An improved method for optimizing dispatch of a comprehensive energy system considering fuel cell cogeneration

Abstract

The application discloses an improved method for optimizing and scheduling a comprehensive energy system considering fuel cell combined heat and power, comprising the following steps: 1) obtaining basic parameters of the comprehensive energy system; 2) establishing a device model of the comprehensive energy system; 3) establishing an optimization scheduling model of the comprehensive energy system considering fuel cell combined heat and power; 4) linearizing non-linear constraints in the optimization scheduling model of the comprehensive energy system to obtain an optimal scheduling model of the comprehensive energy system; and 5) solving the optimal scheduling model of the comprehensive energy system to obtain an optimization scheduling scheme of the comprehensive energy system considering fuel cell combined heat and power. The method can improve the heat production efficiency of SOFC in a period with high heat load and low electricity price, and can increase the power generation efficiency in a period with high electricity price.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of integrated energy system optimization scheduling, and particularly relates to an improved method for integrated energy system optimization scheduling considering fuel cell combined heat and power. BACKGROUND

[0002] With the rapid development of economy, energy shortage and environmental pollution problems are increasingly prominent, and vigorously developing and constructing integrated energy systems (IES) that integrate multiple heterogeneous energies, realize the mutual coordination, comprehensive utilization and mutual aid of different energies will become the development trend of future energy systems. The integrated energy system can break down the industry barriers of electricity, gas, heat and other energy systems, realize the interconnection and interconnection of multiple energies, and has important significance for improving social energy utilization efficiency, promoting large-scale development of renewable energy and ensuring energy supply security.

[0003] Under the background of the prominent global energy security problem and the serious environmental pollution problem, vigorously developing wind power, solar power, hydropower and other renewable energy and realizing the renewable energy transformation of energy production is an important way for China and even the world to achieve sustainable development of energy and economy. In recent years, renewable energy has developed rapidly, and the installed capacity has been increasing. However, the randomness, volatility and anti-peaking characteristics of renewable energy lead to serious curtailment of wind and light, causing a lot of waste of renewable energy. How to solve the problem of curtailment of wind and light and improve the renewable energy consumption rate has become an important research topic. The power to gas (P2G) technology can convert excess electricity into hydrogen or natural gas. Electricity cannot be stored on a large scale, but hydrogen and natural gas can be stored for a long time and on a large scale. Therefore, P2G can promote wind power consumption and realize "high production and low storage" arbitrage, and is considered to be an effective way to improve the renewable energy consumption rate.

[0004] On the other hand, improving the power generation efficiency of the power generation unit is an important means to improve the energy conversion efficiency of the energy system. Among the numerous power generation devices, fuel cells (FC) can directly convert the chemical energy of fuel into electrical energy, have the advantages of high power generation efficiency, low pollution, high specific energy, low noise and easy construction, and are hailed as the fourth generation of power generation technology after water, fire, and nuclear power. The power generation efficiency of fuel cells can reach 40% to 60%, and if the waste heat generated during power generation is collected, the combined heat and power efficiency will be more than 80%. P2G includes two steps of water electrolysis to produce hydrogen and hydrogen methanation, and the efficiency of electric hydrogen production can reach 80%, but due to the energy loss in the hydrogen methanation process, the overall efficiency of P2G is only 45% to 65%, therefore, preferentially using hydrogen produced by the P2G hydrogen production link can reduce the energy loss caused by the P2G cascade conversion. In addition to the characteristics of high efficiency and low pollution, fuel cells also have the advantage of wide fuel range, and hydrogen, methane, biogas, methanol, etc. can be used as fuel for fuel cells. Therefore, introducing fuel cells into the integrated energy system not only improves the energy conversion efficiency of the power generation unit of the system, but also promotes the high-grade utilization of hydrogen energy and more efficient utilization of excess renewable energy.

[0005] There are existing literatures considering the combined heat and power of fuel cells in the optimal scheduling of integrated energy systems. At present, the fuel cell combined heat and power models mainly fall into four categories: the first category is the combined heat and power model constructed according to the electrochemical reaction principle of fuel cells without considering fuel utilization; the second category is the combined heat and power model constructed according to the electrochemical reaction principle of fuel cells considering fuel utilization; the third category is the combined heat and power model obtained by data fitting of the measured electric and thermal power of fuel cells; and the fourth category is the combined heat and power model simplifying the electric and thermal efficiency of fuel cells as a constant. Although the second category of model considers the fuel utilization of fuel cells, it sets the fuel utilization as a fixed value when performing optimal scheduling of integrated energy systems, without considering the fuel utilization as a decision variable. In fact, the gas consumption and fuel utilization will both affect the electric and thermal output power of fuel cells, and the steady-state control of fuel utilization can be achieved by adjusting the fuel valve, and adjusting the fuel utilization is also one of the strategies to change the operating conditions of the fuel cell combined heat and power system. The electric and thermal power of fuel cells are coupled with each other, and the existing researches setting the fuel utilization as a fixed value result in only being able to change the electric and thermal output of fuel cells by adjusting the gas consumption, reducing the operating flexibility of fuel cells. Therefore, considering the fuel utilization as a decision variable and optimizing its control can improve the operating flexibility of fuel cells, and further reduce the operating cost of the integrated energy system.

[0006] In summary, in order to improve the consumption level of renewable energy and reduce the operating cost of the integrated energy system, it is necessary to consider the optimal control of the fuel utilization of fuel cells when performing optimal scheduling of the integrated energy system considering the combined heat and power of fuel cells. SUMMARY

[0007] The purpose of the present application is to provide an improved method for optimizing the scheduling of a comprehensive energy system taking into account the cogeneration of a fuel cell, comprising the following steps:

[0008] 1) Obtain the basic parameters of the comprehensive energy system.

[0009] Further, the basic parameters of the comprehensive energy system include the purchase and sale of electricity prices, natural gas prices, solid oxide fuel cell parameters, battery parameters, heat storage tank parameters, gas turbine parameters, gas boiler parameters, electric refrigerator parameters, photovoltaic unit output prediction values, electric load prediction values, thermal load prediction values, cold load prediction values.

[0010] 2) Establish the device model of the comprehensive energy system.

[0011] Further, the device model of the comprehensive energy system includes a cogeneration model of a solid oxide fuel cell, a gas turbine model, a gas boiler model, an electric boiler model, an electric refrigerator model, a battery model, a heat storage tank model.

[0012] The cogeneration model of the solid oxide fuel cell includes a power generation model of the solid oxide fuel cell and a heat generation model of the solid oxide fuel cell.

[0013] The power generation model of the solid oxide fuel cell is shown in Equations (1) - (10) respectively, i.e.:

[0014]

[0015] In the formula: parameter K r = 1 / (4F); F is the Faraday constant; I t is the current in a single solid oxide fuel cell during the period t; is the molar flow of hydrogen and oxygen consumed in a single solid oxide fuel cell during the period t, respectively; is the molar flow of water vapor generated in a single solid oxide fuel cell during the period t.

[0016]

[0017] In the formula: is the pressure of hydrogen, oxygen and water vapor in a single solid oxide fuel cell; is the molar flow of hydrogen input into a single solid oxide fuel cell; is the molar constant of hydrogen, oxygen and water vapor; r H-O is the ratio of hydrogen flow to oxygen flow.

[0018]

[0019] wherein: u t is the fuel utilization rate;

[0020]

[0021] wherein: q sofc,t is the natural gas flow rate into the solid oxide fuel cell; N1 is the number of series-connected single cells in the cell stack; N2 is the number of parallel-connected columns of the cell stack;

[0022] U sofc,t = N1(E nernst,t -U act,t -U con,t -U ohm,t ) (5)

[0023] wherein: E nernst,t is the Nernst reversible potential of a single solid oxide fuel cell; U act,t , U con,t , U ohm,t are the active polarization voltage, the concentration polarization voltage and the ohmic loss voltage of a single solid oxide fuel cell, respectively; U sofc,t is the output voltage of the solid oxide fuel cell;

[0024]

[0025] wherein: E0 is the standard potential; R is the universal gas constant; T is the working temperature of the fuel cell; E nernst,t is the Nernst reversible potential;

[0026]

[0027] wherein: I0 is the exchange current; U act,t is the active polarization voltage;

[0028]

[0029] wherein: I L is the limiting current; U con,t is the concentration polarization voltage;

[0030] U ohm,t = rI t (9)

[0031] wherein: r is the resistance of a single solid oxide fuel cell; U ohm,t is the ohmic loss voltage;

[0032] P sofc,t = N1N2(E nernst,t -U act,t -U con,t -Uohm,t )I t ×10 -3 (10)

[0033] In the formula: P sofc,t This refers to the electrical power output of a solid oxide fuel cell.

[0034] The heat generation models for solid oxide fuel cells are shown in equations (11)-(17), namely:

[0035]

[0036] In the formula: Q gen,sofc,t Q represents the total thermal power generated by the solid oxide fuel cell stack. re,t The heat power required for the methane steam reforming reaction; η gas This represents the proportion of heat carried away by the gas in the fuel cell stack. The thermal power required to preheat natural gas; Q pre,air,t The thermal power required to preheat the air; Q is the thermal power required for preheating water; ab,t Q represents the thermal power generated by hydrogen combustion in the afterburner; sofc,t The thermal power output of a solid oxide fuel cell;

[0037] Q gen,sofc,t =-4ΔH1u t q sofc,t -P sofc,t (12)

[0038] In the formula: ΔH1 is the enthalpy change when hydrogen and oxygen undergo an electrochemical reaction in the battery stack; Q gen,sofc,t This represents the total thermal power generated by the battery stack.

