Penetration of wind power into electricity system is constantly increasing. Wind resources are usually distant from existing transmission lines. Wind farms are often connected to weak grids far from central generation stations. Maximum wind power extraction causes the more irregular and unpredicted power output of wind turbine, which has same nature as wind speed variation. The voltage in such long line is vulnerable with the consumption and generation imbalance. In a long line, the mid-line voltage is largely affected by the variation and the penetration of the wind fluctuating power. Fluctuating nature of wind power output and long transmission line have led to concern that the voltage disturbances impressed on the weak system may become unacceptable. Fluctuating power and X/R ratio are key contributors for unnecessary voltage fluctuation and variation along the feeder. Control of the wind power fluctuation and variation can prevent the excessive voltage fluctuation and variation in the system. The weak grid with a doubly fed induction generator (DFIG) wind turbine has a higher probability of the voltage variation due to the fluctuations of the wind speed and load demands. To compensate the variation of power and voltage in a weak grid system, an energy storage system can be designed to provide fast controllable responses. In this paper, effect of energy storage system for reduction of voltage variations has been investigated. The investigation has been carried out through modelling of a doubly fed wind turbine and an energy storage system using SimPowerSystems tools of MATLAB. 1.