Grid-Synchronization Stability Analysis for Multi DFIGs Connected in Parallel to Weak AC Grids

Dong Wang, Yunhui Huang, Min Liao, Guorong Zhu and Xiangtian Deng
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Dong Wang: School of Automation, Department of Electrical Engineering, Wuhan University of Technology, Wuhan 430070, China
Yunhui Huang: School of Automation, Department of Electrical Engineering, Wuhan University of Technology, Wuhan 430070, China
Min Liao: Global Energy Interconnection Research Institute Co. Ltd, State Grid, Beijing 102209, China
Guorong Zhu: School of Automation, Department of Electrical Engineering, Wuhan University of Technology, Wuhan 430070, China
Xiangtian Deng: School of Automation, Department of Electrical Engineering, Wuhan University of Technology, Wuhan 430070, China

Energies, 2019, vol. 12, issue 22, 1-16

Abstract: Recent works have shown that phase-locked loop (PLL) synchronized wind turbines (WTs) suffer stability issues when integrated into weak grids. However, most of the current studies are limited to a single machine case, the interactions among the WTs are usually overlooked. This paper studies the stability of multiple doubly-fed induction generators (DFIGs) that are connected in parallel to a weak AC grid. A state space model of a two-DFIG system is firstly presented. Subsequently, eigenvalue sensitivity analysis shows that instability can occur at low short-circuit ratio (SCR) or heavy loading conditions. Meanwhile, participation factor analysis implies that the unstable mode is primarily induced by the interactions between the PLLs of the two WTs. Further, to make out how the PLLs interact to cause instability, a reduced-order model is proposed for analysis simplicity, and an explanation in terms of transfer function residue is given for illustration. Detailed model-based time domain simulations are conducted to validate the analyses’ results.

Keywords: weak grid; eigenvalue analysis; PLL; DFIG; transfer function residue; synchronization stability (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: 2019
References: View complete reference list from CitEc
Citations: View citations in EconPapers (3)

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