The paper investigates the processes of steam pressure regulation in a boiler unit in order to increase the efficiency and reliability of its operation. The main purpose of the study is to develop a mathematical model that allows to describe the dynamic processes in the system accurately and determine optimal parameters of the pressure regulator. The objectives of the research include development of a model of dynamic processes, analysis of existing control methods and selection of optimal parameters to minimize pressure deviations. The research methodology includes modeling the processes of setting up a PI-controller (Proportional integral controller) by engineering methods, comparative analysis and evaluation of the results obtained during the synthesis of ACS (Automatic control systems) with a PI controller. After setting up and evaluating the qualitative characteristics of the regulator in question, it was concluded that this regulator had an effect on the effectiveness of automatic pressure control system in the drum. Taking into account the obtained numerical values of the quality criteria, it can be concluded that the selected tuning coefficients and the structure of the PI regulator guarantee the necessary properties of the pressure control system and meet all the requirements for industrial regulators. These results are important for improving the efficiency of operation of thermal power plants and reducing their energy and operating costs, which is important for energy sector and automated control systems.