A method and system for optimal configuration of reactive power compensation equipment of a receiving end power grid considering tidal flow transfer

Abstract

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

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of receiving-end power grid, and more particularly, to a method and system for optimal configuration of reactive power compensation equipment of receiving-end power grid considering power flow transfer. BACKGROUND

[0002] The ultra-high voltage direct current system has the characteristics of large capacity, controllability and flexibility, and has been widely used in large regional power grid interconnection, long-distance large-capacity power transmission and cross-strait power transmission. However, due to the large power of the ultra-high voltage direct current transmission, when it is blocked due to failure or runs at a reduced power, a large-scale power flow transfer will occur in the receiving-end power grid, which may lead to 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 cause power flow transfer within the power grid, and further lead to voltage instability. In view of the above problems, it is urgent to study the optimal configuration scheme of reactive power compensation devices of the receiving-end power grid to provide reactive power voltage support for the power grid and ensure the safe and stable operation of the receiving-end power grid. SUMMARY

[0003] In view of the above problems, the present application provides a method and system for optimal configuration of reactive power compensation equipment of receiving-end power grid considering power flow transfer, to solve the technical problem that due to the large power of the ultra-high voltage direct current transmission, when it is blocked due to failure or runs at a reduced power, a large-scale power flow transfer will occur in the receiving-end power grid, which may lead to 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 cause power flow transfer within the power grid, and further lead to voltage instability.

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

[0005] 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;

[0006] Based on the power flow transfer factor of the receiving-end power grid, calculate the comprehensive evaluation index of voltage weak nodes, and determine the set of voltage stability weak nodes based on the comprehensive evaluation index;

[0007] For the set of voltage stability weak nodes, by calculating the electrical distance index, the nodes in the set of voltage stability weak nodes are partitioned, and the set of alternative installation nodes 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 power compensation devices is calculated, and the installation location and capacity of the reactive power compensation devices are determined based on the optimal particle swarm algorithm.

[0009] Optionally, when the high-voltage direct current or new 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 end power grid fed by the ultra-high voltage direct current, the ultra-high voltage direct current is equivalent to a power source at the feeding point, when the high-voltage direct current or new energy power in the receiving end power grid changes, assuming that the direct current feeding point or the new energy grid connection point is node i, when the active power injection power of node i changes ΔP i , the active power change amount on the branch k in the receiving end power grid will be , then there is a relationship:

[0011]

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

[0013] Based on the relationship, the expression of G k-i is derived, according to the fast decomposition method power flow calculation formula, there is:

[0014]

[0015] Where, ΔP is the node injection power change column vector, Δθ is the voltage phase angle change column vector, B0 is the admittance matrix established by taking 1 / x as the branch parameter, and X is the inverse matrix of B0;

[0016] According to formula (2), after the active injection power of node i changes, the power change amount on the branch k, assuming that the two end node numbers are m and n, is

[0017]

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

[0019]

[0020] Optionally, 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, including:

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

[0022]

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

[0024] The dynamic reactive power compensation capability index γ of the line k receiving end node is formulated by comprehensively considering the sensitivity of the node voltage to the dynamic compensation device reactive power output and the reactive power output capability of the compensation device k :

[0025]

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

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

[0028] L k =λ k -αγ k (7)

[0029] wherein, α is an adjustment coefficient, which can be valued according to the actual situation of the power grid;

[0030] The voltage weak node comprehensive evaluation index L k is set as a threshold value L k.max , if L k >L k.max , it is judged that the line k receiving end node is a weak node, the voltage stability weak node set R={i,j,…} is determined by calculating the voltage weak node comprehensive evaluation index of all lines of 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 the alternative 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, which is defined by the node impedance matrix, and has

[0033]

[0034] Let the vector I take 1 and -1 respectively in I k and I i , and the rest take 0, which is equivalent to injecting positive and negative unit currents at the nodes k and i in the power grid respectively, and U kand U i , the electrical distance D k.i between node k and i is represented as

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

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

[0037] The candidate installation node set of the reactive power compensation device is determined for each node partition, and an average electrical distance calculation index D is defined, which is the average distance from node k to all nodes in weak node set R1 is represented as

[0038]

[0039] where N R1 is the number of weak nodes in R1;

[0040] The average electrical distance of each node in the receiving end power grid to the nodes in R1 is calculated one by one The nodes with the smallest average electrical distance are selected as the candidate nodes of the reactive power compensation device for node partition R1;

[0041] The above steps are repeated until the candidate nodes of the reactive power compensation device for 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] The reactive power compensation device is set at the candidate installation node j, and the rated capacity is S N.j , the voltage support effect of the reactive power compensation device at different locations on the weak node i after the fault is analyzed through time domain simulation, and the sensitivity index μ ij is established to determine the voltage support effect of different types of reactive power compensation devices on the node voltage:

[0044]

[0045] where ΔUi is the post-fault steady-state voltage variation of node i after installation of the reactive power compensation device;

[0046] The objective function of the optimal particle swarm algorithm is determined according to the equipment cost and the penalty function of the voltage of different nodes exceeding the constraint condition:

[0047] minf =∑C k + p(U) (12)

[0048] wherein ∑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 over-limit of the voltage of each node;

[0049] The constraint condition of the optimal particle swarm algorithm is that the steady-state voltage of each voltage weak node under the 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, wherein each particle represents a reactive power compensation device configuration scheme, and the function expression of different particles and their velocities is:

[0052]

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

[0054] Through the optimal particle swarm iterative calculation, the global optimal particle obtained 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 reactive power compensation equipment optimal configuration system of a receiving end power grid considering power flow transfer is also provided, comprising:

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

[0057] A voltage stability weak node set determination module is configured to calculate a comprehensive evaluation index of a voltage weak node 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;

[0058] The determining alternative installation node set module is configured to partition nodes in the voltage stability weak node set by calculating the electrical distance index, and determine the alternative installation node set of the reactive power compensation device for each node partition respectively;

[0059] The determining installation site and capacity module is configured to calculate the sensitivity of the weak node voltage to the alternative node of the reactive power compensation device by simulation, and determine the installation site and capacity of the reactive power compensation device based on the optimal particle swarm algorithm.

