Powertrain modularity

Neutral-point-clamped multilevel converters are a suitable solution to the implementation of low–medium voltage and power applications at present, thanks to their intrinsic superior voltage and current quality. The conventional configurations of these converters present uneven power loss distribution, causing thermal stress in some power semiconductors, which weakens the power converter reliability. To overcome this, an implementation of the neutral-point-clamped multilevel converter based on a switching-cell array is introduced, adding redundant conduction paths on one side and more options to distribute the switching losses on the other side. An active thermal control is proposed to balance the temperature distribution in the converter. A four-level converter has been implemented to evaluate the proposed solution. The experimental results show that the proposed implementation and active thermal control presents an enhanced temperature distribution in the converter and, therefore, reduced thermal stress and better reliability

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.