A hydrogen energy power system applied to an underwater unmanned platform

Abstract

The application relates to a hydrogen energy power system applied to an underwater unmanned platform, which comprises a PEMFC management system, the PEMFC management system comprises a liquid cooling module and a fuzzy PID controller; the liquid cooling module comprises a radiator, a water tank and a water pump, the water tank is used for buffering the coolant, the water pump drives the coolant to flow among a PEMFC stack, the radiator and the water tank, and the radiator is configured to cool the coolant flowing out of the PEMFC stack; the fuzzy PID controller is electrically connected with the liquid cooling module, and is configured to modulate a PWM control signal according to the collected inlet temperature T out of the coolant of the PEMFC stack and the outlet temperature T st of the coolant on the basis of establishing a voltage and temperature coupling model of the PEMFC stack, control the rotating speed of the water pump and the rotating speed of a radiator fan, thereby control the flow of the coolant and the heat dissipation amount of the coolant, further control the temperature of the PEMFC stack to ensure the stability of the output voltage, and realize the intelligent optimization of dynamic energy conversion and the stable heat management function of the fuel cell in a complex application scenario.

Description

Technical Field

[0001] This invention relates to the field of hydrogen power technology, and in particular to a hydrogen power system for use in underwater unmanned platforms. Background Technology

[0002] Hydrogen energy, as an ideal clean energy source, has the characteristics of high calorific value and zero emissions. Using hydrogen as a clean energy source to replace traditional energy is one of the future development directions. However, hydrogen cannot be used directly; it needs to be converted into heat or electricity before it can be used. Hydrogen fuel cells are devices that convert hydrogen energy into electrical energy.

[0003] Among various hydrogen fuel cells, proton exchange membrane fuel cells (PEMFCs) have attracted much attention due to their superior performance and application prospects. These fuel cells can operate at relatively low temperatures (≤80℃) and pressures (≤ 2 bar) while maintaining high power density, making them highly promising for transportation and distributed energy storage. However, PEMFC stacks also present some challenges during use: 1. As PEMFCs are low-temperature fuel cells, the temperature difference between them and the environment is small, hindering heat dissipation and increasing their own heat load, resulting in high internal temperatures; 2. Temperature significantly affects the output voltage of PEMFC stacks. Therefore, the management system of PEMFC stacks has a crucial impact on their lifespan and stable output. Constructing a scientific PEMFC stack management system and optimizing control strategies to manage the temperature and output voltage of PEMFC stacks are technical problems that need to be addressed. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a hydrogen power system for underwater unmanned platforms, comprising a PEMFC stack composed of multiple identical single fuel cells connected together, characterized in that it further comprises a PEMFC management system, wherein the PEMFC management system includes a liquid cooling module and a fuzzy PID controller.

[0005] The liquid cooling module includes a radiator, a water tank, and a water pump. The water tank is configured to buffer the coolant, and the water pump is configured to drive the coolant to circulate between the PEMFC stack, the radiator, and the water tank. The radiator is configured to dissipate heat and cool the coolant flowing out of the PEMFC stack.

[0006] The fuzzy PID controller is electrically connected to the liquid cooling module and is configured to optimize the model parameters of the voltage and temperature coupling model of the PEMFC stack using a fuzzy PID control algorithm, based on the established voltage and temperature coupling model of the PEMFC stack, and according to the collected PEMFC stack coolant inlet temperature T. outWith coolant outlet temperature T st The PWM control signal is modulated to control the speed of the water pump and the speed of the radiator fan, thereby regulating the flow rate and heat dissipation of the coolant, and thus controlling the temperature of the PEMFC stack to ensure the stability of the output voltage.

[0007] Preferably, the formula for the voltage and temperature coupling model of the PEMFC stack is as follows:

[0008] Vo =n cell V n ;

[0009] V n =EV act -V ohmic -V con ;

[0010] E = [ΔG - ΔS(T - T0) + RT(ln(P H2 )+(ln(P O2 )) / 2)] / (2F);

[0011] V act = ζ1 + ζ2T + ζ3T[ln(C O2 )] + ζ4 T[ln(I)];

[0012] ln(C O2 )=P O2 / (5.08e -6 *exp(-498 / T));

[0013] V ohmic =Ir M L / A;

[0014] V con = -Bln(1-I / A / i max ) ;

[0015] T st = ;

[0016] Q tot = n cell I / (nF)△H;

[0017] Q gas = (q O2 rec C O2 + q H2 rec C H2 + q H2O ,lrec C H2O,l (T) st - T atm );

[0018] Q cl =C pw M w (T st -T out )=A(-13.68q air 2 +70.56q air +5.13)(1 / 2(T out +T st )-T atm );

[0019] M w =(N2 / N 01 )q 01 ;q air = (N1 / N0)q0;

[0020] Q r = εσA st (T st 4 -T atm 4 );

[0021] P st =IV0;

