The increasing penetration of wind power to the electrical grid leads to the need of a stronger contribution of wind turbines to grid control, concerning quality and stability. For the purpose of controlling the active power injection, depending on the needs of the grid and not depending on the power generation, energy storage systems can be used. In this paper this kind of system with a bidirectional interleaved DC/DC-converter and electric double-layer capacitors as storage technology is investigated. The dimensioning of the converter's main elements and its performance for three- and four-phase interleaved configurations is studied and compared. Simulations are carried out in MATLAB/Simulink/Plecs.