Load Optimization Scheduling Method in Hydrogen Reduction Steel Production Process Considering Renewable Energy

Abstract

A load optimization scheduling method for hydrogen-reduced steel production processes that considers renewable energy includes: proposing a matrix-based coordination strategy for equipment start-up and shutdown between production steps; analyzing the load operating mechanism of steel production equipment in hydrogen-reduced steel plants and establishing a load control model for these equipment; and analyzing the coupled relationship between electricity and hydrogen production and consumption in hydrogen-reduced steel plants to construct a load optimization scheduling model for hydrogen-reduced steel production equipment that considers renewable energy. This method minimizes production costs for steel companies while increasing the renewable energy absorption rate, providing a basis for accurate and reliable assessment of steel companies' demand response potential.

Description

Technical Field

[0001] The present invention relates to the technical field of power load regulation, and in particular to a load optimization scheduling method in a hydrogen reduction steel production process taking renewable energy into consideration. Background Art

[0002] As a typical large-scale traditional industrial user of electricity, steel companies are characterized by high load demands, high levels of automation, and strong shock loads. With the gradual advancement of industrial decarbonization, digitalization, and automation, the traditional steel industry's main energy consumption has gradually shifted from coal to electricity. However, the existing mainstream low-carbon electrified steel production process relies heavily on scrap steel as its production raw material, and the global scrap steel shortage has hindered the promotion of low-carbon electric arc furnace production processes. The hydrogen reduction electric furnace steel production process (H2DRI-EAF), which has the ability to process the entire process from iron ore to finished steel parts, has become the most promising low-carbon steel production process.

[0003] Domestic and foreign scholars have conducted extensive research on the fine-grained control model of load in the hydrogen reduction steel production process.

[0004] [1]: Ye Xingjie, Xu Yonghai, Huang Zitong, et al. Participation of steel enterprises in power system dispatching and wind power consumption [J]. Electric Power Automation Equipment, 2023, 43(08): 112-118. DOI: 10.16081 / j.epae.202301021. In this paper, considering the random volatility of arc furnace power and wind power, an arc furnace power control model for adjusting the arc furnace transformer tap is proposed to study the problem of steel enterprises participating in power system dispatching and wind power consumption.

[0005] Reference [2]: Wang Haibo, Zhang Li. Supply and demand interactive scheduling model considering the production process of short-process steel enterprises [J]. Automation of Electric Power Systems, 2021, 45(15): 64-76. A power grid scheduling model for electric furnace short-process steel enterprises is proposed. By optimizing the process connection logic, the renewable energy absorption capacity of steel enterprises under flexible scheduling is evaluated.

[0006] Reference [3]: Jiayang Wang, Qiang Wang, Wenqiang Sun, Optimal power system flexibility-based scheduling in iron and steel production: A case of steelmaking-refining-continuous casting process, Journal of Cleaner Production, Volume 414, 2023. A steelmaking-refining-continuous casting scheduling model based on process flexibility was constructed, and a resource task network model considering flexibility was constructed. With the goal of minimizing electricity costs, various load modes of the refining ladle furnace were considered to optimize the resource scheduling of steel enterprises.

[0007] Currently, there are few studies on low-carbon steel production technology, and the focus is mainly on the power consumption and the coupling relationship between electricity and hydrogen in the two production steps of electrolysis and direct reduction of hydrogen. For example, in the literature [4]: Vahid Shahbazbegian, Miadreza Shafie-khah, Hannu Laaksonen, Goran Strbac, Hossein Ameli, Resilience-oriented operation of microgrids in the presence of power to hydrogen systems, Applied Energy 2023, 348. A technical and economic analysis of the H2DRI system was conducted, revealing that the use of green hydrogen in hydrogen reduction steel plants can significantly reduce direct carbon dioxide emissions by up to 85%. However, to ensure economic feasibility, the unit hydrogen production or procurement cost must be reduced to US$1.63 / kg or lower.

[0008] Reference [5]: Elsheikh H, Eveloy V. Assessment of variable solar-and grid electricity-driven power to hydrogen integration with direct iron orereduction for low-carbon steel making. Fuel 2022; 324: 124758. This paper analyzes the role of hydrogen production in promoting low-carbon hydrogen reduction steelmaking systems in solar-rich regions. A scheduling method based on hourly plant operations is proposed to reduce grid emissions and costs by integrating low-cost solar photovoltaic power and hydrogen storage technology, thereby promoting the widespread application of low-carbon steelmaking technology.

