Studies on Ultra-capacitor Based Energy Storage and Power Conversion System for Three-phase Electric Drives
Pages : 525-530
Most of modern controlled electric drive applications, such as lifts, cranes, and tooling machines are characterized by a high ratio of the peak to average power. In addition, such applications have high demand for braking at the full rated power. In ordinary drives, the braking energy which represents 30%–50% of the consumed energy is dissipated on a braking resistor. Apart, from this energetic issue, power supply interruption, input current quality and power conversion system are the additional issues to be solved. It has been long known that three-phase electrical equipment such as three-phase induction motors are significantly more efficient, economical and easy to control than their single-phase counterpart. Also, the sizes of three-phase motors are significantly smaller than its single-phase version with the same kVA rating. However, in many instances three-phase power is rarely available in the rural or light industrial areas due to the high cost of extending three-phase service. So the only available power in these areas is in the form of single-phase and there exists a need for phase converters for powering induction motor driven fans, pumps and other irrigation equipment. Some solutions have been proposed to convert a single-phase power to three-phase power. The ultra-capacitor with an interface DC-DC converter is used to store and recover the braking energy. Moreover, the DC bus voltage is boosted and controlled to be constant and ripple free regardless of the load and the mains voltage variation. In comparison to state-of-the-art solutions, the new solution has better performance, regarding size, cost and efficiency. The presented solution is theoretically analyzed and experimentally verified. The results are presented and discussed. All these solutions provide an efficient way to save the braking energy and improve the global efficiency of variable speed drive systems.
Keywords: Ultra-capacitor, Power Conversion, DC-DC Converters.
Article published in International Journal of Current Engineering and Technology, Vol.4,No.2 (April- 2014)