Variable Coefficient Based Coordinated Frequency Modulation Strategy Between DFIG-Based Wind Turbine And Synchronous Generator

With the energy crisis and environmental problems increasingly serious,wind power has received a whole worldwide attention as a clean renewable energy source.In China,where the wind energy resources are abundant,the penetration rate of wind power is more than 20%.With the increasing capacity of wind power and the increasing permeability,the influence of large-scale wind power grid on the frequency and safety of power grid is becoming more and more obvious.DFIG(Doubly-Fed Induction Generator)has become the main active model,but its rotor speed and grid frequency decoupling control mode determines its output power can not respond to the power grid frequency changes.When the penetration of wind power continues to rise,the grid frequency modulation pressure is increasing.Therefore,it is important to study the frequency modulation technology of doubly-fed wind turbine and the coordinated frequency modulation strategy with synchronous generator.In this paper,the frequency control strategy of double-fed wind turbine is the main content,and the frequency modulation technology of double-fed wind turbine is studied on the basis of the existing literature review.Firstly,the history and trend of wind power development at home and abroad are summarized,and the problems that should be paid attention to in the process of rapid development of wind power technology are analyzed,and the related technologies of wind power frequency modulation are summarized.Based on the frequency response characteristics of synchronous generators,the simulated inertia characteristics of doubly fed wind turbines are analyzed theoretically.The experimental part of the simulation of inertia control is introduced,and the relevant control block diagrams are given.The traditional control method of pitch angle is improved,and it also has the ability of frequency response,and the frequency characteristics of the doubly fed wind turbine and the synchronous generator are compared.This paper also analyzes the shortcomings of the existing fixed frequency coefficient of the wind turbine,and further proposes the frequency modulation strategy based on the current wind speed of each wind turbine in the wind farm,so that the frequency modulation power in the wind farm can reasonably distribution.When the wind power is used as a new frequency modulation power supply into the grid,the coordinated control theory of the doubly fed wind turbine and the synchronous generator is deduced.According to the different operation modes of the doubly fed wind turbine,the related coordination frequency modulation strategy is developed.The simulation part is based on MATLAB/SIMULINK,and the simulation results show that the proposed variable coefficient frequency modulation strategy is conducive to smooth wind power fluctuations,which can make the reserve power of the doubly fed wind turbine more fully involved in the frequency modulation and effectively reduce the frequency modulation pressure of the synchronous generator.