Power quality enhancement using a photovoltaic-integrated hybrid distribution transformer

Introduction: The increasing adoption of distributed generation and the integration of energy storage present considerable challenges to distribution networks, including voltage fluctuations, increased energy losses, and deteriorating power quality. Hybrid distribution transformers (HDTs) have emerged as an innovative solution that combines the robustness of conventional low-frequency transformers with the versatility of power electronics. By incorporating partially rated power electronics modules, these transformers offer enhanced flexibility and additional services to distribution networks, all while maintaining cost-effectiveness and improving reliability. Materials and methods: This study proposes a power electronic module that comprises an active front-end rectifier (AFR) and a modular multilevel converter (MMC) integrated into the high-voltage side of a transformer. A photovoltaic (PV) system is incorporated into the Direct Current (DC) link of a power electronic system, thereby supplying active power to the network. The performance of the control scheme was validated under different operating scenarios. Results: The simulation results show that the load-side voltage was maintained at 240 V in all studied cases, while the MMC output power varied from 1885 W under normal conditions to 3391 W during sag compensation and decreased to 380 W under swell conditions. The reliance on the AFR reduced because the PV contribution increased with sun irradiation and could provide all MMC power required. The concept was verified by a scaled-down experimental prototype that maintained the targeted 30 V peak load. Conclusions: The results demonstrate that, with less dependence on the AFR, the proposed HDT–PV configuration can enhance power quality and provide flexible voltage support.