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@PHDTHESIS{Gurumurthy:1014325,
author = {Gurumurthy, Sriram Karthik},
othercontributors = {Monti, Antonello and Liserre, Marco},
title = {{A}dvanced harmonic stability monitoring and control of
power-electronics dominated grids; 1. {A}uflage},
volume = {141},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {E.ON Energy Research Center, RWTH Aachen University},
reportid = {RWTH-2025-06020},
isbn = {978-3-948234-55-3},
series = {E.ON Energy Research Center},
pages = {1 Online-Ressource : Illustrationen},
year = {2025},
note = {Druckausgabe: 2025. - Auch veröffentlicht auf dem
Publikationsserver der RWTH Aachen University; Dissertation,
RWTH Aachen University, 2024},
abstract = {A new paradigm has emerged with the increased proliferation
of renewable energy sources (RES), which is enabled by the
large-scale integration of grid-connected power electronic
converters. These power electronic-dominated grids (PEDGs)
pose new challenges to stability over a wide range of
frequencies. Interaction among the power
electronic-interfaced sources and non-linear loads may lead
to the presence of undesirable harmonics and
inter-harmonics, which distort the grid voltage and affect
power quality. Depending on the operating conditions and
damping in the power system, these inter-harmonics could
remain sustained and resonate; the harmonic content may
increase over a period, cause tripping of breakers, and
potentially fully destabilize the grid. This phenomenon is
known as harmonic instability. Due to the growing number of
instances and failures experienced by grid operators, it is
essential to develop methods to monitor and detect harmonic
stability conditions. Over the last decade, several research
studies have identified that harmonic stability can be
characterized as an impedance phenomenon, and thus the
impedance of converters would be required. Converter
manufacturers protect the hardware and control systems of
converters through Intellectual Property Rights (IPR), and
thus black-box or non-parametric models of converters are
required. Consequently, the choice of measurement method for
rapid impedance extraction becomes vital, as does the
characterization of such measurement devices. Aggregation of
the extracted impedance data on a system level is crucial
for system-level harmonic stability studies. To address
harmonic stability issues, local compensation schemes are
necessary to adjust the impedance of power converters and
effectively introduce the desired damping. This dissertation
aims to develop a standalone impedance measurement device, a
harmonic stability monitoring algorithm for a multi-bus
network, and a harmonic instability mitigation method. This
dissertation proposes four major scientific contributions
which enable harmonic stability monitoring and a safe
operation of PEDGs: 1) a standalone impedance measurement
device to extract the grid impedance in a non-parametric
manner; 2) a Frequency Coupling Matrix (FCM) measurement
method for power converters; 3) a non-parametric harmonic
stability monitoring method for multi-bus power systems; and
4) an advanced virtual damping control strategy for
grid-connected power electronic converters. The initial part
of the thesis deals with the measurement of non-parametric
impedances. A standalone plug-play measurement device called
Wideband-frequency Grid Impedance (WFZ) measurement device
is developed for the measurement of grid impedances. A
low-power prototype of the proposed device is constructed.
Linear impedance measurement is verified formerly by
simulations followed by experimental measurements.
Uncertainty characterization of the WFZ device is performed
to validate the device. The second part of this thesis
considers non-linearity through the FCM and extends the
measurement algorithm of the WFZ device to accommodate FCM
measurements. Characterization parameters are developed for
the analysis and interpretation of the extracted FCM.
Simulative and experimental measurements were carried out to
extract the FCM of a grid-connected converter, followed by
validation of the extracted FCM. The third part of the
thesis proposes a non-parametric harmonic stability
monitoring method. The proposed method requires
non-parametric impedance measurements of active components
in the network. A bus admittance matrix approach is
considered to aggregate the non-parametric impedances of the
power converters within the network. The proposed method
enables the calculation of the minimum phase margin and the
critical frequency where damping is required. The
effectiveness of the method is demonstrated empirically
through validation on both star and meshed power networks,
showcasing its broad applicability across different network
configurations. In the last part of the thesis, a
non-parametric approach to harmonic instability mitigation
is proposed. The proposed method consists of a centralized
non-parametric stability monitoring tool that identifies the
critical frequency and bandwidth, which are then published
to the local converters. The converters implement the
damping through the proposed adaptive Virtual Damping
Controller, which is implemented as a digital Infinite
Impulse Response (IIR) filter with adaptive parameters such
as the critical frequency and bandwidth; furthermore, a
look-up table-based approach is proposed to select the
optimal gain of the VDC based on the critical frequency and
bandwidth. The proposed VDC controller only requires grid
current measurement, establishing a two-degree-of-freedom
(2-DoF) control structure. Experimental validations were
conducted to show the efficacy of the proposed approach.
This thesis makes significant contributions in the areas of
impedance measurement devices, system-level monitoring of
harmonic stability, and the development of an advanced VDC,
resulting in advancements in these fields.},
cin = {616310 / 080052},
ddc = {621.3},
cid = {$I:(DE-82)616310_20140620$ / $I:(DE-82)080052_20160101$},
pnm = {RE-SERVE - Renewables in a Stable Electric Grid (727481) /
TWINECS - Toward a Digital Twin ECS and thermal management
architecture models: Improvement of MODELICA libraries and
usage of Deep Learning technics (886533) / DFG project
G:(GEPRIS)432169785 - REDeFiNE -- Reflex-basierte, verteilte
Frequenzregelung für Stromnetze (432169785) / BMBF
03SFK1C0-03 - Verbundvorhaben ENSURE3: Neue
EnergieNetzStruktURen für die Energiewende - Phase 3
(03SFK1C0-03) / BMBF 03HY128A - Verbundvorhaben HYPOWER -
Elektrische Integration von Groß-Elektrolysen in das
Stromnetz auf Basis einer 100 MW Elektrolyse.
(Unterstützung für H2Giga) (03HY128A) / SPP 1914:
Cyber-Physical Networking (CPN)},
pid = {G:(EU-Grant)727481 / G:(EU-Grant)886533 /
G:(GEPRIS)432169785 / G:(BMBF)03SFK1C0-03 / G:(BMBF)03HY128A
/ G:(GEPRIS)273882191},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
doi = {10.18154/RWTH-2025-06020},
url = {https://publications.rwth-aachen.de/record/1014325},
}
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