Elimination of low-order harmonics in high power medium voltage inverter applications using a modified SHE-PWM technique

Abstract

There are several conventional selected harmonic elimination techniques that form a class of pulse width modulation techniques (SHEPWM) that are very effective compared to other PWM schemes in the elimination of the low-order harmonics. However they suffer from a complicated computational process especially if the number of low order harmonics to be eliminated is high. This paper presents a new technique that employs one inverter (the reference inverter) using a conventional SHE-PWM scheme to eliminate a number of specific low order harmonics, while a second inverter is phase shifted with a pre-calculated angle to eliminate the first significant surplus harmonic. This set of two inverters is to be connected to a second similar set of two inverters, with a second pre-calculated phase shift, to eliminate the second significant surplus harmonic and so on. Simulation results obtained by MATLAB and PSpice are compared for three-phase high-power medium voltage inverters.