Management of Operation of PEM-Fuel-Cell-Stack Backup Electric Generator

A PEM-fuel-cell-stack backup electric generator (1) comprising:

• a fuel-cell stack (2) formed by a plurality of stacked PEM fuel cells (3), electrically connected in series for supplying electrical energy to an electrical load;
• a cell-voltage monitor (4) for measuring the voltage supplied by each fuel cell (3);
• an electrical-energy management and conditioning unit (5), connected between the fuel-cell stack (2) and the electrical load;
• 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);
• a hydrogen-purging device (8), configured 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 (11), which 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) and is configured for managing operation of the electric generator (1) differently at start-up, at shut-down, and during normal operation thereof, said generator being characterized in that said controller (11) is moreover configured for managing 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;
• and
• controlling the purging device (8) in such a way as to carry out a cyclic secondary purging of hydrogen according to a duty cycle, 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
• a time longer than a maximum admissible time has elapsed from turning-on of the electric generator (1).