Electro-hydrogen system optimization operation method considering dynamic characteristics of proton exchange membrane electrolytic cell

Abstract

The invention belongs to the technical field of electric power, and discloses an electricity-hydrogen system optimization operation method considering dynamic characteristics of a proton exchange membrane electrolytic bath, which is characterized by comprising the following steps: 1, carrying out improved modeling based on the dynamic characteristics of the proton exchange membrane electrolytic bath; 2, constructing an electricity-hydrogen comprehensive energy system optimization operation model considering the dynamic characteristics of the proton exchange membrane electrolytic cell; and 3, carrying out model conversion and solving. Compared with the prior art, the method has the main beneficial technical effects that high-quality consumption of redundant new energy is realized through the electrolytic cell, the carbon emission and the abandoned wind and light quantity of the system are reduced, and misjudgment of the operation state of the electricity-hydrogen comprehensive energy system can be avoided, so that low-carbon transformation of the energy system is promoted.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electric power, and particularly discloses a method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer. BACKGROUND

[0002] Global energy consumption is increasing, and fossil energy reserves are decreasing, which seriously threatens global energy security. In order to cope with the urgent challenge of climate change, it has become an urgent need to realize low-carbon transformation of the electric power energy system.

[0003] Hydrogen, as a new energy carrier, has flexibility and multifunctionality in the fields of power generation, chemical industry, metallurgy, transportation, etc., and plays an important role in global carbon emission reduction. However, the high cost of hydrogen produced by water electrolysis is still the main obstacle to its widespread application. Therefore, low-carbon electricity produced by electrolysis, such as hydrogen produced by water electrolysis of renewable energy, effectively solves this problem. Hydrogen can be used as a raw material for chemical production, and can be used in the hydrogenation process of oil refineries, or reacted with carbon, nitrogen and oxygen to synthesize compounds such as ammonia, methane and methanol. This provides a feasible way to utilize renewable energy, and also provides a new way for the green and low-carbon transformation of the electric power energy system.

[0004] Electrolyzers are key equipment for producing hydrogen, which can be divided into three categories, including proton exchange membrane electrolyzers, alkaline electrolyzers and solid oxide electrolyzers. Proton exchange membrane electrolyzers have the advantages of flexible operation and strong response capability, and are an ideal choice for renewable energy applications. However, it has been hindered by high cost, complex system and strict requirements for water purity. Alkaline electrolyzers are a well-developed water electrolysis technology and are widely used in industry. The main disadvantage of alkaline electrolyzers is low efficiency and long response time at partial load power. The applicability of solid oxide electrolyzers on an industrial scale has not been guaranteed. At present, for renewable energy hydrogen production systems, proton exchange membrane electrolyzers and alkaline electrolyzers are widely used in the hydrogen production industry. In practice, the use of proton exchange membrane electrolyzers and alkaline electrolyzers basically depends on technology and economy. From the technical point of view, the operating power of the proton exchange membrane electrolyzer is flexible, while the alkaline electrolyzer is limited by the minimum operating power. From the economic point of view, the investment cost of the alkaline electrolyzer is significantly lower than that of the proton exchange membrane electrolyzer.

[0005] In the optimization operation of integrated energy systems, the efficiency and energy consumption ratio of proton exchange membrane electrolyzers are usually fixed as constants. In fact, the efficiency of proton exchange membrane electrolyzers is usually related to electrochemical characteristics and operating power. Under certain operating conditions, the hydrogen production efficiency of electrolytic water can be reduced by 20%. When the power supply of proton exchange membrane electrolyzers is provided by intermittent and fluctuating renewable energy, this problem should be considered. Therefore, the optimization operation of integrated energy systems should consider the dynamic characteristics of proton exchange membrane electrolyzers, and a more accurate and detailed technical and economic analysis model should be established.

[0006] Currently, the existing operation strategy research of proton exchange membrane electrolyzers has highlighted the importance of efficiency variation, load range and start-stop characteristics. In theory, the efficiency of proton exchange membrane electrolyzers increases with the decrease of current density, which means that the lower the hydrogen production per kilogram, the lower the energy consumption. In addition, proton exchange membrane electrolyzers have an optimal operating range, usually at 25% to 100% of the nominal capacity, and cannot be operated below its lower limit or risk overload. This constraint can lead to frequent start-stop cycles, which has been widely discussed, and several rules for start-stop management of proton exchange membrane electrolyzers have been proposed. SUMMARY

[0007] Based on the above analysis, the present application focuses on the dynamic process of proton exchange membrane electrolyzers and conducts optimization operation research of electricity-hydrogen integrated energy systems. The influence of electrochemical characteristics of proton exchange membrane electrolyzers is simulated, a hydrogen production model is constructed, and the dynamic variation of hydrogen production efficiency is considered. On this basis, an optimization operation model of electricity-hydrogen integrated energy systems is constructed, and a corresponding model transformation method is proposed to optimize the operation strategy of the system.

[0008] The purpose of the present application is to disclose an electricity-hydrogen system optimization operation method considering the dynamic characteristics of proton exchange membrane electrolyzers, which is realized by adopting the following technical scheme.

