Generalised pulse width modulation approach for DC capacitor voltage balancing in diode-clamped multilevel converters

This study develops a generalised pulse width modulation (PWM) approach to eliminate both the low-frequency oscillations and imbalances in the dc-link capacitor voltages, which are the main drawbacks of diode clamped converters. The algorithm has been developed within the carrier-based PWM framework to facilitate its implementation in diode clamped converters with four or more levels. In addition, a generalised control strategy for dc voltage control is proposed and its stability is demonstrated. The good performance of the proposed modulation technique is demonstrated from simulation and experimental results for a four-level diode-clamped inverter.