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

Shang-Hung Hu, Tzung-Lin Lee, Chun-Yi Kuo and Josep M. Guerrero
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Shang-Hung Hu: Department of Electrical Engineering, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
Tzung-Lin Lee: Department of Electrical Engineering, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
Chun-Yi Kuo: Department of Electrical Engineering, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
Josep M. Guerrero: Department of Energy Technology, Aalborg University, Aalborg 9100, Denmark

Energies, 2016, vol. 9, issue 9, 1-15

Abstract: 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.

Keywords: droop control; virtual inductance; microgrid; grid-connected; islanded (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2016
References: View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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