CN115224303B - Fuel cell circulation cooling device and temperature balance control method - Google Patents
Fuel cell circulation cooling device and temperature balance control method Download PDFInfo
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- 239000000446 fuel Substances 0.000 title claims abstract description 162
- 238000001816 cooling Methods 0.000 title claims abstract description 33
- 238000000034 method Methods 0.000 title claims abstract description 14
- 239000000110 cooling liquid Substances 0.000 claims abstract description 78
- 230000007246 mechanism Effects 0.000 claims abstract description 11
- 230000017525 heat dissipation Effects 0.000 claims abstract description 8
- 238000012512 characterization method Methods 0.000 claims description 8
- 230000002441 reversible effect Effects 0.000 description 15
- 239000001257 hydrogen Substances 0.000 description 14
- 229910052739 hydrogen Inorganic materials 0.000 description 14
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 12
- 238000010586 diagram Methods 0.000 description 6
- 239000007800 oxidant agent Substances 0.000 description 6
- 230000001590 oxidative effect Effects 0.000 description 5
- 239000002826 coolant Substances 0.000 description 4
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- 238000002347 injection Methods 0.000 description 2
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- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
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- H01M8/00—Fuel cells; Manufacture thereof
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- H01M8/04029—Heat exchange using liquids
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- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
- H01M8/04067—Heat exchange or temperature measuring elements, thermal insulation, e.g. heat pipes, heat pumps, fins
- H01M8/04074—Heat exchange unit structures specially adapted for fuel cell
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- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
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- H01M8/04358—Temperature; Ambient temperature of the coolant
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- H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
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Abstract
The invention particularly relates to a fuel cell circulating cooling device and a temperature balance control method. The method comprises dividing temperature equalization control modes according to the difference between the calculated stack temperature and the preset stack temperature, the difference between the cooling liquid inlet and outlet stack temperature, the calculated difference between the fuel cell stack and the variance of the voltage values of all the single cells of the stack, selecting a proper mode for the fuel cell stack meeting the heat dissipation requirement, controlling a cooling liquid circulation reversing mechanism to drive the cooling liquid to flow unidirectionally or reversely, and controlling a radiator assembly fan to work in a proper speed interval. The temperature uniformity of the fuel cell system is controlled by the invention.
Description
Technical Field
The invention relates to the technical field of large-area fuel cell thermal management for traffic power systems, in particular to a fuel cell circulating cooling device and a temperature balance control method.
Background
Fuel cells, which are essentially electrochemical devices that produce electrical energy through an electrochemical reaction (non-combustion) using hydrogen and oxygen as fuels, are receiving increasing attention worldwide due to their non-polluting emissions. Commercialization of fuel cells still faces many problems including excessive cost, too low life, and poor durability. As fuel cells tend to have larger active areas, the maldistribution of components within the fuel cell leads to further expansion of the in-plane variability of the fuel cell, and as the number of fuel cell sheets increases, the uniformity of the fuel cell system is also affected, ultimately leading to reduced durability and life of the fuel cell.
From a thermodynamic perspective, the self-generated heat of a fuel cell increases significantly with increasing current density, with an efficiency of only about 50% at the rated power point, with the remaining energy being largely variable to heat, which results in a temperature build-up inside the fuel cell and maldistribution. The temperature distribution unevenness is mainly expressed in two aspects: firstly, the in-plane distribution is uneven, and the uneven distribution of the in-plane fuel can cause different reaction intensity due to factors such as air flow distribution and the like, so as to cause the difference of temperature distribution; second, since the fuel cell system has several cells connected in series and heat is carried out by the cooling system, this means that the temperature along the flow path may show a stepwise change. The variation and difference in temperature can significantly affect the performance and uniformity of the fuel cell itself, and the uniformity of the temperature distribution of the fuel cell needs to be emphasized.
The existing fuel cell thermal management only adopts a unidirectional cooling mode, which leads to that the temperature at the water outlet of the fuel cell is obviously higher than the temperature at the water inlet, and the temperature gradient is obviously improved along with the rise of the current density.
