Optimal fuzzy logic control of energy storage systems for V/f support in distribution networks considering battery degradation

High penetration of renewable energy resources into distribution networks induces frequency and voltage fluctuations to the power grids. Unlike high-voltage transmission lines, the X/R ratio of distribution lines is relatively low, thereby frequency support and voltage regulation are closely coupled. Considering their coupling relationship, a rule-based fuzzy logic controller (FLC) is proposed in this paper for battery energy storage systems (BESSs) to coordinately provide bus voltages and frequency support. The membership functions of the FLC are optimized offline to minimize the frequency and voltage deviations using Pareto front criterion. Moreover, with a practical battery aging dataset, a battery degradation model is constructed to design fuzzy rules for prolonging battery lifetime. The proposed method is tested on the IEEE 33-bus distribution network and compared with benchmarking methods. The simulation results verify that the proposed method can simultaneously provide frequency and voltages regulation support to satisfy the operational limits while extending the battery lifetime.