Unbalance Reduction in LV Networks with High PV and EVs via Droop-Controlled BESS

Abstract

Low-voltage distribution networks are experiencing increasing phase current unbalance due to the widespread installation of single-phase photovoltaic systems and electric vehicle chargers. These unbalance results in increased power losses, transformer thermal stress, and accelerated asset degradation. This article proposes a decentralized drop control method using three independent single-phase battery energy storage systems mounted on LV transformers. The proposed control scheme regulates the charging and discharging of each BESS based on the deviation between individual phase currents and the average phase current, while explicitly considering the state of charge limitation. This method relies only on local current measurements and does not require centralized communication. The effectiveness of the proposed method was validated using a real residential low-voltage distribution network with high PV and EV usage. Simulation results demonstrate a significant reduction in the current unbalanced factor, improved phase current symmetry, reduced feeder losses, and relief from transformer thermal stress. Technical and economic assessments further demonstrate that the proposed strategy is a more cost-effective alternative to traditional grid strengthening in low-voltage networks.