Evaluation of Performance of DC DC test bed experiment

Abstract

newline quotIn this thesis, the use of direct current for medium-voltage distribution systems is investigated. Current trends in the electric power consumption indicate an ncreasing use of dc in end-user equipment, like computers and other electronic appliances used in households and offices, and in larger equipment used in the industry. With a dc distribution system, power conversion within the appliance can be avoided, and losses reduced. The ac/dc conversion is centralized, and by using a fully controllable power-electronic interface, high power quality for both the ac and the dc system during steady state and ac grid disturbances can be obtained. Connection of back-up energy storage and small-size generation is also easier to realize in a dc system. newline newlineThe construction of new overhead electric lines is increasing difficulty, thus there is a need to look at alternatives that increases the power transfer capability of the existing right of ways. It is technically feasible to achieve a substantial power upgrading of existing AC lines through their conversion for use with DC, by using the same conductors, tower bodies and foundations, but with changes in tower head and insulation assemblies. newline newline newlineWhen using existing AC lines to transmit DC power, the lines are already built, so that cost can be saved. The distribution networks cost is lower than the transmission ones, because of the lower voltage level applied to the semiconductor cost. It is also remarkable the fast development of multi terminal DC systems. DC transmission has many more advantages, such as stability, controlled emergency support and no contribution to short circuit level. newline newlineTo facilitate practical application, it is important that the shift from ac to dc distribution can be done with minimal changes. Results from measurements carried out on common household appliances reported in this thesis show that most loads are able to operate with dc supply without any modifications. Furthermore, the measurements are used to derive simple, yet sufficientl