30 kW Power Boost System for Drive Trains for Electric Vehicles Based on Supercapacitor Technologies

Abstract

The goal of the master thesis is to design, dimension and construct a power boost system for the drive trains in electric vehicles, utilizing supercapacitor technology. In order to build the system a supercapacitor bank and a converter has been constructed. The system has been designed to be used in the new Think electric vehicle, and each part of the converter has been dimensioned according to information provided by Think Technology. The master thesis is limited to the design and construction of the power boost system, and the implementation, interfacing and control of power sharing have not been dealt with. The supercapacitor bank and the converter are built based on analytical computations and simulations. The supercapacitor bank can store up to 100 Wh and is built from 90 series connected cells rated 1500 F each. The bidirectional DC DC converter is based on a standard intelligent power module with three legs in a bridge configuration and three inductors. An interleaved switching sequence is selected for the operation of the legs and each IGBT is capable of switching 150 A at 600 V. The thermal management of this module is solved with the use of a heat sink with fans for forced air flow. The inductors are made from amorphous alloys and copper foil, achieving an inductance of 0.25 mH and a maximum current rating of 100 A. Voltage smoothing capacitors and measuring devices have also been implemented in the converter design. The results presented are held to be accurate, all though measurements gathered are affected to a certain degree by noise in the system. Based on tests of the various components, it is concluded that the power boost system is an up to date system and has achieved the design goals of delivering 30 kW for 12 seconds. Some tests are yet to be completed in order to make sure that the system works in continuous operation. Further work based on this master thesis should include more extensive testing on the system, and perform an optimization of the supercapacitor bank and the inductors. The intelligence for optimized load sharing must be created, and a communication interface with the power control unit in the Think electric vehicle must be made.