A Novel Super Capacitor Voltage Recovery in Virtual Capacitor Control

In recent years, with more integration of distributed generator(DG) and large number of DC loads into the power grid, DC microgrid has attracted more and more attention in the research field of micro-grid. Due to the inevitable volatility and randomness of renewable energy, battery is an essential element of DC microgrid, especially in islanded mode. To prevent the damage to battery caused by frequent and rapid charge and discharge, and consider the high power density of super capacitor(SC), some research combine battery and SC as hybrid energy storage system(HESS). In HESS, battery is under conventional droop control, and virtual capacitor control is also implemented in SC to simulate the output characteristics of DC bus capacitor and absorb transient power. This paper studies the equivalent leak current of SC and DC/DC convertor, and a novel SC voltage recovery method is proposed based on traditional virtual capacitor control. Finally, a simulation model was established in PSCAD/EMTDC to verify the proposed algorithm.