A Three-Phase Three-Level Isolated DC-AC Converter with Line Frequency Unfolding

Pal, A and Basu, K (2020) A Three-Phase Three-Level Isolated DC-AC Converter with Line Frequency Unfolding. In: IEEE Transactions on Power Electronics, 35 (11). pp. 11758-11769.

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Abstract

A three-level three-phase single-stage high-frequency link dc-ac converter is reported in this article for grid integration of photovoltaic sources. The proposed topology employs two three-level neutral point clamp (NPC) half-bridge legs on the dc side. The advantages of using three-level legs over conventional two level are: 1) the three-level legs can be implemented with the devices with lower blocking voltage which are economical; and 2) the low voltage blocking devices have lower on-state drop and lower turn on-off energy losses compared to high voltage blocking devices used in a two-level leg. These help to improve the converter efficiency. The sinusoidal pulsewidth modulation is implemented with the three-level NPC legs. The modulation strategy ensures reduced neutral current drawn by the NPC legs. The inner switches of the NPC legs are zero voltage switched. The turn-on transitions of the outer switches are with zero current. The proposed solution employs two high-frequency transformers to provide galvanic isolation which results in compact, low cost isolated converter solution. The intermediate dc link is pulsating and does not require any filtering. A low-frequency unfolder is employed to generate line frequency ac from pulsating dc. The switching loss of the unfolder is negligible. The proposed topology can support stand-alone load up to ± 0.866 PF. The converter operation is verified on a 2-kW hardware prototype. © 1986-2012 IEEE.

Item Type:	Journal Article
Publication:	IEEE Transactions on Power Electronics
Publisher:	Institute of Electrical and Electronics Engineers Inc.
Additional Information:	Copy right for this article belongs to Institute of Electrical and Electronics Engineers Inc.
Keywords:	Energy dissipation; High frequency transformers; HVDC power transmission; Modulation; Topology; Zero voltage switching, Converter efficiency; High frequency link; Isolated converters; Modulation strategy; Neutral point clamps; Photovoltaic sources; Sinusoidal pulse width modulation; Zero-voltage-switched, Electric inverters
Department/Centre:	Division of Electrical Sciences > Electrical Engineering
Date Deposited:	05 Nov 2020 10:21
Last Modified:	05 Nov 2020 10:21
URI:	http://eprints.iisc.ac.in/id/eprint/66350

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