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Design considerations for a three-port bidirectional DC-DC converter to be used in hybrid energy storage systems (HESSs) with the aim to increase the power transfer capability are discussed in this study. For this, an analysis of the power flow that allows obtaining the current waveforms is presented. Then, a loss model, that includes losses in semiconductors and the magnetic core, is proposed based as a function of the voltage variations in the energy storage devices considering all possible cases of power transference. The analysis reveals that it is possible to size the converter auxiliary inductances to reduce the converter currents and losses and therefore increase the power transfer capability. The analysis and the proposal presented in this study are validated using a 5-kW experimental prototype. Results show that it is possible to increase the converter transfer capability up to 80%.

Failures in power semiconductors of a dual active bridge converter are characterised considering open-circuit faults in diodes and transistors. A detailed electrical waveforms analysis to identify the main symptoms of the converter during normal and failure conditions is presented. Based on this analysis, a fault diagnosis strategy is proposed which is able to identify failures either in a diode or in a transistor as well as its location in the circuit. Finally, simulation and experimental results, using a prototype of 1 KW, are presented in this study to demonstrate the practical feasibility of the theoretical proposal.