A study on compensation for voltage unbalance in distribution transformer areas considering three-phase load imbalance using hybrid PV-ESS inverters

To address voltage unbalance induced by three-phase load discrepancies in rural areas, this paper proposes a voltage compensation technology utilising hybrid photovoltaic-energy storage (PV-ESS) inverters. Data analysis from 12 typical distribution stations indicates an average three-phase load unbalance of 18.7 and a maximum phase-voltage deviation of 7.2, contributing to a 35 rise in user-side equipment failure rates. The study employs a collaborative PV-ESS control strategy that dynamically modulates inverter output by monitoring three-phase currents alongside real-time active and reactive power. A three-month pilot verification involving 500 households in a distribution area demonstrated that voltage unbalance dropped from 15.3 to 2.1, the power factor improved from 0.82 to 0.96, line losses decreased by 12.8, and the user-side voltage compliance rate rose from 92.1 to 98.7. Through optimised charge-discharge strategies, the technology achieves a PV self-consumption rate exceeding 85, effectively mitigating heavy loads on distribution transformers. This study provides a quantifiable technical solution for rural grid voltage regulation, with empirical data validating its significant compensation efficacy.