Overview of Battery-Integrated Modular Multilevel Converter Topologies for Automotive Applications

The rise in global temperatures due to greenhouse gas emissions has led to a transition to alternative energy carriers especially in automotive applications. A key component in this transition is the battery pack, which contains several parallel and/or series-connected cells. The available energy and power of the battery pack are determined not only by the cell type, size, and configuration but also by the battery management system. To improve the control and energy utilization of the pack, battery-integrated modular multilevel converters (BI-MMCs) are presented. Five BI-MMC topologies for three main battery-integrated system configurations, namely, 3-phase, 6-phase low voltage, and 6-phase high voltage systems are evaluated for a 400 kW 40-ton commercial vehicle. The evaluation includes a comparative assessment of the number of submodules, battery, capacitor, and semiconductor losses for all BI-MMC topologies with 1 to 12 cascaded cells per submodule against a conventional 2-level inverter that is the benchmark. Furthermore, a performance matrix is developed for all BI-MMC topologies, which includes the total efficiency and the total number of submodules. The evaluation shows that most 6-phase and 3-phase BI-MMC topologies have higher efficiencies than the 2-level inverter. Furthermore, 6-phase BI-MMCs have higher efficiencies than the 3-phase BI-MMCs, but it comes with increases in complexity and cost. However, the complexity is also an advantage as it increases the controllability of the pack that can contribute to a longer life for the pack.