CN-122026282-A - Pilot power protection method and device

CN122026282ACN 122026282 ACN122026282 ACN 122026282ACN-122026282-A

Abstract

The application relates to a longitudinal power protection method and a device, which relate to the technical field of power system protection, and the method comprises the steps of constructing a direct-current line Berhelson equivalent circuit model according to a system topological structure, and establishing a voltage and current deduction matrix from a measuring point to a reference point of each converter station; the method comprises the steps of carrying out time-frequency analysis on typical faults by adopting S transformation, comprehensively considering amplitude accumulation indexes and stability indexes to determine optimal analysis frequency, collecting voltage and current information of each converter station in real time, carrying out phase-mode transformation, carrying out deduction to a reference point through a deduction matrix, extracting voltage and current phasors under specific frequency by using a recursive DFT, calculating power phasors, constructing longitudinal power action quantity and braking quantity based on a power conservation law, establishing a longitudinal power protection criterion, and sending a tripping instruction when the criterion is met. The application can effectively identify the internal faults of the three-terminal direct current system and provides an effective protection solution for the three-terminal distributed diode rectification delivery system.

Inventors

HUANG ZIHENG
LIN XIANGNING
LI ZHENGTIAN
DING ZHIHAO
LI ZE
HUANG YINGJIE

Assignees

华中科技大学

Dates

Publication Date: 20260512
Application Date: 20251231

Claims (10)

