Proton exchange membrane electrolytic cell self-adaptive frequency modulation control method considering temperature-pressure-water influence

Abstract

The invention discloses a temperature-pressure-water influence-considered self-adaptive frequency modulation control method for a proton exchange membrane electrolytic cell, which comprises the following steps of: 1) constructing a PEMEL dynamic model considering a temperature, pressure and water content coupling effect on the basis of PEMEL dynamic operation characteristics, and providing an accurate model basis for the design of a frequency modulation control strategy; 2) analyzing the frequency modulation performance of the PEMEL at different steady-state operation points; 3) analyzing the influence mechanism of the temperature, the pressure and the water content of the PEMEL on the maximum hydrogen production power of the PEMEL; 4) providing a frequency modulation power compensation method of the PEMEL under the influence of temperature, pressure and water content; and 5) based on the fuzzy control theory and the real-time state of the operation point of the PEMEL, designing a virtual inertia and a primary frequency modulation parameter adaptive setting mechanism of the PEMEL, and researching a PEMEL adaptive frequency modulation strategy. According to the PEMEL adaptive frequency modulation control strategy considering the temperature-pressure-water influence, accurate perception and dynamic optimization control of the PEMEL frequency modulation performance are realized.

Description

TECHNICAL FIELD

[0001] The application relates to the field of frequency regulation of an electric hydrogen comprehensive energy system, and in particular to a self-adaptive frequency regulation control method for a proton exchange membrane electrolyzer considering temperature-pressure-water effects. BACKGROUND

[0002] With the rapid advancement of global energy transformation, renewable energy represented by wind power and photovoltaic power has replaced traditional fossil energy power generation on a large scale, resulting in a sharp decrease in the inertia of the power system and a significant weakening of the frequency regulation capability. Under this background, PEMEL shows great potential in power system frequency regulation services due to its fast response characteristics and flexible power regulation capability. However, the frequency regulation performance of PEMEL is significantly affected by multiple factors such as temperature, pressure and water content, making the frequency regulation control of PEMEL in actual operation face severe challenges.

[0003] At present, some scholars have made important progress in the aspects of PEMEL basic modeling, electrochemical characteristic analysis and hydrogen production efficiency optimization, laying a theoretical foundation for the development of PEMEL technology. However, existing researches mostly focus on the steady-state operation characteristics of PEMEL, and the in-depth analysis of its dynamic frequency regulation performance is still insufficient. Especially under the coupling effect of multiple environmental factors such as temperature change, pressure fluctuation and water content change, the frequency regulation response characteristics of PEMEL show strong nonlinear and multi-time scale coupling complex dynamic characteristics, and the traditional single parameter control strategy is difficult to meet the technical requirements of accurate frequency regulation.

[0004] Therefore, it is urgent to break through the single parameter regulation mode of traditional PEMEL frequency regulation control, establish a dynamic frequency regulation control theory that can comprehensively consider the coupling effects of temperature, pressure and water content, develop a frequency regulation strategy with adaptive parameter setting capability, and realize accurate and stable frequency regulation control of PEMEL under complex environmental conditions. SUMMARY

[0005] The purpose of the present application is to provide a self-adaptive frequency regulation control method for a proton exchange membrane electrolyzer considering temperature-pressure-water effects, comprising the following steps:

[0006] Step 1) Based on the dynamic operation characteristics of the proton exchange membrane electrolyzer PEMEL, a PEMEL dynamic model considering the coupling effects of temperature, pressure and water content is constructed;

[0007] Step 2) Determine the frequency regulation performance of PEMEL at different steady-state operating points;

[0008] Step 3) Refer to the frequency regulation performance of PEMEL at different steady-state operating points, and construct a frequency regulation power compensation sub-model considering temperature-pressure-water content according to the PEMEL dynamic model;

[0009] Step 4) Based on the frequency modulation power compensation sub-model, a virtual inertia and primary frequency modulation control correction model of PEMEL is constructed;

[0010] Step 5) Based on the fuzzy control theory and the real-time state of the operating point of PEMEL, the virtual inertia coefficient and the primary frequency modulation coefficient are adaptively set;

[0011] Step 6) Based on the virtual inertia coefficient and the primary frequency modulation coefficient, the primary frequency modulation power is calculated by using the virtual inertia and primary frequency modulation control correction model of PEMEL, so as to realize the adaptive frequency modulation control of PEMEL.

[0012] Further, the PEMEL dynamic model considering the coupling effects of temperature, pressure and water content includes a PEMEL electrochemical model considering the temperature-pressure-water content coupling effect and a PEMEL dynamic physical model considering the temperature-pressure-water content coupling effect.

[0013] Further, the PEMEL electrochemical model considering the temperature-pressure-water content coupling effect is as follows:

[0014] (1)

[0015] In the formula, , , , is the end voltage of PEMEL, the reversible voltage, the voltage generated by the internal ohmic resistance, and the concentration difference overvoltage; , is the double-layer voltage.