[0009] An electricity-hydrogen system optimization operation method considering the dynamic characteristics of proton exchange membrane electrolyzers, characterized in that it comprises the following steps:

[0010] Step 1: Improved modeling based on the dynamic characteristics of proton exchange membrane electrolyzers;

[0011] Step 2: Construction of an electricity-hydrogen integrated energy system optimization operation model considering the dynamic characteristics of proton exchange membrane electrolyzers;

[0012] Step 3: Model transformation and solution.

[0013] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that in the first step, the hydrogen production amount of the proton exchange membrane electrolyzer depends on the start-stop state of the electrolyzer; when the proton exchange membrane electrolyzer is running, the hydrogen production amount is controlled by adjusting the current for electrolyzing water, and for each compartment in the electrolysis system, the polarization relationship between the open circuit voltage and the current density is expressed by a mathematical formula: (1), wherein F is the Faraday constant, T and R are temperature constant and universal gas constant, V0 is the reversible cell voltage, , , and are the charge transfer coefficient and exchange current density at each electrode, , and are the pressures of hydrogen, oxygen and water, is the equivalent resistance;

[0014] Generally, the parameters of each compartment are the same, and the of each compartment is equal, so the current density of each electrolysis system is equal, and according to the structure of the electrolyzer, the consumed renewable energy and the generated hydrogen are expressed as functions of and , as follows: (2), (3), wherein k1 and k2 are conversion coefficients, η is the Faraday efficiency, is the number of electrolyzers, is the membrane contact area;

[0015] On the basis of formula (1)-(3), further considering the start-stop state of the electrolyzer , the nonlinear relationship between and can be expressed as: (4),

[0016] In order to ensure the safe operation of the electrolyzer, needs to be limited to its upper limit and lower limit , as follows: (5),

[0017] As can be seen from the above formula, the hydrogen production efficiency of the proton exchange membrane electrolyzer is variable and is derived as: (6), wherein k3 and k4 are conversion coefficients, is the high heat value of hydrogen.

[0018] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that in the second step, the following sub-steps are included:

[0019] In the second step 2.1, the basic structure of the electricity-hydrogen integrated energy system includes the power grid, the electrolyzer, the hydrogen storage tank, the hydrogen fuel cell, the combined heat and power unit, the hydrogen pipeline, the thermal load, the electrochemical energy storage, the electrical load, the photovoltaic unit and the wind turbine unit.

[0020] In the second step 2.2, the objective function of the electricity-hydrogen integrated energy system optimization model is constructed as follows:

[0021] In the third step 2.3, the model constraints of the power grid, the hydrogen grid and the coupling unit include the power flow equation, the hydrogen energy storage tank operation constraint, the hydrogen fuel cell operation constraint, the hydrogen pipeline gas flow equation, the hydrogen network flow continuity equation, the electrochemical energy storage operation constraint, the combined heat and power unit operation constraint, the electricity-hydrogen integrated energy system power balance constraint, the node voltage and gas pressure constraint, and the branch transmission capacity constraint.

[0022] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that in the second step 2.1, the basic structure of the electricity-hydrogen integrated energy system includes the power grid, the electrolyzer, the hydrogen storage tank, the hydrogen fuel cell, the combined heat and power unit, the hydrogen pipeline, the thermal load, the electrochemical energy storage, the electrical load, the photovoltaic unit and the wind turbine unit.

[0023] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that in the second step 2.2, the objective function of the electricity-hydrogen integrated energy system optimization model is constructed as follows: (7), wherein c curt , c grid , c RDG , c trad respectively represent the wind and light punishment price, the electricity purchase price, the new energy on-grid electricity price and the carbon trading price, e car is the carbon emission factor.

[0024] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that in the third step 2.3, the model constraints of the power grid, the hydrogen grid and the coupling unit include the power flow equation, the hydrogen energy storage tank operation constraint, the hydrogen fuel cell operation constraint, the hydrogen pipeline gas flow equation, the hydrogen network flow continuity equation, the electrochemical energy storage operation constraint, the combined heat and power unit operation constraint, the electricity-hydrogen integrated energy system power balance constraint, the node voltage and gas pressure constraint, and the branch transmission capacity constraint.

[0025] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that the power flow equation is:

[0026] (8),

[0027] (9),

[0028] wherein P i and Q i are active power injection and reactive power injection at node i; U i and U j are voltage amplitudes of nodes i and j; θ i and θ j are voltage angles of nodes i and j; G ij and B ij are conductance and susceptance between nodes i and j; and N e is the total number of electrical nodes.

[0029] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that the hydrogen energy storage tank operation constraint is:

[0030] (10),

[0031] (11),

[0032] (12),

[0033] (13),

[0034] (14),

[0035] (15),

[0036] wherein HyS t is hydrogen mass stored by the hydrogen energy storage tank, m ch.t and m dic.t are hydrogen charging and discharging amounts, HyS min and HyS max are upper and lower limits of the hydrogen energy storage tank, α and Z HyS are initial state coefficients and hydrogen charging and discharging states of the hydrogen energy storage tank, ΔHyS max and ΔHyS min are hydrogen storage ramping limits, m HyS.min and m HyS.maxThe upper and lower limits of hydrogen charging and discharging for the hydrogen energy storage tank; formula (10) is the storage balance of the hydrogen energy storage tank, and formulas (11)-(15) represent the storage capacity limit and the uphill and downhill storage constraints for the hydrogen energy storage tank.