[0022] Among them, V o Indicates the output voltage of the PEMFC stack, n cell V represents the number of individual fuel cells. n V represents the output voltage of a single fuel cell, E represents the thermodynamic electromotive force of a single fuel cell, and V represents the output voltage of a single fuel cell. act V represents the activation voltage loss of a single fuel cell. ohmic This represents the ohmic voltage loss of a single fuel cell, V. con The concentration voltage loss of a single fuel cell is represented by ΔG, Gibbs free energy by F, F by Faraday constant, ΔS by standard molar entropy by T, thermodynamic temperature during the reaction process by T0, reference temperature by R, and universal gas constant by P. H2 P represents the pressure of hydrogen gas. O2 This represents the pressure of oxygen, where ζ1, ζ2, ζ3, and ζ4 are constants, and C O2 Let I be the oxygen concentration, L be the current in a single fuel cell, A be the thickness of the single fuel cell membrane, and r be the area of ​​the single fuel cell membrane. M Indicates the equivalent internal resistance of a single fuel cell, B represents the proportional coefficient, and i maxQ represents the maximum current density. tot Q represents the chemical energy of the hydrogen-oxygen reaction. cl Q represents the amount of heat dissipated by the coolant. gas Q represents the heat carried away by the unreacted gas. r P represents the amount of heat dissipated by environmental radiation. st C represents the output power of the fuel cell stack. st M represents the specific heat capacity of the fuel cell stack. st The value represents the fuel cell mass, n represents the amount of substance in the electrochemical reaction, ΔH represents the enthalpy change parameter of the reaction, and q represents the mass of the fuel cell stack. O2 rec To participate in the reaction oxygen flow rate, q H2 rec To determine the hydrogen flow rate involved in the reaction, q H2O,l rec To generate water vapor flow rate, C O2 For the specific heat capacity of oxygen, C H2 C is the specific heat capacity of hydrogen. H2O,l T is the specific heat capacity of water vapor. atm For ambient temperature, C pw M represents the specific heat capacity of coolant at constant pressure. w N2 represents the coolant flow rate, N2 represents the instantaneous speed of the water pump, and q represents the instantaneous speed of the water pump. 01 N represents the rated flow rate of the water pump. 01 q represents the rated speed of the water pump. air N1 represents the instantaneous airflow of the radiator, N1 represents the instantaneous speed of the radiator fan, q0 represents the rated airflow of the radiator fan, N0 represents the rated speed of the radiator fan, and T represents the instantaneous airflow of the radiator fan. st T represents the outlet temperature of the fuel cell stack coolant. out The inlet temperature of the fuel cell stack is represented by ε, the radiation coefficient by σ, and the Boltzmann constant by A. st This represents the surface area of ​​the fuel cell stack. This model formula can construct a multi-input multi-output, strongly coupled, and nonlinear dynamic coupling model, providing a computational foundation for the implementation of fuzzy control algorithms in PEMFC fuel cell stacks.

[0023] Preferably, the method for establishing the voltage and temperature coupling model of the PEMFC stack is as follows: based on the principle of energy conservation, the heat generation and heat dissipation of the PEMFC stack are equal. The heat is calculated by time differentiation, and the total heat generation power of the PEMFC stack is equal to the total heat dissipation power. Combined with the operating principle of the voltage equivalent circuit of the PEMFC stack, the voltage and temperature coupling model of the PEMFC stack is established.

[0024] Preferably, based on the principle that the total heat generation power of a PEMFC stack is equal to the total heat dissipation power, the heat balance equation for a PEMFC stack is listed as follows:

[0025] Q tot -Q cl-Q gas -Q r -P st = C st M st (dT st / dt);

[0026] Therefore, the T of the PEMFC stack st The calculation formula is as follows:

[0027] T st = .

[0028] Preferably, the heat generated by the PEMFC stack originates from the electrochemical reaction, and the heat generation calculation formula for the stack is as follows:

[0029] Q react =Q tot -P st =n cell I(E0-V n );

[0030] Among them: Q react E0 represents the heat generation power of the PEMFC stack and the reversible voltage.

[0031] Chemical energy Q of the hydrogen-oxygen reaction tot The calculation formula is as follows:

[0032] Q tot = n cell IE0 = n cell q m，react △H;

[0033] q m，react = I / (nF);

[0034] It is concluded that Q tot = n cell I / (nF)△H;

[0035] Where, q m，react The molar flow rate of the reactants is expressed as ΔH = -571.6 kJ·mol⁻¹.

[0036] Preferably, the removal of unreacted gases from the PEMFC stack will carry away some of the internal heat Q. gas The computational workload is as follows:

[0037] Q gas = (q O2 rec C O2 + q H2 rec C H2 + qH2O,l rec C H2O,l (T) st - T atm );

[0038] Where, q O2 rec For the oxygen flow rate participating in the reaction; q H2 rec The hydrogen flow rate participating in the reaction; q H2O,l rec For the generation of water vapor flow rate; C O2 C is the specific heat capacity of oxygen. H2 C is the specific heat capacity of hydrogen. H2O,l T is the specific heat capacity of water vapor; atm The ambient temperature.

[0039] Preferably, the PEMFC stack exchanges heat with the coolant through convection heat transfer, and the heat dissipation Q of the coolant is obtained based on the temperature difference between the inlet and outlet of the coolant. cl :

[0040] Q cl =C pw M w (T st -T out );

[0041] M w =(N2 / N 01 )q 01 ;

[0042] Where: C pw M represents the specific heat capacity of the coolant at constant pressure; w Indicates the instantaneous flow rate of coolant; T st T represents the coolant outlet temperature of the fuel cell stack, which is equal to the fuel cell stack temperature. out This indicates the inlet temperature of the fuel cell stack coolant, which is equal to the outlet temperature of the radiator coolant.

[0043] After the high-temperature coolant flowing out of the PEMFC stack flows into the radiator, the heat is dissipated to the outside through the radiator, and the coolant temperature drops. The cooled coolant then re-enters the PEMFC stack for heat dissipation. Therefore, the heat dissipation of the stack coolant is set to be equal to the heat dissipation of the radiator.

[0044] Q cl = AK(T ra -T atm );

[0045] T ra = 1 / 2(T out +T st );

[0046] K = -13.68q air ^2+70.56q air +5.13;

[0047] q air = (N1 / N0)q0;

[0048] Conclusion: Q cl =C pw M w (T st -T out )=A(-13.68q air 2 +70.56q air +5.13)(1 / 2(T out +T st )-T atm ), where: A is the heat dissipation area of ​​the radiator body; K is the heat transfer coefficient of the radiator; T is the heat transfer coefficient of the radiator. ra Indicates the radiator temperature; T atm Indicates ambient temperature.

[0049] Preferably, a portion of the heat generated by the PEMFC stack is dissipated to the outside through thermal radiation, with the radiative heat dissipation Q... r The calculation formula is as follows:

[0050] Q r = εσA st (T st 4 -T atm 4 );

[0051] Where ε represents the radiation coefficient; σ represents the Boltzmann constant; A st T represents the surface area of ​​the fuel cell stack; atm Indicates ambient temperature.