The existing large-area fuel cells mostly adopt a mode of single-chip one-check or even multi-chip one-check, and because the internal state coupling of the fuel cells is changeable, the internal state of the fuel cells is difficult to effectively evaluate by means of single variable measurement, and the fuel cells are not suitable for being applied to the large-area fuel cells.
Disclosure of Invention
The invention aims to solve the technical problems, and provides a fuel cell circulating cooling device and a temperature balance control method, which aim to improve the temperature distribution uniformity of a fuel cell and ensure the consistency and the service life of the fuel cell on the premise of evaluating the state of the fuel cell.
The invention provides a fuel cell circulation cooling device which comprises a radiator assembly, a switch valve, a temperature sensor, a pressure sensor and a cooling liquid circulation reversing mechanism, wherein the radiator assembly is communicated with a fuel cell stack through two pipelines, the switch valve is used for controlling whether cooling liquid enters the radiator assembly, the temperature sensor and the pressure sensor are used for collecting the temperature and the pressure of a cooling liquid inlet and outlet of the fuel cell stack, and the cooling liquid circulation reversing mechanism is connected to the pipeline communicated with the radiator assembly and used for providing power for the flow of the cooling liquid and switching the flow direction of the cooling liquid.
Preferably, the cooling liquid circulation reversing mechanism adopts a reversible pump, and the reversible pump is arranged on a pipeline for communicating the fuel cell stack with the radiator assembly.
Preferably, the cooling liquid circulation reversing mechanism comprises a one-way pump, four reversing valves, a first branch and a second branch, wherein the first branch and the second branch are respectively provided with one reversing valve, and the first branch and the second branch are connected to two pipelines which are communicated with the fuel cell stack and the radiator assembly in a crossing manner; the one-way pump and the reversing valve are arranged on a pipeline for communicating the fuel cell stack with the radiator assembly; a reversing valve is disposed in the other line of the fuel cell stack that communicates with the radiator assembly.
Preferably, the fuel cell stack radiator further comprises a water tank, wherein the water tank is connected to one pipeline which is communicated with the radiator assembly through a pipeline.
Preferably, the fuel cell stack radiator further comprises a water tank, wherein the water tank is connected to one pipeline which is communicated with the radiator assembly through a pipeline.
The invention also provides a temperature balance control method adopting the fuel cell circulation cooling device, which comprises the following steps: collecting the cooling liquid inlet and outlet temperatures of a fuel cell stack, collecting the voltages at the four positions of a cathode inlet, a cathode outlet, an anode inlet and an anode outlet of each single cell of the fuel cell stack, calculating the temperature difference of the cooling liquid inlet and outlet of the stack and the temperature of the stack through a fuel cell controller, calculating the pressure difference of the fuel cell stack and the variance of the voltage values at the four positions of all single cells of the stack, judging whether the fuel cell stack meets the heat dissipation requirement according to the calculated temperature difference of the cooling liquid inlet and outlet of the stack and the working temperature range of the fuel cell, dividing the temperature balance control mode according to the calculated temperature difference of the stack and the preset temperature difference of the cooling liquid inlet and outlet of the stack and the calculated pressure difference of the fuel cell stack and the variance of the voltage values at the four positions of all single cells of the stack, selecting a proper temperature balance control mode for the fuel cell stack which meets the heat dissipation requirement, controlling a cooling liquid circulation reversing mechanism of a fuel cell circulation cooling device to drive cooling liquid to flow or reversing flow, and controlling a radiator assembly fan to work in a proper speed range.
Preferably, the stack temperature is represented by an average value of the coolant in-and-out stack temperatures.
Preferably, the differential pressure DeltaV of the fuel cell stack is calculated by formula (1),
ΔV＝max(V 1 ,V 2 ,V 3 ,…,V n )-min(V 1 ,V 2 ,V 3 ,…,V n ) (1)
where n is the total number of single cells in the fuel cell stack, V 1 ,V 2 ,V 3 ,…,V n For each single cell calculated characterization voltage.
