Characteristics of Major EMD Sources in HVDC Converter Stations

A method of time-domain wide-band circuit simulation based on Electromagnetic Transient Program(EMTP) was used to analyze the conducted electromagnetic disturbance(EMD) caused by valve operations(turn-on and turn-off),the frequency band covers up to several MHz,while a method based on the Method of Moments(MOM) was adopted to calculate radiated EMD,which is much more significant at about several MHz.This is the most important EMD source during the steady state.Characteristics of the EMD caused by transient processes of switching operations were analyzed based on tests.It is shown that damping oscillatory waves are generated in secondary cables.The major frequency is about 0.4 MHz to 2 MHz and the amplitude is about several hundred volts.Because of the high corona inception voltage of DC tube buses,the radio frequency disturbance level caused by the corona phenomenon in DC yards is relatively low.