[0016] Further, the reversible voltage is as follows:

[0017] (2)

[0018] (3)

[0019] (4)

[0020] In the formula, is the reversible voltage reference value, is the gas constant, is the electrolyte temperature, F is the Faraday constant, is the partial pressure of hydrogen, is the partial pressure of oxygen, is the gas partial pressure of water in the cathode / anode chamber;

[0021] The ohmic overvoltage is the voltage drop generated by the internal equivalent resistance of the electrolytic cell, that is:

[0022] (5)

[0023] (6)

[0024] wherein, represents the PEMEL membrane electrode thickness, represents the membrane conductivity, represents the membrane water content; represents the current density;

[0025] The double layer voltage of the PEMEL is as follows:

[0026] (7)

[0027] (8)

[0028] wherein, and respectively represent the charge transfer coefficients of the anode and the cathode, and respectively represent the exchange current densities of the anode and the cathode;

[0029] The concentration difference overvoltage is as follows:

[0030] (9)

[0031] wherein, is the amount of transferred electrons, is the maximum current allowed by the PEMEL.

[0032] Further, the dynamic physical model of the PEMEL includes an internal temperature dynamic change model, a pressure dynamic change model, and a water content dynamic change model.

[0033] The internal temperature dynamic change model is as follows:

[0034] (10)

[0035] wherein, is the number of series and parallel connections of the PEMEL monomers, is a thermodynamic model coefficient, is the hydrogen production efficiency, and are temperature coefficients and heat loss coefficients; is the hydrogen production power, is the ambient temperature, is the reference temperature; t is time;

[0036] The pressure dynamic change model is as follows:

[0037] (11)

[0038] wherein, , and are the gas volumes of hydrogen, oxygen and water vapor respectively, and are the hydrogen production and oxygen production rates respectively, and are the hydrogen exhaust and oxygen exhaust rates respectively, and are the water replenishment and water consumption rates respectively, and are the water vapor evaporation and condensation rates respectively.

[0039] The water content dynamic change model is shown as follows:

[0040] (12)

[0041] wherein, , and are the water content dynamic coefficient, diffusion loss coefficient and evaporation loss coefficient respectively, is the electro-osmotic drag coefficient, is the reference water content for normal operation of the membrane, is the water saturated vapor pressure.

[0042] Further, when the PEMEL is operated at a low steady state point, the frequency modulation capability when the frequency fluctuates upward is stronger than that when the PEMEL is operated at a high steady state point, and the frequency modulation capability when the frequency fluctuates downward is weaker than that when the PEMEL is operated at a high steady state point.

[0043] Further, the temperature-pressure-water content frequency modulation power compensation sub-model considers temperature compensation, pressure compensation and water content compensation of the frequency modulation power.

[0044] The temperature compensation of the frequency modulation power is shown as follows:

[0045] (13)

[0046] wherein, is the frequency modulation power compensation amount caused by temperature change, is the temperature compensation coefficient, is the reference temperature;

[0047] The pressure compensation of the frequency modulation power is shown as follows:

[0048] (14)

[0049] wherein, is the frequency deviation caused by the pressure change, is the pressure compensation coefficient, is the reference pressure;

[0050] The water content compensation term of the frequency modulation power is as follows:

[0051] (15)

[0052] wherein, is the frequency deviation caused by the water content change, is the water content compensation coefficient, is the reference water content.

[0053] Further, the virtual inertia and primary frequency modulation control correction model of the PEMEL is as follows:

[0054] (16)

[0055] (17)

[0056] wherein, and respectively represent the virtual inertia and the primary frequency modulation coefficient, is the frequency deviation; is the sum of the virtual inertia and the primary frequency modulation power of the PEMEL after correction.

[0057] Further, in step 5), the step of solving the virtual inertia and the primary frequency modulation control correction model of the PEMEL based on the fuzzy control theory and the real-time state of the operating point of the PEMEL includes:

[0058] Step 5.1) inputting the power at the steady-state operating point of the PEMEL and the system frequency change rate into the fuzzy controller for adjusting the virtual inertia coefficient to obtain the upper correction amount or the lower correction amount of the virtual inertia coefficient;

[0059] inputting the power at the steady-state operating point of the PEMEL and the system frequency deviation into the fuzzy controller for adjusting the primary frequency modulation coefficient to obtain the upper correction amount or the lower correction amount of the primary frequency modulation coefficient;

[0060] Step 5.2) calculating the virtual inertia coefficient of the PEMEL based on the upper correction amount or the lower correction amount of the virtual inertia coefficient;

[0061] calculating the primary frequency modulation coefficient of the PEMEL based on the upper correction amount or the lower correction amount , the first-order frequency modulation coefficient of the PEMEL is calculated;

[0062] The virtual inertia coefficient and the first-order frequency modulation coefficient are shown as follows:

[0063] (18)

[0064] (19)

[0065] In the formula, f is frequency.

[0066] Further, the input and output variables of the fuzzy controller are divided into negative big NB, negative small NS, zero Z, positive small PS, and positive big PB fuzzy sets by using triangular membership functions or trapezoidal membership functions.

[0067] The control rules used by the fuzzy controller for adjusting the virtual inertia coefficient are shown as follows:

[0068] When the power of the steady-state operating point is large and the frequency variation rate is large, the upper correction amount of the virtual inertia coefficient is moderate, and the lower correction amount is large.

[0069] When the power of the steady-state operating point is moderate and the frequency variation rate is moderate, both the upper correction amount and the lower correction amount of the virtual inertia coefficient are moderate.

[0070] When the power of the steady-state operating point is small and the frequency variation rate is large, the upper correction amount of the virtual inertia coefficient is large, and the lower correction amount is moderate.

[0071] The control rules used by the fuzzy controller for adjusting the first-order frequency modulation coefficient are shown as follows:

[0072] When the power of the steady-state operating point is large and the frequency deviation is large, the upper correction amount of the first-order frequency modulation coefficient is moderate, and the lower correction amount is large.

