Stability Analysis of Fully Power Converter-based Microgrids

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dc.contributorAalto-yliopistofi
dc.contributorAalto Universityen
dc.contributor.advisorQvintus, Mikko
dc.contributor.authorMurugesan, Vishnukumar
dc.contributor.schoolSähkötekniikan korkeakoulufi
dc.contributor.supervisorPouresmaeil, Edris
dc.date.accessioned2019-10-27T18:01:21Z
dc.date.available2019-10-27T18:01:21Z
dc.date.issued2019-10-21
dc.description.abstractDue to rising energy demand and climate crisis, distributed energy generation utilizing the renewable energy resource is constantly evolving. Generation near the electrical loads within a defined boundary forms a microgrid. It can be operated by connecting with utility-grid or as a stand-alone system. Solar and wind energy resources use a power-electronic converter to interface with the load or grid. The fast dynamics of the converter is very different from the inertial dynamics of the grid with large synchronous machines. Furthermore, low short-circuit capacity, more resistive network and unbalanced loading are few inherent characteristics concerning the operational reliability of the microgrid. This thesis aims to present the various issues with fully power converter-based microgrids in terms of stability and protection. High-power converters with LCL-filter are simulated under various operating conditions in typhoon real-time simulator. A relay function is used to detect the unstable operating points. High resistance-to-reactance ratio in the low-voltage line forms active-reactive power coupling, making the conventional droop control inaccurate. For a disturbance, droop control allows a steep voltage or frequency deviations which lead to unnecessary protection tripping. Use of virtual inertia control avoids the steep change in the system variables and preserves the stability. Parallel droop-based converters with non-identical parameters or output impedance induce circulating current or reactive power oscillations. Use of virtual impedance control minimizes the circulating current and enhances power-sharing. Phase-locked loop synchronized with a weak grid (high-impedance grid) is unstable on large-signal disturbances. Current-reference saturation limits the converter current for a three-phase balanced fault condition. For higher fault-impedance, the fault current is nearly equal to the load current, which possibly blinds the microgrid protection.en
dc.format.extent81+12
dc.format.mimetypeapplication/pdfen
dc.identifier.urihttps://aaltodoc.aalto.fi/handle/123456789/40780
dc.identifier.urnURN:NBN:fi:aalto-201910275784
dc.language.isoenen
dc.locationP1fi
dc.programmeAEE - Master’s Programme in Automation and Electrical Engineering (TS2013)fi
dc.programme.majorElectrical Power and Energy Engineeringfi
dc.programme.mcodeELEC3024fi
dc.subject.keywordpower converter-based microgriden
dc.subject.keywordgrid-formingen
dc.subject.keywordweak griden
dc.subject.keyworddroop controlen
dc.subject.keywordvirtual inertia emulationen
dc.titleStability Analysis of Fully Power Converter-based Microgridsen
dc.typeG2 Pro gradu, diplomityöfi
dc.type.ontasotMaster's thesisen
dc.type.ontasotDiplomityöfi
local.aalto.electroniconlyyes
local.aalto.openaccessyes
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