Power grid short-circuit ratio calculation method and device considering distributed photovoltaic influence

Abstract

The invention is suitable for the technical field of electric power, and provides a power grid short-circuit ratio calculation method and device considering distributed photovoltaic influence, and the method comprises the steps: obtaining equipment parameters, distributed photovoltaic output parameters and load parameters of a power grid, and building a distributed photovoltaic and load balanced distribution power grid simulation calculation model according to the obtained parameters; determining a power transfer coefficient of each photovoltaic feed-in node in the power grid simulation calculation model; respectively setting the power grid simulation calculation model to be in different operation scenes; in each operation scene, calculating a short-circuit ratio related index of each photovoltaic feed-in node, and determining a short-circuit ratio of each photovoltaic feed-in node in the operation scene according to the short-circuit ratio related index of each photovoltaic feed-in node and the power transfer coefficient; and determining the short-circuit ratio of the power grid based on the short-circuit ratio of each photovoltaic feed-in node in each operation scene. The problem of calculation deviation caused by the fact that distributed photovoltaic influence is not considered in existing power grid short-circuit ratio calculation can be solved.

Description

Technical Field

[0001] The present invention belongs to the field of electric power technology, and in particular relates to a method and a device for calculating the short-circuit ratio of a power grid taking into account the influence of distributed photovoltaics. Background Art

[0002] In recent years, my country's distributed photovoltaic power generation has been connected to the power grid on a large scale. As the proportion of new energy in the system continues to increase, new energy has been integrated into weak AC power grids in some areas. This is one of the factors that cause problems such as broadband oscillation and overvoltage, which brings challenges to the operation of the power grid. Compared with thermal power units, distributed photovoltaic units have a smaller short-circuit current, which leads to a decrease in the short-circuit ratio of the power grid, a sharp drop in voltage support capacity, and a prominent problem of static voltage stability in the power grid.

[0003] At present, relevant standards stipulate that the short-circuit ratio of new energy stations should reach a reasonable level, but the short-circuit ratio of the power grid is affected by the distributed photovoltaic operation scenario and has time-varying characteristics, making it difficult to accurately quantify and calculate. Studying the calculation method of the short-circuit ratio of the power grid containing distributed photovoltaics under multiple operation scenarios is of great significance for accurately quantifying the short-circuit ratio of active power grids and analyzing the static stability of power grid voltage. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a method and device for calculating the short-circuit ratio of a power grid taking into account the influence of distributed photovoltaics, so as to solve the problem of calculation deviation caused by the existing calculation of the short-circuit ratio of the power grid not taking into account the influence of distributed photovoltaics.

[0005] A first aspect of an embodiment of the present invention provides a method for calculating a short-circuit ratio of a power grid, comprising:

[0006] Obtaining grid parameters of the power grid, and building a distributed photovoltaic and load balanced distribution grid simulation calculation model based on the grid parameters;

[0007] Determining the power transfer coefficient of each photovoltaic feed-in node in the power grid simulation calculation model;

[0008] The power grid simulation calculation model is respectively set in different operation scenarios;

[0009] Under each operation scenario, the short-circuit ratio related index of each photovoltaic feed-in node is calculated, and the short-circuit ratio of each photovoltaic feed-in node under the operation scenario is determined according to the short-circuit ratio related index and the power transfer coefficient of each photovoltaic feed-in node;

[0010] The short-circuit ratio of the power grid is determined based on the short-circuit ratio of each photovoltaic feed-in node under each operation scenario.

[0011] In combination with the first aspect, in a possible implementation of the first aspect, the grid parameters include: distributed photovoltaic and load;

[0012] The method of building a distributed photovoltaic and load balanced distribution grid simulation calculation model according to the grid parameters includes:

[0013] Build a power grid simulation model containing multiple nodes and multiple lines;

[0014] The distributed photovoltaic and the load are evenly distributed to each photovoltaic feed-in node in the power grid simulation calculation model to obtain a power grid simulation calculation model with balanced distribution of distributed photovoltaic and load; wherein the photovoltaic feed-in nodes are: all nodes except the nodes connected to the main grid.

[0015] In combination with the first aspect, in a possible implementation manner of the first aspect, determining the power transfer coefficient of each photovoltaic feed-in node in the power grid simulation calculation model includes:

[0016] Determining the self-impedance matrix of each photovoltaic feed-in node and the mutual impedance matrix between each photovoltaic feed-in node and other photovoltaic feed-in nodes according to the grid structure of the power grid simulation calculation model;

[0017] Based on the self-impedance matrix of each photovoltaic feeding node and the mutual impedance matrix between each photovoltaic feeding node and other photovoltaic feeding nodes, the power transfer coefficient of each photovoltaic feeding node is determined.

[0018] In combination with the first aspect, in a possible implementation of the first aspect, the operation scenarios include: a forward flow scenario, a reverse flow scenario, and an on-site balancing scenario;

[0019] The respectively setting the power grid simulation calculation model to different operation scenarios includes:

[0020] By setting the coefficient of distributed photovoltaic power generation, the distributed photovoltaic power generation power is made smaller than the load power consumption, and at this time, the power grid simulation calculation model is in the positive power flow scenario;

[0021] By setting the coefficient of distributed photovoltaic power generation, the distributed photovoltaic power generation power is made greater than the load power consumption, and at this time, the power grid simulation calculation model is in the power flow reverse transmission scenario;

[0022] By setting the coefficient of the distributed photovoltaic power generation power, the distributed photovoltaic power generation power is equal to the load power consumption. At this time, the power grid simulation calculation model is in the local balance scenario.

