CN109818016B - Temperature self-regulating method for cathode open type fuel cell - Google Patents

Temperature self-regulating method for cathode open type fuel cell Download PDF

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CN109818016B
CN109818016B CN201910083968.8A CN201910083968A CN109818016B CN 109818016 B CN109818016 B CN 109818016B CN 201910083968 A CN201910083968 A CN 201910083968A CN 109818016 B CN109818016 B CN 109818016B
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temperature
cathode
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CN109818016A (en
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王亚雄
陈铨
林飞
廖锐越
张博
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Fuzhou University
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Abstract

The invention provides a temperature self-regulating method of a cathode open type fuel cell, which is used for the cathode open type fuel cell with a fan and comprises the following steps; a1, establishing a thermodynamic model of the cathode open type fuel cell according to the physical characteristics and experimental empirical parameters of the cathode open type fuel cell; a2, simulating the established thermodynamic model to compare the temperature rise curve obtained by simulation with experimental data to verify the effectiveness of the model; a3, designing a closed-loop control system comprising a composite controller by a verified thermodynamic model, and controlling the temperature of the fuel cell by the closed-loop control system according to the thermodynamic model, wherein the composite controller is a fuzzy-PID composite controller comprising a PID controller and a fuzzy control rule matched with the PID controller; the fuzzy-PID composite controller can be used for realizing the self-regulation of the temperature of the fuel cell under the condition of variable working conditions; the invention can control the temperature in the fuel cell stack to ensure that the cathode open type fuel cell stably works in the optimal temperature range.

Description

Temperature self-regulating method for cathode open type fuel cell
Technical Field
The invention relates to the technical field of fuel cells, in particular to a temperature self-regulating method of a cathode open type fuel cell.
Background
The proton exchange membrane fuel cell is an important development direction of global new energy at present and even in the future because of the advantages of low carbon, environmental protection, no pollution and the like, the market share of hydrogen energy as a high-efficiency renewable energy source is higher and higher, and China also accelerates the development of the hydrogen energy industry in the trend of global hydrogen energy utilization. The hydrogen energy fuel cell automobile is used as a large application industry of hydrogen energy, and has become a key direction for the development of new energy automobiles in the future due to the advantages of high energy density of a galvanic pile, long endurance, short hydrogenation time, low operation temperature and the like compared with a pure electric battery automobile. The open cathode fuel cell is one kind of proton exchange membrane fuel cell, and has no other auxiliary system to lower cost and raise the cost of fuel cell.
The temperature of the open cathode proton exchange membrane fuel cell has important significance on the service efficiency and the service life of the fuel cell. If the cell temperature is too low, the electrochemical reaction slows, thereby preventing evaporation of liquid water within the proton exchange membrane and degrading cell performance. However, excessive temperatures can lead to catalyst and heat waste due to excessive chemical reactions within the proton exchange membrane, resulting in evaporation of liquid water, thereby reducing proton conductivity. Open cathode fuel cells are also problematic in that they remove other auxiliary systems while controlling stack temperature.
Therefore, the problem to be solved by those skilled in the art is to effectively control the stack temperature of the open cathode fuel cell while keeping the open cathode fuel cell low in cost and simple in structure without other auxiliary systems.
Disclosure of Invention
The invention provides a temperature self-regulating method of a cathode open type fuel cell, which can control the temperature in a fuel cell stack to ensure that the cathode open type fuel cell stably works in an optimal temperature range.
The invention adopts the following technical scheme.
A method for self-regulating the temperature of an open cathode fuel cell, for use in an open cathode fuel cell in which the temperature of the cell is regulated by a fan, comprising: the self-adjusting method comprises the following steps;
a1, establishing a thermodynamic model of the cathode open type fuel cell according to the physical characteristics and experimental empirical parameters of the cathode open type fuel cell;
a2, simulating the established thermodynamic model to compare the temperature rise curve obtained by simulation with experimental data to verify the effectiveness of the model;
a3, designing a closed-loop control system comprising a composite controller by a verified thermodynamic model, and controlling the temperature of the fuel cell by the closed-loop control system according to the thermodynamic model, wherein the composite controller is a fuzzy-PID composite controller comprising a PID controller and a fuzzy control rule matched with the PID controller; the fuzzy-PID composite controller can be used for realizing the self-regulation of the temperature of the fuel cell under the condition of variable working conditions.
The closed-loop control system is a cathode open type fuel cell temperature self-regulating control system based on an Arduino microcontroller.
