Researches On The High Orders Harmonics And Their Filters In UHVDC Transmission Systems

A great deal of high Orders harmonics at the both sides of converter stations during the operation of Ultra High Voltage Direct Current(UHVDC) transmission systems must be restrained by high frequence filters.Baesd on the±800kV Xiangjiaba-Shanghai UHVDC transmission project,the high frequence model of two 12-pulse converter valves of UHVDC transmission system is built and the high orders harmonics produced by converter valves are calculated.At the direct current side,the radio interferences brought by converter valves are compared with another radio interferences generated by corona from direct current overhead lines.By comparison,it is seen that the converter valves are not the main source of radio interferences at the terminals of the polar line.At the alternating current side,the attenuation ability of ac overhead lines about power line carrier interferences is also reckoned.According to the calculation results,the converter stations equipped without ac power line carrier filters in several cases.Finally,the high frequence filters are designed. The high orders harmonics no exceed the limits if the high frequence filters are operated.