Integrated Electric Motor Drive and Power Electronics for Bidirectional Power Flow Between the Electric Vehicle and DC or AC Grid

This paper presents an integrated traction machine and converter topology that has bidirectional power flow capability between an electric vehicle and the dc or ac supply or grid. The inductances of the traction motor windings are used for bidirectional converter operation to transfer power eliminating the need for extra inductors for the charging and vehicle-to-grid converter operations. These operations are in addition to the vehicle traction mode operation. The electric powertrain system size and weight can be minimized with this approach. The concept has been analyzed with finite-element- coupled simulation with dynamic analysis software. Experimental results are also provided with electric machines. The interleaving technique has been used with the inductors to share the current and reduce the converter switching stresses.

I. Introduction

The multipurpose use of the power electronic converter in the drivetrain of an electric vehicle has become an interesting topic for minimizing the system size, weight, and cost. The weight and size of the converter are challenging issues in the case of on-board chargers which otherwise provides the flexibility of charging the vehicle anywhere. The vehicle is not driven during the period of charging, and hence, the traction motor and inverter of the powertrain can be used as an integral part of the converter. The windings of the traction motor can serve as the inductors of the power converter along with power devices of the traction inverter to transfer power. The power converter of the electric vehicle can draw power from the grid when it requires, and also can deliver power to the grid in the peak time when the grid needs power. During a significant part of the day, most vehicles remain idle in the parking lot when the integrated power converter can use the traction motor and its drive to transfer power to the grid.