State-space control for LCL filters: Converter versus grid current measurement

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Abstract

This article deals with discrete-time state-space current control of three-phase converters equipped with an LCL filter. Either the converter or grid current is measured, and the unknown states are estimated using a reduced-order observer. The stability and dynamic performance of the control designs based on these two current measurement options are compared by means of analysis and experiments at different sampling frequencies and under varying grid conditions, ranging from strong to very weak. Equal reference-tracking performance under nominal conditions is used as a basis for comparison between these two options. If a strong grid is assumed in the control tuning, the controller based on the grid current measurement (GCM) is found to be more robust against varying grid conditions in a wide range of sampling frequencies than the controller based on the converter current measurement (CCM). The CCM leads to better dynamic performance as compared to the GCM if the resonance frequency of the system falls below the critical resonance frequency.
Original languageEnglish
Article number9167454
Pages (from-to)6608 - 6618
Number of pages11
JournalIEEE Transactions on Industry Applications
Volume56
Issue number6
DOIs
Publication statusPublished - 1 Nov 2020
MoE publication typeA1 Journal article-refereed

Keywords

  • Feedback
  • Grid converter
  • LCL filter
  • State-space current control
  • Weak grid

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