재차단이 가능한 새로운 반도체 차단기에 관한 연구

Abstract

Abstract With the development of IT industry in modern society, sensitive loads that require high power quality are becoming more widespread. Furthermore, it is a tendency that a lot of distributed generators susceptible to natural phenomena is being widespreadly installed. Thus if quick isolation of grid faults can not be performed, serious damages may occur because of rapid increase of fault current and thereby consequent electrical fires. In addition, after the first breaking of fault, if the fisrt breaking state remains for a long time without quick reclosing, additional economic losses due to long power outages may occur. For this reason, the operating duty condition of circuit breaker (IEC-62271-100) prescribes that reclosing and rebreaking of the cirrcuit breaker can be performed repeatedly. Thus this paper proposes two new SSCBs, that is, a new AC SSCB and a new DC SSCB that can perform the required operating duty of reclosing and rebreaking. It also verifies the operating characteristics by simulation and experimental.

1. DC Solid-State Circuit Breaker Although SCRs require commutation circuits for turn-off operation, they are suitable for use in DC SSCB because they are relatively cheaper and their on-state losses are smaller compared with other semiconductor switching devices. However, since the existing SSCBs using SCR were developed for use in AC grids, it is difficult to directly apply them to DC grids. Therefore, this paper proposes a novel DC SSCB with simple structure and rebreaking capability. Since the proposed DC SSCB has the capability of limiting short-circuit current, the current ratings of related SCRs can be reduced, thus resulting in possible selection of low-specification device and reduction of system cost. Also since all the SCRs containd in the proposed DC SSCB operate under ZCS or ZVS due to L-C resonance, switching losses are very small.

2. AC Solid-State Circuit Breaker This paper proposes a new AC SSCB that can perform the operating duty of reclosing and rebreaking without additional device. The proposed SSCB can perform the reclosing and rebreaking operation regardless of the load conditions because the proposed AC SSCB can charge its related capacitors even in hard situations where short circuit fault continues. Also, since quick reclosing is possible with simple control, economic losses due to long power outages can be reduced. When compared with the conventional AC SSCB, the proposed AC SSCB is cheaper by reducing the number of contained varistors and by using low-priced resistors.