1. A pilot power protection method, comprising: Based on a line topology structure of a three-terminal distributed diode rectification outgoing system, constructing a direct-current line Berhelon equivalent circuit model, selecting line intersection points of the direct-current line Berhelon equivalent circuit model as reference points, and constructing a voltage and current deduction matrix from each power exchange station measuring point to the reference points; s-transformation time-frequency analysis is carried out on the plurality of typical fault data, and the optimal analysis frequency is determined based on a frequency selection principle and the typical fault data after the time-frequency analysis; acquiring voltage and current information of each power exchange station measuring point of the three-terminal distributed diode rectification outgoing system in real time, uniformly deducting the voltage and current information of each power exchange station measuring point to a reference point based on the voltage and current deduction matrix, and acquiring the deduced voltage and current information; extracting the amplitude and the phase of the deduced voltage and current information under the optimal analysis frequency based on a recursive DFT algorithm to obtain voltage and current phasors, and calculating the power phasors of all converter stations based on the voltage and current phasors; And determining an action amount of the pilot power and a braking amount of the pilot power based on the power phasors of the power exchange stations, establishing a pilot power protection criterion based on the action amount of the pilot power, the braking amount of the pilot power, a set proportion braking coefficient, a reliability coefficient and a fixed action value, and controlling a protection device based on the pilot power protection criterion so as to protect the pilot power of the three-terminal distributed diode rectification and transmission system.
2. The method for protecting the pilot power according to claim 1, wherein the constructing a direct-current circuit berlong equivalent circuit model based on the circuit topology structure of the three-terminal distributed diode rectification outgoing system comprises: determining a plurality of uniform and lossy direct current transmission lines based on a line topology structure of a three-terminal distributed diode rectification outgoing system; Dividing each section of uniform lossy direct current transmission line into two parts, arranging the divided uniform lossy direct current transmission lines on two sides of a resistor and a conductive lossless line, and constructing a direct current line Berhelone equivalent circuit model based on line unit resistance, unit conductivity and line wave impedance.
3. The method for protecting the pilot power according to claim 2, wherein the step of establishing a voltage and current deduction matrix from each measurement point of the power exchange station to the reference point comprises the steps of: constructing a voltage and current deduction matrix based on line wave impedance, line resistance, line conductance, time for transmitting waves from the converter station to a reference point, delay factors, a direct-current line Berlong equivalent circuit model and a transmission line theory corresponding to each converter station; the expression of the voltage and current deduction matrix is as follows: ; Wherein, the ; ; ; ; ; In the formula, For line wave impedance, ri=rl i is line resistance, gi=gl i is line conductance, For the time that the wave passes from the converter station to the reference point, I is the delay factor and i is the respective station.
4. The method of claim 1, wherein the typical fault data is a forward intra-zone fault, a reverse extra-zone fault or a forward extra-zone fault, the S-transformed time-frequency analysis is performed on the typical fault data, and an optimal analysis frequency is determined based on a frequency selection principle and the typical fault data after the time-frequency analysis, and the method comprises the steps of; For any typical fault data, performing phase-mode transformation on the typical fault data to obtain line-mode voltage and line-mode current during fault; for any typical fault data, carrying out S-transformation time-frequency analysis on the fault time line mode voltage and the fault time line mode current based on a preset S-transformation algorithm to obtain a fault time voltage time-frequency matrix and a fault time current time-frequency matrix; Setting an analysis frequency upper limit based on a sampling theorem, and determining the number of sampling points corresponding to each period of the analysis frequency as a positive integer to obtain a candidate set of integers; For any typical fault data, respectively taking a mode of the fault time voltage time frequency matrix and the fault time current time frequency matrix to obtain a mode value voltage matrix and a mode value current matrix; For any one of the typical fault data, determining an amplitude product matrix based on the product of the modulus voltage matrix and the modulus current matrix; For any typical fault data, calculating an amplitude accumulation index and a stationarity index based on an amplitude product matrix, and determining a comprehensive index based on the amplitude accumulation index and the stationarity index; Calculating the difference between the frequency corresponding to each integer in the candidate set of integers and the frequency corresponding to the maximum comprehensive index based on the frequency corresponding to the maximum comprehensive index, and selecting the integer with the smallest difference as a target integer; and determining an optimal analysis frequency based on the target integer and the set sampling frequency.
5. The method for pilot power protection according to claim 4, wherein the preset S-transform algorithm is: ; ; ; Wherein x (k) is an input signal, namely a fault time line mode voltage and a fault time line mode current, N=2000 represents the number of sampling points of each group of input signals, m and N are integers, the m and N represent the number of rows and columns of a matrix obtained after S conversion, m satisfies a frequency mf s /N corresponding to m (N/2+1) which is more than or equal to 0 and less than or equal to N, N satisfies a sampling point time sequence corresponding to N which is more than or equal to 1, S T is a result after S conversion, a fault time voltage time frequency matrix S T(u,type) is obtained, a fault time current time frequency matrix S T(i,type) is obtained, and types are different fault types.
6. The method of claim 1, wherein the step of uniformly deducting the voltage and current information of each measurement point of the power exchange station to a reference point based on the voltage and current deduction matrix to obtain deduced voltage and current information comprises the steps of: performing phase-mode transformation on the voltage and current information of each power exchange station measurement point based on a preset phase-mode transformation formula to obtain a line mode voltage component and a line mode current component of each transformer station; Based on the voltage and current deduction matrix and a preset deduction formula, deducting the line mode voltage component and the line mode current component of each converter station measuring point to a reference point to obtain deduced voltage and current information, wherein the deduced voltage and current information comprises the line mode voltage component and the line mode current component of the reference point; The preset deduction formula is as follows: ; Wherein, the 、 The reference point is a line mode voltage component and a line mode current component respectively, T i is a voltage current deduction matrix, u li(t) is a line mode voltage component, and i li(t) is a line mode current component.
7. The method for protecting pilot power according to claim 6, wherein the recursive DFT algorithm is: ; ; ; ; Wherein N=fs/fa represents the number of sampling points of one period corresponding to the extraction optimal analysis frequency, k is an integer greater than or equal to 0, 、 The method is characterized in that the method comprises the steps of respectively obtaining a line mode voltage phasor and a line mode current phasor at a reference point, wherein K is an integer greater than or equal to 0, fs is a sampling frequency, and fa is an optimal analysis frequency.
8. The method of claim 1, wherein determining an amount of pilot power actuation and an amount of pilot power actuation based on the power phasors of each of the power converters, and establishing pilot power protection criteria based on the amount of pilot power actuation, a set proportional brake coefficient, a reliability coefficient, and an actuation constant, comprises: based on a power conservation law, calculating vector sums of power phasors of all converter stations, and taking a mode of the vector sums to obtain longitudinal power action quantity; determining a longitudinal power braking amount based on a modulus value of a power phasor of each power exchange station; Establishing a pilot power protection criterion based on pilot power action quantity, pilot power braking quantity, set proportion braking coefficient, reliability coefficient and action fixed value; The pilot power protection criterion is as follows: If the pilot power movement is greater than the product of the set proportional braking coefficient and the pilot power movement, and if the pilot power movement is greater than the product of the reliability coefficient and the movement fixed value, determining that the pilot power protection criterion is met.
9. The method for pilot power protection according to claim 8, wherein said controlling the protection device based on the pilot power protection criterion comprises: When the pilot power protection criterion is met, the protection device is controlled to trip, and a fault line is cut off; And when the pilot power protection criterion is not met, controlling the protection device to keep a non-action state.
10. A pilot power protection device, comprising: The voltage and current deduction matrix building module is used for building a direct-current line Berhelson equivalent circuit model based on a line topological structure of the three-terminal distributed diode rectification outgoing system, selecting line intersection points of the direct-current line Berhelson equivalent circuit model as reference points, and building a voltage and current deduction matrix from each power exchange station measuring point to the reference points; The optimal analysis frequency establishing module is used for carrying out S-transformation time-frequency analysis on the typical fault data and determining the optimal analysis frequency based on a frequency selection principle and the typical fault data after the time-frequency analysis; The acquisition module is used for acquiring the voltage and current information of each power exchange station measuring point of the three-terminal distributed diode rectification outgoing system in real time, and uniformly deducting the voltage and current information of each power exchange station measuring point to a reference point based on the voltage and current deduction matrix to acquire the deduced voltage and current information; The calculation module is used for extracting the amplitude and the phase of the deduced voltage and current under the optimal analysis frequency based on a recursive DFT algorithm to obtain voltage and current phasors, and calculating the power phasors of all converter stations based on the voltage and current phasors; and the protection module is used for determining the action quantity and the braking quantity of the longitudinal power based on the power phasors of the power exchange stations, establishing a longitudinal power protection criterion based on the action quantity, the braking quantity, the set proportional braking coefficient, the reliability coefficient and the action fixed value of the longitudinal power, and controlling a protection device based on the longitudinal power protection criterion so as to protect the longitudinal power of the three-terminal distributed diode rectification and transmission system.

