Harmonic Analysis for Low-Capacitance Cascaded H-Bridge STATCOM with Phase-shifted PWM

Abstract

Phase-shifted pulse width modulation (PSPWM) has been an industry standard applied to cascaded H-bridge (CHB) multilevel converters. The application of film capacitors to dc-link results in a reliable CHB system, but considerable capacitor voltage variation is also introduced due to the low power density of film capacitors. This paper develops an analytical solution to the harmonic spectrum of the pulsewidth modulated output voltage of the CHB-STATCOM connected to the dc bus with considerable voltage ripple. Simulation results are presented to validate the analytical solution.