[0052] Preferably, based on the operating principle of the PEMFC stack voltage equivalent circuit, the output voltage of the PEMFC stack is:

[0053] V o =n cell ·V n ;

[0054] Within a single fuel cell, there are three main types of voltage losses: ohmic voltage loss, activation voltage loss, and concentration voltage loss. The actual output voltage of the fuel cell is equal to the cell's thermodynamic electromotive force minus the sum of these three voltage losses, i.e.:

[0055] V o =EV act -Vohmic -V con ;

[0056] The equivalent circuit of a single fuel cell can be viewed as a power source E connected to an internal resistance. This internal resistance is equivalent to the activation equivalent resistance in series with an ohmic equivalent resistance, then a capacitor in parallel, and finally the concentration gradient equivalent resistance in series. The capacitor reflects the dynamic characteristics of the PEMFC stack. The thermodynamic electromotive force E, also known as the Nernst electromotive force, is given by the following formula:

[0057] E = [ΔG - ΔS(T - T0) + RT(ln(P H2 )+(ln(P O2 )) / 2)] / (2F);

[0058] Activation voltage loss refers to the voltage consumed in a fuel cell system to transfer electrons from one electrode to another as the electrochemical reaction requires overcoming the potential barrier of chemical bonds. Its relationship with current can be expressed by the Butler-Volmer equation, i.e.:

[0059] V act = ζ1 + ζ2T + ζ3T[ln(C O2 )] + ζ4 T[ln(I)]

[0060] ln(C O2 )=P O2 / (5.08e -6 *exp(-498 / T))

[0061] Where: ζ1, ζ2, ζ3, and ζ4 are constants;

[0062] C O2 is the oxygen concentration; I is the current in a single fuel cell;

[0063] Ohmic voltage drop refers to the voltage reduction in a PEMFC caused by the resistance encountered by electrons and protons during their transport through components such as electrodes, electrolytes, and current collectors. This voltage drop follows Ohm's law and is proportional to the product of current and total internal resistance, as shown in the following formula:

[0064] V ohmic =IR ohmic ;

[0065] R ohmic = r M L / A;

[0066] Result: V ohmic =Ir M L / A;

[0067] Where: Rohmic The value of r represents the internal resistance of a single fuel cell, L represents the thickness of the single fuel cell membrane, A represents the area of ​​the single fuel cell membrane, and r represents the internal resistance of a single fuel cell. M This represents the equivalent internal resistance of a single fuel cell.

[0068] Concentration voltage drop refers to the voltage loss caused by the decrease in reactant concentration during the chemical reaction process inside the PCMFC stack. Its calculation equation is as follows:

[0069] V con = -Bln(1-i / i max ) ;

[0070] i = I / A;

[0071] Result: V con = -Bln(1-I / A / i max ) ;

[0072] Where: B represents the proportionality coefficient;

[0073] i max This indicates the maximum current density.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] This invention establishes a temperature management hardware system for a PCMFC fuel cell stack. The system includes a radiator, water tank, water pump, and a fuzzy PID controller. The radiator, water tank, water pump, and PCMFC stack are connected via pipes. The system uses water cooling to manage the PCMFC stack's temperature, addressing the issue of heat accumulation within the stack and thus mitigating the impact of temperature on its output voltage. Based on this hardware system, a voltage-temperature coupling model for the PCMFC stack is established, providing a theoretical basis for computational regulation in fuel cell applications. This enables intelligent optimization of dynamic energy conversion and stable thermal management in complex application scenarios, ensuring efficient and stable operation of the fuel cell. Attached Figure Description

[0076] Figure 1 This is a schematic diagram of the PEMFC liquid cooling system in this invention.

[0077] Figure 2 This is a control strategy diagram of the controller in this invention.

[0078] Figure 3 These are temperature change curves of PEMFC stacks under different control conditions.

[0079] Figure 4The output voltage variation curves of the PEMFC stack under different control conditions are shown.

[0080] Figure 5 The output power variation curves of the PEMFC stack under different control conditions are shown.

[0081] Figure 6 These are the efficiency variation curves of PEMFC stacks under different control conditions.

[0082] Figure 7 It is a QCL curve graph.

[0083] Figure 8 This is a graph showing the QAIR variation under different controllers.

[0084] Figure 9 It is a graph showing the change in cooling water heat dissipation under different controllers.

[0085] Figure 10 This is a graph showing the changes in Kp, Ki, and Kd of the water pump.

[0086] Figure 11 This is a graph showing the changes in Kp, Ki, and Kd of the heat sink.

[0087] Figure 12 This is a graph showing the variation of the pump error E under different controllers.

[0088] Figure 13 This is a graph showing the variation of the heat sink error E under different controllers. Detailed Implementation

[0089] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments are only specific illustrations of the invention and should not be regarded as limitations on the invention. The purpose of the embodiments is to enable those skilled in the art to better understand and reproduce the technical solution of the present invention. The scope of protection of the present invention should still be determined by the scope defined in the claims.

[0090] refer to Figure 1 A hydrogen power system for underwater unmanned platforms includes a PEMFC stack consisting of multiple identical single fuel cells connected together. The improvement of the present invention is that it also includes a PEMFC management system, which includes a liquid cooling module and a fuzzy PID controller.

[0091] The liquid cooling module includes a radiator, a water tank, and a water pump. The water tank is configured to buffer the coolant, preferably cooling water. The water pump is configured to drive the coolant to circulate between the PEMFC stack, the radiator, and the water tank. The radiator is configured to dissipate heat and cool the coolant flowing out of the PEMFC stack. Specifically, the outlet end of the PEMFC stack is connected to the water tank, the water tank is connected to the inlet end of the radiator, the water pump is connected between the water tank and the radiator, and the outlet end of the radiator is connected to the inlet end of the PEMFC stack.

[0092] The fuzzy PID controller is electrically connected to the liquid cooling module; specifically, it is connected to the water pump and the radiator fan. The fuzzy PID controller is configured to optimize the model parameters of the voltage and temperature coupling model of the PEMFC stack using a fuzzy PID control algorithm, based on the established voltage and temperature coupling model, and according to the collected PEMFC stack coolant inlet temperature T. out With coolant outlet temperature T st The PWM control signal is modulated to control the speed of the water pump and the speed of the radiator fan, thereby regulating the flow rate and heat dissipation of the coolant, and thus controlling the temperature of the PEMFC stack to ensure the stability of the output voltage.

[0093] The fuzzy PID controller adjusts the speed of the water pump and the cooling fan. By adjusting the speed of the water pump, the flow rate of the coolant can be changed, thereby affecting the heat exchange between the fuel cell and the coolant. If the inlet temperature of the coolant entering the PEMFC stack is kept constant, the outlet temperature will change accordingly. Adjusting the speed of the radiator fan will change the heat dissipated in the radiator, thereby causing the coolant temperature to drop, which in turn changes the inlet temperature of the coolant entering the PEMFC stack.

