Protection voltage calculation method for passive breakdown protection device of sub-module device

The invention discloses a protection voltage calculation method for a passive breakdown protection device of a sub-module, and the method comprises the steps: enabling a converter to achieve the breakdown through the overvoltage of the passive breakdown protection device connected in parallel with an AC port of the sub-module when a bypass switch of the sub-module refuses to operate, forming a short-circuit through-current state, and achieving the non-stop operation of a modular multi-level converter. According to the invention, the maximum voltage value under the operation condition of the sub-module, the sum of the breakdown voltage of the power device of the sub-module and the charging voltage increment of the peak current of the bridge arm during the closing period of the bypass switch of the sub-module are combined to obtain the protection voltage range calculation method of the passive breakdown protection device of the sub-module; the protection voltage value of the passive breakdown protection device