Development and Experimental Testing of a 3o Resolution-Level Controlled WM Inverter-Fed Induction Motor

This paper presents a novel speed control approach for inverter-fed three-phase (3Phi) induction motors. The proposed approach is called the resolution-level controller (RLC) that is realized for the 3Phi voltage-source (VS) wavelet-modulated (WM) inverters. The wavelet modulation technique generates switching pulses using a non-dyadic type multiresolution analysis (MRA) that is constructed by three scale-based linearly-combined scaling functions shifted by 2pi/3 from each other. Moreover, The change in the scale of the three synthesis scaling functions is based on the change of the sign of the first derivative of the reference-modulating signals. The three scaling functions have dual synthesis scaling functions that are responsible for reconstructing the three continuous-time reference-modulating signals from their nonuniform recurrent samples. The reconstruction processes are carried out by the three synthesis scaling functions to achieve 180-degrees conduction mode of the 3Phi inverter. The proposed RLC approach is based on adjusting the zero-crossing locations of the first derivative of the reference-modulating signals to change scales of successive dilated and shifted versions of the three synthesis scaling functions. This change in scales can be incorporated to adjust the speed of the induction motor to meet load changes. The complete drive incorporating the RLC is successfully implemented in real-time using a digital signal processor board dSPACE ds1102 DSP board to generate switching pulses to activate the inverter six IGBT switches. The IGBT inverter supplies a 1 hp, 1750 RPM, 208 V, 60 Hz, Y-connected 3Phi squirrel-cage induction motor that is tested for several speed and load variations. The test results demonstrate robust performance, simple implementation, significant dynamic responses and high ability to maintain high quality outputs.