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Energies 2016, 9(9), 732;

A Riding-through Technique for Seamless Transition between Islanded and Grid-Connected Modes of Droop-Controlled Inverters

Department of Electrical Engineering, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
Department of Energy Technology, Aalborg University, Aalborg 9100, Denmark
Author to whom correspondence should be addressed.
Academic Editor: Chunhua Liu
Received: 31 May 2016 / Revised: 30 August 2016 / Accepted: 31 August 2016 / Published: 9 September 2016
(This article belongs to the Special Issue Microgrids 2016)
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This paper presents a seamless transition method for a droop-controlled inverter. The droop control is suitable to make the inverter work as a voltage source in both islanded and grid-connected modes, however, the transfer between theses modes can result in a big inrush current that may damage the system. The proposed method allows the droop-controlled inverter to improve the transient response when transferring between modes, by detecting the inrush current, activating a current control loop during transients, and then transferring back to droop-controlled mode smoothly by using a virtual inductance loop. In addition, a local phase-locked-loop (PLL) is proposed to align the inverter voltage with the grid in order to reduce the transient current during the transition. Therefore, the droop-controlled inverter is able to operate in both grid-connected and islanded modes, providing as well a smooth transition between them, requiring neither synchronization signals nor grid-side information. The control algorithm and design procedure are presented. Experimental results from a laboratory prototype validate the effectiveness of the proposed method. View Full-Text
Keywords: droop control; virtual inductance; microgrid; grid-connected; islanded droop control; virtual inductance; microgrid; grid-connected; islanded

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Hu, S.-H.; Lee, T.-L.; Kuo, C.-Y.; Guerrero, J.M. A Riding-through Technique for Seamless Transition between Islanded and Grid-Connected Modes of Droop-Controlled Inverters. Energies 2016, 9, 732.

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