Alleviation of Neutral-to-Ground Potential Rise Under Unbalanced Allocation of Rooftop PV Using Distributed Energy Storage

A high penetration of one-phase rooftop solar photovoltaic (PV) units with unbalanced allocation can create considerable neutral current and neutral potential rise in low voltage (LV) four-wire multigrounded distribution networks, even with balanced loads. Because of the limitations of traditional strategies to mitigate the combined effect of load and PV unbalance, this paper proposes the use of distributed energy storage to reduce the neutral current and neutral potential under a high penetration of unbalanced rooftop solar PV allocation. A power-balancing algorithm based on charge/discharge control is developed to continuously adjust the power exchange with the grid to mitigate the neutral current and neutral potential rise, while minimizing power drawn from the energy storage. A dynamic model of the integrated PV-storage system is developed to investigate the dynamic performance of the proposed strategy. An Australian LV distribution system is used to verify its performance and the results are presented.