Receiving end power grid reactive power compensation equipment optimal configuration method and system considering power flow transfer

Abstract

The invention discloses a receiving end power grid reactive power compensation equipment optimal configuration method considering power flow transfer. The method comprises the following steps: when high-voltage direct current or new energy power in a receiving-end power grid changes, calculating a power flow transfer factor of the receiving-end power grid; calculating a voltage weak node comprehensive evaluation index based on the power flow transfer factor of the receiving end power grid, and determining a voltage stability weak node set based on the comprehensive evaluation index; for the voltage stability weak node set, partitioning nodes in the voltage stability weak node set by calculating an electrical distance index, and respectively determining an alternative installation node set of the reactive compensation equipment for each node partition; through simulation, the sensitivity of weak node voltage to alternative nodes of the reactive power compensation device is calculated, and the installation place and capacity of the reactive power compensation device are determined based on the optimal particle swarm optimization.

Description

Technical Field

[0001] The present application relates to the technical field of receiving-end power grids, and more specifically, to a method and system for optimizing configuration of reactive power compensation equipment of a receiving-end power grid taking power flow transfer into consideration. Background Art

[0002] The UHV DC system has the characteristics of large capacity, controllability and flexibility, and has been widely used in regional power grid interconnection, long-distance large-capacity power transmission and cross-strait power transmission. However, due to the large power of UHV DC transmission, when it is locked or reduced in power due to a fault, a large-scale power flow transfer will occur in the receiving power grid, which may cause voltage instability in some important AC transmission channels. In addition, with the large-scale access of new energy to the receiving power grid, when the output of new energy fluctuates randomly, it will also trigger power flow transfer within the power grid, leading to voltage instability. In view of the above problems, it is urgent to study the optimal configuration scheme of the reactive compensation device of the receiving power grid to provide reactive voltage support for the power grid and ensure the safe and stable operation of the receiving power grid. Summary of the invention

[0003] Based on the above problems, this application provides a method and system for optimizing the configuration of reactive compensation equipment in the receiving-end power grid considering power flow transfer, in order to solve the problem that due to the large power of ultra-high voltage direct current transmission, when it is locked or reduced in power due to a fault, a large-scale power flow transfer will occur in the receiving-end power grid, which may cause voltage instability in some important AC transmission channels. In addition, with the large-scale access of new energy to the receiving-end power grid, when the output of new energy fluctuates randomly, it will also trigger power flow transfer within the power grid, thereby causing technical problems such as voltage instability.

[0004] According to a first aspect of the present application, a method for optimizing configuration of reactive power compensation equipment in a receiving-end power grid considering power flow transfer is provided, comprising:

[0005] When the high voltage DC or new energy power in the receiving grid changes, calculate the power flow transfer factor of the receiving grid;

[0006] Based on the power flow transfer factor of the receiving-end power grid, a comprehensive evaluation index of voltage weak nodes is calculated, and a voltage stability weak node set is determined based on the comprehensive evaluation index;

[0007] For the weak voltage stability node set, the nodes in the weak voltage stability node set are partitioned by calculating the electrical distance index, and the candidate installation node set of reactive power compensation equipment is determined for each node partition;

[0008] Through simulation, the sensitivity of weak node voltage to the alternative nodes of reactive compensation device is calculated, and the installation location and capacity of reactive compensation device are determined based on the optimal particle swarm algorithm.

[0009] Optionally, when the high voltage direct current or renewable energy power in the receiving-end power grid changes, the power flow transfer factor of the receiving-end power grid is calculated, including:

[0010] For the receiving grid fed by UHV DC, the UHV DC is equivalent to a power source at the feeding point. When the power of the high-voltage DC or renewable energy in the receiving grid changes, assuming that the DC feeding point or renewable energy grid connection point is node i, when the active injection power of node i changes ΔP i When the active power change on the internal branch k of the receiving power grid is Then there is a relationship:

[0011]

[0012] In the formula, G k-i It is the power transfer factor of line k to node i;

[0013] Based on the relationship, G k-i The expression is derived, and according to the rapid decomposition method flow calculation formula, we have:

[0014]

[0015] Among them, ΔP is the column vector of node injection power change, Δθ is the column vector of voltage phase angle change, B0 is the susceptance matrix established with 1 / x as the branch parameter, and X is the inverse matrix of B0;

[0016] According to formula (2), after the active power injection of node i changes, the power change caused on branch k, assuming that the node numbers at both ends are m and n respectively, is

[0017]

[0018] The power flow transfer factor G of the receiving power grid k-i The expression is

[0019]

[0020] Optionally, based on the power flow transfer factor of the receiving-end power grid, calculating a comprehensive evaluation index of voltage weak nodes, and determining a voltage stability weak node set based on the comprehensive evaluation index, comprises:

[0021] For the expected fault of the receiving power grid, based on the power flow transfer factor of the receiving power grid, the power flow change of each line in the key section is calculated, and the line load rate index is obtained according to formula (5):

[0022]

[0023] Among them, λ k is the load rate index of line k after the fault, P k and Pk.N are the steady-state power and rated power of line k after the fault respectively;

[0024] Taking into account the sensitivity of node voltage to the reactive power output of dynamic compensation equipment and the reactive power output capacity of compensation equipment, the dynamic reactive power compensation capacity index γ of the receiving node of line k is formulated. k :

[0025]

[0026] Among them, ΔQ k is the reactive power change of the dynamic reactive power compensation device at the receiving end node of line k, ΔU k is the voltage change of the corresponding line k receiving node, Q k.max The reactive power output upper limit of the dynamic reactive power compensation device connected to the receiving node of line k;

[0027] Based on the line load rate index and dynamic reactive power compensation capability index, the voltage weak node comprehensive evaluation index L is calculated. k :

[0028] L k =λ k -αγ k (7)

[0029] Among them, α is the adjustment coefficient, which can be determined according to the actual situation of the power grid;

[0030] Set the comprehensive evaluation index L of the voltage weak node k The threshold value is L k.max , if L k >L k.max , then the receiving node of line k is judged to be a weak node, and the voltage stability weak node set R = {i, j, …} is determined by calculating the comprehensive evaluation index of weak nodes for all lines in the key section.

[0031] Optionally, for the voltage stability weak node set, the nodes in the voltage stability weak node set are partitioned by calculating the electrical distance index, and a candidate installation node set of the reactive power compensation device is determined for each node partition, including:

[0032] The electrical distance between any two different nodes in the power grid is defined by the node impedance matrix:

[0033]

[0034] Let vector I k and I i Take 1 and -1 respectively, and the rest take 0, which is equivalent to injecting positive and negative unit currents into nodes k and i in the power grid respectively. From formula (8), we can get U kand U i , then the electrical distance D between nodes k and i k.i Expressed as

[0035] D k.i =|U k -U i |=|Z kk +Z ii -2Z ki | (9)

[0036] Define the maximum electrical distance index D max , for all nodes in the set R, the electrical distance is calculated pairwise by equation (9). For any node k and i, if D k.i ≤D max , then nodes k and i are classified as the same region, and the set R is divided into z subsets according to the region, denoted as R1, ..., R z ;

[0037] For each node partition, the candidate installation node set of reactive compensation equipment is determined respectively, and an average electrical distance calculation index D is defined, which is the average distance from node k to all nodes in the weak node set R1. Expressed as

[0038]

[0039] Among them, N R1 is the number of weak nodes in R1;

[0040] For each receiving grid node, calculate the average electrical distance between it and the nodes in R1. Select several nodes with the smallest average electrical distance as candidate nodes for reactive power compensation devices in node partition R1;

[0041] Repeat the above steps until the candidate nodes of the reactive power compensation device in each node partition are obtained.