Preferably, the characterization voltage of the single cell is calculated by formula (2):
wherein the anode inlet voltage of the ith single cell of the fuel cell stack is V i1 Anode outlet voltage of V i2 The cathode inlet voltage is V i3 The cathode outlet voltage is V i4 I=1, 2, …, n, n is the total number of cells in the fuel cell stack, k 1 ＝1.5，k 2 ＝0.5，k 3 ＝1.5，k 4 ＝0.5。
Preferably, the variance of the four-position voltage values of all the unit cells of the stack is calculated by formula (3),
wherein ,
is the average value of the characterization voltages of all the single cells of the fuel cell stack.
Preferably, the temperature equalization control mode is set to three modes, and the first mode satisfies the condition: T-T0 is less than or equal to D1, T1-T2 is less than or equal to D2, deltaV is less than or equal to D3, and SigmaV is less than or equal to D4;
the second mode is that the condition D1 < |T-T0|is less than or equal to E1, D2 < |T 1-T2|is less than or equal to E2, D3 delta V is less than or equal to E3, and D4 delta V is less than or equal to E4;
the third mode is that the condition E1 < |T-T0|is less than or equal to F1, E2 < |T 1-T2|is less than or equal to F2, E3 < DeltaV is less than or equal to F3, E4 < Sigma V is less than or equal to F4;
wherein T is the temperature of the electric pile, T0 is the preset electric pile temperature, T1 is the temperature of the cooling liquid inlet pile, T2 is the temperature of the cooling liquid outlet pile, deltaV is the pressure difference of the electric pile of the fuel cell, and DeltaV is the variance of the voltage values of all the single cells of the electric pile at four positions.
The beneficial effects of the invention are as follows:
the invention provides two structural schemes of a reversible pump and a variable flow channel structure, and the flow direction of cooling liquid is timely adjusted by utilizing the reversible pump or a reversing valve according to the temperature field change of the fuel cell stack, so that the distribution uniformity of the temperature of a water inlet and a water outlet of the fuel cell stack can be ensured, and the device has the characteristics of high flexibility, good heat dissipation effect and strong adaptability;
the invention provides a new fuel cell state evaluation method, which is used for judging the internal state of a fuel cell stack based on multi-point voltage data, and taking the state as a temperature balance control strategy basis to formulate a plurality of working modes so as to control the flow direction of cooling liquid, the flow speed of the cooling liquid, the rotating speed of a radiator and the like in the fuel cell stack, thereby greatly improving the radiating efficiency of the fuel cell stack, improving the temperature uniformity and consistency of the fuel cell, improving the performance of the fuel cell and ensuring the service life of the fuel cell;
according to the invention, a fuzzy PID control theory is introduced, so that the control of the fuel cell circulation cooling device under the whole working condition is realized under the conditions that the heat production of the fuel cell stack is large and the temperature difference between the cooling liquid inlet and the cooling liquid outlet is overlarge, and the fuzzy PID algorithm is introduced under each working condition, so that the optimal heat management performance can be output under each working condition, the local control performance of the system can be met, the purpose of integral optimization can be achieved, and the temperature consistency of the fuel cell stack is improved.
Drawings
Fig. 1: a schematic structural diagram of a fuel cell circulation cooling device of the first embodiment,
fig. 2: a schematic structural diagram of a fuel cell circulation cooling device of the second embodiment,
fig. 3: the schematic diagram of the trend of the temperature difference in the single cell plane over time provided in the third embodiment,
fig. 4: the schematic diagram of the in-plane temperature distribution of the single cell provided in the third embodiment,
fig. 5: the temperature difference schematic diagram of the cooling liquid of the long pile, the short pile and the single cell of the electric pile provided in the third embodiment,
fig. 6: the multi-point voltage acquisition schematic diagram provided in the third embodiment.
