Research On Reliability Of Press-pack IGBT For HVDC Circuit Breaker

The Direct Current Circuit Breaker(DCCB)is vital to isolate the fault lines and interrupt current in the Voltage Source Converter High Voltage Direct Current(VSC-HVDC).The Press Pack IGBT in hybrid DCCB is a key to conduct current transfer and break fault current.The working condition of the hybrid DC circuit breaker is very different from the converter valve and the converter,whose key component is the IGBT device.Since the hybrid high-voltage DC circuit breaker only operates when the system fails,its operating frequency is low,and the current level of the press pack IGBT device is higher to the rated level.Depending on the position of the press pack IGBT device,the stress is different The IGBT device in the auxiliary breaker is subjected to continuous current while that in the main-breaker only needs to turn off the fault current when the fault occurs.That is,the failure modes of the Press-pack IGBT are different from the bonded-IGBT module which has been developed better so far.The main modes are the thermal failure caused by large current,the local thermal failure caused by uneven current distribution,and the uneven pressure distribution.Local mechanical failure,fretting wear,etc.It is mainly studied in the paper that the failure mode and failure mechanism of the Press-pack IGBT device under the condition of DC breaker and its equivalent reliability test method.Firstly,according to the working process of the hybrid DC circuit breaker,the stresses of the Press-pack IGBT device are analyzed.It is concluded that the possible failure mode of the Press-pack IGBT under this condition is the overheating failure caused by high current and the skin effect.The two failure modes is simulated by the finite element simulation software,it is found that the continuous flow of IGBT devices in the auxiliary breaking switch will withstand continuous high temperature and the temperature rise will continue until the fault occurs or overhaul,which may cause overheating failure.When it turn off the fault current,the longer the turn-off process is,the higher the temperature rise of the chip is,and the chip temperature is small and the edge is large.The simulation of the multi-chip model shows that the thermal stress in the center is smaller than that of the outside,and the heat generated by the shutdown current increases according to the degree of unevenness.There is little high-frequency components in the current waveform,so it is unlikely to have a significant unevenness in the current distribution.Therefore,an equivalent reliability test method with current as stress and temperature rise as equivalent is proposed,so as to estimate the reliability of the Press-pack IGBT device under large inrush current with safe current level.