[0037] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that the hydrogen fuel cell operation constraints are:

[0038] (16),

[0039] (17),

[0040] (18),

[0041] In the formula, mHFC t, ηHFC t and PHFC t are the hydrogen consumption amount, energy conversion coefficient and electric energy output amount of the hydrogen fuel cell, and PHFC min and PHFC max are the upper and lower limits of the hydrogen consumption amount, and ΔPHFC max and ΔPHFC min are the uphill constraints of the fuel cell; formula (16) is the energy conversion process of the hydrogen fuel cell, and formulas (17)-(18) represent the capacity limit and the uphill and downhill constraints of the hydrogen fuel cell, respectively.

[0042] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that the hydrogen pipeline gas flow equation is: (19), in which, is the hydrogen flow rate of pipeline r; is the function symbol; is the pressure drop along pipeline r; i and j are the node numbers of the two ends of pipeline r; s ij is the symbol function for describing the flow direction of hydrogen in the pipeline; when p i > p j , s ij = 1; otherwise, s ij = -1; K r is the pipeline resistance coefficient r, which is represented as: (20), in which, D g is the inner diameter of the pipeline; L g is the length of the pipeline; T g is the average temperature of the gas; S is the specific gravity of the gas; Z a is the average compression factor of the gas; and C n is a constant related to the universal constant of the reference temperature, the reference pressure and the ideal gas.

[0043] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that a flow continuity equation of the hydrogen network is: (21), wherein A g is a node branch incidence matrix of the hydrogen network; f is a vector of hydrogen flow in each pipeline; G is hydrogen flow of each node, and is set as , A gas pressure drop matrix of the hydrogen pipeline is represented as: (22) in combination with the above equation, a pipeline flow equation of the hydrogen network is represented as: (23).

[0044] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that an electricity storage operation constraint is:

[0045] (24),

[0046] (25),

[0047] (26),

[0048] (27),

[0049] (28),

[0050] wherein SOC t , P ch.t and P dis.t are energy and charge-discharge power of the electricity storage, SOC min and SOC max are upper and lower limits of storage capacity of the electricity storage; P bat,min and P bat,max are upper and lower limits of charge-discharge power of the electricity storage; β and Z b； are initial state coefficients and charge-discharge states of the electricity storage; formula (24) describes a storage process of the electricity storage, formulas (25)-(26) represent state of charge constraints of the electricity storage, and formulas (27)-(28) represent charge-discharge power constraints of the electricity storage.

[0051] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that a combined heat and power unit operation constraint is:

[0052] (29),

[0053] (30), ​

[0054] (31),

[0055] where PCHP t, QCHP t and GCHP t are the power output, heat output and gas consumption of the combined heat and power, respectively; ηMT t is the power generation efficiency; η rec and λCo he are the heating coefficient of the bromine cooler and the flue gas recovery efficiency, respectively; ηMT L is the heat loss coefficient of the turbine; a MT , b MT , c MT and d MT are the linear model of the water turbine efficiency coefficient obtained by linear fitting polynomial.

[0056] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that the power balance constraint of the electricity-hydrogen comprehensive energy system is:

[0057] (32),

[0058] (33),

[0059] (34),

[0060] (35),

[0061] where P RDG.t and P cur.t are the active power generated and reduced by the renewable energy; Q RDG.t and QLoad t are the reactive power generated by the renewable energy and the reactive load demand, respectively; P grid.t and Q grid.t are the active and reactive power exchanged with the upper-level power grid; Hload t and PLoad t are the demand amounts of the heat load and the electric load.

[0062] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that the node voltage and gas pressure constraints are:

[0063] (36),

[0064] (37),

[0065] where U i.max and U i.min are the upper and lower limits of the amplitude of the node voltage; p i.max and p i.min are the upper and lower limits of the amplitude of the node gas pressure.

[0066] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that the branch transmission capacity constraint is:

[0067] (38),

[0068] (39),

[0069] wherein P ij.max and P ij.min are transmission capacities of the branch ij; f r.max and f r.min are transmission capacities of the pipeline r.

[0070] The method for optimizing operation of an electricity-hydrogen system considering dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that in the third step, for the constraint formulas (1)-(6) of the proton exchange membrane electrolyzer, the functional relationship between PPEM c.t and FPEM c.t is described as: when UPEM c.t=1, FPEM c.t is a monotonic nonlinear function of PPEM c.t, denoted as f PEM (PPEMc.t); otherwise, FPEM c.t is a linear function of PPEM c.t, which can be represented by a straight line; accordingly, the curve f PEM (PPEMc.t) is divided into N p linear segments within the feasible range of PPEM c.t, and (1)-(6) are converted into:

[0071] (40),

[0072] (41),

[0073] (42),

[0074] (43),

[0075] wherein PPEM c.k is the kth segmented point value within the feasible range of PPEM c.t; θ c.k.t and are continuous auxiliary variables and binary auxiliary variables, respectively;

[0076] Similarly, for the hydrogen pipeline gas flow equation, a segmented linearization method is adopted to convert it into:

[0077] (44),

[0078] (45),

[0079] (46),

[0080] (47),

[0081] (48),

[0082] wherein, is f r.t the kth segment point value in the feasible range; and δ k.t are continuous auxiliary variables and binary auxiliary variables, respectively;

[0083] For the power flow equation, considering two characteristics of the distribution network: 1) the node voltage amplitude tends to 1 p.u.; 2) the phase angle difference between the two ends of the line is small, the power flow equation is converted to:

[0084] (49),

[0085] (50).

