Temperature control method for vehicular proton exchange membrane fuel cell system

1. A temperature control method for a vehicular proton exchange membrane fuel cell system, comprising the following steps:

step S1: measuring a coolant inlet temperature of a cell stack;

step S2: evaluating a difference between a target coolant inlet temperature and an actually measured coolant inlet temperature to obtain a temperature deviation value;

step S3: inputting the temperature deviation value and the actually measured coolant inlet temperature into a proportional integral (PI) control module to obtain a control quantity of a cooling fan, wherein the control quantity comprises a rotation speed of the cooling fan, and the PI control module comprises a proportional integral PI module and a fuzzy logic module specifically as follows:

the proportional integral PI module is used for obtaining the rotation speed of the cooling fan by calculation, and the fuzzy logic module is used for adjusting PI parameters in real time according to the temperature deviation value and a variation quantity of the temperature deviation value, an input membership function of the fuzzy logic module is described by a triangular distribution, an output of the fuzzy logic module is a proportional parameter correction and an integral parameter correction, an output membership function is described by a Gaussian distribution, and a centroid method is adopted for the calculation of the output; and

step S4: inputting the control quantity of the cooling fan obtained in the step S3 into a cooling system controller through a control unit of a fuel cell system to achieve temperature control of the fuel cell system, wherein

in the step S3, in consideration of a large difference value between the target coolant inlet temperature and the actually measured coolant inlet temperature in an initial warming-up process, the following processing is specifically conducted:

introducing an integral separation method in the proportional integral PI module to separate an integral in the proportional integral PI module in the initial warming-up process, specifically as follows:

1) Setting a threshold value ε for controlling the temperature deviation value according to actual system control requirements;

2) when the target coolant inlet temperature is an initial warming-up temperature and the difference value between the target coolant inlet temperature and the actually measured coolant inlet temperature is greater than the threshold value ε, adopting a proportional control; and

3) In a target coolant inlet temperature reduction process, not starting the proportional integral PI module in the cooling process, maintaining a current opening degree of the cooling fan unchanged until the difference value between the actually measured coolant inlet temperature and the target coolant inlet temperature is less than a certain threshold value, and then starting the proportional integral PI module to adjust the rotation speed of the cooling fan in real time.

2. The temperature control method for the vehicular proton exchange membrane fuel cell system according to claim 1 , wherein,

in the step S3, the rotation speed is regulated in advance through the cooling fan under a working condition that a load current changes is greater than 10 A, the load current is regarded as disturbance to be used for a compensation calculation, and then a compensation calculation result is integrated with the output of the fuzzy logic module:

when a compensation action needs to be started, a disturbance-based feedforward compensation control expression is as follows:

u ( t ) fed =k c I

wherein k c is a feedforward control parameter;

a total opening degree output control expression of the cooling fan is as follows:

u=k c I +( k p_c +Δk p_FL ) e ( t )+( k i_c +Δk i_FL )∫ 0 t e ( t ) dt

3. The temperature control method for the vehicular proton exchange membrane fuel cell system according to claim 2 , wherein,

in the step S3, before inputting an obtained total opening degree output control value of the cooling fan into a controller of a cooling subsystem, a total opening degree control output quantity is limited, so that an upper control duty ratio of each cooling fan is 90%.

4. The temperature control method for the vehicular proton exchange membrane fuel cell system according to claim 1 , wherein,

the step S3 further comprises a step of distributing the cooling fans, so that the output duty ratio is averagely distributed, with specific principles as follows:

when a PI output duty ratio D is that D is equal to or greater than 0 and is less than 5%, no cooling fan is started;

when the PI output duty ratio is that D is equal to or greater than 5 and is less than 15%, the duty ratio of each cooling fan is 15%, and one cooling fan is started;

when the PI output duty ratio is that D is equal to or greater than 15% and is less than 30%, the duty ratio of each cooling fan is D, and one cooling fan is started;

when the PI output duty ratio is that D is equal to or greater than 30% and is less than 60%, the duty ratio of each cooling fan is D/2, and two cooling fans are started;

when the PI output duty ratio is that D is equal to or greater than 60% and is less than 90%, the duty ratio of each cooling fan is D/3, and three cooling fans are started;

when the PI output duty ratio is that D is equal to or greater than 90% and is less than 120%, the duty ratio of each cooling fan is D/4, and four cooling fans are started;

when the PI output duty ratio is that D is equal to or greater than 120% and is less than 150%, the duty ratio of each cooling fan is D/5, and five cooling fans are started;

when the PI output duty ratio is that D is equal to or greater than 150% and is less than 180%, the duty ratio of each cooling fan is D/6, and six cooling fans are started;

when the PI output duty ratio is that D is equal to or greater than 180% and is less than 210%, the duty ratio of each cooling fan is D/7, and seven cooling fans are started; and

when the PI output duty ratio is that D is equal to or greater than 210% and is less than 240%, the duty ratio of each cooling fan is D/8, and eight cooling fans are started.