The establishment method of the thermodynamic model is based on the derivation and mathematical analysis of an energy conservation equation and a related empirical formula; the deviation amount of the thermodynamic model and the actual thermodynamic field is within the acceptable range of the open cathode fuel cell temperature regulation;
the thermodynamic model is established as follows;
open cathode fuel cell stack temperature TFCThe following functional relationships are provided:
Figure BDA0001961163030000021
wherein
Figure BDA0001961163030000022
Energy released for the electrochemical reaction of the fuel cell, and
Figure BDA0001961163030000023
is related to the hydrogen mass flow rate of the fuel cell anode reaction
Figure BDA0001961163030000024
And cathode oxygen mass flow rate
Figure BDA0001961163030000025
A function of (a);
PFCthe power generated for the cathode open fuel cell electrochemical reaction has a functional relationship:
PFC＝n*Vcell*IFC(ii) a A second formula;
n is the number of fuel cell monomers, VcellFor the actual output voltage of the fuel cell unit, IFCOutputting current for the electric pile; vcellThe actual output voltage has a functional relation:
Vcell＝E-Vact-Vohm-Vconc(ii) a A formula III;
in which E is a thermodynamic electromotive force, VactTo activate overvoltage, VohmIs an ohmic overvoltage, VconcIs concentration polarization overvoltage;
Figure BDA0001961163030000026
is the heat radiation quantity in the electrochemical process of the fuel cell and the temperature T of the electric pileFCIt is related.
Figure BDA0001961163030000027
For the convection of the cooling air, there is the equation:
Figure BDA0001961163030000028
it can be seen from the above equation that the convection flow of the heat dissipating air is composed of two parts, one of which is natural convection
Figure BDA0001961163030000029
The other part is forced convection
Figure BDA00019611630300000210
And respectively have the equation:
Figure BDA00019611630300000211
Figure BDA00019611630300000212
wherein natural convection occurs at the outer sidewall of the fuel cell and forced convection occurs at the inner sidewall of the cell so that the heat exchange area A of the natural convectionnatAnd heat exchange area A of forced convectionforcDifferent, simultaneous heat convection transfer coefficient hnatAnd hforcAlso different; and h isforcCan be expressed as:
Figure BDA00019611630300000213
wherein Wca，inIs a cathode open fuel cell cathode air mass flow rate and has:
Wca，in＝pair*vca，in*Achannel(ii) a A formula eight;
in the formula: p is a radical ofairIs the cathode peripheral air density, vca，inCathode air intake flow rate, A, measured by an air flow rate sensor installed in an internal passage of the fuel cellchannelIs the effective channel area;
because of the voltage V of the air velocity sensorsensorWith the velocity v of the air flowca，inThere is a certain functional relationship due to the air mass flow rate Wca，inWith inlet flow velocity vca，inProportional, and the cathode oxygen mass flow rate is related to the air mass flow rate:
Figure BDA0001961163030000031
so oxygen mass flow rate
Figure BDA0001961163030000032
With the air velocity sensor voltage VsensorFunctional relation exists, and the following functional relation can be obtained after data fitting:
Figure BDA0001961163030000033
oxygen mass flow rate for open cathode fuel cell cathode reaction
Figure BDA0001961163030000039
Comprises the following steps:
Figure BDA0001961163030000034
wherein the content of the first and second substances,
Figure BDA0001961163030000035
is the oxygen molar mass, and F is the Faraday constant;
so that the cathode oxygen excess ratio of the open cathode fuel cell can be obtained:
Figure BDA0001961163030000036
in the formula twelve, the oxygen excess ratio must be satisfied for the normal and stable operation of the cathode open type fuel cell
Figure BDA0001961163030000037
The fan of the cathode open type fuel cell not only has the oxygen supply function of the traditional fuel cell air compressor to provide the excess oxygen supply ratio for the fuel cell, but also has the function of an auxiliary cooling system; therefore, when the cathode open type fuel cell is provided with the fan for cooling, the linear relation exists between the mass flow rate of air sucked by the fan during the operation of the fan and the input voltage at two ends of the fan, the rotating speed of the fan can be controlled by modulating the pulse width u (t), and the mass flow rate of air can be obtained by experimental data fitting after the functional relation between the voltage at two ends of the fan and the pulse width u (t) is established
Figure BDA0001961163030000038
The relationship with the fan pulse width u (t) is as follows:
Figure BDA0001961163030000041
in the formula beta1And beta2The constant obtained by fitting, and the value of the pulse width u (t) ranges from 0 to 1.
The input quantity of the PID controller is the difference between the real-time temperature of the fuel cell and the control target temperature, namely temperature deviation, and the output quantity of the PID controller is the rotating speed of the fan;
in the closed-loop control system, the rotating speed of a fan is used as an input parameter of a fuel cell thermodynamic model, the fuel cell thermodynamic model is used for calculating the real-time temperature of the fuel cell, and the real-time temperature is output and fed back to the system.
