Direct current offset controller for transformerless single-phase photovoltaic grid-connected inverters
Article
Article Title | Direct current offset controller for transformerless single-phase photovoltaic grid-connected inverters |
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ERA Journal ID | 40937 |
Article Category | Article |
Authors | Bowtell, L. (Author) and Ahfock, A. (Author) |
Journal Title | IET Renewable Power Generation |
Journal Citation | 4 (5), pp. 428-437 |
Number of Pages | 10 |
Year | 2010 |
Place of Publication | Stevenage, Herts. United Kingdom |
ISSN | 1752-1416 |
1752-1424 | |
Digital Object Identifier (DOI) | https://doi.org/10.1049/iet-rpg.2009.0043 |
Web Address (URL) | https://digital-library.theiet.org/content/journals/10.1049/iet-rpg.2009.0043 |
Abstract | Limitation of direct current (DC) injection into the alternating current (AC) network is an important operational requirement for grid-connected photovoltaic (PV) systems. One way to ensure that this requirement is met is to use a power transformer as interface to the AC network. But this adds costs, mass, volume and power losses. In a transformerless system, the inverter forming part of the PV system has to be operated so that the DC content in its output current is below the specified limits. Ideally, there should be no DC at the output of the inverter, but in practice, in the absence of special measures, a small amount of DC current is present. A technique for elimination of the DC-offset is proposed. It is based on the sensing of the DC-offset voltage at the output of the inverter. A sensor output is used to drive a feedback system designed to control the operation of the inverter so that the DC-offset is forced to stay within the acceptable limits. A mathematical model for the DC-offset controller is derived. A design procedure, based on the model, is proposed for the controller. The results of tests performed on a system of 1 kW nominal rating provide validation for the mathematical model. |
Keywords | DC-offset; power quality; DC-injection; AC networks; acceptable limit; alternating current; AS interfaces; DC current; DC offsets; design procedure; direct current; direct-current offsets; feedback systems; grid connected inverters; grid-connected photovoltaic system; operational requirements; output current; power-losses; PV system; sensor output; transformerless |
ANZSRC Field of Research 2020 | 400803. Electrical energy generation (incl. renewables, excl. photovoltaics) |
490105. Dynamical systems in applications | |
401706. Numerical modelling and mechanical characterisation | |
Public Notes | File reproduced in accordance with the copyright policy of the publisher/author. |
Byline Affiliations | Department of Electrical, Electronic and Computer Engineering |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q07vq/direct-current-offset-controller-for-transformerless-single-phase-photovoltaic-grid-connected-inverters
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