Development of a novel ultracapacitor electric vehicle and methods to cope with voltage variation

In this paper, we introduce a novel DC-DC converterless ultracapacitor electric vehicle (EV) and propose methods to cope with voltage variation of ultracapacitor. In general capacitor applications, a DC-DC converter is used to suppress ultracapacitor's voltage variation. In the case of the proposed EV, the ultracapacitor storage system is directly connected to an inverter for the purpose of weight, space utilization, and energy efficiency. It is shown that the inverter, which is specially designed to cope with voltage variation and operates without any problem between 50 V - 200 V. Dq axis vector control for the interior permanent magnet synchronous motor is applied to achieve wide-speed operation and cope with voltage variation.