Optimal Placement and Sizing of Distributed Energy Storage for Loss Minimisation in the Enugu Distribution Network

This study develops and validates an optimisation methodology for the placement and sizing of distributed battery energy storage systems to minimise real power losses in the Enugu Electricity Distribution Company's medium voltage distribution network in Enugu State, South East Nigeria. Distribution networks with high resistive losses, such as EEDC's predominantly aged low cross-section feeders, represent a major source of inefficiency that increases generation dispatch costs and reduces the effective capacity available to serve consumer demand. An accurate load flow model of the EEDC Enugu Metro area medium voltage network was constructed in ETAP using field-verified feeder topology, conductor impedance, and transformer ratings. Annual load profiles at each distribution transformer were derived from available billing data supplemented by probabilistic load synthesis. The optimal placement problem is formulated as a multi-period non-linear optimisation, minimising total annual network losses subject to bus voltage limits, feeder thermal limits, and battery capacity constraints. The problem is solved using a hybrid algorithm combining particle swarm optimisation for candidate location selection and sequential quadratic programming for capacity sizing. The validated model is run for six candidate storage scenarios. Results indicate that placement of three battery storage systems totalling 4.5MWh at the identified optimal locations reduces peak hour resistive losses by 18.3 percent and daily energy losses by 11.7 percent across the modelled network. Capital cost recovery from loss reduction value is estimated at 8.2 years at current electricity tariff levels. Keywords: battery storage, loss minimisation, optimal placement, distribution network, Enugu.