[0039]

[0040] In the formula: This refers to the specific heat capacity of natural gas. The molar mass of natural gas; This refers to the initial temperature of the natural gas. This is the preheating temperature of natural gas; For the efficiency of the natural gas preheater; The thermal power required to preheat natural gas;

[0041]

[0042] In the formula: C air M is the specific heat capacity of air; air T is the molar mass of air; air,0 T represents the initial air temperature. airPreheating temperature of air; ε air Efficiency of air preheater; Q pre,air,t Heat power required for preheating air;

[0043]

[0044] wherein: Specific heat capacity of liquid water; Specific heat capacity of water vapor; Molar mass of water; Latent heat of vaporization of water; Initial temperature of water; Preheating temperature of water; Efficiency of water preheater; Heat power required for preheating water;

[0045]

[0046] wherein: η ab Efficiency of afterburner; Low calorific value of hydrogen; Q ab,t Heat power generated by hydrogen combustion in afterburner;

[0047] Q re,t = ΔH2q sofc,t (17)

[0048] wherein: ΔH2 is enthalpy change of steam methane reforming reaction; Q re,t Heat power required for steam methane reforming reaction;

[0049] Gas turbine model is shown as follows:

[0050]

[0051] wherein: P gt,t Power generation of gas turbine; q gt,t Natural gas flow consumed by gas turbine; Calorific value of natural gas; η gt Power generation efficiency of gas turbine;

[0052] Gas boiler model is shown as follows:

[0053]

[0054] wherein: Q gb,t Heat generation of gas boiler; q gb,t Natural gas flow consumed by gas boiler; η gb Efficiency of gas boiler;

[0055] The electric boiler model is shown as follows:

[0056] Q eb,t = P eb,t η eb (20)

[0057] In the formula: Q eb,t is the heating power of the electric boiler; P eb,t is the power consumption of the electric boiler; η eb is the efficiency of the electric boiler;

[0058] The electric refrigerator model is shown as follows:

[0059] Q ec,t = P ec,t C ec (21)

[0060] In the formula: Q ec,t is the refrigeration power of the electric refrigerator; P ec,t is the power consumption of the electric refrigerator; C ec is the energy efficiency ratio of the electric refrigerator;

[0061] The battery model is shown as follows:

[0062]

[0063] In the formula: E bat,t and E bat,t-1 are the electric energy stored by the battery at time t and time t-1, respectively; P bat,cha,t and P bat,dis,t are the charging power and discharging power of the battery, respectively; σ bat , η bat,cha , and η bat,dis are the self-discharge rate, charging efficiency, and discharging efficiency of the battery, respectively; Δt is the duration of the time period;

[0064] The heat storage tank model is shown as follows:

[0065]

[0066] In the formula: E tes,t and E tes,t-1 are the thermal energy stored by the heat storage tank at time t and time t-1, respectively; Q tes,cha,t and Q tes,dis,t are the heat storage power and heat release power of the heat storage tank, respectively; σ tes , η tes,cha , and η tes,dis are the self-heat release rate, heat storage efficiency, and heat release efficiency of the heat storage tank, respectively.

[0067] 3) Establish an optimal scheduling model of a comprehensive energy system considering fuel cell combined heat and power.

[0068] Further, the objective function of the optimization scheduling model of the integrated energy system considering fuel cell cogeneration is as follows:

[0069]

[0070] In the formula, C IES is the total operation cost of the integrated energy system; C g,t , C e,t and C om,t are the gas purchase cost, electricity purchase cost and operation and maintenance cost of the integrated energy system respectively; T is the scheduling period.

[0071] Among them, the gas purchase cost C g,t , the electricity purchase cost C e,t and the operation and maintenance cost C om,t of the integrated energy system are as follows:

[0072]

[0073] In the formula, ζ g is the unit price of natural gas; P grid,t is the interactive power of the integrated energy system and the power distribution network; ζ em,t and ζ es,t are the purchase and sale prices of electricity of the integrated energy system respectively; ζ bat , ζ tes , ζ gt , ζ eb , ζ ec , ζ gb and ζ sofc are the operation and maintenance cost coefficients of the battery, the heat storage tank, the gas turbine, the electric boiler, the electric refrigerator, the gas boiler and the solid oxide fuel cell respectively.

[0074] Further, the constraint conditions of the optimization scheduling model of the integrated energy system considering fuel cell cogeneration include the electric power balance constraint, the heat power balance constraint, the cold power balance constraint, the power upper and lower limits and the climbing constraint of the solid oxide fuel cell, the fuel utilization rate constraint of the solid oxide fuel cell, the gas turbine constraint, the gas boiler constraint, the electric boiler constraint, the electric refrigerator constraint, the battery constraint and the heat storage tank constraint.

[0075] Further, the electric power balance constraint is as follows:

[0076] P gt,t + P sofc,t + P grid,t + P bat,dis,t + P pv,t = P bat,cha,t + P ec,t + P eb,t+ P load,t (26)

[0077] where P pv,t is the power output of the photovoltaic unit; P load,t is the electrical load;

[0078] The thermal power balance constraint is given as follows:

[0079] Q sofc,t + Q eb,t + Q gb,t + Q tes,dis,t = Q tes,cha,t + Q load,heat,t (27)

[0080] where Q load,heat,t is the thermal load;

[0081] The cold power balance constraint is given as follows:

[0082] Q ec,t = Q load,cool,t (28)

[0083] where Q load,cool,t is the cold load;

[0084] The power upper and lower limits of the solid oxide fuel cell and the ramping constraints are given as follows:

[0085]

[0086] where Z sofc,t is a 0-1 variable representing the on-off state of the solid oxide fuel cell, 1 for operation and 0 for shutdown; and are the upper and lower ramping rate limits of the power output of the solid oxide fuel cell, respectively; and are the upper and lower ramping rate limits of the heat output of the solid oxide fuel cell, respectively; and are the upper and lower limits of the power output of the solid oxide fuel cell, respectively; and are the upper and lower limits of the heat output of the solid oxide fuel cell, respectively;

[0087] The fuel utilization constraint of the solid oxide fuel cell is given as follows:

[0088] Z sofc,t u min ≤ u t ≤ Z sofc,t u max (30)

[0089] where umax and u min are the upper and lower limits of the fuel utilization of the solid oxide fuel cell, respectively;

[0090] The gas turbine constraints are as follows:

[0091]

[0092] where: Z gt,t is a 0-1 variable representing the on-off state of the gas turbine, 1 for running and 0 for shutdown; and are the upper and lower ramp rates of the power output of the gas turbine, respectively; and are the upper and lower limits of the power output of the gas turbine, respectively;

[0093] The gas boiler constraints are as follows:

[0094]

[0095] where: Z gb,t is a 0-1 variable representing the on-off state of the gas boiler, 1 for running and 0 for shutdown; and are the upper and lower limits of the heating power of the gas boiler, respectively;

[0096] The electric boiler constraints are as follows:

[0097]

[0098] where: Z eb,t is a 0-1 variable representing the on-off state of the electric boiler, 1 for running and 0 for shutdown; and are the upper and lower limits of the heating power of the electric boiler, respectively;

[0099] The electric refrigerator constraints are as follows:

[0100]

[0101] where: Z ec,t is a 0-1 variable representing the on-off state of the electric refrigerator, 1 for running and 0 for shutdown; and are the upper and lower limits of the refrigeration power of the electric refrigerator, respectively.

[0102] The battery constraints are as follows:

[0103]

[0104] where: Z bat,cha,tZ is a 0-1 variable representing the state of charge of a battery, where 1 represents charging and 0 represents not charging; bat,dis,t The 0-1 variable is used to characterize the discharge state of a battery, where 1 represents discharge and 0 represents no discharge; and These are the upper and lower limits of charging power, respectively. and These are the upper and lower limits of the discharge power, respectively. and These represent the upper and lower limits of the electrical energy stored in the battery; E bat,0 E represents the initial electrical energy. bat,T The final electrical energy within the scheduling cycle;

[0105] The constraints of the thermal storage tank are as follows:

[0106]

[0107] In the formula: Z tes,cha,t Z is a 0-1 variable characterizing the thermal storage state of the thermal storage tank, where 1 represents thermal storage and 0 represents no thermal storage; tes,dis,t The 0-1 variable is used to characterize the heat release state of the thermal storage tank, where 1 represents heat release and 0 represents no heat release; and These are the upper and lower limits of thermal storage capacity, respectively. and These are the upper and lower limits of the heat release power, respectively; and These represent the upper and lower limits of the thermal energy stored in the thermal storage tank; E tes,0 E is the initial thermal energy. tes,T This represents the final thermal energy within the scheduling cycle.

[0108] 4) Linearize the nonlinear constraints in the integrated energy system optimal scheduling model to obtain the optimal scheduling model of the integrated energy system;

[0109] Furthermore, methods for linearizing nonlinear constraints in the integrated energy system optimization scheduling model include piecewise linearization based on the second type of special sequence set.

