Print Email Facebook Twitter Mitigation of Voltage Sags in Industrial Power Plants with Medium Voltage DC Distribution System Title Mitigation of Voltage Sags in Industrial Power Plants with Medium Voltage DC Distribution System Author Weverink, M.L.M. Faculty Electrical Engineering, Mathematics and Computer Science Department Electrical Power Processing Date 2009-05-18 Abstract Unplanned downtime in industrial power systems causes high loss of revenues. These downtimes are often caused by voltage sags of durations up to 1 s. Currently many systems exist which can help to mitigate these voltage sags such as Dynamic Voltage Restorer, UPS and FACTS based devices. With the recent development in semiconductors the voltage-source-converter based high-voltage direct-current (VSC-HVDC) system has also become feasible to deal with power quality problems. With the Siemens Multifunctional Power Link (SIPLINK) also industrial customers can benefit from the advantages of the VSC technology. These benefits are due to the VSC making use of pulse width modulation (PWM) and are amongst others short circuit reduction and independent control of active and reactive power. In this thesis the applicability of SIPLINK to mitigate voltage sags in an industrial power system is studied. Two different solutions are researched which make use of the VSC technology. One solution is based on the current rating of the converters such that the converter can continue to extract nominal power from the grid in an undervoltage situation. This method is called overrating of the system. The other is based on an auxiliary supply containing supercapacitors to replenish the grid power that is reduced during undervoltage. The research is carried on in Matlab/Simulink making use of the SimPowerSystems package. An industrial grid with three medium voltage induction motors serves as a base case for these two solutions. The important parameter to be monitored will be the speed of the motors during a sag with and without mitigation of any form. To simulate the applicability of an overrated SIPLINK to mitigate sags a symmetrical voltage sag of 45% (i.e. 55 % remaining voltage) is applied to the grid that lasts 50 ms and another that lasts 1 s. The results will show that an 80% overrated converter is enough to mitigate these sags. To test the applicability of sag mitigation by supercapacitor, symmetrical voltage sags of 90% and 10% are applied to the grid each lasting 50 ms and 1 s. The results will show that fast mitigation can be accomplished this way. Subject VSC-HVDCVector controllerVoltage sagsSupercapacitor To reference this document use: http://resolver.tudelft.nl/uuid:5abacd05-9ff1-4ef7-994a-ab2fab26588f Embargo date 2009-05-20 Part of collection Student theses Document type master thesis Rights (c) 2009 Weverink, M.L.M. Files PDF Thesis_M_Weverink.pdf 2.5 MB Close viewer /islandora/object/uuid:5abacd05-9ff1-4ef7-994a-ab2fab26588f/datastream/OBJ/view