Voltage compensation by a modified mixed cascade flying capacitor multicell inverter
ABSTRACT Multicell multilevel converters are very interesting alternatives for high power applications. A modified mixed cascade flying capacitor multicell inverter is proposed in this paper which leads to reduction in the number of switches. The proposed configuration is used for compensation of voltage sag/swell and voltage unbalance. Simulation results by MATLAB simulink confirm the effectiveness of this configuration.
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ABSTRACT: The paper explores the spontaneous coupled clamping-capacitor-current control loops and the resultant self-balancing property of the clamping-capacitor-voltages in the multilevel capacitor-clamping-inverter. The case of the three-level capacitor-clamping-inverter under sub-harmonic PWM modulation is dealt with first. The case of the multilevel capacitor-clamping-inverter (M>3) under sub-harmonic PWM modulation is then analyzed. Test results on a half-bridge three-level capacitor-clamping-inverter prototype under sub-harmonic PWM modulation are demonstratedIEEE Transactions on Power Electronics 04/2001; · 4.08 Impact Factor
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ABSTRACT: This paper focuses on the development of the natural balancing theory for the p-cell case. It describes the relationship between the models for different numbers of cells in a generic model for a p-cell multicell converter. The model discussed is based on the same principles that were used to develop the two-cell model in , except that the mathematics is much more involved. The same conclusions that were found to be true for the two-cell case was also found to be true for the general case of p cells. These conclusions include that the natural balancing mechanism of multicell converters depends on the overlap of the groups of harmonics of the switching function as well as on the load impedance. It will also be shown that the self-balancing mechanism ensures safe operation under most operating conditions where a high enough switching frequency is chosen and the load is not purely reactive. Two new aspects of the balancing theory were identified in the p-cell case: 1) for fixed duty-cycle modulation there exists certain values of the duty-cycle that causes the natural balancing mechanism to fail and 2) for p-cell converters the balance booster concept can be extended to a number of balance boosters tuned to multiples of the switching frequency. A "DesignTool" based on the balancing theory was developed to aid practicing engineers in designing multicell convertersIEEE Transactions on Power Electronics 12/2006; · 4.08 Impact Factor
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ABSTRACT: 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 propertiesIEEE Transactions on Power Electronics 12/2006; · 4.08 Impact Factor