Limiting Ramp Rate of Wind Power Output using a Battery Based on the Variance Gamma Process

Abstract

A battery system is designed to reduce violations of ramping limit due to severe and long ramps of wind power output. The power rating, battery capacity, and operational policies of the battery are decided based on the assumption that the wind power output follows the Variance Gamma (V.G.) process over short time interval. The histogram of the ramp rates of wind power follows the symmetric Laplace distribution. Furthermore, ramp rates have independent and stationary increments, and their variances are proportional to the time interval. Consequently, the wind power output can be modelled as a simple form of the V.G. process. Battery operational oplicies based on the V.G. process are tested using statistics representing the sum of all wind power outputs from wind farms in the Electric Reliability Council of Texas (ERCOT). It is found that the battery can essentially eliminate violations of ramping limits due to severe ramp events. Furthermore, in this operation, it is discovered that the power rating influences the ramp limiting performance of the battery more than battery storage rating.