[0110] 5) Solve the optimal scheduling model of the integrated energy system to obtain the optimal scheduling scheme of the integrated energy system taking into account fuel cell cogeneration.

[0111] Furthermore, tools for solving the optimal scheduling model of a comprehensive energy system include the Gurobi solver.

[0112] The technical effect of the present application is self-evident. The present application aims at the problem that the existing comprehensive energy system optimization scheduling research does not consider the regulation and control of fuel utilization rate of a fuel cell, considers the optimization and control of the fuel utilization rate of the fuel cell, and provides an improved method for optimizing scheduling of a comprehensive energy system considering fuel cell combined heat and power, which can improve the heat production efficiency of the solid oxide fuel cell in a period with high heat load and low electricity price, and can increase the power generation efficiency of the solid oxide fuel cell in a period with high electricity price. BRIEF DESCRIPTION OF DRAWINGS

[0113] Figure 1 It is a schematic diagram of a solid oxide fuel cell combined heat and power system.

[0114] Figure 2 It is a system structure diagram of the method example of the present application.

[0115] Figure 3 It is the predicted value of the electric load, the heat load, the cold load and the photovoltaic unit output of the system example of the method example of the present application.

[0116] Figure 4 It is the fuel utilization rate of the solid oxide fuel cell in scenario 4.

[0117] Figure 5 It is the electric power and the heat power of the solid oxide fuel cell under four scenarios. DETAILED DESCRIPTION

[0118] The present application will be further described below in conjunction with examples, but should not be understood as limiting the above-mentioned subject matter of the present application to the following examples. According to ordinary technical knowledge and conventional means in the art, various substitutions and modifications can be made 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.

[0119] Example 1:

[0120] Reference Figures 1 to 5 An improved method for optimizing scheduling of a comprehensive energy system considering fuel cell combined heat and power, comprising the following steps:

[0121] 1) Obtain the basic parameters of the comprehensive energy system.

[0122] The basic parameters of the comprehensive energy system include the purchase and sale price of electricity, the price of natural gas, the parameters of the solid oxide fuel cell, the parameters of the battery, the parameters of the heat storage tank, the parameters of the gas turbine, the parameters of the gas boiler, the parameters of the electric refrigerator, the predicted value of the photovoltaic unit output, the predicted value of the electric load, the predicted value of the heat load, and the predicted value of the cold load.

[0123] 2) Establish the device model of the comprehensive energy system.

[0124] The device model of the integrated energy system comprises a solid oxide fuel cell combined heat and power model, a gas turbine model, a gas boiler model, an electric boiler model, an electric refrigerator model, a battery model, and a thermal storage tank model.

[0125] The solid oxide fuel cell combined heat and power model comprises a solid oxide fuel cell power generation model and a solid oxide fuel cell heat generation model.

[0126] The solid oxide fuel cell power generation model is shown in Equations (1)-(10) as follows:

[0127]

[0128] In the formula, parameter K r = 1 / (4F); F is Faraday's constant; I t is the current in a single solid oxide fuel cell in a period t; are the molar flow rates of hydrogen and oxygen consumed in a single solid oxide fuel cell in a period t, respectively; are the molar flow rates of water vapor generated in a single solid oxide fuel cell in a period t, respectively.

[0129]

[0130] In the formula, u is the pressure of hydrogen, oxygen, and water vapor in a single solid oxide fuel cell; is the molar flow rate of hydrogen input into a single solid oxide fuel cell; is the valve molar constant of hydrogen, oxygen, and water vapor; r H-O is the ratio of hydrogen flow rate to oxygen flow rate.

[0131]

[0132] In the formula, u t is the fuel utilization rate;

[0133]

[0134] In the formula, q sofc,t is the flow rate of natural gas input into the solid oxide fuel cell; N1 is the number of single cells in series in the cell stack; N2 is the number of parallel columns of the cell stack;

[0135] U sofc,t = N1(E nernst,t -U act,t -U con,t -U ohm,t ) (5)

[0136] In the formula, E nernst,tU represents the Nernst reversible potential of a single solid oxide fuel cell; act,t U con,t U ohm,t These represent the active polarization voltage, concentration polarization voltage, and resistive loss voltage of a single solid oxide fuel cell, respectively; U sofc,t This refers to the output voltage of a solid oxide fuel cell.

[0137]

[0138] In the formula: E0 is the standard potential; R is the universal gas constant; T is the operating temperature of the fuel cell; E nernst,t This is the Nernst reversible potential;

[0139]

[0140] In the formula: I0 is the exchange current; U act,t This is the active polarization voltage;

[0141]

[0142] In the formula: I L U is the limiting current; con,t This is the concentration polarization voltage;

[0143] U ohm,t =rI t (9)

[0144] In the formula: r is the resistance of a single solid oxide fuel cell; U ohm,t This is the voltage at which resistance is lost;

[0145] P sofc,t =N1N2(E nernst,t -U act,t -U con,t -U ohm,t )I t ×10 -3 (10)

[0146] In the formula: P sofc,t This refers to the electrical power output of a solid oxide fuel cell.

[0147] The heat generation models for solid oxide fuel cells are shown in equations (11)-(17), namely:

[0148]

[0149] In the formula: Q gen,sofc,t Q represents the total thermal power generated by the solid oxide fuel cell stack. re,t The heat power required for the methane steam reforming reaction; η gasQ Q pre,air,t Q Q ab,t Q sofc,t Q

[0150] Q gen,sofc,t t q sofc,t -P sofc,t (12)

[0151] Q gen,sofc,t Q

[0152]

[0153] Q C M T T ε Q

[0154]

[0155] C air M air T air,0 T air T air ε pre,air,t Q

[0156]

[0157] Q C C M L T T ε Q ​

[0158]

[0159] In the formula: η ab For afterburner efficiency; L H2 The lower heating value of hydrogen; Q ab,t The thermal power generated by hydrogen combustion in the afterburner;

[0160] Q re,t =ΔH2q sofc,t (17)

[0161] In the formula: ΔH2 is the enthalpy change of the methane steam reforming reaction; Q re,t This refers to the thermal power required for the methane steam reforming reaction;

[0162] The gas turbine model is shown below:

[0163]

[0164] In the formula: P gt,t q represents the power generation capacity of the gas turbine. gt,t The flow rate of natural gas consumed by the gas turbine; η is the calorific value of natural gas. gt The power generation efficiency of the gas turbine;

[0165] The gas boiler model is shown below:

[0166]

[0167] In the formula: Q gb,t q represents the heat output of the gas-fired boiler; gb,t η is the flow rate of natural gas consumed by the gas-fired boiler. gb For the efficiency of gas-fired boilers;

[0168] The electric boiler model is shown below:

[0169] Q eb,t =P eb,t η eb (20)

[0170] In the formula: Q eb,t P is the heating capacity of the electric boiler. eb,t The power consumption of the electric boiler; η eb For the efficiency of electric boilers;

[0171] The electric chiller model is shown below:

[0172] Q ec,t =P ec,t C ec (twenty one)

[0173] In the formula: Qec,t P is the refrigeration power of the electric refrigerator; ec,t C is the power consumption of the electric refrigerator; ec COP is the energy efficiency ratio of the electric refrigerator;

[0174] The battery model is as follows:

[0175]

[0176] In the formula: E bat,t and E bat,t-1 are the electric energy stored by the battery at time t and time t-1, respectively; P bat,cha,t and P bat,dis,t are the charging power and discharging power of the battery, respectively; σ bat , η bat,cha and η bat,dis are the self-discharge rate, charging efficiency and discharging efficiency of the battery, respectively; and Δt is the time duration.

[0177] The heat storage tank model is as follows:

[0178]

[0179] In the formula: E tes,t and E tes,t-1 are the thermal energy stored by the heat storage tank at time t and time t-1, respectively; Q tes,cha,t and Q tes,dis,t are the heat storage power and heat release power of the heat storage tank, respectively; σ tes , η tes,cha and η tes,dis are the self-heat release rate, heat storage efficiency and heat release efficiency of the heat storage tank, respectively.

[0180] 3) Establish an optimal scheduling model of a comprehensive energy system considering fuel cell combined heat and power.

[0181] The objective function of the optimal scheduling model of the comprehensive energy system considering fuel cell combined heat and power is as follows:

[0182]

[0183] In the formula: C IES is the total operation cost of the comprehensive energy system; C g,t , C e,t and C om,t are the gas purchase cost, electricity purchase cost and operation and maintenance cost of the comprehensive energy system, respectively; and T is the scheduling period.

[0184] Among them, the gas purchase cost C g,t , the electricity purchase cost C e,t and the operation and maintenance cost C om,t of the comprehensive energy system are as follows:

[0185]

[0186] wherein: ζ g is the natural gas unit price; P grid,t is the interactive power of the comprehensive energy system and the power distribution network; ζ em,t and ζ es,t are the purchase and sale unit prices of the comprehensive energy system, respectively; ζ bat , ζ tes , ζ gt , ζ eb , ζ ec , ζ gb and ζ sofc are the operation and maintenance cost coefficients of the battery, the heat storage tank, the gas turbine, the electric boiler, the electric refrigerator, the gas boiler and the solid oxide fuel cell, respectively.