[0042] Optionally, the sensitivity of the weak node voltage to the candidate node of the reactive power compensation device is calculated through simulation, and the installation location and capacity of the reactive power compensation device are determined based on the optimal particle swarm algorithm, including:

[0043] Reactive power compensation devices are set at the candidate installation nodes j, and their rated capacity is S N.j Through time domain simulation, the voltage support effect of reactive power compensation devices at different locations on the voltage weak node i after the fault is analyzed. By establishing the sensitivity index μ ij , determine the effect of different types of reactive compensation devices on node voltage support:

[0044]

[0045] Among them, ΔUi is the post-fault steady-state voltage change of node i after the reactive compensation device is installed;

[0046] The objective function of the optimal particle swarm algorithm is determined based on the penalty function of equipment cost and different node voltages exceeding the constraint conditions:

[0047] minf=∑C k +p(U) (12)

[0048] Among them, ∑C k is the total equipment cost of the reactive power compensation device in the configuration scheme, p(U) is the penalty function caused by the voltage exceeding the limit at each node;

[0049] The constraint condition for determining the optimal particle swarm algorithm is that the steady-state voltage of each voltage-weak node under a typical fault set can be restored to the allowable range:

[0050] U i.min ≤U i ≤U i.max (13)

[0051] The optimal particle swarm algorithm is used to solve the reactive power configuration scheme, where each particle represents a reactive power compensation device configuration scheme, and the function expressions of different particles and their speeds are:

[0052]

[0053] Among them, α i.j is the reactive power compensation capacity at the alternative node j in scheme i, v i.j is α i.j The speed of change;

[0054] The global optimal particle is obtained through iterative calculation of the optimal particle swarm, which is used as the optimal configuration location and capacity of the reactive power compensation device of the receiving-end power grid.

[0055] According to another aspect of the present application, a system for optimizing configuration of reactive power compensation equipment of a receiving-end power grid considering power flow transfer is also provided, comprising:

[0056] A power flow transfer factor calculation module is used to calculate the power flow transfer factor of the receiving power grid when the high voltage direct current or new energy power in the receiving power grid changes;

[0057] A module for determining a set of weak voltage stability nodes, used to calculate a comprehensive evaluation index of weak voltage nodes based on a power flow transfer factor of the receiving-end power grid, and determine a set of weak voltage stability nodes based on the comprehensive evaluation index;

[0058] A module for determining candidate installation node sets is used to partition the nodes in the voltage stability weak node set by calculating the electrical distance index, and determine the candidate installation node set of reactive power compensation equipment for each node partition;

[0059] The module for determining the installation location and capacity is used to calculate the sensitivity of the weak node voltage to the candidate nodes of the reactive compensation device through simulation, and determine the installation location and capacity of the reactive compensation device based on the optimal particle swarm algorithm.

[0060] Optionally, a module for calculating a power flow transfer factor includes:

[0061] The power flow transfer factor calculation submodule is used for the receiving grid of UHV DC feed-in. The UHV DC is equivalent to the power supply at the feed-in point. When the power of the high-voltage DC or new energy in the receiving grid changes, the DC feed-in point or the new energy grid connection point is assumed to be node i. When the active injection power of node i changes ΔP i When the active power change on the internal branch k of the receiving power grid is Then there is a relationship:

[0062]

[0063] In the formula, G k-i It is the power transfer factor of line k to node i;

[0064] Based on the relationship, G k-i The expression is derived, and according to the rapid decomposition method flow calculation formula, we have:

[0065]

[0066] Among them, ΔP is the column vector of node injection power change, Δθ is the column vector of voltage phase angle change, B0 is the susceptance matrix established with 1 / x as the branch parameter, and X is the inverse matrix of B0;

[0067] According to formula (2), after the active power injection of node i changes, the power change caused on branch k, assuming that the node numbers at both ends are m and n respectively, is

[0068]

[0069] The power flow transfer factor G of the receiving power grid k-i The expression is

[0070]

[0071] Optionally, the module for determining a voltage stability weak node set includes:

[0072] The line load rate index submodule is used to calculate the power flow change of each line in the key section based on the power flow transfer factor of the receiving power grid for the expected fault of the receiving power grid, and obtain the line load rate index according to formula (5):

[0073]

[0074] Among them, λ k is the load rate index of line k after the fault, P k and P k.N are the steady-state power and rated power of line k after the fault respectively;

[0075] Formulate a dynamic reactive power compensation capability index submodule, which is used to comprehensively consider the sensitivity of node voltage to the reactive power output of dynamic compensation equipment and the reactive power output capacity of compensation equipment, and formulate the dynamic reactive power compensation capability index γ of the receiving node of line k k :

[0076]

[0077] Among them, ΔQ k is the reactive power change of the dynamic reactive power compensation device at the receiving end node of line k, ΔU k is the voltage change of the corresponding line k receiving node, Q k.max The reactive power output upper limit of the dynamic reactive power compensation device connected to the receiving node of line k;

[0078] The submodule for calculating the comprehensive evaluation index of the weak voltage node is used to calculate the comprehensive evaluation index L of the weak voltage node based on the line load rate index and the dynamic reactive power compensation capability index. k :

[0079] L k =λ k -αγ k (7)

[0080] Among them, α is the adjustment coefficient, which can be determined according to the actual situation of the power grid;

[0081] Determine the voltage stability weak node set submodule, which is used to set the voltage weak node comprehensive evaluation index L k The threshold value is L k.max , if L k >L k.max , then the receiving node of line k is judged to be a weak node, and the voltage stability weak node set R = {i, j, …} is determined by calculating the comprehensive evaluation index of weak nodes for all lines in the key section.

[0082] Optionally, determine the node-set modules that can be installed, including:

[0083] The electrical distance determination submodule is used to define the electrical distance between any two different nodes in the power grid, which is defined by the node impedance matrix.

[0084]

[0085] Let vector I k and I i Take 1 and -1 respectively, and the rest take 0, which is equivalent to injecting positive and negative unit currents into nodes k and i in the power grid respectively. From formula (8), we can get U k and U i , then the electrical distance D between nodes k and i k.i Expressed as

[0086] D k.i =|U k -U i |=|Z kk +Z ii -2Z ki | (9)

[0087] Divide the voltage stability weak node set into submodules to define the maximum electrical distance index D max , for all nodes in the voltage stability weak node set R, the electrical distance is calculated pairwise by equation (9). For any node k and i, if D k.i ≤D max , then nodes k and i are classified into the same region, and the voltage stability weak node set R is divided into z subsets according to the region, denoted as R1,…,R z ;

[0088] The node average distance determination submodule is used to determine the candidate installation node set of reactive compensation equipment for each node partition, and define an average electrical distance calculation index D, the average distance from node k to all nodes in the weak node set R1 Expressed as

[0089]

[0090] Among them, N R1 is the number of weak nodes in R1;

[0091] The submodule for determining candidate nodes of reactive compensation device is used to calculate the average electrical distance D between each node of receiving grid and the node in R1 one by one. k 1 , select several nodes with the smallest average electrical distance as candidate nodes for reactive power compensation devices in node partition R1;

[0092] Repeat the above steps until the candidate nodes of the reactive power compensation device in each node partition are obtained.

