This project investigates computer simulation methods for power electronic systems. Power electronic systems are essential sub-systems in key energy conversion application areas such as electric vehicle powertrains, marine propulsion, aerospace, renewable energy and power distribution. They are complex assemblies of electrical, mechanical and thermal management sub-systems and components. Optimal system designs require understanding of electrical, electromagnetic and thermal interactions between components - the way in which a component is integrated during system manufacture can have a significant effect on system performance and lifetime. Computer models that can be passed from component to system manufacturers are needed to allow effective digital system design optimisation. Existing models provided by power electronic component manufacturers are limited to circuit models which cannot account for the 3D system geometry, component placement, or manufacturing processes used. 3D CAD component models could be provided but to be useful, detailed and high-resolution models are needed which would expose IP. Complex Finite Element simulations would then be needed to evaluate these models and these simulations are extremely computationally expensive - potentially taking days to complete. Historically, models have been used to evaluate worst case electrical and thermal performance given expected operating conditions but increasingly, lifetime and reliability is of concern. Predicting worst-case electrical and thermal performance is straightforward because maximum power and ambient temperature operating points can easily be defined and simulated. Predicting lifetime and service intervals for components is more difficult as component wear-out is determined by accumulated stress and damage sustained under normal operating conditions - different conditions within the acceptable performance envelope can give drastically different service lifetimes. Wear-out also occurs over long time periods which necessitates long simulations, if the models used are not incredibly efficient then this further increases the amount of time required to run the simulations. The research undertaken will propose a new Real-Time Virtual Prototype (RTVP) model architecture for power electronic components. The RTVP models utilise reduced order modelling algorithms that allow the models to simulate over 1000 times faster than conventional Finite Element models. These models can then be coupled together and simulated very quickly (faster than real-time in certain scenarios) to allow system manufacturers to evaluate system performance, including wear-out and reliability, over extended time periods. Furthermore, the models can be configured to hide sensitive design and performance data which will enable component manufacturers to release accurate, 3D models simulation models of their components whilst protecting sensitive IP. These models can be combined to produce full digital "virtual prototypes" of system designs, eliminating the need for construction and testing of physical prototypes, leading to reduced design costs and increased system performance.