Active power control (APC) of PMSG wind farm using emulated inertia and droop control

Variable Speed Wind Turbine (VSWT) employing Permanent Magnet Synchronous Generator (PMSG) uses full scale back- to-back converter that totally decouples the rotating parts of the wind turbine and the generator from the electrical network. Therefore, there is no inertial contribution from the PMSG VSWT for primary frequency regulation. The modern trend is to synthesize active power control (APC) capability which benefits from the fast response of the converter to change the active power production during a frequency disturbance. This paper introduces a proposed APC algorithm for PMSG VSWT in order to imitate the response of a conventional synchronous generator. The proposed APC method uses two auxiliary torque control loops; the first is the emulated inertia control loop based on the effective inertia constant which depends on the wind power produced, and the second is the droop control loop. Those two loops extract the instantaneous active power needed for primary frequency regulation from the stored kinetic energy in the rotating mass of the PMSG VSWT. The design of the Proportional Integral (PI) controllers for the Generator Side Converter (GSC) is based on the Decoupled and Diagonal Internal Model Control (DDIMC) method. Simulations using MATLAB/Simulink were performed under different wind speeds, with a frequency drop caused by the insertion of large loads. Comparative results were presented to verify the effectiveness and the robustness of the proposed APC method.