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Small-Signal Analysis of Photovoltaic Inverter with Impedance-Compensated Phase-Locked Loop in Weak Grid

Research output: Contribution to journalArticleScientificpeer-review


Original languageEnglish
JournalIEEE Transactions on Energy Conversion
Publication statusE-pub ahead of print - 2019
Publication typeA1 Journal article-refereed


The grid-connection point of photovoltaic inverters may exhibit inductive characteristics (i.e., a weak grid) due to long transmission cables as well as multiple transformers. A large grid impedance can arouse impedance-based stability problems, sustained resonances and impose power-delivery limits. This paper discusses an impedance-compensated synchronous reference- frame-PLL-angle-correction method. The method presented in this paper compensates the PLL angle according to estimated or measured grid impedance in order to achieve improved performance in weak grids. Due to the lack of explicit small-signal impedance models around the aforementioned topic, this paper presents a complete small-signal transfer function model to analyze the impedance-based stability of the PLL-angle compensation method. The results are validated with real-time hardware-in-the-loop simulations and laboratory experiments.

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