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A new current limiting and overload protection scheme for distributed inverters in microgrids under grid faults

- Li, Zilin, Hu, Jiefeng, Chan, Ka Wing

  • Authors: Li, Zilin , Hu, Jiefeng , Chan, Ka Wing
  • Date: 2021
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Industry Applications Vol. 57, no. 6 (2021), p. 6362-6374
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  • Description: Unlike a synchronous generator that could withstand a large overcurrent, an inverter-based distributed generation (DG) has low thermal inertia, and the inverter is likely damaged by overcurrents during grid faults. In this article, a new strategy, namely positive-And negative-sequence limiting with stability enhanced P-f droop control (PNSL-SEPFC), is proposed to limit the output currents and active power of droop-controlled inverters in islanded microgrids. This strategy is easy to implement in the inverter controller and does not require any fault detection. Inverter stability is analyzed mathematically, which gives guidelines to design the parameters of the PNSL-SEPFC strategy. PSCAD/EMTDC simulation based on a four-DG microgrid shows that the proposed PNSL-SEPFC can limit inverter output currents and powers with better performance under both symmetrical and asymmetrical faults. Furthermore, hardware experiments demonstrate that the proposed PNSL-SEPFC can ensure the inverters riding through grid faults safely and stably. (A video of experimental waveforms is attached.). © 1972-2012 IEEE.

A new current limiting and overload protection strategy for droop-controlled voltage-source converters in islanded AC microgrids under grid faulted conditions

- Li, Zi-Lin, Hu, Jiefeng, Chan, Ka Wing

  • Authors: Li, Zi-Lin , Hu, Jiefeng , Chan, Ka Wing
  • Date: 2020
  • Type: Text , Conference paper
  • Relation: 12th Annual IEEE Energy Conversion Congress and Exposition, ECCE 2020,Detroit, MI, USA, USA, 11-15 Oct. 2020 p. 3888-3893
  • Full Text: false
  • Reviewed:
  • Description: Grid-forming voltage source converter (VSC) plays a vital role in the future renewable energy-based utility grid. Limited by the thermal capability of semiconductor switches, grid-forming VSC-based distributed generation units (DGs) cannot stand excess overcurrent like synchronous generators (SG) during large transient disturbances. In order to protect the VSC from overcurrent and ride through the transient disturbances, a new current limiting and overload protection strategy is proposed in this paper. By properly selecting the maximum current thresholds in the synchronous rotating frame, overcurrent and overload protection are achieved simultaneously. The synchronization among DGs is enhanced by feeding back the output voltage in the q-axis to the active power droop control. A comparison study between the proposed strategy and two existing methods are conducted using a networked microgrid in PSCAD/EMTDC, examining the effectiveness of the proposed strategy. © 2020 IEEE.
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