Research On Converter Control Strategy And Low/high Voltage Ride Through Technology Of Doubly Fed Wind Power

As wind turbines accounted for the proportion of the power grid interconnection capacity increasing, the research of wind turbine running through operation under the grid fault has become an important research direction of wind power generation. The doubly fed wind power generator as the research object, analyzes the double fed wind generator under grid voltage dips, swells, fault low/high voltage ride through the transient characteristics of the operation. Using the cooperative control strategy of the grid side and rotor side converter of doubly fed machine, the hardware protection scheme is optimized, and the expected results are achieved.The mathematical model of the complete doubly fed wind turbine generator including doubly fed wind generator and grid side PWM converter and rotor side PWM converter is established in different coordinate systems.Grid side PWM converter using double-loop control of vector space, and adding the load current feedback and feed-forward of grid voltage to compensate inhibition load disturbance, the rotor side PWM converter based on the stator voltage oriented vector control strategy.The single doubly fed wind turbine simulation model is constructed based on MATLAB, model contains the LVRT hardware, pitch control,imitating the real dynamic characteristics of the actual system, to run through research laid the foundation of the DFIG. On the basis of in-depth study of the LVRT condition of rotor side and grid side converter and assisted with LVRT hardware system coordinated control strategy, based on grid guideline,calculate the LVRT double fed converter active and reactive power output, in the low voltage ride through improved control strategy, the grid side converter to the grid maximum feedback active, effectively reducing the DCbus voltage fluctuation, to ease the pressure on the protection circuit of DC chopper. Based on the control of reactive power output, the rotor side converter can inject active power to the grid to ensure the generator to generate enough braking torque to prevent the wind turbine from too fast.On the basis of traditional control strategy, adding a voltage sudden change of dynamic compensation, establish the DFIG accurate control model,on the basis of improved the DFIG based on stator voltage oriented vector control scheme, for DFIG high voltage ride through operation were studied.The dynamic compensation control strategy reduces the dynamic process of the DFIG, and the high voltage through Chopper and Crowbar protection circuit and control strategy of coordinated control is studied, and the simulation results are analyzed. In addition, the HVRT capability of Chopper and Crowbar circuit is simulated and evaluated, and the corresponding reconstruction scheme is used.