A Torque Fluctuation Suppression Method for an Integrated On-Board EV Charger Considering Grid and Switching Frequency Components

The integrated on-board battery chargers (IOBCs) that employ nine-phase permanent magnet synchronous machines (PMSMs) for electric vehicles (EVs) connected to a three-phase grid inevitably produce torque fluctuations during charging process. This undesired torque variation is the primary source of motor vibrations and noise, stemming from the interaction between the motor winding current (including switching frequency dc current and grid frequency current), the permanent magnet field, and rotor position. This article proposes a grid frequency torque fluctuation control (GFTFC) method and utilizes a modified dc-dc converter to suppress the switching frequency torque fluctuation. The system employs this proposed approach, offering the advantages of silent charging with low torque fluctuation at any rotor position. Additionally, the suppressed switching frequency current ripples reduce iron loss, permanent magnet loss, and inverter loss in the system. Simulation and experimental results are provided to validate the theoretical analysis.