Analysis of wide-band oscillation of hybrid MMC interfacing weak AC power system

Xiaojun Lu, Wang Xiang, Weixing Lin, Jinyu Wen

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Abstract

The wide-band oscillation of the hybrid MMC induced by excessive power infeed under weak AC power system integration is analyzed in this paper. A closed-loop state-space-based time-domain small-signal model is firstly established to investigate the instability problem. Different from the findings in two-level VSCs or half-bridge MMCs, the root locus analysis and participation factor analysis in this paper reveals that the oscillation frequency and involved control loops are highly related to the operation status. When hybrid MMC operates as a rectifier, a low-frequency oscillation is observed with the d-channel control loop mainly participated. In contrast, a high-frequency oscillation occurs with a q-channel control loop mainly involved when the hybrid MMC operates as an inverter. This wide-band oscillation phenomenon is explored with the aid of two simplified loop-gain-based s-domain models, which are derived referring to the selective modal analysis approach. To suppress the oscillation, sensitivity analysis regarding the impact of parameters on the phase margin is conducted to recognize effective parameter adjustment methods. The analysis results are validated by detailed electromagnetic simulations.
Original languageEnglish
Number of pages13
JournalIEEE Journal of Emerging and Selected Topics in Power Electronics
Early online date21 Sep 2020
DOIs
Publication statusE-pub ahead of print - 21 Sep 2020

Keywords

  • analytical models
  • power system stability
  • voltage control
  • stability analysis
  • power harmonic filters

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