An investigation of DC-link voltage and temperature variations on EV traction system design

DC-link voltage and temperature variations are critical issues when designing an electric vehicle (EV) traction system. The paper presents an assessment of electric vehicle power-train options based on the Nissan Leaf vehicle, which is taken as a benchmark system providing same validation for the study. The Nissan Leaf traction machine is evaluated and performance assessed by considering DC-link voltage and temperature variations. An alternative traction machine design is proposed to satisfy the specification. The vehicle power-train is then modified with the inclusion of a DC/DC converter between the battery pack and DC-link to maintain the traction system DC-link voltage near constant. Additionally, inclusion of a supercapacitor system presents a much tighter input voltage specification but still doesn't completely eliminate the issue. Finally, installing a DC/DC converter to mitigate the faulted operation of electric machine drive is reported.