Especially, the installation of the wind power generation with high cost-effectiveness is top priority to solve exhaustion of fossil fuels, CO_2-reduction while the importance of renewable energy installation rises. However, the load change is absorbed with expanding the wind power installation in the electricity system. So, Electric Power Company cannot help limiting the wind power installation from the viewpoint of the frequency change control. Agency for Natural Resources and Energy came up with the method in 2004 and reported that the use of the ream system line between electric power companies and output fluctuation relief by battery energy storage system are efficient measures. At the same time, Tohoku Electric power Company accepted wind power connected candidates with this technical requirement in 2006. Therefore, our company has developed a wind power generation system by optimizing wind turbine power limitation system and battery energy storage system, and we have evaluated that performance by our simulation. After that, we have constructed the Shiura wind farm with this system in Gosyogawara city since April 2009, and now, commercial operation started in February 2010. In this thesis, we introduce the outline of our system and we report the evaluation of the output fluctuation actual data in the Shiura wind farm.