System and method for estimating hydrogen concentration of fuel cell

1 . A system for estimating a hydrogen concentration of a fuel cell, the system comprising:

the fuel cell;

a discharge line connected to an outlet side of a fuel cell hydrogen electrode while connecting the fuel cell to an exterior of the fuel cell, for communication between the fuel cell and the exterior of the fuel cell;

a discharge valve provided at the discharge line and configured to adjust the communication between the fuel cell and the exterior of the fuel cell; and

a controller configured to estimate a gas discharge amount of gas discharged through the discharge line, to cut off the discharge valve after estimation of the gas discharge amount, to check occurrence of degradation of the fuel cell, and to correct a crossover coefficient value of the fuel cell in accordance with a level of the degradation in the fuel cell when the degradation of the fuel cell has occurred, estimating the hydrogen concentration in an interior of the fuel cell,

wherein the controller is configured to determine a reduction amount reduced from the estimated gas discharge amount for a reference time after cut-off of the discharge valve, and then to determine whether or not the degradation of the fuel cell has occurred, based on the determined reduction amount, and

wherein the controller is configured to determine a difference between the reduction amount of the gas discharge amount and a reference reduction amount of the gas discharge amount as a reduction variation amount, and then to conclude that the degradation has occurred in the fuel cell, when the determined reduction variation amount is greater than the reference reduction variation amount.

2 . The system of claim 1 , further including:

a hydrogen supply line connected to the fuel cell hydrogen electrode and configured to supply hydrogen to the fuel cell; and

a pressure sensor provided at the hydrogen supply line and configured to measure a pressure of the hydrogen supply line,

wherein the controller is configured to determine a hydrogen supply amount based on the pressure measured through the pressure sensor, and to estimate the gas discharge amount in a state of reflecting the determined hydrogen supply amount.

3 . The system of claim 1 , wherein the reference reduction amount of the gas discharge amount is a reduction amount of the gas discharge amount for the reference time in an initial state in which the fuel cell is not aged.

4 . The system of claim 1 , wherein the reference reduction variation amount is a minimum value of the reduction variation amount of the gas discharge amount when the degradation occurs in the fuel cell.

5 . The system of claim 1 , wherein the controller is configured to derive a degradation rate of the fuel cell based on the reduction variation amount determined when the degradation has occurred in the fuel cell, checking a degradation level of the fuel cell.

6 . The system of claim 5 , wherein the controller is provided with a data map using, as an input thereof, the reduction variation amount of the gas discharge amount, and as an output thereof, the degradation rate of the fuel cell according to the reduction variation amount of the gas discharge amount.

7 . The system of claim 5 , wherein the controller is configured to correct the crossover coefficient value of the fuel cell based on the derived degradation rate of the fuel cell, and to estimate the hydrogen concentration of the fuel cell hydrogen electrode in the interior of the fuel cell based on the corrected crossover coefficient value.

8 . The system of claim 7 , wherein, in the estimating the hydrogen concentration in the interior of the fuel cell, the controller is configured to determine a diffusion coefficient caused by crossover of the fuel cell, using the corrected crossover coefficient value, and then to estimate the hydrogen concentration of the fuel cell hydrogen electrode in the interior of the fuel cell, based on the determined diffusion coefficient.

9 . A method for estimating a hydrogen concentration of a fuel cell, the method comprising:

estimating, by a controller, a gas discharge amount discharged through a discharge line during operation of the fuel cell;

cutting off, by the controller, a discharge valve after estimation of the gas discharge amount, and then checking, by the controller, occurrence of degradation of the fuel cell;

correcting, by the controller, a crossover coefficient value of the fuel cell when the degradation of the fuel cell has occurred; and

estimating, by the controller, the hydrogen concentration in an interior of the fuel cell, based on the corrected crossover coefficient value,

wherein, in the checking occurrence of degradation of the fuel cell, the controller is configured to determine a reduction amount reduced from the estimated gas discharge amount for a reference time after cut-off of the discharge valve, and then to determine a difference between the reduction amount of the gas discharge amount and a reference reduction amount of the gas discharge amount, as a reduction variation amount, and

wherein, in the checking occurrence of degradation of the fuel cell, the controller is configured to compare the reduction variation amount of the gas discharge amount with a reference reduction variation amount, and to conclude that degradation of the fuel cell has occurred, when the reduction variation amount of the gas discharge amount is greater than the reference reduction variation amount.

10 . The method of claim 9 , wherein, in the estimating the gas discharge amount, the controller is configured to determine a hydrogen supply amount based on a pressure measured by a pressure sensor, and to estimate the gas discharge amount in a state of reflecting the determined hydrogen supply amount.

11 . The method of claim 9 , wherein the reference reduction amount of the gas discharge amount is a reduction amount of the gas discharge amount for the reference time in an initial state in which the fuel cell is not aged.

12 . The method of claim 11 , wherein the reference reduction variation amount is a minimum value of the reduction variation amount of the gas discharge amount when the degradation occurs in the fuel cell.

13 . The method of claim 9 , wherein, in the correcting the crossover coefficient value of the fuel cell, the controller is configured to derive a degradation rate of the fuel cell based on the reduction variation amount of the gas discharge amount, when the degradation of the fuel cell has occurred, and then to correct the crossover coefficient value of the fuel cell based on the derived degradation rate of the fuel cell.

14 . The method of claim 9 , wherein, in the estimating the hydrogen concentration in the interior of the fuel cell, the controller is configured to determine a diffusion coefficient caused by crossover of the fuel cell, using the corrected crossover coefficient value, and then to estimate the hydrogen concentration in the interior of the fuel cell, based on the determined diffusion coefficient.