In this master thesis, a project of the combined cycle power plant of a total power output of 690 MWel was elaborated. The power plant consists of two gas blocks, each of which contains a gas turbogenerator that generates 260 MWel, and of a steam block that contains a steam turbogenerator that produces 160 MWel. The gas and steam parts of the plant are connected in the process by a 3- pressure heat recovery steam generator that runs on exhaust gases from the gas blocks with a temperature of 600°C, while the gas turbines are powered by natural gas. To understand the thesis, the first part describes the work of individual processes, both gas and steam, which are then combined into a common process. This is followed by a brief description of several state of the art combined power plants in the world that stand out in terms of efficiency or power and also represent good environmental solutions. The first part also includes an analytical calculation of the combined plant that consists of a technical description of the system, a calculation of the energy balance of the gas part, which includes the calculation of natural gas combustion, and the energy balance of the steam part of the plant. Following the analytical calculation in the first part, in the second part, a previously analyzed computer model was made in the "EBSILON Professional" software, as well as the calculation of the heating surfaces of the heat exchangers in the heat recovery steam generator. Finally, the general steam generator plan and the layout drawing of the power plant were made.