[0060] Optionally, the power flow transfer factor calculation module comprises:

[0061] The power flow transfer factor calculation submodule is configured to, for an HVDC-fed receiving end power grid, equivalent the HVDC to a power source at the feeding point, when the high-voltage direct current or new energy power in the receiving end power grid changes, assume that the HVDC feeding point or the new energy grid-connected point is node i, when the active power injection power of node i changes ΔP i , the active power change amount of the internal branch k of the receiving end power grid will be , and the relationship is:

[0062]

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

[0064] Based on the relationship, the expression of G k-i is derived, and according to the fast decomposition method power flow calculation formula, there is:

[0065]

[0066] Where, ΔP is the node injection power change column vector, Δθ is the voltage phase angle change column vector, B0 is the admittance matrix established by taking 1 / x as the branch parameter, and X is the inverse matrix of B0;

[0067] According to formula (2), after the active injection power of node i changes, the power change amount of branch k, assuming that the two end nodes are m and n, is

[0068]

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

[0070]

[0071] Optionally, the determining voltage stability weak node set module comprises:

[0072] The submodule for obtaining the line load rate index 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-end power grid in response to anticipated faults in the receiving-end power grid, and to obtain the line load rate index according to equation (5):

[0073]

[0074] Where, λ k P represents the load factor of line k after a fault. k and P k.N These are the steady-state power and rated power of line k after the fault, respectively;

[0075] A submodule for defining dynamic reactive power compensation capability indicators is developed to comprehensively consider the sensitivity of node voltage to the reactive power output of dynamic compensation equipment, as well as the reactive power output capability of the compensation equipment, and to formulate the dynamic reactive power compensation capability indicator γ for the receiving-end node of line k. k :

[0076]

[0077] Where, ΔQ k Let ΔU be the reactive power change of the dynamic reactive power compensation equipment at the receiving end node of line k. k Q represents the voltage change at the corresponding receiving node k of the line. k.max The upper limit of reactive power output of the dynamic reactive power compensation equipment connected to the receiving node of line k;

[0078] The submodule for calculating the comprehensive evaluation index of voltage weak nodes is used to calculate the comprehensive evaluation index L of voltage weak nodes 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] Wherein, α is the adjustment coefficient, which can be selected according to the actual situation of the power grid;

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

[0082] Optionally, alternative installation node set modules are determined, including:

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

[0084]

[0085] Let vector I contain I k and I i Taking values ​​of 1 and -1 respectively, and 0 for the rest, is equivalent to injecting positive and negative unit currents at nodes k and i in the power grid, respectively. U is obtained from equation (8). k and U i Then the electrical distance D between node k and i k.i Represented as

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

[0087] The voltage stability weak node set is divided into sub-modules 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 using equation (9). For any nodes k and i, if D k.i ≤D max Then, nodes k and i are grouped into the same region, and the set of weak voltage-stability nodes R is divided into z subsets according to the region, denoted as R1, ..., R2. z ;

[0088] The submodule for determining the average node distance is used to identify the candidate installation node set for reactive power compensation equipment for each node partition. It defines an average electrical distance calculation index D, which is the average distance from node k to all nodes in the weak node set R1. Represented as

[0089]

[0090] Where, N R1 This represents the number of weak nodes in R1.

[0091] The candidate node submodule for determining reactive power compensation devices is used to calculate the average electrical distance D between each receiving-end grid node and the nodes in R1. k 1 Several nodes with the smallest average electrical distance are selected as candidate nodes for the reactive power compensation device of node partition R1.

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

[0093] Optionally, the determining installation site and capacity module comprises:

[0094] The sensitivity index establishing sub-module is configured to set the reactive power compensation device at the candidate installation node j with a rated capacity of S N.j The time domain simulation is used to analyze the voltage support effect of the reactive power compensation device at different sites on the weak node i after the fault, and the sensitivity index μ ij is established to determine the voltage support effect of the different types of reactive power compensation devices on the node:

[0095]

[0096] Wherein, ΔU i is the change of the steady-state voltage of the node i after the fault after the installation of the reactive power compensation device;

[0097] The target function determining sub-module is configured to determine the target function of the optimal particle swarm algorithm according to the device cost and the penalty function of the voltage exceeding the constraint condition of different nodes:

[0098] min f =∑C k + p(U) (12)

[0099] Wherein, ∑C k is the total device cost of the reactive power compensation device in the configuration scheme, and p(U) is the penalty function caused by the voltage out-of-limit of each node;

[0100] The constraint condition determining sub-module is configured to determine the constraint condition of the optimal particle swarm algorithm as the steady-state voltage of each weak node under the typical fault set being able to recover to the allowable range:

[0101] U i.min ≤ U i ≤ U i.max (13)

[0102] The different particle and velocity determining sub-module is configured to solve the reactive power configuration scheme by using the optimal particle swarm algorithm, wherein each particle represents a reactive power compensation device configuration scheme, and the function expression of the different particle and velocity is:

[0103]

[0104] Wherein, α i.j is the reactive power compensation capacity at the candidate node j in the scheme i, v i.j is the change speed of α i.j ;

[0105] The optimal configuration site and capacity determining sub-module is configured to obtain the global optimal particle by the optimal particle swarm iterative calculation, as the optimal configuration site and capacity of the reactive power compensation device of the receiving end power grid.

[0106] According to another aspect of the present application, there is also provided a computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the method according to any one of the preceding aspects.

[0107] According to another aspect of the present application, there is also provided an electronic device comprising: a computer readable storage medium; and one or more processors configured to execute a program in the computer readable storage medium.

[0108] Therefore, the present application proposes an optimal configuration method of reactive power compensation equipment of a receiving end power grid considering post-fault power flow transfer, aiming at voltage stability problems of the receiving end power grid caused by HVDC line faults or new energy power fluctuations. By calculating the power flow transfer factor in the power grid after UHVDC blocking, combining the line load rate index and the voltage weak node comprehensive evaluation index, the weak node set of the receiving end power grid is effectively screened, and the proposed electrical distance index is combined to propose an optimal configuration scheme of the reactive power compensation device of the receiving end power grid, to provide reactive voltage support for the receiving end power grid, effectively solve the voltage instability risk of the important AC transmission channel of the receiving end power grid after DC fault or new energy power fluctuation, and is conducive to improving the UHVDC and new energy consumption capacity of the receiving end power grid, and ensuring the safe and stable operation of the receiving end power grid. BRIEF DESCRIPTION OF DRAWINGS

[0109] The exemplary embodiments of the present application can be more completely understood by reference to the following drawings:

[0110] Figure 1 A flowchart of an optimal configuration method of reactive power compensation equipment of a receiving end power grid considering power flow transfer according to the present embodiment;

[0111] Figure 2 A flowchart of an optimal particle swarm algorithm according to the present embodiment;

[0112] Figure 3 A schematic diagram of a provincial power grid and external AC / DC connection according to the present embodiment;

[0113] Figure 4 A schematic diagram of an optimal configuration system of reactive power compensation equipment of a receiving end power grid considering power flow transfer according to the present embodiment. DETAILED DESCRIPTION

[0114] Reference will now be made to the drawings to describe the exemplary embodiments of the present application in greater detail. The present application can be variously embodied and is not limited to the embodiments described herein, which are provided for the purposes of explanation and thoroughness and fully convey the scope of the application to those skilled in the art. The terminology used herein with respect to the exemplary embodiments described in the drawings is not intended to limit the present application. In the drawings, the same elements / elements are denoted by the same reference numerals.