The fuzzy control rule is a two-dimensional fuzzy control rule, the fuzzy input quantity of the fuzzy control rule is a derivative of temperature deviation and temperature deviation, namely a temperature deviation rate, the temperature deviation is e (t), and the temperature deviation rate is
Figure BDA0001961163030000042
Fourteen formula, the output is PID controller parameter correction quantity delta KP、ΔKIAnd Δ KD(ii) a The fuzzy implication relation algorithm of the fuzzy control rule uses a Mamdani algorithm, the fuzzy control rule uses an area center method when the fuzzy control rule carries out clarification processing on fuzzy quantity, and the fuzzy control rule and a PID controller are compounded to form a fuzzy-PID composite controller.
The temperature self-regulation method of the fuel cell under the variable working condition comprises the following steps of; the fuzzy-PID composite controller sets and online adjusts three parameters Kp, Ki and Kd of the PID controller according to a fuzzy rule, so that the cathode open type fuel cell automatically corrects the rotating speed of the fan when the working condition changes, and the effect of temperature self-regulation is achieved;
the input quantity of the PID controller is the difference between the target temperature and the real-time temperature of the fuel cell stack, namely temperature deviation e (t), and the output quantity is the fan rotating speed pulse width u(t)And has the formula:
Figure BDA0001961163030000043
in the formula KPTo proportional gain, KITo integrate the gain, KDIs the differential gain.
The fuzzy-PID composite controller sets and online adjusts three parameters Kp, Ki and Kd of the PID controller according to 49 fuzzy rules.
The closed-loop control system comprises a cathode open type fuel cell with a fan, an Arduino controller, a fan driving circuit, a temperature sensor and a PC upper computer; the PC upper computer can operate a fuel cell thermodynamic model; the fuzzy-PID composite controller comprises an Arduino controller; the fuzzy-PID composite controller obtains the rotating speed of the fan through the fan driving circuit and controls the fan.
The fan driving circuit comprises an L494 pulse width modulation control chip, a 15V direct current power supply, a diode and an enhanced NMOS (N-channel metal oxide semiconductor) tube;
the Arduino controller is connected with the end of a PC upper computer through a USB interface, and the PC upper computer utilizes MATLAB to interact with the Arduino controller through a serial port;
the Arduino controller is connected with the temperature sensor through a digital I/O port to read the temperature in the cathode open type fuel cell stack in real time, and outputs an analog voltage signal through the digital I/O port to control the fan driving circuit to output a PWM value so as to realize the control of the rotating speed of the cathode open type fuel cell direct current fan and further adjust the temperature of the fuel cell.
The Arduino controller is Arduino Uno R3; the fan of the cathode open type fuel cell is a direct current fan; the direct current fan is used for providing oxygen required by the reaction for the fuel cell and also used as a cooling fan for regulating the temperature of the fuel cell.
The invention has the following advantages: the invention can effectively solve the problem that the temperature of the electric pile is controlled on the basis of keeping the structure of the cathode open type fuel cell unchanged and not increasing other fuel cell auxiliary systems. The method can effectively inherit the advantage of low cost of the cathode open type fuel cell, and the cathode open type fuel cell temperature self-regulating method has the advantages of quick response, settable target temperature, real-time temperature control, high control precision, capability of effectively eliminating interference caused by load change and the like.
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The invention is described in further detail below with reference to the following figures and detailed description:
FIG. 1 is a graph comparing temperature rise curves of thermodynamic models of open cathode fuel cells in an embodiment of the present invention;
FIG. 2 is a schematic diagram of the open cathode fuel cell temperature self-regulation of the present invention;
FIG. 3 is a graph showing the effect of temperature control according to the present invention;
FIG. 4 is a schematic diagram of the control system of the present invention;
FIG. 5 is a schematic diagram of a fan control circuit according to an embodiment of the present invention;
in the figure: 1-a fan; 2-a fan drive circuit; 3-temperature sensor.
Detailed Description
As shown in fig. 1 to 5, a method for self-regulating the temperature of an open cathode fuel cell, which is used for regulating the temperature of the open cathode fuel cell by a fan 1, is characterized in that: the self-adjusting method comprises the following steps;
a1, establishing a thermodynamic model of the cathode open type fuel cell according to the physical characteristics and experimental empirical parameters of the cathode open type fuel cell;
a2, simulating the established thermodynamic model to compare the temperature rise curve obtained by simulation with experimental data to verify the effectiveness of the model;
a3, designing a closed-loop control system comprising a composite controller by a verified thermodynamic model, and controlling the temperature of the fuel cell by the closed-loop control system according to the thermodynamic model, wherein the composite controller is a fuzzy-PID composite controller comprising a PID controller and a fuzzy control rule matched with the PID controller; the fuzzy-PID composite controller can be used for realizing the self-regulation of the temperature of the fuel cell under the condition of variable working conditions.
The closed-loop control system is a cathode open type fuel cell temperature self-regulating control system based on an Arduino microcontroller.
