Medium-voltage distribution grid planning considering the flexibility of distributed energy storage

Abstract

The integration of battery energy storage system (BESS) solutions, particularly those connected to the medium-voltage (MV) and low-voltage (LV) networks, can significantly increase the flexibility of distribution network operation. Compared with conventional reinforcement solutions, BESS can increase the network capacity to integrate renewable energy sources and provide grid support functionalities for congestion management, Volt/Var support and backup power supply. This study evaluates the impact of BESS in the expansion of distribution networks considering two complementary business cases: one where the distribution system operator (DSO) operates the BESS and another where the consumers in a self-consumption scheme own the BESS. A technical-economic analysis for a 20-year planning horizon is performed for different MV networks to evaluate the effectiveness of BESS to eliminate branch's congestion and to improve the continuity of supply, which is measured by the reduction on the expected energy not distributed (EEND) index. Simulation results for the Portuguese reality have shown that while owning a BESS is an economically viable option for the DSO to handle congestions in the MV network, the cost-effective alternative to reduce the EEND is to foster distributed storage coupled with local production.