Research On Optimal Tip-Speed Ratio Control Strategy In Wind Generation System

With the capability of wind generating systems constantly increasing,it is more and more important to improve the efficiency of the wind generator system in the research of wind electricity conversion system.Variable speed and constant frequency(VSCF) becomes hot point in the wind power conversion system and control of doubly-oriented converter is hard core in the doubly-fed generating system.In order to provide excitation to DFIG.as a result of doubly-PWM converter supplies merely slip power,the research reduces greatly the request to capacity of doubly-PWM converter.The thesis can adjust rotor excitation frequency based on wind turbine speed,assures that export constant frequency AC current at DFIG stator-side,and makes that wind turbine run under great rotor speed bound.In order to capture theλ_opt,this dissertation mainly researches a controlling arithmetic for doubly-oriented PWM converter.Firstly,the paper studies grid-side converter of doubly-PWM,which can finish energy conversion between rotor-side converter and power grid via DC-tache.The thesis founds math model of grid converter,and carries out simulation under Matlab.The simulation results show:DC voltage is controllable.Then,the thesis studies math model of DFIG,and founds stator flux linkage oriented vector control strategy of DFIG.And makes sure two control strategies under vector control:rotor-side control strategy under power control and rotor-side control strategy under speed control.Thereinto,power control strategy can complete decoupling control of active power and reactive power.Speed control strategy can make wind turbine run under sub-synchronous and super-synchronous speed,and switch quickly between sub-synchronous and super-synchronous speed. In the simulation,the thesis founds simulation model of rotor-side control strategy in Matlab,and gains simulation results under conventional PI control.Simulation results validate that the stator flux linkage oriented vector control strategy is correct.Finally,the thesis studies self-adjusting fuzzy PI control strategy,and carries out comparison analysis to conventional PI control.The comparison result shows that self-adjusting fuzzy PI control strategy has obvious superiority:quicker speed response and less overshoot,presents a feasible control strategy forλ_opt controll.It has some reference value for deeply research and experiment.