The establishment method of the thermodynamic model is based on the derivation and mathematical analysis of an energy conservation equation and a related empirical formula; the deviation amount of the thermodynamic model and the actual thermodynamic field is within the acceptable range of the open cathode fuel cell temperature regulation;
the thermodynamic model is established as follows;
open cathode fuel cell stack temperature TFCThe following functional relationships are provided:
Figure BDA0001961163030000061
wherein
Figure BDA0001961163030000062
Energy released for the electrochemical reaction of the fuel cell, and
Figure BDA0001961163030000063
is related to the hydrogen mass flow rate of the fuel cell anode reaction
Figure BDA0001961163030000064
And cathode oxygen mass flow rate
Figure BDA0001961163030000065
A function of (a);
PFCthe power generated for the cathode open fuel cell electrochemical reaction has a functional relationship:
PFC＝n*Vcell*IFC(ii) a A second formula;
n is the number of fuel cell monomers, VcellFor the actual output voltage of the fuel cell unit, IFCOutputting current for the electric pile; vcellThe actual output voltage has a functional relation:
Vcell＝E-Vact-Vohm-Vconc(ii) a A formula III;
in which E is a thermodynamic electromotive force, VactTo activate overvoltage, VohmIs an ohmic overvoltage, VconcIs concentration polarization overvoltage;
Figure BDA0001961163030000066
is the heat radiation quantity in the electrochemical process of the fuel cell and the temperature T of the electric pileFCIt is related.
Figure BDA0001961163030000067
For the convection of the cooling air, there is the equation:
Figure BDA0001961163030000068
it can be seen from the above equation that the convection flow of the heat dissipating air is composed of two parts, one of which is natural convection
Figure BDA0001961163030000069
The other part is forced convection
Figure BDA00019611630300000610
And respectively have the equation:
Figure BDA00019611630300000611
Figure BDA00019611630300000612
wherein natural convection occurs at the outer sidewall of the fuel cell and forced convection occurs at the inner sidewall of the cell so that the heat exchange area A of the natural convectionnatAnd heat exchange area A of forced convectionforcDifferent, simultaneous heat convection transfer coefficient hnatAnd hforcAlso different; and h isforcCan be expressed as:
Figure BDA00019611630300000613
wherein Wca，inIs a cathode open fuel cell cathode air mass flow rate and has:
Wca，in＝pair*vca，in*Achannel(ii) a A formula eight;
in the formula: p is a radical ofairIs the cathode peripheral air density, vca，inCathode air intake flow rate, A, measured by an air flow rate sensor installed in an internal passage of the fuel cellchannelIs the effective channel area;
because of the voltage V of the air velocity sensorsensorWith the velocity v of the air flowca，inThere is a certain functional relationship due to the air mass flow rate Wca，inWith inlet flow velocity vca，inProportional, and the cathode oxygen mass flow rate is related to the air mass flow rate:
Figure BDA0001961163030000071
so oxygen mass flow rate
Figure BDA0001961163030000072
With the air velocity sensor voltage VsensorFunctional relation exists, and the following functional relation can be obtained after data fitting:
Figure BDA0001961163030000073
oxygen mass flow rate for open cathode fuel cell cathode reaction
Figure BDA00019611630300000710
Comprises the following steps:
Figure BDA0001961163030000074
wherein the content of the first and second substances,
Figure BDA0001961163030000075
is the oxygen molar mass, and F is the Faraday constant;
so that the cathode oxygen excess ratio of the open cathode fuel cell can be obtained:
Figure BDA0001961163030000076
in the formula twelve, the oxygen excess ratio must be satisfied for the normal and stable operation of the cathode open type fuel cell
Figure BDA0001961163030000077
The fan of the cathode open type fuel cell not only has the oxygen supply function of the traditional fuel cell air compressor to provide the excess oxygen supply ratio for the fuel cell, but also has the function of an auxiliary cooling system; therefore, when the cathode open type fuel cell is provided with the fan for cooling, the linear relation exists between the mass flow rate of air sucked by the fan during the operation of the fan and the input voltage at two ends of the fan, the rotating speed of the fan can be controlled by modulating the pulse width u (t), and the mass flow rate of air can be obtained by experimental data fitting after the functional relation between the voltage at two ends of the fan and the pulse width u (t) is established
Figure BDA0001961163030000078
The relationship with the fan pulse width u (t) is as follows:
Figure BDA0001961163030000079
in the formula beta1And beta2The constant obtained by fitting, and the value of the pulse width u (t) ranges from 0 to 1.
The input quantity of the PID controller is the difference between the real-time temperature of the fuel cell and the control target temperature, namely temperature deviation, and the output quantity of the PID controller is the rotating speed of the fan;
in the closed-loop control system, the rotating speed of a fan is used as an input parameter of a fuel cell thermodynamic model, the fuel cell thermodynamic model is used for calculating the real-time temperature of the fuel cell, and the real-time temperature is output and fed back to the system.