[0093] Optionally, determining the installation location and capacity module includes:

[0094] A sensitivity index submodule is established to set reactive power compensation devices at candidate installation nodes j, with a rated capacity of S N.j Through time domain simulation, the voltage support effect of reactive power compensation devices at different locations on the voltage weak node i after the fault is analyzed. By establishing the sensitivity index μ ij , determine the effect of different types of reactive compensation devices on node voltage support:

[0095]

[0096] Among them, ΔU i is the post-fault steady-state voltage change of node i after the reactive compensation device is installed;

[0097] The objective function determination submodule is used to determine the objective function of the optimal particle swarm algorithm based on the equipment cost and the penalty function of different node voltages exceeding the constraint conditions:

[0098] minf=∑C k +p(U) (12)

[0099] Among them, ∑C k is the total equipment cost of the reactive power compensation device in the configuration scheme, p(U) is the penalty function caused by the voltage exceeding the limit at each node;

[0100] The constraint determination submodule is used to determine the constraint of the optimal particle swarm algorithm, which is that the steady-state voltage of each voltage-weak node under the typical fault set can be restored to the allowable range:

[0101] U i.min ≤U i ≤U i.max (13)

[0102] Determine different particles and their speed submodules, which are used to solve the reactive configuration scheme using the optimal particle swarm algorithm, where each particle represents a reactive compensation device configuration scheme, and the function expressions of different particles and their speeds are:

[0103]

[0104] Among them, α i.j is the reactive power compensation capacity at the alternative node j in scheme i, v i.j is α i.j The speed of change;

[0105] The optimal configuration location and capacity submodule is used to determine the optimal configuration location and capacity of the reactive power compensation device of the receiving-end power grid, and obtain the global optimal particle through iterative calculation of the optimal particle swarm.

[0106] According to another aspect of the present application, a computer-readable storage medium is provided, on which a computer program is stored, and when the program is executed by a processor, the steps of any of the methods described above are implemented.

[0107] According to another aspect of the present application, an electronic device is provided, including: a computer-readable storage medium; and one or more processors for executing a program in the computer-readable storage medium.

[0108] Therefore, the present application proposes a method for optimizing the configuration of reactive compensation equipment in a receiving-end power grid that takes into account power flow transfer after a fault, aiming at the problem of voltage stability in a receiving-end power grid caused by a high-voltage direct current line fault or power fluctuations of renewable energy. The method calculates the power flow transfer factor in the power grid after ultra-high voltage direct current blocking, combines the line load rate index and the comprehensive evaluation index of voltage weak nodes, effectively screens the set of weak nodes for voltage stability in the receiving-end power grid, and proposes an optimized configuration scheme for reactive compensation devices in the receiving-end power grid in combination with the proposed electrical distance index, providing reactive voltage support for the receiving-end power grid, effectively solving the risk of voltage instability in an important AC transmission channel faced by the receiving-end power grid after a DC fault or power fluctuations of renewable energy, and is beneficial to improving the ultra-high voltage direct current and new energy absorption capacity of the receiving-end power grid, and ensuring the safe and stable operation of the receiving-end power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0110] By referring to the following drawings, a more complete understanding of the exemplary embodiments of the present application can be obtained:

[0111] Figure 1 A schematic flow chart of a method for optimizing configuration of reactive power compensation equipment in a receiving-end power grid considering power flow transfer described in this embodiment;

[0112] Figure 2 This is a flow chart of the optimal particle swarm algorithm described in this implementation mode;

[0113] Figure 3 A schematic diagram of AC and DC connections between a provincial power grid and the outside world described in this implementation mode;

[0114] Figure 4 This is a schematic diagram of a system for optimizing configuration of reactive compensation equipment in a receiving-end power grid taking power flow transfer into consideration according to this embodiment. DETAILED DESCRIPTION

[0115] Now, exemplary embodiments of the present application are introduced with reference to the accompanying drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present application in detail and completely and to fully convey the scope of the present application to those skilled in the art. The terms in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present application. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0116] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0117] According to a first aspect of the present application, a method 100 for optimizing configuration of reactive power compensation equipment in a receiving-end power grid considering power flow transfer is provided, referring to Figure 1 As shown, the method 100 includes:

[0118] S101: When the high voltage direct current or new energy power in the receiving-end power grid changes, calculate the power flow transfer factor of the receiving-end power grid;

[0119] S102: Calculate a comprehensive evaluation index of voltage weak nodes based on the power flow transfer factor of the receiving-end power grid, and determine a voltage stability weak node set based on the comprehensive evaluation index;

[0120] S103: for the voltage stability weak node set, partition the nodes in the voltage stability weak node set by calculating the electrical distance index, and determine the candidate installation node set of the reactive power compensation equipment for each node partition;

[0121] S104: Calculate the sensitivity of the weak node voltage to the candidate nodes of the reactive compensation device through simulation, and determine the installation location and capacity of the reactive compensation device based on the optimal particle swarm algorithm.

[0122] Specifically, step one: calculate the power flow transfer factor of the receiving power grid.

[0123] For the receiving power grid fed by UHV DC, in order to simplify the analysis process, the UHV DC can be equivalent to a power source at the feeding point.

[0124] When the high-voltage DC or renewable energy power in the receiving grid changes, assuming that the DC feed-in point or renewable energy grid connection point is node i, when the active injection power of node i changes ΔP i When the active power change on the internal branch k of the receiving power grid is Then there is a relationship:

[0125]

[0126] In the formula, G k-i It is the power transfer factor of line k to node i.

[0127] Then for G k-i According to the rapid decomposition method flow calculation formula, we have:

[0128]

[0129] Among them, ΔP is the column vector of node injection power change, Δθ is the column vector of voltage phase angle change, B0 is the susceptance matrix established with 1 / x as the branch parameter, and X is the inverse matrix of B0.

[0130] According to formula (2), after the active power injection of node i changes, the power change caused on branch k (assuming that the node numbers at both ends are m and n respectively) is

[0131]

[0132] Therefore, G k-i The expression can be written as

[0133]

[0134] Step 2: Calculate the comprehensive evaluation index of voltage weak nodes and determine the voltage stability weak nodes.

[0135] For expected faults in the receiving grid, such as DC blocking or new energy fluctuations, the power flow change of each line in the key section is calculated using the power flow transfer factor calculated in step 1, and then the load rate of different lines is calculated according to formula (5).

[0136]

[0137] Among them, λ k is the load rate of line k after the fault, P k and P k.N are the steady-state power and rated power of line k after the fault respectively.

[0138] According to the line load rate index, when λ k When it is greater than a certain limit value, the receiving node of the line may be a weak node. However, in the actual power grid, if the receiving node has a conventional generator, phase regulator, SVC, STATCOM and other dynamic reactive compensation equipment connected, the dynamic reactive compensation equipment can provide reactive voltage support for the node after the power flow is transferred. Therefore, the influence of the dynamic reactive compensation equipment must also be considered to determine whether the node is weak.

