Wind Farm Subsynchronous Oscillation Mechanism And Suppression Strategy Considering STATCO

The installed capacity of wind power is increasing year by year,which has become the main component of renewable energy generation.Due to the long transmission distance and large scale of wind power,fixed or controllable series compensation is often used to improve the transmission capacity of the line.The subsynchronous oscillation accident caused by series compensation has become one of the major hidden dangers threatening the stable operation of the power system.Reactive power compensation devices(such as STATCOM)are often installed in actual wind farms to stabilize the grid-connected point voltage.However,most of the current researches on the subsynchronous oscillation characteristics of wind farms do not consider the interaction of reactive power compensation devices.In view of the above problems,this paper explores the mechanism and characteristics of subsynchronous oscillation of DFIG wind farm considering STATCOM by disturbance response method and impedance analysis method,and proposes STATCOM based on improved LADRC to suppress subsynchronous oscillation of wind farm.The main research contents of this paper are as follows :Based on the disturbance response method,the subsynchronous disturbance interaction mechanism between DFIG and STATCOM is analyzed.Firstly,the structure of DFIG wind farm with STATCOM and the mathematical model of key components are introduced.Then,the response path of subsynchronous disturbance in DFIG and STATCOM and the dynamic interaction mechanism between them are derived.The process of subsynchronous control interaction in the system is explained.It is proved that when the parameter configuration is unreasonable,the disturbance response of STATCOM can help to increase the subsynchronous oscillation of the system.The impedance analysis method is used to explore the sub-synchronous oscillation characteristics of the wind farm with STATCOM,and the impedance expression of the DFIG wind farm with STATCOM sent out by series compensation is derived.According to the impedance expression,the conditions and mechanism of sub-synchronous oscillation in the system are derived,as well as the related factors affecting the system impedance.The overall impedance model is built in the simulation system.According to the impedance frequency response curve,the influence of STATCOM on the stability of the system is explored,as well as the influence of STATCOM control delay and fan control parameters on the impedance.A static synchronous compensator based on improved linear active disturbance rejection control is proposed to suppress the sub-synchronous oscillation of wind farm.Firstly,the linear active disturbance rejection controller is improved to solve the problem of time axis mismatch between the input signals of the controller.Then,a STATCOM control system based on fully improved linear active disturbance rejection control is designed,including additional damping controller,voltage outer loop and current inner loop controller and phase-locked loop.Then,the mechanism of STATCOM suppressing subsynchronous oscillation is analyzed from the perspective of impedance,and the time domain simulation model of the system is built in MATLAB / Simulink to verify the effectiveness and superiority of the suppression strategy.