Modelling and control of a triple-active-bridge converter

This study proposes a systematic approach to model and control a triple-active-bridge (TAB) converter for electric vehicle on-board charger applications. An innovative generalised-harmonic-approximation (GHA) modelling method is proposed to accurately predict the instantaneous current and voltage waveforms. Based on the GHA modelling, a control strategy for a TAB converter is proposed, which enables the power flow from grid to two batteries with high conversion efficiency while achieving zero-voltage switching operation. Compared to the conventional phase-shift modulation, the proposed control method achieves an extended operating range of simultaneous charging operation mode, especially under the unbalanced load conditions. As a proof-of-concept, a 600 W prototype is built and tested. The experimental results are presented including waveforms of different operation modes and efficiency measurements. The peak efficiency of the TAB converter under the G2B mode is measured as 97.6%. The experimental waveforms exhibit good agreement with the waveforms obtained through GHA modelling.