[0023] In combination with the first aspect, in a possible implementation of the first aspect, in each operation scenario, calculating the short-circuit ratio-related index of each photovoltaic feed-in node includes:

[0024] In each operation scenario, a three-phase short-circuit fault is set on each photovoltaic feed-in node in turn, and the short-circuit ratio related indicators of each photovoltaic feed-in node are simulated and calculated;

[0025] Among them, the short-circuit ratio related indicators include: short-circuit current and short-circuit capacity.

[0026] In combination with the first aspect, in a possible implementation of the first aspect, determining the short circuit ratio of each photovoltaic feed-in node in the operation scenario according to the short circuit ratio related index and the power transfer coefficient of each photovoltaic feed-in node includes:

[0027] according to Determine the short-circuit ratio of each photovoltaic feed-in node under the operating scenario;

[0028] Among them, K SCRi is the short-circuit ratio of the i-th photovoltaic feed-in node; S i is the capacity of the i-th photovoltaic feed-in node; P i is the photovoltaic feed-in power of the i-th photovoltaic feed-in node; P j is the photovoltaic feed-in power of the jth photovoltaic feed-in node; K i,j is the power transfer coefficient of the jth PV feed-in node.

[0029] In combination with the first aspect, in a possible implementation of the first aspect, determining the short-circuit ratio of the power grid based on the short-circuit ratio of each photovoltaic feed-in node in each operating scenario includes:

[0030] Determine the minimum short-circuit ratio of each PV feed-in node in each scenario;

[0031] Based on the minimum short-circuit ratio under various operating scenarios, the short-circuit ratio of the power grid is determined by the geometric mean method.

[0032] In combination with the first aspect, in a possible implementation of the first aspect, determining the power transfer coefficient of each photovoltaic feed-in node based on the self-impedance matrix of each photovoltaic feed-in node and the mutual impedance matrix between each photovoltaic feed-in node and other photovoltaic feed-in nodes includes:

[0033] based on Determine the power transfer coefficient of each photovoltaic feed-in node;

[0034] Among them, K i,j is the power transfer coefficient of photovoltaic feed-in node j; Z i,i is the self-impedance matrix of photovoltaic feed-in node i; Z i,j is the mutual impedance matrix between photovoltaic feeding node i and photovoltaic feeding node j.

[0035] A second aspect of an embodiment of the present invention provides a power grid short-circuit ratio calculation device taking into account the influence of distributed photovoltaics, including:

[0036] Establish a module for obtaining grid parameters of the grid, and build a grid simulation calculation model for distributed photovoltaic and load balanced distribution according to the grid parameters;

[0037] A determination module, used to determine the power transfer coefficient of each photovoltaic feed-in node in the power grid simulation calculation model;

[0038] A setting module, used to respectively set the power grid simulation calculation model to different operation scenarios;

[0039] The calculation module is used to calculate the short-circuit ratio related indicators of each photovoltaic feed-in node in each operation scenario, and determine the short-circuit ratio of each photovoltaic feed-in node in the operation scenario according to the short-circuit ratio related indicators and the power transfer coefficient of each photovoltaic feed-in node; based on the short-circuit ratio of each photovoltaic feed-in node in each operation scenario, determine the short-circuit ratio of the power grid.

[0040] In conjunction with the second aspect, in a possible implementation of the second aspect, the grid parameters include: distributed photovoltaics and loads;

[0041] The establishment module is specifically used for:

[0042] Build a power grid simulation model containing multiple nodes and multiple lines;

[0043] The distributed photovoltaic and the load are evenly distributed to each photovoltaic feed-in node in the power grid simulation calculation model to obtain a power grid simulation calculation model with balanced distribution of distributed photovoltaic and load; wherein the photovoltaic feed-in nodes are: all nodes except the nodes connected to the main grid.

[0044] In conjunction with the second aspect, in a possible implementation manner of the second aspect, the determining module is specifically configured to:

[0045] Determining the self-impedance matrix of each photovoltaic feed-in node and the mutual impedance matrix between each photovoltaic feed-in node and other photovoltaic feed-in nodes according to the grid structure of the power grid simulation calculation model;

[0046] Based on the self-impedance matrix of each photovoltaic feeding node and the mutual impedance matrix between each photovoltaic feeding node and other photovoltaic feeding nodes, the power transfer coefficient of each photovoltaic feeding node is determined.

[0047] In conjunction with the second aspect, in a possible implementation of the second aspect, the operation scenarios include: a forward flow scenario, a reverse flow scenario, and an on-site balancing scenario;

[0048] The setting module is specifically used for:

[0049] By setting the coefficient of distributed photovoltaic power generation, the distributed photovoltaic power generation power is made smaller than the load power consumption, and at this time, the power grid simulation calculation model is in the positive power flow scenario;

[0050] By setting the coefficient of distributed photovoltaic power generation, the distributed photovoltaic power generation power is made greater than the load power consumption, and at this time, the power grid simulation calculation model is in the power flow reverse transmission scenario;

[0051] By setting the coefficient of the distributed photovoltaic power generation power, the distributed photovoltaic power generation power is equal to the load power consumption. At this time, the power grid simulation calculation model is in the local balance scenario.

[0052] In conjunction with the second aspect, in a possible implementation manner of the second aspect, the calculation module is specifically used to:

[0053] In each operation scenario, a three-phase short-circuit fault is set on each photovoltaic feed-in node in turn, and the short-circuit ratio related indicators of each photovoltaic feed-in node are simulated and calculated;

[0054] Among them, the short-circuit ratio related indicators include: short-circuit current and short-circuit capacity.

[0055] In conjunction with the second aspect, in a possible implementation manner of the second aspect, the calculation module is specifically used to:

[0056] according to Determine the short-circuit ratio of each photovoltaic feed-in node under the operating scenario;

[0057] Among them, K SCRi is the short-circuit ratio of the i-th photovoltaic feed-in node; S i is the capacity of the i-th photovoltaic feed-in node; P i is the photovoltaic feed-in power of the i-th photovoltaic feed-in node; P j is the photovoltaic feed-in power of the jth photovoltaic feed-in node; K i,j is the power transfer coefficient of the jth PV feed-in node.

