A Modular Multi-Port Hybrid Solid-State Transformer for Large-Scale Renewable Power Applications

Offshore wind and solar energy have substantial attention for the generation of high-voltage ac (HVAC) and high-voltage dc (HVDC). However, traditional systems face application limitations due to low-frequency transformers and inefficient power converters. This article proposes a four-port solid-state transformer (FPSST) to enhance large-scale energy generation from renewable sources. The FPSST incorporates a modular multilevel converter to collect both medium-voltage ac and dc from wind and solar systems. Following this collection, high-frequency transformer-based dc/dc converters ensure galvanic isolation between ports by enabling a compact, lightweight and efficient design due to the advanced magnetic material. A cascaded H-bridges multilevel inverter produces HVAC with reduced harmonic distortion and precise voltage regulation. Moreover, a series-connected two-quadrant converter generates HVDC, providing a stable dc output through a discretised dc-link capacitor. The performance of the proposed FPSST is thoroughly investigated using the MATLAB/Simulink platform, which offers insight into system behaviour. Prior to experimental validation, an amorphous alloy-based high-frequency transformer is developed in the laboratory, and a 1-kW sealed-down FPSST is constructed. Simulation and experiment results confirm the feasibility and effectiveness of the proposed FPSST. Thanks to its compact, modular design, the four-port SST can be easily scaled, enabling both HVAC and HVDC generation from renewable sources.