Research On Virtual Synchronous Control Strategy Of Doubly-Fed Wind Turbine

Due to the gradual depletion of traditional energy and the aggravation of environmental pollution,wind power generation technology has been widely applied.The side-converter of doubly-fed wind power generator only needs to control the power difference,which can greatly reduce the converter cost and become the main generator model in the wind power generator system.The traditional vector control strategy of the doubly-fed wind turbine makes the motor speed and frequency decouple and cannot provide inertial support for the power grid.At the same time,the new energy generation of large-scale wind power generation is connected to the grid through power electronic equipment,which makes the overall grid system present the characteristics of "low inertia" and "weak damping",leading to the problems of frequency and voltage stability.In this paper,the virtual synchronous control strategy of doubly-fed wind generator is taken as the research object,and the effects of primary frequency modulation,inertial support and voltage regulation are studied.Firstly,the paper briefly describes the structure of doubly-fed wind turbine,establishes the mathematical model of doubly-fed wind turbine,the mathematical model of machine-side converter and net-side converter in different coordinate systems,and carries out simulation experiments on the net-side converter based on grid voltage oriented vector control strategy and the machine-side converter based on stator voltage oriented vector control strategy respectively in synchronous coordinate system.The normal operation of the doubly-fed motor is realized in the speed mode and the power control mode.Secondly,with the virtual synchronous control strategy as the main research content,this paper briefly discusses the working principle of the synchronous generator,constructs the virtual synchronous generator control model,designs the overall structure of the virtual synchronous control algorithm,and analyzes and studies the virtual synchronous control strategy adopted by the single grid-connected inverter,realizing the function of voltage regulation and frequency support of the common coupling point.At the same time,the virtual synchronous control model of doubly-fed wind turbine is constructed,its control structure is designed,and the virtual synchronous control strategy is adopted for doubly-fed wind power generation system,which realizes the functions of doubly-fed wind turbine with primary frequency modulation,inertial support and voltage regulation.Finally,a simulation model was built in MATLAB/Simulink to simulate the traditional vector control and virtual synchronization control strategies.At the same time,experiments were carried out on the experimental platform of 5.5k W wind turbine system.The feasibility and effectiveness of the adopted virtual synchronization control strategy were verified by the simulation and experiments.