[0073] When the power of the steady-state operating point is moderate and the frequency deviation is moderate, both the upper correction amount and the lower correction amount of the first-order frequency modulation coefficient are moderate.

[0074] When the power of the steady-state operating point is small and the frequency deviation is large, the upper correction amount of the first-order frequency modulation coefficient is large, and the lower correction amount is moderate.

[0075] The technical effect of the present application is self-evident. The present application proposes a self-adaptive frequency modulation control strategy of PEMEL under the influence of temperature-pressure-water. Firstly, the dynamic response mechanism of the temperature, pressure and water content inside PEMEL is analyzed in depth, and an electrochemical model and a temperature-pressure-water content dynamic model of PEMEL are constructed, thereby providing an accurate model basis for the design of the frequency modulation control strategy. Secondly, based on the power-frequency characteristics of PEMEL, the frequency modulation performance of PEMEL at different steady-state operating points is analyzed. Then, based on the fuzzy control principle and the real-time state of the operating point of PEMEL, a double-input double-output fuzzy control rule for adjusting the virtual inertia coefficient and the droop coefficient is designed, and a self-adaptive virtual inertia and primary frequency modulation control strategy considering temperature-pressure-water coupling compensation is proposed. BRIEF DESCRIPTION OF DRAWINGS

[0076] Fig. 1 is a self-adaptive frequency modulation control flowchart of PEMEL considering the influence of temperature-pressure-water;

[0077] Fig. 2 is a hydrogen production power diagram of PEMEL participating in frequency modulation;

[0078] Fig. 3 is a system frequency deviation diagram of PEMEL participating in frequency modulation. DETAILED DESCRIPTION

[0079] The present application will be further described below in conjunction with embodiments, but should not be understood as limiting the above-mentioned subject matter of the present application to the following embodiments. Various substitutions and modifications can be made according to ordinary technical knowledge and conventional means in the art without departing from the above-mentioned technical idea of the present application, and all of them should be included in the protection scope of the present application.

[0080] Embodiment 1:

[0081] Referring to Figs. 1-3 , the self-adaptive frequency modulation control method of the proton exchange membrane electrolyzer considering the influence of temperature-pressure-water includes the following steps:

[0082] Step 1) Based on the dynamic operating characteristics of the proton exchange membrane electrolyzer (PEMEL), a dynamic model of PEMEL considering the coupling effect of temperature, pressure and water content is constructed;

[0083] Step 2) The frequency modulation performance of PEMEL at different steady-state operating points is determined;

[0084] Step 3) Referring to the frequency modulation performance of PEMEL at different steady-state operating points, a frequency modulation power compensation sub-model considering temperature-pressure-water is constructed according to the dynamic model of PEMEL;

[0085] Step 4) Based on the frequency modulation power compensation sub-model, a virtual inertia and primary frequency modulation control correction model of PEMEL is constructed;

[0086] Step 5) Based on the fuzzy control theory and the real-time state of the operating point of PEMEL, the virtual inertia coefficient and the primary frequency modulation coefficient are adaptively set;

[0087] Step 6) Based on the virtual inertia coefficient and the primary frequency modulation coefficient, the primary frequency modulation power is calculated by using the virtual inertia and primary frequency modulation control correction model of PEMEL, so as to realize the adaptive frequency modulation control of PEMEL.

[0088] Embodiment 2:

[0089] Referring to Figs. 1-3 , the adaptive frequency modulation control method of the proton exchange membrane electrolyzer considering the temperature-pressure-water influence, the technical content is the same as that of embodiment 1, further, the PEMEL dynamic model considering the temperature-pressure-water coupling effect includes the PEMEL electrochemical model considering the temperature-pressure-water coupling effect, the PEMEL dynamic physical model considering the temperature-pressure-water coupling effect.

[0090] Embodiment 3:

[0091] Referring to Figs. 1-3 , the adaptive frequency modulation control method of the proton exchange membrane electrolyzer considering the temperature-pressure-water influence, the technical content is the same as that of any one of embodiments 1-2, further, the PEMEL electrochemical model considering the temperature-pressure-water coupling effect is as follows:

[0092] (1)

[0093] In the formula, , , , is the end voltage, reversible voltage, internal ohmic resistance generated voltage, concentration difference overvoltage of PEMEL; , is the double-layer voltage.

[0094] Embodiment 4:

[0095] Referring to Figs. 1-3 , the adaptive frequency modulation control method of the proton exchange membrane electrolyzer considering the temperature-pressure-water influence, the technical content is the same as that of any one of embodiments 1-3, further, the reversible voltage is as follows:

[0096] (2)

[0097] (3)

[0098] (4)

[0099] wherein, Vrefis the reversible voltage reference value, R is the gas constant, T is the cell temperature, F is the Faraday constant, PH2is the partial pressure of hydrogen, PO2is the partial pressure of oxygen, PH2O is the partial pressure of water in the anode / cathode compartment;

[0100] The ohmic overvoltage is the voltage drop due to the internal equivalent resistance of the cell, i.e.

[0101] (5)

[0102] (6)

[0103] wherein, PEMELis the PEMEL membrane electrode thickness, σ is the membrane conductivity, C is the water content of the membrane; J is the current density;

[0104] The double layer voltage of the PEMEL is given by:

[0105] (7)

[0106] (8)

[0107] wherein, and are the charge transfer coefficients for the anode and cathode, respectively, and are the exchange current densities for the anode and cathode, respectively;

[0108] The concentration difference overvoltage is given by:

[0109] (9)

[0110] wherein, n is the number of electrons transferred, Imaxis the maximum current allowed by the PEMEL.