The marks in the figure: the first pipe 1, the second pipe 2, the radiator assembly 3, the switching valve 4, the temperature sensor 5, the pressure sensor 6, the reversible pump 7, the water tank 8, the oxidizer supply system 9, the fuel supply system 10, the unidirectional pump 11, the first reversing valve 12, the second reversing valve 13, the third reversing valve 14, the fourth reversing valve 15, the first branch 16, the second branch 17, the air cleaner 91, the flow meter 92, the air compressor 93, the throttle valve 94, the air humidifier 95, the back pressure valve 96, the air in-out stack temperature sensor 97, the air in-out stack pressure sensor 98, the hydrogen storage bottle 101, the hydrogen injection valve 102, the hydrogen humidifier 103, the hydrogen discharge valve 104, the hydrogen in-out stack temperature sensor 105, the hydrogen in-out stack pressure sensor 106, and the fuel cell stack 100.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and all other embodiments obtained by those skilled in the art without making any inventive effort based on the embodiments of the present invention are within the scope of protection of the present invention.
In addition, directional words such as "upper", "lower", "left", "right", and the like, which are used in the following embodiments, are merely directions with reference to the drawings, and thus, the directional words used are intended to illustrate, not to limit, the invention.
Example 1
As shown in fig. 1, the fuel cell circulation cooling device provided in this embodiment includes a radiator assembly 3 that is communicated with a fuel cell stack 100 through a first pipeline 1 and a second pipeline 2, a switch valve 4 that controls whether cooling liquid enters the radiator assembly 3, a temperature sensor 5 and a pressure sensor 6 that collect the temperature and pressure of the cooling liquid of the fuel cell stack 100, and a cooling liquid circulation reversing mechanism, where the cooling liquid circulation reversing mechanism in this embodiment adopts a reversible pump 7, the reversible pump 7 can control the forward and reverse flow of the cooling liquid, the reversible pump 7 is disposed on the first pipeline 1 that communicates the fuel cell stack 100 with the radiator assembly 3, and the reversible pump 7 provides power for the flow of the cooling liquid and switches the flow direction of the cooling liquid. The fuel cell circulation cooling device of the present embodiment further includes a water tank 8, and the water tank 8 is connected to the second pipeline 2, which is communicated with the radiator assembly 3, of the fuel cell stack 100 through a pipeline.
The fuel cell circulation cooling device of the present embodiment further includes an oxidant supply system 9 and a fuel supply system 10, the oxidant supply system 9 includes an air filter 91, a flow meter 92, an air compressor 93, a throttle valve 94, an air humidifier 95, a back pressure valve 96 disposed at the oxidant outlet side of the fuel cell stack 100, an air inlet and outlet stack temperature sensor 97 for detecting the temperature and pressure of the fuel cell stack 100, and an air inlet and outlet stack pressure sensor 98, which are sequentially connected through pipelines at the oxidant inlet side of the fuel cell stack 100.
The fuel supply system 10 includes a hydrogen storage bottle 101, a hydrogen injection valve 102, a hydrogen humidifier 103, a hydrogen discharge valve 104 disposed at the fuel outlet side of the fuel cell stack 100, a hydrogen inlet/outlet stack temperature sensor 105 for detecting the temperature and pressure of the hydrogen in the fuel cell stack 100, and a hydrogen inlet/outlet stack pressure sensor 106, which are sequentially connected to the fuel inlet side of the fuel cell stack 100 via pipes.
