슈퍼커패시터용 Dual Full-Bridge 양방향 DC-DC 컨버터의 스위칭 손실 최소화 기법

Abstract

Abstract

This paper deals with the minimization of switching loss of a dual full-bridge bidirectional DC-DC converter for supercapacitor. Nowadays, renewable energy sources such as wind generation and solar energy, have been moved into spotlight. On the configuration of the micro-grid, those renewable energy sources are the key factor. A renewable energy source has a slow response time for abrupt load change. It is difficult to use as a high power quality electrical source. Therefore, it is necessary to compensate the slow response of the source to compensate the slow response characteristics, energy storage systems with fast charging and discharging performance such as flywheel or supercapacitor are added to that renewable energy system. Supercapacitor has lots of advantages such as long life and high charging efficiency. With these advantages, supercapacitor is spotlighted as one of the compensation device. In this paper, the supercapacitor is used to compensate the slow response characteristics of a fuel cell. In order to implement the compensation system effectively bi-directional DC-DC converter is needed. The major contents of this paper is the minimization of the switching loss of the DC-DC converter. Dual Full-Bridge Bidirectional DC-DC converter operation is divided in to the idling, charge and discharge modes. In idling mode, simulations are carried out with the supercapacitor which maximum voltage is 50 V. It is found that the soft switching can be achieved as far as the supercapacitor voltage is below 94% of the maximum voltage in idling mode. Therefore, the switching loss in the mode can be reduced by controlling the upper limit of the supercapacitor voltage. In case of charging mode, the switching loss can be minimized with proper switching pattern, and the switching loss in discharging mode can be minimized with soft switching. Simulation and experimental results show that the switching loss is reduced considerably.