The novel intermediate compound which can be efficiently utilized in the synthesis of carotenoid compounds based on the sulfone chemistry, the preparation method of the same, and the practical synthetic process for preparing .beta.-carotene by the use of the above novel compound are disclosed. The synthesis of .beta.-carotene is characterized by the double elimination reactions of the C.sub.40 compound containing both the benzenesulfonyl group and the group X (either halogen or ether), which can...

A DC power transmission system of a voltage source converter using a pulse-interleaving auxiliary circuit is disclosed. The converter system comprises an IGBT converter for converting an AC power to a DC power or the DC power to the AC power; an open Y-Y transformer and a Y-.DELTA. transformer for stepping up or stepping down the AC power having a predetermined magnitude; a capacitor for dividing a DC voltage; and a DC Auxiliary circuit composed of a normal transformer and half-bridge for overla...