Example two
As shown in fig. 2, the fuel cell circulation cooling device provided in this embodiment includes a radiator assembly 3 that is connected to a fuel cell stack 100 through a first pipeline 1 and a second pipeline 2, a switch valve 4 that controls whether cooling liquid enters the radiator assembly 3, a temperature sensor 5 and a pressure sensor 6 that collect the temperature and pressure of the cooling liquid of the fuel cell stack 100, and a cooling liquid circulation reversing mechanism that includes a unidirectional pump 11, four reversing valves (a first reversing valve 12, a second reversing valve 13, a third reversing valve 14, a fourth reversing valve 15), a first branch 16 and a second branch 17, where the first branch 16 and the second branch 17 are respectively provided with the first reversing valve 12 and the second reversing valve 13, and the first branch 16 and the second branch 17 are cross-connected to the first pipeline 1 and the second pipeline 2 that are connected to the fuel cell stack 100 and the radiator assembly 3; the one-way pump 11 and the third reversing valve 14 are arranged on a first pipeline 1 which is communicated with the radiator assembly 3 by the fuel cell stack 100; the fourth reversing valve 15 is disposed on the second pipe 2, which communicates with the radiator assembly 3, of the fuel cell stack 100. The fuel cell circulation cooling device of the present embodiment also includes a water tank 8, and the system structures of the oxidant supply system 9 and the fuel supply system 10 are the same as those of the first embodiment, and will not be described again.
Example III
The embodiment mainly aims at the problem of overlarge temperature difference between the cooling liquid inlet and the cooling liquid outlet of the fuel cell stack, and provides a temperature balance control method. As shown in fig. 3, which shows the temperature profile of a large-area fuel cell unit cell with time, it can be seen that the in-cell-plane variability further increases with time (current density increases). Fig. 4 shows the temperature distribution in the single cell plane of the large-area fuel cell, and it can be seen from the figure that the highest point of the temperature in the single cell plane is located at the cooling liquid inlet, and the lowest point is located at the cooling liquid outlet. Fig. 5 shows the variation curves of the temperature of the cooling liquid inlet and outlet of the long stack, the short stack and the single cell with the current density, and it can be seen that the difference of the cell temperature is further increased with the increase of the number of the cell sheets. The temperature equalization control method can remarkably improve the temperature distribution uniformity of the fuel cell stack.
The fuel cell stack is provided with a voltage inspection module for detecting the voltage of each single cell. All sensors and actuators in the fuel cell circulation cooling device of the first embodiment and the second embodiment are connected with a fuel cell controller, and a storage battery is connected with a reversing valve, a reverse pump or a one-way pump, a radiator assembly and the fuel cell controller through a power wire harness and supplies power for the reversing valve, the reverse pump or the one-way pump, the radiator assembly and the fuel cell controller; the fuel cell controller controls the reverse pump or the unidirectional pump, the radiator assembly and the reversing valve according to the information acquired by the temperature sensor and the voltage inspection module, and is used for controlling the overall temperature rise of the fuel cell stack and increasing the temperature consistency of the fuel cell stack.
The embodiment provides a temperature equalization control method adopting the fuel cell circulation cooling device, which comprises the following steps:
collecting the cooling liquid inlet and outlet temperatures of the fuel cell stack 100 through a temperature sensor 5, collecting the voltages (1-4 sampling positions shown in fig. 6) of the cathode inlet, the cathode outlet, the anode inlet and the anode outlet of each single cell of the fuel cell stack 100 through a voltage inspection module in the fuel cell stack 100, calculating the cooling liquid inlet and outlet stack temperature through a fuel cell controller, calculating the pressure difference of the fuel cell stack and the variance of the voltage values of the four positions of all the single cells of the stack, judging whether the fuel cell stack reaches the heat dissipation requirement according to the calculated cooling liquid inlet and outlet stack temperature difference and the working temperature range of the fuel cell, dividing the temperature balance control mode according to the calculated difference of the stack temperature and the preset stack temperature and the calculated pressure difference of the fuel cell stack and the variance of the voltage values of the four positions of all the single cells of the stack, and selecting a proper temperature balance control mode for the fuel cell controller to control the cooling liquid circulation mechanism to drive the cooling liquid or drive the cooling liquid to flow or control the cooling liquid to flow in a proper direction change mode in a reversing mode for the fuel cell controller to the cooling fan.
Specifically, the pile temperature is represented by an average value of the pile inlet and outlet temperatures of the cooling liquid, namely T= (T1+T2)/2, T1 is the pile inlet temperature of the cooling liquid, T2 is the pile outlet temperature of the cooling liquid, and |T1-T2| is used as the pile inlet and outlet temperature difference of the cooling liquid.
