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Open-loop system and method for fuel cell stack start-up with low-voltage source

  • US 9,005,785 B2
  • Filed: 09/24/2007
  • Issued: 04/14/2015
  • Est. Priority Date: 09/24/2007
  • Status: Active Grant
First Claim
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1. A method for starting a fuel cell system having a fuel cell stack including a cathode inlet, an exhaust directly emitting from the fuel cell stack to an environment external to the fuel cell system, an air compressor in fluid communication with the cathode inlet and the exhaust, a low-voltage start-up battery in electrical communication with the air compressor, wherein the low-voltage start-up battery has an operating voltage less than a fuel cell stack operating voltage, a power conversion module in electrical communication with the low-voltage start-up battery and the air compressor, the power conversion module adapted to selectively boost a voltage of the low-voltage start-up battery supplied to the air compressor, the method comprising the steps of:

  • receiving a start request;

    enabling the power conversion module to boost the voltage of the low-voltage start-up battery;

    determining an available electrical energy from the boosted voltage of the low-voltage start-up battery;

    determining an estimated speed of the air compressor based on the available electrical energy;

    starting the air compressor and setting the air compressor at the estimated speed with a controller in communication with the power conversion module, wherein a flow of air bypasses the fuel cell stack and is provided to the exhaust by the compressor and no flow of air is provided to the fuel cell stack;

    measuring an actual speed of the air compressor using a speed sensor in communication with the controller and directly sensing a rotational speed of the air compressor, wherein the actual speed is the rotational speed of the air compressor;

    comparing the actual speed to a desired speed calculated from the estimated speed;

    scheduling an anode purge based on the available electrical energy when one of a) the actual speed is greater than the desired speed, and b) a compressor ramp-up time has elapsed, wherein the step of scheduling the anode purge includes at least one of i) setting a time for the anode purge, and ii) setting a flow rate for the anode purge, and wherein the anode purge flow rate is calculated from a look-up table based on the available electrical energy;

    purging an anode of the fuel cell stack; and

    providing a controlled flow of hydrogen to the anodes and diverting the flow of air from the exhaust to the cathode inlet.

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