Control systems and methods to meet fuel cell fuel demand

A method for meeting hydrogen gas demand in a fuel cell circuit of a vehicle under transient conditions, the method comprising:

• detecting, by a current sensor, a current flowing through a fuel cell stack;
• estimating, by an electronic control unit (ECU), a pressure of the hydrogen gas and pressures of non-hydrogen gases at an outlet of the fuel cell stack;
• determining, by the ECU, a current increase rate based on the detected current;
• determining, by the ECU, a target hydrogen gas stoic at an inlet of the fuel cell stack based on the detected current;
• and
• increasing, by at least one injector, the pressure of the hydrogen gas at the outlet based on the estimated pressures of the hydrogen gas and the non-hydrogen gases to meet the target hydrogen gas stoic when the current increase rate is above a predetermined threshold.

A method for meeting hydrogen gas demand in a fuel cell circuit of a vehicle, the method comprising:

• determining, by an electronic control unit (ECU), a target hydrogen gas recirculation stoic at an inlet of a fuel cell stack;
• estimating, by the ECU, a mole fraction of the hydrogen gas at an outlet of a liquid vapor separator, a pressure of the hydrogen gas, and pressures of non-hydrogen gases at an outlet of the fuel cell stack, the pressures of the hydrogen gas and the non-hydrogen gases defining a total system pressure;
• and
• increasing, by the ECU, a speed of a hydrogen pump based on the mole fraction of the hydrogen gas to meet the target hydrogen gas recirculation stoic while minimizing excess hydrogen gas purging to improve overall efficiency of the fuel cell circuit.