CN-114006384-B - Series-parallel oscillation suppression strategy for wind farm under different operation conditions

CN114006384BCN 114006384 BCN114006384 BCN 114006384BCN-114006384-B

Abstract

The invention discloses a series-parallel oscillation suppression strategy of a wind farm under different operation conditions, which comprises the following steps of S1, determining the duty ratio of a voltage source type wind turbine generator in a system through the short circuit ratio of a wind farm access system, the serial compensation degree of a wind farm output line and the real-time output of the wind farm, S2, calculating the duty ratio of the voltage source type wind turbine generator in the system, S3, selecting a wind farm internal unit according to a certain strategy to perform mode switching, calculating the duty ratio of the voltage source type wind turbine generator to avoid introducing a new oscillation mode into the system, and real-time predicting the wind farm access system to analyze and adjust the external electric damping of the wind farm in real time, selecting proper wind turbine generator grid-connected power and the grid-connected electric distance of the wind turbine generator distance, and controlling the mode switching, thereby increasing the accuracy and the adaptation degree of the mode switching.

Inventors

YANG JING
FA LADIER
YING YOU
SUN YONG
HUA BIN

Assignees

浙江运达风电股份有限公司
国家电网有限公司
国网冀北电力有限公司电力科学研究院

Dates

Publication Date: 20260512
Application Date: 20211109

Claims (8)

1. The series-parallel oscillation suppression strategy for the wind farm under different operation conditions is characterized by comprising the following steps of: S1, calculating a short circuit ratio of a wind power plant access system through an admittance matrix formed by system power flow, and if a transmission line contains series compensation, correcting the admittance matrix to obtain the series compensation degree of the transmission line of the wind power plant; s2, taking real-time output of the wind power plant, the short-circuit ratio and the series compensation degree as inputs, outputting oscillation frequency and damping ratio by a width learning system subjected to history data training, adopting root mean square error as a judgment standard, adopting a weight mode to combine the oscillation frequency and damping ratio threshold judgment, and obtaining the duty ratio of the voltage source type machine wind turbine generator in the wind power plant according to the comparison result of the oscillation frequency and the damping ratio threshold judgment; And S3, selecting a unit in the wind power plant to switch modes according to a certain strategy, wherein the certain strategy is to select the unit to switch between a current source and a voltage source control mode according to the voltage source unit duty ratio requirement determined by the oscillation frequency and the damping ratio threshold value and the comprehensive priority sequence of unit output and electric distance from the grid-connected point.
2. The wind farm series-parallel oscillation suppression strategy according to claim 1, wherein step S1 comprises the steps of: S11, calculating the tide of a wind power plant access system, forming a corresponding admittance matrix Y, and calculating the equivalent short-circuit ratio ESCR of the system; step S12, the admittance matrix Y' of the system is corrected by judging the serial compensation investment of the station outgoing line.
3. The wind farm series-parallel oscillation suppression strategy according to claim 2, wherein the following specific calculation mode is obtained through step S11: Wherein DeltaV represents the variation of bus voltage, subscripts i and j represent bus positions respectively, z ji represents the mutual impedance between stations i and j, z ii represents the self impedance of station i, P i represents the actual output of the wind power plant, S i represents the short-circuit capacity of the wind power plant, and subscript pu represents the per unit value of the output of station.
4. A wind farm series-parallel oscillation suppression strategy according to claim 3, wherein when the wind farm outgoing line is connected to the series compensation, the system admittance is modified to calculate the outgoing line series compensation, and the original outgoing line admittance is changed from Y il to Y il ', and the modified system admittance matrix is Y'.
5. The method according to claim 4, wherein a modified system impedance matrix Z '=y' -1 is obtained according to a modified admittance matrix Y ', and a wind farm serial compensation degree k is calculated according to a line inductance x il ' between modified buses i and l and a transmission line serial compensation resistance x c : 。
6. The wind farm series-parallel oscillation suppression strategy according to claim 1, wherein step S2 comprises the steps of: step S21, training a wind power plant damping evaluation model based on wind power plant historical operation data, and monitoring a small disturbance process of the wind power plant; S22, obtaining system damping and dominant oscillation modes in real time through monitoring; In step S23, the oscillation prediction adopts a width learning (read LEARNING SYSTEM, BLS) system based on increment learning to update the weight of the original network structure, and the sample input x of the prediction system is expressed as: x=[P farm ,k,ESCR,K 1 ,K 2 ,K 3 ,…,L 1 ,L 2 ,L 3 ,...] The control method of the wind power plant energy management system comprises the steps of enabling K i to be a control mode of an ith unit, enabling K i =1 to represent that the unit i adopts a current source control mode, enabling K i =0 to represent that the unit i adopts a voltage source control mode, enabling the unit control mode to be known from field control, enabling P farm to be wind power plant output power obtained from the wind power plant energy management system, enabling L i to be an electrical distance from the ith unit to a grid connection point of the wind power plant, enabling ESCR to be a system equivalent short circuit ratio, and enabling K to be wind power plant serial compensation.
7. The series-parallel oscillation suppression strategy for the wind farm under different operation conditions according to claim 1, wherein the oscillation frequency omega of a system oscillation mode and the damping ratio xi of a corresponding oscillation mode are adopted as output results of width learning, namely Y= [ omega, xi ], the initial group numbers of characteristic nodes Z and reinforcing nodes H are respectively n and m, a network structure is represented as A m =[Z n |H m , and the obtaining mode of each group of characteristic nodes and reinforcing nodes is as follows We i 、βe i ,Wh i 、βh i are the weights and biases from the feature node to the output, the weights and biases from the feature node to the enhancement node, and the weights and biases are randomly generated by the incremental learning width learning system.
8. The wind farm series-parallel oscillation suppression strategy according to claim 6, wherein reasonable judgment standards and judgment thresholds are set to judge the approaching degree of the oscillation frequency and the damping ratio output by the width learning system and the oscillation frequency and the damping ratio of the actual system, the judgment standards adopt root mean square error, and the oscillation frequency and the damping ratio threshold are combined in a weighting mode, and the method is specifically expressed as the following formula: wherein k represents the number of key oscillation modes of the system, the superscript is a variable output by the width learning system, a and b represent the oscillation frequency and damping ratio weight, and a+b=1 is satisfied.

