Parallel Operation of Frequency Converters

Abstract

In order to increase the power of three-phase squirrel-cage induction motors, with a limited amount of supply voltage, in practice, the parallel operation of several machines is often used to drive the working mechanisms. Depending on the type of working mechanism, the following three variants are possible: (1) the motors are interconnected via an elastic coupling, which is characteristic of a distributed arrangement of machines in space, (2) the motors are interconnected via a rigid coupling, whereby mutual variations in the speed of rotation of the machines are minimal, and (3) the usual solution when it is desired to increase the reliability and availability of the drive is a parallel design of the stator winding, i.e. a machine with a common rotor. The paper examines the most common design of an indirect frequency converter today and the methods and protocols with which converters communicate. A review is given of scalar and vector control of a machine with and without feedback on the speed of rotation in different operating modes. For the purposes of research, a model of a two-winding electric motor with a power of 2x5.5 kW was realized in the laboratory for electrical machines and drives of FESB. The components and operating principle of the 4-quadrant test bench used for generating different operating modes are described. Finally, the experimental results are presented.

Marin Despalatović

Full Professor | Department of Electrical Drives and Industrial Control

Full professor at the Faculty of Electrical Engineering, Mechanical Engineering, and Naval Architecture in Split, where he teaches courses Electric Machines, Electric Drive Systems, and Electromechanical System Modeling. His research focuses on power systems, energy storage, and smart grid technologies, with active participation in multiple national and international projects aimed at advancing energy infrastructure and improving system stability.