Analysis and performance evaluation of space vector pulse width modulation based algorithms for multilevel neutral point clamped inverter fed induction motor drive

Abstract

Multilevel inverter technology has recently emerged as a very important alternative in the area of high-power medium-voltage energy control. The output voltage of power inverter is to be a pure sinusoidal waveform with minimum distortion. But for the practical inverters, the output voltage is a series of rectangular waveforms. The major issues for the control of the power inverters are to get suitable modulation methods to control the output rectangular waveforms to synthesize the desired waveforms. Therefore a modulation control method is required to get a desired fundamental frequency voltage and to eliminate higher order harmonics as much as possible.Higher frequencies are employed in traditional pulse width modulation methods because of the undesirable harmonics occur at higher frequencies, which can be filtered easily and several kHz is well above the acoustic noise level. But the traditional pulse width modulation methods cause electromagnetic interference. The rapid change in voltage (dv/dt) is the cause of electromagnetic interference. A high dv/dt produces common-mode voltages across the windings of motor and leads to damage it. In multilevel inverters, as the switching involves several small voltages, the rapid change in voltage is smaller. Further, switching at the fundamental frequency will also result in decreasing the number of times these voltage changes occur per fundamental cycle. In multilevel inverter there will be more than one way to generate the desired voltages due to switching redundancies.