Thyristor-Based DCCB With Reliable Fast Reclosing Protection Ability by Restoring Capacitor Polarity

Abstract

Lots of dc circuit breakers have been proposed for protecting medium voltage dc (MVDC) systems. However, they normally have one or more following limitations: low operational reliability, lack of controllability, lack of reclosing protection ability, power supply required, and high construction cost. To overcome these problems, a novel thyristor-based dc circuit breaker (TCB) is proposed in this paper. The proposed TCB could break the bi-directional current actively and reliably. In the reclosing process, the polarity of capacitor in the counter current loop could restore automatically to the initial state, and the auxiliary thyristor could be turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> naturally. As a result, the proposed TCB guarantees reliable fast reclosing protection ability on the premise of no additional pre-charge power supply. Moreover, all thyristors of the proposed TCB could be turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> by voltage drop of the anti-parallel diodes, and the overvoltage problem caused by reverse recovery process of thyristors is eliminated, which further enhances the reliability of TCB. The detailed topology introduction, parameters designing guidelines, scaled-down experimental results, and comparative study of the proposed TCB are all presented.