The hybrid HVDC transmission using Line Commutated Converter and Full Bridge Modular Multilevel Converter

With its advantages of relatively low cost and mature technology, Line Commutated Converter based HVDC (LCC-HVDC)had been well developed in all around the world. However, its need for absorbing large amounts of reactive power and the risk of commutation failure have limited its further development. Meanwhile, the Full-Bridge Modular Multilevel Converter based HVDC (FBMMC-HVDC) was adopted on account of its flexible operating control characteristic, independent control ability of active power and independent control ability of reactive power, while its relatively high cost has been criticized. Therefore, the paper proposes the New Hybrid High Voltage Direct Voltage (NH-HVDC) system which combines the advantages of the both ones. The proposed NH-HVDC is able to achieve power reversal without the need for the power cut or the high speed switches, which can´t be realized in ever proposed H-HVDC. The paper analyzes the mathematical model of NH-HVDC, designs the appropriate control scheme and the operating principles and methods of power reversal for it. Based on the PSCAD/EMTDC, a NH-HVDC model with ±400kV DC voltage is built. The results show that the NH-HVDC system can operate stably and has the ability of power reversal.