Study On Sub-synchronous Oscillation Characteristics And Suppression Strategy Of Doubly-fed Wind Turbine

Wind power is one of the fastest growing new energy resources in the 21 st century.However,the regional difference between wind resources and energy load centers make large-scale wind power transmission inevitable.The technology of series capacitor compensation can solve the long-distance transmission of wind power effectively,however,it is easy to lead a phenomenon called sub-synchronous oscillation(SSO).In this paper,The SSO in doubly fed induction generator(DFIG)is analyzed and the suppression strategy of SSR is studied.First of all,the SSO phenomenon in wind farms is summarized and analyzed,the conclusion has been obtained that the SSO phenomenon is mainly focused on doubly fed wind turbines.Based on the mathematical model of DFIG,the mechanism of the SSO phenomenon and the influence of the sub-synchronous frequency variation on the DFIG are both analyzed.The reason which cause the SSO on the DFIG is the interaction between the control system of DFIG's converter and the series capacitor compensation.Based on this,the complex torque coefficient method is adopted to investigate the influence of the system parameters on the probability of SSR occurrence.Secondly,the suppression strategy of SSO of DFIG is investigated at both the hardware and software level.In this paper,the SSO suppression strategies based on the rotor side converter(RSC)of DFIG are studied emphatically.The suppression scheme based on Proportional-Integral(PI)regulator is proposed,including the quasi-resonant regulator strategy and sub-synchronous damping strategy.As for the application of high power doubly fed wind power converter,a SSO suppression scheme based on model predictive control(MPC)is proposed,which includes the strategy based on the rotor sub-synchronous harmonic current command and the strategy based on the stator sub-synchronous harmonic current feedback.Finally,a experimental platform of double fed wind turbine is designed at both the hardware and software level,and the SSO suppression schemes based on PI regulator are experimental verified.A 2MW doubly fed wind turbine simulation platform is established through Matlab/Simulink,and the SSO suppression schemes based on MPC is simulated and verified.