[0139] Taking into account the sensitivity of node voltage to the reactive power output of dynamic compensation equipment and the reactive power output capacity of compensation equipment, the dynamic reactive power compensation capacity index γ of the receiving node of line k is formulated. k :

[0140]

[0141] Among them, ΔQ k is the reactive power change of the dynamic reactive power compensation device at the receiving end node of line k, ΔU k is the voltage change of the corresponding line k receiving node, Q k.max It is the reactive power output upper limit of the dynamic reactive power compensation device connected to the receiving node of line k.

[0142] The comprehensive evaluation index L of the voltage weak node is calculated by combining the line load rate index and the dynamic reactive power compensation capacity index. k :

[0143] L k =λ k -αγ k (7)

[0144] Among them, α is the adjustment coefficient, which can be determined according to the actual situation of the power grid.

[0145] Setting L k The threshold value is L k.max , if L k >L k.max , then the receiving node of line k is judged to be a weak node. By calculating the comprehensive evaluation index of weak nodes for all lines in the key sections, the voltage stability weak node set R = {i, j, ...} is finally determined.

[0146] Step 3: For the voltage stability weak node set R, partition the nodes in R by calculating the electrical distance index, and determine the candidate installation node set of reactive compensation equipment for each node partition.

[0147] After the weak nodes of voltage stability are determined, it is necessary to further clarify the alternative installation nodes of the reactive compensation device. However, due to the large number of actual receiving grid nodes, if optimization calculations are carried out for all nodes, the amount of calculation will be too large, and it may even lead to the curse of dimensionality and be unable to be solved. Therefore, it is necessary to use a certain method to conduct a preliminary screening of all nodes to obtain a set of alternative installation nodes for the reactive compensation device, so as to greatly reduce the amount of calculation and improve the calculation efficiency.

[0148] Considering that reactive power in the power system should be compensated nearby, and the weak voltage nodes in the receiving power grid may be relatively scattered after the power flow transfer occurs, the nodes in the weak node set R should be grouped according to the electrical distance between the nodes, and then the alternative installation node set of reactive power compensation equipment should be determined for each partition.

[0149] First, define the electrical distance between any two different nodes in the power grid. Defined by the node impedance matrix, we have

[0150]

[0151] Let vector I k and I i Take 1 and -1 respectively, and the rest take 0, which is equivalent to injecting positive and negative unit currents into nodes k and i in the power grid respectively. From formula (8), we can get U k and U i , then the electrical distance D between nodes k and i k.i It can be expressed as

[0152]

[0153] Define the maximum electrical distance index D max For all nodes in the set R, the electrical distance is calculated pairwise by equation (9). For any node k and i, if D k.i ≤D max , then nodes k and i are classified as the same region, and finally the set R is divided into z subsets according to the region, denoted as R1,…,R z .

[0154] Then, for each node partition, the candidate installation node set of reactive compensation equipment is determined, taking the regional subset R1 as an example. An average electrical distance calculation index D is defined, which is the average distance from node k to all nodes in the weak node set R1. It can be expressed as

[0155]

[0156] Among them, N R1 is the number of weak nodes in R1.

[0157] For each receiving grid node, calculate the average electrical distance between it and the nodes in R1. Several nodes with the smallest average electrical distance are selected as candidate nodes for reactive power compensation devices in node partition R1.

[0158] Repeat the above steps to finally obtain the candidate nodes of the reactive power compensation device in each node partition.

[0159] Step 4: Calculate the sensitivity of the weak node voltage to the reactive power of the candidate node through simulation, and use the optimal particle swarm algorithm to determine the installation location and capacity of the reactive power compensation device.

[0160] Reactive power compensation devices such as phase regulators are installed at the candidate installation nodes j, and their rated capacity is S N.jThrough time domain simulation, the voltage support effect of reactive power compensation devices at different locations on the voltage weak node i after the fault is analyzed, and the sensitivity index μ is established. ij , clarify the effect of different types of reactive power compensation devices on node voltage support:

[0161]

[0162] Among them, ΔU i is the post-fault steady-state voltage change of node i after the reactive compensation device is installed.

[0163] The objective function of this algorithm is composed of the equipment cost and the penalty function of different node voltages exceeding the constraints:

[0164] minf=∑C k +p(U) (12)

[0165] Among them, ∑C k is the total equipment cost of the reactive power compensation device in the configuration scheme, and p(U) is the penalty function caused by the voltage exceeding the limit at each node.

[0166] The constraint of the algorithm is that the steady-state voltage of each voltage-weak node under a typical fault set can be restored to the allowable range:

[0167] U i.min ≤U i ≤U i.max (13)

[0168] Then, the optimization algorithm such as the optimal particle swarm is used to solve the reactive configuration scheme. Each particle represents a reactive compensation device configuration scheme, and the function expression of different particles and their speeds is:

[0169]

[0170] Among them, α i.j is the reactive power compensation capacity at the alternative node j in scheme i, v i.j is α i.j The speed of change.

[0171] Since the optimal particle swarm algorithm is already very mature, its specific calculation process will not be described here. Only the algorithm flow chart of the optimal particle swarm in this application is listed as shown in the attached figure. Figure 2 shown.

[0172] Through iterative calculation of the optimal particle swarm, the global optimal particle is finally obtained as the optimal configuration location and capacity of the reactive power compensation device of the receiving power grid.

[0173] Taking a provincial power grid in my country as an example, under high load in the province in summer, as shown in the following figure Figure 3As shown in Table 1, the province receives active power from outside the province through four double-circuit AC lines and one UHV DC line. Under a typical operation mode, the UHV DC power is 8000MW, and the active power of each AC line (with the active power flowing into the province as positive) is shown in Table 1.

[0174] Table 1 Initial active power of AC line

[0175]

[0176] Since the UHV DC line receives a large amount of power, when a DC line fails, such as a single-pole or double-pole blockage, the active power difference generated will be mostly transferred to the AC line, which will greatly increase the transmission pressure of the AC line and cause the voltage at the AC receiving node to drop or even become unstable. Therefore, a dynamic reactive power compensation device needs to be installed to effectively avoid voltage instability.

[0177] First, according to the proposed step 1, the power flow transfer factor of AC line L1-L4 to UHV DC power is obtained respectively, and the results are shown in Table 2. Then, according to step 2, combined with the data in Table 1 and Table 2, the load rate of line L1-L4 is calculated, and the results are shown in Table 3. After investigation, the receiving nodes of line L1-L4 are not connected to dynamic reactive power compensation equipment. Therefore, it can be seen from formula (7) that the comprehensive evaluation index of voltage weak nodes is equal to the line load rate index. The line set with a comprehensive evaluation index of voltage weak nodes greater than 0.7 is selected as {L1, L2, L3}, so the voltage stability weak node set R = {1, 2, 3} is determined.

[0178] Table 2 Power flow transfer factors of AC lines to UHV DC lines

[0179]

[0180] Table 3 AC line load factor λ k

[0181]

[0182] According to step 3, considering that the voltage stability weak nodes 1, 2, and 3 in this example are close in electrical distance, the above nodes are uniformly divided into the same area for analysis, and no separate partitions are performed. For the receiving-end grid nodes, the average electrical distance D between them and the weak nodes is calculated one by one, and finally the five nodes {1, 2, 3, 6, 7} with the smallest D value are selected as the candidate installation nodes for the reactive compensation device.

