Total System Engineering of an All Electric Ship, a Discussion of Fundamental Issues

摘要

The complexity of today's ship systems exceeds capabilities of existing tools for "total system engineering". As the power of systems increases, lower order effects have substantial amounts of energy and that cannot be ignored. Converters in the 10's of megawatt range can produce 100's of kilowatts of losses in the form of heat, electro-magnetic interference (EMI), and mechanical vibration. Today's designer must take into account these interactions, as well as predict many other effects such as: system cost, reliability, environmental effects, health effects, and so on. These predictions span temporal ranges from microseconds, through days, to years. Existing system design tools are rule-based on the standards that are eroding in the face of characterization costs of new technologies and vanishing research recourses. Rule-based design is impossible if there are no parts that comply with the rules. Sample sizes are often too low to provide adequate engineering justification. Usually, several iterations are required to complete the design process because when all the components are determined, it is possible that the design does not behave as desired, or the requirements determined for each design stage were not accurate enough. The design process has to be bottom-up. After the components are determined, the behavior of the whole system has to be verified. However, complex systems can be simplified by applying advanced technology. Using intelligent controllers and partitioning the system based on the physics of the materials, components, and methods of manufacture can produce building blocks, which allow systems to be designed, built, and operated in a rational predictable manner. This paper analyzes the challenges of "All Electric Ship" Engineering and describes some new ideas such as a "relational" design process, enabled by physics-based modeling and simulation. Physics-based analysis, founded on the nature of the materials and their manufacturing processes, will enable statistics from all of industry to be garnered in support of engineering justification and reliability assurance. Instead of complicating the design, power electronics is used to simplify complex systems. The model will become the specification, replacing documents and reducing ambiguity. An establishment of public library with model-based specifications, standards, benchmarks, and validation tools is a cornerstone of this approach together with industry wide agreements on models subject to legal scrutiny. Paper also describes the Marine Industries Subcommittee activities in the development of new IEEE standards based on collective industrial experience and consensus for power electronics and Medium Voltage DC power systems on ships.