Analysis of the Control System for a Soft Starter of an Induction Motor Based on a Multi-Zone AC Voltage Converter

The development trends of the modern world of power electronics dictate the requirements for the use of AC voltage converters as soft starters for induction motors. A direct connection of the motors to the mains voltage negatively affects both the motor itself and the mains system as a whole due to high starting currents values, which entail, as a rule, more frequent accidents and shorten the drive system service life. Modern methods of motor acceleration are implemented in practice by means of frequency converters, which require the presence of both a rectifier and an inverter in the structure of the device. The paper presents a study of the control system of a multi-zone AC voltage single-stage regulator. The use of capacitive voltage dividers will also compensate for the consumed reactive power. The article analyzes the features of modern soft starters, describes the circuit design, presents a mathematical calculation by the differential equations algebraization method, a performed simulation modeling in Matlab/Simulink, and also an assembled experimental stand. Particular attention is paid to the definition of the multizonality concept of the proposed converter and the analysis of the control method. The developed algorithm of the double-loop automatic control system will minimize the influence of induction motors on the mains voltage and thus improve electromagnetic compatibility.