Selecting stepped reference waveforms for PWM inverter drives to minimize the current distortion

Abstract

This paper assesses the ability of stepped reference signals to produce 3-phase pwm waveforms with a low current distortion. Four modulation techniques, that use three steps per 90' of the fundamental cycle, are analyzed. The functional relationships between each of the steps, determined by a current distortion minimization procedure, are shown to change with the carrier frequency and the magnitude of the fundamental. The lowest current distortion characteristics are obtained by selecting modulating techniques to cover specified ranges of the fundamental magnitude.Stepped waveforms are shown to be competitive with sinewave regular sampling techniques, and near-optimal performance can be obtained at low carrier frequencies.Operation at very high fundamental magnitudes is possible with minimal current distortion and well defined switching periods.

A simple approach to current THD prediction for small-scale grid-connected inverters

“…Fourier analysis is a usual method to identify the harmonic contents for a pulse width modulation (PWM) control, but it is not an effective and efficient way when a high or a non-integer carrier-to-fundamental ratio is applied [8]. Bennett method is another one widely used for harmonic analysis so far through using a 3-D modulation model based on a double Fourier series which is firstly applied by Bowes [9] in 1975 and developed in the past decades [10][11][12]. However, harmonic analysis performed by Bennett methods is limited by both a detail description of the modulation waveform and massive amounts of numerical calculations.…”