[0187] The constraint conditions of the comprehensive energy system optimization scheduling model considering the fuel cell combined heat and power include the electric power balance constraint, the heat power balance constraint, the cold power balance constraint, the power upper and lower limits of the solid oxide fuel cell and the climbing constraint, the fuel utilization rate constraint of the solid oxide fuel cell, the gas turbine constraint, the gas boiler constraint, the electric boiler constraint, the electric refrigerator constraint, the battery constraint and the heat storage tank constraint.

[0188] The electric power balance constraint is as follows:

[0189] P gt,t + P sofc,t + P grid,t + P bat,dis,t + P pv,t = P bat,cha,t + P ec,t + P eb,t + P load,t (26)

[0190] wherein: P pv,t is the power output of the photovoltaic unit; P load,t is the electric load.

[0191] The heat power balance constraint is as follows:

[0192] Q sofc,t + Q eb,t + Q gb,t + Q tes,dis,t = Q tes,cha,t + Q load,heat,t (27)

[0193] wherein: Q load,heat,t is the heat load.

[0194] The cold power balance constraint is as follows:

[0195] Q ec,t = Q load,cool,t (28)

[0196] where: Q load,cool,t is the cooling load;

[0197] The power upper and lower limits of the solid oxide fuel cell and ramping constraints are shown as follows:

[0198]

[0199] where: Z sofc,t is a 0-1 variable representing the on-off state of the solid oxide fuel cell, 1 for running and 0 for shutdown; and are the upper and lower ramping rate limits of the power output of the solid oxide fuel cell, respectively; and are the upper and lower ramping rate limits of the heat output of the solid oxide fuel cell, respectively; and are the upper and lower limits of the power output of the solid oxide fuel cell, respectively; and are the upper and lower limits of the heat output of the solid oxide fuel cell, respectively;

[0200] The fuel utilization constraint of the solid oxide fuel cell is shown as follows:

[0201] Z sofc,t u min ≤ u t ≤ Z sofc,t u max (30)

[0202] where: u max and u min are the upper and lower limits of the fuel utilization of the solid oxide fuel cell, respectively;

[0203] The gas turbine constraints are shown as follows:

[0204]

[0205] where: Z gt,t is a 0-1 variable representing the on-off state of the gas turbine, 1 for running and 0 for shutdown; and are the upper and lower ramping rate limits of the power output of the gas turbine, respectively; and are the upper and lower limits of the power output of the gas turbine, respectively;

[0206] The gas boiler constraints are shown as follows:

[0207]

[0208] where Z gb,t is a 0-1 variable representing the on-off state of the gas boiler, 1 means on, 0 means off; and are the upper and lower limits of the heating power of the gas boiler, respectively;

[0209] The electric boiler constraints are as follows:

[0210]

[0211] where Z eb,t is a 0-1 variable representing the on-off state of the electric boiler, 1 means on, 0 means off; and are the upper and lower limits of the heating power of the electric boiler, respectively;

[0212] The electric refrigerator constraints are as follows:

[0213]

[0214] where Z ec,t is a 0-1 variable representing the on-off state of the electric refrigerator, 1 means on, 0 means off; and are the upper and lower limits of the refrigeration power of the electric refrigerator, respectively.

[0215] The battery constraints are as follows:

[0216]

[0217] where Z bat,cha,t is a 0-1 variable representing the charging state of the battery, 1 means charging, 0 means not charging; Z bat,dis,t is a 0-1 variable representing the discharging state of the battery, 1 means discharging, 0 means not discharging; and are the upper and lower limits of the charging power, respectively; and are the upper and lower limits of the discharging power, respectively; and are the upper and lower limits of the stored electric energy of the battery, respectively; E bat,0 is the initial electric energy; E bat,T is the final electric energy in the scheduling period;

[0218] The thermal storage tank constraints are as follows:

[0219]

[0220] where Ztes,cha,t is a 0-1 variable representing the heat storage state of the heat storage tank, 1 represents heat storage, and 0 represents no heat storage; Z tes,dis,t is a 0-1 variable representing the heat release state of the heat storage tank, 1 represents heat release, and 0 represents no heat release; and are the upper and lower limits of the heat storage power, respectively; and are the upper and lower limits of the heat release power, respectively; and are the upper and lower limits of the heat energy stored in the heat storage tank, respectively;E tes,0 is the initial heat energy;E tes,T is the final heat energy in the dispatching period.

[0221] 4) Linearizing the nonlinear constraints in the integrated energy system optimal dispatching model to obtain an integrated energy system optimal dispatching model;

[0222] The method for linearizing the nonlinear constraints in the integrated energy system optimal dispatching model includes a piecewise linearization method based on a second special order set.

[0223] 5) Solving the integrated energy system optimal dispatching model to obtain an integrated energy system optimal dispatching scheme considering fuel cell cogeneration.

[0224] The tool for solving the integrated energy system optimal dispatching model includes a Gurobi solver.

[0225] Embodiment 2:

[0226] An improved method for optimal dispatching of an integrated energy system considering fuel cell cogeneration, comprising the following steps:

[0227] Step 1: Input the basic parameters of the integrated energy system.

[0228] The basic parameters of the integrated energy system include: electricity purchase and sale prices, natural gas prices, solid oxide fuel cell parameters, battery parameters, heat storage tank parameters, gas turbine parameters, gas boiler parameters, electric refrigerator parameters, photovoltaic unit output prediction values, electric load prediction values, heat load prediction values, cold load prediction values, etc. Among them, the natural gas price is 2.2 yuan / m 3 , the prediction values of photovoltaic unit output, electric load, heat load and cold load are shown in the attached Figure 3 , the main parameters of the solid oxide fuel cell are shown in Table 1, the main parameters of other devices are shown in Table 2, and the time-of-use electricity price is shown in Table 3.

[0229] Table 1 Main parameters of solid oxide fuel cell

[0230] Parameter Value Molar constant of hydrogen valve / (mol / (s·atm)) 0.843 Molar constant of oxygen valve / (mol / (s·atm)) 2.52 Molar constant of water vapor valve / (mol / (s·atm)) 0.281 Exchange current / A 12.112 Limiting current / A 300 Resistance of single solid oxide fuel cell / Ω 3.2813 x 10 -4 ]]> Hydrogen-oxygen flow rate ratio 1.145 Operating temperature of solid oxide fuel cell / K 823 Number of single SOFCs in series of cell stack 1000 Number of columns in parallel of cell stack 10 Preheating temperature of natural gas / K 573 Preheating temperature of air / K 573 Preheating temperature of water / K 573 Initial temperature of natural gas / K 298 Initial temperature of air / K 298 Initial temperature of water / K 298 Efficiency of natural gas preheater 0.9 Efficiency of air preheater 0.9 Efficiency of water preheater 0.9 Efficiency of post-combustion chamber 0.9 Proportion of heat taken away by air 0.9 Upper limit of power generation of solid oxide fuel cell / kW 950 Lower limit of power generation of solid oxide fuel cell / kW 200 Upper ramping rate limit of power generation of solid oxide fuel cell / (kW / h) 100 Lower ramping rate limit of power generation of solid oxide fuel cell / (kW / h) 100

[0231] Main parameters of other devices in Table 2

[0232] Parameter Value Efficiency of gas turbine power generation 0.4 Upper limit of power generation of gas turbine / kW 1200 Lower limit of power generation of gas turbine / kW 200 Upper ramping rate limit of power generation of gas turbine / (kW / h) 150 Lower ramping rate limit of power generation of gas turbine / (kW / h) 150 Self-discharge rate of battery 0.001 Charging efficiency of battery 0.9 Discharging efficiency of battery 0.9 Upper limit of charging power of battery / kW 500 Lower limit of charging power of battery / kW 0 Upper limit of discharging power of battery / kW 500 Lower limit of discharging power of battery / kW 0 Upper limit of stored electric energy of battery / kWh 3000 Lower limit of stored electric energy of battery / kWh 500 Self-heat dissipation rate of heat storage tank 0.01 Heat storage efficiency of heat storage tank 0.9 Heat dissipation efficiency of heat storage tank 0.9 Upper limit of heat storage power of heat storage tank / kW 300 Lower limit of heat storage power of heat storage tank / kW 0 Upper limit of heat dissipation power of heat storage tank / kW 300 Lower limit of heat dissipation power of heat storage tank / kW 0 Upper limit of stored heat energy of heat storage tank / kWh 2500 Lower limit of stored heat energy of heat storage tank / kWh 400 Efficiency of electric boiler 0.7 Upper limit of heating power of electric boiler / kW 500 Lower limit of heating power of electric boiler / kW 100 Energy efficiency ratio of electric refrigerator 4 Upper limit of refrigeration power of electric refrigerator / kW 1500 Lower limit of refrigeration power of electric refrigerator / kW 100 Operation and maintenance cost coefficient of solid oxide fuel cell / (yuan / kWh) 0.01 Operation and maintenance cost coefficient of electric boiler / (yuan / kWh) 0.007 Operation and maintenance cost coefficient of electric refrigerator / (yuan / kWh) 0.0097 Operation and maintenance cost coefficient of gas turbine / (yuan / kWh) 0.0126 Operation and maintenance cost coefficient of battery / (yuan / kWh) 0.005 Operation and maintenance cost coefficient of heat storage tank / (yuan / kWh) 0.002 Operation and maintenance cost coefficient of photovoltaic generator set / (yuan / kWh) 0.0096

[0233] Time-of-use electricity price in Table 3

[0234] Time period Price of purchasing electricity / (yuan / kWh) Price of selling electricity / (yuan / kWh) Peak period (10:00-14:00, 17:00-23:00) 0.83 0.75 Flat period (7:00-10:00, 14:00-17:00) 0.49 0.45 Valley period (23:00-7:00 of next day) 0.17 0.13

[0235] Step 2: Establishing a model of a device in the integrated energy system

[0236] 2.1 Cogeneration model of solid oxide fuel cell

[0237] Among all fuel cells, the solid oxide fuel cell (SOFC) has the highest power generation efficiency, high waste heat utilization value, cogeneration efficiency of more than 80%, and a wide range of fuel sources, such as hydrogen, natural gas and biogas, and has little pollution during power generation, and is known as the most promising green power generation system in the 21st century. Therefore, the present application takes SOFC as an example to study an improved method for optimizing and scheduling an integrated energy system considering fuel cell cogeneration. When the coupled device is another type of fuel cell, the research method is similar.