The fuzzy control rule is a two-dimensional fuzzy control rule, the fuzzy input quantity of the fuzzy control rule is a derivative of temperature deviation and temperature deviation, namely a temperature deviation rate, the temperature deviation is e (t), and the temperature deviation rate is
Figure BDA0001961163030000081
Fourteen formula, the output is PID controller parameter correction quantity delta KP、ΔKIAnd Δ KD(ii) a The fuzzy implication relation algorithm of the fuzzy control rule uses a Mamdani algorithm, the fuzzy control rule uses an area center method when the fuzzy control rule carries out clarification processing on fuzzy quantity, and the fuzzy control rule and a PID controller are compounded to form a fuzzy-PID composite controller.
The temperature self-regulation method of the fuel cell under the variable working condition comprises the following steps of; the fuzzy-PID composite controller sets and online adjusts three parameters Kp, Ki and Kd of the PID controller according to a fuzzy rule, so that the cathode open type fuel cell automatically corrects the rotating speed of the fan when the working condition changes, and the effect of temperature self-regulation is achieved;
the input quantity of the PID controller is the difference between the target temperature and the real-time temperature of the fuel cell stack, namely temperature deviation e (t), the output quantity is the fan rotating speed pulse width u (t), and the PID controller has the following formula:
Figure BDA0001961163030000082
in the formula KPTo proportional gain, KITo integrate the gain, KDIs the differential gain.
The fuzzy-PID composite controller sets and online adjusts three parameters Kp, Ki and Kd of the PID controller according to 49 fuzzy rules.
The closed-loop control system comprises a cathode open type fuel cell with a fan 1, an Arduino controller, a fan driving circuit 2, a temperature sensor 3 and a PC upper computer; the PC upper computer can operate a fuel cell thermodynamic model; the fuzzy-PID composite controller comprises an Arduino controller; the fuzzy-PID composite controller obtains the rotating speed of the fan through the fan driving circuit and controls the fan.
The fan driving circuit comprises an L494 pulse width modulation control chip, a 15V direct current power supply, a diode and an enhanced NMOS (N-channel metal oxide semiconductor) tube;
the Arduino controller is connected with the end of a PC upper computer through a USB interface, and the PC upper computer utilizes MATLAB to interact with the Arduino controller through a serial port;
the Arduino controller is connected with the temperature sensor through a digital I/O port to read the temperature in the cathode open type fuel cell stack in real time, and outputs an analog voltage signal through the digital I/O port to control the fan driving circuit to output a PWM value (duty ratio) so as to realize the control of the rotating speed of the cathode open type fuel cell direct current fan and further adjust the temperature of the fuel cell.
The Arduino controller is Arduino Uno R3; the fan of the cathode open type fuel cell is a direct current fan; the direct current fan is used for providing oxygen required by the reaction for the fuel cell and also used as a cooling fan for regulating the temperature of the fuel cell.
Example 1:
after the cathode open type fuel cell thermodynamic model is established, in order to verify the effectiveness of the model, the invention compares and observes the temperature change experiment of the fuel cell at the load constant current of 0-300 seconds 10A and 300-600 seconds 20A with the temperature change curve simulated by the model in MATLAB/Simulink, and the cathode open type fuel cell thermodynamic model established in the acceptable deviation range shown in FIG. 1 is real and effective.
In this embodiment, the target temperature of the 1000w cathode open fuel cell is 50 degrees celsius, and as shown in fig. 2, the specific algorithm of the fuzzy-PlD composite controller adopted by the present invention for controlling the temperature of the cathode open fuel cell stack is as follows:
the input quantity of the PID controller is the difference between the target temperature and the real-time temperature of the fuel cell stack, namely temperature deviation e (t), the output quantity is the fan rotating speed pulse width u (t), and the PID controller has the following formula:
Figure BDA0001961163030000091
in the formula KPTo proportional gain, KITo integrate the gain, KDIs the differential gain.
Because the load of the fuel cell can change at any time during the operation process, the PID parameters need to be continuously adjusted on line to realize the accurate control of the temperature of the electric pile. The input of the two-dimensional fuzzy controller designed by the invention comprises temperature deviation e (t) and temperature deviation rate
Figure BDA0001961163030000092
The output is PID parameter correction quantity delta KP、ΔKIAnd Δ KD。
The invention summarizes three parameters K of temperature deviation e (t), temperature deviation rate ec (t) and PID in experience summary and data processing after multiple operationsP、KI、KDThe relationship between the two and the establishment of the corresponding fuzzy rule is as follows:
let the ambiguity field of the temperature deviation e (t) in the fuzzy input be [ -3, 3]The ambiguity range of the temperature deviation rate ec (t) is [ -3, 3 [)]The correction quantity delta K of the fuzzy output PID parameterP、ΔKIAnd Δ KDAre respectively [ -3, 3 [ -3 [)]，[-0.06，0.06]， [-0.3，0.3]。
Select 7 fuzzy subsets: negative large (NG), Negative Medium (NM), Negative Small (NS), zero (Z), Positive Small (PS), Positive Medium (PM), positive large (PB), all used to cover domains of input and output quantities. And a triangular membership function is selected.
