Six-phase drive-based integrated onboard battery charger for electric vehicles considering zero-sequence circulating current elimination

The concept of the integrated onboard battery charger (IOBC) provides electric vehicles (EVs) with access to the integration of the drivetrain and the charger. In this paper, an IOBC based on a six-phase drive is studied. In the charging mode, the IOBC is equivalent to a paralleled three-phase voltage source rectifier (PTP-VSR) with common ac and dc sides. Such operation leads to a zero-sequence circulating current (ZSCC), which causes current waveform distortion and the resultant power loss. This paper proposes a novel ZSCC elimination strategy, which is in principle tied to finite control set model predictive control (FCS-MPC). By modifying the control set (CS), the ZSCC can be naturally circumvented without increasing the complexity of the control system. Furthermore, an enhanced phase-locked loop (EPLL) based on the second-order generalized integrator (SOGI) is proposed, by which, only sampling a line voltage is required. Finally, the effectiveness of the proposed strategy and EPLL are experimentally validated.