Abstract
The feasibility of power transfer enhancement, through simultaneous AC–DC power transmission in a two-terminal transmission network, has been proposed earlier by the authors, and the concept is well established. To meet the increase in demand for electricity, a new technique is proposed in this article to increase the use of existing transmission lines in addition to independent control of AC and DC power flow. This paper extends the concept to a three-terminal transmission network by considering a power tapping from the middle of the line. DC is also superimposed in the already existing three-terminal AC transmission system. In the proposed topology, a multi-terminal simultaneous AC–DC system is used, which is integrated with a zig-zag transformer and more than two voltage source converter (VSC) stations. Each terminal may represent an area of the power system. Anyone/two-terminal(s) may act as sending end, whereas the remaining two/one terminal(s) may act as receiving end. Power can flow in either direction through each segment of the transmission system. At sending end, VSC converts a part of AC to DC and injects it into the neutral of the zig-zag transformer. On receiving terminal, DC power is tapped from neutral of zig-zag transformer and fed to VSC for conversion back to AC. The concept is verified in the digital simulation software PSCAD/EMTDC.
Highlights
The maximum power transmission through the existing long AC transmission lines is restricted due to stability considerations, as it is not possible to load long extra-high voltage (EHV) AC transmission lines to their thermal limits to maintain a necessary stability margin [1,2,3]
Flexible alternating current transmission system (FACTS) devices are used in the power transmission system to improve power transfer capacity and reliability
The commercial high voltage DC power transmission was developed for submarines
Summary
The maximum power transmission through the existing long AC transmission lines is restricted due to stability considerations, as it is not possible to load long extra-high voltage (EHV) AC transmission lines to their thermal limits to maintain a necessary stability margin [1,2,3]. The development of voltage source converter for high-voltage, direct current (VSC–HVDC) has helped to remove most of the difficulties of conventional HVDC and led to open new possibilities and new areas of applications [7]. This state-of-the-art technology comanpdrilseeds tao tohpreene-pnhewaseposswsiibtcihli-tmiesodane dconnevweratreeratshoaft aepmpplilcoaytisonpsul[s7e]. LIinnethies aplrsooppoossesdibslceh.eTmhe,perninhcainpcaelment of power benefits of thistsrcahnesmfeer awrieththoautttrheevpisoinwgerthtreaenxsifsetrincgapEaHciVtyAoCf tlhineeliniseailssoimpporsosvibelde.rTemhearpkr-incipal benefits ably, and the troafntshiiesnstcshteambielitayreotfhtahtetshyespteomweisr btroaonsstfeedr cuapp[a1c5it–y18o]f.the line is improved remarkably, and This papetrhienttrraondsuiecnest satatbhirleitey-toefrmthiensayl,stseimuisltabnoeoostuesdAuCp–[D15C–1p8o].wer transmission system to enhance Tthheisppoawpeerr tirnatnrosfdeurcceaspaabthilrietye-otefrtmheinlainl,esiimn ualdtadniteionustoAiCn–dDepCenpdowenetr transmission control of AC asynsdteDmCtpooewnhera.nTcheitshreespuolwtseirnttrhaensefceorncoampaicbiolpiteyraotfiothneolfintheeinsyasdtedmiti.oTnhteo independent proposed contrcolnstrcohleomfeAuCseadndthDreCe pzoigw-zear.gTthraisnrsefosurmltserisn, tihnestecaodnofmaicsotapnedratridontroafnsth- e system.
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