[0115] Unless otherwise defined, the terms (including technical terms) used herein have meanings commonly understood by those skilled in the art. In addition, it is to be understood that the terms defined in commonly used dictionaries are to be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0116] According to a first aspect of the present application, a method 100 for optimizing the configuration of reactive power compensation devices in a receiving end power grid considering power flow transfer is provided, as shown in Figure 1 The method 100 comprises:

[0117] 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;

[0118] S102: Based on the power flow transfer factor of the receiving end power grid, calculate a comprehensive evaluation index of voltage weak nodes, and determine a set of voltage stability weak nodes based on the comprehensive evaluation index;

[0119] S103: For the set of voltage stability weak nodes, by calculating an electrical distance index, the nodes in the set of voltage stability weak nodes are partitioned, and for each node partition, a set of candidate installation nodes of reactive power compensation devices is determined;

[0120] S104: Through simulation, calculate the sensitivity of weak node voltage to the candidate nodes of reactive power compensation devices, and determine the installation location and capacity of the reactive power compensation devices based on the optimal particle swarm algorithm.

[0121] Specifically, step one: calculate the power flow transfer factor of the receiving end power grid.

[0122] For a receiving end power grid with ultra-high voltage direct current feeding, in order to simplify the analysis process, the ultra-high voltage direct current can be equivalent to a power source at the feeding point.

[0123] When the high-voltage direct current or new energy power in the receiving end power grid changes, assuming that the direct current feeding point or the new energy grid connection point is node i, when the active power injection of node i changes ΔP i , it will cause the active power change of branch k in the receiving end power grid to be Then there is a relationship:

[0124]

[0125] where G k-i is the power flow transfer factor of line k to node i.

[0126] Then G k-i is derived. According to the fast decoupled power flow formula, we have

[0127]

[0128] where ΔP is the column vector of node injection power variation, Δθ is the column vector of voltage phase angle variation, B0 is the admittance matrix established by 1 / x as branch parameter, and X is the inverse matrix of B0.

[0129] According to formula (2), the power variation caused by the active power injection variation of node i on branch k (assuming the node numbers at both ends are m and n) is

[0130]

[0131] Therefore, G k-i can be written as

[0132]

[0133] Step 2: Calculate the comprehensive evaluation index of voltage weak nodes to determine the voltage stability weak nodes.

[0134] For the expected faults of the receiving end power grid, such as DC blocking or new energy fluctuation, the power flow variation of each line at 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).

[0135]

[0136] where 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.

[0137] According to the line load rate index, when λ k is greater than a certain limit value, the receiving end node of the line may be a weak node. However, in the actual power grid, if the receiving end node has conventional generators, phase modulators, SVC, STATCOM, and other dynamic reactive power compensation devices connected, the dynamic reactive power compensation devices can provide reactive voltage support for the node after the power flow transfer, so whether the node is weak also needs to consider the influence of dynamic reactive power compensation devices.

[0138] The dynamic reactive power compensation capability index γ of the receiving end node of line k is formulated by comprehensively considering the sensitivity of the node voltage to the dynamic compensation device reactive power output and the reactive power output capability of the compensation device k :

[0139]

[0140] wherein, ΔQ k is the reactive power variation of the dynamic reactive power compensation device at the receiving end node of line k, ΔU k is the corresponding voltage variation of the receiving end node of line k, Q k.max is the upper limit of the reactive power output of the dynamic reactive power compensation device connected to the receiving end node of line k.

[0141] The voltage weak node comprehensive evaluation index L k :

[0142] L k = λ k - αγ k (7)

[0143] wherein, α is an adjustment coefficient, which can be valued according to the actual situation of the power grid.

[0144] The threshold value of L k is L k.max , if L k > L k.max , the receiving end node of line k is determined as a weak node. Through the weak node comprehensive evaluation index calculation of all lines of the key section, the voltage stability weak node set R = {i, j, …} is finally determined.

[0145] Step three: for the voltage stability weak node set R, the nodes in R are partitioned by calculating the electrical distance index, and the candidate installation node set of the reactive power compensation device is determined for each node partition.

[0146] After the voltage stability weak node is determined, the candidate installation node of the reactive power compensation device needs to be further determined. However, due to the large number of nodes in the actual receiving end power grid, if the optimization calculation is carried out for all nodes, the calculation amount is too large, and even the dimension disaster is caused and cannot be solved, therefore, a certain method is needed to preliminarily screen all nodes to obtain the candidate installation node set of the reactive power compensation device, so as to greatly reduce the calculation amount and improve the calculation efficiency.

[0147] Considering that the reactive power of the power system should be compensated nearby, and the voltage weak nodes in the receiving end power grid may be dispersed after the power flow transfer occurs, therefore, the nodes in the weak node set R should be grouped in combination with the electrical distance between the nodes, and the candidate installation node set of the reactive power compensation device is determined for each partition.

[0148] Firstly, the electrical distance between any two different nodes in the power grid is defined. It is defined by the node impedance matrix, and has

[0149]

[0150] Let the vector I in 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 at nodes k and i in the power grid respectively, and U k and U i are obtained respectively by formula (8). Then the electrical distance D k.i between nodes k and i can be expressed as

[0151]

[0152] Define the maximum electrical distance index D max . Calculate the electrical distance between all nodes in set R according to formula (9). For any node k and i, if D k.i ≤D max , then nodes k and i are classified into the same region. Finally, set R is divided into z subsets, denoted as R1, …, R z .

[0153] Then, the candidate installation node set of the reactive power compensation device is determined for each node partition. Take the region subset R1 as an example. Define an average electrical distance calculation index D, and the average distance of node k to all nodes in the weak node set R1 can be expressed as

[0154]

[0155] where N R1 is the number of weak nodes in R1.

[0156] For the nodes in the receiving end power grid, the average electrical distance D of each node to the nodes in R1 is calculated one by one. Select the nodes with the smallest average electrical distance as the candidate nodes for the reactive power compensation device of node partition R1.

[0157] Repeat the above steps to finally obtain the candidate nodes for the reactive power compensation device of each node partition.

[0158] Step four: through simulation, calculate the sensitivity of the weak node voltage to the reactive power of the candidate node, and use the optimal particle swarm algorithm to determine the installation location and capacity of the reactive power compensation device.

[0159] Set the reactive power compensation device such as phase modifier at the candidate installation node j, and its rated capacity is S N.j. Through time-domain simulation, the voltage support effect of reactive power compensation devices at different locations on the weak node i after fault is analyzed, and the sensitivity index μ ij is established to determine the voltage support effect of different types of reactive power compensation devices on the node voltage:

[0160]

[0161] where ΔU i is the change in steady-state voltage of node i after fault after installing the reactive power compensation device.

