Improved rotor current control of wind turbine driven doubly fed induction generators during network unbalance

This paper investigates an improved control and operation of a DFIG system under unbalanced network conditions. A new rotor current control strategy is presented, which consists of a main controller and an auxiliary compensator. The main controller is constructed in the same way as the conventional vector control design without involving sequential-component separation in order to guarantee system stability and high dynamic response. While the auxiliary controller is specially designed to control the negative sequence current taking into account the impact of the main controller on negative sequence components. Experimental results on a 1.5-kW DFIG prototype are provided and compared with those of conventional vector control and dual PI current control schemes to demonstrate the effectiveness of the proposed control strategy during steady-state and transient conditions when the network voltage is unbalanced.