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<xml><records><RECORD><source-app name="Bibcite" version="8.x">Drupal-Bibcite</source-app><REFERENCE_TYPE>2</REFERENCE_TYPE><CONTRIBUTORS><AUTHORS><AUTHOR><style face="normal" font="default" size="100%">Arne Gloe</style></AUTHOR></AUTHORS></CONTRIBUTORS><TITLES><TITLE><style face="normal" font="default" size="100%">Influence of grid support functionalities on the mechanical loads and the energy yield of wind turbines</style></TITLE></TITLES><KEYWORDS/><DATES/><AUTHORS><style face="normal" font="default" size="100%"/></AUTHORS><YEAR><style face="normal" font="default" size="100%">2023</style></YEAR><SECONDARY_TITLE><style face="normal" font="default" size="100%">Department of Energy and Environmental Management</style></SECONDARY_TITLE><PLACE_PUBLISHED><style face="normal" font="default" size="100%">Flensburg</style></PLACE_PUBLISHED><PUBLISHER><style face="normal" font="default" size="100%">EUROPA-UNIVERSITÄT </style></PUBLISHER><VOLUME><style face="normal" font="default" size="100%">Ph.D.</style></VOLUME><PAGES><style face="normal" font="default" size="100%">199</style></PAGES><DATE><style face="normal" font="default" size="100%">12/2023</style></DATE><TYPE_OF_WORK><style face="normal" font="default" size="100%">Doctoral thesis</style></TYPE_OF_WORK><ABSTRACT><style face="normal" font="default" size="100%">&lt;p&gt;As the share of inverter connected generation increases in power systems, grid operators worldwide&lt;br /&gt;&#13;
increase their demand for system services by wind turbines. One of these services, grid frequency&lt;br /&gt;&#13;
control, is very challenging for wind turbines, as it requires a change of the active power of the wind&lt;br /&gt;&#13;
turbine. Furthermore, wind turbines are curtailed when the grid capacity is not sufficient to transport&lt;br /&gt;&#13;
the produced power: the so-called feed-in management. Hence, the control of the wind turbines has&lt;br /&gt;&#13;
to cope with the needs of the grid. Thus, the wind turbines are exposed to an additional external&lt;br /&gt;&#13;
excitation in addition to the prevailing wind conditions.&lt;br /&gt;&#13;
In this thesis, the influence of the providing these services on the wind turbine is analysed. The analysis&lt;br /&gt;&#13;
is based on time domain simulations of the wind turbine. The models were partly developed in this&lt;br /&gt;&#13;
project. Additionally, a focus is laid on analysing data to derive realistic scenarios of the grid signals. As&lt;br /&gt;&#13;
some of these signals were not available, several measurement had to be set up and maintained during&lt;br /&gt;&#13;
the project.&lt;br /&gt;&#13;
In a research project with the wind turbine manufacturer Suzlon Energy, a controller for providing&lt;br /&gt;&#13;
inertial response continuously was developed. In contrast to the state-of-the-art, the magnitude of the&lt;br /&gt;&#13;
inertial response is scaled with the operating point of the wind turbine in order to provide this service&lt;br /&gt;&#13;
reliably and at the same time to use the full potential of the wind turbine in strong wind conditions.&lt;br /&gt;&#13;
This controller is tested with grid frequency scenarios from Europe and India to identify the&lt;br /&gt;&#13;
consequences for the energy yield and the mechanical loads of the wind turbine. It is shown, that&lt;br /&gt;&#13;
neither the energy yield nor the loads are affected significantly.&lt;br /&gt;&#13;
During the research project, a grid islanding and eventually a blackout occurred in Flensburg. The local&lt;br /&gt;&#13;
grid operator provided data of the grid situation for the day of the blackout. This data allowed to&lt;br /&gt;&#13;
analyse the cause of the blackout and to develop fictive scenarios how wind turbines could have helped&lt;br /&gt;&#13;
to stabilize the islanded grid. In the analysed scenarios it was shown, that wind turbines equipped with&lt;br /&gt;&#13;
an inertial response and a fast frequency response controller could have stabilized the islanded grid&lt;br /&gt;&#13;
making a blackout less likely. However, the wind turbines were also at risk of running in overspeed, as&lt;br /&gt;&#13;
they had to reduce their power drastically when stabilizing the grid.&lt;br /&gt;&#13;
As a consequence of the overspeed problems, a feedforward loop for the pitch control was added to&lt;br /&gt;&#13;
the grid frequency support controller. It modifies the pitch angle signal from the feedback controller&lt;br /&gt;&#13;
by a signal depending on the pitch sensitivity and the magnitude of the power change for grid&lt;br /&gt;&#13;
frequency support. The proposed controller achieved to reduce the overspeed significantly.&lt;br /&gt;&#13;
In addition to the grid frequency support, a controller for continuous feed-in management was&lt;br /&gt;&#13;
developed at the institute. It was tested with a fictive case of a weak grid connection, which was&lt;br /&gt;&#13;
designed based on measurements at the campus in Flensburg. In comparison to the state-of-the-art&lt;br /&gt;&#13;
feed-in management, the controller allowed a higher energy yield of the wind turbine and a better&lt;br /&gt;&#13;
utilization of the grid components. The loads of the wind turbine were only slightly increased. Finally,&lt;br /&gt;&#13;
it is also shown, that feed-in management and inertial response can be provided by a wind turbine at&lt;br /&gt;&#13;
the same time, as the excitations and the wind turbine response are largely decoupled in the frequency&lt;br /&gt;&#13;
domain.&lt;br /&gt;&#13;
It is concluded that wind turbines can provide system services to a larger extend than today without&lt;br /&gt;&#13;
suffering from unduly harm for its mechanical loads and its energy yield.&lt;/p&gt;&#13;
</style></ABSTRACT><title><style face="normal" font="default" size="100%">Influence of grid support functionalities on the mechanical loads and the energy yield of wind turbines</style></title></RECORD></records></xml>
