Natural Balance of Multicell Converters: The Two-Cell Case

• Published in: IEEE transactions on power electronics Vol. 21; no. 6; pp. 1649 - 1657
• Main Authors: Wilkinson, R.H., Meynard, T.A., du Toit Mouton, H.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.11.2006; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Africa; Applied sciences; Capacitors; Catalytic converters; Circuit properties; Circuit topology; Converters; Convertors; Electric, optical and optoelectronic circuits; Electrical engineering. Electrical power engineering; Electrical machines; Electronic circuits; Electronics; Exact sciences and technology; Impedance; Insulated gate bipolar transistor (IGBT); Insulated gate bipolar transistors; Inverters; Mass balance models; Mathematical analysis; Mathematical models; Other multijunction devices. Power transistors. Thyristors; p -cells; Power electronics, power supplies; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Series & special reports; Signal convertors; Simulation; Studies; Switches; Switching; Switching converters; Switching frequency; Topology; Voltage; Waveforms; Harmonic; Power converter; Insulated gate bipolar transistor; Switching function; Voltage regulation; Booster; Power system stability; Power electronics; Switching convertors; Switching; Power transistor; Operating conditions; Load impedance; p-cells; Switching conditions; Equivalent circuit; Insulated gate bipolar transistor (IGBT); System simulation; Multilevel system; Gain
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2006.882958

The multicell converter topology is said to possess a natural voltage balancing property. This paper is the first of a two-part series in which multicell converters are modelled for the general case of p-cells. This paper focuses on the development of the natural balancing theory for the two-cell case. An understanding of the two-cell case is fundamental to understanding the general balancing theory. 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. The main conclusion of the analysis is that the natural balancing of these converters are influenced by three factors namely, the harmonic content of the reference waveform, the switching frequency and the load impedance. Mathematical tools are presented that can help designers to predict if balancing problems would occur for a particular set of operating conditions. As a result of the detailed understanding of the balancing mechanism that is gained through this theory it is shown that by adding a balance booster, the load impedance can be manipulated to improve the natural balancing of the converter. Simulation results are included to verify the presented balance theory and properties