[0094] refer to Figure 2 The fuzzy PID controller employs a PID control strategy to control the speed of the circulating water pump and cooling fan; the controller acquires the PEMFC stack coolant inlet temperature T based on the temperature data. out With coolant outlet temperature T st The PWM duty cycle of the circulating water pump and cooling fan is used to adjust their speeds, thereby regulating the water pump flow rate and the radiator exhaust volume, and ultimately controlling the amount of heat dissipated by the coolant.

[0095] Specifically, the formula for the voltage and temperature coupling model of the PEMFC stack is as follows:

[0096] Vo =n cell V n ;

[0097] V n =EVact -V ohmic -V con ;

[0098] E = [ΔG - ΔS(T - T0) + RT(ln(P H2 )+(ln(P O2 )) / 2)] / (2F);

[0099] V act = ζ1 + ζ2T + ζ3T[ln(C O2 )] + ζ4 T[ln(I)];

[0100] ln(C O2 )=P O2 / (5.08e -6 *exp(-498 / T));

[0101] V ohmic =Ir M L / A;

[0102] V con = -Bln(1-I / A / i max ) ;

[0103] T st = ;

[0104] Q tot = n cell I / (nF)△H;

[0105] Q gas = (q O2 rec C O2 + q H2 rec C H2 + q H2O ,l rec C H2O,l )(T st - T atm );

[0106] Q cl =C pw M w (T st -T out )=A(-13.68q air 2 +70.56q air +5.13)(1 / 2(T out +T st )-T atm);

[0107] M w =(N2 / N 01 )q 01 ;q air = (N1 / N0)q0;

[0108] Q r = εσA st (T st 4 -T atm 4 );

[0109] P st =n cell IV0;

[0110] Among them, V o Indicates the output voltage of the PEMFC stack, n cell V represents the number of individual fuel cells. n V represents the output voltage of a single fuel cell, E represents the thermodynamic electromotive force of a single fuel cell, and V represents the output voltage of a single fuel cell. act V represents the activation voltage loss of a single fuel cell. ohmic This represents the ohmic voltage loss of a single fuel cell, V. con The concentration voltage loss of a single fuel cell is represented by ΔG, Gibbs free energy by F, F by Faraday constant, ΔS by standard molar entropy by T, thermodynamic temperature during the reaction process by T0, reference temperature by R, and universal gas constant by P. H2 P represents the pressure of hydrogen gas. O2 This represents the pressure of oxygen, where ζ1, ζ2, ζ3, and ζ4 are constants, and C O2 Let I be the oxygen concentration, L be the current in a single fuel cell, A be the thickness of the single fuel cell membrane, and r be the area of ​​the single fuel cell membrane. M Indicates the equivalent internal resistance of a single fuel cell, B represents the proportional coefficient, and i max Q represents the maximum current density. tot Q represents the chemical energy of the hydrogen-oxygen reaction. cl Q represents the amount of heat dissipated by the coolant. gas Q represents the heat carried away by the unreacted gas. r P represents the amount of heat dissipated by environmental radiation. st C represents the output power of the fuel cell stack. st M represents the specific heat capacity of the fuel cell stack. st The value represents the fuel cell mass, n represents the amount of substance in the electrochemical reaction, ΔH represents the enthalpy change parameter of the reaction, and q represents the mass of the fuel cell stack. O2 rec To participate in the reaction oxygen flow rate, q H2 recTo determine the hydrogen flow rate involved in the reaction, q H2O,l rec To generate water vapor flow rate, C O2 For the specific heat capacity of oxygen, C H2 C is the specific heat capacity of hydrogen. H2O,l T is the specific heat capacity of water vapor. atm For ambient temperature, C pw M represents the specific heat capacity of coolant at constant pressure. w N2 represents the coolant flow rate, N2 represents the instantaneous speed of the water pump, and q represents the instantaneous speed of the water pump. 01 N represents the rated flow rate of the water pump. 01 q represents the rated speed of the water pump. air N1 represents the instantaneous airflow of the radiator, N1 represents the instantaneous speed of the radiator fan, q0 represents the rated airflow of the radiator fan, N0 represents the rated speed of the radiator fan, and T represents the instantaneous airflow of the radiator fan. st T represents the outlet temperature of the fuel cell stack coolant. out The inlet temperature of the fuel cell stack is represented by ε, the radiation coefficient by σ, and the Boltzmann constant by A. st This represents the surface area of ​​the fuel cell stack. This model formula can construct a multi-input multi-output, strongly coupled, and nonlinear dynamic coupling model, providing a computational foundation for the implementation of fuzzy control algorithms in PEMFC fuel cell stacks.

[0111] Specifically, the method for establishing the voltage and temperature coupling model of the PEMFC stack is as follows: based on the principle of energy conservation, the heat generation and heat dissipation of the PEMFC stack are equal. By performing time differential calculation on the heat, the total heat generation power of the PEMFC stack is equal to the total heat dissipation power. Combining the operating principle of the voltage equivalent circuit of the PEMFC stack, the voltage and temperature coupling model of the PEMFC stack is established.

[0112] Based on the principle that the total heat generation power of a PEMFC stack is equal to the total heat dissipation power, the heat balance equation for a PEMFC stack is as follows:

[0113] Q tot -Q cl -Q gas -Q r -P st = C st M st (dT st / dt);

[0114] Therefore, the T of the PEMFC stack st The calculation formula is as follows:

[0115] T st = ;

[0116] Among them: Q totQ represents the chemical energy of the hydrogen-oxygen reaction; cl Indicates the heat dissipation of cooling water; Q gas Q represents the heat carried away by the unreacted gas; r P represents the amount of heat dissipated by environmental radiation. st Indicates the output power of the fuel cell stack; C st M represents the specific heat capacity of the fuel cell stack; st Indicates the mass of the fuel cell stack; T st This indicates the fuel cell stack temperature, which is equal to the fuel cell stack coolant outlet temperature.

[0117] Furthermore, the heat generated by the PEMFC stack originates from electrochemical reactions, and the heat generation calculation formula for the stack is as follows:

[0118] Q react =Q tot -P st =n cell I(E0-V n );

[0119] Among them: Q react E0 represents the heat generation power of the PEMFC stack, and V represents the reversible voltage. n This indicates the output voltage of a single fuel cell.

