CESI (Centre Elettrotecnico Sperimentale Italiano) and AFCo (Ansaldo Fuel Cells SpA) have launched a joint project that aims at developing and demonstrating a small-sized hybrid system that combines the MCFC (Molten Carbonate Fuel Cell) technology with a microturbine (MTG). A 100 kW cogeneration power plant is under construction at the CESI site in Milan. The plant will be connected to the low-voltage electrical grid. Due to the high degree of technological innovation of this hybrid plant, a simulator has been developed as an important tool for process design support and plant automation definition (control system and plant procedures specification). The purpose of this document is to present the dynamic computer simulation model of the hybrid plant and some examples of application. In an experimental project of innovative nature, such a model supplies helpful information for the definition of automation procedures for correct and safe plant operation. These procedures can then be validated by simulation. The simulator also supports the project design verifying the dynamic behaviour of some critical components. The model has been developed using LegoPC (a CESI proprietary dynamic modular code) and LegoSim (an interactive real time environment developed by CESI integrating LegoPC with MATLAB-Simulink).