Fuzzy-logic based Adaptive Control of Distributed Energy Storage Systems for Simultaneous V/f Regulation

High penetration of renewable energy in distribution networks brings both voltage and frequency fluctuations to the power grid. Conventionally, system frequency and network voltage regulation are separately considered. However, due to the relatively low $X/R$ ratio of distribution lines, frequency regulation and voltage regulation by distributed generation units are not decoupled. To this end, this paper presents a fuzzy logic controller (FLC) to coordinately and adaptively regulate system frequency and bus voltages using distributed energy storage systems (DESSs). The complex power from the DESSs and their interfacing converters are effectively utilized for simultaneous voltage and frequency regulation. The proposed method is demonstrated on the 7-bus distribution network, and the simulation results verify that it can adaptively and coordinately regulate voltages and frequency within operating limits.