Voltage Unbalance and Overvoltage Mitigation by Using the Three-phase Damping Control Strategy in Battery Storage Applications

The constantly decreasing prices of the battery storage systems make them a very attractive solution for mitigating over voltages and voltage unbalance in low voltage grids with high penetration of renewable energy resources. A centralised storage device, connected at the end of the feeder can be a very effective solution for dealing with over voltages. The classical positive-sequence control strategy is usually employed in these devices to ensure a power exchange between the grid and the battery and vice versa. Nevertheless, the voltage unbalance cannot be mitigated by the classical control strategies. In this article, a modified three-phase damping control strategy is used to discharge and charge the battery storage system. This control strategy has an improved resistive behavior towards the zero- and negative-sequence components which mitigates the voltage unbalance by injecting or drawing asymmetrical phase currents. Thus both power quality problems are mitigated.