Comparative Analysis of Isolated and Non-Isolated On-Board-Charger Topologies for Electric Buses

In the future, transport electrification is expected to become prevalent, with battery electric buses (BEB) becoming a relevant mode of transportation in urban environments. BEBs are typically charged at depots using AC connectors, as they are equipped with on-board-chargers (OBC). Ideally, the chosen OBC should offer the highest efficiency while minimizing size, therefore, there is a need for safety and risk reduction of electric shocks during battery charging. In this context, this work compares a non-isolated buck-boost topology considering a symmetric design approach to reduce common-mode leakage currents with an isolated dual-active-bridge (DAB) converter for charging BEB. The comparison is performed in terms of efficiency and size of magnetic components at different switching frequencies. Results indicate strong potential for the non-isolated topology at switching frequencies above 50 kHz, primarily due to a significant reduction in the weight of the magnetic components. For switching frequencies below this value, the DAB converter presents advantages in terms of magnetic components weight while maintaining similar efficiency levels.