Research on Dynamic Voltage Balancing of Series Connected Thyristors in Auxiliary Oscillation Zero-Crossing Circuit

As a mature power semiconductor, the thyristor is widely used in high-power electrical systems. However, its performance and type selection are still worth discussing in some unconventional applications. In this article, the dynamic voltage balancing the performance of series connected thyristors in an auxiliary oscillation zero-crossing circuit designed for a 10 kV/100 kA Quench Protection System (QPS) is discussed. This pulse power circuit contains a bidirectional switch composed of four thyristor stacks, which are used to inject reverse current into the parallel vacuum circuit breaker (VCB) to interrupt the dc circuit. It is proven by both analysis and experiment results that although there is a high di/dt conduction requirement, the ordinary power thyristors are proof that it is more suitable than pulse power thyristors on this occasion for their better transient reverse recovery voltage balancing performance. The phenomenon is explanted by physical principles and measurement results.