A New Approach to Model Reverse Recovery Process of a Thyristor for HVdc Circuit Breaker Testing

In the HVdc circuit breaker testing process, a thyristor is used to generate high current for the testing purpose. However, the reverse recovery process (RRP) of a thyristor can induce a significant overvoltage problem, which jeopardizes the reliable operation. It is important to model the RRP of a thyristor. The existing modeling methods usually omit the stray inductances in the circuit, which cannot describe the hard-switching process accurately. Therefore, this article proposes a novel method to model the RRP, considering the stray inductances. There are mainly three original contributions. First, the physical mechanism of the RRP is analyzed, describing the internal charge behavior and dividing the RRP into two stages. Second, this article provides a novel trigonometric exponential (TE) model of the thyristor voltage and current with analytical equations. Third, the extraction method of model parameters is also provided based on external circuit parameters and thyristor characteristics. In order to verify the proposed modeling method, a 1 kV/830 A IGBT-based circuit breaker is implemented with a thyristor to initialize the current. The experimental results show that the negative peak voltage induced by the RRP is as high as 4.26 kV, and the proposed TE model can precisely predict the overvoltage with a relative error of 7.51%.