[0238] The present application takes natural gas as the fuel of SOFC, and assumes that the natural gas is pure methane (CH4). The natural gas is subjected to a reforming reaction to obtain hydrogen, and the hydrogen and oxygen are subjected to an electrochemical reaction in the cell stack to generate electric energy and heat energy, and the electrochemical reaction equation is:

[0239]

[0240] The reforming reaction considered in the present application is steam reforming of methane, and the chemical reaction equation is:

[0241] CH4+2H2O→CO2+4H2ΔH2=164.95kJ / mol (2)

[0242] In the formula: ΔH1 and ΔH2 are the enthalpy changes of chemical reactions.

[0243] The SOFC cogeneration system is as shown in FIG. 1 Figure 1The natural gas, air and water are preheated by the high temperature gas discharged from the afterburner, the preheated air is sent into the cathode of the SOFC, the preheated natural gas is mixed with the water vapor and enters the anode of the SOFC to carry out the steam reforming reaction of the methane to obtain the hydrogen. In the SOFC, the hydrogen and the oxygen carry out the electrochemical reaction to generate the electric energy and the heat energy, the DC / AC inverter converts the direct current into the alternating current to supply the electric load, and most of the heat energy generated by the electrochemical reaction is taken out by the gas in the SOFC. The unreacted hydrogen and oxygen are sent into the afterburner to burn, and the high temperature flue gas discharged from the afterburner preheats the air, the natural gas and the water in sequence through the preheater.

[0244] 1) SOFC power generation model

[0245] According to the electrochemical reaction principle of the fuel cell, the relationship between the consumed and generated gases and the cell current in a single SOFC is obtained as follows:

[0246]

[0247] In the formula, K = 1 / (4F); F is the Faraday constant, 96487 C / mol; I is the current in a single SOFC in a period t, A; nH2 is the molar flow of the hydrogen consumed in a single SOFC in a period t, mol / s; nO2 is the molar flow of the oxygen consumed in a single SOFC in a period t, mol / s; nH2O is the molar flow of the water generated in a single SOFC in a period t, mol / s. The subscript t in the present application represents the variable corresponding to the period t, and the period will not be particularly mentioned below. r t

[0248] In the formula, P is the pressure of the hydrogen, the oxygen and the water vapor in a single SOFC, atm; nH2 is the molar flow of the hydrogen input into a single SOFC, mol / s; nO2 is the molar flow of the oxygen input into a single SOFC, mol / s; nH2O is the molar flow of the water input into a single SOFC, mol / s; R is the universal gas constant, 0.0821 L·atm / (mol·K); T is the temperature of the hydrogen, the oxygen and the water vapor in a single SOFC, K; r is the ratio of the hydrogen flow to the oxygen flow.

[0249]

[0250] In the formula, P is the pressure of the hydrogen, the oxygen and the water vapor in a single SOFC, atm; nH2 is the molar flow of the hydrogen input into a single SOFC, mol / s; nO2 is the molar flow of the oxygen input into a single SOFC, mol / s; nH2O is the molar flow of the water input into a single SOFC, mol / s; R is the universal gas constant, 0.0821 L·atm / (mol·K); T is the temperature of the hydrogen, the oxygen and the water vapor in a single SOFC, K; r is the ratio of the hydrogen flow to the oxygen flow. H-O

[0251] The fuel utilization rate is one of the important operation variables affecting the performance of the SOFC, and is defined as follows:

[0252]

[0253] ​​​​​​​​The output voltage of a single SOFC is small and the output power is low, so the SOFC power generation system is generally composed of several parallel cell stacks, each of which is composed of several single SOFC cells in series. The hydrogen molar flow rate input into a single SOFC is:

[0254]

[0255] wherein q sofc,t is the natural gas flow rate input into the SOFC, and for the convenience of modeling, q sofc,t is taken as the unit of mol / s; N1 is the number of single cells in series in the cell stack; and N2 is the number of parallel cell stacks.

[0256] The output voltage of the SOFC is:

[0257] U sofc,t = N1 (E nernst,t -U act,t -U con,t -U ohm,t ) (7)

[0258] wherein E nernst,t is the Nernst reversible potential of a single SOFC, V; U act,t , U con,t , and U ohm,t are the active polarization voltage, the concentration polarization voltage, and the resistance loss voltage of a single SOFC, respectively, V.

[0259] The Nernst reversible potential is:

[0260]

[0261] wherein E0 is the standard potential, V; R is the universal gas constant, 8.314 J / (mol·K); and T is the working temperature of the fuel cell, K.

[0262] The active polarization voltage is:

[0263]

[0264] wherein I0 is the exchange current, A.

[0265] The concentration polarization voltage is:

[0266]

[0267] wherein I L is the limiting current, A.

[0268] The resistance loss voltage is:

[0269] U ohm,t = rI t(11)

[0270] wherein r is the resistance of a single SOFC, Ω.

[0271] The electric power output by the SOFC cogeneration system is:

[0272] P sofc,t = N1N2(E nernst,t -U act,t -U con,t -U ohm,t )I t × 10 -3 (12)

[0273] wherein P sofc,t is the electric power output by the SOFC, kW.

[0274] 2) Heat production model of SOFC

[0275] In the SOFC cogeneration system, the stack and the post-combustion chamber are the heat sources, and the heat produced is partly used to provide thermal energy for the reforming reaction and to preheat air, natural gas and water, and the other part is used to supply external heat load, therefore, the heat power Q sofc,t output by the SOFC is:

[0276]

[0277] wherein Q gen,sofc,t is the total heat power produced by the SOFC stack, kW; Q re,t is the heat power required for the steam reforming reaction of methane, kW; η gas is the proportion of heat taken away by the gas in the stack; is the heat power required for preheating natural gas, kW; Q pre,air,t is the heat power required for preheating air, kW; is the heat power required for preheating water, kW; Q ab,t is the heat power produced by the combustion of hydrogen in the post-combustion chamber, kW.

[0278] The total heat power produced by the SOFC stack is:

[0279] Q gen,sofc,t = -4ΔH1u t q sofc,t -P sofc,t (14)

[0280] The heat power required for preheating natural gas is:

[0281]

[0282] wherein: Cp is the specific heat capacity of natural gas, kJ / (kg·K) ; Mn is the molar mass of natural gas, kg / mol; Tn is the initial temperature of natural gas, K; Tn is the preheating temperature of natural gas, K; εn is the efficiency of natural gas preheater.

[0283] The volume fraction of oxygen in air is 21%, so the heat power required for preheating air is:

[0284]

[0285] In the formula: C air Cp is the specific heat capacity of air, kJ / (kg·K) ; M air M is the molar mass of air, kg / mol; T air,0 T is the initial temperature of air, K; T air T is the preheating temperature of air, K; ε air ε is the efficiency of air preheater.

[0286] The heat power required for preheating water is:

[0287]

[0288] In the formula: Cp is the specific heat capacity of liquid water, kJ / (kg·K) ; Cp is the specific heat capacity of water vapor, kJ / (kg·K) ; M is the molar mass of water, kg / mol; L is the latent heat of vaporization of water, kJ / kg; T is the initial temperature of water, K; T is the preheating temperature of water, K; ε is the efficiency of water preheater.

[0289] The hydrogen gas not involved in the electrochemical reaction is sent to the afterburner for combustion, and the heat power generated by the combustion of hydrogen gas in the afterburner is:

[0290]

[0291] In the formula: η ab η is the efficiency of the afterburner; LHV is the low heat value of hydrogen, kJ / m 3 .

[0292] The steam reforming reaction of methane is a strong endothermic reaction, and the heat energy required for the reforming reaction is provided by the electric pile. As can be seen from the above, the heat power required for the steam reforming reaction of methane is:

[0293] Q re,t = ΔH2q sofc,t(19)

[0294] 2.2 Gas turbine model

[0295] A gas turbine generates electricity by consuming natural gas, and the relationship between the natural gas flow rate and the electric power is:

[0296]

[0297] where: P gt,t is the electric power generated by the gas turbine, kW; q gt,t is the natural gas flow rate consumed by the gas turbine, m 3 / s; is the heating value of natural gas, kJ / m 3 ; η gt is the electric power generation efficiency of the gas turbine.