[0009] In addition, the literature [6]: Alexandra Devlin, Aidong Yang. Regional supply chains for decarbonizing steel: Energy efficiency and green premium mitigation. Energy Conversion and Management 2022; 254: 115-268. explored the integration of steel production and renewable energy power generation systems. Existing research lacks consideration of the connection characteristics between the overall steel production steps, as well as analysis of the impact of subsequent production steps on hydrogen balance and steel production process scheduling. Summary of the Invention

[0010] In order to effectively solve the technical problems of high electricity costs and low control flexibility in hydrogen reduction steel plants, the present invention provides a load optimization scheduling method in the hydrogen reduction steel production process considering renewable energy. While ensuring the lowest production cost for steel enterprises, it also improves the absorption rate of renewable energy, providing a basis for accurate and reliable demand response potential assessment of steel enterprises.

[0011] The technical solution adopted by the present invention is:

[0012] A load optimization scheduling method for a hydrogen reduction steel production process considering renewable energy includes the following steps:

[0013] Step 1: Propose a matrix connection strategy for equipment start and stop between production steps;

[0014] Step 2: Analyze the load operation mechanism of steel production equipment in hydrogen reduction steel plants and establish a load control model for steel production equipment in hydrogen reduction steel plants;

[0015] Step 3: Analyze the electricity-hydrogen production and consumption coupling relationship in the steel production of hydrogen reduction steel plants, and construct a load optimization scheduling model for steel production equipment in hydrogen reduction steel plants considering renewable energy.

[0016] The step 1 comprises the following steps:

[0017] Step 1.1: Classify hydrogen reduction steel production equipment into two types: solid-state steel-molten steel interaction equipment and liquid-state steel-molten steel interaction equipment. Solid-state steel-molten steel interaction equipment is used to manufacture and process solid raw materials or products; liquid-state steel interaction equipment is used to manufacture and process liquid raw materials or products.

[0018] Step 1.2: Based on the flow shop scheduling architecture, construct a matrix representing the start and stop status of production equipment in the hydrogen reduction steel plant for each production step. Among them, j represents the production furnace, l represents the production step, and t represents the production time.

[0019] Step 1.3:

[0020] a: Construct production equipment startup constraints:

[0021] Considering factors such as product quality and production safety, each process in the hydrogen reduction steel production process cannot be interrupted after it starts, and it is a continuous load. Therefore, the processing time of each production process is constrained, as shown in Equations (1) to (3):

[0022]

[0023] Where, Ind1 represents the process start-up action state of each batch at time t; T l ope represents the period of time during which process 1 remains in operation; T l ra Indicates the rated production time of process l; It is a 0-1 variable that represents the production status of steel production batch j in production step l at time t-1.

[0024] b: Build production equipment end constraints:

[0025] Taking into account the production and transportation time of production equipment and the maximum waiting time of molten steel, the production equipment end constraints are set, as shown in Equations (4) to (7):

[0026]

[0027] Where, T wm Indicates the waiting time before molten steel enters the next process; Ind2 represents the production status of steel production batch j at the next production step l+1 during the time period τ; Ind2 represents the process shutdown status of each batch of steel at time t; EAF and AOD represent the production processes of electric arc furnace and argon oxygen decarburization furnace respectively; T wm,max represents the maximum waiting time of molten steel at room temperature; T represents the total time scale of the simulation.

[0028] c: Considering the strict sequence requirements of the production steps of the hydrogen reduction steel plant and the influence of the processing equipment of the hydrogen reduction steel plant on the connection between its products, the production step sequence constraint and the production equipment quantity constraint are constructed, as shown in Equation (8) and Equation (9):

[0029]

[0030]

[0031] Where, The production status of steel production batch j in the previous production step l-1 at time t; represents the rated production time of production step l-1; J represents the total number of batches of steel production tasks; M l Indicates the number of production equipment in process l.

