The Calculation of Turn-off Overvoltages in a High Voltage dc Thyristor Valve

A method of calculating turn-off overvoltages in a high voltage dc thyristor valve, and a computer program to perform the calculations, are presented. The effects of the statistical distribution of storage charge among thyristors and of valve and system parameters on turn-off overvoltages are shown through results of calculations for a representative thyristor valve. These results are supported by measurements performed on a model valve. The techniques presented are useful for valve design, and for optimization of valve and system parameters. The results presented are valuable in clarifying the effects of important parameters on valve performance.