The ultra-high voltage active commutation converter based on series valve group of reverse blocking integrated gate commutated thyristors (RB-IGCT) is one of the key commutation equipment for constructing novel power system. The uneven distribution of voltage stress caused by inconsistent switching of valve arm devices can threaten the operational reliability of the devices

and on the other hand

it will cause excessive redundancy of devices in the valve arm

which resulting in increased construction costs for the converter valve. To this end

this article first analyzes the switching characteristics of IGCT devices

establishes the IGCT model based on physical characteristics

and verifies the model by experimental. Secondly

the study of the series voltage sharing characteristics of the subunit was carried out. The influence of the stray inductance

resistance and capacitance parameters of the snubber on the voltage sharing coefficient between devices under the condition of drive delay was analyzed. The selection range of the snubber parameters was given based on the premise of a voltage sharing coefficient of 5%. Finally

the "RCD+MOV" snubber topology was proposed and its effect was simulated and analyzed. The results show that the new topology has better voltage equalization effect. When the drive delay is 200 ns

the voltage non-equalization coefficient is only 2.59%

which is 64.7% lower than the original topology. This study has certain reference value for the future design of voltage sharing for IGCT series valve group.