Research On Impedance Stability Optimization Method Of Doubly Fed Induction Generator System

Energy is the basis of the development of modern society.With the development of the wind power industry,the use of wind energy in new energy sources is becoming more and more popular.In order to use wind energy more efficiently and safely,the research on the stability of the wind power system grid connection has also been put on the agenda.At the same time,due to the far distance between the grid-connected interface of the wind power generation system and the grid,the grid presents unfriendly weak grid characteristics.Therefore,the grid-connected stable operation of the doubly-fed induction generator system can not be ignored,which is the mainstream of the wind power industry.This paper focus on the doubly-fed induction generator system,and its goal is to improve the system grid-connected stability.This paper has done some researches as follows:First,starting from the basic structure of the doubly-fed induction generator system,the system could be divided into two subsystems,namely the grid-side converter system and the rotor-side converter system.Acorrding to the Erchoff’s law and circuit topology we can obtain the basic time-domain mathematical model,after coordinate transformation and small signal linearization,derives the small signal model under the synchronous rotating coordinate system,and combines the control structure of the system to obtain the impedance model.Finally,we can obtain the whole impedance model of the system,which lays the foundation for the subsequent analysis of the grid-connection stability of the system.Then,based on the control structure of the doubly-fed induction generator system,in accordance with the traditional automatic control theory,the relevant control parameters of the grid-side converter subsystem and the rotor-side converter subsystem are respectively designed,and the grid-connected impedance stability analysis theory and frequency domain passivity theory are introduced in detail.Combineing with the obtained impedance model and design parameters,this article analyzes the the interface impedance characteristics and grid stability of doubly-fed induction generator system,and finally by building a simulation model of doubly-fed induction generator system,the abovementioned analysis conclusion is validated scientifically.Finally,the control parameters that mainly affect the grid-connected stability of the system are analyzed for their influence on the system impedance passive area.Taking into account the limitations of the traditional grid-connected impedance stability analysis,this article optimizes the system control parameters from the angle of frequency-domain passivity,making the doubly-fed induction generator system under the condition of the interconnection of the equivalent admittance of passive resistance increase,which makes the doubly-fed induction generator system get the optimization and improvement of gridconnected stability and robustness.Finally,the analysis conclusions are verified in the simulation model.