High-voltage Direct Current Transmission System Imbalance Runtime Dc Current Distribution Rule And Dc Bias Phenomenon Analysis

With the development of the high voltage direct current transmission in our country,transformer dc bias become increasingly apparent because of the dc systemmonopole-ground operation mode. Transformer neutral point current as the directinfluence factors of transformer dc bias condition, reflected the transformer dc biascondition, Therefore how to calculate fully exchange network in power system angles ofeach transformer neutral point current distribution, depth analysis of transformer dc currentdistribution mechanism is the grid development needs.In order to reveal the internal relationship between system operation mode and DC bias,we collected the actual data of AC/DC transmission program in Yichang power grid, byusing the method of AC system network modeling, DC bias current distribution simulationmodel which contain two500kV DC transmission lines and all the220kV transformersnear the grounding pole is established based on PSCAD/EMTDC. Compare the result ofsimulation model and the measured date under specific status, it shows that the establishedmodel has high accuracy. Besides, by simulating the DC current distribution in everyspecific transformer neutral point under the action of single grounding and doublegrounding pole respectively, this paper find the root reason of different distributioncharacteristics of DC current in transformer neutral point, which can provide the theorybasis for control the DC bias from the perspective of system.