Research on Parallel Application Technology of High-Power Thyristors Under Surge Conditions

The peak current of high-power thyristors applied in pulse power technology under surge conditions reaches tens of kA, and the current change rate reaches hundreds of A/µ s. When devices operate in parallel, small differences between them can lead to significant differences in current distribution between branches, posing a great threat to the safe operation of the devices. In response to this issue, this article focuses on the two processes of forward conduction and forced shutdown of high-power thyristors under surge conditions, and builds simulation models to analyze the impact of current sharing factors from three aspects: circuit topology, on state voltage drop, and branch stray inductance. The results show that in terms of circuit structure, the circuit connection method of series first and then parallel is completely symmetrical, which is conducive to improving the current sharing coefficient of parallel operation. For the on state voltage drop of the device itself, compared to the threshold resistance, the on state resistance of the thyristor has a more significant impact on the current sharing effect, which is a parameter that should be paid more attention to in the application process. Stray inductance is an important parameter that affects current sharing, especially in high current change rate conditions. The difference in stray inductance not only leads to a significant difference in the current between the two components during the forward conduction process, but also causes a difference in the current drop rate of the parallel components during the forced shutdown process, resulting in a redistribution of current between the two parallel components and a longer time interval for current zero crossing. Therefore, in high current change rate application conditions, the structure of parallel branches should adopt a symmetrical connection method to improve the current sharing coefficient and ensure the safety and reliability of device operation.