[0058] In conjunction with the second aspect, in a possible implementation manner of the second aspect, the calculation module is specifically used to:

[0059] Determine the minimum short-circuit ratio of each PV feed-in node in each scenario;

[0060] Based on the minimum short-circuit ratio under various operating scenarios, the short-circuit ratio of the power grid is determined by the geometric mean method.

[0061] In conjunction with the second aspect, in a possible implementation manner of the second aspect, the determining module is specifically configured to:

[0062] based on Determine the power transfer coefficient of each photovoltaic feed-in node;

[0063] Among them, K i,j is the power transfer coefficient of photovoltaic feed-in node j; Z i,i is the self-impedance matrix of photovoltaic feed-in node i; Z i,j is the mutual impedance matrix between photovoltaic feeding node i and photovoltaic feeding node j.

[0064] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0065] The embodiment of the present invention builds a distributed photovoltaic and load balanced distribution power grid simulation calculation model, determines the power transfer coefficient of each photovoltaic feed-in node in the power grid simulation calculation model, respectively sets the power grid simulation calculation model in different operation scenarios, calculates the short-circuit ratio related indicators of each photovoltaic feed-in node in each operation scenario, and determines the short-circuit ratio of each photovoltaic feed-in node in the operation scenario based on the short-circuit ratio related indicators and power transfer coefficient of each photovoltaic feed-in node, and finally determines the short-circuit ratio of the power grid based on the short-circuit ratio of each photovoltaic feed-in node in each operation scenario. The embodiment of the present invention comprehensively considers the short-circuit ratio of different operation scenarios in the power grid, thereby refining the calculation and analysis of the voltage stability of the power grid, solves the calculation deviation problem caused by the existing power grid short-circuit ratio calculation not considering the influence of distributed photovoltaics, and realizes the accurate calculation of the short-circuit ratio of the power grid containing distributed photovoltaics, which is of great significance for quantifying the short-circuit ratio of the active power grid and analyzing the static stability of the power grid voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0067] Figure 1 It is a schematic diagram of the implementation flow of a method for calculating the short-circuit ratio of a power grid taking into account the influence of distributed photovoltaic power generation provided in an embodiment of the present invention;

[0068] Figure 2 Schematic diagram of a power grid simulation calculation model provided by an embodiment of the present invention Figure 1 ;

[0069] Figure 3 Schematic diagram of a power grid simulation calculation model provided by an embodiment of the present invention Figure 2 ;

[0070] Figure 4It is a structural schematic diagram of a power grid short-circuit ratio calculation device taking into account the influence of distributed photovoltaics provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0071] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0072] In order to illustrate the technical solution of the present invention, a specific embodiment is provided below for illustration.

[0073] Figure 1 is a schematic diagram of the implementation flow of the method for calculating the short-circuit ratio of a power grid taking into account the influence of distributed photovoltaic power generation provided in an embodiment of the present invention, see Figure 1 As shown, the method includes:

[0074] Step S101, obtaining grid parameters of the power grid, and building a distributed photovoltaic and load balanced distribution grid simulation calculation model based on the grid parameters.

[0075] In this embodiment, the grid parameters include but are not limited to equipment parameters of the grid, distributed photovoltaic output parameters, load parameters, etc.

[0076] First, a power grid simulation calculation model containing multiple nodes and multiple lines is built, and then the distributed photovoltaics and loads are evenly distributed to each photovoltaic feed-in node in the power grid simulation calculation model to obtain a power grid simulation calculation model with balanced distribution of distributed photovoltaics and loads; among which, the photovoltaic feed-in nodes are: all nodes except the nodes connected to the main grid.

[0077] Exemplary:

[0078] First, build a power grid model with n nodes and m lines, and set the n nodes as N1, N2, N3, ..., N n , where N1 is the node connected to the main network. The m lines are set as L1, L2, L3, ..., L m , the resistance on each line is R 1, R 2, R3,...R m , reactance is X1,X2,X3,...,X m , the capacitance is C1, C2, C3, ..., C m The node voltage of each node is U1, U2, U3, ..., U n .

[0079] Then, the distributed photovoltaic and load are evenly distributed to each node except N1. Assume that N2, N3, N4, ..., N n The distributed photovoltaics on the nodes are G2, G3, G4, ..., G n ; Assume that the total active power of distributed photovoltaic is P, the total reactive power is Q, and the active power of each distributed photovoltaic is P2, P3, P4, ..., P n ,and The reactive power of each distributed photovoltaic is Q2, Q3, Q4, ..., Q n ,and Set the load of each connection at each node to LD2, LD3, LD4, ..., LD n The active power of each load is P 2 ,P 3 ,P 4 ,...,P n , and P 2 =P 3 =P 4 =... =P n , the reactive power of each load is Q 2 ,Q 3 ,Q 4 ,...,Q n , and Q 2 =Q 3 =Q 4 =... =Q n The effective value of the voltage of the external power supply connected to the N1 node is E, and its short-circuit capacity is S.

[0080] Step S102, determining the power transfer coefficient of each photovoltaic feed-in node in the power grid simulation calculation model.

[0081] Here, the self-impedance matrix of each photovoltaic feed-in node and the mutual impedance matrix between each photovoltaic feed-in node and other photovoltaic feed-in nodes can be determined according to the grid structure of the power grid simulation calculation model; based on the self-impedance matrix of each photovoltaic feed-in node and the mutual impedance matrix between each photovoltaic feed-in node and other photovoltaic feed-in nodes, the power transfer coefficient of each photovoltaic feed-in node is determined.