[0120] Chemical energy Q of the hydrogen-oxygen reaction tot The calculation formula is as follows:

[0121] Q tot = n cell IE0 = n cell q m，react △H;

[0122] In fact, the energy output of a fuel cell, whether electrical or thermal, comes directly from the energy released or absorbed during the breaking and formation of chemical bonds in hydrogen and oxygen, which is the enthalpy difference of the chemical reaction process.

[0123] 2H2 + O2 → 2H2O △H = -571.6 kJ·mol-1

[0124] Using Faraday's second law, the relationship between the amount of electric charge and the amount of chemical reaction products can be obtained as follows:

[0125] Q e = nFζ;

[0126] Among them: Q e ζ represents the amount of charge transferred in the reaction; n represents the amount of substance in the electrochemical reaction; ζ represents the electrochemical progress.

[0127] Dividing both sides by time yields the reactant molar flow rate q. m，react The calculation formula is as follows:

[0128] q m，react = I / (nF);

[0129] It is concluded that Q tot = n cell I / (nF)△H;

[0130] Where, q m，react The molar flow rate of the reactants is expressed as ΔH = -571.6 kJ·mol⁻¹.

[0131] Furthermore, the removal of unreacted gases from the PEMFC stack will carry away some of the internal heat Q. gas The computational workload is as follows:

[0132] Q gas = (q O2 rec C O2 + q H2 rec C H2 + q H2O,l rec C H2O,l (T) st - T atm );

[0133] Where, q O2 rec For the oxygen flow rate participating in the reaction; q H2 rec The hydrogen flow rate participating in the reaction; q H2O,l rec For the generation of water vapor flow rate; C O2 For the specific heat capacity of oxygen, C H2 C is the specific heat capacity of hydrogen. H2O,l T represents the specific heat capacity of water vapor. atm The ambient temperature.

[0134] Preferably, the PEMFC stack exchanges heat with the coolant through convection heat transfer, and the heat dissipation Q of the coolant is obtained based on the temperature difference between the inlet and outlet of the coolant. cl :

[0135] Q cl =C pw M w (T st -T out );

[0136] M w =(N2 / N 01 )q 01 ;

[0137] Where: C pw M represents the specific heat capacity of the coolant at constant pressure; w Indicates the instantaneous flow rate of coolant; T st This indicates the coolant outlet temperature of the fuel cell stack, which is equivalent to the stack temperature; T out This indicates the inlet temperature of the fuel cell stack coolant, which is equivalent to the outlet temperature of the radiator coolant.

[0138] After the high-temperature coolant flowing out of the PEMFC stack flows into the radiator, the heat is dissipated to the outside through the radiator, and the coolant temperature drops. The cooled coolant then re-enters the PEMFC stack for heat dissipation. Therefore, the heat dissipation of the stack coolant is set to be equal to the heat dissipation of the radiator.

[0139] Q cl = AK(T ra -T atm );

[0140] T ra = 1 / 2(T out +T st );

[0141] K = -13.68q air ^2+70.56q air +5.13;

[0142] q air = (N1 / N0)q0;

[0143] Conclusion: Q cl =C pw M w (T st -T out )=A(-13.68q air 2 +70.56q air +5.13)(1 / 2(T out +T st )-T atm ), where: A is the heat dissipation area of ​​the radiator body; K is the heat transfer coefficient of the radiator; T is the heat transfer coefficient of the radiator. ra Indicates the radiator temperature; T atm Indicates ambient temperature.

[0144] Preferably, a portion of the heat generated by the PEMFC stack is dissipated to the outside through thermal radiation, with the radiative heat dissipation Q... r The calculation formula is as follows:

[0145] Q r = εσA st (T st 4 -T atm4 );

[0146] Where ε represents the radiation coefficient; σ represents the Boltzmann constant; A st T represents the surface area of ​​the fuel cell stack; atm Indicates ambient temperature.

[0147] The temperature of the PEMFC stack affects the voltage / power output of the PEMFC stack, and the voltage / power output of the PEMFC stack also affects the temperature of the PEMFC stack. The temperature model and the voltage model are a coupled system.

[0148] The cooling water is deionized water because using alcohol-based cooling water such as ethylene glycol would cause PEMFC poisoning in this project.

[0149] In the PEMFC stack, a circulating water pump drives cooling water through pipelines into the PEMFC to remove the heat generated during PEMFC operation; the function of the water pump is to drive the cooling water circulation to ensure that the heat generated by the battery stack is dissipated quickly and effectively.

[0150] Furthermore, based on the operating principle of the PEMFC stack voltage equivalent circuit, the output voltage of the PEMFC stack is:

[0151] V o =n cell ·V n ;

[0152] Where: V o Indicates the output voltage of the entire fuel cell; n cell V represents the number of individual fuel cells; n This indicates the output voltage of a single fuel cell.

[0153] Within a single fuel cell, there are three main types of voltage losses: ohmic voltage loss, activation voltage loss, and concentration voltage loss. The actual output voltage of the fuel cell is equal to the cell's thermodynamic electromotive force minus the sum of these three voltage losses, i.e.:

[0154] V o =EV act -V ohmic -V con ;

[0155] The equivalent circuit of a single fuel cell can be viewed as a power source E connected to an internal resistance. This internal resistance is equivalent to the activation equivalent resistance in series with an ohmic equivalent resistance, then a capacitor in parallel, and finally the concentration gradient equivalent resistance in series. The capacitor reflects the dynamic characteristics of the PEMFC stack. The thermodynamic electromotive force E, also known as the Nernst electromotive force, is given by the following formula:

[0156] E = [ΔG - ΔS(T - T0) + RT(ln(P H2 )+(ln(P O2 )) / 2)] / (2F);

[0157] Where: ΔG represents the Gibbs free energy, F represents the Faraday constant; ΔS represents the standard molar entropy, T represents the thermodynamic temperature during the reaction process; T0 represents the reference temperature; R represents the universal gas constant, and P... H2 P represents the pressure of hydrogen gas. O2 This indicates the pressure of oxygen.

