Field-circuit analysis of planar transformer at medium frequency for converter application

With the advancements in power electronics technologies and the momentum towards intelligent electrical energy management, there is an increasing demand for power grids to have additional functions. Solid-state transformer (SST) is a new type of power converter that is employed in microgrids to achieve miniaturisation and promising performance. It comprises an isolated DC-DC converter with planar transformer integrated in the high frequency AC stage. In order to study its applications at medium frequency, different converter topologies should be simulated and analysed. In this paper, planar litz wire is compared with solid conductor in the transformer embedded in HF-link isolated DC-DC converters. Its pros and cons are discussed in detail. Small signal equations for a phase-shifted full-bridge (PSFB) DC-DC converter have been also derived with its corresponding controller being designed. A DC-AC inverter is also designed and cascaded to the PSFB DC-DC converter for AC applications.