Description

Pilot power protection method and device Technical Field The invention relates to the technical field of power system protection, in particular to a longitudinal power protection method and device. Background With the deep advancement of energy transformation strategy in China, new energy power generation technology is rapidly developed, and the installed scale of renewable energy is continuously increased. However, the new energy resource distribution in China presents obvious regional characteristics, the problem of space mismatch of the resource enrichment region and the load concentration region is presented, the problem is presented as structural contradiction that the capacity of the resource enrichment region is insufficient and the energy supply of the load center region is relatively deficient, and the current situation severely restricts the efficient utilization and large-scale development of the new energy. In order to solve the difficult problem of the consumption of renewable energy sources, a new energy source is rectified and sent out by a three-terminal distributed diode, and an economically feasible technical path is provided for realizing the medium-distance and provincial-level delivery of the new energy source. According to the technology, an independent island power grid is constructed by deploying a network-structured energy storage system, so that the autonomous networking operation of new energy is realized, and the efficient delivery of electric energy is completed by combining a distributed diode rectification technology, so that the problem of mismatch of the geographic position between new energy consumption and load demand can be effectively relieved. In the field of relay protection of power systems, in order to solve the problem of fault protection of a direct current system, various technical means are conventionally adopted. For direct current line protection, a main protection device based on a traveling wave principle and a differential undervoltage principle is common. The protection device based on the traveling wave principle judges the position and the type of the fault by utilizing traveling wave signals generated during the fault, and the protection device based on the differential undervoltage principle realizes the fault detection by monitoring the change rate and the amplitude of the voltage. In addition, pilot protection of conventional two-terminal systems is also a common means of determining fault conditions by comparing the electrical quantities between two measurement terminals. Meanwhile, in the aspect of acquiring fault data, fault wave recording data of a converter station monitoring device in the system can be collected or simulation is carried out to obtain related data. In data analysis, some conventional transformation methods are also used to process the data. However, the failure mechanism of the three-terminal distributed diode rectification power transmission system is complex, and the failure characteristics of the three-terminal distributed diode rectification power transmission system are obviously different from those of the traditional two-terminal direct current system. The main protection device based on the traveling wave principle and the differential undervoltage principle has obviously reduced sensitivity when facing high-resistance faults, because the traveling wave characteristics are weak when the high-resistance faults occur, and the traveling wave signals can further attenuate signal energy due to complex refraction and reflection when passing through a T contact point of a line, so that the sensitivity of fault detection is affected. The influence of the new energy control strategy on the system protection is more remarkable, the sending end of the system is usually connected with a new energy power generation unit with extremely high proportion, and the diode rectifier does not have active control and regulation capability, so that the fault transient process is rapidly conducted into the direct current system, the fault characteristics inside and outside the area tend to be fuzzy, and the complexity of fault identification is increased. In addition, the adverse effect of synchronization errors on the pilot protection is further aggravated, the pilot protection of the traditional two-end system only needs to consider clock synchronization errors between two measurement terminals, and the three-end distributed system is required to realize accurate time synchronization between a plurality of measurement points, and the accumulation of synchronization errors threatens the reliability of protection criteria. Disclosure of Invention The invention aims to solve at least one technical problem by providing a longitudinal power protection method and a longitudinal power protection device. The technical scheme for solving the technical problems is as follows: In a first aspect, the present application provides a pilot power protection me