Primary frequency control of DFIG-WTs using bang-bang phase angle controller

A bang-bang phase angle controller (BPAC) was proposed in this study for the primary frequency control of doubly-fed induction generator-based wind turbines (DFIG-WTs). Dynamics of the internal voltage of a synchronous generator (SG) and that of a DFIG-WT were investigated in frequency deviation events. A BPAC was designed to regulate the phase angle obtained with a phase-locked loop directly, which enables the rapid active power control of the DFIG-WT. The BPAC signal is fed into the active power regulation loop of the pitch angle controller, which is expected to help rotor speed recovery and prevent secondary frequency drop. The small-signal analysis was carried out for the closed-loop system, composed of the DFIG-WT and the external SG-based power system, to verify the stability of the overall system. Simulation studies were undertaken on a wind power penetrated multi-machine power system, through which the primary frequency control performance of the BPAC was verified.