Distributed Energy Storage Systems with an Improved Fuzzy Controller for Mitigating Voltage Unbalance on Low-Voltage Networks

Abstract

The growth of photovoltaic (PV) systems on low-voltage distribution networks can create technical issues such as voltage rise, voltage unbalance, unnecessary neutral current circulation, and reverse power flow. Usually, these happen with little fluctuation. However, they tend to fluctuate seriously because of the low clear sky index in Malaysia and they become more severe when the installation and distribution of single-phase renewable energy sources are rather arbitrary and not monitored by utility companies. To ensure effective operation of distribution networks with PV systems, an improved version of a three-phase fuzzy control algorithm for distributed energy storage (ES) systems is proposed. With this algorithm, distributed energy storage systems can control individual phase voltage to mitigate the voltage unbalance factor effectively, maintaining voltage magnitude without cutting any excess renewable energy. An experimental low-voltage distribution network with two 3.6-kWp PV systems was set up. A number of case studies under various generation and demand conditions were carried out to evaluate the performance of the three single-phase energy storage systems with the novel fuzzy control algorithm. The results show that the proposed algorithm can effectively coordinate the systems to mitigate voltage unbalance and maintain the voltage level of low-voltage distribution networks with PV systems.