Time Series Variations of the Neutral-to-Ground Potential in a 4-Wire LV Network under Unbalanced Allocation of Rooftop Solar PV and Mitigation using Energy Storage

Abstract

Recently, there have been a significant increase in the number of single-phase rooftop solar photovoltaic systems in the low voltage (LV) distribution networks (DNs). High integration of solar PV units in future grids has the potential of imposing some adverse effects on the distribution networks. Detailed analysis of the future distribution networks is necessary for future distribution network planning and operation. In the traditional three phase network analysis, the neutral wire in the 4-wire LV is often ignored or merged into the phase admittances. However if the effect of the neutral wire is not addressed, the use of the traditional three phase analysis of a 4-wire system may not accurately reflect the actual operation on the power systems. A high neutral current due to the unbalance operation of the power system may overload the neutral conductor, interfere with communication infrastructure, reduce the sensitivity of fault relays and increase the neutral to ground voltage. This paper aims to investigate the variation of the neutral to ground voltage in a multi-grounded DN with varying load and PV production in a 24 hour period. A mitigation strategy using distributed energy sources is also provided to demonstrate the benefit of the distributed storage in the LV networks. A study using the time series power flow has been performed on an Australian Distribution Network and the results have been reported in this paper.