The main problem of renewable energy sources is their intermittency. Integration of energy storage devices with renewable energy systems can offer solution to this problem simply by storing excess produced energy for utilization when needed later on. Energy storage devices are also essential for other applications such as automotive. Accurate knowledge of the electrical attributes and expected response of an energy storage device is of high importance when it is utilized in any power system in order to attain proper charging/discharging without inflicting damages. In this paper, a relatively new type of energy storage device, Li-ion ultracapacitor, is thoroughly studied. This type of ultracapacitors has high energy density, high power density, high efficiency, and long cycle life. Testing, analysis, and modeling of this energy storage device are presented in detail. A series of DC and AC tests has been conducted to develop an electrical model, which has been verified for accuracy by simulation and comparison with test results.