When the temperature deviation e (t) is negative and the temperature deviation ratio ec (t) is negative, the larger Δ K is selectedP. When e (t) is positive, and ec (t) is positive, it should take the larger Δ KP. Correction quantity of control variable Δ KPThe specific fuzzy control rule of (1) is as follows:
Figure BDA0001961163030000101
when the temperature deviation e (t) is negative and the temperature deviation ratio ec (t) is negative, the larger Δ K is selectedI. When e (t) is positive, and ec (t) is positive, it should take the larger Δ KI. Correction quantity of control variable Δ KIThe specific fuzzy control rule of (1) is as follows:
Figure BDA0001961163030000102
Figure BDA0001961163030000111
when the temperature deviation e (t) is negative and the temperature deviation ratio ec (t) is negative and large, the positive and small values of Δ K should be selectedD. When e (t) is positive, and ec (t) is positive, it should take larger Δ KD. Correction quantity of control variable Δ KDThe specific fuzzy control rule of (1) is as follows:
Figure BDA0001961163030000112
further after fuzzy reasoning, the area center method is selected for defuzzification to obtain fuzzy output delta KP、ΔKIAnd Δ KD。
In the present embodiment, the fuel cell load current I is setFC20A in 0-300s and 30A in 300-600 s. To satisfy the excess oxygen ratio
Figure BDA0001961163030000113
The minimum rotation speed u of the fan can be obtainedmin(t), and the output of the fuzzy-PID composite controller satisfies u (t) being more than or equal to umin(t) to ensure stable operation of the fuel cell.
According to the fuzzy rule, the fuzzy controller can correct the PID parameters of the cathode open type fuel cell under the variable working condition in real time so as to realize the function of the temperature self-regulation of the closed loop control system. After the initial amount of the PID parameter is determined, the present embodiment performs a simulation experiment on the designed fuzzy-PID composite controller under the load current change (variable working condition), as shown in fig. 3, where the load current is 20A at 0-300s, and the load current is suddenly changed to 30A at 300s, and the simulation result shows that the designed fuzzy-PID composite controller can reach the target temperature of 50 degrees celsius and effectively eliminate the interference caused by the load change.
Example 2:
after verifying the effectiveness of the designed fuzzy-PID composite controller in the temperature regulation of the cathode open type fuel cell, the present embodiment further designs a cathode open type fuel cell temperature self-regulation control system based on an Arduino microcontroller, as shown in fig. 4, which is described in detail as follows:
the temperature self-regulation control system of the cathode open type fuel cell based on the Arduino microcontroller comprises: the fuel cell comprises an open cathode fuel cell, a fan, an Arduino UNO 3, a fan driving circuit, a temperature sensor and a PC upper computer.
Furthermore, in the control system, Arduino UNO R3 is connected with an upper computer PC end through a USB interface and is interacted with Arduino UNO R3 through a serial port by using MATLAB, and Arduino UNO R3 is connected with a temperature sensor through digital I/ O ports 5, 6 and 7 to read the temperature in the cathode open type fuel cell stack in real time and output an analog voltage signal through the digital I/O port 3 to control the PWM value output by the fan driving circuit so as to realize the control of the direct current fan rotating speed of the cathode open type fuel cell, thereby further regulating the fuel cell temperature.
Further, the fan driving circuit mainly includes: TL494 PWM control chip, 15V DC power supply, diode and enhancement NMOS transistor, as shown in FIG. 5. Pin 3 of TL494 is connected to Arduino UNO R3 digital pin 3, pin 10 outputs PWM signal to connect to the gate of the enhancement NMOS transistor, pin 12 is connected to the positive pole of the 15V dc power supply to supply power to the TL494 PWM control chip, and pin 7 is connected to the negative pole of the 15V dc power supply. And a 10k resistor R1 is connected between the gate of the enhancement NMOS transistor and the ground. The source electrode of the enhanced NMOS tube is grounded, and the drain electrode is connected with the positive electrode Vcc of the power supply of the fan. A freewheeling diode is arranged at two ends of the fan to play a role in freewheeling protection.
Further, the enhancement NMOS transistor used in this embodiment has a model of IRF730, and the diode has a model of UF 5408.
Further, the temperature sensor used in this embodiment is a K-type thermocouple and a MAX6675 module to realize real-time measurement of the temperature of the fuel cell stack, where VCC and GND of the MAX6675 module are respectively connected to 5V and GND of the Arduino Uno R3 controller to provide power for the MAX6675, signal pins SO, CS, and CSK of the MAX6675 module are connected to digital pins 5, 6, and 7, the positive and negative electrodes of the K-type thermocouple are respectively connected to T and T-of the MAX6675 module, and the thermocouple is placed inside the open cathode fuel cell to detect the temperature inside the fuel cell stack in real time.
