Applying Steinmetz Circuit Design to Mitigate Voltage Unbalance Using Distributed Solar PV

Abstract

Distributed solar photovoltaic (PV) systems can contribute to voltage unbalance in electric power distribution networks. However, PV inverter control can also be used to help mitigate voltage unbalance. Steinmetz proposed a circuit design method to achieve voltage balance by controlling the reactances of three-phase delta-connected constant-impedance loads. The approach is simple, open-loop, and decentralized. In this paper, we explore the application of Steinmetz circuit design to the control of distributed PV systems, specifically their reactive power injections, to mitigate voltage unbalance. Simulation results show that Steinmetz circuit design can completely eliminate voltage unbalance at a particular bus if a three-phase delta-connected PV system is present at that bus. When single-phase PV systems (connected line-to-line) are distributed along a feeder and connected to different phases, Steinmetz circuit design can significantly reduce voltage unbalance but may not achieve perfect balance.