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A three-phase dual-active-bridge (3p-DAB) converter is an attractive topology for bidirectional power conversion in high-power applications. However, conduction and switching losses are two main loss mechanisms that severely affect its efficiency performance, and adoption of any single modulation scheme or topology cannot minimize these losses over a wide operating range. For this purpose, a reconfigurable topology of the 3p-DAB converter is proposed in this article that utilizes a reconfigurable and tunable resonant network to offer multiple degrees of freedom in minimizing conduction and switching losses over a wide range of operating conditions. The converter is designed such that for 40–100% of the rated output power, it operates as a tunable 3p-DAB resonant immittance converter with its output power controlled by varying switching frequency and tuning the resonant frequency of a resonant immittance network to track the switching frequency. Below 40% of the rated output power, the converter transforms to a tunable 3p-DAB series-resonant converter with its output power controlled by varying the impedance of a series-resonant network while keeping the switching frequency and phase shift constant. The combination of both operation modes jointly leads to wide-range zero circulating current and soft switching of all the switches and, hence, a wide-range high-efficiency performance, as validated by the experimental results. [ABSTRACT FROM AUTHOR]

Switching loss and conduction loss are two main loss mechanisms in dual-active-bridge (DAB) converter and the degree to which they affect the efficiency of DAB converter depends on the chosen power modulation scheme. In general, no single modulation scheme will perform optimally under all operating conditions. In this article, a hybrid modulation scheme and a new DAB converter topology designed for its realization are presented. The DAB converter is designed to switch between two operation modes—dynamic frequency matching (DFM) for medium- to full-load condition and enhanced dual-phase-shift (EDPS) modulation for light-load condition. Under DFM modulation, a switch-controlled capacitor is used to tune the resonant frequency of an LCL immittance network such that minimum rms current is guaranteed by unity-power-factor operation under different load conditions, leading to zero backflow power, zero circulating current, and zero-voltage switching (ZVS) operation of all switches. Under EDPS modulation, zero backflow power, and ZVS operation of all switches are achieved. These advantageous features are critical to ensuring a high-efficiency operation of DAB converter. The proposed solution is experimentally verified using a 1.5-kW hardware prototype with efficiency exceeding 96% for all output power levels. [ABSTRACT FROM AUTHOR]