Design Considerations of a Long-Term Single-Phase Uninterruptible Power Supply Based on Fuel Cells

This paper presents the design of a long-term UPS system based on fuel cells which focused on the system´s architecture and its control. It presents the fuel cell electrical parameters obtained by two methods, one that interrupts the fuel cell current and measures its voltage, and the other that applies a small AC current perturbation and measures its voltage. Both methods were used to determine the fuel cell impedance. A UPS architecture was presented, emphasizing the difficulties involved in its selection, and a low cost DC-DC conversion solution was shown. The system´s architecture was designed to confine all the low frequency ripple current, not allowing it to circulate through the fuel cell. An energy storage stage was calculated based on the fuel cell and load behavior. The current transfer function of the DC-DC converter was presented which included the fuel cell model using actual parameters. At the end of the paper, the experimental results of the entire system were presented