[0082] Exemplary:

[0083] According to the grid structure of the power grid simulation calculation model, the self-impedance matrix Z of the photovoltaic feed-in node i is obtained. i,i , and its mutual impedance matrix Z with the photovoltaic feed-in node j i,j , the power transfer coefficient K of the photovoltaic feed-in node j can be obtained i,j ,in

[0084] Step S103, respectively setting the power grid simulation calculation model to different operation scenarios.

[0085] In this embodiment, the operation scenarios include: a forward power flow scenario, a reverse power flow scenario, and a local balance scenario. The power grid simulation calculation model can be placed in different operation scenarios by setting the coefficient λ of the distributed photovoltaic power generation power.

[0086] Exemplary:

[0087] In the scenario of positive power flow, the coefficient λ can be set so that the active power of distributed photovoltaic is λP2,λP3,λP4,...,λP n , and ensure that λP i <P i ,In this scenario, the distributed photovoltaic power generation power is less than the load power consumption, and the power is transmitted positively from the main grid to the power grid.

[0088] In the reverse power flow scenario, the coefficient λ can be set so that the active power of distributed photovoltaic is λP2,λP3,λP4,...,λP n , and ensure that λP i >P i ,In this scenario, the distributed photovoltaic power generation power is greater than the load power consumption, and the power is transmitted back from the power grid to the main grid.

[0089] In the local balancing scenario, the coefficient λ can be set so that the active power of distributed photovoltaic is λP2,λP3,λP4,...,λP n , and ensure that λP i =P i ,In this scenario, the distributed photovoltaic power generation power is equal to the load power consumption, and the power is balanced on site.

[0090] Step S104, in each operation scenario, calculating the short-circuit ratio related index of each photovoltaic feed-in node, and determining the short-circuit ratio of each photovoltaic feed-in node in the operation scenario according to the short-circuit ratio related index and the power transfer coefficient of each photovoltaic feed-in node.

[0091] (1) In the scenario of positive power flow, a three-phase short-circuit fault is set at each node in turn, and the short-circuit current to ground of each node is measured by simulation calculation in turn. Then calculate the short-circuit capacity S1, S2, S3, ..., S of each node n ,in U i is the rated voltage of the ith node.

[0092] Then, according to the short-circuit ratio related indicators and power transfer coefficient of each photovoltaic feed-in node, the short-circuit ratio of each photovoltaic feed-in node under this operation scenario is determined using the following formula:

[0093]

[0094] Among them, K SCRi is the short-circuit ratio of the i-th photovoltaic feed-in node; S i is the capacity of the ith photovoltaic feed-in node; P i is the photovoltaic feed-in power of the i-th photovoltaic feed-in node; P j is the photovoltaic feed-in power of the jth photovoltaic feed-in node; K i,j is the power transfer coefficient of the jth PV feed-in node.

[0095] (2) In the power flow reverse transmission scenario, a three-phase short-circuit fault is set at each node in turn, and the short-circuit current to ground of each node is measured by simulation calculation in turn. Then calculate the short-circuit capacity S1, S2, S3, ..., S of each node n ,in U i is the rated voltage of the ith node.

[0096] Then, according to the short-circuit ratio related indicators and power transfer coefficient of each photovoltaic feed-in node, the short-circuit ratio of each photovoltaic feed-in node under this operation scenario is determined using the following formula:

[0097]

[0098] Among them, K SCRi is the short-circuit ratio of the i-th photovoltaic feed-in node; S i is the capacity of the ith photovoltaic feed-in node; P i is the photovoltaic feed-in power of the i-th photovoltaic feed-in node; P j is the photovoltaic feed-in power of the jth photovoltaic feed-in node; K i,j is the power transfer coefficient of the jth PV feed-in node.

[0099] (3) In the local balancing scenario, a three-phase short-circuit fault is set at each node in turn, and the short-circuit current to ground of each node is simulated and calculated in turn. Then calculate the short-circuit capacity S1, S2, S3, ..., S of each node n ,in U i is the rated voltage of the ith node.

[0100] Then, according to the short-circuit ratio related indicators and power transfer coefficient of each photovoltaic feed-in node, the short-circuit ratio of each photovoltaic feed-in node under this operation scenario is determined using the following formula:

[0101]

[0102] Among them, K SCRi is the short-circuit ratio of the i-th photovoltaic feed-in node; S i is the capacity of the i-th photovoltaic feed-in node; P i is the photovoltaic feed-in power of the i-th photovoltaic feed-in node; P j is the photovoltaic feed-in power of the jth photovoltaic feed-in node; K i,j is the power transfer coefficient of the jth PV feed-in node.

[0103] Step S105 , determining the short-circuit ratio of the power grid based on the short-circuit ratio of each photovoltaic feed-in node in each operation scenario.

[0104] In this embodiment, the minimum short-circuit ratio of each photovoltaic feed-in node in each scenario can be determined first, that is,

[0105] Then, based on the minimum short-circuit ratio under each operating scenario, the short-circuit ratio of the power grid is determined by the geometric mean method, and the formula is: This approach can balance the impact of each scene to a certain extent.

