Topology and Magnetics Optimisation for a 100-kW Bi-Directional DC-DC Converter

Modern applications of high-power DC-DC converters can be found in the renewable energy, energy storage, and automotive industries, where they are used for on-board power trains and rapid charging systems for Electric Vehicles (EV). This paper presents an investigation into the optimisation of a high-power bi-directional DC-DC interleaved converter suitable for high-performance EV applications. Three topologies are considered for comparison - the three- and four-phase interleaved converter with discrete inductors (3P-DI and 4P-DI), and the four-phase interleaved converter with three Interphase Transformers (4P-IPT). The different topologies are compared through a comprehensive multi-objective design optimisation procedure for a 100 kW 300-750 V case study. It is shown that the 4P-IPT offers lower volume and higher efficiency than the 3P-DI and 4P-DI across a wide range of switching frequencies, with reductions in weight of up to 50% being possible at low switching frequencies. It is then demonstrated that magnetic cores with higher temperature limits and lower gap losses may enable the discrete inductor topologies to be competitive with the 4P-IPT in terms of power density and efficiency.