| The engineering construction of±800kV ultra-high voltage direct current transmission in China is the first project of the same type in the world, which belongs to the important step of the national 21st century development strategic target-'Diversion of Electricity from the Western to the Eastern Regions'. It is very important to study on the key apparatus of HVDC project, namely, the converter transformer and its filtering equipments. This thesis combines with the'11th Five-Year plan'major project in Hunan province-'The Research and Manufacture of HVDC Converter Transformer'. This research has the important theoretical and engineering application value.The thesis analyses the present research situation and development tendency of±800kV ultra-high voltage direct current transmission technology first. Then put forth an UHVDC system based on a new converter transformer and its filtering equipments (abbr. the new±800kV direct current transmission system). The wiring layout, self-compensation and harmonic suppression of the new system is introduced; The harmonic characteristics of new system will be analyzed considering the commutation, which laid the theoretic foundation for the future synthetic design of inductive filtering equipment.At last, refer to the engineering parameters of the±800kV HVDC transmission project in our country recently, this paper respectively establishes the traditional and the new±800kV HVDC transmission analogue system's simulation model based on the new converter transformer with its inductive filtering equipment via Matlab/Simulink/PSB, and carries out detailed simulation and comparisons. The result shows that the main characteristic harmonics are suppressed in the valve side, and the adverse effects of the harmonic currents bring to the primary side of the transformers are reduced greatly and improves the valve line-voltage, which is good for converter's normal commutation and reliability. It can enhances the DC transmission system's stability.
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