The article is dedicated to the group of converters with variable modular structure, the use of which eliminates inefficient operation of a converter at a minimal load and ensures the necessary power reserve under a load close to the maximal. Inefficiency of the group converters of a permanent structure may occur at a minimum load, in particular if the modules are used as stand-alone inverters with an excess reactive power compensator, which in this mode distorts considerably the quality of the output voltage curve. For this reason, in case the power supply is organized by a group of inverters and the total power of the modules is much larger than the current load power, it is advisable to change the module structure, depending on the load. The algorithm of an automatic determination of the optimal structure of the modules is presented. It is realized due to switching of the converter modules in real time. The structural optimization is implemented automatically according to two criteria: the degree of compliance of the modular structure of a converter with the necessary power reserve and the degree of compliance with the power limits. Algorithms were developed for determination of the optimal sequence of the switching modules according to the additive criteria (time transients, total power of modules, involved in switching). The mathematical models are based on the elements of the theory of fuzzy sets and optimization on graphs. The effectiveness of the algorithms was tested using the developed computer model for the system with a variable structure for a five module converter.