Higher-Order Sliding Mode Control of DFIG Wind Energy System Under LVRT

Doubly-fed induction generator (DFIG) is widely applied in Variable Speed Constant Frequency (VSCF) wind power system. In recent years the proportion of wind power became more and more in the electricity supply. The failure of power grid will lead to voltage drop and will cause system transient instability and may lead to partial or full paralysis. So Low Voltage Ride Through (LVRT) requirements is paied attention to integration of wind power into electric net-work. The paper analyzed the DFIG mathematical model in detailed and proposed a control strategy when grid voltage dips. And according to the principle of sliding mode control (SMC), designed a higher-order SMC controller. Adopting the above control strategy the system can get good dynamical characteristics and realize the maximum power point tracking. Even though voltage sag in the power grid, the proposed control can effectively reduce the impact of the rotor currents and inhibit the DC bus voltage fluctuations. The simulation results validate the effectiveness of the control strategy.