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Electro-Thermal Modelling of an HVDC-Converter During Fault Conditions

David Eriksson ; Olle Nordqvist
Göteborg : Chalmers tekniska högskola, 2014. 64 s.
[Examensarbete på avancerad nivå]

This thesis investigates the electro-thermal stresses on the converter semiconductor components during surge currents events in a VSC HVDC-system using MMC topology. A typical HVDC-link is described and modelled in PSCAD simulation software and analytical calculations were performed alongside in order to confirm the simulated fault current peak values. Both the analytical calculations and simulations have shown that the most severe fault cases for the converter components are when faults occurs on DC-side of the converter, so called pole-to-pole and pole-to-ground faults. These fault currents are mainly conducted by the semiconductor diodes in the converter for which two different kinds of voltage drop models were derived - one extrapolated measurement based model and one physics based Lauritzen power diode model. The corresponding temperature response of the diode was simulated by a thermal model using Cauer electrical network representation. All models were created and combined in a Matlab/Simulink environment. The Lauritzen model has proven to give satisfying results in the transient electro-thermal investigation for surge currents with lower peak values. However, during higher surge currents, the model starts to deviate from the measurement based model and estimate larger losses. The parameter extraction process for the Lauritzen model is time consuming for a new component and if the model parameters does not already exist, the benefits compared to the measurement based model are negligible. Similar to the Laurtizen model, the extrapolated model with the three different types of temperature coefficient starts also to deviate for higher surge currents. Better knowledge of the temperature dependent voltage drop combined with more detailed measurements in higher current and temperature range are needed in order to achieve more accurate simulations.

Nyckelord: HVDC, MMC, Fault Analysis, Surge Current, Electro-Thermal Modelling, Semiconductors

Publikationen registrerades 2014-07-03. Den ändrades senast 2015-01-19

CPL ID: 200117

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