Kozakevych I. Sensorless vector control of induction motors at low angular speed

The purpose of the thesis is to study the dynamic processes in asynchronous electric drive with vector control when working at low angular velocity and the processes in the supply of its inverter with pulse width modulation. The purpose of the work is to develop the theoretical aspects and practical solutions to improve the quality of management of asynchronous electric drives with sensorless vector control and the determination of the angular velocity and flux. Methods: the operator method, the differential calculus method, numerical integration methods, methods of experimental design and search for an extremum, the finite element method. The theoretical results are: the method of compensation of non-linear properties of the voltage of the inverter based on the determination of the current, evaluated by the adaptive model, was first proposed, but in contrast to the existing methods it does not require prior determination of the inverter parameters and a control system; the structure of the observer of the induction motor status, based on using its anisotropic properties, allowing the selection of useful signals anisotropy, that, in contrast to the methods, doesn't involve the use of an idealized model of the induction motor was formalized for the first time; based on the analysis of the existing structures of adaptive systems with a given model the feasibility of a system with variable structure that can significantly improve drive stability in the zone of low angular velocities was shown. Practical results: compensation means designed inverter nonlinearities, which can be used in modern frequency converters in obtaining quality sinusoidal output current when operating in the zone of low output voltages have been developed; algorithms for sensorless determining the angular speed and flux of the induction motor only when measuring the voltage of the DC current link and the inverter output currents which can be used in modern frequency converters intended for process units that require a deep control of the motor speed have been developed; modulation effects division tools which is caused by different anisotropic properties of the engine have been developed so that they could be used for sensorless determination of the angular velocity. The degree of implementation - the results have been implemented by the "Semiol" LTD company and in the learning process of State Higher Education Establishment "Kryvyi Rih National University." The field of application: electrical industry.