[0032] The step 2 comprises the following steps:

[0033] Step 2.1: Analyze the equipment rated power, production power fluctuation and other factors in the hydrogen reduction steel plant to construct the power characteristics of different production equipment;

[0034] Considering the different power requirements of production equipment, set the production power P of production equipment at rated state in different production steps. l Its production power fluctuation δ l , then the production power of the equipment in production step 1 under rated conditions is P l ·δ l ;

[0035] Step 2.2: Combine the equipment start-stop matrix connection strategy between production steps obtained in step 1 and set the power P of different production equipment l Superimposed on the production equipment start and stop status matrix The steel production power P of the steel production line at each moment is obtained t Steel , as shown in formula (10):

[0036]

[0037] Where, P l represents the average power of the equipment in production step l; δ l Indicates the power fluctuation of the equipment in production step 1;

[0038] Step 2.3: Calculate the electricity cost of the steel production equipment in the hydrogen reduction steel plant based on the average power of each production step and the industrial peak and valley electricity prices:

[0039] First, the electricity consumption cost of the hydrogen reduction steel plant in each period is calculated based on the electricity consumption and industrial electricity price of each period. Second, the electricity cost of each period is added together to obtain the electricity cost of the hydrogen reduction steel plant for the entire day, as shown in formula (11):

[0040]

[0041] Where C Steel represents the electricity cost of steel production equipment in a steel enterprise; DT represents the length of each period; θ t represents the industrial electricity price in time period t.

[0042] Step 2.4: Based on the equipment start-stop matrix connection strategy between production steps proposed in Step 1 and the electricity cost calculation model for steel production in a hydrogen-reduced steel plant, a load control model for steel production equipment in a hydrogen-reduced steel plant is constructed. The optimal electricity cost is used as the objective function, and the steel production connection constraint and the load start-stop superposition constraint are used as constraints. The constructed model is shown below:

[0043] ①Objective function: formula (11);

[0044] ② Constraints: Equations (1) to (10).

[0045] The step 3 comprises the following steps:

[0046] Step 3.1: Based on the load control model of steel production equipment in hydrogen-reduced steel plants constructed in step 2, the electricity-hydrogen coupling characteristics are analyzed and a bypass electrolysis hydrogen production system model for hydrogen-based steel enterprises is constructed, as shown in Equations (12) to (14):

[0047]

[0048] Where HG t represents the hydrogen production in the period t; γ represents the energy conversion efficiency of hydrogen production in the electrolyzer; P t PtH represents the total power of the electrolytic hydrogen production system at time t; Indicates the unit calorific value of hydrogen; N indicates the number of single electrolyzers in the electrolyzer array, The electrolysis hydrogen production power of electrolyzer n in the electrolyzer array at time t; and Respectively represent the lower and upper limits of the power of each electrolytic cell n.

[0049] Step 3.2:

[0050] (1) Considering the cold start characteristics of the PEM electrolyzer, it requires a period of startup time during cold start. During this time, the production efficiency of the electrolyzer is low and can be ignored. Therefore, the cold start constraints of the electrolyzer are set as shown in Equations (15) to (17):

[0051]

[0052] Where, Ind3 represents the start / stop state of electrolytic cell n in the electrolytic cell array at time t; Ind4 represents the shutdown state of the electrolytic hydrogen production system; Indicates the cold start period of the electrolyzer;

[0053]

[0054] Where, Indicates the start and stop status of electrolytic cell n in the electrolytic cell array at time t-1; Represents the start and stop status of electrolytic cell n in the electrolytic cell array at time t.

[0055]

[0056] Where, Indicates the minimum cold start time of the electrolyzer;

[0057] (2) The hydrogen in the hydrogen reduction steel plant can be stored in a hydrogen storage tank to transfer the hydrogen production load, providing higher control flexibility for hydrogen-based steel production. Therefore, considering the configuration of an appropriate small-capacity hydrogen storage system for the hydrogen reduction steel plant, the constraints of the hydrogen storage system are constructed as shown in Equations (18) to (19):

[0058]

[0059] Where, represents the hydrogen reserve at time t; Indicates the hydrogen reserve at time t-1; HG t represents the hydrogen production of the electrolytic hydrogen production system at time t, Indicates the hydrogen consumption factor for steel production; SF represents the shaft furnace production step that primarily consumes hydrogen.

[0060]

[0061] Where HG sto,min and HG sto,max Respectively represent the lower and upper limits of hydrogen storage tank capacity;

[0062] (3) Considering the pressure requirement for hydrogen to be transported out of the tank, the pressure in the hydrogen tank should not be less than a threshold to ensure hydrogen transport efficiency. Therefore, the lower limit of the hydrogen tank storage capacity is shown in formula (20):

[0063]

[0064] Where, Pe min Indicates the minimum pressure inside the hydrogen storage tank; Vol and Tem respectively represent the volume of the hydrogen storage tank (10m 3 ) and internal temperature (294K); HR represents the hydrogen gas constant; Z represents the variable compressibility coefficient of hydrogen in the hydrogen storage tank, Z = (pressure inside the tank + pressure outside the tank) / 2; represents the molar amount of hydrogen.