[0111] Example 5:

[0112] Referring to Figs. 1-3, the adaptive frequency control method of the proton exchange membrane electrolyzer considering temperature-pressure-water influence, the technical content is the same as any one of embodiments 1-4, further, the dynamic physical model of the PEMEL includes an internal temperature dynamic change model, a pressure dynamic change model, and a water content dynamic change model;

[0113] The internal temperature dynamic change model is as follows:

[0114] (10)

[0115] In the formula, is the number of series and parallel of the PEMEL monomer, is the thermodynamic model coefficient, is the hydrogen production efficiency, and are the temperature coefficient and the heat loss coefficient; is the hydrogen production power, is the ambient temperature, is the reference temperature; t is time;

[0116] The pressure dynamic change model is as follows:

[0117] (11)

[0118] In the formula, , and are the gas volumes of hydrogen, oxygen and water vapor respectively, and are the hydrogen production and oxygen production rates respectively, and are the hydrogen discharge and oxygen discharge rates respectively, and are the water supply and water consumption rates respectively, and are the evaporation and condensation rates of water vapor.

[0119] The water content dynamic change model is as follows:

[0120] (12)

[0121] In the formula, , and are the water content dynamic coefficient, the diffusion loss coefficient and the evaporation loss coefficient respectively, is the electroosmotic drag coefficient, is the reference water content for normal operation of the membrane, is the water saturated vapor pressure.

[0122] Embodiment 6:

[0123] Referring to Figs. 1-3 , the adaptive frequency control method of the PEMEL considering temperature-pressure-water influences, the technical content is the same as any one of embodiments 1-5, further, when the PEMEL is running at a low steady state point, the frequency fluctuation ability is stronger than that when the PEMEL is running at a high steady state point, and the frequency fluctuation ability is weaker than that when the PEMEL is running at a high steady state point.

[0124] The low steady state point and the high steady state point are both fuzzy concepts, and there is no specific limit. Among them, the low steady state point is usually defined as a certain amount (for example, the running point is at 30% of the maximum power point as a low steady state point) that the PEMEL running point is less than 50% of the maximum power point.

[0125] Embodiment 7:

[0126] Referring to Figs. 1-3 , the adaptive frequency control method of the PEMEL considering temperature-pressure-water influences, the technical content is the same as any one of embodiments 1-6, further, the frequency compensation sub-model considering temperature-pressure-moisture content includes a temperature compensation term, a pressure compensation term, and a moisture content compensation term of the frequency compensation power;

[0127] Among them, the temperature compensation term of the frequency compensation power is as follows:

[0128] (13)

[0129] In the formula, is the frequency compensation power compensation amount caused by temperature change, is the temperature compensation coefficient, is the reference temperature;

[0130] The pressure compensation term of the frequency compensation power is as follows:

[0131] (14)

[0132] In the formula, is the frequency compensation power compensation amount caused by pressure change, is the pressure compensation coefficient, is the reference pressure;

[0133] The moisture content compensation term of the frequency compensation power is as follows:

[0134] (15)

[0135] In the formula, is the frequency compensation power compensation amount caused by moisture content change, is the moisture content compensation coefficient, is the reference moisture content.

[0136] Example 8:

[0137] Referring to Figs. 1-3 , the adaptive frequency control method of the PEMEL considering temperature-pressure-water influences, the technical content is the same as any one of examples 1-7, further, the virtual inertia and primary frequency modulation correction model of the PEMEL is as follows:

[0138] (16)

[0139] (17)

[0140] In the formula, and respectively represent the virtual inertia and the primary frequency modulation coefficient, is the frequency deviation; is the sum of the virtual inertia and the primary frequency modulation power of the PEMEL after correction.

[0141] Example 9:

[0142] Referring to Figs. 1-3 , the adaptive frequency control method of the PEMEL considering temperature-pressure-water influences, the technical content is the same as any one of examples 1-8, further, in step 5), based on the fuzzy control theory and the real-time state of the operating point of the PEMEL, the steps of solving the virtual inertia and the primary frequency modulation correction model of the PEMEL include:

[0143] Step 5.1) input the steady-state operating point power of the PEMEL and the system frequency change rate into the fuzzy controller for adjusting the virtual inertia coefficient, to obtain the upper correction amount or the lower correction amount of the virtual inertia coefficient;

[0144] input the steady-state operating point power of the PEMEL and the system frequency deviation into the fuzzy controller for adjusting the primary frequency modulation coefficient, to obtain the upper correction amount or the lower correction amount of the primary frequency modulation coefficient;

[0145] Step 5.2) based on the upper correction amount or the lower correction amount of the virtual inertia coefficient, calculate the virtual inertia coefficient of the PEMEL;

[0146] based on the upper correction amount or the lower correction amount of the primary frequency modulation coefficient, calculate the primary frequency modulation coefficient of the PEMEL;

[0147] The virtual inertia coefficient and the primary frequency modulation coefficient are as follows:

[0148] (18)

[0149] (19)

[0150] where f is frequency.

