Improving LV networks hosting capacity via the use of a neutral point compensator - a Monte-Carlo analysis

Due to the rapid increase in residential PV capacity, it gets more and more difficult for an LV grid to absorb power at peak hours due to overvoltage issues, causing concerns to DSOs and prosumers who are temporarily unable to inject power into the grid. Monte-Carlo simulations were performed with a parametrized LV feeder model and with input parameters representing typical feeder characteristics in Belgium that could lead to overvoltage occurrences, in order to gain insights on the effectiveness of using a zigzag transformer as neutral point compensator to mitigate the issue. The simulations’ outputs highlighted that such mitigation measure can bring significant voltage excursion (|Vph-N- Vnom|) reductions. Reductions typically comprised between 14% and 28% have been observed when the zigzag transformer is located near the end of the LV feeder, depending on the zigzag transformer impedance considered. The corresponding reduction of the risk for overvoltage occurrences was comprised between 41% and 77%. The neutral point compensator is only as effective as the unbalance level in the LV feeder, which is linked to the distribution of 1ph PV inverters and 3ph PV inverters on the feeder. The neutral point compensator can thus be regarded as a promising mitigation measure against PV-related overvoltages but with limited effectiveness depending on the unbalance level of the PV production.