[0086] The application has the following main beneficial technical effects: the redundant new energy high-quality consumption is realized through the electrolytic cell, the carbon emission and the abandoned wind and light amount of the system are reduced, the misjudgment of the operation state of the electric-hydrogen comprehensive energy system can be avoided, and thus the low-carbon transformation of the energy system is promoted. BRIEF DESCRIPTION OF DRAWINGS

[0087] Figure 1 is a structural schematic diagram of a proton exchange membrane electrolytic cell.

[0088] Figure 2 is a structural schematic diagram of an electric-hydrogen comprehensive energy system.

[0089] Figure 3 is a device rated capacity chart of an electric-hydrogen comprehensive energy system.

[0090] Figure 4 is a comparison chart of operation conditions of different scenarios, unit: ten thousand yuan.

[0091] Figure 5 is a comparison chart of hydrogen energy production conditions of different scenarios.

[0092] Figure 6 is a comparison of new energy consumption.

[0093] Figure 7 is a comparison of carbon emissions.

[0094] Figure 8 is a comparison chart of system operation costs under different capacities, unit: ten thousand yuan. DETAILED DESCRIPTION

[0095] For those skilled in the art to better understand and implement the patent, the specific embodiments are further described in detail in conjunction with the drawings in the specification.

[0096] See Figures 1 to 8 , a method for optimizing operation of an electricity-hydrogen system considering the dynamic characteristics of a proton exchange membrane electrolyzer, first, to make up for the modeling deficiency of the existing electricity-hydrogen comprehensive energy system operation model, the dynamic characteristics of the proton exchange membrane electrolyzer are considered based on the electrochemical characteristics of the proton exchange membrane electrolyzer; the model reflects the influence of different operating states of the electrolyzer on the hydrogen production efficiency, which is conducive to accurately simulating the operating conditions of the electrolyzer, realizing high-quality consumption of new energy through hydrogen production, and meeting the demand for hydrogen energy application; on this basis, further consider the heterogeneous energy conversion and safe operation constraints of the electricity-hydrogen comprehensive energy system, as well as the operation constraints of hydrogen fuel cells, various types of energy storage, and combined heat and power units, etc. To minimize the daily operation cost of the system, an electricity-hydrogen comprehensive energy system optimization operation model considering the dynamic characteristics of the proton exchange membrane electrolyzer is constructed; finally, based on the simulation example, the influence of the dynamic characteristics of the proton exchange membrane electrolyzer on the system operation is analyzed in detail, and the effectiveness of the proposed model and method is verified.

[0097] 1. Dynamic characteristics of proton exchange membrane electrolyzer

[0098] The structural diagram of the proton exchange membrane electrolyzer is shown in Figure 1 , Figure 2 It is illustrated that multiple parallel proton exchange membrane electrolyzers can realize new energy consumption and hydrogen production, and a single proton exchange membrane electrolyzer is composed of compressed series of current-controlled electrolysis chambers. Through continuous adjustment of current and discrete start-stop of proton exchange membrane electrolyzer, the proton exchange membrane electrolyzer can quickly respond to the change of new energy surplus power and realize flexible control of hydrogen production.

[0099] The hydrogen production of the proton exchange membrane electrolyzer depends on the start-stop state of the electrolyzer; when the proton exchange membrane electrolyzer is running, the hydrogen production can be controlled by adjusting the current of electrolytic water. For each compartment in the electrolysis system, the polarization relationship between the open circuit voltage and the current density can be expressed by a mathematical formula:

[0100] (1)

[0101] In the formula, F is the Faraday constant, T and R are temperature constant and universal gas constant, V0 is the reversible cell voltage, , , and are the charge transfer coefficients and exchange current densities at each electrode, respectively. , and are the pressure of hydrogen, oxygen and water, respectively, is the equivalent resistance.

[0102] Generally, the parameters of each compartment are the same. Therefore, the current density of each electrolysis system is equal, and the consumed renewable energy and the generated hydrogen can be expressed as a function of and , as follows.

[0103] (2)

[0104] (3)

[0105] where k1 and k2 are conversion coefficients, η is the Faraday efficiency, is the number of electrolytic cells, is the membrane contact area.

[0106] Based on equations (1)-(3), further considering the start-stop state of the electrolytic cell , the nonlinear relationship between and can be expressed as:

[0107] (4)

[0108] In order to ensure the safe operation of the electrolytic cell, needs to be limited to its upper limit and lower limit , as follows:

[0109] (5)

[0110] As can be seen from the above formula, the hydrogen production efficiency of the proton exchange membrane electrolytic cell is variable and can be derived as:

[0111] (6)

[0112] where k3 and k4 are conversion coefficients, is the high heat value of hydrogen.

[0113] 2. Optimal operation model of electricity-hydrogen integrated energy system

[0114] ​Based on the aforementioned proton exchange membrane electrolyzer model, considering the operation constraints of the electricity-hydrogen integrated energy system, the daily operation cost composed of carbon emission cost, energy consumption cost and wind curtailment penalty cost is taken as the target, and the electricity-hydrogen integrated energy system optimization operation model considering the dynamic characteristics of the proton exchange membrane electrolyzer is constructed.

