Modeling on Converters of Direct-driven Wind Power System and Its Performance During Voltage Sags

To enhance the low voltage ride through(LVRT) capability of direct-driven variable-speed constant frequency(VSCF) wind power system,some countermeasures must be taken.By adding damp load at DC-side of the converter,redundant energy at DC-side during grid faults will be consumed,therefore the operating of wind turbine will not be influenced by grid voltage sags.The back-to-back dual PWM converter is used,and the principles of generator-side converter,grid-side converter and damp load are analyzed in detail,then the whole modeling of the converter is realized.The simulation model of the converter is developed based on the Matlab7.3/simulink6.5,and the performance during grid voltage sags is simulated,which demonstrates the validity of the model and analysis.The results show that direct-driven wind power system have good capability of fault ride through and fast dynamic respond speed by using damping load at DC-side.