Method for generating injection current for fuel cell stack and apparatus for performing the same

1. An apparatus for generating injection current for a fuel cell stack, comprising:

a switch configured to retain any one state of an on state and an off state;

an inductor configured to output accumulated energy according to a state of the switch as a boost voltage and a signal current, wherein the signal current is applied to the fuel cell stack so as to diagnose a fault of the fuel cell stack; and

a converter configured to provide the boost voltage received from the inductor to a load or convert the boost voltage into a predetermined voltage and provide the predetermined voltage to a load; and

a control unit configured to receive the signal current and calculate total harmonic distortion (THD) and impedance of the fuel cell stack,

wherein the switch generates an alternating current component in the signal current which is applied to the fuel cell stack, while the state of the switch is controlled to be changed by the unit of a predetermined time according to a frequency to be used, and

wherein the control unit calculates the THD through a frequency analysis corresponding to the frequency to be used, and determines the fault of the fuel cell stack when the THD is equal to or more than a predetermined harmonic distortion.

2. The apparatus according to claim 1 , wherein the inductor accumulates energy at both ends thereof when the state of the switch retains the on state, and outputs the accumulated energy as the boost voltage when e state of the switch is changed from the on state to the off state.

3. The apparatus according to claim 1 ,

wherein the control unit is configured to calculate current of the fuel cell stack by using the signal current, and calculate the impedance of the fuel cell stack by using the current of the fuel cell stack and a voltage of the fuel cell stack.

4. The apparatus according to claim 3 , wherein the control unit calculates a current of the fuel cell stack corresponding to a predetermined frequency by frequency-analyzing the signal current.

5. The apparatus according to claim 3 , wherein the control unit calculates a voltage of the fuel cell stack corresponding to a predetermined frequency by frequency-analyzing the voltage of the fuel cell stack.

6. The apparatus according to claim 5 , wherein the control unit calculates a voltage of the fuel cell stack corresponding to any one frequency of 300 Hz and 10 Hz.

7. The apparatus according to claim 1 , wherein the state of the switch is controlled by a pulse width modulation (PWM) signal of the control unit to be changed with the unit of the predetermined time according to the frequency to be used.

8. A method for generating injection current for a fuel cell stack, performed in an apparatus for generating injection current for the fuel cell stack, the method comprising:

accumulating energy in an inductor when a state of a switch retains an on state;

outputting, by the inductor, accumulated energy as a signal current which is applied to the fuel cell stack to diagnose a fault of the fuel cell stack and a boost voltage when the state of the switch is changed from the on state to an off state;

providing the boost voltage to a load or converting the boost voltage into a predetermined voltage and providing the predetermined voltage to a load, by a converter to which the boost voltage is supplied; and

calculating, by a control unit, total harmonic distortion (THD) and impedance of the fuel cell stack,

wherein the switch generates an alternating current component in the signal current which is applied to the fuel cell stack, while a state of the switch is controlled by the control unit to be changed by the unit of a predetermined time according to a frequency to be used,

wherein the calculating of the total harmonic distortion (THD) and the impedance of the fuel cell stack comprises:

calculating, by the control unit, THD through a frequency analysis corresponding to the frequency to be used; and

determining, by the control unit, the fault of the fuel cell stack when the THD is equal to or more than a predetermined harmonic distortion.

9. The method according to claim 8 , wherein the total harmonic distortion (THD) and impedance of the fuel cell stack comprises:

calculating, by the control unit, current of the fuel cell stack by using the signal current; and

calculating, by the control unit, the impedance of the fuel cell stack by using the current of the fuel cell stack and a voltage of the fuel cell stack.

10. The method according to claim 9 , wherein the calculating of the current of the fuel cell stack comprises:

calculating, by the control unit, the current of the fuel cell stack corresponding to a predetermined frequency by frequency-analyzing the signal current.

11. The method according to claim 9 , wherein the calculating of the impedance of the fuel cell stack comprises:

calculating, by the control unit, a voltage of the fuel cell stack corresponding to a predetermined frequency by frequency-analyzing the voltage of the fuel cell stack.

12. The method according to claim 11 , wherein the calculating of the voltage of the fuel cell stack corresponding to the predetermined frequency calculates a voltage of the fuel cell stack corresponding to any one frequency of 300 Hz and 10 Hz.

13. The method according to claim 8 , wherein the state of the switch is controlled by a PWM signal of the control unit to be changed with the unit of the predetermined time according to the frequency to be used.