Design and Optimization with Litz Wire Version of PCB in Solid-State Transformer

The PCB winding-based transformer is renowned for its low profile, easy manufacturability, and cost-effectiveness. However, it encounters challenges in high-power applications due to substantial winding loss caused by the proximity effect in high-frequency currents. On the other hand, Litz wire is designed to handle high-frequency currents efficiently through its twisting and interweaving structure, making it suitable for high-power applications. Yet, constructing the Litz wire pattern within PCB winding poses a significant challenge due to its complex structure. This paper introduces a novel design and optimization method, presenting a Litz wire version of PCB for Solid-State Transformers. The construction of the Litz wire version of PCB is detailed, and the principle of the flux cancellation effect inside it is analyzed. A comprehensive optimization process is proposed for the design of a PCB Litz wire-based Solid-State Transformer. Results demonstrate that, compared to traditional PCB winding, PCB Litz wire achieves a 30% reduction in winding loss, significantly improves current distribution, and enhances thermal performance. To validate the concept's effectiveness, a prototype of a 1.6/1.05kV, 192kHz, 30-kW CLLC converter is built, demonstrating an impressive 99.0% efficiency with 6.8 kW/L power density.