[0151] Example 10:

[0152] Referring to Figs. 1-3 , the adaptive frequency control method of the proton exchange membrane electrolyzer considering temperature-pressure-water influence, the technical content is the same as any one of examples 1-9, further, the input and output variables of the fuzzy controller are all divided into negative big NB, negative small NS, zero Z, positive small PS, and positive big PB fuzzy sets using triangular membership functions or trapezoidal membership functions;

[0153] The control rules of the fuzzy controller for adjusting the virtual inertia coefficient are as follows:

[0154] When the power of the steady-state operating point is large and the frequency change rate is large, the upper correction amount of the virtual inertia coefficient is moderate, and the lower correction amount is large;

[0155] When the power of the steady-state operating point is moderate and the frequency change rate is moderate, both the upper correction amount and the lower correction amount of the virtual inertia coefficient are moderate;

[0156] When the power of the steady-state operating point is small and the frequency change rate is large, the upper correction amount of the virtual inertia coefficient is large, and the lower correction amount is moderate;

[0157] The control rules of the fuzzy controller for adjusting the primary frequency modulation coefficient are as follows:

[0158] When the power of the steady-state operating point is large and the frequency deviation is large, the upper correction amount of the primary frequency modulation coefficient is moderate, and the lower correction amount is large; large, moderate, and small are all determined by fuzzy control theory.

[0159] When the power of the steady-state operating point is moderate and the frequency deviation is moderate, both the upper correction amount and the lower correction amount of the primary frequency modulation coefficient are moderate;

[0160] When the power of the steady-state operating point is small and the frequency deviation is large, the upper correction amount of the primary frequency modulation coefficient is large, and the lower correction amount is moderate.

[0161] Example 11:

[0162] The adaptive frequency control strategy of the PEMEL considering temperature-pressure-water influence, the steps include:

[0163] 1) Based on the dynamic operating characteristics of the PEMEL, a PEMEL dynamic model considering the coupling effects of temperature, pressure, and water content is constructed to provide an accurate model basis for the design of the frequency control strategy;

[0164] 2) Analyzing the frequency regulation performance of PEMEL at different steady state operating points;

[0165] 3) Analyzing the influence mechanism of temperature, pressure, and water content on the maximum hydrogen production power of PEMEL;

[0166] 4) Proposing a frequency regulation power compensation method for PEMEL under the influence of temperature, pressure, and water content;

[0167] 5) Based on the fuzzy control theory and the real-time state of the operating point of PEMEL, designing a virtual inertia and primary frequency regulation parameter adaptive setting mechanism for PEMEL, and researching the adaptive frequency regulation strategy of PEMEL.

[0168] PEMEL electrochemical model considering temperature-pressure-water content coupling effect: PEMEL terminal voltage The reversible voltage The voltage generated by the internal ohmic resistance The concentration difference overvoltage The double-layer voltage And The mathematical description can be expressed as:

[0169] (1)

[0170] The reversible voltage is related to the pressure and temperature inside the electrolytic cell, and its value can be expressed as:

[0171] (2)

[0172] In the above formula is the reference value of the reversible voltage, is the gas constant, is the electrolytic cell temperature, F is the Faraday constant, is the hydrogen partial pressure, is the oxygen partial pressure, is the water partial pressure in the anode / cathode chamber. Among them And can be obtained from the empirical formula:

[0173] (3)

[0174] (4)

[0175] The ohmic overvoltage is the voltage drop generated by the equivalent resistance inside the electrolytic cell, which can be expressed as:

[0176] (5)

[0177] In the above formula The resistance generated by other components such as electrodes, which has little effect and is taken as 0.01, The resistance generated by the proton transfer resistance, which plays a leading role. The above formula can be transformed into:

[0178] (6)

[0179] (7)

[0180] The above formula represents the thickness of the PEMEL membrane electrode, represents the conductivity of the membrane, represents the water content of the membrane.

[0181] The double-layer voltage of PEMEL is mainly generated by the movement of charges at the anode / cathode and electrolyte interface, which can be represented as:

[0182] (8)

[0183] (9)

[0184] The above formula and respectively represent the charge transfer coefficients of the anode and the cathode, and respectively represent the exchange current density of the anode and the cathode.

[0185] The concentration difference overvoltage is generated by the mass transfer limitation of the reactants in the electrode and the inability of the gas to be promptly removed from the electrode, which can be represented as:

[0186] (10)

[0187] where is the amount of transferred electrons, is the maximum current allowed by the PEMEL.

[0188] The dynamic physical model of PEMEL mainly includes the dynamic changes of temperature, pressure and water content, which directly affect the dynamic performance of the PEM electrolytic cell, so dynamic models need to be established respectively.

[0189] The internal temperature of PEMEL changes with the change of hydrogen production power, and its dynamic model is:

[0190] (11)

[0191] The above formula is the number of series and parallel connections of PEMEL monomers, is the coefficient of the thermodynamic model, which is taken as , For hydrogen production efficiency, and For temperature coefficient and heat loss coefficient, respectively , , For hydrogen production power, For ambient temperature, Reference temperature.

[0192] The internal pressure of PEMEL changes depending on the generation rate, discharge rate and thermodynamic state of the anode / cathode chamber. The dynamic model is as follows:

[0193] (12)

[0194] The above formula , and are the gas volumes of hydrogen, oxygen and water vapor, respectively, and are the hydrogen production and oxygen production rates, respectively, and are the hydrogen discharge and oxygen discharge rates, respectively, and are the water supply and consumption rates, respectively, and are the evaporation and condensation rates of water vapor.

