Control Strategy for Three-Phase Grid-Connected PV Inverters Enabling Current Limitation Under Unbalanced Faults

Ehsan Afshari, Gholam Reza Moradi, Ramin Rahimi, Babak Farhangi, Yongheng Yang, Frede Blaabjerg, Shahrokh Farhangi

Research output: Contribution to journalJournal articleResearchpeer-review

86 Citations (Scopus)
370 Downloads (Pure)

Abstract

Power quality and voltage control are among the most important aspects of the grid-connected power converter operation under faults. Non-sinusoidal current is injected during unbalanced voltage sag and active or/and reactive power includes double frequency content. This paper introduces a novel control strategy to mitigate the double grid frequency oscillations in the active power and dc-link voltage of the two-stage three-phase grid-connected Photovoltaic (PV) inverters during unbalanced faults. With the proposed control method, PV inverter injects sinusoidal currents under unbalanced grid faults. In addition, an efficient and easy-to-implement current limitation method is introduced, which can effectively limit the injected currents to the rated value during faults. In this case, the fault-ride-through operation is ensured and it will not trigger the overcurrent protection. A non-MPPT operation mode is proposed for the dc-dc converter. The mode is enabled under severe faults when the converter cannot handle the maximum PV power. Finally, experimental validation is provided by implementing the method in an experimental setup including a 2-kW PV inverter.
Original languageEnglish
JournalI E E E Transactions on Industrial Electronics
Volume64
Issue number11
Pages (from-to)8908-8918
Number of pages11
ISSN0278-0046
DOIs
Publication statusPublished - Nov 2017

Keywords

  • Active power oscillations
  • Current limitation
  • DC-link voltage oscillations
  • Low-voltage ride-through (LVRT)
  • Photovoltaic (PV) systems

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