Model-Based Risk Assessment of Power Converters: Case Study of On-Board Battery System for Railway

On-board energy storage systems for railway traction are becoming a clear trend for many new rail projects, both for retrofit and new designs. This has raised safety and reliability concerns in railway industry given the novelty of the technology. Reliability analysis is mostly based on detailed modeling of the physics of failure. However, it is thought for system optimization and does not consider catastrophic and human factor failures. On the other hand, risk assessment studies are widely used for identifying, analyzing and prioritizing all possible modes of failure. However, they are not based on systems models and are not extendable to other converter topologies or battery configurations. To overcome the limitations of the two aforementioned approaches, this article proposes a method for risk assessment based on systems models. The proposed methodology is applied to study the critical risks of using a multilevel converter topology integrating a configuration of two series low-voltage ($< $1 kV) traction batteries to the dc bus of a train. The proposed approach is directly extendable to any converter topology or battery configuration.