Studies toward a faster, stabler and lower losses transfer switch

Transfer switches will play an important role in the flexible, reliable and intelligent electrical energy delivery system (FRIENDS), which is a promising distribution system in the future. Transfer switches will be used for flexible operation of the distribution system and reduction of distribution losses in the FRIENDS system. Although transfer switches using thyristors are already used for power quality improvement, following studies are still needed: (1) transfer characteristics of the switch for various phase difference between two feeders and various power factor have not been studied; and (2) reduction of losses is needed. This paper shows a proper gate control scheme for transfer without causing circulating current. From a loss point of view, a hybrid configuration with mechanical switches and semiconductor switches is studied. Experimental results from the hybrid configuration are also shown in this paper