Assessment of Voltage Balancing in Distribution Networks with Utility-Scale and Behind-the-Meter PVs Considering Service Transformers

The paper compares the mitigation strategy applied to eliminate the voltage unbalance in an active distribution network from a utility-scale PVs and Behind the Meter (BTM) PVs, while taking into account the constraints imposed by single-phase center-tapped secondary transformers (common in the North America distribution systems). An AC Optimal Power Flow formulation for the integrated primary and secondary distribution network is introduced to determine the reactive power absorption/injection as a control variable to minimize system-wide voltage unbalance. The analysis treats all nodes as critical, which corresponds to real-world scenarios. As most of the single-phase PV systems in the Low-Voltage systems is owned by a residential customer, the service transformers must be taken into account to evaluate the participation of single phase PV in mitigating the voltage unbalance. The findings of this study contribute to understanding the limitations and effectiveness of voltage unbalance mitigation strategies, considering the impact of secondary transformers. The results can assist distribution system operators and planners in making informed decisions regarding the integration and control of PV systems for voltage management in active distribution networks.