Bidirectional thyristor-based active clamping technology for turn-off overvoltage of DC solid-state circuit breakers
Traditional metal oxide varistor-based passive overvoltage clamp techniques only limit the peak overvoltage to more than twice the DC bus voltage.As a result,the rated voltage utilization of semicon-ductor switches in solid-state circuit breakers is reduced,which reduces the efficiency,power density and cost advantages of solid-state circuit breakers.To address this issue,based on the analysis of traditional overvoltage clamping techniques,an active overvoltage clamp technique based on the bidirectional thyris-tor was proposed.Based on the feature that bidirectional thyristors are easier to drive,can be turned on/off in both directions,and can self-turn off under milliamp current,the structure of the overvoltage clamp circuit was simplified,and a dedicated uncontrolled RC drive circuit was designed.Therefore,the over-voltage suppression effect,hardware cost and volume were optimized.The working process,parameters design and devices selection of the overvoltage clamp circuit were analyzed in detail and illustrated with examples.Finally,a comparative experiment on turn-off overvoltage at a bus voltage of 600 V was con-ducted.The results show that the proposed scheme ensures better overvoltage suppression while its cost is reduced.
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