Furthermore, the control system guides a designed fuzzy-PID composite controller algorithm program into Arduino Uno R3 through MATLAB, the deviation between real-time data measured by the temperature sensor connected with Arduino Uno R3 and a target temperature value set in the program is used as the input of the fuzzy-PID composite controller, corresponding analog voltage is given to TL494 through the control algorithm to control a PWM signal of a fan driving circuit, and the rotating speed of the direct current fan is adjusted in real time to keep the temperature of the fuel cell at the set target temperature.
The parameter t in the above formula is a time parameter.

Claims (9)

1. A method for self-regulating the temperature of an open cathode fuel cell, for use in an open cathode fuel cell in which the temperature of the cell is regulated by a fan, comprising: the self-adjusting method comprises the following steps;
a1, establishing a thermodynamic model of the cathode open type fuel cell according to the physical characteristics and experimental empirical parameters of the cathode open type fuel cell;
a2, simulating the established thermodynamic model to compare the temperature rise curve obtained by simulation with experimental data to verify the effectiveness of the model;
a3, designing a closed-loop control system comprising a composite controller by a verified thermodynamic model, and controlling the temperature of the fuel cell by the closed-loop control system according to the thermodynamic model, wherein the composite controller is a fuzzy-PID composite controller comprising a PID controller and a fuzzy control rule matched with the PID controller; the fuzzy-PID composite controller can be used for realizing the self-regulation of the temperature of the fuel cell under the condition of variable working conditions; the establishment method of the thermodynamic model is based on the derivation and mathematical analysis of an energy conservation equation and a related empirical formula; the deviation amount of the thermodynamic model and the actual thermodynamic field is within the acceptable range of the open cathode fuel cell temperature regulation;
the thermodynamic model is established as follows;
open cathode fuel cell stack temperature TFCThe following functional relationships are provided:
Figure FDA0003191479030000011
wherein
Figure FDA0003191479030000012
Energy released for the electrochemical reaction of the fuel cell, and
Figure FDA0003191479030000013
is related to the hydrogen mass flow rate of the fuel cell anode reaction
Figure FDA0003191479030000014
And cathode oxygen mass flow rate
Figure FDA0003191479030000015
A function of (a);
PFCas cathode open fuelThe power generated by the electrochemical reaction of the battery has a functional relation:
PFC＝n*Vcell*IFC(ii) a A second formula;
n is the number of fuel cell monomers, VcellFor the actual output voltage of the fuel cell unit, IFCOutputting current for the electric pile; vcellThe actual output voltage has a functional relation:
Vcell＝E-Vact-Vohm-Vconc(ii) a A formula III;
in which E is a thermodynamic electromotive force, VactTo activate overvoltage, VohmIs an ohmic overvoltage, VconcIs concentration polarization overvoltage;
Figure FDA0003191479030000016
is the heat radiation quantity in the electrochemical process of the fuel cell and the temperature T of the electric pileFC(ii) related;
Figure FDA0003191479030000017
for the convection of the cooling air, there is the equation:
Figure FDA0003191479030000018
it can be seen from the above equation that the convection flow of the heat dissipating air is composed of two parts, one of which is natural convection
Figure FDA0003191479030000019
The other part is forced convection
Figure FDA0003191479030000021
And respectively have the equation:
Figure FDA0003191479030000022
Figure FDA0003191479030000023
wherein natural convection occurs at the outer sidewall of the fuel cell and forced convection occurs at the inner sidewall of the cell so that the heat exchange area A of the natural convectionnatAnd heat exchange area A of forced convectionforcDifferent, simultaneous heat convection transfer coefficient hnatAnd hforcAlso different; and h isforcCan be expressed as:
Figure FDA0003191479030000024
wherein Wca，inIs a cathode open fuel cell cathode air mass flow rate and has:
Wca，in＝pair*vca，in*Achannel(ii) a A formula eight;
in the formula: p is a radical ofairIs the cathode peripheral air density, vca，inCathode air intake flow rate, A, measured by an air flow rate sensor installed in an internal passage of the fuel cellchannelIs the effective channel area;
because of the voltage V of the air velocity sensorsensorWith the velocity v of the air flowca，inThere is a certain functional relationship due to the air mass flow rate Wca，inWith inlet flow velocity vca，inProportional, and the cathode oxygen mass flow rate is related to the air mass flow rate:
Figure FDA0003191479030000025
so oxygen mass flow rate
Figure FDA0003191479030000026
Voltage of air velocity sensorVsensorFunctional relation exists, and the following functional relation can be obtained after data fitting:
Figure FDA0003191479030000027
oxygen mass flow rate for open cathode fuel cell cathode reaction
Figure FDA0003191479030000028
Comprises the following steps:
Figure FDA0003191479030000029
wherein the content of the first and second substances,
Figure FDA00031914790300000210
is the oxygen molar mass, and F is the Faraday constant;
so that the cathode oxygen excess ratio of the open cathode fuel cell can be obtained:
Figure FDA00031914790300000211
in the formula twelve, the oxygen excess ratio must be satisfied for the normal and stable operation of the cathode open type fuel cell
Figure FDA0003191479030000031
The fan of the cathode open type fuel cell not only has the oxygen supply function of the traditional fuel cell air compressor to provide the excess oxygen ratio for the fuel cell, but also has the function of an auxiliary cooling system; therefore, when the cathode open type fuel cell is cooled by the fan, the linear relation exists between the mass flow rate of air sucked by the fan during the operation of the fan and the input voltage at two ends of the fan, the rotating speed of the fan can be controlled by modulating the pulse width u (t), and the voltage at two ends of the fan and the pulse width u (t) are established) The air mass flow rate can be obtained by fitting experimental data after the function relation
Figure FDA0003191479030000032
The relationship with the fan pulse width u (t) is as follows:
Figure FDA0003191479030000033
in the formula beta1And beta2The constant obtained by fitting, and the value of the pulse width u (t) ranges from 0 to 1.