[0195] The dynamic model of water content is as follows:

[0196] (13)

[0197] The above formula , and are the dynamic coefficient of water content, diffusion loss coefficient and evaporation loss coefficient, respectively, is the electro-osmotic drag coefficient, is the reference water content for normal operation of the membrane, is the water saturated vapor pressure.

[0198] The steady-state operating point of PEMEL is the key to determining its up-regulation and down-regulation frequency capabilities.

[0199] PEMEL is based on the preset steady-state operating point for bidirectional frequency regulation, and the frequency regulation capability of PEMEL at different steady-state operating points is very different. Therefore, it is urgent to clarify the frequency regulation performance of PEMEL at different steady-state operating points to provide theoretical support for the design of frequency regulation control strategy.

[0200] When PEMEL operates at low steady state point, the frequency modulation ability is stronger when the frequency fluctuates upward, and weaker when the frequency fluctuates downward; when PEMEL operates at high steady state point, the frequency modulation ability is weaker when the frequency fluctuates upward, and stronger when the frequency fluctuates downward.

[0201] Considering that the temperature, pressure and water content of PEMEL can affect the actual maximum operating power, based on the established PEMEL multi-physical coupling dynamic model, the frequency modulation power compensation sub-model of temperature, pressure and water content is proposed.

[0202] Temperature compensation term: Generally, the temperature rise of PEMEL will reduce the membrane resistance, resulting in the actual operating power rising. In this paper, the temperature is defined as rising from 60℃ to 80℃, and the power change range is +10%~15%. Based on the temperature dynamic model, the temperature compensation term of frequency modulation power is designed as:

[0203] (14)

[0204] The above formula is the frequency modulation power compensation amount caused by temperature change, is the temperature compensation coefficient, is the reference temperature.

[0205] Pressure compensation term: Generally, the pressure rise of PEMEL will improve the bubble and transmembrane mass transfer, resulting in the actual operating power being too high, thereby affecting the maximum hydrogen production power. In this paper, the pressure is defined as rising from 1bar to 3bar, and the power change range is +0~5%. Based on the pressure dynamic model, the pressure compensation term of frequency modulation power is designed as:

[0206] (15)

[0207] The above formula is the frequency modulation power compensation amount caused by pressure change, is the pressure compensation coefficient, is the reference pressure.

[0208] Water content compensation term: Properly increasing the membrane water content of PEMEL can improve the proton conductivity, and insufficient membrane water content will reduce the proton conductivity. In this paper, the water content is defined as rising from 14 to 22, and the power change range is +10%~20%. Based on the water content dynamic model, the water content compensation of frequency modulation power is designed as:

[0209] (16)

[0210] The above formula is the frequency modulation power compensation amount caused by water content change, is the water content compensation coefficient, is the reference water content.

[0211] The virtual inertia of PEMEL and the primary frequency modulation control technology are designed, and the mathematical model can be expressed as:

[0212] (17)

[0213] The above formula and respectively represent the virtual inertia and the primary frequency modulation coefficient, is the frequency deviation.

[0214] The temperature-pressure-water frequency modulation compensation term is integrated into the above control model, and the virtual inertia and the primary frequency modulation control correction model of PEMEL is obtained as:

[0215] (18)

[0216] The above formula is the sum of the virtual inertia and the primary frequency modulation power of the corrected PEMEL.

[0217] The fuzzy control technology is adopted to realize the adaptive online setting of the virtual inertia coefficient and the primary frequency modulation coefficient of PEMEL, so that the frequency modulation performance is in an optimal value under different conditions.

[0218] The input and output of the fuzzy controller: the virtual inertia mainly affects the frequency change rate of the system, so the fuzzy controller for adjusting the virtual inertia coefficient takes the power at the steady-state operating point of PEMEL and the frequency change rate of the system as the input, and outputs the upper correction amount and the lower correction amount of the virtual inertia coefficient. The primary frequency modulation mainly affects the maximum frequency deviation of the system, so the fuzzy controller for adjusting the primary frequency modulation coefficient takes the power at the steady-state operating point of PEMEL and the frequency deviation of the system as the input, and outputs the upper correction amount and the lower correction amount of the primary frequency modulation coefficient.

[0219] Membership function: the input and output variables both adopt triangular membership functions or trapezoidal membership functions, which are divided into five fuzzy sets of negative big (NB), negative small (NS), zero (Z), positive small (PS), and positive big (PB). The control rules are designed as follows:

[0220] Control rule 1: when the steady-state operating point power is large and the frequency change rate is large, the upper correction amount of the virtual inertia coefficient is moderate, and the lower correction amount is large; when the steady-state operating point power is moderate and the frequency change rate is moderate, the upper correction amount and the lower correction amount of the virtual inertia coefficient are both moderate; when the steady-state operating point power is small and the frequency change rate is large, the upper correction amount of the virtual inertia coefficient is large, and the lower correction amount is moderate.

[0221] Control rule 1: when the power of the steady-state operating point is large and the frequency deviation is large, the upper correction amount of the primary frequency modulation coefficient is moderate, and the lower correction amount is large; when the power of the steady-state operating point is moderate and the frequency deviation is moderate, the upper correction amount and the lower correction amount of the primary frequency modulation coefficient are both moderate; when the power of the steady-state operating point is small and the frequency deviation is large, the upper correction amount of the primary frequency modulation coefficient is large, and the lower correction amount is moderate.