[0065] (4) Considering renewable energy power generation and hydrogen production, photovoltaic power generation is used as the power generation output of renewable energy; considering electric hydrogen production, renewable energy power generation is first used, and then the grid output is used to make up for the hydrogen production gap. The constraints of renewable energy power generation and hydrogen production are shown in formula (21):

[0066] P t PtH,renewable -P t abandont +P t PtH,grid =P t PtH (twenty one);

[0067] Where, P t PtH,renewable is the output of distributed renewable energy configured by the electrolysis hydrogen production system, P t PtH,grid is the power output of the grid for hydrogen production by electrolysis, P t abandont is the amount of renewable energy load curtailment.

[0068] (5) Combining the above-mentioned renewable energy and grid hybrid hydrogen production system, considering the cost of hydrogen production from the grid for the electrolyzer, the cost of hydrogen production from renewable energy for the electrolyzer, and the cost of electricity production for steel production equipment, the total production cost of the hydrogen reduction steel plant is solved as shown in Equations (22) to (23):

[0069]

[0070] Where C PtH represents the electricity cost of the electrolysis hydrogen production system; P t PtH,grid represents the power purchased from the grid by the electrolysis hydrogen production system at that moment; DT represents the length of a single simulation time granularity; θ t represents the electricity price at time t; P t PtH,renewable Indicates the power drawn from the renewable energy system by the electrolysis hydrogen production system at that moment; t is the unit output cost of distributed renewable energy;

[0071] C=C Steel +C PtH (twenty three);

[0072] Where C represents the total cost of hydrogen reduction in steel mills.

[0073] Step 3.3: Combining the proposed load control model for steel production equipment in a hydrogen reduction steel plant, the electrolysis hydrogen production system model, the hydrogen storage system constraints, and the renewable energy power generation and hydrogen production constraints, a load optimization scheduling model for steel production equipment in a hydrogen reduction steel plant considering renewable energy is constructed as follows:

[0074] ①Objective function: Formula (23)

[0075] ② Constraints: Equations (1) to (10); (12) to (22).

[0076] The present invention provides a load optimization scheduling method in the hydrogen reduction steel production process considering renewable energy, and the technical effects are as follows: 1) Step 1 of the present invention constructs a production step start-stop matrix model based on the matrix 0-1 variable connection constraint. The model is completely linear and has strong scalability, and can be applied to solving various types of complex industrial production control problems.

[0077] 2) Step 2 of the present invention constructs a load control model for hydrogen reduction steel production equipment, performs refined simulation of the power load of a single production step and the power load, and superimposes them to form a production line load curve, which can be applied to multiple load control strategies such as production step scheduling transfer and equipment load control.

[0078] 3) Step 3 of the present invention constructs a load optimization scheduling model for hydrogen-reduced steel enterprises that takes renewable energy into consideration, taking into account the load regulation flexibility under the coordination of the electrolytic cell array, hydrogen storage system, and steel production system, and fully tapping the demand response potential of hydrogen-reduced steel plants, which can provide a reference for multiple parties such as power grid companies, load aggregators, and steel companies. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 This is a flow chart of the load optimization scheduling method of the present invention.

[0080] Figure 2 Multi-scenario simulation optimization results for hydrogen reduction steel plant. DETAILED DESCRIPTION

[0081] Load optimization scheduling method in hydrogen reduction steel production process considering renewable energy, such as Figure 1 As shown, the following steps are included:

[0082] Step 1: Propose a matrix connection strategy for equipment start-stop between production steps;

[0083] S1.1: Analyze the five energy-intensive steps involved in the iron ore processing process for hydrogen reduction steel production. The specific processes include: direct reduction, primary smelting, secondary metallurgy, continuous casting, and hot rolling.

[0084] Next, based on the physical state of the raw materials and intermediate products in each process step, hydrogen reduction steel production equipment is divided into two types: solid-molten steel interaction equipment and liquid-molten steel interaction equipment: Solid-molten steel interaction equipment: used for manufacturing and processing solid raw materials or products; Liquid-molten steel interaction equipment: used for manufacturing and processing liquid raw materials or products;

[0085] ① Solid-state molten steel interaction equipment: After the vertical furnace completes production, the iron ore is converted into solid sponge iron; after the continuous casting machine completes the initial casting step, the molten steel condenses and solidifies into steel billets. The solid-state physical properties of the product allow it to delay entering subsequent production steps, so the liquid steel interaction equipment has high scheduling flexibility.

