Analytic method of fuel consumption optimized hybrid concept for fuel cell systems

A method for optimizing a power output distribution between a fuel cell stack and a battery in a fuel cell system, said method comprising:

• identifying a desired power request;
• defining a virtual battery hydrogen power for the battery that is based on a relationship between a battery power request from the battery and an efficiency of the battery;
• defining a virtual stack hydrogen power for the fuel cell stack that is based on a relationship between a stack power request from the fuel cell stack and an efficiency of the fuel cell stack;
• converting the virtual battery hydrogen power to a battery polynomial equation;
• converting the virtual stack hydrogen power to a stack polynomial equation;
• adding the battery polynomial equation and the stack polynomial equation to obtain a combined power polynomial equation;
• solving the combined power polynomial equation to determine a minimum of the stack power request and the battery power request;
• and
• adding a compressor acceleration power signal for controlling a cathode compressor to the desired power request if a stack power at a current time step is greater than a stack power at a previous time step.

An optimization system for optimizing a power output distribution between a fuel cell stack and a battery in a fuel cell system, said optimization system comprising:

• a controller programmed to provide:
• means for identifying a desired power request;
• means for defining a virtual battery hydrogen power for the battery that is based on a relationship between a battery power request from the battery and an efficiency of the battery;
• means for defining a virtual stack hydrogen power for the fuel cell stack that is based on a relationship between a stack power request from the fuel cell stack and an efficiency of the fuel cell stack;
• means for converting the virtual battery hydrogen power to a battery polynomial equation;
• means for converting the virtual stack hydrogen power to a stack polynomial equation;
• means for adding the battery polynomial equation and the stack polynomial equation to obtain a combined power polynomial equation;
• means for solving the combined power polynomial equation to determine a minimum of the fuel cell stack power request by setting derivative of the virtual stack hydrogen power to zero;
• and means for subtracting the stack power request from the desired power request to obtain the battery power request;
• and
• means for adding a compressor acceleration power signal for controlling a cathode compressor to the desired power request if a stack power at a current time step is greater than a stack power at a previous time step.