Geographical smoothing effects on wind power output variation in Japan

There is a growing concern that the supply and demand operations of electric power systems will become more difficult with a large number of renewable energy sources whose outputs depend on the weather variations. To investigate the countermeasures that are required to stabilize the outputs of the power systems, it is important to quantitatively evaluate the wind power output fluctuations and variations corresponding to the supply-demand balancing controls, such as turbine governor control, load frequency control, and economic-load dispatching control (EDC). With an increasing number of wind power generators being installed, these fluctuations and variations with respect to the rated output capacity will decrease because of the geographical smoothing effects, i.e., the output fluctuations and variations of multiple wind turbines will mutually cancel one another. In this study, we quantitatively evaluate the geographical smoothing effects using the actual high time-resolution wind power output data of several wind farms that is recorded in the supervisory control and data acquisition systems of the Tohoku and Kyushu power systems in Japan. Further, we evaluate the smoothing effects pertaining to the introduced wind power using various approximation curves, and it is observed that the exponential parts of the approximation curves depend on the region and cycles. Using these exponential parts, we observe that perfect smoothing effects were obtained during the shorter periods of cycles. The smoothing effects of the fluctuations in the EDC domain are observed to be small, especially in the Tohoku region.