Damping Control Of Large-scale DFIG-based Wind Power Generation System Based On WAMS

In recent years,wind energy as a green and clean energy has developed rapidly.However,most wind power bases are far away from load centers,and cross-region wind power absorption is often achieved through interconnection of power grids.Moreover,the output power of wind power is random and uncertain,which undoubtedly increases the possibility of interval low frequency oscillation in power system.It is difficult to suppress the interval low-frequency oscillation in interconnected power systems by relying solely on local signal-based local controllers.The infrastructure construction and application development of smart grid based on wide-area measurement system(WAMS)provide certain technical possibilities for suppressing the interval low-frequency oscillation.However,due to the inevitable delay of wide-area signals in transmission channels,this method is adopted.It is necessary to consider the time-varying delay effect of wide-area signals when additional damping control is applied to wide-area signals.Focusing on the two key technical issues of damping control and time-delay compensation,the main research contents of this paper include the following parts:In the first part,the mechanical system model and the doubly-fed induction generator(DFIG)model of doubly-fed wind turbines are established,and the power system linearization model with wind turbines is deduced.On the basis of the linearization model,a single-input-single-output transfer function model identification method is deduced by using Prony algorithm.In the second part,based on the time-delay output feedback control technology of power system,combining with classical PSS structure,a unified design method for feedback gain and phase compensation parameters of wide-area dampers considering the effects of phase shift and time delay is proposed.This design method adopts the principle of near compensation to reduce the compensation phase angle and the number of compensation links in series,which greatly simplifies the structure of the controller.In the third part,according to the characteristics of time delay distribution of WAMS under the actual operation conditions of power system,based on the discretization requirement of time delay data in computer simulation,the method of constructing time delay sequence of WAMS is designed,and the structure with Rice probability is constructed.In the fourth part,aiming at the random distribution and time-varying characteristics of WAMS time-delay,a time-delay adaptive wide-area damper control structure is designed,which adopts joint criteria to update the controller parameters.The controller fully takes into account the stochastic fluctuation of time delay and the short-term and large-scale change of time delay,which has no obvious influence on the relatively slow low-frequency oscillation damping control.,and the negative effects caused by frequent switching of controller parameters can be avoided,and improve the system damping proformance.