[0162] The objective function of the algorithm is composed of device cost and penalty function of different node voltages exceeding the constraint condition:

[0163] min f =∑C k + p(U) (12)

[0164] where ∑C k is the total device cost of the reactive power compensation device in the configuration scheme, and p(U) is the penalty function caused by the over-limit of each node voltage.

[0165] The constraint condition of the algorithm is that the steady-state voltage of each weak node under the typical fault set can be restored to the allowable range:

[0166] U i.min ≤ U i ≤ U i.max (13)

[0167] Then, optimization algorithms such as optimal particle swarm are used to solve the reactive power configuration scheme. Each particle represents a reactive power compensation device configuration scheme, and the function expression of different particles and their speeds is:

[0168]

[0169] where α i.j is the reactive power compensation capacity at the candidate node j in scheme i, and v i.j is the change speed of α i.j .

[0170] Since the optimal particle swarm algorithm is already very mature, its specific calculation process will not be described here, and only the algorithm flowchart of the optimal particle swarm in this application is listed as shown in the accompanying Figure 2 .

[0171] Through iterative calculation of the optimal particle swarm, the finally obtained global optimal particle is used as the optimal configuration location and capacity of the reactive power compensation device of the receiving end power grid.

[0172] Taking a provincial power grid in China as an example, under high-level load in summer in the province, as shown in the accompanying Figure 3The province is shown by 4 double back AC lines and 1 UHV DC line from outside the province to receive active power. In a certain typical operating mode, the UHV DC power is 8000MW, and the active power of each AC line (positive for flowing into the province) is shown in Table 1.

[0173] Table 1 AC line initial active power

[0174]

[0175] Due to the large UHV DC line power, when the DC line fails such as single pole blocking and double pole blocking, the active power difference generated will be mostly transferred to the AC line, thereby greatly increasing the transmission pressure of the AC line and causing the voltage of the AC receiving end node to drop or even voltage instability. Therefore, dynamic reactive power compensation devices need to be installed to effectively prevent voltage instability.

[0176] First, according to the first step, the AC line L1-L4 power flow transfer factor of the UHV DC power is obtained, and the results are shown in Table 2. Then, according to step two, 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. According to the research, the dynamic reactive power compensation device is not connected to the receiving end node of line L1-L4, so the voltage weak node comprehensive evaluation index is equal to the line load rate index according to formula (7). The line set with voltage weak node comprehensive evaluation index greater than 0.7 is {L1, L2, L3}, so the voltage stability weak node set R = {1, 2, 3} is determined.

[0177] Table 2 AC line power flow transfer factor of UHV DC line

[0178]

[0179] Table 3 AC line load rate λ k

[0180]

[0181] According to step three, 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 partition is performed. For the receiving end grid nodes, the average electrical distance D of each node from the weak nodes is calculated, and the five nodes with the smallest D value {1, 2, 3, 6, 7} are selected as the candidate installation nodes of the reactive power compensation device.

[0182] Based on step four, taking a phase modifier as an example, the sensitivity of the weak node voltage to the reactive power of the candidate node is obtained by time domain simulation as shown in Table 4. Using the optimal particle swarm algorithm, the optimal configuration scheme of the grid reactive power compensation device is obtained as shown in Table 5.

[0183] Table 4 Sensitivity of weak node voltage to reactive power of alternative node

[0184]

[0185] Table 5 Optimal configuration scheme of reactive power compensation

[0186]

[0187] The simulation verification is performed on the calculation results by using the PSASP time domain simulation program developed by the China Electric Power Research Institute. According to the proposed reactive power scheme before and after the configuration, after the occurrence of DC bipolar blocking, the steady-state voltage of each node is shown in Table 6. It is found by comparison that after the configuration of reactive power compensation, the voltage of each voltage weak node is obviously improved, and the steady-state voltage of the weak node can be restored to more than 0.9 p.u., which meets the operation requirements of the power grid.

[0188] Table 6 Comparison of weak node voltage before and after configuration of reactive power compensation

[0189]

[0190] Therefore, for the voltage stability problem of the receiving end power grid caused by high-voltage direct current line fault or new energy power fluctuation, an optimal configuration method of reactive power compensation equipment of the receiving end power grid considering power flow transfer after fault is proposed. The weak node set of voltage stability of the receiving end power grid is selected by calculating the power flow transfer factor, the line load rate and the comprehensive evaluation index of voltage weak node. Combined with the proposed electrical distance index, the optimal configuration scheme of reactive power compensation device of the receiving end power grid is proposed, which provides reactive voltage support for the receiving end power grid, effectively solves the voltage instability risk of the important AC transmission channel of the receiving end power grid after the DC fault or the new energy power fluctuation, and is beneficial to improve the high-voltage direct current and new energy consumption capacity of the receiving end power grid, and ensures the safe and stable operation of the receiving end power grid.

[0191] Optionally, when the high-voltage direct current or new energy power in the receiving end power grid changes, the power flow transfer factor of the receiving end power grid is calculated, including:

[0192] For the receiving end power grid fed by the ultra-high voltage direct current, the ultra-high voltage direct current is equivalent to a power source at the feeding point. When the high-voltage direct current or new energy power in the receiving end power grid changes, assuming that the DC feeding point or the new energy grid connection point is node i, when the active power injection power of node i changes ΔP i , the active power change amount of the internal branch k of the receiving end power grid is , then there is a relationship:

[0193]

[0194] In the formula, G k-i is the power flow transfer factor of the line k to the node i;

[0195] Based on the relationship formula, G k-i The expression is derived according to the quick decomposition method of the power flow calculation formula, and has:

[0196]

[0197] Where, ΔP is the node injection power change column vector, Δθ is the voltage phase angle change column vector, B0 is the admittance matrix established by taking 1 / x as the branch parameter, and X is the inverse matrix of B0;

[0198] According to formula (2), after the active power injection of node i changes, the power change amount caused by the branch k, assuming that the two end node numbers are m and n, is

[0199]

[0200] The power flow transfer factor G k-i The expression is

[0201]

[0202] Optionally, based on the power flow transfer factor of the receiving end power grid, a comprehensive evaluation index of a voltage weak node is calculated, and a voltage stability weak node set is determined based on the comprehensive evaluation index, including:

[0203] For the expected fault of the receiving end power grid, based on the power flow transfer factor of the receiving end power grid, the power flow change amount of each line of the key section is calculated, and the line load rate index is calculated according to formula (5):

[0204]

[0205] Where, 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;

[0206] Considering the sensitivity of the node voltage to the dynamic compensation device reactive power output and the reactive power output capability of the compensation device, the dynamic reactive power compensation capability index γ k of the receiving end node of line k is formulated:

[0207]

[0208] Where, ΔQ k is the reactive power change amount of the dynamic reactive power compensation device at the receiving end node of line k, ΔU k is the voltage change amount of the corresponding receiving end node of line k, and Q k.max is the upper limit of the reactive power output of the dynamic reactive power compensation device connected to the receiving end node of line k;

[0209] Based on the line load rate index and the dynamic reactive power compensation capability index, a voltage weak node comprehensive evaluation index L is calculated k :

[0210] L k = λ k - αγ k (7)

[0211] Wherein, α is an adjustment coefficient, which can be valued according to the actual situation of the power grid;

[0212] The voltage weak node comprehensive evaluation index L is set k The threshold value is L k.max , if L k >L k.max , the receiving end node of the line k is determined as a weak node, and the voltage stability weak node set R = {i, j, …} is determined by calculating the weak node comprehensive evaluation index of all lines of the key section.

