CN-121980835-A - Method and system for improving short circuit calculation convergence of new energy access power system

CN121980835ACN 121980835 ACN121980835 ACN 121980835ACN-121980835-A

Abstract

The invention provides a method and a system for improving short circuit calculation convergence of a new energy access power system, wherein the method comprises the steps of aggregating new energy values in a new energy station accessed by the power system to generate a first new energy equivalent model and a second new energy equivalent model; the method comprises the steps of performing initial short-circuit calculation to determine initial voltages of all nodes of the power system when output of a second new energy equivalent model is not considered, dividing the power system into a near fault zone and a far fault zone according to the initial voltages after short-circuit faults occur, regarding the second new energy equivalent model of the far fault zone as an open circuit, regarding the second new energy equivalent model of the near fault zone as a voltage-controlled current source model, and performing short-circuit iterative calculation to determine the short-circuit convergence of the system. The method and the system effectively solve the problem that convergence and precision of short circuit calculation cannot be considered when new energy is accessed, and lay a foundation for relay protection setting calculation and protection correct actions of the novel power system.

Inventors

WEI MINGJIE
ZHANG ZHI
WANG XIAOYANG
ZHOU JINHONG
YU YUE
YANG GUOSHENG
WANG CONGBO
LI YONG
GAO CHENGUANG
LV PENGFEI
WANG HUI
LI ZHONGQING

Assignees

中国电力科学研究院有限公司

Dates

Publication Date: 20260505
Application Date: 20260409

Claims (10)

