26-01-2010, 11:12 PM
Long extra high voltage (EHV) ac lines cannot be loaded to their thermal limits in order to keep sufficient margin against transient instability.by using this system it is possible to load these lines very close to their thermal limits. The conductors are allowed to carry usual ac along with dc superimposed on it. The added dc power flow does not cause any transient instability. Substantial gain in the loadability of the line is obtained. Master current controller senses ac current and regulates the dc current orders for converters online such that conductor current never exceeds its thermal limit and by using Fast controllability and modulation of DC component Loss of synchronism is prevented by quickly and producing sufficient decelerating energy to counteract accelerating energy gained during fault and subsequently due to loss of line after clearing the fault.
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http://www.scribddoc/22894025/1-Power-Up...ansmission
read full paper
http://www.scribddoc/22894025/1-Power-Up...ansmission