[0115] 2.1, basic structure of electricity-hydrogen integrated energy system

[0116] Hydrogen is considered to be the most promising secondary energy, due to its friendly storage characteristics, can fully complement the power, and can play an important role in the future low-carbon society. For this purpose, an electricity-hydrogen integrated energy system is proposed, which can use electricity and hydrogen as energy carriers, and can accommodate high-penetration renewable energy.

[0117] Figure 2 The structure of the electricity-hydrogen integrated energy system in the present application is shown. It uses the carbon-free environmental protection characteristics of hydrogen energy to meet the demand of users for electricity, heating and hydrogen energy. Photovoltaic panels and wind turbines provide clean power supply, and hybrid energy storage is used to solve the imbalance between intermittent renewable energy and fluctuating load demand. The combination of batteries and hydrogen storage systems is used to manage short-term power fluctuations and long-term energy differences. Proton exchange membrane electrolyzers and hydrogen storage tanks are combined to provide hydrogen for hydrogen loads and improve hydrogen energy utilization efficiency. In addition, combined with cogeneration systems and gas boilers, hot water for users is provided.

[0118] 2.2, objective function

[0119] Considering the dynamic characteristics of the proton exchange membrane electrolyzer, the objective function of the electricity-hydrogen integrated energy system optimization operation model is constructed as follows:

[0120] (7)

[0121] In the formula, c curt , c grid , c RDG , c trad respectively represent the wind curtailment penalty price, the electricity purchase price, the new energy on-grid price and the carbon trading price, e car is the carbon emission factor.

[0122] 2.3, constraint conditions

[0123] At the level of constraints, the operation constraints of the electricity-hydrogen integrated energy system should follow the basic laws of power systems and hydrogen energy systems and the operation characteristics of each coupled unit, and the model constraints of the power grid, hydrogen grid and coupled units are established. Subsequently, the operation constraints of the electricity-hydrogen integrated energy system are established by integrating the above-mentioned sub-model constraints. Among them, the constraints of the proton exchange membrane electrolyzer have been described above, and the following describes the power flow equation, the operation constraints of the hydrogen storage tank, the operation constraints of the hydrogen fuel cell, the hydrogen pipeline gas flow equation, the flow continuity equation of the hydrogen network, the operation constraints of the electrochemical energy storage, the operation constraints of the cogeneration unit, the power balance constraints and the voltage and gas pressure safety operation constraints.

[0124] 1) Power flow equation

[0125] The power flow equation of the power grid reflects the relationship between power injection and voltage, which can be expressed as:

[0126] (8)

[0127] (9)

[0128] In the formula, P i and Q i are the active power injection and reactive power injection at node i, respectively; U i and U j are the voltage amplitudes of nodes i and j, respectively; θ i and θ j are the voltage angles of nodes i and j, respectively; G ij and B ij are the conductance and susceptance between nodes i and j, respectively; N e is the total number of electrical nodes.

[0129] 2) Hydrogen energy storage tank operation constraints

[0130] (10)

[0131] (11)

[0132] (12)

[0133] (13)

[0134] (14)

[0135] (15)

[0136] In the formula, HyS t is the mass of hydrogen stored in the hydrogen energy storage tank, m ch.t and m dic.tHyS min and HyS max are the upper and lower limits of hydrogen energy storage tank, a and Z HyS are the initial state coefficient and hydrogen charging and discharging state of hydrogen energy storage tank, AHYs max and AHYs min are the ramping limits of hydrogen storage, m HyS.min and m HyS.max are the upper and lower limits of hydrogen charging and discharging of hydrogen energy storage tank. Equation (10) is the storage balance of hydrogen energy storage tank, and equations (11)-(15) represent the storage capacity limits and upper and lower storage ramping constraints for hydrogen energy storage tank.

[0137] 3) Hydrogen fuel cell operation constraints

[0138] (16)

[0139] (17)

[0140] (18)

[0141] where mHFC t, ηHFC t and PHFC t are the hydrogen consumption, energy conversion coefficient and electrical energy output of hydrogen fuel cell, PHFC min and PHFC max are the upper and lower limits of hydrogen consumption, and ΔPHFC max and ΔPHFC min are the ramping constraints of fuel cell. Equation (16) is the energy conversion process of hydrogen fuel cell, and equations (17)-(18) represent the capacity limits and upper and lower ramping constraints of hydrogen fuel cell, respectively.

[0142] 4) Hydrogen pipeline flow equation

[0143] Considering the steady-state isothermal process of hydrogen flow in the hydrogen pipeline, the relationship between pipeline flow and pipeline pressure drop is represented as:

[0144] (19)

[0145] where f r is the hydrogen flow rate of pipeline r; is the function symbol; is the pressure drop along pipeline r; i and j are the node numbers of both ends of pipeline r; s ij is a symbol function used to describe the flow direction of hydrogen in the pipeline; when p i > p j , s ij = 1; otherwise, s ij = -1; K r is the pipeline resistance coefficient r, which can be represented as:

[0146] (20)

[0147] In the formula, D g L is the inner diameter of the pipe. g T is the length of the pipe; g Z represents the average temperature of the gas; S represents the specific gravity of the gas; Z represents the average temperature of the gas. a C is the gas average compressibility factor. n It is a constant related to the reference temperature, reference pressure, and the general constants of an ideal gas.

