Selection and Performance-Degradation Modeling of LiMO$_{2}$/Li$_{4}$Ti$_{5}$O $_{12}$ and LiFePO $_{4}$/C Battery Cells as Suitable Energy Storage Systems for Grid Integration With Wind Power Plants: An Example for the Primary Frequency Regulation Service

Advances in the development of energy storage technologies are making them attractive for grid integration together with wind power plants. Thus, the new system, the virtual power plant, is able to emulate the characteristics of today's conventional power plants. However, at present, energy storage devices are expensive and proper selection of the energy storage technology that is to be grid integrated with wind power plants is necessary. In this paper, a methodology for selection of the most suitable energy storage technology for grid integration with wind power plants is proposed. The selection process is service-oriented and thus the energy storage technology is selected based on certain requirement criteria. The primary frequency regulation service was chosen, for example, due to its potential economic benefits. For this service, low cost per cycle at partial charge/discharge was found as the requirement criterion while Li-ion batteries where found as the devices which could best fulfil this requirement. Since accurate and fast battery performance models are indispensable for studying the virtual power plant behavior under different operating conditions, impedance-based performance-degradation models were developed for the two most suitable Li-ion chemistries for the primary frequency regulation service: LiMO₂/Li₄Ti₅O₁₂ and LiFePO₄/C.