Implementing $V/f$ Control for Induction Motors Fed by Wavelet Modulated Power Electronic Converters
S. A. Saleh
Abstract
Volt-per-hertz ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V/f$</tex> ) scalar control is one the simplest control structures developed for operating induction motor drives. This paper presents the development and performance testing of a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V/f$</tex> scalar control for induction motor drives that are fed by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3\phi$</tex> wavelet modulated dc-ac power electronic converters. The wavelet modulation technique is typically characterized by the maximum resolution level ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$J$</tex> ) and scale-time interval factor ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\gamma$</tex> ). The magnitude of the output voltage of a three phase wavelet modulated inverter is directly dependent on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$J$</tex> , while the number of switching pulses, over a half cycle of the output voltage, is related to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\gamma$</tex> . These two factors of the wavelet modulation technique can be adjusted to implement a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V/f$</tex> scalar control of induction motor drives. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V/f$</tex> scalar control of a wavelet modulated dc-ac PEC is implemented for performance testing using induction motor drives under different operating conditions. Performance results demonstrate stable, dynamic, and accurate responses, with minor sensitivities to the load torque and/or initial and final speeds. Furthermore, test results demonstrate the ability to enhance the efficiency using the tested scalar control.