[0106] The method for calculating the short-circuit ratio of a power grid containing distributed photovoltaics under multiple operating scenarios proposed in an embodiment of the present invention is to build a power grid simulation calculation model of distributed photovoltaics and load balanced distribution, determine the power transfer coefficient of each photovoltaic feed-in node in the power grid simulation calculation model, set the power grid simulation calculation model in different operating scenarios, calculate the short-circuit ratio related indicators of each photovoltaic feed-in node in each operating scenario, and determine the short-circuit ratio of each photovoltaic feed-in node in the operating scenario based on the short-circuit ratio related indicators and power transfer coefficient of each photovoltaic feed-in node, and finally determine the short-circuit ratio of the power grid based on the short-circuit ratio of each photovoltaic feed-in node in each operating scenario. The embodiment of the present invention comprehensively considers the short-circuit ratio of different operating scenarios in the power grid, thereby refining the calculation and analysis of the voltage stability of the power grid, solves the calculation deviation problem caused by the existing power grid short-circuit ratio calculation not considering the influence of distributed photovoltaics, and realizes the accurate calculation of the short-circuit ratio of the power grid containing distributed photovoltaics, which is of great significance for quantifying the short-circuit ratio of the active power grid and analyzing the static stability of the power grid voltage.

[0107] In order to facilitate understanding of the present solution, the method is explained below through two examples based on the above-mentioned method for calculating the short-circuit ratio of the power grid.

[0108] Example 1

[0109] Step 1: If Figure 2 , a power grid model with 5 nodes and 4 lines is built. The resistance, capacitance and reactance of each line are shown in Table 1:

[0110] Table 1 Power grid parameters

[0111] r_ohm_per_km x_ohm_per_km c_nf_per_km 0.2 0.2 0 0.1 0.1 0 0.2 0.2 0 0.1 0.1 0

[0112] The node voltage of each node is U1=U2=U3=U4=U5=10kV. The total active power of distributed photovoltaic is 40MW, the active power of each distributed photovoltaic is P2=P3=P4=P5=10MW, and the active power of each load is P 2 =P 3 =P 4 =P 5 = 15MW. The voltage effective value of the external power supply connected to the N1 node is 10kV, and its short-circuit capacity is 10MW.

[0113] Step 2: Calculate the impedance matrix of each node:

[0114]

[0115] The element in the i-th row and j-th column of the matrix is ​​Z i,j , such as Z 1,1 =1.142+0.284j. According to Z i,j The size of Calculate the power transfer coefficient K i,j , as shown in Table 2:

[0116] Table 2 Power transfer coefficient calculation results

[0117] <![CDATA[K 1,2 ]]> 0.803 <![CDATA[K 3,4 ]]> 0.888 <![CDATA[K 1,3 ]]> 0.737 <![CDATA[K 3,5 ]]> 0.862 <![CDATA[K 1,4 ]]> 0.655 <![CDATA[K 4,1 ]]> 0.863 <![CDATA[K 1,5 ]]> 0.636 <![CDATA[K 4,2 ]]> 0.863 <![CDATA[K 2,1 ]]> 1 <![CDATA[K 4，3 ]]> 0.888 <![CDATA[K 2,3 ]]> 0.917 <![CDATA[K 4，5 ]]> 0.969 <![CDATA[K 2,4 ]]> 0.816 <![CDATA[K 5,1 ]]> 0.792 <![CDATA[K 2,5 ]]> 0.792 <![CDATA[K 5,2 ]]> 0.792 <![CDATA[K 3,1 ]]> 0.971 <![CDATA[K 5,3 ]]> 0.815 <![CDATA[K 3,2 ]]> 0.971 <![CDATA[K 5,4 ]]> 0.916

[0118] Step 3: Set the coefficient λ = 1 in the forward transmission scenario, and the active power λP of the distributed photovoltaic i =10MW, active power of load P i =15MW, the short-circuit current and short-circuit capacity of the photovoltaic feed-in node are calculated, as shown in Table 3:

[0119] Table 3 Calculation results of short-circuit capacity under forward transmission scenario

[0120] Short circuit current Short circuit capacity <![CDATA[N2]]> 1.796kA 31.113MW <![CDATA[N3]]> 5.123kA 88.732MW <![CDATA[N4]]> 9.680kA 167.662MW <![CDATA[N5]]> 15.366kA 266.146MW

[0121] The short circuit ratio is calculated as shown in Table 4:

[0122] Table 4 Calculation results of short circuit ratio under positive transmission scenario

[0123]

[0124] Step 4: Set the coefficient λ = 2 in the reverse transmission scenario, and the active power λP of the distributed photovoltaic i =20MW, load active power P i =15MW, the short-circuit current and short-circuit capacity of the photovoltaic feed-in node are calculated, as shown in Table 5:

[0125] Table 5 Calculation results of short-circuit capacity under reverse transmission scenario

[0126] Short circuit current Short circuit capacity <![CDATA[N2]]> 1.553kA 26.898MW <![CDATA[N3]]> 5.312kA 92.006MW <![CDATA[N4]]> 10.980kA 190.179MW <![CDATA[N5]]> 17.887kA 309.811MW

[0127] The calculated short circuit ratio is shown in Table 6:

[0128] Table 6 Calculation results of short circuit ratio in reverse transmission scenario

[0129]

[0130] Step 5: Set the coefficient λ = 1.5 in the local balancing scenario, and the active power λP of the distributed photovoltaic i =15MW, active power of load P i =15MW, the short-circuit current and short-circuit capacity of the photovoltaic feed-in node are calculated, as shown in Table 7:

[0131] Table 7 Calculation results of short-circuit capacity under local balancing scenario

[0132]

[0133]

[0134] The calculated short circuit ratio is shown in Table 8:

[0135] Table 8 Calculation results of short circuit ratio in local balancing scenario

[0136]

[0137] Step 6: According to Calculate K 1 =6.106,K 2 =3.623,K 3 =4.481; according to The equivalent short-circuit ratio K of the entire power grid is calculated. SCR =4.628.