[0213] 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 the selected installation node set of the reactive power compensation device is determined for each node partition, comprising:

[0214] The electrical distance between any two different nodes in the power grid is defined, which is defined by the node impedance matrix, and has

[0215]

[0216] Let the vectors I k and I i take 1 and -1 respectively, and the rest take 0, which is equivalent to injecting positive and negative unit current at nodes k and i in the power grid respectively, and U k and U i are obtained from formula (8) respectively, then the electrical distance D k.i between nodes k and i is expressed as

[0217] D k.i = |U k -U i | = |Z kk + Z ii - 2Z ki | (9)

[0218] The maximum electrical distance index D max is defined, and the electrical distance is calculated for all nodes in the set R according to formula (9), for any node k and i, if D k.i ≤ D max , nodes k and i are classified into the same area, and the set R is divided into z subsets according to the area, denoted as R1, …, R z;

[0219] Determine the candidate installation node set of the reactive power compensation device for each node partition, define an average electrical distance calculation index D, the average distance of node k to all nodes in the weak node set R1 Indicated as

[0220]

[0221] Wherein, N R1 The number of weak nodes in R1;

[0222] For the receiving end power grid node, calculate the average electrical distance between it and the nodes in R1 one by one Select a number of nodes with the smallest average electrical distance as the candidate nodes of the reactive power compensation device of node partition R1;

[0223] Repeat the above steps until the candidate nodes of the reactive power compensation device of each node partition are obtained.

[0224] Optionally, through simulation, calculate the sensitivity of weak node voltage to the candidate node of the reactive power compensation device, determine the installation location and capacity of the reactive power compensation device based on the optimal particle swarm algorithm, including:

[0225] Set the reactive power compensation device at the candidate installation node j, and the rated capacity is S N.j Through time domain simulation, analyze the voltage support effect of the reactive power compensation device at different locations on the weak node i after fault, and determine the voltage support effect of different types of reactive power compensation devices on the node voltage by establishing the sensitivity index μ ij

[0226]

[0227] Wherein, ΔU i The change of steady-state voltage of node i after fault after installing the reactive power compensation device;

[0228] According to the device cost and the penalty function of the voltage exceeding the constraint condition of different nodes, determine the objective function of the optimal particle swarm algorithm:

[0229] minf=∑C k +p(U) (12)

[0230] Wherein, ∑C k The total device cost of the reactive power compensation device in the configuration scheme, and p(U) is the penalty function caused by the over-limit of each node voltage;

[0231] The constraint condition of the optimal particle swarm algorithm is that the steady-state voltage of each weak node under the typical fault set can be restored to the allowable range:

[0232] U​i.min ≤U i ≤U i.max (13)

[0233] An optimal particle swarm algorithm is used to solve the reactive power configuration scheme, wherein each particle represents a reactive power compensation device configuration scheme, and the function expression of different particles and their velocities is:

[0234]

[0235] wherein, α i.j is the reactive power compensation capacity at the alternative node j in the scheme i, v i.j is the change speed of α i.j ;

[0236] Through the optimal particle swarm iterative calculation, the global optimal particle obtained is used as the optimal configuration location and capacity of the reactive power compensation device of the receiving end power grid.

[0237] According to another aspect of the present application, a reactive power compensation device optimal configuration system 400 of a receiving end power grid considering power flow transfer is also provided, as shown in Figure 4 , the system 400 comprises:

[0238] A power flow transfer factor calculation module 410 is configured 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.

[0239] A voltage stability weak node set determination module 420 is configured 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.

[0240] An alternative installation node set determination module 430 is configured to calculate an electrical distance index for the voltage stability weak node set, partition the nodes in the voltage stability weak node set based on the comprehensive evaluation index, and determine an alternative installation node set of the reactive power compensation device for each node partition.

[0241] An installation location and capacity determination module 440 is configured to calculate the sensitivity of the weak node voltage to the alternative node of the reactive power compensation device through simulation, and determine the installation location and capacity of the reactive power compensation device based on an optimal particle swarm algorithm.

[0242] Optionally, the power flow transfer factor calculation module comprises:

[0243] A power flow transfer factor calculation submodule is configured to, for a receiving end power grid with ultra-high voltage direct current feeding, equivalent the ultra-high voltage direct current to a power source at the feeding point, assume that the direct current feeding point or the new energy grid-connected point is node i, when the active power injection power of node i changes ΔP iThe active power variation on the internal branch k of the receiving end power grid will be caused by The relationship is:

[0244]

[0245] In the formula, G k-i is the power flow transfer factor of the line k to the node i;

[0246] Based on the relationship, G k-i is derived from the expression, according to the fast decomposition method power flow calculation formula, and has:

[0247]

[0248] Where, ΔP is the node injection power change column vector, Δθ is the voltage phase angle change column vector, B0 is the admittance matrix established by taking 1 / x as the branch parameter, and X is the inverse matrix of B0;

[0249] According to formula (2), after the active injection change of the node i, the power variation caused by the branch k is

[0250]

[0251] The power flow transfer factor G k-i of the receiving end power grid is

[0252]

[0253] Optionally, the weak node set voltage stability determination module comprises:

[0254] The line load rate index sub-module is used to calculate the power flow variation of each line of the key section according to the power flow transfer factor of the receiving end power grid, and the line load rate index is calculated according to formula (5):

[0255]

[0256] Where, λ k is the load rate index of the line k after the fault, P k and P k.N are the steady-state power and rated power of the line k after the fault, respectively;

[0257] The dynamic reactive power compensation capability index sub-module is used to comprehensively consider the sensitivity of the node voltage to the dynamic compensation device reactive power output and the reactive power output capability of the compensation device, and to formulate the dynamic reactive power compensation capability index γk of the receiving end node of the line k:

[0258]

[0259] wherein, AQ k is the reactive power variation of the dynamic reactive power compensation device at the receiving end node of line k, AU k is the corresponding voltage variation of the receiving end node of line k, Q k.max is the upper limit of the reactive power output of the dynamic reactive power compensation device connected to the receiving end node of line k;

[0260] The voltage weak node comprehensive evaluation index calculation submodule is configured to calculate a voltage weak node comprehensive evaluation index L k based on the line load rate index and the dynamic reactive power compensation capability index.

