Voltage imbalance investigation in residential LV distribution networks with rooftop PV system

Voltage imbalance is a common power quality problem in power grids. The penetration of the single-phase PV system will affect the voltage imbalance indicator of the low and medium voltage distribution network. Since there is no adequate monitoring point in the distribution network, the evaluation method for assessing the voltage imbalance indicator is of paramount importance, given the stochastic nature of the location and classification of the PV panels. In this paper, the effect of power injection from a single-phase PV rooftop system in the low voltage distribution network on voltage unbalance was studied, by performing a simulation by using the NEPLAN Power Systems Simulation Software. The results show that for the balanced PV case for balanced/unbalanced load, an average power injection of approximately 3 kW–7 kW per bus on the LV distribution grid would not push the voltage unbalance beyond the 2–3% limits. In a worst-case scenario, where all of the PVs would be connected to the same phase and a maximum unbalanced load would be applied, the power injection per bus may be up to 3 kW and 4.5 kW before reaching the same voltage unbalance limits. Whereas in the case of changing the length of the line, the voltage imbalance changes approximately in a direct proportion with the change in the length of the line.