Powertrain modularity

The Dual Active Bridge Converter topology is widely recognized for its high power density in high-power applications, enabling soft switching and achieving high efficiencies in both buck and boost operation modes. However, under conventional phase-shift modulation, operation at light or no load results in hard-switching and high effective currents, leading to increased overall losses, one of its main drawbacks. These issues have been primarily addressed by implementing complex modulation strategies, leveraging from the multiple degrees of freedom in the control of the converter power, particularly the inner and outer shift angles of its bridges. Contrary to the traditional approach, this work proposes the modulation of the series inductance of the DAB converter by implementing a switched inductor, aiming for a simplified modulation strategy. The proposed method effectively achieves zero current under no-load conditions and significantly reduces effective currents at light loads compared to the traditional phase-shift modulation approach. Although an in-depth comparison with other modulation schemes is required, this work represents a stepping stone in the analysis of the topology and the comprehension of its trade-offs.

The study of multilevel dual-active-bridge (DAB) converters has garnered significant attention in recent years thanks to their advantages with respect to the conventional two-level (2L) DAB; namely, its greater performance and its capability to operate at higher voltage. The analysis of the converter high-frequency inductor current (𝑖LiL) is crucial, for instance, to compute its root mean square (RMS) value, required to estimate the conduction losses in the converter. The mathematical expression of 𝑖LiL is piecewise and multiple variations, i.e., modes, exist depending on the modulation parameter values. This increases the complexity of converter performance analytical study. Thus, a more practical and generalizable expression of 𝑖LiL current is desirable. This paper proposes novel compact analytic expressions for the instantaneous and RMS inductor current in the 2L-NL DAB converter, leveraging binary functions to define the piecewise intervals and to identify the mode as a function of the modulation parameter values. The proposed method paves the way for more simple and computationally efficient DAB performance optimization software tools that allow exploring any given converter structures and modulation strategies.