A novel robust low voltage and fault ride through for wind turbine application operating in weak grids

Wind turbines are very susceptible to any disturbance, faults and low grid voltages. They are disconnected from the grid whenever these conditions arise and reconnected once the grid is healthy. Maintaining the wind turbine connected to grid is real challenge. Future grid codes will require wind turbines connected to grid even during the fault condition and have low voltage ride through (LVRT) feature installed. LVRT feature is not available in most of the present wind turbine and few do with addition circuitry and control increasing the cost of the system. In this paper, a novel control strategy and LVRT for wind turbines with doubly fed induction generators is presented to maintain the turbine connected to grid during fault and post fault condition without addition circuitry. The controller is designed using H_∞ technique and μ-analysis based robust control technique to take into account various adverse conditions. The controller is tested on low power hardware prototype and the results are presented.