Discontinuous space vector PWM strategies for a seven-phase voltage source inverter

Abstract

This paper presents discontinuous space vector PWM (DPWM) strategies for a seven-phase voltage source inverter (VSI). Space vector model of a seven-phase VSI shows that there exist 128 space vectors with different lengths and maps into fourteen sided polygons. A number of possibilities could arise to implement modulation of inverter legs due to large number of available space voltage vectors. Two strategies are adopted here; one utilising only large set of space vectors and another using large and two middle sets of space vectors to implement discontinuous space vector PWM. The former offer best utilisation of available dc link and the later offers nearly sinusoidal output. A significant reduction in switching losses is observed. A generalised formula is presented to determine the exact amount of reduction in the switching losses by using DPWM. Simulation results are provided to validate the concept followed by their experimental implementation. The experimental set-up is illustrated and the experimental results matches the simulation results.