Abstract: Aiming at the problem of reactive power distribution in the current reactive power-voltage control in the large-scale wind power collection system, this paper first defines the reactive power imbalance and the reactive power circulation of the wind farm, and gives the evaluation index of the reactive power imbalance. Then, the influence of the existing voltage command calculation methods and the different reactive power control cycles on the reactive power balance is discussed. A secondary voltage control optimization model that considers reactive power imbalance and voltage deviation of Convergence Node is proposed, and the corresponding solution is given. Based on this optimization model, the existing wind farm reactive power and voltage control process is improved and the reactive power imbalance constraint is considered in the process. When the index of the reactive power imbalance is too large, the constant reactive power control is used to adjust the reactive power. Finally, based on a wind farm cluster in the north of Hebei province, it is verified that the proposed strategy is able to reduce the reactive power imbalance and suppress the reactive power circulation under the premise of ensuring the accuracy of the Convergence Node voltage control.