An auxiliary power distribution network for an electric vehicle.

Abstract

The University of Canterbury purchased a modern Toyota MR2 sports car with the intention of converting it into an electric vehicle. Similar to the common combustion engine vehicles, electric vehicles requires power and control systems to operate the 12Vdc auxiliaries, such as lights, indicators and wipers. Traditional technology results in a large number of wires in the wiring harness. To reduce the number of wires, an alternative method is to use a pair of control lines and a universal power connection around the vehicle. This power and control system is named the "Power Distribution Network" and it is implemented by using multiple power converters and a differential control system. This thesis presents the design, implementation, and test results of the Power Distribution Network for the MR2. The 300Vdc nominal battery voltage is converted to an intermediate voltage of 48V. This configuration is considered more efficient than the usual 12V distribution system since smaller and lighter wires can be used to carry same amount of power. The Power Distribution Network operates off the 48V intermediate voltage, and provides 12V output power to drive all the auxiliaries in the vehicle. The Power Distribution Network also has the ability of detect faults from the auxiliary loads as well as turn on and off these loads. The Power Distribution Network is implemented with two major systems: the Auxiliary Power System, which consists of a 360W Cuk converter with current limiting control circuits to step-down voltage from the 48V intermediate voltage to the 12V. The other system is the CAN Control system, it is developed using micro-controllers and standalone CAN controllers that control and monitor the auxiliary loads in the vehicle. The prototype Power Distribution Network is fully operational and has been tested with eight of 12V light bulbs which are used to simulate the auxiliary loads in the vehicle. Experimental measurements show that the prototype is able to successfully control the light bulbs under the full load condition. This confirms that in principle the Power Distribution Network is suitable as the power and control system for the auxiliary loads in an electric vehicle.