Synthetic Testing of High Voltage Direct Current Circuit Breakers

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Abstract

The UK is facing two major challenges in the development of its electricitynetwork. First, two thirds of the existing power stations are expected to close by2030. Second, is the requirement to reduce its CO2 emissions by 80% by 2050.Both of these challenges are significant in their own right. The fact that they areoccurring at the same time, generates a significant amount of threats to theexisting power system, but also provides many new opportunities.In order to meet both these challenges, significant amounts of offshore windgeneration has been installed in the UK. For the wind generation with thelongest connections to land, Voltage Source Converter (VSC) based HighVoltage Direct Current (HVDC) transmission has to be used.Due to the high power rating of the offshore wind farms, compared to the limitedtransmission capacity of the links, a large number of point-to-point connectionsare required. This has lead to the concept of HVDC grids being proposed, inorder to reduce the amount of installed assets required.HVDC grids are a new transmission environment and the fundamental questionof how they will protect themselves must be answered. Several newtechnologies are under consideration to provide this protection, one of which isthe HVDC circuit breaker.As HVDC circuit breakers are a new technology, they must be tested in alaboratory environment to prove their operation and improve their TechnologyReadiness Level (TRL). This thesis is concerned with how such HVDC circuitbreakers are operated, rated, and tested in a laboratory environment.A review of the existing circuit breaker technologies is given, along withdescriptions of several novel circuit breakers developed in this thesis. Astandardized method of rating DC circuit breaker and their associated testcircuit is developed.Mathematical analysis of several circuit breakers is derived from first principlesand low power prototypes are developed to validate these design concepts. Ahigh power test circuit is then constructed and a semiconductor circuit

Keyword(s)

Control VSC; Fault; HVDC Circuit Breakers; HVDC Grid; Voltage Source Converters

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