[0222] Based on the above fuzzy control strategy, the virtual inertia coefficient and the primary frequency modulation coefficient expression of PEMEL are as follows:

[0223] (19)

[0224] (20)

[0225] Example 12:

[0226] The application of the PEMEL adaptive frequency modulation control strategy considering temperature-pressure-water influence is as follows:

[0227] In order to verify the feasibility and effectiveness of the proposed method, a revised IEEE-9 node test system is constructed in this patent, which includes synchronous generator station, new energy power generation station, PEM electrolyzer station and load composition.

[0228] When the system has frequency deviation and needs PEMEL to participate in frequency modulation, PEMEL will actively participate in frequency modulation, and according to the operating state of PEMEL, its optimal frequency modulation performance will be excavated, and the flow chart of PEMEL participating in system frequency modulation is as shown in Figs. 1-3 .

[0229] In order to verify the feasibility of PEMFL participating in frequency modulation and the effectiveness of the proposed adaptive frequency modulation control strategy, the following three cases are set for comparative analysis in this section.

[0230] Case 1: PEMEL does not participate in frequency modulation;

[0231] Case 2: PEMEL adopts constant coefficient virtual inertia and droop control to participate in frequency modulation;

[0232] Case 3: PEMEL adopts the control strategy proposed in this paper to participate in frequency modulation.

[0233] In this simulation, it is assumed that photovoltaic and wind turbine are running in maximum power point mode, the internal temperature, pressure and water content of PEMEL are considered as constants, the temperature, pressure and water supply subsystem of PEMEL do not participate in frequency modulation, and the steady-state operating point of PEMEL is set at a moderate position. The system load suddenly increases at t=6s and suddenly decreases at t=10s, and the simulation results under different cases are as shown in Fig. 1 and Fig. 2 .

[0234] From Fig. 3 And Fig. 2 It can be seen that the frequency fluctuation is the largest when the PEMEL is not involved in frequency regulation under Case 1 at t = 6 s. The PEMEL involved in frequency regulation by reducing the hydrogen production power under Case 2 and Case 3 can quickly reduce the frequency fluctuation. The frequency fluctuation is larger when the PEMEL is under Case 2 and smaller when the PEMEL is under Case 3. Similarly, the upward frequency regulation performance of the PEMEL under different cases is the same at t = 10 s. Therefore, according to Fig. 3 And Fig. 2 Fig. 3 The results show that the adaptive virtual inertia and primary frequency regulation control strategy proposed in this paper can fully exploit the optimal frequency regulation capability of the PEMEL.

Claims

1. An adaptive frequency modulation control method for a proton exchange membrane electrolyzer considering the effects of temperature, pressure, and water, characterized in that, Includes the following steps: Step 1) Based on the dynamic operating characteristics of the proton exchange membrane electrolyzer (PEMEL), construct a PEMEL dynamic model that considers the coupling effect of temperature, pressure and water content. Step 2) Determine the frequency modulation performance of PEMEL at different steady-state operating points; Step 3) Referencing PEMEL's frequency modulation performance at different steady-state operating points, construct a frequency modulation power compensation sub-model considering temperature-pressure-water content based on PEMEL's dynamic model; Step 4) Based on the frequency modulation power compensation sub-model, construct the virtual inertia and primary frequency modulation control correction model of PEMEL; Step 5) Based on fuzzy control theory and PEMEL's real-time running point status, adaptively tune the virtual inertia coefficient and the primary frequency modulation coefficient. Step 6) Based on the virtual inertia coefficient and the primary frequency modulation coefficient, calculate the primary frequency modulation power using PEMEL's virtual inertia and primary frequency modulation control correction model, thereby realizing PEMEL's adaptive frequency modulation control.

2. The adaptive frequency modulation control method for a proton exchange membrane electrolyzer considering the effects of temperature, pressure, and water, as described in claim 1, is characterized in that... PEMEL dynamic models that consider the coupling effects of temperature, pressure, and water content include the PEMEL electrochemical model that considers the coupling effects of temperature-pressure-water content and the PEMEL dynamic physical model that considers the coupling effects of temperature-pressure-water content.

3. The adaptive frequency modulation control method for a proton exchange membrane electrolyzer considering the effects of temperature, pressure, and water, as described in claim 2, is characterized in that... The PEMEL electrochemical model considering the temperature-pressure-water content coupling effect is shown below: （1） In the formula, , , , For PEMEL, the terminal voltage, reversible voltage, voltage generated by the internal ohmic resistance, and concentration difference overvoltage; , It is the double-layer voltage.

4. The adaptive frequency modulation control method for a proton exchange membrane electrolyzer considering the effects of temperature, pressure, and water, as described in claim 3, is characterized in that... Reversible voltage As shown below: （2） （3） （4） In the formula, This is the reversible voltage reference value. The gas constant is... The temperature of the electrolytic cell is given by , and F is the Faraday constant. This is the partial pressure of hydrogen gas. This is the partial pressure of oxygen. This refers to the partial pressure of the gas occupied by water in the cathode / anode chamber; Ohmic overvoltage is the voltage drop caused by the equivalent resistance inside the electrolytic cell, that is: （5） （6） In the formula, Indicates the thickness of the PEMEL film electrode. Indicates the conductivity of the membrane. Indicates the water content of the membrane; Indicates current density; The double-layer voltage of PEMEL is shown below: （7） （8） In the formula, and These represent the charge transfer coefficients of the anode and cathode, respectively. and These represent the exchange current densities at the anode and cathode, respectively. Concentration gradient overvoltage is shown below: （9） In the formula, To transfer the amount of electrons, This is the maximum current density allowed by PEMEL.