1. A method for improving convergence of short circuit calculation of a new energy access power system, the method comprising: For a new energy unit with the same control strategy in a new energy station accessed by the power system, performing aggregation equivalence according to the grid-connected capacity of the new energy unit, and generating a first new energy equivalence model; aggregating and equating a first new energy equivalent model which has different control strategies and is connected with a public node, and generating a second new energy equivalent model; When the output of the second new energy equivalent model is not considered, initial short circuit calculation is carried out, and initial voltages of all nodes of the power system are determined; After a short-circuit fault occurs, dividing the power system into a near fault zone and a far fault zone according to the initial voltage; regarding the second new energy equivalent model of the fault far zone as an open circuit, regarding the second new energy equivalent model of the fault near zone as a voltage-controlled current source model, performing short circuit iterative computation, and determining fault components of all node voltages in each iteration; And when the iteration times are not more than the set iteration limit times and the fault components of all node voltages meet the set iteration convergence criterion, ending the short circuit iteration calculation.
2. The method of claim 1, wherein aggregating equivalence based on grid-tie capacity of the new energy unit, generating the first new energy equivalence model is generating the first new energy equivalence model based on grid-tie capacity of the new energy unit by weighted multiplication equivalence, wherein: the output current and the terminal voltage of the first new energy equivalent model are expressed as: In the formula, Positive sequence is represented when +is taken, negative sequence is represented when-is taken, Representing the number of new energy units with the same control strategy in the new energy station; And Representing the first place of new energy station Of individual units Sequence current The terminal voltage of the sequencer is per unit value; And Respectively represent the equivalent models of the first new energy source Sequence current A sequencer terminal voltage; regarding the output currents of all new energy units with the same control strategy in the new energy station as the same phase, the relation between the output current of the first new energy equivalent model and the terminal voltage is as follows: In the formula, Representing the output of the first new energy equivalent model Sequence current concerns Function of sequencer terminal voltage.
3. The method of claim 2, wherein aggregating and equating a first new energy equivalence model having different control strategies and being connected to a common node to generate a second new energy equivalence model, comprises: setting public node accessed by first new energy equivalent model with different control strategies Sequencer terminal voltage The sequence currents are respectively And And (2) and , wherein, Is that Sequence voltage amplitude; Order the Each common node is determined by an iterative method by coherently taking per unit value in the (0, 1) range The output current corresponding to the sequence voltage is calculated, wherein the expression of the output current is as follows: In the formula, Representing the number of first new energy equivalent models with different control strategies; representing an aggregate area of the common node An order node admittance matrix; 、 And A first new energy equivalent model respectively representing the j-th control strategy in the aggregation area of the common node Sequentially outputting current, Sequencer terminal voltage a function of the relationship between the two; According to each of the common nodes The voltage of the sequencer terminal and the corresponding output current are subjected to aggregation equivalence to generate a second new energy source equivalence model The order model, wherein, the output characteristic expression of the second new energy equivalent model is: In the formula, Representing a first new energy equivalence model aggregated to a common node The sequence output current relates to Function of sequencer terminal voltage.
4. The method of claim 1, wherein after the occurrence of the short-circuit fault, dividing the power system into a near fault zone and a far fault zone according to the initial voltage comprises: Dividing the area where the node with the initial voltage not smaller than the set voltage per unit value threshold is located into a fault far area, and dividing the area where the node with the initial voltage smaller than the set voltage per unit value threshold is located into a fault near area.
5. The method of claim 1, wherein considering the second new energy equivalence model of the far-fault zone as an open circuit and the second new energy equivalence model of the near-fault zone as a voltage-controlled current source model, performing a short circuit iterative calculation, determining fault components of all node voltages in each iteration, comprises: and calculating fault components of positive sequence, negative sequence and zero sequence voltages of all nodes in the t-th iteration, wherein the fault components have the following expression: Wherein, the N is the set iteration limit number, 、 And Respectively representing positive sequence, negative sequence and zero sequence node admittance matrixes of the power system; 、 And The positive sequence current, the negative sequence current and the zero sequence current which are injected by all nodes in the t-th iteration respectively comprise three types of nodes including a new energy node, a fault node and other nodes, wherein when t=1, the positive sequence current which is injected by the new energy node is the rated current of the node which is connected with the new energy, the negative sequence current and the zero sequence current which are injected by the new energy node are all 0, and the positive sequence, the negative sequence and the zero sequence current which are injected by the fault node are fault node currents which are obtained by short circuit calculation without considering the connection of the new energy; 、 And Respectively representing fault component matrixes of positive sequence, negative sequence and zero sequence voltages of all nodes calculated in the t-th iteration; calculating positive sequence, negative sequence and zero sequence voltage matrixes of all nodes after t-th iteration correction, wherein the expression is as follows: In the formula, 、 And Respectively representing positive sequence, negative sequence and zero sequence voltage matrix of all nodes after the t-th iteration correction, The positive sequence voltage matrix is used for all nodes in a normal running state before a fault occurs; according to the output characteristics of the second new energy equivalent model, updating the positive sequence, the negative sequence and the zero sequence current injected by the new energy node in the t+1th iteration through the positive sequence, the negative sequence and the zero sequence voltage of the new energy node extracted from all node positive sequence, negative sequence and zero sequence voltage matrixes after the t iteration correction; updating positive sequence, negative sequence and zero sequence current injected by the fault node in the t+1th iteration according to the positive sequence, negative sequence and zero sequence voltage of the fault node extracted from the positive sequence, negative sequence and zero sequence voltage matrix of each node after the t iteration correction, wherein the expression is as follows: In the formula, Respectively representing positive sequence, negative sequence and zero sequence voltage of fault node after t-th iteration correction, and respectively taking the values from the matrix 、 And A failed node in (a); Positive sequence, negative sequence and zero sequence currents injected by the fault node in the t+1st iteration are respectively represented; representing a function of solving the sequence current according to boundary conditions, sequence voltage and system impedance in short circuit calculation; and forming positive sequence, negative sequence and zero sequence current matrixes injected by each node in the t+1th iteration according to the positive sequence, negative sequence and zero sequence currents injected by the new energy node in the t+1th iteration and the positive sequence, negative sequence and zero sequence currents injected by the fault node.
6. The method of claim 5, wherein the short-circuit iterative computation ends when the iteration number is not greater than a set iteration limit number and the fault components of all node voltages satisfy a set iteration convergence criterion, wherein the iteration convergence criterion is expressed as: wherein, when t=1, A matrix with all elements being 0; Representing the maximum deviation of the fault components of the node voltages determined by two adjacent iterative calculations.
7. The method of claim 1, further comprising re-performing short-circuit iterative computation by considering a second new energy equivalence model of the near-fault zone as a linear model when the number of iterations is greater than a set iteration limit number and fault components of all node voltages do not meet a set iteration convergence criterion.
8. A system for improving convergence of short circuit calculation of a new energy access power system, the system comprising: The first model unit is used for carrying out aggregation equivalence on new energy units with the same control strategy in a new energy station accessed by the power system according to the grid-connected capacity of the new energy units to generate a first new energy equivalence model; The second model unit is used for carrying out aggregation equivalence on the first new energy equivalent model which has different control strategies and is connected with a common node, and generating a second new energy equivalent model; the initial voltage unit is used for carrying out initial short circuit calculation when the output of the second new energy equivalent model is not considered, and determining the initial voltage of all nodes of the power system; The area dividing unit is used for dividing the power system into a fault near area and a fault far area according to the initial voltage after the short circuit fault occurs; The iteration calculation unit is used for regarding the second new energy equivalent model of the fault far zone as an open circuit, regarding the second new energy equivalent model of the fault near zone as a voltage-controlled current source model, performing short circuit iteration calculation, and determining fault components of all node voltages in each iteration; And the iteration ending unit is used for ending the short circuit iteration calculation when the iteration times are not more than the set iteration limit times and the fault components of all node voltages meet the set iteration convergence criterion.
9. A computer readable storage medium, on which a computer program is stored, characterized in that the program, when being executed by a processor, implements the steps of the method according to any of claims 1-7.
10. An electronic device, comprising: A processor; A memory for storing the processor-executable instructions; the processor being configured to read the executable instructions from the memory and execute the executable instructions to implement the steps of the method of any of the preceding claims 1-7.

