In recent years, computer-aided thermodynamic simulation assumed an important role in the design of power plants. In order to simplify and to facilitate the layout of thermodynamic cycles in the simulation, modularization of system components is required. The purpose of this study was to develop a modular combined cycle power plant structure in simulation technology and its implementation in the heat balance software EBSILON Professional. Using the concept of an object as per object-oriented programming and the general definition of a model, the properties of a module and its interfaces were defined. After examining and modeling selected existing combined cycle power plants, groups of plant components could be combined to equipment modules. With this approach it was possible to represent a maximum of combined cycle power plant models with a minimum of modules. In order to fully exploit the advantages of a modularized structure in the process calculation, a new component for automatic connection of the module interfaces has been programmed.