Full-capacity wind turbine with inertial support by optimizing phase-locked loop

This paper proposes a novel inertial control method based on optimizing the dynamic response of phase-locked loop (PLL) of full-capacity wind turbine (FCWT). Different from the typical inertial control strategy with PD controller, the proposed method utilizes the phase-tracking error provided by the optimized PLL to modify the rotor speed references without detecting the grid frequency or calculating the frequency derivative. In order to realize the expected inertial response characteristic, control parameters of PLL should be optimized, and the phase-locked loop error (Δθ) should be introduced to the speed reference. The controller design follows the principle that the WT can fast response and participate in stabilizing the grid frequency based on the large amount of rotational kinetic energy stored in the rotor when frequency fluctuates in grid. With this control strategy, the kinetic energy is released and transformed to the grid directly to improve frequency stability of power grid. Simulation model was built in MATLAB/Simulink and simulated results demonstrate the feasibility and correctness of the presented control method.