A probabilistic model of a grid-connected wind power plant with energy storage

A new method is developed for finding an estimate for the average firm power output of a combined wind-storage power plant. The method is based on the probabilistic properties of wind speed, a wind power curve and a general representation of an energy storage unit. Firming of wind power by the use of energy storage is valuable in power systems with high wind penetration or costly balancing rules for intermittent generators. In addition, as described in the paper, the calculated firm power level is also a measure of the minimum required transmission capacity. Thus, energy storage is considered both for increasing the value of wind power in the power system and for reducing the amount of dissipated wind power due to transmission constraints. It is shown that if the wind speed follows a Weibull distribution with an expectation value of 8 m/s, the power rating of a storage system with reversible fuel cell does not need to be more than approximately 50% of rated wind power to provide sufficient firm power. If the storage system consists of individual charging and discharging devices, the charging and discharging capacity should be about 50 %, respectively 25 % of the rated wind power.