Specifically, the differential pressure and variance calculation process of the fuel cell stack is as follows:
detecting the voltage of four positions of each single cell through a voltage inspection module of the fuel cell stack, and defining the anode inlet voltage of the ith (i=1, 2, …, n) single cell of the fuel cell stack as V i1 Anode outlet voltage of V i2 The cathode inlet voltage is V i3 The cathode outlet voltage is V i4 The differential pressure of the four position voltages of each single cell is calculated by the formula (1):
ΔV i ＝max(V i1 ,V i2 ,V i3 ,V i4 )-min(V i1 ,V i2 ,V i3 ,V i4 ) (1)
the variance of the four position voltages of each single cell is calculated by the formula (2):
wherein ,
for the average of the four voltage positions of each single cell, i.e
To be used for
ΔV i ≤B，σV i C is less than or equal to C as single electricityReasonable difference sign in pool surface, wherein A, B and C are experimental calibration values which are 0.55,0.05,0.065 respectively. In the fuel cell stack, n single cells are counted, and the number m of the single cells with excessive in-plane difference is used as an evaluation index to represent the number of the cells with problems in the stack.
The characterization voltage of each single cell is calculated by equation (4),
wherein ,k1 ＝1.5，k 2 ＝0.5，k 3 ＝1.5，k 4 ＝0.5，i＝1,2,…,n。
Then the differential pressure DeltaV of the electric pile is calculated through a formula (5),
ΔV＝max(V 1 ,V 2 ,V 3 ,……,V n )-min(V 1 ,V 2 ,V 3 ,……,V n ) (5)
then calculating the variance sigma V of the voltage values at four positions of all single cells of the electric pile through a formula (6),
wherein ,
is the average value of the characterization voltages of all the single cells of the stack, as shown in formula (7),
then dividing a temperature equalization control mode according to the cooling liquid feeding temperature difference, a preset electric pile temperature value T0, an electric pile pressure difference delta V and variances sigma V of voltage values of four positions of all single cells of the electric pile:
the mode one state is noted when the following conditions are satisfied at the same time:
T-T0 is less than or equal to D1, T1-T2 is less than or equal to D2, deltaV is less than or equal to D3, and SigmaV is less than or equal to D4.
When the following conditions are satisfied at the same time, the mode is marked as a mode two state:
d1 is less than or equal to |T-T0| is less than or equal to E1, D2 is less than or equal to |T1-T2| is less than or equal to E2, D3 is less than or equal to DeltaV is less than or equal to E3, D4 is less than or equal to sigma V is less than or equal to E4.
When the following conditions are satisfied at the same time, the mode three state is marked:
e1 is less than or equal to |T-T0 is less than or equal to F1, E2 is less than or equal to |T1-T2 is less than or equal to F2, E3 is less than or equal to DeltaV is less than or equal to F3, E4 is less than or equal to sigma V is less than or equal to F4.
The values of the D1, D2, D3, D4, E1, E2, E3, E4, F1, F2, F3 and F4 are obtained through experiments, and the values of the parameters are actually calibrated according to NEDC working conditions and real vehicle test working conditions, so that the threshold value is determined. The approximate ranges of D1, E1, F1 are 0.5 ℃,1 ℃ and 1.5 ℃; the approximate ranges of D2, E2 and F2 are 4 ℃,6 ℃ and 8 ℃; d3, E3, F3 approximately ranges from 0.01, 0.025, 0.05; the approximate ranges of D4, E4, F4 are 0.005, 0.01, 0.015.
The working temperature range of the fuel cell stack is 70-80 ℃, the temperature difference between the cooling liquid inlet and the cooling liquid outlet is controlled within 10 ℃, and the heat dissipation requirement is met for the fuel cell stack exceeding the working temperature range and the temperature difference range between the cooling liquid inlet and the cooling liquid outlet.
