CN-122000913-A - Transient oscillation characteristic analysis method and system for single-loop PI control direct current power flow controller

CN122000913ACN 122000913 ACN122000913 ACN 122000913ACN-122000913-A

Abstract

The invention provides a method and a system for analyzing transient oscillation characteristics of a single-loop PI control direct current power flow controller, wherein the method comprises the steps of constructing a transfer function matrix of a direct current power flow controller with common inductance between two lines, dynamically dividing the direct current power flow controller into a full control system and a semi-autonomous system based on the transfer function matrix, solving the maximum singular value of the semi-autonomous system by utilizing a singular value decomposition technology, researching the transient oscillation characteristics of the direct current power flow controller, analyzing the singular value decomposition result of the semi-autonomous system of the direct current power flow controller through frequency sweeping, comprehensively considering line resistance and control reference values, and analyzing the influence rule of key parameters of the direct current power flow controller on transient oscillation of the system. The invention fully utilizes the active response characteristic of the DC power flow controller to the disturbance of the DC micro-grid, provides reference for the transient oscillation suppression of the DC micro-grid based on the system dynamic realization, and can realize the DC power flow control adapting to the complex scene of the DC power grid.

Inventors

LIN PENGFENG
ZHOU YURUI
ZHU MIAO
ZHANG HONGYI

Assignees

上海交通大学

Dates

Publication Date: 20260508
Application Date: 20241101

Claims (10)

1. A transient oscillation characteristic analysis method of a single-loop PI control direct current power flow controller is characterized by comprising the following steps: Step S1, constructing a transfer function matrix of the two-line shared inductance type direct current power flow controller, wherein the matrix is based on an equivalent state space model of the two-line shared inductance type direct current power flow controller controlled by single loop PI; Step S2, dynamically dividing the direct current power flow controller into a full control system and a semi-autonomous system based on the transfer function matrix; s3, carrying out maximum singular value solution on the semi-autonomous system by utilizing a singular value decomposition technology, and researching transient oscillation characteristics of the direct current power flow controller; And S4, analyzing the singular value decomposition result of the semi-autonomous system of the direct current power flow controller through frequency sweep, comprehensively considering the line resistance and the control reference value, and analyzing the influence rule of the key parameters of the direct current power flow controller on the transient oscillation of the system.
2. The method for analyzing transient oscillation characteristics of a single-loop PI controlled dc power flow controller according to claim 1, wherein the process of constructing a transfer function matrix in step S1 includes the steps of: Step S1.1, writing state space equation of the common inductance type direct current power flow controller between two lines: wherein D represents that the variable is a small signal disturbance, And Respectively represent the differentiation of line 13 current, PI current loop differentiation term, differentiation of common inductor current, differentiation of line 12 current, differentiation of line 23 , differentiation of voltage across capacitor C 1 , differentiation of voltage across capacitor C 2 , differentiation of voltage across the port of VSC1 and differentiation of voltage across the port of VSC2, d is the dynamic duty cycle of switch Q 1 , U C1 、U C2 and I L are both steady state values, U C1 、u C2 and I L are both dynamic values, a represents the system matrix of the common inductor dc current controller between the two lines, B represents the input matrix of the system, C represents the output matrix of the system, X represents the state variable of the system, Differential representing a system state variable, u representing an input variable of the system, and Y representing an output variable of the system; S1.2, dynamically dividing the state variables according to whether the state variables are completely controlled by the PI single ring, and classifying the state variables controlled by the PI single ring into a controllable system and classifying other state variables into an autonomous system; And S1.3, constructing a small signal model of the autonomous system based on the input variable and the output variable of the autonomous system to obtain a transfer function matrix.
3. The method for analyzing transient oscillation characteristics of a single-loop PI-controlled dc power flow controller according to claim 1, wherein the process of dynamically dividing the single-loop PI-controlled dc power flow controller into a fully-controlled system and a semi-autonomous system in step S2 comprises the following steps: S2.1, determining a state variable controlled by a PI single loop, and classifying the state variable into a controllable system; s2.2, determining a state variable which is not controlled by the PI single loop, and classifying the state variable into an autonomous system; and step S2.3, respectively establishing state space equations of the controllable system and the autonomous system.
4. The method for analyzing transient oscillation characteristics of a single-loop PI controlled dc power flow controller according to claim 1, wherein the solving the maximum singular value in step S3 by using a singular value decomposition technique comprises the following steps: S3.1, under a preset frequency, carrying out singular value decomposition on a transmission function matrix; And S3.2, determining the maximum singular value corresponding to each frequency point to represent the response peak value of the state variable of the autonomous system which can be excited by the input variable of the system.
5. The method for analyzing transient oscillation characteristics of a single-loop PI controlled dc power flow controller according to claim 1, wherein the process of frequency sweep analysis in step S4 includes the steps of: s4.1, changing the frequency of an input signal, and calculating the maximum singular value corresponding to each frequency point; and S4.2, comprehensively considering the changes of the line resistance and the control reference value, and analyzing to obtain the influence rule of the key parameters of the direct current power flow controller on the transient oscillation of the system.
6. The method for analyzing transient oscillation characteristics of a single-loop PI controlled dc power flow controller according to claim 1, further comprising: and S5, verifying the effectiveness of the transient oscillation characteristic analysis method in the three-terminal looped network direct current transmission system, and observing the change condition of the transient oscillation characteristic of the system by changing the line resistance and the line current reference value.
7. The method for analyzing transient oscillation characteristics of a single-loop PI controlled dc power flow controller according to claim 6, wherein the verification process in step S5 includes the steps of: s5.1, placing a direct current power flow controller between two wires containing single-ring PI control into a three-terminal ring network direct current transmission system; s5.2, setting a line current reference value, and actively regulating and controlling the tide of a preset line; and S5.3, changing the reference values of the line resistance and the line current, and observing and recording the change condition of the transient oscillation characteristic of the system.
8. The method for analyzing transient oscillation characteristics of a single-loop PI-controlled dc power flow controller according to claim 1, wherein the topology of the two-wire shared inductance-type dc power flow controller comprises two voltage source-type converters and a shared inductance.
9. The method for analyzing transient oscillation characteristics of a single-loop PI control dc power flow controller according to claim 1, wherein the single-loop PI control includes a current loop and a voltage loop, wherein the current loop is used for controlling a current in a common inductor, and the voltage loop is used for controlling an output voltage of a voltage source converter.
10. The transient oscillation characteristic analysis system of the single-loop PI control direct current power flow controller is characterized by comprising the following modules: The module M1 is used for constructing a transfer function matrix of the two-line shared inductance type direct current power flow controller, wherein the matrix is based on an equivalent state space model of the two-line shared inductance type direct current power flow controller controlled by single loop PI; the module M2 dynamically divides the direct current power flow controller into a full control system and a semi-autonomous system based on the transfer function matrix; The module M3 is used for carrying out maximum singular value solution on the semi-autonomous system by utilizing a singular value decomposition technology and researching transient oscillation characteristics of the direct current power flow controller; and the module M4 is used for analyzing the singular value decomposition result of the semi-autonomous system of the direct current power flow controller through frequency sweep, comprehensively considering the line resistance and the control reference value, and analyzing the influence rule of the key parameters of the direct current power flow controller on the transient oscillation of the system.

