Active Disturbance Rejection Control of Current of Direct Drive Wind Turbine in Power Grid Fault

The grid connection guidelines require wind turbines to have capability to quickly support reactive power in the events of grid faults. However, traditional proportional-integral controllers have the problems of slow transient response and poor adaptability dealing with changes in grid impedance and serious model disturbances. In order to solve this problem, this paper proposes an improved reactive power support control strategy which combines linear active disturbance rejection control(ADRC) with least error squares(LES) filters. The LES filter is used to quickly and accurately detect the amplitude of the fault grid voltage with background harmonics, which can effectively reduce the fault detection delay. The ADRC controller is used to effectively improve the transient reactive power response speed and the control adaptability and robustness of the wind turbines under grid impedance disturbance. The simulation model of direct drive wind turbine based on PSCAD/EMTDC is built considering two scenarios, weak power grid and power grid with background harmonics. The effectiveness of the proposed control strategy is verified by simulation.