Control Strategy of Series-End Winding Single-Phase Integrated On-Board Charger System

Battery charger is an important equipment for electrical vehicle (EV) system. Different from conventional on-board charger (OBC) which is based on a dedicated power electronics converter for battery charging, grid-connected integrated on-board charger (IOBC) is based on existing traction drive to charge the battery and can significantly reduce the cost and volume of the EV. However, conventional IOBC faces certain challenges and drawbacks. These include instability issues, unbalanced current stress, extra motor loss in charging mode and potential adverse effects on the permanent magnet (PM) within the motor. By applying novel series-end winding motor drive (SWMD) for traction, there is a freedom of 0-axis current to utilize for IOBC and solve the problems. This article explores the use of this novel IOBC structure, investigates its working principle, and highlights its advantages in practical applications. With the SWMD, single-phase grid can be connected to one phase winding and realize zero-torque charging mode for the battery. Furthermore, the grid charging current can be assigned to d-axis current and 0-axis current in the motor. This allocation results in a substantial reduction of the d-axis current, which in turn minimizes the impact on the permanent magnet (PM). Rational configuration of current in d-axis and 0-axis can also optimize the current stress of legs and motor loss. A prototype SWMD system has been successfully developed and implemented, allowing for the validation of the proposed IOBC operation and control schemes through a series of experiments.