Reliability Analysis of Shore-to-Ship Fast Charging Systems

This paper presents a reliability assessment of Shore-to-Ship Sharging (S2SC) systems with focus on the two most common topologies of ac and dc charging. In the proposed reliability model, the Markov chain and reliability block diagrams are used to establish multi-state models of the system. In this regard, the state of system is defined as the maximum transferable charging power into the onboard batteries from shore which can be comprimised by the failure of the individual compoents. As the results of Markov chain analysis, the probability of the operation states and Mean Time to The First Failure (MTTFF) are calculated. Further, to clearify the impact of the failure of the individual compoents on the charigng mission, an application-specific failure threshold is defined. Subsequently, two relibility indices, namely, Loss of Charging Expectation (LOCE) and Derated Charging Expectation (DCE) are introduced and computed using the calculated prbability tables and the defined failure threshold. The results from conducting such analysis for two case studies with ac and dc S2SC systems, shows how the studied dc charging system is more reliable than its ac counterpart.