Description

Method and system for improving short circuit calculation convergence of new energy access power system Technical Field The invention relates to the technical field of relay protection setting, in particular to a method and a system for improving short circuit calculation convergence of a new energy access power system. Background Relay protection (protection for short) is a first defense line for safe and stable operation of the power system. Is responsible for fast, reliable, sensitive and selective removal of faulty power elements and ensuring the safe operation of the power system. And judging whether the electric characteristic quantity reaches the action fixed value or not to determine the opening and closing of the circuit breaker, so that the setting of the relay protection action fixed value directly relates to the isolation performance of protection on faults. The setting calculation is a process of modeling a fault scene of the power system, calculating the distribution condition of the short-circuit current of the system after the fault, and setting a protection action fixed value. Compared with a conventional power supply, the novel power system with gradually improved new energy duty ratio shows strong controllability in the fault process, and the short circuit calculation precision cannot be ensured in the traditional mode of using linear elements such as constant current sources and the like to equate new energy, so that the main network protection setting calculation software gradually tries to adopt nonlinear models such as voltage-controlled current sources and the like to equate new energy, and short circuit calculation is realized by an iterative method. In this process, iterative convergence of the short-circuit calculation result means that all conditions such as KCL, KVL, ohm law, new energy control constraint and the like are almost satisfied at the same time, and as the number of new energy nodes increases, calculation convergence gradually decreases, and further, the situation that after the new energy access scale is slightly higher, the system is not converged and cannot obtain a short-circuit current result occurs. Disclosure of Invention In order to solve the technical problem that the convergence of the result gradually decreases when the new energy is subjected to short-circuit calculation by adopting a nonlinear model after the new energy access scale is increased in the prior art, the invention provides a method and a system for improving the convergence of short-circuit calculation of a new energy access power system, so as to improve the calculation convergence on the premise of not reducing the short-circuit calculation precision of the power system containing the new energy. According to an aspect of the present invention, the present invention provides a method for improving convergence of short circuit calculation of a new energy access power system, the method comprising: For a new energy unit with the same control strategy in a new energy station accessed by the power system, performing aggregation equivalence according to the grid-connected capacity of the new energy unit, and generating a first new energy equivalence model; aggregating and equating a first new energy equivalent model which has different control strategies and is connected with a public node, and generating a second new energy equivalent model; When the output of the second new energy equivalent model is not considered, initial short circuit calculation is carried out, and initial voltages of all nodes of the power system are determined; After a short-circuit fault occurs, dividing the power system into a near fault zone and a far fault zone according to the initial voltage; regarding the second new energy equivalent model of the fault far zone as an open circuit, regarding the second new energy equivalent model of the fault near zone as a voltage-controlled current source model, performing short circuit iterative computation, and determining fault components of all node voltages in each iteration; And when the iteration times are not more than the set iteration limit times and the fault components of all node voltages meet the set iteration convergence criterion, ending the short circuit iteration calculation. According to another aspect of the present invention, there is provided a system for improving convergence of short circuit calculation of a new energy access power system, the system comprising: The first model unit is used for carrying out aggregation equivalence on new energy units with the same control strategy in a new energy station accessed by the power system according to the grid-connected capacity of the new energy units to generate a first new energy equivalence model; The second model unit is used for carrying out aggregation equivalence on the first new energy equivalent model which has different control strategies and is connected with a common node, and generating a second ne