Hierarchical and partitioning means of present voltage control is confronted with the problem of coordination among multiple coupled zones. From the perspective of game theory

the split zones are regarded as game players to develop an individual rationality based cooperative game model

in which the players seek efficient alliances to improve the control effect. Players in the same alliance have a common optimization objective

while in the sub-problem alliances play a noncooperative game

and the Nash equilibrium strategy would allow the secondary voltage control area to consider the interaction and coupling from elsewhere thus avoiding voltage oscillation and overshoot. A solution for nontransferable utility cooperative game is proposed

with the existence of Nash equilibrium in the sub-problem proved as well. Furthermore

steady-state simulation on an IEEE 39-bus system demonstrates that the cooperative game model can effectively coordinate reactive power sources to improve the technical specifications of secondary voltage control. This work is supported by National Natural Science Foundation of China(No. 51177049).