Research On The Active Crowbar Technology For Doubly-fed Wind-driven Generator

Doubly-fed Induction Generator wind power generation system is becoming a significant research field in wind-energy domain all over the world, due to its advantage of partial converter, controlling active and reactive power independently and high efficiency. In this paper a Low Voltage Ride Through (LVRT) technique of DFIG based on active crowbar is studied in detail. The effectiveness and feasibility of the proposed LVRT technique is validated through both simulation and experimentation.The principle of DFIG wind power generation system is analyzed and the mathematic model is developed. The dynamic response of DFIG during voltage sags under vector control is studied. A LVRT scheme is proposed based on analyzing the key factors which constraint the LVRT capability.A simulation model of 1.5MW DFIG wind power generation system with back to back PWM inverter is built. The dynamic response of DFIG during voltage sags based on the vector control strategy is studied based on the simulation model. The function of the active Crowbar in LVRT is studied and the parameters of the active Crowbar are given. The simulation result shows that the DFIG system with active crowbar can protect converter against overvoltage and over current. Then the system can provide reactive power to the grid in order to meet the requirement of power system to wind system during voltage sags.Finally, main power circuit and driving circuit of the active Crowbar is designed. A VSG (Voltage Sag Generation) based on resistor is built. The corresponding experiment is done on the 90kW DFIG experimental platform.The LVRT scheme based on the active Crowbar is studied through experimentation. The experiment result shows that Crowbar is necessary for improving LVRT capability of DFIG wind power generation system and LVRT scheme based on the active Crowbar is effective.