[0183] Based on step 4, taking the phase regulator as an example, through time domain simulation, the sensitivity of the weak node voltage to the reactive power of the alternative node is obtained as shown in Table 4. Using the optimal particle swarm algorithm, the optimal configuration scheme of the reactive power compensation device of the power grid is finally obtained as shown in Table 5.

[0184] Table 4 Sensitivity of weak node voltage to reactive power of candidate nodes

[0185]

[0186] Table 5 Optimal configuration scheme for reactive power compensation

[0187]

[0188] The calculation results were verified by using the PSASP time-domain simulation program developed by the China Electric Power Research Institute. The steady-state voltages of each node before and after the proposed reactive power scheme was configured and after the DC bipolar blocking occurred are shown in Table 6. By comparison, it was found that the voltages of each weak voltage node were significantly improved after the reactive power compensation was configured, and the steady-state voltage of the weak nodes could be restored to above 0.9pu, meeting the grid operation requirements.

[0189] Table 6 Comparison of weak node voltage before and after reactive compensation configuration

[0190]

[0191] Therefore, in order to solve the voltage stability problem of the receiving power grid caused by high-voltage DC line faults or new energy power fluctuations, an optimal configuration method for reactive power compensation equipment in the receiving power grid considering power flow transfer after faults is proposed. The set of weak nodes for voltage stability in the receiving power grid is screened out by calculating the power flow transfer factor, line load rate and comprehensive evaluation index of weak voltage nodes. Combined with the proposed electrical distance index, an optimal configuration scheme for reactive power compensation devices in the receiving power grid is proposed to provide reactive voltage support for the receiving power grid, effectively solve the risk of voltage instability in important AC transmission channels faced by the receiving power grid after DC faults or new energy power fluctuations, and is conducive to improving the UHV DC and new energy absorption capacity of the receiving power grid and ensuring the safe and stable operation of the receiving power grid.

[0192] Optionally, when the high voltage direct current or renewable energy power in the receiving-end power grid changes, the power flow transfer factor of the receiving-end power grid is calculated, including:

[0193] For the receiving grid fed by UHV DC, the UHV DC is equivalent to a power source at the feeding point. When the power of the high-voltage DC or renewable energy in the receiving grid changes, assuming that the DC feeding point or renewable energy grid connection point is node i, when the active injection power of node i changes ΔP i When the active power change on the internal branch k of the receiving power grid is Then there is a relationship:

[0194]

[0195] In the formula, G k-i It is the power transfer factor of line k to node i;

[0196] Based on the relationship, G k-i The expression is derived, and according to the rapid decomposition method flow calculation formula, we have:

[0197]

[0198] Among them, ΔP is the column vector of node injection power change, Δθ is the column vector of voltage phase angle change, B0 is the susceptance matrix established with 1 / x as the branch parameter, and X is the inverse matrix of B0;

[0199] According to formula (2), after the active power injection of node i changes, the power change caused on branch k, assuming that the node numbers at both ends are m and n respectively, is

[0200]

[0201] The power flow transfer factor G of the receiving power grid k-i The expression is

[0202]

[0203] Optionally, based on the power flow transfer factor of the receiving-end power grid, calculating a comprehensive evaluation index of voltage weak nodes, and determining a voltage stability weak node set based on the comprehensive evaluation index, comprises:

[0204] For the expected fault of the receiving power grid, based on the power flow transfer factor of the receiving power grid, the power flow change of each line in the key section is calculated, and the line load rate index is obtained according to formula (5):

[0205]

[0206] Among them, λ k is the load rate index of line k after the fault, P k and P k.N are the steady-state power and rated power of line k after the fault respectively;

[0207] Taking into account the sensitivity of node voltage to the reactive power output of dynamic compensation equipment and the reactive power output capacity of compensation equipment, the dynamic reactive power compensation capacity index γ of the receiving node of line k is formulated. k :

[0208]

[0209] Among them, ΔQ k is the reactive power change of the dynamic reactive power compensation device at the receiving end node of line k, ΔU k is the voltage change of the corresponding line k receiving node, Q k.max The reactive power output upper limit of the dynamic reactive power compensation device connected to the receiving node of line k;

[0210] Based on the line load rate index and dynamic reactive power compensation capability index, the voltage weak node comprehensive evaluation index L is calculated. k :

[0211] L k =λ k -αγ k (7)

[0212] Among them, α is the adjustment coefficient, which can be determined according to the actual situation of the power grid;

[0213] Set the comprehensive evaluation index L of the voltage weak node k The threshold value is L k.max , if L k >L k.max , then the receiving node of line k is judged to be a weak node, and the voltage stability weak node set R = {i, j, …} is determined by calculating the comprehensive evaluation index of weak nodes for all lines in the key section.

[0214] Optionally, for the voltage stability weak node set, the nodes in the voltage stability weak node set are partitioned by calculating the electrical distance index, and a candidate installation node set of the reactive power compensation device is determined for each node partition, including:

[0215] The electrical distance between any two different nodes in the power grid is defined by the node impedance matrix:

[0216]

[0217] Let vector I k and I i Take 1 and -1 respectively, and the rest take 0, which is equivalent to injecting positive and negative unit currents into nodes k and i in the power grid respectively. From formula (8), we can get U k and U i , then the electrical distance D between nodes k and i k.i Expressed as

[0218] D k.i =|U k -U i |=|Z kk +Z ii -2Z ki | (9)

[0219] Define the maximum electrical distance index D max , for all nodes in the set R, the electrical distance is calculated pairwise by equation (9). For any node k and i, if D k.i ≤D max , then nodes k and i are classified as the same region, and the set R is divided into z subsets according to the region, denoted as R1, ..., R z;

[0220] Determine the candidate installation node set of reactive compensation equipment for each node partition, define an average electrical distance calculation index D, the average distance from node k to all nodes in the weak node set R1 Expressed as

[0221]

[0222] Among them, N R1 is the number of weak nodes in R1;

[0223] For each receiving grid node, calculate the average electrical distance between it and the nodes in R1. Select several nodes with the smallest average electrical distance as candidate nodes for reactive power compensation devices in node partition R1;

[0224] Repeat the above steps until the candidate nodes of the reactive power compensation device in each node partition are obtained.

[0225] Optionally, the sensitivity of the weak node voltage to the candidate node of the reactive power compensation device is calculated through simulation, and the installation location and capacity of the reactive power compensation device are determined based on the optimal particle swarm algorithm, including:

[0226] Reactive power compensation devices are set at the candidate installation nodes j, and their rated capacity is S N.j Through time domain simulation, the voltage support effect of reactive power compensation devices at different locations on the voltage weak node i after the fault is analyzed. By establishing the sensitivity index μ ij , determine the effect of different types of reactive compensation devices on node voltage support:

[0227]

[0228] Among them, ΔU i is the post-fault steady-state voltage change of node i after the reactive compensation device is installed;

[0229] The objective function of the optimal particle swarm algorithm is determined based on the penalty function of equipment cost and different node voltages exceeding the constraint conditions:

[0230] minf=∑C k +p(U) (12)

[0231] Among them, ∑C k is the total equipment cost of the reactive power compensation device in the configuration scheme, p(U) is the penalty function caused by the voltage exceeding the limit at each node;

[0232] The constraint condition for determining the optimal particle swarm algorithm is that the steady-state voltage of each voltage-weak node under a typical fault set can be restored to the allowable range:

[0233] Ui.min ≤U i ≤U i.max (13)

[0234] The optimal particle swarm algorithm is used to solve the reactive power configuration scheme, where each particle represents a reactive power compensation device configuration scheme, and the function expressions of different particles and their speeds are:

[0235]

[0236] Among them, α i.j is the reactive power compensation capacity at the alternative node j in scheme i, v i.j is α i.j The speed of change;

[0237] The global optimal particle is obtained through iterative calculation of the optimal particle swarm, which is used as the optimal configuration location and capacity of the reactive power compensation device of the receiving-end power grid.

