Enhanced loading ability of distribution system by concurrent AC-DC power transmission

By fast increment in demand of electrical energy and for rapid progress of nation, specifically in big cities, the erection of new transmission corridors are excessive urgent. But the mission is limited by the deficiency of right-of-ways for new transmission corridors. This drawback, limits the transmission ability between power plant and load end. Centered on zigzag transformer, this paper offers a concurrent AC-DC power transmission arrangement, a new circuit topology, in the distribution network by overlaying DC power flow on existing AC line. The mixed DC and AC current and merged voltage is controlled below thermal limits and the insulation level of the line respectively. No variations of conductor size, insulator discs, breaker capacity and tower structure are needed. As circuit is near to the conductor thermal limit in the AC-DC system, the capacity of transmission line is considerably improved. Scheme of concurrent AC-DC power transmission system applied in the distribution network is put forward and the extreme of the whole power transmitted by the system is studied theoretically and numerically. Simulation is also supplied.