[0298] 2.3 Gas boiler model

[0299] A gas boiler consumes natural gas to generate heat energy, and its model is as follows:

[0300]

[0301] where: Q gb,t is the heat generation power of the gas boiler, kW; q gb,t is the natural gas flow rate consumed by the gas boiler, m 3 / s; η gb is the efficiency of the gas boiler.

[0302] 2.4 Electric boiler model

[0303] An electric boiler consumes electric energy to generate heat, and its model is:

[0304] Q eb,t = P eb,t η eb (22)

[0305] where: Q eb,t is the heat generation power of the electric boiler, kW; P eb,t is the electric power consumed by the electric boiler, kW; η eb is the efficiency of the electric boiler.

[0306] 2.5 Electric refrigerator model

[0307] An electric refrigerator consumes electric energy to generate cold, and its model is:

[0308] Q ec,t = P ec,t C ec (23)

[0309] where: Q ec,tP is the refrigeration power of the electric refrigerator, kW; P ec,t C is the power consumption of the electric refrigerator, kW; C ec COP is the energy efficiency ratio of the electric refrigerator.

[0310] 2.6 Battery model

[0311] The model of the battery is:

[0312]

[0313] E bat,t and E bat,t-1 are the electrical energy stored in the battery at time period t and t-1, kWh; P bat,cha,t and P bat,dis,t are the charging power and discharging power of the battery, kW; σ bat , η bat,cha , and η bat,dis are the self-discharge rate, charging efficiency, and discharging efficiency of the battery, respectively; Δt is the duration of the time period (1h in the present application).

[0314] 2.7 Heat storage tank model

[0315] The model of the heat storage tank is:

[0316]

[0317] E tes,t and E tes,t-1 are the thermal energy stored in the heat storage tank at time period t and t-1, kWh; Q tes,cha,t and Q tes,dis,t are the heat storage power and heat release power of the heat storage tank, kW; σ tes , η tes,cha , and η tes,dis are the self-heat release rate, heat storage efficiency, and heat release efficiency of the heat storage tank, respectively.

[0318] Step 3: Establishing an optimal scheduling model of a comprehensive energy system considering fuel cell combined heat and power

[0319] 3.1 Objective function

[0320] The optimal scheduling of the comprehensive energy system is based on information such as electricity price, gas price, and next-day load forecast information. By optimizing the purchase / sale of electricity and the operating conditions of various devices, the operating cost of the comprehensive energy system is minimized.

[0321] The objective function of the optimal scheduling of the comprehensive energy system is as follows:

[0322]

[0323] CIES C is the total operation cost of the integrated energy system, yuan; T is a dispatching period (24h in the present application). g,t C e,t C om,t C are respectively the gas purchase cost, the electricity purchase cost and the operation and maintenance cost of the integrated energy system, yuan; T is a dispatching period (24h in the present application).

[0324] Each cost is specifically calculated as follows:

[0325]

[0326] In the formula: ζ g is a natural gas unit price, yuan / m 3 ; P grid,t is the interactive power of the integrated energy system and the power distribution network (negative indicating selling electricity to the power distribution network), kW; ζ em,t and ζ es,t are respectively the electricity purchase and sale unit prices of the integrated energy system, yuan / kWh; ζ bat , ζ tes , ζ gt , ζ eb , ζ ec , ζ gb and ζ sofc are respectively the operation and maintenance cost coefficients of the battery, the heat storage tank, the gas turbine, the electric boiler, the electric refrigerator, the gas boiler and the SOFC, yuan / kWh.

[0327] 3.2 Constraint conditions

[0328] The constraint conditions of the integrated energy system optimization scheduling model of the present application include: the electric / thermal / cold power balance constraint of the integrated energy system, the model of various devices in the integrated energy system and the operation constraint thereof. The model of various devices in the integrated energy system is shown in step (2), and the other constraints are described in detail as follows.

[0329] Electric power balance constraint:

[0330] P gt,t + P sofc,t + P grid,t + P bat,dis,t + P pv,t = P bat,cha,t + P ec,t + P eb,t + P load,t (28)

[0331] In the formula: P pv,t is the power output of the photovoltaic unit, kW; P load,t is the electric load, kW.

[0332] Thermal power balance constraint:

[0333] Q sofc,t +Q eb,t +Q gb,t +Q tes,dis,t =Q tes,cha,t +Q load,heat,t (29)

[0334] where Q load,heat,t is the thermal duty, kW.

[0335] Cold power balance constraint:

[0336] Q ec,t =Q load,cool,t (30)

[0337] where Q load,cool,t is the cold duty, kW.

[0338] SOFC power upper and lower limits and ramping constraints:

[0339]

[0340] where Z sofc,t is a 0-1 variable representing the SOFC on-off state (1 for on, 0 for off); and are the SOFC power generation upper and lower ramping rate limits, kW / h, respectively; and are the SOFC heat generation upper and lower ramping rate limits, kW / h, respectively; and are the SOFC power generation upper and lower limits, kW, respectively; and are the SOFC heat generation upper and lower limits, kW, respectively.

[0341] In addition to satisfying the power upper and lower limits and ramping constraints, the SOFC fuel utilization must also satisfy the following constraints:

[0342] Z sofc,t u min ≤u t ≤Z sofc,t u max (32)

[0343] where u max and u min are the SOFC fuel utilization upper and lower limits, respectively.

[0344] Gas turbine constraints:

[0345]

[0346] where: Z gt,t is a 0-1 variable representing the on-off state of the gas turbine (1 for running, 0 for shutdown); and are the upper and lower climb rate limits of the gas turbine power, kW / h, respectively; and are the upper and lower limits of the gas turbine power, kW, respectively.

[0347] Gas boiler constraints:

[0348]

[0349] where: Z gb,t is a 0-1 variable representing the on-off state of the gas boiler (1 for running, 0 for shutdown); and are the upper and lower limits of the gas boiler heating power, kW, respectively.

[0350] Electric boiler constraints:

[0351]

[0352] where: Z eb,t is a 0-1 variable representing the on-off state of the electric boiler (1 for running, 0 for shutdown); and are the upper and lower limits of the electric boiler heating power, kW, respectively.

[0353] Electric refrigerator constraints:

[0354]

[0355] where: Z ec,t is a 0-1 variable representing the on-off state of the electric refrigerator (1 for running, 0 for shutdown); and are the upper and lower limits of the electric refrigerator cooling power, kW, respectively.

[0356] Battery constraints:

[0357]

[0358] where: Z bat,cha,t is a 0-1 variable representing the charging state of the battery (1 for charging, 0 for not charging); Z bat,dis,t is a 0-1 variable representing the discharging state of the battery (1 for discharging, 0 for not discharging); and are the upper and lower limits of the charging power, kW, respectively; and are the upper and lower limits of the discharging power, kW, respectively. and are the upper and lower limits of the battery stored electrical energy, kWh; the third equation is the mutual exclusive constraint of charging and discharging state; the fourth equation requires the final electrical energy E bat,T returns to the initial electrical energy E bat,0 to ensure the sustainable scheduling of the next day.

[0359] Heat storage tank constraint:

[0360]

[0361] In the formula: Z tes,cha,t is a 0-1 variable representing the heat storage state of the heat storage tank (1 represents heat storage, and 0 represents no heat storage); Z tes,dis,t is a 0-1 variable representing the heat release state of the heat storage tank (1 represents heat release, and 0 represents no heat release); and are the upper and lower limits of the heat storage power, kW; and are the upper and lower limits of the heat release power, kW; and are the upper and lower limits of the heat storage energy of the heat storage tank, kWh; the third equation is the mutual exclusive constraint of heat storage and heat release state; the fourth equation requires the final heat energy E tes,T returns to the initial heat energy E tes,0 to ensure the sustainable scheduling of the next day.

[0362] Step 4 linearizes the scheduling model and solves it

[0363] In combination with the foregoing objective function and constraint condition, the optimal scheduling of the comprehensive energy system of the fuel cell combined heat and power can be expressed as the following optimization problem:

[0364]

[0365] Obviously, problem (39) is a mixed integer nonlinear programming problem, which contains multiple 0-1 variables representing the start-stop state of the device and nonlinear constraints. The present application adopts a segmented linearization method based on the second type of special order set (SOS) to process the nonlinear constraint, converts problem (39) into a mixed integer linear programming problem, and then solves the problem by calling the Gurobi solver through Yalmip.

[0366] Experimental results:

[0367] To verify the economy and effectiveness of the method of the present application, the comprehensive energy system shown in the accompanying drawings is taken as the simulation object, and the following four scenarios are designed: Figure 2

[0368] ​Scenario 1: The fuel utilization rate of SOFC is 0.75;

[0369] Scenario 2: The fuel utilization rate of SOFC is 0.8;

[0370] Scenario 3: The fuel utilization rate of SOFC is 0.85;

[0371] Scenario 4: The fuel utilization rate of SOFC can be flexibly adjusted within the range of 0.6 to 0.9.

[0372] The difference between Scenario 4 and Scenario 1, Scenario 2 and Scenario 3 is that the fuel utilization rate of SOFC in Scenario 4 is not a fixed value, but a decision variable to be optimized.

