DC-Voltage-Ratio Control Strategy for Multilevel Cascaded Converters Fed With a Single DC Source

• Published in: IEEE transactions on industrial electronics (1982) Vol. 56; no. 7; pp. 2513 - 2521
• Main Authors: Vazquez, S., Leon, J.I., Franquelo, L.G., Padilla, J.J., Carrasco, J.M.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.07.2009; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Converters; Councils; Direct current; Distortion; Electric potential; Fault tolerance; Government; Low voltage; Modulation; Motor drives; Multilevel; Multilevel systems; Renewable energy resources; Strategy; Time domain analysis; Topology; Voltage; Voltage control
• ISSN: 0278-0046; 1557-9948
• DOI: 10.1109/TIE.2009.2017549

Recently, a multilevel cascaded converter fed with a single DC source has been presented. An analysis of the steady-state working limits of this type of converter is presented in this paper. Limits of the maximum output voltage and the minimum and maximum loading conditions for stable operation of the converter are addressed. In this paper, a way to achieve any DC voltage ratio (inside the stable operation area of the converter) between the H-bridges of the single-DC-source cascaded H-bridge converter is presented. The proposed DC-voltage-ratio control is based on a time-domain modulation strategy that avoids the use of inappropriate states to achieve the DC-voltage-ratio control. The proposed technique is a feedforward-modulation technique which takes into account the actual DC voltage of each H-bridge of the converter, leading to output waveforms with low distortion. In this way, the dc voltage of the floating H-bridge can be controlled while the output voltage has low distortion independently of the desired DC voltage ratio. Experimental results from a two-cell cascaded converter are presented in order to validate the proposed DC-voltage-ratio control strategy and the introduced concepts.