[0086] ② Liquid steel interaction equipment: The steel processed in the electric arc furnace and argon oxygen decarburization furnace is still in a molten state. In order to prevent the molten steel from cooling and solidifying before entering the subsequent process, there are strict time constraints between adjacent processes. Therefore, the scheduling flexibility of the liquid steel interaction equipment is relatively low.

[0087] S1.2: By flexibly scheduling production equipment, peak loads can be reduced and production load transfer can be promoted, thereby improving the production flexibility of steel enterprises. Therefore, based on the flow shop scheduling architecture, a matrix representing the start and stop status of production equipment in hydrogen reduction steel plants is constructed for each production step. Among them, j represents the production furnace, l represents the production step, and t represents the production time.

[0088] Step 1.3:a: Construct production device launch constraints:

[0089] Considering factors such as product quality and production safety, each process in the hydrogen reduction steel production process cannot be interrupted after it starts, and it is a continuous load. Therefore, the processing time of each production process is constrained, as shown in Equations (1) to (3):

[0090]

[0091] Where, Ind1 represents the process start-up action state of each batch at time t; T l ope represents the period of time during which process 1 remains in operation; T l ra Indicates the rated production time of process l; It is a 0-1 variable that represents the production status of steel production batch j in production step l at time t-1.

[0092] b: Build production equipment end constraints:

[0093] Taking into account the production and transportation time of production equipment and the maximum waiting time of molten steel, the production equipment end constraints are set, as shown in Equations (4) to (7):

[0094]

[0095]

[0096] Where, T wm Indicates the waiting time before molten steel enters the next process; Ind2 represents the production status of steel production batch j at the next production step l+1 during the time period τ; Ind2 represents the process shutdown status of each batch of steel at time t; EAF and AOD represent the production processes of electric arc furnace and argon oxygen decarburization furnace respectively; T wm,max represents the maximum waiting time of molten steel at room temperature; TT represents the total time scale of the simulation.

[0097] c: Considering the strict sequence requirements of the production steps of the hydrogen reduction steel plant and the influence of the processing equipment of the hydrogen reduction steel plant on it, the production step sequence constraint and the production equipment quantity constraint are constructed, as shown in Equation (8) and Equation (9):

[0098]

[0099] Where, At time t, the production status of steel production batch j in the previous production step l-1; represents the rated production time of production step l-1; J represents the total number of batches of steel production tasks, M l Indicates the number of production equipment in process l.

[0100] Step 2: Analyze the load operation mechanism of the steel production equipment in the hydrogen reduction steel plant and establish a load control model for the steel production equipment in the hydrogen reduction steel plant, including the following steps:

[0101] S2.1: Analyze the equipment rated power, production power fluctuations and other factors in hydrogen reduction steel plants, and construct power characteristics for different production equipment;

[0102] Considering the different power requirements of production equipment, set the production power P of production equipment at rated state in different production steps. l Its production power fluctuation δ l , then the production power of the equipment in production step 1 under rated conditions is P l ·δ l .

[0103] S2.2: Combine the equipment start-stop matrix connection strategy between production steps proposed in step 1 to convert the power P of different production equipment into l Superimposed on the production equipment start and stop status matrix The steel production power P of the steel production line at each moment is obtained t Steel , as shown in formula (10):

[0104]

[0105] Where, P l represents the average power of the equipment in production step l; δ lIndicates the power fluctuation of the equipment in production step 1.

[0106] S2.3: Based on the obtained average power of each production step and the industrial peak and valley electricity prices, calculate the electricity cost of the steel production equipment in the hydrogen reduction steel plant:

[0107] First, the electricity consumption cost of the hydrogen reduction steel plant in each period is calculated based on the electricity consumption and industrial electricity price of each period. Second, the electricity cost of each period is added together to obtain the electricity cost of the hydrogen reduction steel plant for the entire day, as shown in formula (11):

[0108]

[0109] Where C Steel represents the electricity cost of steel production equipment in a steel enterprise; DT represents the length of each period; θ t represents the industrial electricity price in time period t.

[0110] S2.4: Based on the equipment start-stop matrix connection strategy between production steps in step 1 and the electricity cost calculation model for steel production in hydrogen reduction steel plants, a load control model for steel production equipment in hydrogen reduction steel plants is constructed. The optimal electricity cost is used as the objective function, and the steel production connection constraint and the load start-stop superposition constraint are used as constraints. The constructed model is shown below:

[0111] ①Objective function: formula (11);

[0112] ② Constraints: Equations (1) to (10).