[0373] (1) Comparison of SOFC operating states

[0374] Appendix Figure 4 and attached Figure 5 The fuel utilization rate of SOFC in Scenario 4 and the electrical and thermal power of SOFC in the four scenarios are given respectively.

[0375] From the appendix Figure 4 and attached Figure 5 It can be seen that since the periods from 1 to 7 and 24 are off-peak electricity price periods and the heat load is high and the electricity load is low during these periods, in order to increase the heat production efficiency of SOFC and thus increase the heat power, the fuel utilization rate of SOFC in Scenario 4 is low, and its heat power is high, which also leads to its electricity power being low. In the period from 8 to 23, although the heat load is greater than the electricity load in some periods (such as 8 and 20 to 23), the electricity purchase price is high at this time. In order to reduce the electricity purchase cost, the electricity power of SOFC in Scenario 4 reaches the upper limit. In addition, in order to increase the power production efficiency of SOFC, the fuel utilization rate is high during this period, which leads to the low heat power during this period.

[0376] SOFC combined heat and power is highly efficient. To reduce operating costs, as shown in the attached... Figure 5 As shown, the power of SOFC in scenarios 1, 2 and 3 all reach the upper limit. Since the fuel utilization rate in these three scenarios is constant, the operating state of SOFC in each time period is the same in the three scenarios.

[0377] (2) Comparison of operating costs

[0378] The total operating costs for the four scenarios are shown in Table 4.

[0379] Table 4 Total Operating Costs of Integrated Energy Systems in Different Scenarios

[0380] Scenario Scenario 1 Scenario 2 Scenario 3 Scenario 4 Total operation cost / yuan 15907 16231 16455 15789

[0381] As shown in Table 4, since the fuel utilization rate of the SOFC in scenario 4 is adjustable, the operation state of the SOFC is more flexible than that in scenarios 1, 2 and 3 in which the fuel utilization rate is fixed, the SOFC can increase the heat production efficiency in the period with high heat load and low electricity price, and can increase the electricity production efficiency in the period with high electricity price, therefore, the operation cost of scenario 4 is the lowest, which verifies the economy and effectiveness of the method.

[0382] Embodiment 3

[0383] An improved method for optimizing scheduling of a comprehensive energy system considering fuel cell combined heat and power generation, comprising the following steps:

[0384] 1) obtaining basic parameters of the comprehensive energy system; 2) establishing a device model of the comprehensive energy system; 3) establishing an optimization scheduling model of the comprehensive energy system considering fuel cell combined heat and power generation; 4) linearizing the nonlinear constraints in the optimization scheduling model of the comprehensive energy system to obtain an optimal scheduling model of the comprehensive energy system; 5) solving the optimal scheduling model of the comprehensive energy system to obtain an optimization scheduling scheme of the comprehensive energy system considering fuel cell combined heat and power generation.

[0385] Embodiment 4

[0386] An improved method for optimizing scheduling of a comprehensive energy system considering fuel cell combined heat and power generation, mainly as shown in Embodiment 3, wherein the basic parameters of the comprehensive energy system include electricity purchase and sale prices, natural gas prices, solid oxide fuel cell parameters, battery parameters, heat storage tank parameters, gas turbine parameters, gas boiler parameters, electric refrigerator parameters, photovoltaic unit output prediction values, electric load prediction values, heat load prediction values, and cold load prediction values.

[0387] Embodiment 5

[0388] An improved method for optimizing scheduling of a comprehensive energy system considering fuel cell combined heat and power generation, mainly as shown in Embodiment 3, wherein the device model of the comprehensive energy system includes a solid oxide fuel cell combined heat and power generation model, a gas turbine model, a gas boiler model, an electric boiler model, an electric refrigerator model, a battery model, and a heat storage tank model.

[0389] The power generation model of the solid oxide fuel cell is shown in formulas (1)-(10). The heat production model of the solid oxide fuel cell is shown in formulas (11)-(17). The gas turbine model is shown in formulas (18)-(21). The battery model is shown in formula (22). The heat storage tank model is shown in formula (23).

[0390] Embodiment 6

[0391] An improved method for optimal scheduling of integrated energy systems considering fuel cell combined heat and power, the main content of which is seen in embodiment 3, wherein the objective function of the optimal scheduling model of integrated energy systems considering fuel cell combined heat and power is shown in formulas (24)-(25).

[0392] Embodiment 7:

[0393] An improved method for optimal scheduling of integrated energy systems considering fuel cell combined heat and power, the main content of which is seen in embodiment 3, wherein the constraint conditions of the optimal scheduling model of integrated energy systems considering fuel cell combined heat and power include power balance constraints, heat power balance constraints, cold power balance constraints, power upper and lower limits of solid oxide fuel cells and climbing constraints, fuel utilization constraints of solid oxide fuel cells, gas turbine constraints, gas boiler constraints, electric boiler constraints, electric refrigerator constraints, battery constraints, and heat storage tank constraints, which are shown in formulas (26)-(36), respectively.

[0394] Embodiment 8:

[0395] An improved method for optimal scheduling of integrated energy systems considering fuel cell combined heat and power, the main content of which is seen in embodiment 3, wherein the method for linearizing the nonlinear constraints in the optimal scheduling model of integrated energy systems includes a piecewise linearization method based on the second special order set.

[0396] Embodiment 9:

[0397] An improved method for optimal scheduling of integrated energy systems considering fuel cell combined heat and power, the main content of which is seen in embodiment 3, wherein the tool for solving the optimal scheduling model of integrated energy systems includes a Gurobi solver.

Claims

1. An improved method for optimal scheduling of integrated energy systems considering fuel cell cogeneration, characterized in that, The method comprises the following steps: 1) obtaining basic parameters of the integrated energy system; 2) establishing a device model of the integrated energy system; 3) establishing an optimal scheduling model of the integrated energy system considering fuel cell cogeneration; 4) linearizing the nonlinear constraints in the optimal scheduling model of the integrated energy system to obtain an optimal scheduling model of the integrated energy system; 5) solving the optimal scheduling model of the integrated energy system to obtain an optimal scheduling scheme of the integrated energy system considering fuel cell cogeneration; The device model of the integrated energy system comprises a solid oxide fuel cell cogeneration model, a gas turbine model, a gas boiler model, an electric boiler model, an electric refrigerator model, a battery model, and a heat storage tank model; The solid oxide fuel cell cogeneration model comprises a solid oxide fuel cell power generation model and a solid oxide fuel cell heat generation model; The solid oxide fuel cell power generation model is shown in formulas (1)-(10), i.e.: where: parameter K = 1 / (4F); F is the Faraday constant; I is the current; r = 1 / (4F); F is the Faraday constant; I is the current; t is the molar flow of hydrogen consumed in the single solid oxide fuel cell during the time period t; is the molar flow of hydrogen consumed in the single solid oxide fuel cell during the time period t; is the molar flow of hydrogen consumed in the single solid oxide fuel cell during the time period t; where: P is the pressure of hydrogen, oxygen, and water vapor in a single solid oxide fuel cell; is the molar flow rate of hydrogen into a single solid oxide fuel cell; is the valve molar constant for hydrogen, oxygen, and water vapor; r H-O is the ratio of hydrogen flow rate to oxygen flow rate; wherein: u t is the fuel utilization; wherein: q sofc,t is the flow of natural gas into the solid oxide fuel cell; N1 is the number of series-connected single cells in the cell stack; N2 is the number of parallel-connected columns of the cell stack; U sofc,t = N1(E nernst,t -U act,t -U con,t -U ohm,t ) (5) wherein: E nernst,t is the Nernst reversible potential of a single solid oxide fuel cell; U act,t , U con,t , U ohm,t are the active polarization voltage, the concentration polarization voltage and the ohmic loss voltage of a single solid oxide fuel cell, respectively; U sofc,t is the output voltage of a solid oxide fuel cell; wherein: E0is the standard potential; R is the universal gas constant; T is the operating temperature of the fuel cell; E nernst,t is the Nernst reversible potential; where: I0 is the exchange current; U act,t is the active polarization voltage; wherein: I L is the limiting current; U con,t is the concentration polarization voltage; U ohm,t = rI t (9) where: r is the resistance of a single solid oxide fuel cell; U ohm,t is the voltage of the resistance loss P sofc,t = N1N2(E nernst,t -U act,t -U con,t -U ohm,t )I t x 10 -3 (10) wherein: P sofc,t P is the electrical power output from the solid oxide fuel cell; The solid oxide fuel cell heat generation model is shown in formulas (11)-(17), i.e.: where: Q gen,sofc,t Qtotal is the total thermal power generated by the solid oxide fuel cell stack; Q re,t Qreforming is the thermal power required for the steam reforming reaction of methane; η gas η is the proportion of the heat taken away by the gases in the stack; Q is the heat power required to preheat the natural gas; pre,air,t Q is the heat power required to preheat the air; Q is the heat power required to preheat the water; ab,t Q is the heat power generated by the combustion of hydrogen in the afterburner; sofc,t Q is the heat power output by the solid oxide fuel cell; Q gen,sofc,t = -4ΔH1u t q sofc,t -P sofc,t (12) where: ΔH1 is the enthalpy change of the electrochemical reaction of hydrogen and oxygen in the cell stack; Q gen,sofc,t is the total thermal power generated by the cell stack; wherein: Cp is the specific heat capacity of the natural gas; M is the molar mass of the natural gas; T0 is the initial temperature of the natural gas; Tpre is the preheating temperature of the natural gas; ηpre is the efficiency of the natural gas preheater; Ppre is the thermal power required to preheat the natural gas; where: C air specific heat capacity of air; M air molar mass of air; T air,0 initial temperature of air; T air preheating temperature of air; ε air efficiency of air preheater; Q pre,air,t thermal power required for preheating air; wherein: Cp is the specific heat capacity of liquid water; Cv is the specific heat capacity of water vapor; M is the molar mass of water; L is the latent heat of vaporization of water; T0 is the initial temperature of water; Tpre is the preheating temperature of water; ηpre is the efficiency of the water preheater; Ppre is the thermal power required to preheat water; wherein: η ab is the efficiency of the afterburner; is the lower heating value of hydrogen; Q ab,t is the thermal power generated by the combustion of hydrogen in the afterburner; Q re,t = ΔH2q sofc,t (17) where ΔH2is the enthalpy change of the steam methane reforming reaction; Q re,t is the heat power required for the steam methane reforming reaction.

