Research On Simultaneous AC-DC Transmission Technology In Medium And Low Voltage Distribution Network

For the fast development of China economy and the power grid,the resources of existing urban transmission corridor are becoming more and more scarce.Also,the traditional communication and distribution network transmission capacity is limited and new energy generation and DC load are increasing;Relevant scholars have studied the simultaneous AC-DC transmission technology in high voltage transmission network.To solve this problem mentioned above,this paper proposes a scheme as simultaneous AC-DC technology.The results include:(1)According to the special structure of the distribution network with multiple feeders,a new power distribution network with Zigzag transformer is proposed.In this paper,the topology of simultaneous AC-DC power distribution network is designed.The main equipment and electric quantity are analyzed,feasibility is testified based on the PSCAD/EMTDC simulation software.(2)In this paper,the Zigzag transformer is the key equipment.The principle and performance of Zigzag transformer are analyzed.Contrasted with ordinary transformer,the distortion degree of the excitation current of the Z transformer is analyzed by using PSCAD/EMTDC simulation software.The simulation results show that Zigzag transformer has obvious effect on the suppression of DC bias magnetic field and iron core saturation.(3)According to special structure of the distribution network,the condition of maximum power transmission and distribution and the superposition method of the AC and DC components is realized.Through numerical example,the results show that power distributed in AC-DC distribution network can be significantly improved,the scheme's theoretical feasibility is verified.(4)From the perspective of economy,comparison for AC-DC and traditional distribution scheme are conducted,considering the investment of the equipment after the transformation from power distribution network.Data analysis shows that simultaneous AC-DC power distribution network show great economic and superiority for improving the capacity of the existing power distribution lines and reducing equipment investment,no matter the AC and DC power or load ratio is ideal or not.Finally,conclusion and prospection of the research of this paper is discussed.