Research On Sub-synchronous And Super-synchronous Speed Dynamic Process Control Strategy In Wind Generation System

Variable speed constant frequency(VSCF)wind generation is a novel,effective,environmental protection generate electricity technology,which has favorable application foreground in wind generation field.The thesis makes use of work principle of doubly-fed induction generator(DFIG),then joins doubly-PWM converter at rotor-side of DFIG 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.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.Secondly,the thesis studies math model of DFIG,and founds stator flux linkage oriented vector control strategy of DFIG.The thesis researches several methods of flux linkage observation,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,then selects corresponding speed to maximum output power of wind turbine as reference value of vector control in the simulation experiment,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 one-input fuzzy PI control strategy,and carries out comparison analysis to conventional PI control.The comparison result shows that self-adjusting fuzzy one-input PI control strategy has obvious superiority:quicker speed response and less overshoot.The one-input fuzzy PI control has definite application worth.