[0261] L k = λ k - αγ k (7)

[0262] wherein, α is an adjustment coefficient, which can be determined according to the actual situation of the power grid;

[0263] The voltage stability weak node set determination submodule is configured to set a voltage weak node comprehensive evaluation index L k threshold value as L k.max , if L k > L k.max , it is determined that the receiving end node of line k is a weak node, and the voltage stability weak node set R = {i, j, …} is determined by calculating the weak node comprehensive evaluation index of all lines of the key section.

[0264] Optionally, the candidate installation node set determination module comprises:

[0265] The electrical distance determination submodule is configured to define the electrical distance between any two different nodes in the power grid, which is defined by the node impedance matrix, and has

[0266]

[0267] Let the vector I take 1 and -1 respectively at I k and I i , and take 0 for the rest, which is equivalent to injecting positive and negative unit currents at nodes k and i in the power grid respectively, and U k and U i are obtained respectively by formula (8), then the electrical distance D k.i between nodes k and i is represented as

[0268] D k.i = |U k - U i | = |Z kk + Z ii - 2Z ki | (9)

[0269] The voltage stability weak node set division sub-module is configured to define a maximum electrical distance index D max For all nodes in the voltage stability weak node set R, the electrical distance is calculated according to formula (9) two by two, and for any node k and i, if D k.i ≤D max , the node k and i are divided into the same region, and the voltage stability weak node set R is divided into z sub-sets according to the region, denoted as R1, …, R z ;

[0270] The node average distance determination sub-module is configured to determine the candidate installation node set of the reactive power compensation device for each node partition, define an average electrical distance calculation index D, and the average distance of the node k to all nodes in the weak node set R1 is expressed as

[0271]

[0272] wherein N R1 is the number of weak nodes in R1;

[0273] The candidate node of the reactive power compensation device determination sub-module is configured to calculate the average electrical distance of each node in the receiving end power grid to the nodes in R1 The nodes with the minimum average electrical distance are selected as the candidate nodes of the reactive power compensation device of the node partition R1.

[0274] The above steps are repeated until the candidate nodes of the reactive power compensation device of each node partition are obtained.

[0275] Optionally, the installation site and capacity determination module comprises:

[0276] The sensitivity index establishment sub-module is configured to set the reactive power compensation device at the candidate installation node j with a rated capacity S N.j , analyze the voltage support effect of the reactive power compensation device at different sites on the voltage weak node i after a fault through time domain simulation, determine the voltage support effect of different types of reactive power compensation devices on the node voltage through the establishment of a sensitivity index μ ij

[0277]

[0278] wherein ΔU i is the change of the steady-state voltage of the node i after a fault after the installation of the reactive power compensation device;

[0279] The objective function determination sub-module is configured to determine the objective function of the optimal particle swarm algorithm according to the device cost and the penalty function of the voltage exceeding the constraint condition of different nodes:

[0280] minf=∑C​k + p(U) (12)

[0281] wherein ∑C k is the total equipment cost of reactive power compensation devices in the configuration scheme, and p(U) is a penalty function caused by voltage out-of-limit of each node;

[0282] The determining constraint condition submodule is configured to determine the constraint condition of the optimal particle swarm algorithm as the steady-state voltage of each voltage weak node under the typical fault set being able to recover to the allowable range:

[0283] U i.min ≤ U i ≤ U i.max (13)

[0284] The determining different particles and their velocities submodule is configured to solve the reactive power configuration scheme by using the optimal particle swarm algorithm, wherein each particle represents a reactive power compensation device configuration scheme, and a function expression of different particles and their velocities is:

[0285]

[0286] wherein α i.j is the reactive power compensation capacity of the alternative node j in the scheme i, v i.j is the change speed of α i.j ;

[0287] The determining optimal configuration location and capacity submodule is configured to obtain the global optimal particle by optimal particle swarm iterative calculation, and the global optimal particle is used as the optimal configuration location and capacity of the reactive power compensation device of the receiving end power grid.

[0288] An embodiment of the power flow transfer considering receiving end power grid reactive power compensation device optimization configuration system 400 of the application corresponds to another embodiment of the power flow transfer considering receiving end power grid reactive power compensation device optimization configuration method 100 of the application, and thus will not be described here.

[0289] According to another aspect of the application, a computer readable storage medium having a computer program stored thereon is also provided, and the program is executed by a processor to implement the steps of the method according to any one of the above embodiments.

[0290] According to another aspect of the application, an electronic device is also provided, which includes a computer readable storage medium and one or more processors configured to execute a program in the computer readable storage medium.

[0291] Those skilled in the art will appreciate that embodiments of the application can be devised for a method, a system, or a computer program product. Accordingly, the present application can be embodied in the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code. Embodiments of the present application can be implemented with various computer program languages such as the object-oriented programming language Java and the interpreted scripting language JavaScript, etc.

[0292] The present application is described in reference to the flowchart illustrations and / or block diagrams according to the embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0293] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0294] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0295] While the preferred embodiments of the application have been described, additional variations and modifications can be made to the embodiments by those skilled in the art once they learn of the basic inventive concepts. Therefore, the appended claims are intended to cover all such variations and modifications as fall within the scope of the application.