Description

Transient oscillation characteristic analysis method and system for single-loop PI control direct current power flow controller Technical Field The invention relates to the technical field of electrical engineering, in particular to a method and a system for analyzing transient oscillation characteristics of a single-ring PI control direct current power flow controller, and particularly relates to a method for analyzing transient oscillation characteristics of a single-ring PI control direct current power flow controller based on system dynamic segmentation. Background With the integration of renewable energy sources into power systems, which have been regarded as irreversible ways to achieve carbon neutralization, the gradual replacement of conventional non-renewable energy sources with clean energy sources has become a trend to further increase the utilization of solar energy, wind energy and nuclear energy. At present, the form of a power distribution system is greatly changed, the energy consumption needs are increasingly diversified, the energy types are continuously diversified, and the renewable energy grid connection proportion is higher. However, with the trend of high permeability of renewable energy sources, its randomness and volatility pose a great challenge to the grid. The flexible direct current transmission technology can relieve uncertainty caused by large-scale new energy grid connection, and improve the flexibility, stability and economy of operation of the novel power system. By adopting the flexible direct current transmission technology based on the multi-terminal direct current transmission technology, the novel energy source large-scale grid-connected digestion and the overall energy utilization efficiency improvement of the novel power system can be realized. However, the multi-terminal direct current transmission technology has a network structure topology, and has the problems of incomplete control of the direct current flow of a line, section blockage, line overload and the like. The direct current power flow controller is introduced into the multi-terminal direct current power transmission system, so that the active regulation and control of the power flow of each line in the direct current power transmission system can be realized, and the stable operation of the flexible direct current power grid can be realized. By adopting the method for analyzing transient oscillation characteristics of the single-loop PI control direct current power flow controller based on system dynamic segmentation, the direct current power grid containing the direct current power flow controller can be subjected to targeted transient oscillation inhibition. In the literature 'inter-line direct current flow controller with fault current limiting function and control method thereof', a high-voltage flexible direct current power grid is taken as an effective means for solving the problems of large-scale access and digestion of renewable energy sources, and becomes one of important development directions of a future power system, but the problems of flow control and fault protection of the power system are more outstanding. In order to overcome the problems and improve the system stability, an inductance coupling type composite device with the dual functions of direct current flow control and fault current limiting is provided. Firstly, a topological structure of the composite device is provided, a current limiting branch capable of sharing a coupling inductance is added on the basis of a traditional direct current flow controller, secondly, the working principle, theoretical deduction and control strategies of a direct current flow function are analyzed in detail, then, based on a current limiting action time sequence provided under a fault condition, the effect of the coupling inductance under 4 different time periods of steady state, current limiting, fault removal and energy release is further analyzed, calculation of direct current fault currents in each time period is researched, finally, a four-terminal direct current power grid model is built on MATLAB/SIMULINK simulation software, and simulation results show that the proposed topology achieves good tide control and short circuit current restraining functions through sharing the coupling inductance, fault current removal time is shortened under a short circuit fault state, and stability of the system is improved while economical efficiency is ensured. The document provides a direct current flow controller with a current limiting function and capable of realizing transient fault current suppression, and provides a current limiting switch action time sequence aiming at fault transient, but the direct current flow controller does not relate to transient research in the switching process of the direct current flow controller under normal working conditions, and the scheme provides an analysis method for covering transient oscillation characteristics u