Ride-through Of Wind Doubly-fed Generator During Grid Voltage Dip

Wind power is a clear, renewable energy sources that holds great promise for the era of low carbon economy. As the penetration of wind power in electric power systems continues to grow, it becomes very important to improve the fault ride-through capability of grid-connected wind turbines. Model of doubly fed inductor generator based wind turbine is built in Matlab/Simulink. A DFIG applied to wind power generation is under study for low voltage ride-through (LVRT).The mathematical model of DFIG based wind turbine was built. Then the control strategies have been derived, including maximum power point tracking (MPPT) strategy of wind turbine, stator voltage oriented vector control strategy of the DFIG and grid voltage oriented vector control strategy for the grid-side converter.When the stator voltage drops to zero, by the method of Laplace transforms, the analytical solutions of transient flux and current are presented. The key issues of LVRT are discussed in-depth.In order to protect the system, an improved vector control strategy of the DFIG without using any other hardware circuit is proposed to reduce the rotor over-current during non-serious voltage dips, which considers the dynamics of the stator flux deduced by the voltage dip when designing the rotor PI controller. In order to meet grid code and improve LVRT capability of DFIG based wind turbine, reactive power compensation strategies based on rotor-side convertor and grid-side convertor are designed, respectively.This paper has also considered how the system will respond when a active crowbar is applied. The effect of various values of crowbar resistance is examined. The control objects of crowbar based plan of LVRT are discussed. Cooperated with reactive power compensation strategies, timer crowbar and hysteresis crowbar based LVRT plans are proposed, which can settle the key two issues of DFIG based wind turbine during serious voltage dips.