Ultracapacitor energy storage system for material handling applications based on short primary linear induction drives

Short primary linear drives on passive track are advantageous in material handling applications, where high precision, long track and a closed path are required. This paper presents a linear induction motor (LIM) drive with short primary (moving windings), in which a contactless energy transmission provides the basic power and an ultracapacitor (UC) storage system provides the peak power. The system uses a bidirectional DC-DC converter between the ultracapacitor bank and the DC-link, to make sure that the ultracapacitor can store the braking energy and supply the peak power demanded by the active vehicle. A control strategy has been developed for controlling the ultracapacitor to deliver the peak of power, to charge, to protect against overvoltage and to recover the energy generated when the vehicle is braking. Experimental results of the short primary linear induction motor and the bidirectional DC-DC converter are presented, and the control strategy is discussed.