Parallel operation of electric power systems is an actual task, since it allows increasing the reliability of energy supply and the quality of electricity supplied to consumers. Modern technical devices implemented on the basis of power electronics, which are developing intensively, allow solving qualitatively many problems of modern energy. In this paper, a new approach to the circuit realization of the FACTS device is substantiated, which had a wide range of applications in the electric power industry and would be characterized by high energy and functional indicators. The concept and operation principle of a multifunctional three-phase high-voltage converter of modular type is considered, in which are used of the transistors. The voltage converter is a multimodule structure of single power modules that are the same for all AC phases. This structure can be extended to obtain the required parameters for voltage and power. The proposed voltage converter can perform the following functions: reactive power compensation (STATCOM function), communication between the AC circuit and the DC circuit (rectifier), the connection between the DC circuit and the AC circuit (inverter), and when using a group of two three-phase converters it is possible to carry out a communication device between two circuits with different current and voltage frequencies (DC link - BtB), as well as communication between circuits with different values of the voltage (the function of the traditional autotransformer). Pulse-width modulation with a variable pulse repetition frequency is used in the converter, which reduces the converter's own losses at variable load and of that various voltage levels in the power circuit. A mathematical model of a three-phase AC / DC converter has been developed, and the operating mode has been studied for a load variation in the range from zero to the nominal value. It is shown that the spectrum of the current harmonics generated by the converter is at the level permitted by normative documents.