Modeling and Optimal Tuning of Hybrid ESS Supporting Fast Active Power Regulation of Fully Decoupled Wind Power Generators

The frequency stability of the power system is challenged by the high penetration of power electronic interfaced renewable energy sources (RES). This paper investigates the improvements of the frequency response of fully decoupled wind power generators (FDWG) by proposing a novel generic model implementation of ultracapacitors (UC) within a hybrid scheme in real-time simulations of wind power plants. UCs are selected as ideal power sources in fast active power-frequency control due to their high power density and fast-reacting speed. Batteries and UCs combined hybrid energy storage systems (HESS) are formed to complement their characteristics. Droop-based and frequency derivative-based control and virtual synchronous power (VSP) are the selected control strategies to support power system frequency stability. The best trade-off between frequency performance and HESS cost is found by solving a proposed optimization problem formulation. The proposed optimization problem is used to define the HESS size and the controller parameters. The optimization results show how the fast active power-frequency response is enhanced by the fast UC power injection. It also shown that VSP leads to faster frequency support than the droop-based control and the frequency derivative control.