A review on the application of D-FACTS devices for power quality optimization in distribution networks

The new distribution network is an advanced power system built upon the traditional power network, which integrates distributed renewable energy sources, energy storage systems, and intelligent power electronic equipment. Unlike traditional distribution networks that only manage stable loads, the new distribution network faces dual challenges: the second-level power fluctuations from photovoltaics and the time-domain aggregation effects of electric vehicle charging loads. These factors lead to a high penetration of power electronics and increased system volatility, giving rise to significant power quality issues, including voltage fluctuations, violations of voltage limits, and three-phase imbalances. Existing on-load voltage regulators and reactive power compensation devices in the distribution network are insufficient to fully address these issues. In contrast, D-FACTS (Distribution Flexible Alternating Current Transmission System) devices have the potential to mitigate these problems and are increasingly recognized as an effective solution for power quality enhancement. This paper first reviews the power quality issues and mechanisms caused by the large-scale integration of photovoltaics and electric vehicles into the distribution network. Subsequently, it provides a detailed analysis on the topology and regulation principles of D-FACTS devices that can address these challenges. The paper also compares the performance of these devices and identifies the specific power quality problems each device can manage. Finally, based on future development needs, the paper proposes further research directions to provide theoretical foundations and practical guidance for the application and advancement of D-FACTS devices in the new distribution network.