[0113] Step 3: Analyze the electricity-hydrogen production and consumption coupling relationship in the steel production of the hydrogen reduction steel plant, and construct a load optimization scheduling model for the steel production equipment of the hydrogen reduction steel plant considering renewable energy; including the following steps:

[0114] S3.1: Based on the actual technology of existing hydrogen reduction steel production, and considering the characteristics of hydrogen that is difficult to transport and cannot be stored in large quantities, hydrogen-based steel enterprises often use bypass electrolysis hydrogen production equipment to electrolyze water to produce hydrogen. Therefore, based on the load control model of steel production equipment in hydrogen reduction steel plants constructed in step 2, the electricity-hydrogen coupling characteristics are analyzed to construct a bypass electrolysis hydrogen production system model for hydrogen-based steel enterprises, as shown in Equations (12) to (14):

[0115]

[0116] Where HG t represents the hydrogen production in the period t; γ represents the energy conversion efficiency of hydrogen production in the electrolyzer; P t PtH represents the total power of the electrolytic hydrogen production system at time t, Indicates the unit calorific value of hydrogen; N indicates the number of single electrolyzers in the electrolyzer array, The electrolysis hydrogen production power of electrolyzer n in the electrolyzer array at time t. and Respectively represent the lower and upper limits of the power of each electrolytic cell n.

[0117] S3.2: (1) Considering the cold start characteristics of the PEM electrolyzer, it requires a period of startup time during cold start. During this time, the production efficiency of the electrolyzer is low and can be ignored. Therefore, the cold start constraints of the electrolyzer are set as shown in Equations (15) to (17):

[0118]

[0119] Where, Ind3 represents the start / stop state of electrolytic cell n in the electrolytic cell array at time t; Ind4 represents the shutdown state of the electrolytic hydrogen production system; Indicates the cold start period of the electrolyzer;

[0120]

[0121] Where, Indicates the start and stop status of electrolytic cell n in the electrolytic cell array at time t-1; Represents the start and stop status of electrolytic cell n in the electrolytic cell array at time t.

[0122]

[0123] Where, Indicates the minimum cold start time of the electrolyzer.

[0124] (2) The hydrogen in the hydrogen reduction steel plant can be stored in a hydrogen storage tank to transfer the hydrogen production load, providing higher control flexibility for hydrogen-based steel production. Therefore, considering the configuration of an appropriate small-capacity hydrogen storage system for the hydrogen reduction steel plant, the constraints of the hydrogen storage system are constructed as shown in Equations (18) to (19):

[0125]

[0126] Where, represents the hydrogen reserve at time t; Indicates the hydrogen reserve at time t-1; HG t represents the hydrogen production of the electrolytic hydrogen production system at time t, Indicates the hydrogen consumption factor for steel production; SF represents the shaft furnace production step that primarily consumes hydrogen.

[0127]

[0128] Where HG sto,min and HGsto,max Respectively represent the lower and upper limits of hydrogen storage tank capacity;

[0129] (3) Considering the pressure requirement for hydrogen to be transported out of the tank, the pressure in the hydrogen tank should not be less than a threshold to ensure hydrogen transport efficiency. Therefore, the lower limit of the hydrogen tank storage capacity is shown in formula (20):

[0130]

[0131] Where, Pe min Indicates the minimum pressure inside the hydrogen storage tank; Vol and Tem respectively represent the volume of the hydrogen storage tank (10m 3 ) and internal temperature (294K); HR represents the hydrogen gas constant; Z represents the variable compressibility coefficient of hydrogen in the hydrogen storage tank, Z = (pressure inside the tank + pressure outside the tank) / 2; represents the molar amount of hydrogen.

[0132] (4) Considering renewable energy power generation and hydrogen production, photovoltaic power generation is used as the power generation output of renewable energy; considering electric hydrogen production, renewable energy power generation is first used, and then the grid output is used to make up for the hydrogen production gap. The constraints of renewable energy power generation and hydrogen production are shown in formula (21):

[0133] P t PtH,renewable -P t abandont +P t PtH,grid =P t PtH (twenty one);

[0134] Where, P t PtH,renewable is the output of distributed renewable energy configured by the electrolysis hydrogen production system, P t PtH,grid is the power output of the grid for hydrogen production by electrolysis, P t abandont is the amount of renewable energy load curtailment.

