Abstract
This paper investigates the interruption capability with the aid of a parallel capacitor branch and exploits the single current direction through a series thyristor with the DC system. Two DC current interruptions are introduced by providing superimposed oscillatory currents. The first one is that the capacitor branch (capacitor and inductor) is continuously connected in parallel with the system where the capacitor is charged from the system during the normal operation. Due to fault occurrence, the capacitor branch including an inductor produces an oscillatory current that can make zero crossing through the series thyristor. However, the interrupting current is unfortunately after the second oscillatory peak current that the fault resistance can damp the oscillatory current. By changing the charged capacitor polarity, the second breaking concept is introduced depending on a precharged capacitor by the system voltage and then injecting the oscillatory current using a self-triggered additional thyristor. The current interruption initiation is attained using the DC current raising. The interruption performance is evaluated using a thyristor-based converter DC system.