[0148] 5) Flow continuity equation for hydrogen networks

[0149] (twenty one)

[0150] In the formula, A g Let f be the node branch correlation matrix of the hydrogen network; f is the vector of hydrogen flow rate in each pipeline; and G is the hydrogen flow rate of each node.

[0151] set up , Pressure drop matrix of hydrogen pipeline It can be represented as:

[0152] (twenty two)

[0153] Combining the above equations, the flow equations for the hydrogen network can be expressed as:

[0154] (twenty three)

[0155] 6) Constraints on the operation of energy storage

[0156] (twenty four)

[0157] (25)

[0158] (26)

[0159] (27)

[0160] (28)

[0161] In the formula, SOC t P ch.t and P dis.t SOC (State of Charge) is the energy stored and the charging / discharging power of electrical energy storage. min and SOC max This represents the upper and lower limits of the energy storage capacity. P bat,min and P bat,maxare the upper and lower limits of the charging and discharging power of the electrical storage. β and Z bat are the initial state coefficient and state of charge of the electrical storage. Equations (24) describe the storage process of the electrical storage, equations (25)-(26) represent the state of charge constraints of the electrical storage, and equations (27)-(28) represent the charging and discharging power constraints of the electrical storage.

[0162] 7) Combined heat and power unit operation constraints

[0163] The combined heat and power unit consists of a micro-combustor and a bromine cooler. The high-temperature steam discharged by the micro-combustor provides heating and hot water through the bromine cooler, achieving cascade utilization of different thermal energy qualities and reducing carbon dioxide and harmful gas emissions. The model of the combined heat and power unit is as follows:

[0164] (29)

[0165] (30)

[0166] (31)

[0167] where PCHP t, QCHP t, and GCHP t are the electrical power output, thermal output, and gas consumption of the combined heat and power, respectively; ηMT t is the power generation efficiency; η rec and λCo he are the heating coefficient and flue gas recovery efficiency of the bromine cooler, respectively; ηMT L is the heat loss coefficient of the turbine; a MT , b MT , c MT , and d MT are the linear models of the turbine efficiency coefficient obtained by linear fitting polynomials.

[0168] 8) Power balance constraints of the integrated electricity-hydrogen energy system

[0169] (32)

[0170] (33)

[0171] (34)

[0172] (35)

[0173] where P RDG.t and P cur.t are the active power generated and curtailed by the renewable energy source. Q RDG.t and QLoad t are the reactive power generated by the renewable energy source and the reactive load demand, respectively. P grid.t and Q grid.tThese represent the active and reactive power exchanged with the upstream power grid, respectively. Hload t and PLoad t represent the demand for heat load and electrical load, respectively.

[0174] 9) Node voltage and air pressure constraints

[0175] (36)

[0176] (37)

[0177] In the formula, U i.max and U i.min These are the upper and lower limits of the node voltage amplitude, respectively; p i.max and p i.min These represent the upper and lower limits of the nodal pressure amplitude, respectively.

[0178] 10) Tributary transmission capacity constraints

[0179] (38)

[0180] (39)

[0181] In the formula, P ij.max and P ij.min These represent the transmission capacities of branch ij, respectively; f r.max and f r.min These represent the transmission capacity of pipe r.

[0182] 3. Model Conversion and Solution

[0183] The proton exchange membrane electrolyzer constraint formulas (1)-(6), the power flow equation formulas (8)-(9), and the hydrogen pipeline gas flow equation formula (19) in the above model are all mixed integer nonlinear constraints, which are difficult to solve directly. Therefore, this application proposes a linearization transformation method for the model, which transforms the above model into a mixed integer linear programming model.

[0184] For the constraint formulas (1)-(6) of the proton exchange membrane electrolyzer, the functional relationship between PPEM ct and FPEM ct can be described as follows: when UPEM ct=1, FPEM ct is a monotonically nonlinear function of PPEM ct, denoted as f PEM (PPEM ct); otherwise, F PEM ct is a linear function of P PEM ct and can be represented by a straight line. Based on this, we will define the curve f PEM (P PEMc.t) is divided into N within the feasible range of P PEM ct. p A linear segment, transforming (1)-(6) into:

[0185] (40)

[0186] (41)

[0187] (42)

[0188] (43)

[0189] In the formula, PPEM ck is the k-th segment point value within the feasible range of PPEM ct. θ c.k.t and These are continuous auxiliary variables and binary auxiliary variables, respectively.

[0190] Similarly, the gas flow equation for a hydrogen pipeline can be transformed into the following using a piecewise linearization method:

[0191] (44)

[0192] (45)

[0193] (46)

[0194] (47)

[0195] (48)

[0196] In the formula, f r.t The value of the kth segment point within the feasible range. and δ k.t These are continuous auxiliary variables and binary auxiliary variables, respectively.

[0197] For the power flow equations, considering two characteristics of the distribution network: 1) the node voltage magnitudes approach 1 p.u.; 2) the phase angle difference between the two ends of the line is very small, the power flow equations can be transformed into:

[0198] (49)

[0199] (50).

[0200] 4. Case Analysis

[0201] 4.1 Simulation Case Settings

[0202] This application conducts simulation analysis on an integrated electric-hydrogen energy system consisting of a 24-node power system and a 20-node hydrogen transmission system, designs three optimized operation strategies, and verifies the effectiveness of the proposed optimized operation strategy for the integrated electric-hydrogen energy system that considers the dynamic characteristics of the proton exchange membrane electrolyzer.

