Influence of the Phase-Locked Loop on the Design of Microgrids Formed by Diesel Generators and Grid-Forming Converters

In recent years, microgrids (MGs) with renewable energy sources, diesel gen-sets, and droop-controlled converters have been increasingly used to guarantee the continuity of power supply in remote areas. Renewable energy sources have been typically connected to MGs by using an electronic converter th...

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Bibliographic Details
Published in:IEEE transactions on power electronics 2022-05, Vol.37 (5), p.5122-5137
Main Authors: Moran-Rio, Diana Patricia, Roldan-Perez, Javier, Prodanovic, Milan, Garcia-Cerrada, Aurelio
Format: Article
Language:English
Subjects:
Alternative energy sources
Control stability
Controllers
Converters
Current control
diesel generator
Diesel generators
Distributed generation
droop control
Eigenvalues
Emulators
Energy resources
Generators
Mathematical models
microgrid (MG)
Phase locked loops
phase-locked loop (PLL)
Power system stability
Renewable energy sources
Renewable resources
small-signal analysis
Stability analysis
Stator windings
Voltage control
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Summary:In recent years, microgrids (MGs) with renewable energy sources, diesel gen-sets, and droop-controlled converters have been increasingly used to guarantee the continuity of power supply in remote areas. Renewable energy sources have been typically connected to MGs by using an electronic converter that features the two controllers: a current-control loop and a phase-locked loop (PLL). Stability issues related to the PLLs application in electrical grids have already been addressed in the literature; however, dynamic interactions in MGs caused by PLLs have not been sufficiently explored. In this article, an MG that includes a grid-feeding voltage source converter and a grid-forming device (diesel gen-set or converter) is studied. All network elements are modeled analytically and the eigenvalue and participation-factor analyses are used to analyze the interactions between the devices. It is demonstrated that MGs formed by diesel gen-sets have reduced stability limits. Also, it is shown that stability margins of MGs formed by droop-controlled converters can be improved by changing the control parameters (e.g., PLL and internal controllers bandwidths). The main findings and conclusions are summarized and presented as a practical MG design guide. Theoretical results are validated in a lab environment comprising two 15 kW converters and one 75 kW grid emulator.
ISSN:0885-8993
1941-0107
DOI:10.1109/TPEL.2021.3127310