[0135] (5) Combining the above-mentioned renewable energy and grid hybrid hydrogen production system, considering the cost of hydrogen production from the grid for the electrolyzer, the cost of hydrogen production from renewable energy for the electrolyzer, and the cost of electricity production for steel production equipment, the total production cost of the hydrogen reduction steel plant is solved as shown in Equations (22) to (23):

[0136]

[0137] Where C PtH represents the electricity cost of the electrolysis hydrogen production system; P t PtH,gridrepresents the power purchased from the grid by the electrolysis hydrogen production system at that moment; DT represents the length of a single simulation time granularity; θ t represents the electricity price at time t; P t PtH,renewable Indicates the power drawn from the renewable energy system by the electrolysis hydrogen production system at that moment; t is the unit output cost of distributed renewable energy;

[0138] C=C Steel +C PtH (twenty three);

[0139] Where C represents the total cost of hydrogen reduction in steel mills.

[0140] S3.3: Combining the proposed load control model for steel production equipment in a hydrogen reduction steel plant, the electrolysis hydrogen production system model, the hydrogen storage system constraints, and the renewable energy power generation and hydrogen production constraints, a load optimization scheduling model for steel production equipment in a hydrogen reduction steel plant considering renewable energy is constructed as follows:

[0141] ①Objective function: Formula (23)

[0142] ② Constraints: Equations (1) to (10); (12) to (22).

[0143] In order to verify the correctness of the load optimization scheduling method in the hydrogen reduction steel production process considering renewable energy, the following scenario simulation was established. The simulation experiment was carried out using the MATLAB platform combined with the YALMIP toolbox to call the GUROBI solver. The simulation scenario parameters are shown in Table 1, and the simulation optimization results are shown in Table 1. Figure 2 shown.

[0144] Depend on Figure 2 As can be seen, in the four simulation scenarios, the total capacity of the electrolyzer array of the hydrogen production system of the hydrogen reduction steel plant is adjusted to (A) 20 MW, (B) 25 MW, (C) 30 MW, and (D) 35 MW, corresponding to the configuration of (A) 8, (B) 10, (C) 12, and (D) 14 large electrolyzers, respectively.

[0145] like Figure 2 As can be seen from sub-figure A, when the total capacity of the electrolyzer array is 20MW, the control strategy proposed in the present invention fully utilizes the control flexibility of the electrolysis hydrogen production system during the peak electricity price period and reduces the proportion of grid electricity purchase for the electrolysis hydrogen production system.

[0146] like Figure 2 As can be seen from sub-figures B and C, as the total capacity of the electrolyzer array increases, the control strategy proposed in the present invention will gradually stop purchasing electricity from the power grid to produce hydrogen during peak electricity price periods and completely adopt green electricity to produce hydrogen; while further reducing costs, it will make full use of the flexibility of hydrogen production and consumption and the flexibility of production step scheduling to improve production efficiency.

[0147] like Figure 2 As can be seen from sub-figure D, when the total capacity of the electrolyzer array is 35MW, the control strategy proposed in the present invention can achieve zero grid electricity purchase during peak electricity price periods, and completely use green electricity to produce hydrogen; and utilize the storage characteristics of the hydrogen storage tank to transfer the grid hydrogen production load to the valley electricity price period, fully tapping the load flexibility potential of the hydrogen reduction steel plant and realizing the optimal low-carbon economic scheduling of the hydrogen reduction steel plant.

[0148] Table 1 Parameters of hydrogen reduction steel plant production simulation scenario

[0149]

[0150] It can be seen from the simulation results that the load optimization scheduling method for the hydrogen reduction steel production process considering renewable energy proposed in the present invention has corresponding flexibility, and can flexibly schedule flexible load-side resources such as electrolytic cells, hydrogen storage tanks, and steel production equipment within hydrogen reduction steel enterprises, and flexibly interact with source-side renewable energy power generation and grid power generation, so as to fully tap the production regulation potential, improve the transferability of electrolytic hydrogen production load, effectively absorb renewable energy and optimize the overall production cost of steel enterprises.