[0138] Example 2

[0139] Step 1: Figure 3 , a power grid model with 4 nodes and 3 lines is built. The resistance, capacitance and reactance of each line are shown in Table 9:

[0140] Table 9 Power grid parameters

[0141] r_ohm_per_km x_ohm_per_km c_nf_per_km 0.2 0.2 0 0.1 0.1 0 0.2 0.2 0 0.1 0.1 0

[0142] The node voltage of each node is U1=U2=U3=U4=10kV. The total active power of distributed photovoltaic is 30MW, the active power of each distributed photovoltaic is P2=P3=P4=10MW, and the active power of each load is P 2 =P 3 =P 4 = 15MW. The voltage effective value of the external power supply connected to the N1 node is 10kV, and its short-circuit capacity is 10MW.

[0143] Step 2: Calculate the node impedance matrix in the example as follows:

[0144]

[0145] The element in the i-th row and j-th column of the matrix is ​​Z i,j , such as Z 1,1 =1.467+0.207j. According to Z i,j The size of Calculate the power transfer coefficient K i,j , as shown in Table 10:

[0146] Table 10 Power transfer coefficient calculation results

[0147] <![CDATA[K 1,2 ]]> 0.855 <![CDATA[K 3,1 ]]> 0.948 <![CDATA[K 1,3 ]]> 0.833 <![CDATA[K 3,2 ]]> 0.948 <![CDATA[K 1,4 ]]> 0.810 <![CDATA[K 3,4 ]]> 0.899 <![CDATA[K 2，1 ]]> 1 <![CDATA[K 4,1 ]]> 0.900 <![CDATA[K 2,3 ]]> 0.974 <![CDATA[K 4，2 ]]> 0.900 <![CDATA[K 2,4 ]]> 0.948 <![CDATA[K 4，3 ]]> 0.877

[0148] Step 3: Set the coefficient λ = 1 in the forward transmission scenario, and the active power λP of the distributed photovoltaic i =10MW, active power of load P i =15MW, the short-circuit current and short-circuit capacity of the photovoltaic feed-in node are calculated, as shown in Table 11:

[0149] Table 11 Calculation results of short-circuit capacity under forward transmission scenario

[0150] Short circuit current Short circuit capacity <![CDATA[N2]]> 2.420kA 41.915MW <![CDATA[N3]]> 5.243kA 90.811MW <![CDATA[N4]]> 12.698kA 219.935MW

[0151] The calculated short circuit ratio is shown in Table 12:

[0152] Table 12 Calculation results of short circuit ratio in positive transmission scenario

[0153]

[0154]

[0155] Step 4: Set the coefficient λ = 2 in the reverse transmission scenario, and the active power λP of the distributed photovoltaic i=20MW, active power of load P i =15MW, the short-circuit current and short-circuit capacity of the photovoltaic feed-in node are calculated, as shown in Table 13:

[0156] Table 13 Calculation results of short-circuit capacity under reverse transmission scenario

[0157] Short circuit current Short circuit capacity <![CDATA[N2]]> 2.055kA 35.293MW <![CDATA[N3]]> 6.028kA 104.408MW <![CDATA[N4]]> 13.778kA 238.641MW

[0158] The calculated short circuit ratio is shown in Table 14:

[0159] Table 14 Calculation results of short circuit ratio in reverse transmission scenario

[0160]

[0161] Step 5: Set the coefficient λ = 1.5 in the local balancing scenario, and the active power λP of the distributed photovoltaic i =15MW, active power of load P i =15MW, the short-circuit current and short-circuit capacity of the photovoltaic feed-in node are calculated, as shown in Table 15:

[0162] Table 15 Short-circuit capacity calculation results under local balancing scenario

[0163] Short circuit current Short circuit capacity <![CDATA[N2]]> 2.163kA 37.464MW <![CDATA[N3]]> 5.675kA 98.293MW <![CDATA[N4]]> 13.233kA 229.202MW

[0164] The calculated short circuit ratio is shown in Table 16:

[0165] Table 16 Calculation results of short circuit ratio in local balancing scenario

[0166]

[0167] Step 6: According to Calculate K 1 =6.957,K 2 =3.839,K 3 =4.881; according to The equivalent short-circuit ratio K of the entire power grid is calculated. SCR =5.070.

[0168] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean 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 embodiment of the present invention.

[0169] Figure 4 : is a schematic diagram of the structure of a power grid short-circuit ratio calculation device 40 taking into account the influence of distributed photovoltaic power generation provided in an embodiment of the present invention, the device comprising:

[0170] A module 41 is established to obtain grid parameters of the grid and to build a grid simulation calculation model of distributed photovoltaic and load balanced distribution according to the grid parameters.

[0171] The determination module 42 is used to determine the power transfer coefficient of each photovoltaic feed-in node in the power grid simulation calculation model.

[0172] The setting module 43 is used to respectively set the power grid simulation calculation model to different operation scenarios.

[0173] The calculation module 44 is used to calculate the short-circuit ratio related indicators of each photovoltaic feed-in node in each operation scenario, and determine the short-circuit ratio of each photovoltaic feed-in node in the operation scenario according to the short-circuit ratio related indicators and the power transfer coefficient of each photovoltaic feed-in node; based on the short-circuit ratio of each photovoltaic feed-in node in each operation scenario, determine the short-circuit ratio of the power grid.

[0174] In one possible implementation, the grid parameters include: distributed photovoltaic and load;

[0175] The establishment module 41 is specifically used for:

[0176] Build a power grid simulation model containing multiple nodes and multiple lines;

[0177] The distributed photovoltaics and loads are evenly distributed to each photovoltaic feed-in node in the power grid simulation calculation model to obtain a power grid simulation calculation model with balanced distribution of distributed photovoltaics and loads; wherein the photovoltaic feed-in nodes are: all nodes except the nodes connected to the main grid.

