High performance fuel cell power generation system for stand-alone applications

Fuel Cell (FC) power generation for stand-alone applications such as residential power supply, building power generation (for hospitals, office buildings, schools, and airports), and portable power supply have the potential to meet high energy standards comprising high conversion efficiency, low emissions, and quiet operation. The strong interaction between the load, power conditioning stage, and FC system makes the design and coordinated operation a remarkable challenge in stand-alone applications. In this thesis, a detailed description of a high-performance FC power conversion system is presented. Key aspects such as power extraction, efficiency, dynamic response, monitoring, and power quality are addressed as part of this work. -- An advanced isolated dc-dc power converter topology and control scheme is proposed to address minimization of power losses and switching stress in the entire range of operation of the system. Architectural and control aspects (dynamic behavior) of the generation system are investigated at the system level with the objective of reducing the effect of low frequency ripple current in the FC. The concept of swinging bus is introduced and characterized to absorb the inverter ripple current. A novel control strategy based on curved switching surfaces is investigated to control the inverter stage, producing high quality output power while rejecting the fluctuations in the swinging bus. In addition, an innovative feature is incorporated to perform on-line monitoring and diagnosis of the FC stack. This critical component based on frequency response analysis is required to realize a fully functional system and has not been addressed in previous FC power conversion systems