Advanced Management and Power Quality Performance of Hybrid Transformers in modern Distribution Networks

The increasing penetration of distributed generation and renewable energy sources in power distribution networks introduces operational challenges such as voltage fluctuations, phase imbalance, network congestion, and power quality issues. Traditionally designed for unidirectional power flow, these networks now require advanced solutions to ensure stability and reliability. This paper presents a novel 250‑kW hybrid transformer (HT) prototype, co‑developed by an industrial manufacturer and a distribution system operator (DSO), and deployed at a medium‑voltage distribution substation in Brindisi, Italy. The HT combines conventional transformer technology with fractional-rated power electronic converters to enable real-time power quality management and operational flexibility. Key functionalities include voltage regulation, reactive power compensation, phase load balancing, harmonic filtering, and active/reactive power flow control. Field results demonstrate its effectiveness in stabilizing load voltage profiles, and reactive power compensation, confirming its potential to enhance the hosting capacity, reduce renewable curtailment, and enhance feeder performance.