Frequency variations in hybrid renewable energy network with integrated storage

Increasing penetration of renewable energy sources into the electrical grid, with intermittent and fluctuating supply, leads to frequency variations that are excessive in nature. This paper demonstrates the use of energy storage devices as a solution to reduce these variations. A hybrid network of conventional and renewable power sources consisting of a gas plant, a wind farm, an electrochemical battery, and a pumped hydroelectric storage plant is modeled. The network uses a load-frequency control model, interconnected with storage systems that are used to contain frequency variations within the band of ±1 Hz. A detailed methodology for the design of a nonlinear model for a sodium sulfur (NaS) battery is provided for this function. The model is validated with experimental data from a privately owned wind farm.