Multilevel Converter-Based Charging Station for A Fleet of Electric Transit Buses

This paper introduces the idea of a multilevel converter-based charging station specifically designed for a fleet of electric buses. The proposed approach uses a cascaded H-bridge (CHB) converter as an active front-end rectifier to draw power from an ac grid. Each electric bus is connected to the dc link of the CHB cell and is equipped with an on-board charger based on a modular multilevel converter (MMC). The battery bank of each electric bus is divided among the submodules (SMs) of an on-board MMC, which can charge the battery bank as well as supply power to the electric drive. An electric bus fleet can be a backup during emergencies and provide support by feeding power into the ac grid as part of ancillary services. This paper presents the bidirectional power flow of the multilevel charging station for this purpose. The simulation results, and analysis of the combined operation of CHB and MMC to charge the battery bank of an electric bus are presented to verify the proposed concept.