[0296] Obviously, numerous modifications and variations of the present application are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A method for optimizing the configuration of reactive power compensation equipment in a receiving-end power grid considering power flow transfer, characterized in that, include: When the power of high-voltage DC or new energy sources in the receiving-end power grid changes, calculate the power flow transfer factor of the receiving-end power grid. Based on the power flow transfer factor of the receiving-end power grid, a comprehensive evaluation index for voltage-weak nodes is calculated, and a set of voltage-stability-weak nodes is determined based on the comprehensive evaluation index. For the set of weak nodes with voltage instability, the nodes in the set of weak nodes with voltage instability are divided into zones by calculating the electrical distance index, and the set of candidate installation nodes for reactive power compensation equipment is determined for each node zone. Through simulation, the sensitivity of the voltage of weak nodes to the candidate nodes of the reactive power compensation device is calculated, and the installation location and capacity of the reactive power compensation device are determined based on the optimal particle swarm optimization algorithm. Based on the power flow transfer factor of the receiving-end power grid, a comprehensive evaluation index for voltage-weak nodes is calculated. Based on the comprehensive evaluation index, a set of voltage-stability-weak nodes is determined, including: For anticipated faults in the receiving-end power grid, based on the power flow transfer factor of the receiving-end 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 equation (1): Where, λ k G represents the load factor of line k after a fault. k-i That is, the power flow transfer factor of line k to node i, ΔP i Let P be the change in injected power at node i. k and P k.N These 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, as well as the reactive power output capability of the compensation equipment, a dynamic reactive power compensation capability index γ for the receiving-end node k of line is formulated. k : Where, ΔQ k Let ΔU be the reactive power change of the dynamic reactive power compensation equipment at the receiving end node of line k. k Q represents the voltage change at the corresponding receiving node k of the line. k.max The upper limit of reactive power output of the dynamic reactive power compensation equipment connected to the receiving node of line k; Based on the aforementioned line load rate index and dynamic reactive power compensation capability index, the comprehensive evaluation index L for voltage-weak nodes is calculated. k : L k =λ k -ag k (3) Wherein, α is the adjustment coefficient, which can be selected according to the actual situation of the power grid; Set a comprehensive evaluation index L for voltage weak points k The threshold value is L k.max If L k >L k.max If the receiving end node of line k is determined to be a weak node, the set of weak nodes for voltage stability R = {i,j,…} is determined by calculating the comprehensive evaluation index of weak nodes for all lines in the key section, where i and j are the weak node numbers.

2. The method according to claim 1, characterized in that, When the power output of high-voltage DC or new energy sources in the receiving-end power grid changes, the power flow transfer factor of the receiving-end power grid is calculated, including: For a receiving-end grid fed by UHVDC, the UHVDC is equivalent to a power source at the feeding point. When the power of the UHVDC or renewable energy source in the receiving-end grid changes, assuming the DC feeding point or renewable energy source grid connection point is node i, when the active power injection at node i changes by ΔP... i The change in active power on branch k within the receiving-end power grid will be as follows: Then we have the following relation: In the formula, G k-i That is, the power flow transfer factor of line k to node i; Based on the aforementioned relationship, G k-i The expression is derived from the power flow calculation formula of the fast decomposition method: Where ΔP is the column vector of nodal injected power change, Δθ is the column vector of voltage phase angle change, B0 is the susceptance matrix established using 1 / x as branch parameters, and X is the inverse matrix of B0. From equation (5), after the active power injection at node i changes, the resulting power change on branch k, assuming the node numbers at both ends are m and n respectively, is: Power flow transfer factor G of the receiving-end power grid k-i The expression is Among them, X mi Let X be the value corresponding to the m-th row and i-th column of matrix X. ni Let x be the value corresponding to the nth row and ith column of matrix X. k Let K be the reactance value of line k.

3. The method according to claim 1, characterized in that, For the set of weak nodes with unstable voltage, the nodes in the set are divided into zones by calculating the electrical distance index. For each zone, a set of candidate installation nodes for reactive power compensation equipment is determined, including: The electrical distance between any two distinct nodes in a power grid is defined by the node impedance matrix Z, and we have: In the formula, n is the total number of power grid nodes. Assuming i and j are any integers from 1 to n, then U i Let I be the voltage value at node i. i Z is the injected current at node i. ij This refers to the element in the i-th row and j-th column of the nodal impedance matrix Z; Let vector I contain I k and I i Taking values ​​of 1 and -1 respectively, and 0 for the rest, is equivalent to injecting positive and negative unit currents at nodes k and i in the power grid, respectively. U is obtained from equation (8). k and U i Then the electrical distance D between node k and i k.i Represented as D k.i =|U k -U i |=|Z kk +Z ii -2Z ki | (9) Among them, U k and U i Let Uk and Ui be the voltages at nodes k and i, respectively. Define the maximum electrical distance index D max For all nodes in set R, the electrical distance is calculated pairwise using equation (9). For any nodes k and i, if D k.i ≤D max Then, nodes k and i are grouped into the same region, and set R is divided into z subsets according to the regions, denoted as R1, ..., R2. z ; For each node partition, a set of candidate installation nodes for reactive power compensation equipment is determined, 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. Represented as Where, N R1 Let R1 be the number of weak nodes in R1, where R1 is the number of subsets into which set R is divided according to regions, denoted as R1, ..., Rz. z The weak nodes in the first region form set R1; For each receiving-end grid node, calculate its average electrical distance to the nodes in R1. Several nodes with the smallest average electrical distance were selected as candidate nodes for the reactive power compensation device in node partition R1. Repeat the above steps until candidate nodes for reactive power compensation devices in each node partition are obtained.

4. The method according to claim 1, characterized in that, Through simulation, the sensitivity of weak node voltage to candidate nodes of the reactive power compensation device is calculated. Based on the optimal particle swarm optimization algorithm, the installation location and capacity of the reactive power compensation device are determined, including: Reactive power compensation devices with a rated capacity of S are installed at each of the alternative installation nodes j. N.j Through time-domain simulation, the voltage support effect of reactive power compensation devices at different locations on voltage-weak node i after a fault is analyzed, and a sensitivity index μ is established. ij To determine the effectiveness of different types of reactive power compensation devices in supporting node voltage: Wherein, ΔU i The change in steady-state voltage at node i after a fault following the installation of the reactive power compensation device; The objective function of the optimal particle swarm optimization algorithm is determined based on equipment cost and the penalty function for different node voltages exceeding the constraints. Where, ∑C k Let p(U) be the total equipment cost of the reactive power compensation device in the configuration scheme, and p(U) be the penalty function caused by voltage exceeding the limit at each node. The constraint for determining the optimal particle swarm optimization algorithm is that the steady-state voltage of each voltage-weak node in a typical fault set can be restored to an allowable range. IN i.min ≤U i ≤U i.max (13) The optimal particle swarm optimization algorithm is used to solve the reactive power allocation scheme, where each particle represents a reactive power compensation device configuration scheme, and the functional expressions for different particles and their velocities are as follows: Where, α i.j v represents the reactive power compensation capacity at candidate node j in scheme i. i.j For α i.j The rate of change; The globally optimal particle obtained through optimal particle swarm optimization is used as the optimal location and capacity for reactive power compensation devices in the receiving-end power grid.

