Hybrid Energy Storage Systems integrating battery and Ultracapacitor for the PJM frequency regulation market

In this paper, the economic analysis on the utilization of the Hybrid Energy Storage System (HESS) for PJM frequency regulation market is performed. The HESS includes the Lithium-Ion battery and the Ultracapacitor (UC). A power sharing strategy is used to reduce the stress of the battery with the help of the UC. The frequency regulation signal from PJM is used as the system input, and a battery degradation model is used to calculate the battery life time. The results show that with 1% of UC added to the Energy Storage System (ESS), the battery life can be improved by 9.95% after 10 years of service. If the battery degradation is considered in the sizing of installed battery capacity, a proper combination of battery and UC can reduce the cost of the energy storage element in the ESS for up to 4.7%.