Adaptive Modulation of Resonant DAB Converters for Wide Range ZVS Operation With Minimum Reactive Circulating Power

Resonant mode dual active bridge (DAB) bidirectional dc–dc converters using either an inductive–capacitive–inductive ( LCL ) or a capacitive–inductive–capacitive ( CLC ) ac-port network offer several performance benefits compared to more conventional nonresonant filter DAB topologies. This includes a reduction in the circulating power between the two bridges, which consequently enables the conduction loss to be minimized and the physical converter volume to be reduced. However, these gains also require that soft-switching is maintained, which is very challenging to achieve across all operating conditions, particularly at light loads. This article investigates the zero-voltage-switching (ZVS) capability of resonant mode DAB converters, applying Fourier analysis to the converter modulation patterns to quantify the ZVS boundaries analytically. The resulting analytic formulations also quantify the DAB real and reactive power flows, which subsequently enables the identification of modulation conditions that improve the converter's soft-switching and reactive circulating power flow behavior. The analysis is verified using detailed time-domain PSIM simulations matched to experimental DAB converters equipped with both LCL and CLC filters.