[0158] Activation voltage loss refers to the voltage consumed in a fuel cell system to transfer electrons from one electrode to another as the electrochemical reaction requires overcoming the potential barrier of chemical bonds. Its relationship with current can be expressed by the Butler-Volmer equation, i.e.:

[0159] V act = ζ1 + ζ2T + ζ3T[ln(C O2 )] + ζ4 T[ln(I)]

[0160] ln(C O2 )=P O2 / (5.08e -6 *exp(-498 / T))

[0161] Where: ζ1, ζ2, ζ3, and ζ4 are constants;

[0162] C O2 I represents the oxygen concentration; I represents the current in a single fuel cell.

[0163] Ohmic voltage drop refers to the voltage reduction in a PEMFC caused by the resistance encountered by electrons and protons during their transport through components such as electrodes, electrolytes, and current collectors. This voltage drop follows Ohm's law and is proportional to the product of current and total internal resistance, as shown in the following formula:

[0164] V ohmic =IR ohmic ;

[0165] R ohmic = r M L / A;

[0166] Result: V ohmic =Ir M L / A;

[0167] Where: R ohmicThe value of r represents the internal resistance of a single fuel cell, L represents the thickness of the single fuel cell membrane, A represents the area of ​​the single fuel cell membrane, and r represents the internal resistance of a single fuel cell. M This represents the equivalent internal resistance of a single fuel cell.

[0168] Concentration voltage drop refers to the voltage loss caused by the decrease in reactant concentration during the chemical reaction process inside the PCMFC stack. Its calculation equation is as follows:

[0169] V con = -Bln(1-i / i max ) ;

[0170] i = I / A;

[0171] Result: V con = -Bln(1-I / A / i max ) ;

[0172] Where: B represents the proportionality coefficient;

[0173] i max This indicates the maximum current density.

[0174] In this embodiment, a temperature management hardware system for the PCMFC stack was constructed. The management hardware system includes a radiator, a water tank, a water pump, and a fuzzy PID controller. The radiator, water tank, water pump, and PCMFC stack are connected by pipes. The management hardware system manages the temperature of the PCMFC stack through water cooling, solving the problem of heat accumulation inside the PCMFC stack and thus addressing the impact of temperature on the output voltage of the PCMFC stack. Based on the temperature management hardware system, a voltage-temperature coupling model of the PCMFC stack was established, providing a theoretical basis for computational regulation of the fuzzy PID control algorithm in fuel cells. This enables intelligent optimization of dynamic energy conversion and stable thermal management of fuel cells in complex application scenarios, ensuring the efficient and stable operation of the fuel cell.

[0175] In this embodiment, the input current in the simulation is the actual current obtained during the test. At the beginning, it rises from 0A to 5A and then pauses for 1-3 seconds before rising to the working current of 16A. When the hydrogen and oxygen flow rate is increased, it will rise to a maximum of 18A. In order to avoid damage to the PEMFC, it drops back to 16A and is maintained at around this level (with slight fluctuations) until the end of the test.

[0176] Figure 3The figures show the temperature change curves of the PEMFC fuel cell stack under different control methods. It can be seen that the temperature gradually rises from room temperature at the start of operation, and the rate of increase slows down under the control of the controllers. At this point, the control effects of the two controllers are similar. However, as the temperature gradually approaches the set temperature of 323.15K, the difference between the two controllers becomes apparent. In fuzzy control, the temperature rises to 323.5K (50.35℃) at 163.6s, at which point the temperature begins to be significantly controlled. After 25.1s, or 188.7s, the temperature is controlled at 323.2K, with an error of only 0.05K from the target value. In contrast, traditional PID control only begins to control the temperature when the stack temperature rises to 324.8K (51.65℃) at 217.8s, and it takes 218.4s for the system to stabilize at 323.3K. In addition to lower control accuracy, traditional PID control is also 247.5s slower than fuzzy control.

[0177] Figures 4-6 These are the output voltage, output power, and stack efficiency curves of a PEMFC stack under different control conditions. The voltage curves further confirm the close relationship between the PEMFC voltage and the stack current and temperature. It can be observed that the initial output voltage can reach 42V, and the voltage decreases with increasing temperature when the current remains constant; the voltage also changes abruptly when the current changes abruptly. The output power is affected by both voltage and current, sometimes exceeding the rated power, reaching a maximum of 537W. Similar to temperature changes, the voltage controlled significantly from 163.6s onwards, 54.2s faster than traditional PID control, with smaller fluctuations, faster speed, and higher efficiency (the efficiency of the fuzzy PID controller reaches 62.4%, 0.4% higher than the traditional method), allowing the PEMFC to reach a stable state more quickly.

[0178] By comparison, it can be found that fuzzy PID control has higher accuracy and speed than traditional control, and the system using fuzzy control also has higher stability.

[0179] In the cooling system, the controller controls the amount of heat dissipated by the coolant by controlling the coolant flow rate of the water pump and the airflow of the radiator. For experimental convenience, the solenoid valve is set to fully open, therefore the coolant flow rate qcl remains unchanged at its maximum value of 200 m³ / h. However, the radiator airflow q... airWhile the PEMFC was still in its temperature rise phase, the airflow was 40 m³ / h. At 163.6 seconds, the fuzzy PID controller began to significantly control the fan speed to regulate the radiator airflow, ensuring the PEMFC stack temperature stabilized within the set temperature range as quickly as possible. After the stack temperature (Tst) stabilized, the radiator airflow also stabilized at 60 m³ / h. In contrast, the traditional PID controller only started controlling the airflow at 217.8 seconds, and its control strength and speed were inferior to the fuzzy PID controller. The change in radiator airflow directly reflects the change in coolant heat dissipation, as shown in the image. Figures 7-9 The comparison clearly shows that, with the water pump flow rate qcl remaining constant, there is a one-to-one correspondence between the change in radiator airflow and the heat dissipation of the coolant.

