Three-phase unbalanced power flow to deploy line voltage regulators in RES-rich distribution feeders: a real case study in Milano, Italy

In the era of energy transition, low-voltage distribution networks are becoming increasingly pivotal. However, technical issues related to voltage can arise due to the increasing electrification of end uses and the spread of distributed generators. On the one hand, voltage stability is a prerequisite for a stable, effective, and efficient power system operation; on the other hand, low voltage distribution networks are influenced by various types of single-phase or three-phase customers (industrial, commercial, and residential), resulting in unbalanced power flows, which cannot be overlooked, to have accurate knowledge of network state. This paper presents a real case study to address the unbalanced issues of low-voltage feeder by applying three-phase power flow algorithms. In particular, a three-phase power flow approach has been developed to address unbalanced voltage issues and explore potential solutions. The approach combines the backward-forward sweep method and the current injection method to simulate results before and after deploying a line voltage regulator. Additionally, a genetic algorithm is applied to test whether the voltage issue can be resolved without deploying the line voltage regulator, but just optimally balancing the power flow in the three phases. The proposed approach has been applied to a real study case in Milano, on a renewable energy source rich low voltage feeder affected by several under-voltage issues.