Chapter 1 - Pulse width modulation and control methods for multilevel inverters

Abstract

The controllers improved for commutating multilevel inverters (MLIs) are based on fundamental modulators fed by required parameters obtained from feedback or feedforward devices. This chapter presents a general introduction to modulation theory and its featured use in the modulator block of MLI controllers. The conventional pulse width modulation schemes and implementation methods are introduced in detail, while phase-locked loop (PLL) controllers tracking the reference values are also represented with application examples from the literature. The synchronous reference frame (SRF), αβ, double synchronous reference frame (DSRF), sinusoidal signal integrator (SSI), dual second-order generalized integrator (DSOGI), and enhanced PLL methods have been introduced and compared in this chapter, while the controllers of grid-connected inverters are depicted with synchronous reference frame, stationary reference frame, and natural reference frame control methods.