Removal of DC offset current from transformerless PV inverters connected to utility

Sharma, Ronald (2005) Removal of DC offset current from transformerless PV inverters connected to utility. In: 40th International Universities Power Engineering Conference (UPEC 2005), 7-9 Sept 2005, Cork, Ireland.

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Some electricity supply authorities in Australia allow PV inverters of up to 10 kW output to be directly connected to
their grid network. The benefits of avoiding the use of power transformers in such PV applications are higher
conversion efficiency of the PV system and lower costs. These benefits however, can only be realised if the level of DC offset current injected from such transformerless inverter systems is maintained within the stringent limits governed by Australian Standard AS4777.2. Currently, there is a lack of evidence that the level DC offset current can be economically and efficiently maintained within these legal limits. In this paper, it is shown that irrespective of its source, the DC offset current can be maintained within these limits without sacrificing the overall conversion efficiency of the inverter system. Simulation and experimental results are presented to confirm that this simple, cost effective technique can be used to measure and separate small magnitudes of DC offset currents from large values of AC currents without compromising the dynamic response of the current feedback loop. This new technique can also be used to improve the quality of the power supplied by PV inverters that use power transformers.

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Item Type: Conference or Workshop Item (Commonwealth Reporting Category E) (Paper)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version deposited in accordance with the copyright policy of the publisher.
Faculty / Department / School: Historic - Faculty of Engineering and Surveying - Department of Electrical, Electronic and Computer Engineering
Date Deposited: 22 Aug 2010 02:48
Last Modified: 02 Jul 2013 23:56
Uncontrolled Keywords: PV inverters; transformerless; unipolar switched; DC offset current
Fields of Research : 09 Engineering > 0913 Mechanical Engineering > 091305 Energy Generation, Conversion and Storage Engineering
09 Engineering > 0906 Electrical and Electronic Engineering > 090607 Power and Energy Systems Engineering (excl. Renewable Power)
Socio-Economic Objective: B Economic Development > 85 Energy > 8506 Energy Storage, Distribution and Supply > 850601 Energy Services and Utilities

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