Natural balance of multicell converters

Abstract

The multicell converter topology is said to possess a natural voltage balancing property. This paper models multicell converters for the general case of p-cells. It describes the relationship between the models for different numbers of cells in a generic model for a p-cell multicell converter. The switching functions used in switching these converters are mathematically analyzed. Equivalent circuits are derived and presented. The switching and balancing properties of these converters are mathematically analyzed. Multicell converters were modeled previously for both sinusoidal and fixed duty-cycle references. The model discussed is valid for any modulation method. The conditions for balanced cell capacitor voltages are presented from the aforementioned mathematical synthesis. The balancing property of these converters is also proved mathematically from the presented properties and conditions for natural balancing are discussed. The balancing properties and conditions are formulated and presented as a "natural balance theory for multicell converters". Simulation and experimental results are included to verify the presented balance theory and properties. Conclusions presented include conditions for the theory to be valid as well as possible extensions to the theory and practical implications on converter design