| 摘要 |
A PEM-fuel-cell-stack backup electric generator comprising: a fuel-cell stack, formed by a plurality of stacked PEM fuel cells electrically connected in series for supplying electrical energy to an electrical load; a cell-voltage monitor for measuring the voltage supplied by each fuel cell; an electrical-energy management and conditioning unit, connected between the fuel-cell stack and the electrical load; a blower for supplying the amount of air necessary for the chemical reactions that occur in the fuel cells; a hydrogen recirculator for recirculating hydrogen between the outlet and the inlet of the fuel-cell stack; a hydrogen-purging device for carrying out a primary purging of hydrogen at a lower flow rate, and a secondary purging of hydrogen at a higher flow rate; and a controller, programmed for managing operation of the electric generator differently at start-up, at shut-down, and during normal operation thereof. |
| 主权项 |
1. A procedure for controlling a PEM-fuel-cell-stack backup electric generator (1), said backup electric generator (1) comprising:
a controller (11) operated by a loaded software configured for managing operations of said backup electric generator (1) to supply electrical energy to an electric load, said operations comprising: an automatic startup operation thus allowing the PEM-fuel-cell-stack electric generator (1) to function as a backup electric generator in the event of lack of mains electric supply; a normal operation a shut-down operation; a fuel-cell stack (2) formed by a plurality of stacked PEM fuel cells (3), electrically connected in series, a cell-voltage monitor (4) for measuring the voltage supplied by each fuel cell (3), measured at a frequency of 20 ms; an electrical-energy management and conditioning unit (5), connected in between the fuel-cell stack (2) and the electrical load; to measure the electric current supplied by the fuel-cell stack (2) and causing said fuel-cell stack (2) to supply electrical power required by the electrical load; and wherein said electrical-energy management and conditioning unit (5) comprises static elements for conversion of the electrical energy, such as semiconductor devices, inductive and capacitive reactances connected according to a topology of a boost or buck converter, able to convert the electrical energy by varying the voltage and current thereof; namely, one of the two values is varied independently and the other as a consequence of the electric-power demand; a blower (6) for supplying the amount of air necessary for the chemical reactions that occur in the fuel cells (3); a hydrogen recirculator (7) for recirculating hydrogen between the outlet and the inlet of the fuel-cell stack (2); and increasing the pressure of the hydrogen between the outlet and the inlet of the fuel-cell stack (2); a hydrogen-purging device (8), configured for carrying out a primary purging of hydrogen at a lower flow rate by opening a primary hydrogen-purging valve (9) and keeping it open, and a secondary purging of hydrogen at a higher flow rate by opening and closing a secondary hydrogen-purging valve (10); and wherein said controller (11), is connected to the cell-voltage monitor (4), the electrical-energy management and conditioning unit (5), the blower (6), the hydrogen recirculator (7), and the hydrogen-purging device (8) wherein said controller (11) is configured for managing the automatic start-up of the electric generator (1) by implementing the following operations:
controlling the purging device (8) in such a way as to carry out a continuous primary purging of hydrogen; by opening the hydrogen-purging valve (9) and increasing the pressure of the hydrogen recirculated from an outlet to an inlet of the fuel-cell stack (2)controlling the purging device (8) in such a way as to carry out a cyclic secondary purging of hydrogen according to a duty cycle, cyclically opening and closing the secondary hydrogen-purging valve (10), in which, starting from a given initial value, the purging time is increased by a given amount at each duty cycle, until one of the following conditions is verified:the voltage of a fuel cell (3) is lower than a given minimum admissible voltage;the voltage of a fuel cell (3) varies, with respect to reference values, by an amount greater than a given maximum admissible variation;the voltage of the fuel-cell stack (2) varies, with respect to reference values, by an amount greater than a given maximum admissible variation for a time longer than a maximum admissible time; and for a time longer than a maximum admissible time has elapsed from turning-on of the electric generator (1). |
