Mathematical Modeling And Small Signal Stability Analysis Of Grid-connected Doubly-fed Wind Power Generation System

With the environmental destruction and increasing scarcity of traditional resources,comprehensive development of clean,environmentally friendly and renewable energy has become an important opportunity for wind power industry.At present,many wind turbines used in wind farms are doubly-fed wind turbines.The power fluctuation caused by wind speed and various dynamic responses have a profound impact on the voltage amplitude,frequency,power quality and output power of doubly-fed wind turbines.In this paper,the mathematical model of doubly-fed induction generator(DFIG)is established to carry out grid-connected research,and the stability of DFIG system is deeply discussed based on small signal model.Firstly,the basic principle of DFIG is introduced,and its basic mathematical model and dynamic mathematical model are established.Secondly,several control strategies of doubly-fed wind power generation system are discussed,including maximum power tracking system,converter control system,etc.The mathematical model of doubly-fed wind power generation unit and the analysis of control system are completed.Then,in order to improve the grid-connected stability of the system,the stability of doubly-fed wind power generation system is analyzed by small signal modeling.The detailed mathematical model of DFIG grid-connected system is established in d-q coordinate system,and the method of linearization is proposed to get the overall small signal model.The overall small signal model uses the characteristic matrix of the DFIG grid-connected system and the eigenvalue analysis method to calculate the steady-state eigenvalues,participation factors and participation degree of the DFIG grid-connected system,and to judge the stability and damping characteristics of the grid-connected system.Some typical electrical parameters of DFIG grid-connected system are selected to study their influence on the stability of grid-connected system.Finally,the simulation model of the DFIG grid-connected system is established to verify the correctness of the control strategy and small signal analysis of the DFIG grid-connected system.