Fault Impact Mitigation in Grid Connected Converters
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
The present thesis deals with fault impact mitigation in grid connected converters used for High Voltage Direct Current transmission. Certain critical fault cases require additional obstructing protection actions to ease the impact on the converter valves. DC sided faults drives high fault currents through the converters. Single phase to ground faults at the converter AC bus results in overvoltages across the converter valve arms. The phenomenon of these faults are described both for symmetric and asymmetric configurations. Different available solutions are explained and evaluated. Simulations in PSCAD/EMTDC show the impact of the protection measures. A three phase short circuit introduced on the tertiary winding of the transformer is an effective temporary measure against the destructive fault cases. It is shown in this report that a tertiary shortcircuit will greatly reduce the overvoltages after converter bus faults and redirect a large part of the fault currents after DC faults. With the lower voltage on the tertiary winding, it is a suitable connection point for short circuit devices.
Place, publisher, year, edition, pages
2012. , 40 p.
EES Examensarbete / Master Thesis, XR-EE-E2C 2012:013
AC/DC Converter, Grid Connected Converter, Fault Impact Mitigation, Converter Bus Fault, DC Fault, Fast Earthing Switch
Electrical Engineering, Electronic Engineering, Information Engineering
IdentifiersURN: urn:nbn:se:kth:diva-107494OAI: oai:DiVA.org:kth-107494DiVA: diva2:576284
Master of Science in Engineering - Electrical Engineering
Nee, Hans-Peter, Professor