PhD student Anuj Maheshwari with Advisor A. Banerjee

Drive-train efficiency and power density are crucial for improving the range of electric vehicles. Variable-pole induction machines (VPIMs) have been shown to be a viable replacement for permanent magnet motors. They can achieve the torque-speed requirement of electric vehicles, even at high speeds, without oversizing the drivetrain (see Figure 1).

Figure 2. Torque speed characteristics of VPIM at 100% battery SOC (blue), 50% battery SOC (red) and 20% battery SOC (yellow).

However, a dc-dc converter is needed to meet the torque-speed requirement when the battery voltage drops during battery discharge. Instead of using a separate fully rated dc-dc converter, dual use of an onboard charger to boost the dc-link voltage while the EV is running is proposed. The architecture is shown in Figure 2. The onboard charger is reconfigured into a partial-power processing converter to control the dc-link voltage using a double-pole double-throw (DPDT) switch. The proposed architecture both removes the need for a separated dc-dc converter to increase the drive train power density and enhances efficiency, as the converter processes only part of the power consumed in the motor. This research is supported by POETS (Power Optimization of Electral-Thermal Systems).

Figure 2. Proposed architecture which uses onboard charger as a partial power processing converter to regulate the inverter dc-bus during motoring mode. The DPDT switch connects the charger to the inverter dc-bus or the grid depending upon the operating mode.