Research On Control Strategy Of DFIG And Wind Farm Equivalent Model

Energy crisis and environmental deterioration have become important factors that restrict the survival and development of human beings,and wind energy as a clean and renewable energy,has attracted more and more attention by the whole world.Doubly-fed wind turbine has become the current mainstream wind turbine because of its mature control technology and high reliability.The study of high performance control strategy for doubly-fed wind power generation system and high precision equivalent modeling method for doubly-fed wind farm has great significance to improve the power conversion efficiency of the wind power system and the safety and stability of the power system in large scale wind power grid connection.This paper first describes the development status and development trend of wind power generation,and compares the advantages and characteristics of the DFIG-based wind power generation system with SCIG-based wind power generation system and PMSM-based wind power generation system.The research status of model predictive control algorithm,wind turbine generator’s maximum power tracking control method and the wind farm’s equivalent modeling method are analyzed.The basic structure and working principle of doubly-fed wind power generation system are analyzed,the mathematical model of doubly fed induction generator is established,and the operation condition characteristics and power flow characteristics of doubly-fed wind power generation system are discussed.The operating principle of back to back PWM converters is analyzed.Based on the simplified mathematical model of grid-side converter,predictive control strategy of grid side converter-current is analyzed,designs the predictive current controller and its cost function.A partition variable step size hill-climbing method is proposed to realize the maximum power tracking of the doubly-fed wind power generator,designs rotor-side converter’s PI controller of speed,the d-axis and the q-axis current.The selection principle of the wind power generating turbines is analyzed,and then the principle of fuzzy-C means clustering algorithm and the detailed steps of using the weighted fuzzy-C means clustering algorithm for wind turbines are analyzed.Then analyzes the parameters identification principle and detailed steps of equivalent models based on global optimal mutation particle swarm optimization algorithm,realized the high precision equivalent modeling of DFIG-based wind farm.In this paper,the Simulink platform and DIg SILENT platform are used to verify the validity of the proposed theory.The simulation results show that the control strategy of grid side converter using predictive control method and the maximum power tracking control strategy of partition variable step size hill-climbing method,the dynamic and static performance of the doubly-fed wind power generation system is improved.Compared with the traditional single generator equivalent model,dynamic characteristic of the established dynamic equivalent model is basically consistent with that of the detailed model,which can accurately reflect the dynamic operating conditions of the wind farm.