In the mode, the temperature of the fuel cell stack is within the operating temperature range, and the fuel cell stack generates less self-generated heat, and a unidirectional flow cooling mode is adopted. For the fuel cell circulation cooling device of the first embodiment, the reversible pump adopts a unidirectional mode, and the cooling liquid flows forward; in the fuel cell circulation cooling device of the second embodiment, the first reversing valve 12 and the second reversing valve 13 are closed, the third reversing valve 14 and the fourth reversing valve 15 are opened, the coolant flows in the forward direction, and the radiator assembly fan operates in the interval of 20% or less.
In the second mode, the self-generated heat of the fuel cell stack is large, the temperature difference between the cooling liquid inlet and outlet of the stack is large, the direction of the cooling liquid needs to be switched at the moment, the direction of the cooling liquid is controlled by adopting fixed frequency, and the cooling liquid flows forward for 5 minutes and flows reversely for 3 minutes. For the fuel cell circulation cooling device of the first embodiment, the reversible pump switches the direction in the specified order; with the fuel cell circulation cooling device of the second embodiment, the first and second switching valves 12, 13 and the third and fourth switching valves 14, 15 are switched to open in the specified order, thereby controlling the direction of the coolant. The radiator assembly fan works in the interval below 75%.
In the third mode, the self-generated heat of the fuel cell stack is larger, the temperature difference of the cooling liquid entering and exiting the stack is larger, and the cooling liquid reversing and switching time are required to be controlled by adopting a fuzzy PID algorithm aiming at the existing working condition. With respect to the fuel cell circulation cooling device of the first embodiment, after receiving the switching instruction, the direction of the pump is switched; with the fuel cell circulation cooling device of the second embodiment, after receiving the switching command, the first reversing valve 12, the second reversing valve 13, the third reversing valve 14, and the fourth reversing valve 15 are switched and opened according to the command, thereby controlling the direction of the coolant. The radiator assembly fan works in a region below 95%.
The specific principle of the fuzzy PID algorithm is as follows:
the usual mathematical expression for a PID controller is shown as:
where u (t) is the calculated output control signal, e (t) is the error between the target value and the measured value, t is the run time, k, of the system p 、k i and kd Respectively proportional gain, integral gain and differential gain.
Therefore, the controller proposed in this embodiment is a derivative-free PI structure to ensure the stability of the closed-loop control system. Explicitly input variables: the cooling liquid inlet and outlet stack temperatures T1 and T2 and the consistency evaluation basis are DeltaV i 、
σV i The method comprises the steps of carrying out a first treatment on the surface of the Output variable: cooling fan rotation speed (real number domain). Then, a membership function is set to blur the input and output. Language tags for representing fuzzy sets are divided intoSeven fuzzy subsets: NB (much less than 0), NM (less than 0), NS (slightly less than 0), ZO (equal to 0), PS (slightly greater than 0), PM (greater than 0), PB (much greater than 0). The membership functions of errors and error variations are triangles, the fields of all variables are [ -6,6]And (3) inner part. Similarly, the output membership functions of proportional and integral gains are distributed by gaussian distribution, with the fields of all variables at [ -1,1]In, the result for calculation by the gravity center method is as follows:
where e is the error, Δe is the error variation, ω is the membership function, n is the number of single point sets, K pi and Kii Is the output of a single point, deltak p and Δki Is a deterministic output. Thus, the parameters of the PI controller can be obtained by:
k p_controller ＝k p +Δk p (11)
k i_controller ＝k i +Δk i (12)
wherein kp and ki Is the fixed gain, k, previously debugged p_controller and ki_controller Is the input to the PI controller.
The fuzzy rule is established according to the controlled object and working experience. The cooling fan control of the fuel cell system mainly effectively controls the temperature and performance of the battery. Fuzzy logic rules created based on the characteristics of the PI controller and the nonlinear hysteresis effect are shown in table 1.
