Voltage Balancing in Five-Level Diode-Clamped Power Converters

This paper addresses the voltage imbalance problem of the dc-link capacitors in multilevel power converters. Considering the five-level diode-clamped converter, a mathematical analysis of the capacitor voltage difference dynamics is carried out. It leads to a new problem statement that relates the voltage balancing objective to a problem of ensuring the practical stability of a nonlinear system in the presence of disturbances. Then, exploiting the properties and knowledge of the disturbance patterns, a novel and simple controller is presented. Simulation results are included to validate the performance of the proposed controller.