Temperature control system and method for fuel cell system and fuel cell system
Temperature control system and method for a fuel cell system are disclosed. The temperature control system includes a state detector, a control selector, a normal controller and an internal model controller. The state detector determines whether the fuel cell system is in a leakage condition based on a dynamic transfer function from an air flowrate provided to the fuel cell system to a fuel cell temperature. The control selector selects to switch between the normal controller and the internal model controller based on a determined result. The normal controller is configured for controlling an air flowrate of the fuel cell system which is not in the leakage condition. The internal model controller is configured for controlling the air flowrate of the fuel cell system in the leakage condition to control the fuel cell temperature. A fuel cell system with the temperature control system is also disclosed.
1. A temperature control system for a fuel cell system comprising:
a state detector for determining whether the fuel cell system is in a leakage condition based on a dynamic transfer function from an air flowrate provided to the fuel cell system to a fuel cell temperature of the fuel cell system;
a control selector for selecting to switch between a normal controller and an internal model controller based on a determined result;
the normal controller for controlling an air flowrate of the fuel cell system which is not in the leakage condition to control the fuel cell temperature; and
the internal model controller for controlling the air flowrate of the fuel cell system in the leakage condition to control the fuel cell temperature.
2. The temperature control system of claim 1 , wherein the dynamic transfer function is expressed as follows:
f
t
(
s
)
=
-
Ks
+
1
(
t
1
s
+
1
)
(
t
2
s
+
1
)
wherein f t represents the dynamic transfer function, s represents the Laplacian operator, K represents a coefficient and is associated with the air flowrate and the fuel cell temperature, and t 1 and t 2 represent time constants.
3. The temperature control system of claim 2 , wherein when the coefficient K is larger than zero, the state detector determines an inverse response indicating cross leakage occurs to the fuel cell system and determines the fuel cell system is in the leakage condition, and when the coefficient K is equal to zero or less than zero, the state detector determines no inverse response occurs and determines the fuel cell system is in a normal condition.
4. The temperature control system of claim 3 , wherein the internal model controller comprises a compensator for compensating the inverse response of the fuel cell system to increase stability of the fuel cell system.
5. The temperature control system of claim 4 , wherein the compensator has the following compensation function:
f
c
(
s
)
=
λ
s
(
t
1
s
+
1
)
(
t
2
s
+
1
)
wherein f c represents the compensation function, and λ represents a compensation coefficient.
6. The temperature control system of claim 5 , wherein the compensator is a Smith predictor compensator and the compensation coefficient λ=2K.
7. The temperature control system of claim 4 , wherein the internal model controller comprises a PID controller and a gain of the PID controller is adaptable based on the dynamic transfer function, an output of the PID controller being fed back to an input of the compensator and an output of the compensator being fed forward to an input of the PID controller.
8. The temperature control system of claim 7 , wherein the normal controller comprises a PID controller, the PID controller of the normal controller having a smaller gain than the PID controller of the internal model controller.
9. The temperature control system of claim 7 , wherein the internal model controller further comprises a feedforward controller for receiving a feedforward signal from at least one of a power output, a fuel flowrate and a recycle ratio of the fuel cell system, and generating an air flowrate compensation based on the feedforward signal, the air flowrate compensation being added to the output of the PID controller.
10. The temperature control system of claim 1 , wherein the internal model controller further comprises a rate limiter for a fuel cell temperature setpoint.
11. The temperature control system of claim 1 , further comprising:
a bump-less transfer unit for ensuring no bump in an air flowrate command generated during switching between the normal controller and the internal model controller.
12. The temperature control system of claim 1 , wherein the fuel cell temperature comprises a temperature at an anode outlet of a fuel cell stack in the fuel cell system, a temperature of a fuel cell surface in the fuel cell system, a temperature of a bottom or top plate of the fuel cell stack, and a temperature in an anode gas passage of the fuel cell stack.
13. A temperature control method for a fuel cell system, comprising:
determining whether the fuel cell system is in a leakage condition based on a dynamic transfer function from an air flowrate provided to the fuel cell system to a fuel cell temperature of the fuel cell system;
selecting to switch between a normal controller and an internal model controller based on a determined result;
controlling, by the internal model controller, an air flowrate of the fuel cell system to control the fuel cell temperature when the fuel cell system is in the leakage condition; and
controlling, by the normal controller, the air flowrate of the fuel cell system to control the fuel cell temperature when the fuel cell system is not in the leakage condition.
14. The temperature control method of claim 13 , further comprising:
receiving an air flowrate feedback and a fuel cell temperature feedback of the fuel cell system; and
generating the dynamic transfer function based on the air flowrate feedback and the fuel cell temperature feedback, wherein the dynamic transfer function is expressed as follows:
f
t
(
s
)
=
-
Ks
+
1
(
t
1
s
+
1
)
(
t
2
s
+
1
)
wherein f t represents the dynamic transfer function, s represents the Laplacian operator, K represents a coefficient and is associated with the air flowrate and the fuel cell temperature, and t 1 and t 2 represent time constants.
15. The temperature control method of claim 14 , wherein determining whether the fuel cell system is in the leakage condition based on the dynamic transfer function comprises:
determining an inverse response indicating cross leakage occurs to the fuel cell system when the coefficient K is larger than zero and determining the fuel cell system is in the leakage condition; and
determining no inverse response occurs when the coefficient K is equal to zero or less than zero and determines the fuel cell system is in a normal condition.
16. The temperature control method of claim 13 , wherein the internal model controller comprises a PID controller and a compensator, controlling the air flowrate by the internal model controller comprising:
compensating, by the compensator, an output of the PID controller to generate a temperature compensation;
adding the temperature compensation to a fuel cell temperature feedback of the fuel cell system;
generating an air flowrate command of the fuel cell system based on an added fuel cell temperature feedback and a fuel cell temperature setpoint; and
controlling an air blower of the fuel cell system based on the air flowrate command.
17. The temperature control method of claim 16 , further comprising:
receiving a feedforward signal from at least one of a power output, a fuel flowrate and a recycle ratio of the fuel cell system;
generating an air flowrate compensation based on the feedforward signal; and
adding the air flowrate compensation to the output of the PID controller.
18. The temperature control method of claim 16 , further comprising:
performing a rate limiting for the fuel cell temperature setpoint, wherein the air flowrate command is generated based on the added fuel cell temperature feedback and a rate-limited fuel cell temperature setpoint.
19. The temperature control method of claim 16 , wherein compensating the output of the PID controller comprises:
multiplying the output of the PID controller by a compensation function of the compensator to generate the temperature compensation, wherein the compensation function is expressed as follows:
f
c
(
s
)
=
λ
s
(
t
1
s
+
1
)
(
t
2
s
+
1
)
wherein f c represents the compensation function, and λ represents a compensation coefficient.
20. The temperature control method of claim 13 , further comprising:
performing bump-less transfer between the normal controller and the internal model controller.
21. A fuel cell system comprising:
a fuel cell stack for generating power and having an anode and a cathode;
a fuel regulator for regulating a fuel flowrate of a fuel provided to the anode;
an air blower for regulating an air flowrate of air provided to the cathode;
an air flowmeter for measuring the air flowrate;
a temperature sensor for measuring a fuel cell temperature; and
the temperature control system as claimed in claim 1 .
22. The fuel cell system of claim 21 , further comprising:
a fuel reformer for receiving the fuel and a tail gas from an anode outlet of the anode and generating a reformate, wherein at least one portion of the reformate is returned to an anode inlet of the anode.