Energy Efficiency of an Electric Vehicle Propulsion Inverter Using Various Semiconductor Technologies
In this Licentiate thesis, various solutions to improve the efficiency in the electrical vehicle
drive drive line such as in the propulsion inverter and in the electric machine, are proposed
and their benefits are quantified from an energy efficiency point of view. The efficiency
analysis is based on modeling of a power electronics inverter, an electric machine and a
battery in various drive cycles of an electric vehicle.
A solution to improve the efficiency in the electric machine is proposed. A loss minimizing
optimized current vector control is suggested for a PMSM which minimizes the total
machine losses. The solution has for the investigated electric machine up to 8% efficiency
improvement or 1.5% improvement in average efficiency of various drive cycles such as ECE,
EUDC and US06.
Several solutions are studied for the propulsion inverter. It is shown that by replacing
the ordinary silicon pn freewheeling diodes in the propulsion inverter with SiC diodes, an
average efficiency improvement of about 0.5 percent can be expected in various drive cycles.
Furthermore by replacing the Silicon IGBTs in the inverter with SiC MOSFETs, the drive
cycle efficiency in various drive cycles can be increased between 4 to 6 percents.
Finally a controllable dc-link voltage for the propulsion inverter is investigated in order
to qualify the energy efficiency gain for the inverter and the motor. Their drive cycle energy
efficiency improvement is 0.5 to 1 percent when using a SiC based inverter and 4 to 6 percents
for an IGBT based inverter.
Current vector control