Current vector controls of AC drives

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Dr. Veszprémi Károly
Department of Electric Power Engineering

This thesis' main purpose is to present the mathematical models of alternating current (AC) machines and the power line, along with their direct and indirect current vector controls and simulation results.

In the first part, the space vector-based permanent magnet synchronous machines', the squirrel-cage induction machines’ and also the power line's equations will be presented. Further the two-level Voltage Source Inverter (VSI) and various Pulse-Width Modulation (PWM) techniques will be detailed, such as the three-phase and space vector PWM controllers.

In the second chapter, direct torque and flux control (DTC) will be presented with a squirrel-cage induction machine. First the algorithm basics will be discussed, followed by additional algorithms, which are required for a demand controlled electric drive. In the last part of this chapter the discovered flux and torque errors and possible solutions for them will be described. It will be shown, that these algorithms can be adapted to a permanent magnet synchronous machine-based direct torque controlled drive. The line-side's direct power control (DPC) will be detailed in this chapter, because it shares many similarities with DTC.

In the third chapter of the thesis, various current vector controls' simulation results will be presented. The mathematical models were implemented in MATLAB and Simulink. In order to understand the systems' behaviors and also to reduce the simulations run time, I took the advantage of the MATLAB's Graphical User Interface developing abilities. These programs were developed not just to visualize the vector trajectories and time signals, but to get back the temporality, which was lost with the space vector-based mathematical models. These GUIs helped me to understand the unexpected errors more easily and to provide solutions to them.


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