Browsing by Author "Ghias, Amer M.Y.M."
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Item Elimination of Low-Frequency Ripples and Regulation of Neutral-Point Voltage in Stacked Multicell Converters(2017-01) Ghias, Amer M.Y.M.; Pou, Josep; Acuna, Pablo; Ceballos, Salvador; Heidari, Alireza; Agelidis, Vassilios G.; Merabet, Adel; POWER ELECTRONICS AND SYSTEM EQUIPMENTThis paper introduces a modulation method for the stacked multicell converters (SMCs). The proposed method is implemented using phase-disposition pulse width modulation and is capable of balancing and regulating the voltages of all the capacitors in the topology, i.e., the flying capacitors and the dc-link capacitors. The proposed method is also able to eliminate the low-frequency voltage ripples that may appear in the neutral point (NP) of SMCs. In SMCs with two stacks, the NP voltage level can be generated by direct connection of the output to the dc-link NP, but also using two extra states available. This redundancy is used to regulate the NP voltage. Furthermore, since the proposed method can eliminate the low-frequency voltage ripples in the capacitors, the capacitances of all the capacitors of the SMCs can be reduced, while maintaining high quality of the output voltages and currents. This enables the use of film capacitors. Simulation and experimental results are presented from a three-phase five-level 2× 2 SMC to verify the effectiveness of the proposed method.Item Low-frequency voltage ripples in the flying capacitors of the nested neutral-point-clamped converter(Institute of Electrical and Electronics Engineers Inc., 2016-05-10) Ghias, Amer M.Y.M.; Pou, Josep; Ceballos, Salvador; Agelidis, Vassilios G.; POWER ELECTRONICS AND SYSTEM EQUIPMENTThe flying capacitors (FCs) of the nested neutral-point-clamped (NNPC) converter show an inherent voltage ripple at fundamental frequency. This ripple can be significantly large under some operating conditions of the converter. In this paper, the amplitudes of the low-frequency voltage ripples in the FCs are determined. An averaged model of the NNPC converter is introduced and used in the analysis. The amplitudes of the capacitor voltage ripples are provided using normalized variables so that this information can be used to size the FCs of the converter in different applications. The results of the analysis are validated experimentally in a laboratory prototype.