[0180] In the controller of the coolant system, the fuzzy PID controller optimizes the PID parameters in real time based on the error value E and the rate of change of the error EC, thereby achieving a more accurate and faster control effect. Figures 10-11 The curves showing the variation of Kp, Ki, and Kd for the water pump and radiator using a fuzzy PID controller, and the curves showing the variation of the control error E for the water pump and radiator under different controllers, are presented. The results of automatic parameter tuning show that the final parameters of Kp, Ki, and Kd for the water pump are 0.05, 0.0009, and -1, respectively; the final parameters of Kp, Ki, and Kd for the radiator are 2.5, 0.005, and 0, respectively. Figure 3 shows that the variation curve of E for the water pump is highly similar to the variation curve of Tst for the PEMFC stack temperature, which explains why the water pump flow rate qcl remains constant. Figures 12-13 show that the E for the radiator is highly correlated with its controlled airflow qair, which intuitively illustrates the control principle of the controller.

[0181] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0182] It should be noted that any technical features not described in detail in this invention can be implemented using any existing technology.

Claims

1. A hydrogen power system for underwater unmanned platforms, comprising a PEMFC stack composed of multiple identical single fuel cells connected together, characterized in that, It also includes a PEMFC management system, which includes a liquid cooling module and a fuzzy PID controller; The liquid cooling module includes a radiator, a water tank, and a water pump. The water tank is configured to buffer the coolant, and the water pump is configured to drive the coolant to circulate between the PEMFC stack, the radiator, and the water tank. The radiator is configured to dissipate heat and cool the coolant flowing out of the PEMFC stack. The fuzzy PID controller is electrically connected to the liquid cooling module and is configured to optimize the model parameters of the voltage and temperature coupling model of the PEMFC stack using a fuzzy PID control algorithm based on the established voltage and temperature coupling model of the PEMFC stack. It also modulates the PWM control signal according to the collected PEMFC stack coolant inlet temperature Tout and coolant outlet temperature Tst, and controls the speed of the water pump and radiator fan through the PWM control signal, thereby regulating the coolant flow rate and the heat dissipation of the coolant, and thus controlling the PEMFC stack temperature to ensure the stability of the output voltage.

2. The hydrogen-powered propulsion system for an underwater unmanned platform as described in claim 1, characterized in that, The formula for the voltage and temperature coupling model of the PEMFC stack is as follows: Vo =n cell V n ; V n =EV act -V ohmic -V con ; E = [ΔG - ΔS(T - T0) + RT(ln(P). H2 )+(ln(P O2 )) / 2)] / (2F); V act = ζ1 + ζ2T + ζ3T[ln(C O2 )] + ζ4 T[ln(I)]; ln(C O2 )=P O2 / (5.08e -6 *exp(-498 / T)); V ohmic =Go M THE; V con = -Bln(1-I / A / i max ) ; T st = ; Q tot = n cell I / (nF)△H; Q gas = (q O2 rec C O2 + q H2 rec C H2 + q H2O ,l rec C H2O,l )(T st - T atm ); Q cl =C pw M w (T st -T out )=A(-13.68q air 2 +70.56q air +5.13)(1 / 2(T out +T st )-T atm ); M w =(N2 / N 01 )q 01 ;q air = (N1 / N0)q0; Q r = εσA st (T st 4 -T atm 4 ); P st =IV0; Among them, V o Indicates the output voltage of the PEMFC stack, n cell V represents the number of individual fuel cells. n V represents the output voltage of a single fuel cell, E represents the thermodynamic electromotive force of a single fuel cell, and V represents the output voltage of a single fuel cell. act V represents the activation voltage loss of a single fuel cell. ohmic This represents the ohmic voltage loss of a single fuel cell, V. con The concentration voltage loss of a single fuel cell is represented by ΔG, Gibbs free energy by F, F by Faraday constant, ΔS by standard molar entropy by T, thermodynamic temperature during the reaction process by T0, reference temperature by R, and universal gas constant by P. H2 P represents the pressure of hydrogen gas. O2 The pressure of oxygen is represented by ζ1, ζ2, ζ3, and ζ4, which are constants, C. O2 Let I be the oxygen concentration, L be the current in a single fuel cell, A be the thickness of the single fuel cell membrane, and r be the area of ​​the single fuel cell membrane. M Indicates the equivalent internal resistance of a single fuel cell, B represents the proportional coefficient, and i max Q represents the maximum current density. tot Q represents the chemical energy of the hydrogen-oxygen reaction. cl Q represents the amount of heat dissipated by the coolant. gas Q represents the heat carried away by the unreacted gas. r P represents the amount of heat dissipated by environmental radiation. st C represents the output power of the fuel cell stack. st M represents the specific heat capacity of the fuel cell stack. st The value represents the fuel cell mass, n represents the amount of substance in the electrochemical reaction, ΔH represents the enthalpy change parameter of the reaction, and q represents the mass of the fuel cell stack. O2 rec To participate in the reaction oxygen flow rate, q H2 rec To determine the hydrogen flow rate involved in the reaction, q H2O,l rec To generate water vapor flow rate, C O2 For the specific heat capacity of oxygen, C H2 C is the specific heat capacity of hydrogen. H2O,l T is the specific heat capacity of water vapor. atm For ambient temperature, C pw M represents the specific heat capacity of coolant at constant pressure. w N2 represents the coolant flow rate, N2 represents the instantaneous speed of the water pump, and q represents the instantaneous speed of the water pump. 01 N represents the rated flow rate of the water pump. 01 q represents the rated speed of the water pump. air N1 represents the instantaneous airflow of the radiator, N1 represents the instantaneous speed of the radiator fan, q0 represents the rated airflow of the radiator fan, N0 represents the rated speed of the radiator fan, and T represents the instantaneous airflow of the radiator fan. st T represents the outlet temperature of the fuel cell stack coolant. out The inlet temperature of the fuel cell stack is represented by ε, the radiation coefficient by σ, and the Boltzmann constant by A. st This represents the surface area of ​​the fuel cell stack.

3. The hydrogen-powered propulsion system for an underwater unmanned platform as described in claim 2, characterized in that, The method for establishing the voltage and temperature coupling model of the PEMFC stack is as follows: Based on the principle of energy conservation, the heat generation and heat dissipation of the PEMFC stack are equal. The heat is calculated by time differentiation, and the total heat generation power of the PEMFC stack is equal to the total heat dissipation power. Combined with the operating principle of the voltage equivalent circuit of the PEMFC stack, the voltage and temperature coupling model of the PEMFC stack is established.

