Research on Reliability Life Model of Thyristor in HVDC Converter Valve System in High-altitude Environment

Under the high-altitude environment, air humidity, temperature, pressure, atmospheric neutron and other factors will affect related electrical equipment, it also brings difficulties to the reliable operation of HVDC transmission projects, especially the thyristor, the key device in the converter valve system. Establishing an accurate device life model considering the influence of specific engineering application environmental conditions is of great significance to improve the reliability of devices and the setting of operation and maintenance schemes. Based on the existing accelerated life test theory and the working characteristics of high-power thyristors, this paper builds a thyristor life test chamber at high altitudes. Through the long-term withstand voltage of all the tested thyristors, the actual running time of the breakdown thyristors is recorded, and finally the life prediction model between the thyristor failure rate and different bias voltages in the high-altitude environment is obtained. The model and test results show that the failure rate of thyristor is positively correlated with the applied bias voltage. The failure rate model of thyristor under voltage stress in high-altitude area established by this test can be used to calculate the failure rate of thyristor under different operating conditions of actual engineering in high-altitude environment, and it has important guiding significance for predicting the life and improving the reliability of the entire HVDC transmission system.