[0203] Scenario 1: The hydrogen production efficiency of the proton exchange membrane electrolyzer is set as a constant value without considering the dynamic characteristics of the proton exchange membrane electrolyzer, and the operation strategy of the electricity-hydrogen integrated energy system is formulated.

[0204] Scenario 2: The proton exchange membrane electrolyzer is set to have sufficient flexibility to start and stop at any time without considering the interval range of the operating power of the proton exchange membrane electrolyzer.

[0205] Scenario 3: Based on the model proposed in this application, the dynamic characteristics of the proton exchange membrane electrolyzer are considered, and the operation strategy of the electricity-hydrogen integrated energy system is formulated.

[0206] Figure 3 The device configuration of the electricity-hydrogen integrated energy system is shown, and the fluctuation of new energy and load is referred to the prior art. Other technical and economic parameters are detailed in the prior art. According to scenarios 1-3, the operation strategy of the electricity-hydrogen integrated energy system is formulated, Figure 4 The economic results of the schemes are compared. Figure 5 The hydrogen production and power consumption under different proton exchange membrane electrolyzer models are compared. Figure 6 、 Figure 7 The system carbon emissions and new energy consumption under different scenarios are compared, Figure 8 The sensitivity analysis of the influence of the proton exchange membrane electrolyzer capacity on the system operation cost is carried out.

[0207] 4.2, comparative analysis of simulation results

[0208] 1) Economic analysis

[0209] Figure 4 The operation economic results of scenarios 1-3 are shown. As can be seen, in scenario 1, the cost of curtailed wind and light, the cost of purchasing electricity, and the cost of carbon emissions of the electricity-hydrogen integrated energy system are much higher than those in scenarios 2-3, which ultimately leads to the worst economic performance of scenario 1. This indicates that ignoring the dynamic characteristics of the proton exchange membrane electrolyzer will result in serious curtailment of wind and light in the integrated energy system, which cannot achieve optimal consumption of new energy, and thus deteriorates the economic performance of the system. Compared with scenario 3, the total operation cost of scenario 2 is reduced by 5.63%, and the cost of curtailed wind and light, carbon emissions, and purchasing electricity is also reduced compared with scenario 3. This is because scenario 2 overestimates the flexibility of the proton exchange membrane electrolyzer, which leads to misjudgment of the new energy consumption and carbon emissions of the system, and thus affects the operation performance of the system. Scenario 3 considers the dynamic characteristics of the proton exchange membrane electrolyzer and can more accurately model the hydrogen production process, so it avoids the misjudgment of the amount of curtailed wind and light and carbon emissions, and achieves optimal consumption of new energy. This shows that considering the dynamic characteristics of the proton exchange membrane electrolyzer is beneficial to accurately evaluate the operation state of the system.

[0210] 2) Hydrogen production status analysis

[0211] Figure 5 The hydrogen production performance of different proton exchange membrane electrolyzer models was compared. Figure 5 As can be seen, although Scenario 1 consumes more electrical energy, its hydrogen production is far less than that of Scenario 2-3. This is because in Scenario 1, the dynamic characteristics of the proton exchange membrane electrolyzer are ignored, resulting in an inaccurate simulation of the relationship between hydrogen production power consumption and hydrogen production, leading to misjudgment of the electrolyzer's operating state and an inaccurate simulation of the system's hydrogen production. Compared to Scenario 2-3, Scenario 2 achieves maximized hydrogen production. This is because Scenario 2 assumes that the electrolyzer has ample flexibility, enabling flexible hydrogen production. However, in reality, the electrolyzer's operation is affected by its start-up and shutdown states, electrochemical characteristics, etc., making flexible start-up and shutdown impossible under all operating conditions. Scenario 3 considers the dynamic characteristics of the proton exchange membrane electrolyzer, allowing for precise modeling of the hydrogen production process, thus enabling accurate modeling of the relationship between hydrogen production and power consumption.

[0212] Figure 6 and Figure 7 The figures illustrate the renewable energy consumption and carbon emissions under different scenarios. As shown, Scenario 1, lacking the dynamic characteristics of the proton exchange membrane electrolyzer, increases both renewable energy consumption and carbon emissions. Scenario 2 overestimates the electrolyzer's flexibility, misjudging renewable energy consumption and carbon emissions, and overestimating the system's low-carbon operating performance. Scenario 3 considers the dynamic characteristics of the proton exchange membrane electrolyzer, avoiding misjudgments in renewable energy consumption and carbon emissions. This demonstrates that considering the dynamic characteristics of the proton exchange membrane electrolyzer is beneficial for improving the low-carbon operating performance of the electricity-hydrogen integrated energy system and avoiding misjudgments in renewable energy consumption and carbon emissions.

[0213] 4.3 Analysis of the impact of proton exchange membrane electrolyzer capacity on operating conditions

[0214] Figure 8 The total operating costs of the system were compared under different electrolyzer capacities. It is evident that, for any scenario, the total system cost gradually decreases with increasing capacity. This is because increasing the electrolyzer capacity increases hydrogen production, thereby promoting renewable energy consumption, reducing system carbon emissions, and improving the system's operational economics. Furthermore, compared to scenario 3, the total operating cost deviation in scenarios 1-2 gradually increases. This is because scenarios 1-2 do not accurately simulate the dynamic characteristics of the proton exchange membrane electrolyzer. As the electrolyzer capacity increases, the hydrogen production also increases, leading to more serious misjudgments in the hydrogen production process. Ultimately, this results in significant misjudgments of the system's renewable energy consumption, carbon emissions, and wind and solar power curtailment, leading to a more severe deterioration in operating costs.

