The design of a fuel-cell-based power-quality control center to realize unbundled power-quality supply

The application of a power-quality control center (PQCC) to provide an unbundled quality of electricity supply is examined. The center consists of back-to-back power converters, a dc bus and a solid-oxide fuel-cell distributed generator (SOFCDG). The purpose is to use the flexibility offered by the converters and SOFCDG to realize varied levels of ac supply quality to the loads. Through the concept of a feasible operating area of the SOFCDG, analysis shows that the ability of the PQCC to accommodate instantaneous power demand change is constrained. This is due to limits imposed on the fuel utilization factor of the SOFCDG. A feasible PQCC operating scheme is then proposed. It fully exploits the ability of the converters and the distributed generator to respond to external disturbances. In the event of a system voltage disturbance, the PQCC is to operate in one of two scenarios in accordance to the severity of the disturbance. Based on the dynamic model derived for the power network, a design procedure of the PQCC control system is also described. Simulation results show the efficacy of the proposed scheme.