Technological sciences, electrical and electronic engineering (01T).
The research results of the inverter, which is used in the frequency converters for control of AC induction motors and is controlled by the space vector modulation principle, have been presented in the dissertation. The main aim of the work – to perform the research of the inverter controlled by the space vector modulation principle and to develop the inverter voltage amplitude control method, which allow us to reduce the power losses in the inverter and motor. The space vector modulation method with the averaged pulse lengths has been presented. The voltage spectrum and power losses in the inverter and motor were investigated for the case when this method is used. The obtained results were compared to the results gained using classical space vector modulation method and the superiority of the space vector modulation method with the averaged pulse lengths has been shown. The problem of inverter voltage first harmonic amplitude control has been reviewed and methods of amplitude control are analyzed. The dependences of the inverter voltage first harmonic amplitude on frequency (on motor speed), at which the minimal power losses in the AC induction motor are guarantied, were found. The inverter voltage first harmonic amplitude control method, which allows maintaining the minimal current of motor in the situation when motor load changes randomly, has been developed and investigated. The minimum of function of motor current dependence on voltage first harmonic amplitude has to be found by digital signal processor in real time for realization of suggested method. The impact of the IGBT transistor control circuit structure and parameters on the temperature of inverter has been investigated. It is shown that the switching losses affect the heating of inverter transistors marginally. The concept of dead time realisation for the inverter switches in the control circuit of the switch instead of its realization by the digital signal processor, which allows as avoiding the damage of the inverter if the processor operation is disturbed by the EMD, has been suggested. The new IGBT transistor control circuit, witch introduces the dead time, is developed and analyzed. The overvoltages generated in the inverter during the motor deceleration have been analyzed. The investigation was performed for various values of initial speed and load torque of motor and capacitance of the inverter supply filter capacitors. The obtained results of the dissertation are applied for the development of the specialized frequency converters for the serial production. The research works were related with the two projects financed by the industry and two projects supported by the Lithuanian State Science and Study Foundation and Agency for Science, Innovation and Technology. The results of the dissertation were presented in the eight scientific conferences and published in the nine scientific papers.
Read electronic version of the book: