Design and implementation of a hybrid regenerative power system combining grid-tie and uninterruptible power supply functions

A hybrid regenerative power system including photovoltaic (PV) and wind powers and combining the functions of the grid-tie system and uninterruptible power supply (UPS) for critical load applications is presented. The proposed system employs six-arm converter topology with three arms for the rectifier-inverter, one arm for battery charging/discharging and two arms for power conversion of the PV module and wind turbine generator. The operation modes include the grid-tie mode and the UPS mode depending on the grid status. A power balance control scheme is presented, which can reduce the grid power and utilise the regenerative power in the most effective way for fulfilling the two requirements of a three-stage charging of the battery and no interruption of the load. Also, the PV and wind powers can be utilised with priority in order to provide the flexibility for adapting to local circumstances. A single-phase 1.2-kW/110-V system is designed and implemented, and the effectiveness of the proposed system and control methodology are verified with some experimental results.