The performance of a shipboard power station, which is a typical large-scale and complex system, relates directly to marine safety. To guarantee ideal performance, control system should be able to maintain the frequency and terminal voltage of electrical network stable in both steady states and transient processes. However, even for a well-tuned controller, in some special cases, its configuration wouldn't be appropriate. If there is a mechanism that is able to detect the variation of topology of electrical network and assist the controller to prepare for it, it could facilitate the working of marine electrical engineer. To realize this idea, a project named as ldquoresearch on control methods for onboard electrical networkrdquo, is now under research. This paper is the first part work of this project and focuses on building a framework for marine power system. Based upon this framework, further researches about topology supervision and controller mutation are carried on. The mathematic models for onboard power system, their realization in Matlab, and some issues that attentions need to be paid to during the simulations are elaborated in this article.