Optimized resolution-level for input-output control of 3ϕ VS WM AC-DC converters

The switching pulses generated by the wavelet modulation technique represent sets of scaled and translated synthesis scale-based linearly-combined wavelet basis functions. The duration and location of each switching pulse are determined by the scale. In this paper, a novel controller is developed and tested for three phase, voltage source, 6-pulse wavelet modulated ac-dc converters. The proposed controller is structured to determine the maximum value of the scale j based on two phase shift angles. The first phase shift angle θ_I is defined to adjust the generated switching pulses in response to changes in the converter input three phase voltages. The second phase shift angle θ_O is defined to adjust the generated switching pulses in order to ensure the output dc voltage follows its command value. The optimized resolution-level controller is implemented for simulation and experimental testing for input three phase voltages with unbalances, as well as step changes in the command output dc voltage. Test results demonstrate fast responses, accurate adjustments and good dynamics to ensure the output dc voltage follows its command value regardless of the state of the 3φ input voltages.