[0238] According to another aspect of the present application, a receiving-end power grid reactive power compensation device optimization configuration system 400 considering power flow transfer is also provided. Figure 4 As shown, the system 400 includes:

[0239] The power flow transfer factor calculation module 410 is used to calculate the power flow transfer factor of the receiving-end power grid when the high-voltage direct current or new energy power in the receiving-end power grid changes;

[0240] A voltage stability weak node set determination module 420 is used to calculate a voltage weak node comprehensive evaluation index based on the power flow transfer factor of the receiving-end power grid and determine a voltage stability weak node set;

[0241] A module 430 for determining candidate installation node sets is used to partition the nodes in the voltage stability weak node set based on the comprehensive evaluation index by calculating the electrical distance index, and to determine candidate installation node sets for reactive power compensation equipment for each node partition;

[0242] The module 440 for determining the installation location and capacity is used to calculate the sensitivity of the weak node voltage to the candidate nodes of the reactive compensation device through simulation, and determine the installation location and capacity of the reactive compensation device based on the optimal particle swarm algorithm.

[0243] Optionally, a module for calculating a power flow transfer factor includes:

[0244] The power flow transfer factor calculation submodule is used for the receiving grid of UHV DC feed-in. The UHV DC is equivalent to the power supply at the feed-in point. When the power of the high-voltage DC or new energy in the receiving grid changes, the DC feed-in point or the new energy grid connection point is assumed to be node i. When the active injection power of node i changes ΔP iWhen the active power change on the internal branch k of the receiving power grid is Then there is a relationship:

[0245]

[0246] In the formula, G k-i It is the power transfer factor of line k to node i;

[0247] Based on the relationship, G k-i The expression is derived, and according to the rapid decomposition method flow calculation formula, we have:

[0248]

[0249] Among them, ΔP is the column vector of node injection power change, Δθ is the column vector of voltage phase angle change, B0 is the susceptance matrix established with 1 / x as the branch parameter, and X is the inverse matrix of B0;

[0250] According to formula (2), after the active power injection of node i changes, the power change caused on branch k, assuming that the node numbers at both ends are m and n respectively, is

[0251]

[0252] The power flow transfer factor G of the receiving power grid k-i The expression is

[0253]

[0254] Optionally, the module for determining a voltage stability weak node set includes:

[0255] The line load rate index submodule is used to calculate the power flow change of each line in the key section based on the power flow transfer factor of the receiving power grid for the expected fault of the receiving power grid, and obtain the line load rate index according to formula (5):

[0256]

[0257] Among them, λ k is the load rate index of line k after the fault, P k and P k.N are the steady-state power and rated power of line k after the fault respectively;

[0258] The dynamic reactive power compensation capability index submodule is formulated to comprehensively consider the sensitivity of the node voltage to the reactive power output of the dynamic compensation equipment and the reactive power output capacity of the compensation equipment, and formulate the dynamic reactive power compensation capability index γk of the receiving node of line k:

[0259]

[0260] Among them, ΔQ k is the reactive power change of the dynamic reactive power compensation device at the receiving end node of line k, ΔU k is the voltage change of the corresponding line k receiving node, Q k.max The reactive power output upper limit of the dynamic reactive power compensation device connected to the receiving node of line k;

[0261] The submodule for calculating the comprehensive evaluation index of the weak voltage node is used to calculate the comprehensive evaluation index L of the weak voltage node based on the line load rate index and the dynamic reactive power compensation capability index. k :

[0262] L k =λ k -αγ k (7)

[0263] Among them, α is the adjustment coefficient, which can be determined according to the actual situation of the power grid;

[0264] Determine the voltage stability weak node set submodule, which is used to set the voltage weak node comprehensive evaluation index L k The threshold value is L k.max , if L k >L k.max , then the receiving node of line k is judged to be a weak node, and the voltage stability weak node set R = {i, j, …} is determined by calculating the comprehensive evaluation index of weak nodes for all lines in the key section.

[0265] Optionally, determine the node-set modules that can be installed, including:

[0266] The electrical distance determination submodule is used to define the electrical distance between any two different nodes in the power grid, which is defined by the node impedance matrix.

[0267]

[0268] Let vector I k and I i Take 1 and -1 respectively, and the rest take 0, which is equivalent to injecting positive and negative unit currents into nodes k and i in the power grid respectively. From formula (8), we can get U k and U i , then the electrical distance D between nodes k and i k.i Expressed as

[0269] D k.i =|U k -U i |=|Z kk +Z ii -2Z ki | (9)

[0270] Divide the voltage stability weak node set into submodules to define the maximum electrical distance index D max , for all nodes in the voltage stability weak node set R, the electrical distance is calculated pairwise by equation (9). For any node k and i, if D k.i ≤D max , then nodes k and i are classified into the same region, and the voltage stability weak node set R is divided into z subsets according to the region, denoted as R1,…,R z ;

[0271] The node average distance determination submodule is used to determine the candidate installation node set of reactive compensation equipment for each node partition, and define an average electrical distance calculation index D, the average distance from node k to all nodes in the weak node set R1 Expressed as

[0272]

[0273] Among them, N R1 is the number of weak nodes in R1;

[0274] Determine the candidate node submodule for reactive power compensation device, which is used to calculate the average electrical distance between the receiving end grid node and the node in R1 one by one Select several nodes with the smallest average electrical distance as candidate nodes for reactive power compensation devices in node partition R1;

[0275] Repeat the above steps until the candidate nodes of the reactive power compensation device in each node partition are obtained.

[0276] Optionally, determining the installation location and capacity module includes:

[0277] A sensitivity index submodule is established to set reactive power compensation devices at candidate installation nodes j, with a rated capacity of S N.j Through time domain simulation, the voltage support effect of reactive power compensation devices at different locations on the voltage weak node i after the fault is analyzed. By establishing the sensitivity index μ ij , determine the effect of different types of reactive compensation devices on node voltage support:

[0278]

[0279] Among them, ΔU i is the post-fault steady-state voltage change of node i after the reactive compensation device is installed;

[0280] The objective function determination submodule is used to determine the objective function of the optimal particle swarm algorithm based on the equipment cost and the penalty function of different node voltages exceeding the constraint conditions:

[0281] minf=∑Ck +p(U) (12)

[0282] Among them, ∑C k is the total equipment cost of the reactive power compensation device in the configuration scheme, p(U) is the penalty function caused by the voltage exceeding the limit at each node;

[0283] The constraint determination submodule is used to determine the constraint of the optimal particle swarm algorithm, which is that the steady-state voltage of each voltage-weak node under the typical fault set can be restored to the allowable range:

[0284] U i.min ≤U i ≤U i.max (13)

[0285] Determine different particles and their speed submodules, which are used to solve the reactive configuration scheme using the optimal particle swarm algorithm, where each particle represents a reactive compensation device configuration scheme, and the function expressions of different particles and their speeds are:

[0286]

[0287] Among them, α i.j is the reactive power compensation capacity at the alternative node j in scheme i, v i.j is α i.j The speed of change;

[0288] The optimal configuration location and capacity submodule is used to determine the optimal configuration location and capacity of the reactive power compensation device of the receiving-end power grid, and obtain the global optimal particle through iterative calculation of the optimal particle swarm.

