Charging and discharging strategies of grid-connected super-capacitor energy storage systems

The energy storage is an effective technique for smoothing out the power fluctuation of the renewable energy sources. Because a super-capacitor has a fast charging/ discharging capability, long cycle life, and low-energy capacity, the super-capacitor energy storage system (SCESS), which consists of the super-capacitor, bidirectional DC-DC converter, and grid-connected inverter, is able to ensure the power quality in a short duration of time. This paper proposes the control strategies of both the bidirectional DC-DC converter and grid-connected inverter for charging and discharging operations of the SCESS. The switching pattern for achieving the zero current switching (ZCS) commutation of the DC-DC converter in the charging mode is suggested in order to reduce the switching loss. The experimental results are carried out in order to validate the charging and discharging performances of the SCESS and the ZCS of bidirectional DC-DC converter.