Description

Series-parallel oscillation suppression strategy for wind farm under different operation conditions Technical Field The invention relates to the field of power transmission, in particular to a series-parallel oscillation suppression strategy for a wind farm under different operation conditions. Background The method is an important strategic measure for realizing carbon peak and carbon neutralization by changing the energy structure and improving the duty ratio of clean energy sources such as wind energy and the like in the energy sources. However, due to the limitation of the intrinsic endowment of resources, the wind power resources of China are concentrated in the region of three North and far away from the load center, so that a wind power development mode of 'large-scale centralized development and long-distance high-voltage delivery' is adopted, wind power is connected to the tail end of a power system, so that a local region power grid is weakened gradually, and the delivery capacity of the system is reduced and the stability margin is reduced along with the increase of the delivery distance. The fixed series compensation technology is mature and low in cost, and is widely applied to a large-scale long-distance power transmission system so as to improve the system output capacity and the system stability margin. However, with the increase of the wind power duty ratio, the wind turbine generator set controlled by the traditional current source is equivalent to a large inductance to the outside, and is easy to form a capacitive resonance loop with the series compensation capacitor in the line, so that the secondary/super synchronous oscillation of the outgoing line is caused, the wind turbine generator set is off-grid in a large area, the safe and stable operation of the power system is seriously threatened, and irreversible mechanical damage is caused to the synchronous unit and the wind turbine generator set in the system. Therefore, in order to suppress wind farm oscillations fed out via series compensation, there are currently mainly two ways: (1) The line parameters are changed by a cut-off method or a thyristor-based controllable series compensation device (Thyristor Controlled Series Compensation, TCSC) to avoid the resonance point of the sub/super synchronous oscillation. The cut-off method mainly monitors grid-connected point oscillation harmonic waves of the wind power plant on line through an on-line detection device, and when the wind power plant is subjected to subsynchronous/supersynchronous oscillation, the wind power plant is directly cut off so as to avoid power system oscillation caused by single wind power plant oscillation; (2) The system oscillation is suppressed by improving the electric damping of the power system through an optimized control strategy, and the main modes comprise optimizing the control strategy of a flexible alternating current transmission system (Flexible AC Transmission Systems, FACTS) device and optimizing the control strategy of a wind turbine generator set. The former mainly comprises a static var Generator (STATIC VAR Generator, SVG) control strategy for optimization and upgrading, and the latter mainly comprises (but is not limited to) providing positive damping oscillation current under different oscillation frequencies by using a virtual impedance method, providing system oscillation damping by using an adaptive oscillation resonance controller and the like. In the prior art, the method has the following two defects that 1, a wind farm is cut off and simultaneously impacts a power system, and adverse effects are caused on the safety and stability of the system, 2, the TCSC is adopted to restrain system oscillation, so that the construction and operation cost of a power transmission system is increased, and additional fault points are increased due to the addition of new hardware, so that the reliability of the system is reduced. For example, a PIR-based flexible dc transmission system oscillation suppression strategy disclosed in the chinese patent literature has publication No. CN112103969a, and includes a problem that electrical damping of a wind farm cannot be adjusted in real time according to different external grid conditions, and the wind farm can impact a power system while cutting off the wind farm, thereby adversely affecting safety and stability of the system. Disclosure of Invention The invention aims to solve the problems that in the prior art, the electric damping of a wind power plant is changed by adjusting the control parameters (such as rotor current inner loop PI controller parameters, power outer loop PI controller parameters and the like) of a traditional current source type wind power plant, but the instability of a wind power plant system can be caused by improper parameter selection, and the robustness of a parameter selection method based on empirical analysis is poor, and provides a series-parallel oscillation suppression strat