Voltage Control of PV-Rich LV Networks: OLTC-Fitted Transformer and Capacitor Banks

Due to the increasing adoption of domestic photovoltaic (PV) systems, the use of technologies such as on-load tap changer (OLTC)-fitted transformers, capacitor banks, and remote monitoring are being considered to mitigate voltage issues, particularly in European-style low voltage (LV) networks. Depending on the control strategy, however, the effects on customer voltages and control actions (e.g., tap changes or capacitor switching) can vary significantly. This work presents a framework to assess the performance of different OLTC-based control strategies in terms of voltage compliance with the standard BS EN50160 and the number of control actions. Three control strategies are proposed: constant set-point (CSC), time-based (TBC) and remote monitoring-based (RMC). A week-long Monte Carlo analysis is carried out considering a real UK LV network, three-phase power flows, different PV penetrations and seasonality. Results show that the TBC outperforms the CSC but at the expense of more tap changes. Due to the enhanced visibility, the RMC significantly increases the PV hosting capacity whilst limiting tap operations. Finally, when feeders have contrasting voltage issues, capacitor banks are found to provide additional flexibility and allow higher PV penetrations. These findings are expected to help the industry determining the benefits from OLTC-based solutions in future LV networks.