[0178] In a possible implementation manner, the determination module 42 is specifically configured to:

[0179] According to the grid structure of the power grid simulation calculation model, the self-impedance matrix of each photovoltaic feed-in node and the mutual impedance matrix between each photovoltaic feed-in node and other photovoltaic feed-in nodes are determined;

[0180] Based on the self-impedance matrix of each photovoltaic feeding node and the mutual impedance matrix between each photovoltaic feeding node and other photovoltaic feeding nodes, the power transfer coefficient of each photovoltaic feeding node is determined.

[0181] As a possible implementation method, the operation scenarios include: forward flow scenario, reverse flow scenario and local balance scenario;

[0182] The setting module 43 is specifically used for:

[0183] By setting the coefficient of distributed photovoltaic power generation, the distributed photovoltaic power generation power is made smaller than the load power consumption. At this time, the power grid simulation calculation model is in the positive power flow scenario.

[0184] By setting the coefficient of distributed photovoltaic power generation, the distributed photovoltaic power generation power is greater than the load power consumption. At this time, the power grid simulation calculation model is in the power flow reverse transmission scenario;

[0185] By setting the coefficient of distributed photovoltaic power generation, the distributed photovoltaic power generation power is equal to the load power consumption. At this time, the power grid simulation calculation model is in a local balance scenario.

[0186] In a possible implementation, the calculation module 44 is specifically used for:

[0187] In each operation scenario, a three-phase short-circuit fault is set on each photovoltaic feed-in node in turn, and the short-circuit ratio related indicators of each photovoltaic feed-in node are simulated and calculated;

[0188] Among them, short-circuit ratio related indicators include: short-circuit current and short-circuit capacity.

[0189] In a possible implementation, the calculation module 44 is specifically used for:

[0190] according to Determine the short-circuit ratio of each photovoltaic feed-in node under the operating scenario;

[0191] Among them, K SCRi is the short-circuit ratio of the i-th photovoltaic feed-in node; S i is the capacity of the i-th photovoltaic feed-in node; P i is the photovoltaic feed-in power of the i-th photovoltaic feed-in node; P j is the photovoltaic feed-in power of the jth photovoltaic feed-in node; K i,j is the power transfer coefficient of the jth PV feed-in node.

[0192] In a possible implementation, the calculation module 44 is specifically used for:

[0193] Determine the minimum short-circuit ratio of each PV feed-in node in each scenario;

[0194] Based on the minimum short-circuit ratio under various operating scenarios, the short-circuit ratio of the power grid is determined by the geometric mean method.

[0195] In a possible implementation manner, the determination module 42 is specifically configured to:

[0196] based on Determine the power transfer coefficient of each photovoltaic feed-in node;

[0197] Among them, K i,j is the power transfer coefficient of photovoltaic feed-in node j; Z i,i is the self-impedance matrix of photovoltaic feed-in node i; Z i,j is the mutual impedance matrix between photovoltaic feeding node i and photovoltaic feeding node j.

[0198] The method for calculating the short-circuit ratio of a power grid containing distributed photovoltaics under multiple operating scenarios proposed in an embodiment of the present invention is to build a power grid simulation calculation model of distributed photovoltaics and load balanced distribution, determine the power transfer coefficient of each photovoltaic feed-in node in the power grid simulation calculation model, set the power grid simulation calculation model in different operating scenarios, calculate the short-circuit ratio related indicators of each photovoltaic feed-in node in each operating scenario, and determine the short-circuit ratio of each photovoltaic feed-in node in the operating scenario based on the short-circuit ratio related indicators and power transfer coefficient of each photovoltaic feed-in node, and finally determine the short-circuit ratio of the power grid based on the short-circuit ratio of each photovoltaic feed-in node in each operating scenario. The embodiment of the present invention comprehensively considers the short-circuit ratio of different operating scenarios in the power grid, thereby refining the calculation and analysis of the voltage stability of the power grid, solves the calculation deviation problem caused by the existing power grid short-circuit ratio calculation not considering the influence of distributed photovoltaics, and realizes the accurate calculation of the short-circuit ratio of the power grid containing distributed photovoltaics, which is of great significance for quantifying the short-circuit ratio of the active power grid and analyzing the static stability of the power grid voltage.

[0199] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0200] Those of ordinary skill in the art will appreciate that the templates, units, and algorithm steps of each example 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 performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0201] If the module / unit is implemented in the form of 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, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned various power grid short-circuit ratio calculation method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0202] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A method for calculating the short-circuit ratio of a power grid taking into account the influence of distributed photovoltaics, characterized in that: include: Obtaining grid parameters of the power grid, and building a distributed photovoltaic and load balanced distribution grid simulation calculation model based on the grid parameters; Determining the power transfer coefficient of each photovoltaic feed-in node in the power grid simulation calculation model; The power grid simulation calculation model is respectively set in different operation scenarios; Under each operation scenario, the short-circuit ratio related index of each photovoltaic feed-in node is calculated, and the short-circuit ratio of each photovoltaic feed-in node under the operation scenario is determined according to the short-circuit ratio related index and the power transfer coefficient of each photovoltaic feed-in node; The short-circuit ratio of the power grid is determined based on the short-circuit ratio of each photovoltaic feed-in node under each operation scenario.

2. The method for calculating the short-circuit ratio of a power grid taking into account the influence of distributed photovoltaics as claimed in claim 1, characterized in that: The grid parameters include: distributed photovoltaic and load; The method of building a distributed photovoltaic and load balanced distribution grid simulation calculation model according to the grid parameters includes: Build a power grid simulation model containing multiple nodes and multiple lines; The distributed photovoltaic and the load are evenly distributed to each photovoltaic feed-in node in the power grid simulation calculation model to obtain a power grid simulation calculation model with balanced distribution of distributed photovoltaic and load; wherein the photovoltaic feed-in nodes are: all nodes except the nodes connected to the main grid.

