Patent ID: 9306230
Filing Date: 2016-04-05
CPC Classification: H01M,Y02E

Claim Text:
1. A method for estimating a cathode inlet and cathode outlet relative humidity (RH) of a fuel cell stack based on a high frequency resistance (HFR) of the fuel cell stack, said method comprising: measuring inlet and outlet pressure of a cathode air flow passing through the fuel cell stack; measuring inlet and outlet coolant temperature of a coolant passing through the fuel cell stack; determining cathode stoichiometry based on measured stack current and measured cathode air flow; utilizing a model to estimate the HFR of the fuel cell stack, wherein the model uses the measured inlet and outlet pressure of the cathode air flow, the measured inlet and outlet coolant temperature of the coolant, and the cathode stoichiometry to estimate the HFR; measuring the HFR of the fuel cell stack using an HFR sensor; comparing the model estimation of the HFR of the fuel cell stack to the measured HFR from an HFR sensor; determining an error between the estimated model HFR and the HFR measured by the HFR sensor; minimizing the error between the estimated model HFR and the HFR measured, wherein minimizing the error includes minimizing a plant model mismatch; estimating the cathode outlet RH by solving a water specie balance; estimating an average stack HFR by integrating the model estimation of the HFR from cathode inlet to cathode outlet; and determining a cathode inlet RH and calculating a step size such that the resulting RH profile matches the measured HFR and the model average HFR after the error has been minimized.