Although the principle of DC bias current distribution calculation has been mature, there is still a lack of systematic methods for modeling, analysis and suppression of DC bias current in large AC power grid due to the large scale of AC ground grid, various operation modes and complex soil structure. Thus, this paper proposes a set of modeling analysis and optimal suppression methods for DC bias of large-scale AC power grid. The multi-stage strategy of combining simulation prediction and experimental observation is adopted to reduce the influence of simulation error and improve the effectiveness of the DC-bias suppression scheme. Finally, the application of the above method in the analysis and control of DC bias in Zhejiang power grid is introduced. The method proposed in this paper can provide method reference for DC bias analysis and control of large AC power grid.

DC bias; large AC power grid; multi-stage strategy; suppression scheme