[0289] A system 400 for optimizing configuration of reactive compensation equipment in a receiving power grid considering power flow transfer in an embodiment of the present application corresponds to a method 100 for optimizing configuration of reactive compensation equipment in a receiving power grid considering power flow transfer in another embodiment of the present application, which will not be described in detail here.

[0290] According to another aspect of the present application, a computer-readable storage medium is provided, on which a computer program is stored, and when the program is executed by a processor, the steps of any of the methods described above are implemented.

[0291] According to another aspect of the present application, an electronic device is provided, including: a computer-readable storage medium; and one or more processors for executing a program in the computer-readable storage medium.

[0292] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0293] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0294] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0295] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0296] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0297] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for optimizing configuration of reactive power compensation equipment in a receiving-end power grid considering power flow transfer, characterized in that: include: When the high voltage DC or new energy power in the receiving grid changes, calculate the power flow transfer factor of the receiving grid; Based on the power flow transfer factor of the receiving-end power grid, a comprehensive evaluation index of voltage weak nodes is calculated, and a voltage stability weak node set is determined based on the comprehensive evaluation index; For the weak voltage stability node set, the nodes in the weak voltage stability node set are partitioned by calculating the electrical distance index, and the candidate installation node set of reactive power compensation equipment is determined for each node partition; Through simulation, the sensitivity of weak node voltage to the alternative nodes of reactive compensation device is calculated, and the installation location and capacity of reactive compensation device are determined based on the optimal particle swarm algorithm.

2. The method according to claim 1, characterized in that When the high voltage DC or renewable energy power in the receiving grid changes, the power flow transfer factor of the receiving grid is calculated, including: For the receiving grid fed by UHV DC, the UHV DC is equivalent to a power source at the feeding point. When the power of the high-voltage DC or renewable energy in the receiving grid changes, assuming that the DC feeding point or renewable energy grid connection point is node i, when the active injection power of node i changes ΔP i When the active power change on the internal branch k of the receiving power grid is Then there is a relationship: In the formula, G k-i It is the power transfer factor of line k to node i; Based on the relationship, G k-i The expression is derived, and according to the rapid decomposition method flow calculation formula, we have: Among them, ΔP is the column vector of node injection power change, Δθ is the column vector of voltage phase angle change, B0 is the susceptance matrix established with 1 / x as the branch parameter, and X is the inverse matrix of B0; According to formula (2), after the active power injection of node i changes, the power change caused on branch k, assuming that the node numbers at both ends are m and n respectively, is The power flow transfer factor G of the receiving power grid k-i The expression is 3. The method according to claim 1, characterized in that Based on the power flow transfer factor of the receiving-end power grid, a comprehensive evaluation index of voltage weak nodes is calculated, and based on the comprehensive evaluation index, a set of voltage stability weak nodes is determined, including: For the expected fault of the receiving power grid, based on the power flow transfer factor of the receiving power grid, the power flow change of each line in the key section is calculated, and the line load rate index is obtained according to formula (5): Among them, λ k is the load rate index of line k after the fault, P k and P k.N are the steady-state power and rated power of line k after the fault respectively; Taking into account the sensitivity of node voltage to the reactive power output of dynamic compensation equipment and the reactive power output capacity of compensation equipment, the dynamic reactive power compensation capacity index γk of the receiving node of line k is formulated: Among them, ΔQ k is the reactive power change of the dynamic reactive power compensation device at the receiving end node of line k, ΔU k is the voltage change of the corresponding line k receiving node, Q k.max The reactive power output upper limit of the dynamic reactive power compensation device connected to the receiving node of line k; Based on the line load rate index and dynamic reactive power compensation capability index, the voltage weak node comprehensive evaluation index L is calculated. k : L k =λ k -ag k (7) Among them, α is the adjustment coefficient, which can be determined according to the actual situation of the power grid; Set the comprehensive evaluation index L of the voltage weak node k The threshold value is L k.max , if L k >L k.max , then the receiving node of line k is judged to be a weak node, and the voltage stability weak node set R = {i, j, …} is determined by calculating the comprehensive evaluation index of weak nodes for all lines in the key section.

4. The method according to claim 1, characterized in that For the weak voltage stability node set, the nodes in the weak voltage stability node set are partitioned by calculating the electrical distance index, and the candidate installation node set of reactive power compensation equipment is determined for each node partition, including: The electrical distance between any two different nodes in the power grid is defined by the node impedance matrix: Let vector I k and I i Take 1 and -1 respectively, and the rest take 0, which is equivalent to injecting positive and negative unit currents into nodes k and i in the power grid respectively. From formula (8), we can get U k and U i , then the electrical distance D between nodes k and i k.i Expressed as D k.i =|U k -U i |=|Z kk +Z ii -2Z ki | (9) Define the maximum electrical distance index D max For all nodes in the set R, the electrical distance is calculated pairwise by equation (9). For any node k and i, if D k.i ≤D max , then nodes k and i are classified into the same region, and the set R is divided into z subsets according to the region, denoted as R1, ..., R z ; For each node partition, the candidate installation node set of reactive compensation equipment is determined respectively, and an average electrical distance calculation index D is defined, which is the average distance D from node k to all nodes in the weak node set R1. k 1 Expressed as Among them, N R1 is the number of weak nodes in R1; For each receiving grid node, calculate the average electrical distance between it and the nodes in R1. Select several nodes with the smallest average electrical distance as candidate nodes for reactive power compensation devices in node partition R1; Repeat the above steps until the candidate nodes of the reactive power compensation device in each node partition are obtained.

5. The method according to claim 1, characterized in that: Through simulation, the sensitivity of the weak node voltage to the candidate nodes of the reactive compensation device is calculated, and the installation location and capacity of the reactive compensation device are determined based on the optimal particle swarm algorithm, including: Reactive power compensation devices are set at the candidate installation nodes j, and their rated capacity is S N.j Through time domain simulation, the voltage support effect of reactive power compensation devices at different locations on the voltage weak node i after the fault is analyzed. By establishing the sensitivity index μ ij , determine the effect of different types of reactive compensation devices on node voltage support: Among them, ΔU i is the post-fault steady-state voltage change of node i after the reactive compensation device is installed; The objective function of the optimal particle swarm algorithm is determined based on the penalty function of equipment cost and different node voltages exceeding the constraint conditions: min f=∑C k +p(U) (12) Among them, ∑C k is the total equipment cost of the reactive power compensation device in the configuration scheme, p(U) is the penalty function caused by the voltage exceeding the limit at each node; The constraint condition for determining the optimal particle swarm algorithm is that the steady-state voltage of each voltage-weak node under a typical fault set can be restored to the allowable range: IN i.min ≤U i ≤U i.max (13) The optimal particle swarm algorithm is used to solve the reactive power configuration scheme, where each particle represents a reactive power compensation device configuration scheme, and the function expressions of different particles and their speeds are: Among them, α i.j is the reactive power compensation capacity at the alternative node j in scheme i, v i.j is α i.j The speed of change; The global optimal particle is obtained through iterative calculation of the optimal particle swarm, which is used as the optimal configuration location and capacity of the reactive power compensation device of the receiving-end power grid.

