Analytically constrained ZVS operation to reduce commutation losses for high boost dual active bridge converters

Dual Active Bridge (DAB) converters offer an unmatched capability to transfer energy in either direction between two DC sources, especially when they are operated under Zero Voltage Switching (ZVS) conditions. However, the parasitic commutation inductance within the bridge phase leg devices can still lead to significant energy losses at device turn-off despite operating under ZVS conditions. These losses can become significant when one bridge has a low DC bus voltage and a consequential high magnitude output current. This paper shows how harmonic decomposition analysis can be used to constrain the bridge circulating currents to their minimum possible values at the point of phase leg commutation while still ensuring that ZVS operation is maintained. This can be used to improve the overall DAB performance under low voltage, high current operating conditions of one DC port. The capability of the theoretical analysis process is confirmed by matching experimental results for a reference DAB system.