Three phase unbalance elimination in distribution system by optimal inverter dispatch of PCs

The increasing introduction of photovoltaic (PV) units into low voltage distribution system causes serious power quality issues, e.g. voltage variation and three phase voltage unbalance (VU) which limit the rating and number of further connections. Some conventional countermeasures such as on load tap changer, step voltage regulator, etc. have been applied to mitigate the voltage problems. However, these methodologies might not be enough to cope with PV output fluctuation due to the limitation in the number of tap changing operations or slow response of tap changers. On the other hand, it seems promising to use PV inverter control to solve the problems when PV units are allowed to inject or absorb reactive power. In particular, there is a possibility that PV inverter control can contribute to VU problem even if they are connected with low voltage single phase networks. This paper proposed a comprehensive inverter control strategy consisting of both reactive power control and active power curtailment to improve the operation performance of VU in medium voltage distribution network with high penetration of residential PV systems by minimizing network losses and active power curtailment with voltage quality constraints. The effectiveness of the proposed method was evaluated in consideration of solar insolation level which affects active power generation of PVs.