2. The improved method for optimal dispatch of an integrated energy system considering fuel cell combined heat and power according to claim 1, wherein, The basic parameters of the integrated energy system comprise electricity purchase and sale prices, natural gas prices, solid oxide fuel cell parameters, battery parameters, heat storage tank parameters, gas turbine parameters, gas boiler parameters, electric refrigerator parameters, photovoltaic unit output prediction values, electric load prediction values, heat load prediction values, and cold load prediction values.

3. The improved method for optimal dispatch of a CCHug system according to claim 1, wherein The gas turbine model is shown as follows: where: P gt,t is the power generated by the gas turbine; q gt,t is the flow rate of natural gas consumed by the gas turbine; is the heating value of the natural gas; η gt is the efficiency of the gas turbine; The gas boiler model is shown as follows: where: Q gb,t is the heat production of the gas boiler; q gb,t is the flow rate of natural gas consumed by the gas boiler; η gb is the efficiency of the gas boiler; The electric boiler model is shown as follows: Q eb,t = P eb,t η eb (20) wherein: Q eb,t is the heating power of the electric boiler; P eb,t is the power consumption of the electric boiler; η eb is the efficiency of the electric boiler; The electric refrigerator model is shown as follows: Q ec,t = P ec,t C ec (21) wherein: Q ec,t is the refrigeration power of the electric refrigerator; P ec,t is the power consumption of the electric refrigerator; C ec is the energy efficiency ratio of the electric refrigerator; The battery model is shown as follows: wherein: E bat,t and E bat,t-1 are the electrical energy stored in the battery for the time period t and t-1, respectively; P bat,cha,t and P bat,dis,t are the charging and discharging power of the battery, respectively; σ bat , η bat,cha , and η bat,dis are the self-discharge rate, charging efficiency, and discharging efficiency of the battery, respectively; and Δt is the time period duration. The heat storage tank model is shown as follows: wherein: E tes,t and E tes,t-1 are the thermal energy stored in the thermal storage tank at time period t and t-1, respectively; Q tes,cha,t and Q tes,dis,t are the thermal storage power and thermal release power of the thermal storage tank, respectively; σ tes , η tes,cha , and η tes,dis are the self-heat generation rate, thermal storage efficiency, and thermal release efficiency of the thermal storage tank, respectively.

4. The improved method for optimal dispatch of a CCHug system according to claim 1, wherein, The objective function of the optimal scheduling model of the integrated energy system considering fuel cell cogeneration is shown as follows: In the formula: C IES is the total operation cost of the integrated energy system; C g,t , C e,t and C om,t are the gas purchase cost, electricity purchase cost and operation and maintenance cost of the integrated energy system respectively; T is the dispatching period; Wherein, the gas purchase cost C of the integrated energy system g,t , the electricity purchase cost C e,t and the operation and maintenance cost C om,t are as follows: wherein: ζ g is the unit price of natural gas; P grid,t is the interactive power between the integrated energy system and the distribution network; ζ em,t and ζ es,t are the purchase and sale prices of electricity of the integrated energy system, respectively; ζ bat , ζ tes , ζ gt , ζ eb , ζ ec , ζ gb and ζ sofc are the operation and maintenance cost coefficients of the battery, the heat storage tank, the gas turbine, the electric boiler, the electric refrigerator, the gas boiler and the solid oxide fuel cell, respectively.

5. The improved method for optimal dispatch of an integrated energy system considering fuel cell combined heat and power according to claim 1, wherein, The constraint conditions of the optimal scheduling model of the integrated energy system considering fuel cell cogeneration comprise electric power balance constraints, heat power balance constraints, cold power balance constraints, power upper and lower limits and ramping constraints of the solid oxide fuel cell, fuel utilization rate constraints of the solid oxide fuel cell, gas turbine constraints, gas boiler constraints, electric boiler constraints, electric refrigerator constraints, battery constraints, and heat storage tank constraints.

6. The improved method for optimal dispatch of an integrated energy system considering fuel cell combined heat and power according to claim 5, wherein, The electric power balance constraints are shown as follows: P gt,t +P sofc,t +P grid,t +P bat,dis,t +P pv,t =P bat,cha,t +P ec,t +P eb,t +P load,t (26) where: P pv,t is the power output by the photovoltaic unit; P load,t is the electrical load; The heat power balance constraints are shown as follows: Q sofc,t +Q eb,t +Q gb,t +Q tes,dis,t =Q tes,cha,t +Q load,heat,t (27) In the formula: Q load,heat,t is the heat load; The cold power balance constraints are shown as follows: Q ec,t = Q load,cool,t (28) In the formula: Q load,cool,t is the cooling load; The power upper and lower limits and ramping constraints of the solid oxide fuel cell are shown as follows: wherein Z sofc,t is a 0-1 variable representing the on-off state of the solid oxide fuel cell, 1 representing operation and 0 representing shutdown; and are the upper and lower ramp rate limits of the power generation of the solid oxide fuel cell, respectively; and are the upper and lower ramp rate limits of the heat production of the solid oxide fuel cell, respectively; and are the upper and lower limits of the power generation of the solid oxide fuel cell, respectively; and are the upper and lower limits of the heat production of the solid oxide fuel cell, respectively. The fuel utilization rate constraints of the solid oxide fuel cell are shown as follows: Z sofc,t u min ≤u t ≤Z sofc,t u max (30) where: u max and u min are the upper and lower limits, respectively, of the fuel utilization of the solid oxide fuel cell The gas turbine constraints are shown as follows: wherein: Z gt,t is a 0-1 variable representing the start-stop condition of the gas turbine, 1 indicating operation and 0 indicating shutdown; and are respectively the upper and lower climb rate limits of the power output of the gas turbine; and are respectively the upper and lower limits of the power output of the gas turbine; The gas boiler constraints are shown as follows: wherein: Z gb,t is a 0-1 variable representing the on-off state of the gas boiler, 1 indicating operation and 0 indicating shutdown; and are, respectively, the upper and lower limits of the heating power of the gas boiler; The electric boiler constraints are shown as follows: wherein: Z eb,t is a 0-1 variable representing the on-off state of the electric boiler, 1 representing operation and 0 representing shutdown; and are the upper and lower limits of the heating power of the electric boiler, respectively. The electric refrigerator constraints are shown as follows: wherein: Z ec,t is a 0-1 variable representing the on-off state of the electric refrigerator, 1 indicating operation and 0 indicating stop; and are the upper and lower limits of the refrigeration power of the electric refrigerator, respectively. The battery constraints are shown as follows: where: Z bat,cha,t is a 0-1 variable representing the state of charge of the battery, 1 indicating charge and 0 indicating no charge; bat,dis,t is a 0-1 variable representing the state of discharge of the battery, 1 indicating discharge and 0 indicating no discharge; and are, respectively, upper and lower limits on charging power; and are, respectively, upper and lower limits on discharging power; and are, respectively, upper and lower limits on the amount of energy stored in the battery; E bat,0 is the initial amount of energy; E bat,T is the final amount of energy over the dispatch period; The heat storage tank constraints are shown as follows: where: Z tes,cha,t is a 0-1 variable representing the state of the thermal storage tank, 1 indicating thermal storage and 0 indicating no thermal storage; Z tes,dis,t is a 0-1 variable representing the state of the thermal storage tank, 1 indicating thermal storage and 0 indicating no thermal storage; and are the upper and lower limits of the thermal storage power, respectively; and are the upper and lower limits of the thermal storage power, respectively; and are the upper and lower limits of the thermal storage tank, respectively; E tes,0 is the initial thermal energy; E tes,T is the final thermal energy within the dispatch period.

7. The improved method for optimal dispatch of an integrated energy system considering fuel cell combined heat and power according to claim 1, wherein: The method for linearizing the nonlinear constraints in the optimal scheduling model of the integrated energy system comprises a piecewise linearization method based on a second-type special order set. 8.The improved method for optimal dispatch of a CCHugrid system according to claim 1, wherein: The tool for solving the optimal scheduling model of the integrated energy system comprises a Gurobi solver.

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