3. The method for calculating the short-circuit ratio of a power grid taking into account the influence of distributed photovoltaics as claimed in claim 1, characterized in that: The determining of the power transfer coefficient of each photovoltaic feed-in node in the power grid simulation calculation model includes: Determining the self-impedance matrix of each photovoltaic feed-in node and the mutual impedance matrix between each photovoltaic feed-in node and other photovoltaic feed-in nodes according to the grid structure of the power grid simulation calculation model; Based on the self-impedance matrix of each photovoltaic feeding node and the mutual impedance matrix between each photovoltaic feeding node and other photovoltaic feeding nodes, the power transfer coefficient of each photovoltaic feeding node is determined.

4. The method for calculating the short-circuit ratio of a power grid taking into account the influence of distributed photovoltaics as claimed in claim 1, characterized in that: The operation scenarios include: forward flow scenario, reverse flow scenario and local balance scenario; The respectively setting the power grid simulation calculation model to different operation scenarios includes: By setting the coefficient of distributed photovoltaic power generation, the distributed photovoltaic power generation power is made smaller than the load power consumption, and at this time, the power grid simulation calculation model is in the positive power flow scenario; By setting the coefficient of distributed photovoltaic power generation, the distributed photovoltaic power generation power is made greater than the load power consumption, and at this time, the power grid simulation calculation model is in the power flow reverse transmission scenario; By setting the coefficient of the distributed photovoltaic power generation power, the distributed photovoltaic power generation power is equal to the load power consumption. At this time, the power grid simulation calculation model is in the local balance scenario.

5. The method for calculating the short-circuit ratio of a power grid taking into account the influence of distributed photovoltaics as claimed in claim 1, characterized in that: In each operation scenario, the short-circuit ratio related indicators of each photovoltaic feed-in node are calculated, including: In each operation scenario, a three-phase short-circuit fault is set on each photovoltaic feed-in node in turn, and the short-circuit ratio related indicators of each photovoltaic feed-in node are simulated and calculated; Among them, the short-circuit ratio related indicators include: short-circuit current and short-circuit capacity.

6. The method for calculating the short-circuit ratio of a power grid taking into account the influence of distributed photovoltaics as claimed in claim 5, characterized in that: Determining the short-circuit ratio of each photovoltaic feed-in node in the operation scenario according to the short-circuit ratio-related index and the power transfer coefficient of each photovoltaic feed-in node includes: according to Determine the short-circuit ratio of each photovoltaic feed-in node under the operating scenario; Among them, K SCRi is the short-circuit ratio of the i-th photovoltaic feed-in node; S i is the capacity of the i-th photovoltaic feed-in node; P i is the photovoltaic feed-in power of the i-th photovoltaic feed-in node; P j is the photovoltaic feed-in power of the jth photovoltaic feed-in node; K i,j is the power transfer coefficient of the jth PV feed-in node.

7. The method for calculating the short-circuit ratio of a power grid taking into account the influence of distributed photovoltaics according to claim 1, characterized in that: The determining the short-circuit ratio of the power grid based on the short-circuit ratio of each photovoltaic feed-in node in each operation scenario includes: Determine the minimum short-circuit ratio of each PV feed-in node in each scenario; Based on the minimum short-circuit ratio under various operating scenarios, the short-circuit ratio of the power grid is determined by the geometric mean method.

8. The method for calculating the short-circuit ratio of a power grid taking into account the influence of distributed photovoltaic power generation according to claim 3, characterized in that: The determining of the power transfer coefficient of each photovoltaic feed-in node based on the self-impedance matrix of each photovoltaic feed-in node and the mutual impedance matrix between each photovoltaic feed-in node and other photovoltaic feed-in nodes includes: based on Determine the power transfer coefficient of each photovoltaic feed-in node; Among them, K i,j is the power transfer coefficient of photovoltaic feed-in node j; Z i,i is the self-impedance matrix of photovoltaic feed-in node i; Z i,j is the mutual impedance matrix between photovoltaic feeding node i and photovoltaic feeding node j.

9. A power grid short-circuit ratio calculation device taking into account the influence of distributed photovoltaics, characterized in that: include: Establish a module for obtaining grid parameters of the grid, and build a grid simulation calculation model for distributed photovoltaic and load balanced distribution according to the grid parameters; A determination module, used to determine the power transfer coefficient of each photovoltaic feed-in node in the power grid simulation calculation model; A setting module, used to respectively set the power grid simulation calculation model to different operation scenarios; The calculation module is used to calculate the short-circuit ratio related indicators of each photovoltaic feed-in node in each operation scenario, and determine the short-circuit ratio of each photovoltaic feed-in node in the operation scenario according to the short-circuit ratio related indicators and the power transfer coefficient of each photovoltaic feed-in node; based on the short-circuit ratio of each photovoltaic feed-in node in each operation scenario, determine the short-circuit ratio of the power grid.

10. The power grid short-circuit ratio calculation device taking into account the influence of distributed photovoltaics as claimed in claim 9, characterized in that: The operation scenarios include: forward flow scenario, reverse flow scenario and local balance scenario; The setting module is specifically used for: By setting the coefficient of distributed photovoltaic power generation, the distributed photovoltaic power generation power is made smaller than the load power consumption, and at this time, the power grid simulation calculation model is in the positive power flow scenario; By setting the coefficient of distributed photovoltaic power generation, the distributed photovoltaic power generation power is made greater than the load power consumption, and at this time, the power grid simulation calculation model is in the power flow reverse transmission scenario; By setting the coefficient of the distributed photovoltaic power generation power, the distributed photovoltaic power generation power is equal to the load power consumption. At this time, the power grid simulation calculation model is in the local balance scenario.

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