A cyber-physical system is the integration of a physical infrastructure with a cyber infrastructure, which provides control over its physical counterpart. The goal is to improve certain aspects of the physical infrastructure, such as its reliability. The Smart Grid, in which intelligent cyber control is added to improve the operation of the traditional power grid, is a prime example of a cyber-physical system. Quantitative models are needed in order to better understand the benefits and risks of adding intelligence to physical systems. To this end, we have developed an integrated cyber-physical reliability model, with a focus on the Smart Grid as our case study.
By understanding operational semantics of the Smart Grid, we analyzed the effects of failures in both the physical and cyber infrastructures. Moreover, for the cyber infrastructure, we studied several failure modes, which reflect the various ways in which the cyber components can fail, both in hardware and in software. We further refined our model by using software fault injection in the cyber infrastructure, which revealed additional failure modes.
The original contribution of this dissertation is the development of a quantitative reliability model for the Smart Grid, which reflects the effect of physical failures (transmission line outages) and cyber failures (software errors) in a unified model. This work can be extended to other cyber-physical critical infrastructure systems, and serves as a first step towards development of a generalized quantitative reliability model for cyber-physical systems --Abstract, page iii
