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

Abstract

A fuel cell system is provided that includes a fuel cell stack and an air compressor in communication with a cathode inlet, a hydrogen source in communication with an anode inlet, and a start-up battery adapted to power the air compressor. The start-up battery is at least one of a low-voltage battery and a high-voltage battery. A power conversion module is in electrical communication with the start-up battery and the air compressor. The power conversion module is adapted to boost a voltage of the start-up battery as desired and power the air compressor at start-up. A controller is in communication with the power conversion module and is adapted to set an air compressor speed based on an available electrical energy. An open-loop method of operating the fuel cell system at start-up is also provided, wherein an anode purge is scheduled based on the available electrical energy from the battery.

What is claimed is: 
     
         1 . A fuel cell system comprising:
 a fuel cell stack including a plurality of fuel cells and having an anode inlet and a cathode inlet;   an air compressor in fluid communication with the cathode inlet;   a hydrogen source in fluid communication with the anode inlet;   a start-up battery in electrical communication with the air compressor;   a power conversion module in electrical communication with the start-up battery and the air compressor, the power conversion module configured to selectively boost a voltage of the start-up battery supplied to the air compressor; and   a controller in electrical communication with the power conversion module configured to set an air compressor speed based on an electrical energy available at the compressor.   
     
     
         2 . The fuel cell system of  claim 1 , wherein the start-up battery includes at least one of a low-voltage battery and a high-voltage battery. 
     
     
         3 . The fuel cell system of  claim 2 , wherein the high-voltage battery is a hybrid battery. 
     
     
         4 . The fuel cell system of  claim 1 , further comprising a voltage sensor configured to measure a voltage of the start-up battery. 
     
     
         5 . The fuel cell system of  claim 1 , further comprising a bypass valve disposed between the air compressor and the cathode inlet, the bypass valve configured to selectively bypass an air flow around the fuel cell stack to an exhaust. 
     
     
         6 . The fuel cell system of  claim 1 , further comprising a regulator valve disposed between the hydrogen source and the fuel cell stack, the regulator valve configured to selectively supply an anode purge to the fuel cell stack. 
     
     
         7 . The fuel cell system of  claim 1 , further comprising at least one speed sensor configured to measure a rotational speed of the air compressor. 
     
     
         8 . The fuel cell system of  claim 1 , wherein the controller is configured to schedule an anode purge based on the available electrical energy in the start-up battery. 
     
     
         9 . A fuel cell system comprising:
 a fuel cell stack including a plurality of fuel cells and having an anode inlet and 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, wherein a flow of air bypasses the fuel cell stack and is provided to the exhaust by the compressor;   a hydrogen source in fluid communication with the anode inlet;   a start-up battery in electrical communication with the air compressor, wherein the start-up battery has an operating voltage less than a fuel cell stack operating voltage;   a power conversion module in electrical communication with the start-up battery and the air compressor, the power conversion module configured to selectively boost a voltage of the start-up battery supplied to the air compressor; and   a controller in electrical communication with the power conversion module configured to set an air compressor speed based on an electrical energy available at the compressor.   
     
     
         10 . The fuel cell system of  claim 9 , wherein the start-up battery includes at least one of a low-voltage battery and a high-voltage battery. 
     
     
         11 . The fuel cell system of  claim 10 , wherein the high-voltage battery is a hybrid battery. 
     
     
         12 . The fuel cell system of  claim 9 , further comprising a voltage sensor configured to measure a voltage of the start-up battery. 
     
     
         13 . The fuel cell system of  claim 9 , further comprising a bypass valve disposed between the air compressor and the cathode inlet, the bypass valve configured to selectively bypass an air flow around the fuel cell stack to an exhaust. 
     
     
         14 . The fuel cell system of  claim 9 , further comprising a regulator valve disposed between the hydrogen source and the fuel cell stack, the regulator valve configured to selectively supply an anode purge to the fuel cell stack. 
     
     
         15 . The fuel cell system of  claim 9 , further comprising at least one speed sensor configured to measure a rotational speed of the air compressor. 
     
     
         16 . The fuel cell system of  claim 15 , wherein the speed sensor measures an actual speed of the air compressor. 
     
     
         17 . The fuel cell system of  claim 16 , wherein an anode purge is scheduled when one of (a) the actual speed of the air compressor is greater than a desired speed, and (b) an air compressor ramp up time has elapsed, wherein the anode purge is scheduled by at least one of (i) setting a time for the anode purge, and (ii) setting a flow rate for the anode purge, wherein the flow rate for the anode purge is calculated from a look-up table based on the electrical energy available. 
     
     
         18 . The fuel cell system of  claim 9 , wherein the controller is configured to schedule an anode purge based on an electrical energy available in the start-up battery. 
     
     
         19 . The fuel cell system of  claim 18 , wherein the controller is further configured to divert the flow of air from the exhaust to the cathode inlet upon completion of the anode purge. 
     
     
         20 . The fuel cell system of  claim 9 , wherein no flow of air is provided to the fuel cell stack during an anode purge.