This paper introduces a new set of methods to directly integrate ultracapacitor banks into cascaded multilevel inverters used for large vehicle propulsion. The idea is to replace the regular dc-link capacitors with ultracapacitors in order to combine the energy storage unit and motor drive. This approach eliminates the need for an interfacing dc-dc converter and considerably improves the efficiency of regenerative braking energy restoration in electric and hybrid vehicles. Utilizing the proposed modulation control set, the two cascaded inverters can have their dc voltage levels maintained at any ratio (even a noninteger ratio) or dynamically varied over a wide range without disrupting the normal operation of the electric motor. As an advantage, ultracapacitor voltage or state of charge can be freely controlled for braking and/or acceleration power management. An optimal regenerative energy management scheme is proposed based on the vehicle's speed range considerations. Detailed simulations verified the proposed methods.

Meeting Name

IEEE Industry Applications Conference/41st IAS Annual Meeting (2006: Oct. 8-12, Tampa, FL)


Electrical and Computer Engineering

Keywords and Phrases

Cascaded Multilevel Inverter; Energy Storage; Hybrid Converter; Hybrid Vehicle; Regenerative Braking; Ultracapacitor; Vehicle Power Management; Capacitors; Electric Motors; Electric Vehicles; Electric Drives; Supercapacitors; Motor Drives; Vehicle Driving; Propulsion; Inverters; Vehicles; Voltage Control; Energy Management; Electric Propulsion

International Standard Book Number (ISBN)


International Standard Serial Number (ISSN)


Document Type

Article - Conference proceedings

Document Version

Final Version

File Type





© 2006 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Oct 2006