NATURAL VOLTAGE BALANCING IN HYBRID FCC MULTILEVEL CONVERTER

Abstract

Multilevel converters are frequently used in high and medium power applications. The challenge associated with successful operation of multilevel converters, is the voltage balancing. There are two major techniques dedicated to deal with the voltage balancing, namely: natural and active voltage balancing techniques. Natural balancing is more preferable, since it does not require sensing and in-time controlling equipment. Accepted methods of natural balancing investigation is based on the manipulations of the frequency components. This methods imply heavy computations and not general solutions. In contrast, time-domain analysis, proposed in this paper, produces simple closed-form solutions and requires simple mathematical calculations. The project is focused on performing time-domain analysis in order to investigate natural balancing characteristics of Combined H-Bridge Flying Capacitor Converter (HFCC) converter, for which natural balancing investigations is not reported in literature yet. Modulation strategy was obtained using Matlab software simulation and were implemented with PWM control and Matlab Simulink interface. Obtained results have demonstrated the fast balancing rates with natural balancing, for the majority part of modulation range. In addition, produced analytical equations, that describe voltage balancing dynamics do not require heavy computational effort and could be calculated online.