Voltage control is one of the most important issues in smart grids. Using the communication infrastructure and management that created in smart grids, end-user reactive power capable device can be coordinated for voltage support. Application and implementation of smart grids cause a fundamental change in the methods of reducing and eliminating voltage issues in distribution grids. Due to increasing role of Distributed Generations in distribution grids, by using traditional control methods, voltage issues cannot be improved desirably. In this paper a decentralized control scheme is proposed to control voltage in distribution grids. In this decentralized method, each network bus is equipped with a sensor and an oscillator to measure required parameters. It is shown that by using local coupling method, one can design the network without the need for a central controller. Genetic Algorithm is used as optimization method aimed at identifying the optimal asset of the voltage controllers. To verify the method, it is applied on the IEEE 33bus system (unbalanced case).I.