2. The method of claim 1, wherein the method further comprises: the closed-loop control system is a cathode open type fuel cell temperature self-regulating control system based on an Arduino microcontroller.
3. The method of claim 1, wherein the method further comprises: the input quantity of the PID controller is the difference between the real-time temperature of the fuel cell and the control target temperature, namely temperature deviation, and the output quantity of the PID controller is the rotating speed of the fan; in the closed-loop control system, the rotating speed of a fan is used as an input parameter of a fuel cell thermodynamic model, the fuel cell thermodynamic model is used for calculating the real-time temperature of the fuel cell, and the real-time temperature is output and fed back to the system.
4. The method of claim 1, wherein the method further comprises: the fuzzy control rule is a two-dimensional fuzzy control rule, the fuzzy input quantity of the fuzzy control rule is the derivative of the temperature deviation and the temperature deviation, namely the temperature deviation rate, and the output is PID controller parameter correction quantity delta KP、ΔKIAnd Δ KD(ii) a The fuzzy implication relation algorithm of the fuzzy control rule uses a Mamdani algorithm, the fuzzy control rule uses an area center method when the fuzzy control rule carries out sharpening processing on fuzzy quantity, and the fuzzy control rule and the PI are usedThe D controller is compounded to form a fuzzy-PID compound controller.
5. The method of claim 4, wherein the method further comprises: the temperature self-regulation method of the fuel cell under the variable working condition comprises the following steps of; the fuzzy-PID composite controller uses fuzzy rule to K of PID controllerp，KiAnd KdSetting and online adjusting the three parameters to enable the cathode open type fuel cell to automatically correct the rotating speed of the fan when the working condition changes, so as to achieve the effect of temperature self-regulation;
the input quantity of the PID controller is the difference between the target temperature and the real-time temperature of the fuel cell stack, namely temperature deviation e (t), and the output quantity is the fan rotating speed pulse width u(t)；KpTo proportional gain, KiTo integrate the gain, KdIs the differential gain.
6. The open cathode fuel cell temperature self-regulating method of claim 5, wherein: k of fuzzy-PID composite controller according to 49 fuzzy rulesp，KiAnd KdAnd setting and online adjusting the three parameters.
7. The open cathode fuel cell temperature self-regulating method of claim 5, wherein: the closed-loop control system comprises a cathode open type fuel cell with a fan, an Arduino controller, a fan driving circuit, a temperature sensor and a PC upper computer; the PC upper computer can operate a fuel cell thermodynamic model; the fuzzy-PID composite controller comprises an Arduino controller; the fuzzy-PID composite controller obtains the rotating speed of the fan through the fan driving circuit and controls the fan.
8. The method of claim 7, wherein the method further comprises: the fan driving circuit comprises an L494 pulse width modulation control chip, a 15V direct current power supply, a diode and an enhanced NMOS (N-channel metal oxide semiconductor) tube;
the Arduino controller is connected with the end of a PC upper computer through a USB interface, and the PC upper computer utilizes MATLAB to interact with the Arduino controller through a serial port;
the Arduino controller is connected with the temperature sensor through a digital I/O port to read the temperature in the cathode open type fuel cell stack in real time, and outputs an analog voltage signal through the digital I/O port to control the fan driving circuit to output a PWM value so as to realize the control of the rotating speed of the cathode open type fuel cell direct current fan and further adjust the temperature of the fuel cell.
9. The method of claim 7, wherein the method further comprises: the Arduino controller is Arduino Uno R3; the fan of the cathode open type fuel cell is a direct current fan; the direct current fan is used for providing oxygen required by the reaction for the fuel cell and also used as a cooling fan for regulating the temperature of the fuel cell.
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