Comprehensive optimal photovoltaic inverter control strategy in unbalanced three-phase four-wire low voltage distribution networks

The continuous expansion of consumer-driven installations of residential rooftop photovoltaic (PV) systems causes serious power quality, notable voltage variations and unbalance, which limit the number and capacity of the further connections. The latent reactive power capability of PV inverters can increase the network PV hosting capability. This paper proposes both reactive power control and real power curtailment as a comprehensive inverter control strategy to improve the operating performance of unbalanced three-phase four-wire low voltage (LV) distribution networks with high penetrations of residential PV systems. A multi-objective optimal power flow (OPF) problem that can simultaneously improve voltage magnitude and balance profiles while minimizing network loss and generation costs is defined. The solution is found using the global solver based on Sequential Quadratic Programming (SQP) algorithm with multiple starting points in Matlab. Detailed simulations are performed and analyzed for typical operating scenarios over 24-hour period on a real three-phase four-wire unbalanced distribution network in Perth Solar City trial, Australia. Smart meter readings are used to justify the accuracy and validation of the network model and the proposed multi-objective OPF model.