As the core equipment of HVDC（ High Voltage Direct Current） transmission system

the reliability of MMC（ Modular Multilevel Converter） converter valve is related to the safe and stable operation of the whole transmission system. Considering the influence of working condition

the reliability model is established and the weak components are analyzed for the traditional HVDC transmission MMC converter valve based on the fault tree analysis method. Firstly

the failure rate models of IGBT and diode are established considering the influence of operating conditions. Then

the fault tree model of the MMC converter valve is established by the fault tree analysis method

and the corresponding reliability index formulas are obtained considering the power module and peripheral control protection system. Finally

the failure rate of each component is calculated according to the reliability index formula

and the weak components of the MMC converter valve are identified based on the probability sensitivity and the critical sensitivity indexes. The results show that the failure rate of the MMC converter valve and component is biggest under the conditions of rectifier and inverter

and the failure rate is smallest under pure reactive power condition

the IGBT module and the power supply are the weak components of the MMC valve

and the performance of the MMC submodule has the most significant influence on the reliability of the valve.