV) systems are connected to the distribution network is set; the preset percentage of the maximum allowable reverse load rate is used to prevent load backfeeding after distributed PV systems are connected to the distribution network.

4. The voltage over-limit calculation method after photovoltaic grid connection according to claim 1, characterized in that, The load distribution schemes include average distribution, decreasing distribution, increasing distribution, convex distribution, concave distribution, and custom distribution; The process of obtaining load fitting curves for various load allocation schemes includes: For each load distribution scheme, corresponding load values, load ratios, and access methods are set based on multiple load characteristics. Based on the load values, access methods, and load ratios of each node corresponding to the load distribution scheme, the load fitting curve of the load distribution scheme is obtained. The load characteristics include industrial load, commercial load, residential load, and agricultural load.

5. The voltage over-limit calculation method after photovoltaic grid connection according to claim 1, characterized in that, The photovoltaic output curves for each photovoltaic access scheme, the load fitting curves for each load distribution scheme, and the distribution network topology model are used to simulate and calculate voltage exceedance scenarios for various photovoltaic access distribution network conditions, including: For each photovoltaic (PV) grid connection scheme, the voltage drop under the sole effect of the distributed PV is simulated and calculated based on the PV output curve of the PV grid connection scheme and the distribution network topology model. Under this photovoltaic access scheme, based on the distribution network topology model, the load fitting curve of each load allocation scheme, and the voltage drop under the action of the distributed photovoltaic alone, the voltage deviation between the line voltage and the line standard voltage of the distribution network corresponding to each load allocation scheme is simulated and calculated after the photovoltaic access scheme is connected to the distribution network. Calculate the percentage of the voltage deviation corresponding to each load distribution scheme under the photovoltaic access scheme in the voltage corresponding to the voltage level of the distribution network, and determine whether the percentage is less than the preset voltage allowable deviation; If, under the photovoltaic access scheme, the percentage of voltage deviation corresponding to the load distribution scheme is less than the preset allowable voltage deviation, then it is determined that there is no voltage limit violation in the distribution network scenario corresponding to the load distribution scheme under the photovoltaic access scheme. If, under the photovoltaic access scheme, the percentage of voltage deviation corresponding to a load distribution scheme is not less than the preset allowable voltage deviation, then it is determined that a voltage over-limit situation has occurred in the distribution network scenario corresponding to the load distribution scheme under the photovoltaic access scheme.

6. The voltage over-limit calculation method after photovoltaic grid connection according to claim 5, characterized in that, If, under the photovoltaic access scheme, the percentage of voltage deviation corresponding to a load distribution scheme is not less than the preset allowable voltage deviation, then after determining that a voltage exceedance situation has occurred in the distribution network scenario corresponding to the load distribution scheme under the photovoltaic access scheme, the method further includes: When it is determined that the distribution network scenario corresponding to the photovoltaic access scheme has exceeded the limit, the voltage at the beginning of the line of the distribution network is adjusted, or the system power factor of the photovoltaic access scheme is adjusted, or energy storage is added to the distribution network. The steps of simulating and calculating the voltage exceeding the limit for various photovoltaic access distribution network scenarios are returned based on the photovoltaic output curve of each photovoltaic access scheme, the load fitting curve of each load distribution scheme, and the distribution network topology model. The process continues until the percentage of voltage deviation corresponding to a load distribution scheme is less than the preset voltage allowable deviation. It is then determined that there is no voltage exceeding the limit for the distribution network scenario corresponding to the load distribution scheme under the photovoltaic access scheme.

7. The voltage over-limit calculation method after photovoltaic grid connection according to claim 3, characterized in that, After acquiring and constructing multiple distributed photovoltaic access schemes, the method further includes: The configuration ratio distribution of various energy storage facilities in the power distribution network is constructed, and the charging and discharging strategy curves of various configuration ratio distributions are obtained; the configuration ratio distribution includes the access location and access capacity. Accordingly, based on the photovoltaic output curve for each photovoltaic access scheme, the load fitting curve for each load distribution scheme, and the distribution network topology model, the simulation calculation of voltage exceedance scenarios for various photovoltaic access distribution network scenarios includes: Based on the photovoltaic output curves of each photovoltaic access scheme, the charging and discharging strategy curves of each energy storage facility in the distribution network configuration ratio, the load fitting curves of each load allocation scheme, and the distribution network topology model, the voltage over-limit situation of various photovoltaic access distribution network scenarios is simulated and calculated.

8. A terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the voltage over-limit calculation method after photovoltaic grid connection as described in any one of claims 1 to 7.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the voltage over-limit calculation method after photovoltaic grid connection as described in any one of claims 1 to 7.

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