PWM strategy with harmonics injection and modulated frequency triangular carrier. A review.

Abstract

A new, programmed pulse-width modulation (PWM) technique to control power inverters, which uses a harmonic-injection modulator and a frequency-modulated triangular carrier, synchronized with the modulating signal is presented in this paper. The instantaneous carrier frequency is adjusted according to a periodic function synchronized with the fundamental term of the modulating signal, in order to maintain the average value of the instantaneous frequency as an odd positive integer multiple of 3, for each period of the modulating signal—which is known as the average modulation order. The advantages of using the proposed technique over the conventional PWM techniques are the reduction in the total harmonic distortion and shift the frequency up of the temporal harmonics for any average modulation order. The experimental results show the viability of optimizing the time harmonics generated to minimize the vibrations in an induction motor or avoid the resonant frequencies. The mathematical formulation for the output modulated voltage is defined and the results are also checked experimentally and compared to a sinusoidal PWM technique.