4. The hydrogen-powered propulsion system for an underwater unmanned platform as described in claim 3, characterized in that, Based on the principle that the total heat generation power of a PEMFC stack is equal to the total heat dissipation power, the heat balance equation for a PEMFC stack is as follows: Q tot -Q cl -Q gas -Q r -P st = C st M st (dT st / dt); Therefore, the T of the PEMFC stack st The calculation formula is as follows: T st = 。 5. A hydrogen-powered propulsion system for an underwater unmanned platform as described in claim 4, characterized in that, The heat generated by the PEMFC fuel cell stack originates from electrochemical reactions. The formula for calculating the heat generation of the fuel cell stack is as follows: Q react =Q tot -P st =n cell I(E0-V n ); Among them: Q react E0 represents the heat generation power of the PEMFC stack and the reversible voltage. Chemical energy Q of the hydrogen-oxygen reaction tot The calculation formula is as follows: Q tot = n cell IE0 = n cell q m，react △H; q m，react = I / (nF); It is concluded that Q tot = n cell I / (nF)△H; Where, ΔH = -571.6 kJ·mol⁻¹; q m，react This indicates the molar flow rate of the reactants.

6. A hydrogen-powered propulsion system for an underwater unmanned platform as described in claim 5, characterized in that, The removal of unreacted gases from inside the PEMFC stack carries away some of the internal heat (Q). gas The computational workload is as follows: Q gas = (q O2 rec C O2 + q H2 rec C H2 + q H2O,l rec C H2O,l )(T st - T atm ); Where, q O2 rec For the oxygen flow rate participating in the reaction; q H2 rec The hydrogen flow rate participating in the reaction; q H2O,l rec For the water vapor generation flow rate; C O2 C is the specific heat capacity of oxygen. H2 C is the specific heat capacity of hydrogen. H2O,l T is the specific heat capacity of water vapor; atm The ambient temperature.

7. A hydrogen-powered propulsion system for an underwater unmanned platform as described in claim 6, characterized in that, The PEMFC fuel cell stack exchanges heat with the coolant through convection heat transfer, and the heat dissipation Q of the coolant is obtained based on the temperature difference between the inlet and outlet of the coolant. cl : Q cl =C pw M w (T st -T out ); M w =(N2 / N 01 )q 01 ; Where: C pw M represents the specific heat capacity of the coolant at constant pressure; w Indicates the instantaneous flow rate of coolant; T st T represents the coolant outlet temperature of the fuel cell stack, which is equal to the fuel cell stack temperature. out This indicates the inlet temperature of the fuel cell stack coolant, which is equal to the outlet temperature of the radiator coolant. After the high-temperature coolant flowing out of the PEMFC stack flows into the radiator, the heat is dissipated to the outside through the radiator, and the coolant temperature drops. The cooled coolant then re-enters the PEMFC stack for heat dissipation. Therefore, the heat dissipation of the stack coolant is set to be equal to the heat dissipation of the radiator. Q cl = AK(T ra -T atm ) T ra = 1 / 2(T out +T st ); K = -13.68q air ^2+70.56q air +5.13; q air = (N1 / N0)q0; Conclusion: Q cl =C pw M w (T st -T out )=A(-13.68q air 2 +70.56q air +5.13)(1 / 2(T out +T st )-T atm ), where: A is the heat dissipation area of ​​the radiator body; K is the heat transfer coefficient of the radiator; T is the heat transfer coefficient of the radiator. ra Indicates radiator temperature; T atm Indicates ambient temperature.

8. A hydrogen-powered propulsion system for an underwater unmanned platform as described in claim 7, characterized in that, A portion of the heat generated by the PEMFC stack is dissipated to the outside through thermal radiation, with the radiative heat dissipation Q... r The calculation formula is as follows: Q r = εσA st (T st 4 -T atm 4 ); Where ε represents the radiation coefficient; σ represents the Boltzmann constant; A st T represents the surface area of ​​the fuel cell stack; atm Indicates ambient temperature.

9. A hydrogen-powered propulsion system for an underwater unmanned platform as described in claim 8, characterized in that, Based on the operating principle of the PEMFC stack voltage equivalent circuit, the output voltage of the PEMFC stack is: V o =n cell ·V n ; Inside a single fuel cell, there are three main types of voltage loss: ohmic voltage loss, activation voltage loss, and concentration voltage loss. The actual output voltage of a fuel cell is calculated using the following formula: V o =EV act -V ohmic -V con ; The equivalent circuit of a single fuel cell is a power source E connected to an internal resistance. This internal resistance is equivalent to the activation equivalent resistance in series with an ohmic equivalent resistance, then a capacitor in parallel, and finally the concentration gradient equivalent resistance in series. The capacitor reflects the dynamic characteristics of the PEMFC stack. The thermodynamic electromotive force E, also known as the Nernst electromotive force, is given by the following formula: E = [ΔG - ΔS(T - T0) + RT(ln(P). H2 )+(ln(P O2 )) / 2)] / (2F) Activation voltage loss refers to the voltage consumed in a fuel cell system to transfer electrons from one electrode to another as the electrochemical reaction requires overcoming the potential barrier of chemical bonds. Its relationship with current can be expressed by the Butler-Volmer equation, i.e.: V act = ζ1 + ζ2T + ζ3T[ln(C O2 )] + ζ4 T[ln(I)] ln(C O2 )=P O2 / (5.08e -6 *exp(-498 / T)) Where: ζ1, ζ2, ζ3, and ζ4 are constants; C O2 is the oxygen concentration; I is the current in a single fuel cell; Ohmic voltage drop follows Ohm's law and is proportional to the product of current and total internal resistance, as shown in the following formula: V ohmic = IS ohmic ; R ohmic = r M L / A; Result: V ohmic =Ir M L / A; Where: R ohmic The value of r represents the internal resistance of a single fuel cell, L represents the thickness of the single fuel cell membrane, A represents the area of ​​the single fuel cell membrane, and r represents the internal resistance of a single fuel cell. M This represents the equivalent internal resistance of a single fuel cell. Concentration voltage drop refers to the voltage loss caused by the decrease in reactant concentration during the chemical reaction process inside a PCMFC. Its calculation equation is as follows: V con = -Bln(1-i / i max ) ; i = I / A; Achieved: V con = -Bln(1-I / A / i max ) ; Where: B represents the proportionality coefficient; i max This indicates the maximum current density.

Images