Research on 1100-kV/5500-A Ultra-High Voltage Thyristor Valve Key Technology and Its Application

As direct current (dc) voltage and current increase to 1100 kV and 5455 A, respectively, ultra-high voltage (UHV) thyristor valve will be in complicated electric, magnetic, thermal, and mechanical environments. First, we analyzed the internal mechanism of damping characteristics and accurate internal relationship between electromagnetic transients of damping circuit and proposed its determination method. We developed a correction function of reverse recovery charge for thyristor valve under different working conditions, subsequently. Based on that, we proposed a calculation method for thyristor junction temperature and constructed a model for analyzing thyristor stress. Dielectric test was performed using dummy load and a method was proposed for determining dummy load parameters. The designed UHV thyristor valve successfully passed the full set of tests according to IEC60700-1 standards. Additionally, it has been applied in the Changji-Guquan HVdc project, which possesses the highest voltage level and largest transmission capacity in the world.