5. A system for optimizing the configuration of reactive power compensation equipment in a receiving-end power grid considering power flow transfer, characterized in that, include: The power flow transfer factor calculation module is used to calculate the power flow transfer factor of the receiving-end power grid when the high-voltage DC or new energy power in the receiving-end power grid changes. The module for determining the voltage stability weak node set is used to calculate the comprehensive evaluation index of the voltage weak node based on the power flow transfer factor of the receiving-end power grid, and determine the voltage stability weak node set based on the comprehensive evaluation index; The module for determining the alternative installation node set is used to divide the nodes in the voltage instability weak node set into zones by calculating the electrical distance index, and to determine the alternative installation node set for reactive power compensation equipment for each node zone. The module for determining the installation location and capacity is used to calculate the sensitivity of the voltage at weak nodes to the candidate nodes of the reactive power compensation device through simulation, and to determine the installation location and capacity of the reactive power compensation device based on the optimal particle swarm optimization algorithm. The module for identifying weak points in voltage stability includes: The submodule for obtaining the line load rate index 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-end power grid in response to anticipated faults, and to obtain the line load rate index according to formula (1): Where, λ k G represents the load factor of line k after a fault. k-i That is, the power flow transfer factor of line k to node i, ΔP i Let P be the change in injected power at node i. k and P k.N These are the steady-state power and rated power of line k after the fault, respectively; A submodule for defining dynamic reactive power compensation capability indicators is developed to comprehensively consider the sensitivity of node voltage to the reactive power output of dynamic compensation equipment, as well as the reactive power output capability of the compensation equipment, and to formulate the dynamic reactive power compensation capability indicator γ for the receiving-end node of line k. k : Where, ΔQ k Let ΔU be the reactive power change of the dynamic reactive power compensation equipment at the receiving end node of line k. k Q represents the voltage change at the corresponding receiving node k of the line. k.max The upper limit of reactive power output of the dynamic reactive power compensation equipment connected to the receiving node of line k; The submodule for calculating the comprehensive evaluation index of voltage weak nodes is used to calculate the comprehensive evaluation index L of voltage weak nodes based on the line load rate index and the dynamic reactive power compensation capability index. k : L k =λ k -ag k (3) Wherein, α is the adjustment coefficient, which can be selected according to the actual situation of the power grid; The module for identifying voltage stability weak nodes is used to set the comprehensive evaluation index L for voltage stability weak nodes. k The threshold value is L k.max If L k >L k.max If the receiving end node of line k is determined to be a weak node, the set of weak nodes for voltage stability R = {i,j,…} is determined by calculating the comprehensive evaluation index of weak nodes for all lines in the key section, where i and j are the weak node numbers.

6. The system according to claim 5, characterized in that, The module for calculating the power flow transfer factor includes: The power flow transfer factor calculation submodule is used to treat the UHVDC feed-in grid as an equivalent power source at the feed-in point. When the power of the UHVDC or renewable energy source in the receiving-end grid changes, assuming the DC feed-in point or renewable energy source grid connection point is node i, the active power injection at node i changes by ΔP. i The change in active power on branch k within the receiving-end power grid will be as follows: Then we have the following relation: In the formula, G k-i That is, the power flow transfer factor of line k to node i; Based on the aforementioned relationship, G k-i The expression is derived from the power flow calculation formula of the fast decomposition method: Where ΔP is the column vector of nodal injected power change, Δθ is the column vector of voltage phase angle change, B0 is the susceptance matrix established using 1 / x as branch parameters, and X is the inverse matrix of B0. From equation (5), after the active power injection at node i changes, the resulting power change on branch k, assuming the node numbers at both ends are m and n respectively, is: Power flow transfer factor G of the receiving-end power grid k-i The expression is Among them, X mi Let X be the value corresponding to the m-th row and i-th column of matrix X. ni Let x be the value corresponding to the nth row and ith column of matrix X. k Let K be the reactance value of line k.

7. The system according to claim 5, characterized in that, The alternative installation node set modules were identified, including: The electrical distance determination submodule is used to define the electrical distance between any two different nodes in the power grid, defined by the node impedance matrix Z. In the formula, n is the total number of power grid nodes. Assuming i and j are any integers from 1 to n, then U i Let I be the voltage value at node i. i Z is the injected current at node i. ij This refers to the element in the i-th row and j-th column of the nodal impedance matrix Z; Let vector I contain I k and I i Taking values ​​of 1 and -1 respectively, and 0 for the rest, is equivalent to injecting positive and negative unit currents at nodes k and i in the power grid, respectively. U is obtained from equation (8). k and U i Then the electrical distance D between node k and i k.i Represented as D k.i =|U k -U i |=|Z kk +Z ii -2Z ki | (9) Among them, U k and U i Voltages U at nodes k and i are respectively k and U i ; The voltage stability weak node set is divided into sub-modules 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 using equation (9). For any nodes k and i, if D k.i ≤D max Then, nodes k and i are grouped into the same region, and the set of weak voltage-stability nodes R is divided into z subsets according to the region, denoted as R1, ..., R2. z ; The submodule for determining the average node distance is used to identify the candidate installation node set for reactive power compensation equipment for each node partition. It defines an average electrical distance calculation index D, which is the average distance from node k to all nodes in the weak node set R1. Represented as Where, N R1 Let R1 be the number of weak nodes in R1, where R1 is the number of subsets into which set R is divided according to regions, denoted as R1, ..., Rz. z The weak nodes in the first region form set R1; The module for identifying candidate nodes for reactive power compensation devices is used to calculate the average electrical distance between each receiving-end grid node and the nodes in R1. Several nodes with the smallest average electrical distance were selected as candidate nodes for the reactive power compensation device in node partition R1. Repeat the above steps until candidate nodes for reactive power compensation devices in each node partition are obtained.

8. The system according to claim 5, characterized in that, Determining the installation location and capacity module includes: A sensitivity index submodule is established to install reactive power compensation devices at each of the 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 voltage-weak node i after a fault is analyzed, and a sensitivity index μ is established. ij To determine the effectiveness of different types of reactive power compensation devices in supporting node voltage: Wherein, ΔU i The change in steady-state voltage at node i after a fault following the installation of the reactive power compensation device; The objective function determination submodule is used to determine the objective function of the optimal particle swarm optimization algorithm based on equipment cost and penalty functions for different node voltages exceeding constraints. minf=∑C k +p(U) (12) Where, ∑C k Let p(U) be the total equipment cost of the reactive power compensation device in the configuration scheme, and p(U) be the penalty function caused by voltage exceeding the limit at each node. The constraint determination submodule is used to determine the constraints of the optimal particle swarm optimization 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) Different particle and velocity submodules are identified for solving reactive power allocation schemes using the optimal particle swarm optimization algorithm. Each particle represents a reactive power compensation device configuration scheme, and the functional expressions for different particles and their velocities are as follows: Where, α i.j v represents the reactive power compensation capacity at candidate node j in scheme i. i.j For α i.j The rate of change; The optimal configuration location and capacity submodule is used to determine the global optimal particle obtained through optimal particle swarm iteration calculation, which serves as the optimal configuration location and capacity of the reactive power compensation device in the receiving-end power grid.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the method as described in any one of claims 1-4.

10. An electronic device, characterized in that, include: The computer-readable storage medium as described in claim 9; as well as One or more processors for executing a program in the computer-readable storage medium.

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