Modelling and bi-level control design of a SiC off-board charging system for battery electric buses with V2G capability

The recent breakthrough of battery electric buses (BEBs) in cities is leading to an increased load demand on the grid. Hence, smart and efficient charging infrastructure is required. Emerging wide bandgap (WBG) semiconductors, such as SiC and GaN, will enable future charging systems to operate at higher switching frequencies and therefore increase the efficiency of the charging process, while smart control algorithms will introduce new features like grid-to-vehicle (G2V) and vehicle-to-grid (V2G) operations to optimize the charging behaviour. Therefore, this paper proposes the modelling of a SiC technology-based off-board charging system for BEBs and the design of its bi-level controller. The low-level control system is used to ensure the battery’s charging or discharging modes and to achieve the best total harmonic distortion (THD) and unity power factor (PF). Therefore, a linear and nonlinear simulation model are developed in MATLAB/Simulink to validate the PQ control theory-based performances. Additionally, a high-level charging management strategy (HL-CMS), based on a genetic algorithm (GA), provides an optimal charging (G2V) and discharging (V2G) scheduling for the entire charging/discharging process, considering the limits and requirements of the grid and bus operators. The results demonstrate that both controllers operate properly under different circumstances.