Primary Frequency Reserve Providing Strategy of Doubly-Fed Induction Generator Wind Generation Using Rotor Inertia Characteristics

For power grids with a high penetration level of wind power generation, stochastic wind speed variation adversely affects the frequency stability. A variable-speed wind turbine generator would deloads its output by shifting the power operating point to provide frequency response. Because the wind speed variation directly affects the calculation of the operating point, difficulties arise in securing a reliable amount of the frequency response. This paper proposes a control scheme of a doubly fed induction generator (DFIG)-based wind generation providing the primary frequency reserve (PFR), which can improve its reliability and flexibility even with a continuously varying wind speed. To achieve these objectives, the proposed scheme employs a de-loaded operation control loop associated with the rotational inertia characteristics of the DFIG. In addition, a static gain-based droop control loop is employed to release the required amount of active power from the system operator. In the proposed scheme, the optimal operating point for de-loaded operation varies more smoothly than it does in a conventional scheme by using the rotor inertia characteristics. The performance of the proposed control scheme is demonstrated using an EMTP-RV simulator under various wind speeds. The simulation results indicate that the proposed scheme significantly improves the frequency support capability of the DFIG in both the process of securing and providing the PFR.