[0215] The application considers the dynamic characteristics of the proton exchange membrane electrolyzer, and establishes an operation method of an electricity-hydrogen integrated energy system considering the dynamic characteristics of the proton exchange membrane electrolyzer. The redundant new energy is high-quality consumed through the electrolyzer, and the carbon emission and the abandoned wind and light amount of the system are reduced. The simulation results of the calculation example verify the effectiveness of the proposed model and method, analyzes the important role of considering the dynamic characteristics of the proton exchange membrane electrolyzer in reducing the system operation cost and improving the renewable energy consumption, and compares and analyzes the system operation under different electrolyzer models. Considering the dynamic characteristics of the proton exchange membrane electrolyzer, the operation state of the electricity-hydrogen integrated energy system can be avoided to be misjudged, so as to promote the low-carbon transformation of the energy system.

[0216] The application has the following main beneficial technical effects: the redundant new energy is high-quality consumed through the electrolyzer, the carbon emission and the abandoned wind and light amount of the system are reduced, and the operation state of the electricity-hydrogen integrated energy system can be avoided to be misjudged, so as to promote the low-carbon transformation of the energy system.

[0217] The above-mentioned embodiments are only preferred technical solutions of the application, and should not be regarded as a limitation of the application. The protection scope of the application should be based on the technical solutions recited in the claims, and the equivalent replacement solutions of the technical features recited in the claims are within the protection scope. That is, the equivalent replacement improvement within this range is also within the protection scope of the application.

Claims

1. A method for optimizing the operation of an electro-hydrogen system considering the dynamic characteristics of a proton exchange membrane electrolyzer, characterized in that... It includes the following steps: Step 1: Improve the modeling based on the dynamic characteristics of the proton exchange membrane electrolyzer; Step 2: Construct an optimized operation model for the integrated electric-hydrogen energy system that takes into account the dynamic characteristics of the proton exchange membrane electrolyzer. Step 3: Perform model transformation and solve the problem.

2. The method for optimizing the operation of an electro-hydrogen system considering the dynamic characteristics of a proton exchange membrane electrolyzer according to claim 1, characterized in that... Step 2 includes the following sub-steps: Step 2.1: Construct the basic structure of an integrated electric-hydrogen energy system; Step 2.2: Construct the objective function of the optimized operation model of the electric-hydrogen integrated energy system; Step 2.3: Establish model constraints for the power grid, hydrogen grid, and coupling units.

3. The method for optimizing the operation of an electro-hydrogen system considering the dynamic characteristics of a proton exchange membrane electrolyzer according to claim 2, characterized in that... In step 2.1, the basic structure of the integrated electric-hydrogen energy system includes a power grid, an electrolyzer, a hydrogen storage tank, a hydrogen fuel cell, a combined heat and power (CHP) system, a hydrogen pipeline, a heat load, electrochemical energy storage, an electrical load, a photovoltaic (PV) generator, and a wind turbine. The power grid, electrolyzer, hydrogen storage tank, hydrogen fuel cell, CHP system, hydrogen pipeline, heat load, electrochemical energy storage, electrical load, PV generator, and wind turbine. The PV generator, wind turbine, and electrochemical energy storage output electricity to the power grid, which supplies electricity to the electrolyzer, electrochemical energy storage, and electrical load. The gas produced by the electrolyzer is sent to the hydrogen storage tank, then to the hydrogen fuel cell, CHP system, and hydrogen pipeline. The hydrogen pipeline further sends the gas to the CHP system, and the heat generated by the CHP system is transferred to the heat load.

4. The method for optimizing the operation of an electro-hydrogen system considering the dynamic characteristics of a proton exchange membrane electrolyzer according to claim 2, characterized in that... In step 2.2, the objective function for constructing the optimized operation model of the electric-hydrogen integrated energy system is as follows: In the formula, c curt c grid c RDG c trad These represent the penalty price for curtailing wind and solar power, the electricity purchase price, the on-grid price for renewable energy, and the carbon trading price, respectively. car It is a carbon emission factor.

5. The method for optimizing the operation of an electro-hydrogen system considering the dynamic characteristics of a proton exchange membrane electrolyzer according to claim 2, characterized in that... In step 2.3, the model constraints for the power grid, hydrogen grid, and coupling units include: power flow equations, operating constraints for hydrogen storage tanks, operating constraints for hydrogen fuel cells, hydrogen pipeline gas flow equations, flow continuity equations for the hydrogen network, operating constraints for electric energy storage, operating constraints for combined heat and power (CHP) units, power balance constraints for the integrated electric-hydrogen energy system, node voltage and pressure constraints, and branch transmission capacity constraints.

6. The method for optimizing the operation of an electro-hydrogen system considering the dynamic characteristics of a proton exchange membrane electrolyzer according to claim 1, characterized in that... In step 3, the constraint formula for the proton exchange membrane electrolyzer is transformed, the gas flow equation for the hydrogen pipeline is transformed, and the tidal flow equation is transformed.

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