Hybrid HVDC Breaker

Historical era of HVDC was unable to form HVDC grid even though knowing the merits of HVDC system and main reason behind was that until no HVDC breaker is developed which fulfill the requirement of HVDC grid. Existing mechanical HVDC breakers are capable of interrupting HVDC currents within several tens of milliseconds, but this is too slow to fulfill the requirements of a reliable HVDC grid. HVDC breakers based on semiconductors can easily overcome the limitations of operating speed, but generate large transfer losses, typically in the range of 30 percent of the losses of a voltage source converter station. To overcome these obstacles, scientist developed a hybrid HVDC breaker. The hybrid design has negligible conduction losses, while preserving ultra-fast current interruption capability. This paper will present a detailed description of the hybrid HVDC breaker, its design principles and its operation. The use of semiconductors for electric power circuit breakers instead of conventional breakers remains an ideal when designing fault current interrupters for high power networks. The major problems concerning power semiconductor circuit breakers are the excessive heat losses and their sensitivity to transients. However, conventional breakers are capable of dealing with such matters. A combination of the two methods, or so-called ‘hybrid breakers’, would appear to be a solution; however, hybrid breakers use separate parallel branches for conducting the main current and interrupting the short-circuit current. Such breakers are intended for protecting direct current (DC) traction systems. In this thesis hybrid switching techniques for current limitation and purely solid- state current interruption are investigated for DC breakers.