5. The adaptive frequency modulation control method for a proton exchange membrane electrolyzer considering the effects of temperature, pressure, and water, as described in claim 2, is characterized in that... The PEMEL dynamic physical model includes a dynamic model of internal temperature change, a dynamic model of pressure change, and a dynamic model of water content change. The internal temperature dynamic change model is shown below: （10） In the formula, This represents the number of PEMEL monomers connected in series or parallel. These are the coefficients of the thermodynamic model. For hydrogen production efficiency, and These are the temperature coefficient and the heat loss coefficient; For hydrogen production capacity, For ambient temperature, Reference temperature; t is time; The dynamic pressure change model is shown below: （11） In the formula, , and These are the gas volumes of hydrogen, oxygen, and water vapor, respectively. and These represent the rates of hydrogen production and oxygen production, respectively. and These represent the rates of hydrogen and oxygen expulsion, respectively. and These are the rates of water replenishment and water consumption, respectively. and These are the rates of water vapor evaporation and water vapor condensation, respectively. The dynamic change model of water content is shown below: （12） In the formula, , and These are the dynamic coefficient of water content, the diffusion loss coefficient, and the evaporation loss coefficient, respectively. This is the electroosmotic drag coefficient. The baseline water content for normal membrane operation. This is the saturated vapor pressure of water.

6. The adaptive frequency modulation control method for a proton exchange membrane electrolyzer considering the effects of temperature, pressure, and water, as described in claim 1, is characterized in that... When PEMEL is running at a low steady-state point, its frequency modulation capability is stronger when the frequency fluctuates upward than when it is running at a high steady-state point, and its frequency modulation capability is weaker when the frequency fluctuates downward than when it is running at a high steady-state point.

7. The adaptive frequency modulation control method for a proton exchange membrane electrolyzer considering the effects of temperature, pressure, and water, as described in claim 1, is characterized in that... The frequency modulation power compensation sub-model considering temperature-pressure-moisture content includes temperature compensation terms, pressure compensation terms, and moisture content compensation terms for frequency modulation power. The temperature compensation term for frequency modulation power is shown below: （13） In the formula, This is the frequency modulation power compensation amount caused by temperature changes. This is the temperature compensation coefficient. Reference temperature; The pressure compensation terms for frequency modulation power are shown below: （14） In the formula, This is the frequency modulation power compensation amount caused by pressure changes. This is the pressure compensation coefficient. As the reference pressure; The moisture content compensation term for frequency modulation power is shown below: （15） In the formula, This is the frequency modulation power compensation amount caused by changes in water content. This is the moisture content compensation coefficient. This is the baseline moisture content.

8. The adaptive frequency modulation control method for a proton exchange membrane electrolyzer considering the effects of temperature, pressure, and water, as described in claim 1, is characterized in that... The virtual inertia and primary frequency modulation control correction model of PEMEL are shown below: （16） （17） In the formula, and These represent the virtual inertia and the first-order frequency modulation coefficient, respectively. This is for frequency deviation; It is the sum of the virtual inertia corrected by PEMEL and the primary frequency modulation power.

9. The PEMEL virtual inertia and primary frequency modulation control technology according to claim 1, characterized in that, Step 5), which involves solving for the virtual inertia and primary frequency modulation control correction model of PEMEL based on fuzzy control theory and the real-time state of PEMEL's operating point, includes the following steps: Step 5.1) Input the PEMEL steady-state operating point power and the system frequency change rate into the fuzzy controller that adjusts the virtual inertia coefficient to obtain the upward correction amount of the virtual inertia coefficient. Or lower the correction amount ; The PEMEL steady-state operating point power and system frequency deviation are input to a fuzzy controller that adjusts the primary frequency modulation coefficient to obtain the upward correction amount of the primary frequency modulation coefficient. Or lower the correction amount ; Step 5.2) Upward correction based on virtual inertia coefficient Or lower the correction amount Calculate the virtual inertia coefficient of PEMEL; Upward correction based on primary frequency modulation coefficient Or lower the correction amount Calculate the primary frequency modulation coefficient of PEMEL; The virtual inertia coefficient and the primary frequency modulation coefficient are shown below: （18） （19） In the formula, f is the frequency.

10. The PEMEL virtual inertia and primary frequency modulation control technology according to claim 9, characterized in that, The input and output variables of the fuzzy controller are divided into fuzzy sets of negative large NB, negative small NS, zero Z, positive small PS, and positive large PB using triangular membership functions or trapezoidal membership functions. The control rules used by the fuzzy controller that adjusts the virtual inertia coefficient are as follows: When the steady-state operating point power is large and the frequency change rate is large, the upward correction of the virtual inertia coefficient is moderate, while the downward correction is large. When the steady-state operating point power and the rate of frequency change are moderate, the upward and downward corrections of the virtual inertia coefficient are both moderate. When the steady-state operating point power is small and the frequency change rate is large, the upward correction of the virtual inertia coefficient is large and the downward correction is moderate. The control rules used by the fuzzy controller for adjusting the primary frequency modulation coefficient are as follows: When the steady-state operating point power is large and the frequency deviation is large, the upper correction of the primary frequency regulation coefficient is moderate, while the lower correction is large. When the steady-state operating point power and frequency deviation are moderate, the upper and lower correction values ​​of the primary frequency regulation coefficient are both moderate. When the steady-state operating point power is small and the frequency deviation is large, the upward correction of the primary frequency regulation coefficient is large, while the downward correction is moderate.

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