SERIES - CONNECTED DC / DC CONVERTER FOR CONTROLLING THE POWER FLOW IN A HVDC POWER TRANSMISSION SYSTEM

摘要

An apparatus (302) for controlling the electric power transmission in a high voltage direct current, HVDC, power transmission system comprising at least one HVDC transmission line (102, 104, 106, 108, 110, 112, 114) for carrying direct current, wherein the apparatus (302) comprises a DC-to-DC converter (304) and a second converter (306) for converting alternating current to direct current and/or direct current to alternating current, the DC-to-DC converter having two DC sides for output and/or input of direct current, the second converter having an AC side (308) for output and/or input of alternating current and a DC side (310) for output and/or input of direct current. The DC-to-DC converter is connectable to the HVDC transmission line (102), and the second converter is connected via its DC side to the DC-to-DC converter. The second converter is connectable via its AC side to an AC source (314), and the apparatus is adapted to control the direct current of the HVDC transmission line by introducing a DC voltage in series with the HVDC transmission line. A HVDC power transmission system comprising the above-mentioned apparatus (302).