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

This paper derives and discusses the superiority of a simple dc-link capacitor voltage control configuration for multilevel neutral-point-clamped converters with any number of levels. The control involves n − 2 control loops regulating the difference between the voltage of neighbor capacitors. These control loops are inherently decoupled, i.e., they are independent and the control action of one loop does not affect the others. This method is proven to be equivalent to previously published approaches, with the added advantages of increased simplicity and scalability to a higher number of levels, all while imposing a lower computational burden. The good performance of such control is confirmed through simulations and experiments.

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.

Multilevelπ π-type and ANPC converters without flying capacitors and clamping diodes are emerging candidates for industrial applications due to their simple structure, less number of devices, and better harmonic performance. However, the voltage balancing difficulty is the key issue of these topologies similar to diode-clamped topology under conventional PWM methods. The unbalance of capacitors voltages may affect the system integrity and stability, and may degrade harmonic performance. To sort out this issue, a simplified virtual vector PWM method to balance the dc-link capacitors voltage of four-level three-phase π -type and ANPC converters is presented in this paper. Simulation results show how easily and efficiently the proposed method can control the voltage of the capacitors for different modulation index values under balanced and unbalanced loads.

This deliverable reports the selection of the optimum power devices for implementing the SCAPE high-voltage switching cells, after a literature review and commercial availability check. In addition to suitable electrical characteristics, the selection of candidates considered the suitability and availability of bare-die components for their subsequent chip embedding process. Two SiC MOSFET references have been selected and samples have been obtained for an initial test campaign (GeneSiC G4R12MT07. 750V – 12 mΩ and Wolfspeed CPM3-0650-0015A. 650V – 15 mΩ). For the development of the low-voltage switching cells of the auxiliary SCAPE converters, GaN HEMTs from EPC will be selected. The deliverable also includes a prospective and literature review about power device emerging technologies.