Ultracapacitors and Cascaded Multilevel Converters in Motor Drives: Application of Hybrid Cascaded Multilevel Converter with Energy Storage Elements in High Power Systems

Ultra-capacitors are increasingly becoming important as onboard energy storage in electric ship, and electric and hybrid electric vehicles where they assist in providing peak power during acceleration and absorbing regenerative energy. While active research is continuously being pursued in the use of ultra-capacitors as energy storage in motor drive applications, the topologies reported so far in literature have drawbacks such as limited real power compensation with no reactive power compensation,and reactive power compensation with no real power compensation. DC-DC converters have significant advantages in low to medium power applications, but degraded performance for high power applications such as in electric ship. Cascaded multilevel converters have been at the center of research for the past several years due to their inherent advantages in medium and high power applications, especially in motor drive applications.This research proposes two hybrid cascaded multilevel converter (HCMC) topologies and the corresponding control strategies applied to motor drive, interfacing both dc sources and capacitor energy storage elements.