Iron birds of power facilities allow solving various functional tasks. The interaction with the hardware of these simulation benches relies on the computer model of an electric power system (EPS). This article considers the main aspects of computer-aided simulation of complex electric power systems. The dynamic mode calculation is presented as a sequential calculation of static modes at each sampling interval. The developed mathematical model of the system consists of mathematical models of its elements and a model of their interaction. The models of the elements are differential equation systems in the (d, q) frame of reference. The algorithms for calculating dynamic and static modes actively use the T-list and allow performing these computations in an optimal manner. The developed software has an expandable and flexible graphical shell. Java programming allows doing without integrative modules for full-scale and half-sized models and ensures high performance and the fulfillment of the cross-platformity requirement. The module for mathematically simulating electric power systems can be used not only as part of subsystems for testing gas turbine power plants, but also for other functional tasks of half-sized sectional simulation of electric power systems.