Systems and methods to determine cathode inlet pressure limits in a fuel cell system
System and methods for setting pressure limits for an air supply of a fuel cell (“FC”) system are presented. Certain embodiments disclosed herein may allow a FC system to calculate a minimum and a maximum FC stack cathode inlet pressure based on different operating conditions while ensuring that the FC stack receives a desired air flow. Further embodiments disclosed herein may allow a FC system to maintain a cathode inlet air pressure within a range that protects an associated compressor from entering surge and/or overheating conditions.
1. A system comprising:
a fuel cell (FC) system comprising a FC stack;
an air circulation system configured to circulate air through one or more locations of the FC system, the air circulation system comprising a FC compressor system;
a FC controller system programmed to:
determine a compressor pressure ratio setpoint of the FC compressor system; determine a predicted compressor inlet pressure of the FC compressor system; determine a predicted pressure drop from an outlet of the FC compressor system
to an inlet of the FC system;
calculate a first stack pressure setpoint of the FC via a mathematical expression using the compressor pressure ratio setpoint, the predicted compressor inlet pressure, and the predicted pressure drop; and
adjust a first control parameter of the FC compressor system based on the calculated first stack pressure setpoint of the FC.
2. The system of claim 1 , wherein the first stack pressure setpoint of the FC comprises a maximum stack pressure setpoint of the FC.
3. The system of claim 1 , wherein the mathematical expression includes subtracting the predicted pressure drop from a product of the compressor ratio setpoint and the predicted compressor inlet pressure.
4. The system of claim 1 , wherein the FC controller system is further programmed to:
determine that a cathode backpressure valve is open at a desired stack flow;
determine a predicted cathode exhaust inlet pressure;
determine a predicted cathode backpressure valve inlet based on the predicted cathode exhaust inlet pressure;
calculate a second stack pressure setpoint of the FC using a pressure drop model; and
adjust a second control parameter of a FC compressor system based on the calculated second stack pressure setpoint of the FC.
5. The system of claim 4 , wherein the calculated second stack pressure setpoint of the FC comprises a minimum stack pressure setpoint of the FC.
6. The system of claim 4 , wherein the FC controller system is further programmed to prevent the cathode backpressure valve from closing and thereby maintain operation of the FC compressor system outside of compressor surge and facilitate direct correspondence of the adjusted first and second control parameters to respective commanded values of the first and second control parameters by setting stack pressure setpoints between the first and second stack pressure setpoints.