Enhanced frequency response strategy for a PMSG-based wind energy conversion system using ultracapacitor in remote area power supply systems
Conventional generators in wind-diesel hybrid remote-area power supply (RAPS) systems are likely to be heavily stressed during frequency disturbances due to poor frequency response of power electronic interfaced wind energy conversion systems (WECSs). Hence, it is imperative for the WECS to provide frequency support during frequency excursions. However, existing frequency control strategies are slow and will also impose severe mechanical/electromagnetic stress on WECSs. In this paper, frequency response strategies for the PMSG-based WECS are explored, and an enhanced frequency response strategy is investigated to regulate the RAPS system frequency jointly with the integrated ultracapacitors. The proposed short-term frequency response strategy utilizes a virtual inertial technique along with the supplementary droop control. Suboptimal power-point-tracking is also implemented at the PMSG to improve the active power reserve. The enhanced frequency response strategy can regulate the RAPS system frequency while alleviating high rate-of-change-of-power, and thus stresses on both the conventional generator and PMSG under frequency disturbances. Proposed control strategies are validated by both simulations and experiments.