Assessing the reliability of power electronic converter systems is an essential task. New generations of components and topologies will be deployed in industrial segments such as renewable energy and electric vehicles. Although the lack of experience feedback, the reliability of those converter systems may be estimated by assessing stress profile and using physics-of-failure models. This method is used in the assessment of a wind turbine converter reliability including the effects of the uncertainty in the lifetime model parameters. By using Monte Carlo method, this paper exhibits the strong impact onto the reliability function of the input parameters although their weak scattering.