Coordinated Control of Three Single–Phase BESS Inverters Using Local Measurements to Mitigate Voltage Unbalance

This article proposes a control algorithm for single-phase battery inverters to provide voltage unbalance compensation in distribution networks with high penetration of photovoltaic panels and electric vehicles. A typical distribution system is studied to quantify the impact of single-phase loads and generating units on voltage unbalance levels, and identify the conditions that lead to the highest voltage unbalance. Voltage unbalance compensation is then performed by regulating active and reactive power exchange between three single-phase battery energy storage units and the power grid. The proposed control strategy consists of an upper level control system to coordinate the three units by sending active and reactive power reference signals, and a Battery Energy Storage System (BESS) control system to regulate active and reactive power exchange between each single-phase inverter and the grid. Simulation results show that the effectiveness of this approach depends on the location where the energy storage units are installed. The positive impact of the proposed methodology on balancing the power flow and reducing the transformer zero-sequence current is also demonstrated. Finally, Hardware-In-The-Loop (HIL) experiments are carried out to provide validation of the control algorithm in real-time.