Analysis of Synchronization Stability for Multi VSCs Parallel-Connected to Weak Grids by Improved Net Damping Criterion

Dong Wang, Xiaojie Zhang, Lei Yang, Yunhui Huang, Wei Huang, Chen Wu and Shengnan Li
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Dong Wang: Department of Electrical Engineering, School of Automation, Wuhan University of Technology, Wuhan 430070, China
Xiaojie Zhang: State Key Laboratory of Advanced Electromagnetic Engineering and Technology, and School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
Lei Yang: Electric Power Research Institute of Yunan, Kunming 650217, China
Yunhui Huang: Department of Electrical Engineering, School of Automation, Wuhan University of Technology, Wuhan 430070, China
Wei Huang: Electric Power Dispatching and Control Center of Yunan, Kunming 650200, China
Chen Wu: Electric Power Dispatching and Control Center of Yunan, Kunming 650200, China
Shengnan Li: Electric Power Research Institute of Yunan, Kunming 650217, China

Energies, 2020, vol. 13, issue 13, 1-16

Abstract: Recent studies show that the loss of stability for a voltage-source converter (VSC) in weak-grid connection is largely related to its synchronization unit, i.e., the phase-locked loop (PLL). This paper studies the synchronization stability of a system comprised by two VSCs in parallel connection to a weak grid. A reduced transfer function based small-signal model, which can allow for the interactions between PLL and converter outer power controls, is first proposed. Then, an improved net damping criterion is used to analyze the damping and stability characters of such system under various operating conditions and different controller configurations. Compared to the conventional net damping criterion, the used criterion has wider applicability in terms of stability judgment. Case studies show that the studied system tends to be unstable at weak-grid or heavy-loading conditions. The instability can be in the form of oscillations or monotonic divergence, in which, the latter is more likely to occur for the converters without grid voltage regulation capabilities. Besides, the net damping-based sensitivity studies can provide guidance on control tuning or design for stability enhancement. Detailed model-based time domain simulations are conducted to verify the analysis results.

Keywords: weak grid; VSC; PLL; net damping criterion; 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: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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