TABLE 1
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (1)
1. A temperature equalization control method adopting a fuel cell circulation cooling device is characterized in that: collecting the cooling liquid inlet and outlet temperatures of a fuel cell stack, collecting the voltages at the four positions of a cathode inlet, a cathode outlet, an anode inlet and an anode outlet of each single cell of the fuel cell stack, calculating the temperature difference of the cooling liquid inlet and outlet of the stack and the temperature of the stack through a fuel cell controller, calculating the voltage difference of the fuel cell stack and the variance of the voltage values at the four positions of all single cells of the stack, judging whether the fuel cell stack meets the heat dissipation requirement according to the calculated temperature difference of the cooling liquid inlet and outlet of the stack and the working temperature range of the fuel cell, dividing a temperature balance control mode according to the calculated temperature difference of the stack and the preset temperature difference of the cooling liquid inlet and outlet of the stack and the calculated variance of the voltage values at the four positions of all single cells of the stack, selecting a proper temperature balance control mode for the fuel cell stack meeting the heat dissipation requirement, controlling a cooling liquid circulation reversing mechanism of a fuel cell circulation cooling device to drive cooling liquid to flow unidirectionally or reversely, and controlling a fan of a radiator assembly to work in a proper speed range; the pile temperature is represented by an average value of the pile inlet and outlet temperatures of the cooling liquid; the voltage difference Δv of the fuel cell stack is calculated by formula (1),
ΔV＝max(V 1 ，V 2 ，V 3 ，...，V n )-min(V 1 ，V 2 ，V 3 ，...，V n ) (1)
where n is the total number of single cells in the fuel cell stack, V 1 ，V 2 ，V 3 ，...，V n A characterization voltage for each single cell calculated;
the characterization voltage of the single cell is calculated by the formula (2):
wherein the anode inlet voltage of the ith single cell of the fuel cell stack is V i1 Anode outlet voltage of V i2 The cathode inlet voltage is V i3 The cathode outlet voltage is V i4 I=1, 2,..n, n is the total number of cells in the fuel cell stack, k 1 ＝1.5，k 2 ＝0.5，k 3 ＝1.5，k 4 ＝0.5；
The variance of the four-position voltage values of all the unit cells of the fuel cell stack is calculated by formula (3),
wherein ,
an average value of the characterization voltages of all the single cells of the fuel cell stack;
the temperature equalization control mode is set into three modes, and the first mode meets the condition: T-T0 is less than or equal to D1, T1-T2 is less than or equal to D2, deltaV is less than or equal to D3, and SigmaV is less than or equal to D4;
the second mode is that the condition D1 < |T-T0|is less than or equal to E1, D2 < |T 1-T2|is less than or equal to E2, D3 delta V is less than or equal to E3, and D4 delta V is less than or equal to E4;
the third mode is that the condition E1 < |T-T0|is less than or equal to F1, E2 < |T 1-T2|is less than or equal to F2, E3 < DeltaV is less than or equal to F3, E4 < Sigma V is less than or equal to F4;
wherein T is the temperature of the fuel cell stack, T0 is the preset stack temperature, T1 is the temperature of the cooling liquid entering the stack, T2 is the temperature of the cooling liquid exiting the stack, deltaV is the voltage difference of the fuel cell stack, and Sigma V is the variance of the voltage values of four positions of all single cells of the fuel cell stack;
in the mode, the temperature of the fuel cell stack is in the working temperature range, the self-generated heat of the fuel cell stack is less, and a unidirectional flow cooling mode is adopted at the moment;
in the second mode, the self-generated heat of the fuel cell stack is larger, the temperature difference between the cooling liquid entering and exiting the stack is larger, the direction of the cooling liquid is required to be switched at the moment, and the reversing of the cooling liquid is controlled by adopting fixed frequency;
in the third mode, the self-generated heat of the fuel cell stack is larger, the temperature difference of the cooling liquid entering and exiting the stack is larger, and the cooling liquid reversing and switching time are required to be controlled by adopting a fuzzy PID algorithm aiming at the existing working condition.
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| CN110649281A (en) * | 2019-09-30 | 2020-01-03 | 西安新衡科测控技术有限责任公司 | HT-PEM methanol-water fuel cell cooling liquid circulation control system and control method |
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