Trapezoidal PWM scheme for multilevel inverter

Abstract

Multilevel voltage source inverter (VSI) structure has been recognized to be very popular especially in high power applications. The general concept of multilevel inverter is to synthesize a sinusoidal voltage from several levels of voltages. By having two or more level of voltages to build sinusoidal voltage, the voltage stress on the switching devices is reduced and the output harmonics distortion is minimized. It is reported that the development of multilevel VSI topology has began in early 1980’s when Nabae at el proposed a three-level Neutral Point Clamped (NPC). Since then, several multilevel topologies have evolved. Presently, there is a number of topologies that can be found in literature and the common topologies are Diode Clamp Multilevel Inverter (DCMI) also known as Neutral Point Clamp (NPC), Flying Capacitor Multilevel Inverter (FCMI) and Cascaded Multilevel Inverter (CMI)[