Hybrid batteries combine cells of complementary chemistries, each offering distinct strengths, resulting in battery designs with intermediate features, tailored for each application. With the aim of contributing to the development of modular and scalable hybrid batteries, this paper proposes a novel hybrid battery configuration consisting of two different battery banks, each formed by three series-connected battery modules, and a four-level neutral-point-clamped dc-dc power converter to interface the two battery banks. A suitable operating principle, a modulation strategy, and a closed-loop control are conceived for the proposed system. The power converter enables bidirectional power flow between the battery banks, and it also enables a lossless battery module state of charge balancing, simply by regulating the contribution of each module to the total power transfer, as this is one of the degrees of freedom of the selected multilevel converter topology. Simulation and experimental results verify the feasibility and good performance of the proposed system, demonstrating a substantial regulation margin of battery module currents, even at high modulation index values.

Accurate aging assessment of switching power semiconductors in power converters is essential due to their critical influence on converter reliability and operational lifespan. Traditional aging evaluation methods rely on intrusive sensors embedded within the power devices, which complicate electromagnetic interference management and limit the practicality of real-time monitoring. This paper proposes a comprehensive digital-twin framework and a simple algorithm to assess the state of health (SOH) of SiC power devices in switching-cell-array based power converters. The digital twin replicates the system electro-thermal behavior from the existing converter control current and voltage measurements and the modulation parameters. The algorithm estimates the power devices on-state resistance through the digital twin outputs and easy-to-integrate temperature sensors within the converter leg printed-circuit board. The on-state resistance provides a direct estimation of the power devices SOH. This framework delivers real-time insights into the converter SOH and degradation patterns, allowing predictive maintenance strategies. The proposed health assessment strategy is validated through simulations.

A charger for two batteries connected in series is presented in this work. From the three-phase grid, the batteries are charged through a three-level neutral-point-clamped ac-dc converter in cascade with a three-level dual active bridge converter. The system provides galvanic isolation and allows bidirectional power flow. A simple control strategy to charge the batteries is presented, based on the regulation of the common-and differential-mode components of the batteries’ charging currents. With this control approach, each battery bank can be charged independently, allowing it to reach full battery bank capacity, even under different battery initial state-of-charge values or different battery nominal capacities. Moreover, the proposed control system also regulates the total dc-link voltage and the dc-link voltage balance in both dc-links of the system. The simulation results verify the feasibility of the proposed implementation and control system approach.

This paper presents a converter consisting of a dual active bridge built upon three-level neutral-point-clamped legs in order to synthesize a five-level medium- or high- frequency stepped waveform on each side of the transformer. Thanks to the modulation extra degrees of freedom, the transformer current harmonic content can be reduced (less magnetic losses) and the fundamental component of the transformer primary and secondary voltages can be adjusted to minimize the reactive power (less conduction losses). A modulation strategy and control scheme to regulate the dc-link capacitor voltage balance is proposed. The topology, modulation, and balancing control are validated through simulations.

This paper presents an efficiency analysis of a recently-published topology, the multilevel-active-clamped (MAC) topology. In order to assess the MAC topology, an efficiency comparison between a four-level MAC leg and a conventional two-level leg operating in low voltage is carried out. First, overall losses of both topologies are estimated. Then, experimental tests to measure their overall losses and their efficiency are presented. Finally, obtained results from the experimental tests are compared with the estimations to substantiate the analysis. The efficiency of the MAC topology is higher in all the switching-frequency range.