A Grid Synchronization PLL Method Based on Mixed Second- and Third-Order Generalized Integrator for DC-Offset Elimination and Frequency Adaptability

Chunjiang Zhang, Xiaojun Zhao*, Xiaohuan Wang, Xiuhui Chai, Zhe Zhang, Xiaoqiang Guo

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

The second order generalized integrator (SOGI) has been widely used to implement grid synchronization for grid-connected inverters, and from grid voltages it is able to extract the fundamental components with an output of two orthogonal sinusoidal signals. However, if there is a dc offset existing in the grid voltages, the general SOGI’s performance suffers from its generated dc effect in the lagging sine signal at the output. Therefore, in this paper, a mixed second- and third-order generalized integrator (MSTOGI) is proposed to eliminate this effect caused by the dc offset of grid voltages. A detailed theoretical analysis on the proposed MSTOGI is presented to reveal the mechanism of eliminating the dc offset. After that, the MSTOGI is applied to a phase-locked loop (PLL) and thereby establish an MSTOGI-PLL which is more adaptable to various grid conditions and power quality. Moreover, a frequency-adaptive control scheme is added to the proposed MSTOGI-PLL to eliminate the phase difference between the PLL output and the grid in grid-connected applications where the grid frequency may vary. Finally, the experimental results from a laboratory prototype are given to demonstrate and verify the effectiveness of the proposed MSTOGI-PLL in terms of steady-state performance, dynamic response and frequency adaptability.
Original languageEnglish
JournalIEEE Journal of Emerging and Selected Topics in Power Electronics
Volume6
Issue number3
Number of pages10
ISSN2168-6777
DOIs
Publication statusPublished - 2018

Keywords

  • Third-order generalized integrator (TOGI)
  • Phase-locked loop (PLL)
  • Synchronization
  • Non-ideal grid

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