Research On Subsynchronous Oscillation Mechanism And Suppression Strategy Of Wind Farm Grid Connected System

Subsynchronous oscillation(SSO)is an abnormal operation state in power system.It usually occurs on transmission lines with series compensation capacitors and synchronous generators.When the sub-synchronous oscillation occurs in the power system,the sub-synchronous torque will be generated in the generator shafting,and the sub-synchronous component will be generated in the power system,which will affect the power quality.With the intensification of energy and environmental crisis,the large-scale development and utilization of wind power has attracted worldwide attention.In recent years,the sub-synchronous oscillation caused by wind farm grid-connected operation has occurred many times in China.Therefore,it is of great significance to study the mechanism and suppression of sub-synchronous oscillation in wind farm grid-connected system.Firstly,the electrical model of doubly-fed fan,DC bus model of back-to-back converter,control system model and series compensation capacitor circuit model are established,and the DQ decoupling control strategy of fan rotor-side converter and grid-side converter is analyzed.Secondly,the factors affecting the operation state of the fan are divided into two categories:natural parameters and operation parameters.The influence of two kinds of parameters on the subsynchronous oscillation of wind farm is studied by means of impedance frequency scanning method and eigenstructure analysis method,and the control parameters are transformed from signal analysis to electrical analysis.Thirdly,by analyzing the influence of operation parameters on the subsynchronous oscillation of wind farm grid-connected system(such as the ratio coefficient and integral coefficient of the internal current loop of the rotor-side converter),the relationship between operation parameters and subsynchronous oscillation is obtained,and on this basis,the objective function for finding the control parameters of subsynchronous oscillation suppression in wind farm is constructed.Then,an autotomy regeneration particle swarm optimization(ARPSO)algorithm based on particle swarm optimization(PSO)is proposed,and a self-cutting peel-off process is proposed for the poor local search ability of PSO in the early stage of calculation,and a tissue regeneration process is proposed for the poor global search ability of PSO at the end of calculation.The validity of the improved algorithm is verified by the test function.Finally,the objective function of the control parameters for subsynchronous oscillation suppression of wind farms is calculated by peeling regenerated particle algorithm,and a set of optimal control parameters are obtained and compared.By comparing the time domain simulation before and after the optimization of control parameters,it is verified that the optimization of control parameters can effectively suppress the sub-synchronous oscillation of wind farm.Time domain simulation after optimizing control parameters by comparing original PSO algorithm,linear weight PSO algorithm and ARPSO algorithm.The validity,accuracy and superiority in parameter selection of the improved ARPSO algorithm are verified.