6. A system for optimizing configuration of reactive power compensation equipment in a receiving-end power grid considering power flow transfer, characterized in that: include: A power flow transfer factor calculation module is used to calculate the power flow transfer factor of the receiving power grid when the high voltage direct current or new energy power in the receiving power grid changes; A module for determining a set of weak voltage stability nodes, used to calculate a comprehensive evaluation index of weak voltage nodes based on a power flow transfer factor of the receiving-end power grid, and determine a set of weak voltage stability nodes based on the comprehensive evaluation index; A module for determining candidate installation node sets is used to partition the nodes in the voltage stability weak node set by calculating the electrical distance index, and determine the candidate installation node set of reactive power compensation equipment for each node partition; The module for determining the installation location and capacity is used to calculate the sensitivity of the weak node voltage to the candidate nodes of the reactive compensation device through simulation, and determine the installation location and capacity of the reactive compensation device based on the optimal particle swarm algorithm.

7. The system according to claim 6, characterized in that Module for calculating power flow transfer factors, including: The power flow transfer factor calculation submodule is used for the receiving grid of UHV DC feed-in. The UHV DC is equivalent to the power supply at the feed-in point. When the power of the high-voltage DC or new energy in the receiving grid changes, the DC feed-in point or the new energy grid connection point is assumed to be node i. When the active injection power of node i changes ΔP i When the active power on the internal branch k of the receiving power grid changes to ΔP k i , then there is a relationship: In the formula, G k-i It is the power transfer factor of line k to node i; Based on the relationship, G k-i The expression is derived, and according to the rapid decomposition method flow calculation formula, we have: Among them, ΔP is the column vector of node injection power change, Δθ is the column vector of voltage phase angle change, B0 is the susceptance matrix established with 1 / x as the branch parameter, and X is the inverse matrix of B0; According to formula (2), after the active power injection of node i changes, the power change caused on branch k, assuming that the node numbers at both ends are m and n respectively, is The power flow transfer factor G of the receiving power grid k-i The expression is 8. The system according to claim 6, characterized in that The module for determining the weak node set of voltage stability includes: The line load rate index submodule is used to calculate the power flow change of each line in the key section based on the power flow transfer factor of the receiving power grid for the expected fault of the receiving power grid, and obtain the line load rate index according to formula (5): Among them, λ k is the load rate index of line k after the fault, P k and P k.N are the steady-state power and rated power of line k after the fault respectively; Formulate a dynamic reactive power compensation capability index submodule, which is used to comprehensively consider the sensitivity of node voltage to the reactive power output of dynamic compensation equipment and the reactive power output capacity of compensation equipment, and formulate the dynamic reactive power compensation capability index γ of the receiving node of line k k : Among them, ΔQ k is the reactive power change of the dynamic reactive power compensation device at the receiving end node of line k, ΔU k is the voltage change of the corresponding line k receiving node, Q k.max The reactive power output upper limit of the dynamic reactive power compensation device connected to the receiving node of line k; The submodule for calculating the comprehensive evaluation index of the weak voltage node is used to calculate the comprehensive evaluation index L of the weak voltage node based on the line load rate index and the dynamic reactive power compensation capability index. k : L k =λ k -ag k (7) Among them, α is the adjustment coefficient, which can be determined according to the actual situation of the power grid; Determine the voltage stability weak node set submodule, which is used to set the voltage weak node comprehensive evaluation index L k The threshold value is L k.max , if L k >L k.max , then the receiving node of line k is judged to be a weak node, and the voltage stability weak node set R = {i, j, …} is determined by calculating the comprehensive evaluation index of weak nodes for all lines in the key section.

9. The system according to claim 6, characterized in that Identify alternative installation node assembly modules, including: The electrical distance determination submodule is used to define the electrical distance between any two different nodes in the power grid, which is defined by the node impedance matrix. Let vector I k and I i Take 1 and -1 respectively, and the rest take 0, which is equivalent to injecting positive and negative unit currents into nodes k and i in the power grid respectively. From formula (8), we can get U k and U i , then the electrical distance D between nodes k and i k.i Expressed as D k.i =|U k -U i |=|Z kk +Z ii -2Z ki | (9) Divide the voltage stability weak node set into submodules to define the maximum electrical distance index D max , for all nodes in the voltage stability weak node set R, the electrical distance is calculated pairwise by equation (9). For any node k and i, if D k.i ≤D max , then nodes k and i are classified into the same region, and the voltage stability weak node set R is divided into z subsets according to the region, denoted as R1,…,R z ; The node average distance determination submodule is used to determine the candidate installation node set of reactive compensation equipment for each node partition, and define an average electrical distance calculation index D, the average distance from node k to all nodes in the weak node set R1 Expressed as Among them, N R1 is the number of weak nodes in R1; Determine the candidate node submodule for reactive power compensation device, which is used to calculate the average electrical distance between the receiving end grid node and the node in R1 one by one Select several nodes with the smallest average electrical distance as candidate nodes for reactive power compensation devices in node partition R1; Repeat the above steps until the candidate nodes of the reactive power compensation device in each node partition are obtained.

10. The system according to claim 6, characterized in that Determine the installation location and capacity modules include: A sensitivity index submodule is established to set reactive power compensation devices at candidate installation nodes j, with a rated capacity of S N.j Through time domain simulation, the voltage support effect of reactive power compensation devices at different locations on the voltage weak node i after the fault is analyzed. By establishing the sensitivity index μ ij , determine the effect of different types of reactive compensation devices on node voltage support: Among them, ΔU i is the post-fault steady-state voltage change of node i after the reactive compensation device is installed; The objective function determination submodule is used to determine the objective function of the optimal particle swarm algorithm based on the equipment cost and the penalty function of different node voltages exceeding the constraint conditions: min f=∑C k +p(U) (12) Among them, ∑C k is the total equipment cost of the reactive power compensation device in the configuration scheme, p(U) is the penalty function caused by the voltage exceeding the limit at each node; The constraint determination submodule is used to determine the constraint of the optimal particle swarm algorithm, which is that the steady-state voltage of each voltage-weak node under the typical fault set can be restored to the allowable range: IN i.min ≤U i ≤U i.max (13) Determine different particles and their speed submodules, which are used to solve the reactive configuration scheme using the optimal particle swarm algorithm, where each particle represents a reactive compensation device configuration scheme, and the function expressions of different particles and their speeds are: Among them, α i.j is the reactive power compensation capacity at the alternative node j in scheme i, v i.j is α i.j The speed of change; The optimal configuration location and capacity submodule is used to determine the optimal configuration location and capacity of the reactive power compensation device of the receiving-end power grid, and obtain the global optimal particle through iterative calculation of the optimal particle swarm.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

12. An electronic device, characterized in that: include: The computer readable storage medium as claimed in claim 11; as well as One or more processors are used to execute the program in the computer-readable storage medium.

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