Claims

1. A method for optimizing load scheduling in a hydrogen reduction steel production process using renewable energy, characterized in that The following steps are involved: Step 1: Propose a matrix connection strategy for equipment start and stop between production steps; Step 2: Analyze the load operation mechanism of steel production equipment in hydrogen reduction steel plants and establish a load control model for steel production equipment in hydrogen reduction steel plants; Step 3: Analyze the electricity-hydrogen production and consumption coupling relationship in the steel production of hydrogen reduction steel plants, and construct a load optimization scheduling model for steel production equipment in hydrogen reduction steel plants considering renewable energy; The step 2 comprises the following steps: Step 2.1: Analyze the rated power of equipment in the hydrogen reduction steel plant, the factors affecting production power fluctuations, and construct power characteristics for different production equipment; Considering the different power requirements of production equipment, set the production steps of different production steps under the rated state of production equipment The average power of the equipment is Power fluctuation value of equipment in its production steps , then the production steps The production power of the equipment under rated conditions is ; Step 2.2: Combine the equipment start-stop matrix connection strategy between production steps obtained in step 1 and set the power of different production equipment Superimposed on the production equipment start and stop status matrix Get the steel production efficiency of the steel production line at every moment , as shown in formula (10): （10）； Where, Indicates production steps Average power of the device; Indicates production steps Power fluctuations in the equipment; Step 2.3: Calculate the electricity cost of the steel production equipment in the hydrogen reduction steel plant based on the average power of each production step and the industrial peak and valley electricity prices: First, the electricity consumption cost of the hydrogen reduction steel plant in each period is calculated based on the electricity consumption and industrial electricity price in each period. Second, the electricity consumption cost of each period is added together to obtain the electricity cost of the hydrogen reduction steel plant for the entire day, as shown in formula (11): （11）； Where, represents the electricity cost of steel production equipment of steel enterprises; Indicates the length of each period; Indicates time period industrial electricity prices; Step 2.4: Based on the equipment start-stop matrix connection strategy between production steps proposed in Step 1 and the electricity cost calculation model for steel production in the hydrogen reduction steel plant, a load control model for steel production equipment in the hydrogen reduction steel plant is constructed, with the optimal electricity cost as the objective function and the steel production connection constraint and the load start-stop superposition constraint as the constraint conditions; The step 3 comprises the following steps: Step 3.1: Based on the load control model of steel production equipment in hydrogen-reduced steel plants constructed in step 2, the electricity-hydrogen coupling characteristics are analyzed and a bypass electrolysis hydrogen production system model for hydrogen-based steel enterprises is constructed, as shown in Equations (12) to (14): （12）； （13）； （14）； Where, represents the hydrogen production during period t; Indicates the energy conversion efficiency of hydrogen production in electrolyzer; Indicates time Total power of the electrolysis hydrogen production system; Indicates the unit calorific value of hydrogen; Indicates the number of individual electrolytic cells in the electrolytic cell array, Electrolyzers in an electrolyzer array At the moment The electrolysis hydrogen production power; and Represents each electrolytic cell separately The lower and upper power limits; Step 3.2: (1) Set the cold start constraints of the electrolyzer as shown in Equations (15) to (17): （15）； Where, Represents an electrolyzer in an electrolyzer array At the moment Start and stop status; Indicates the shutdown status of the electrolysis hydrogen production system; Indicates the cold start period of the electrolyzer; （16）； Where, Represents an electrolyzer in an electrolyzer array At the moment Start and stop status; Represents an electrolyzer in an electrolyzer array At the moment Start and stop status; （17）； Where, Indicates the minimum cold start time of the electrolyzer; (2) Considering the configuration of a small-capacity hydrogen storage system in a hydrogen reduction steel plant, the constraints of the hydrogen storage system are constructed as shown in Equations (18) to (19): （18）； Where, represents the hydrogen reserve at time t; express The hydrogen reserve at the time; express The hydrogen production of the electrolysis hydrogen production system at any moment, represents the hydrogen consumption coefficient for steel production; Indicates the shaft furnace production step that mainly consumes hydrogen; （19）； Where, and Respectively represent the lower and upper limits of hydrogen storage tank capacity; (3) Considering the pressure requirement for hydrogen to be transported out of the tank, the pressure in the hydrogen tank should not be less than a threshold to ensure hydrogen transport efficiency. Therefore, the lower limit of the hydrogen tank storage capacity is shown in formula (20): （20）； Where, Indicates the minimum gas pressure inside the hydrogen storage tank; and represent the volume and internal temperature of the hydrogen storage tank respectively; represents the hydrogen gas constant; Indicates the variable compression coefficient of hydrogen in the hydrogen storage tank, (pressure inside the tank + pressure outside the tank) / 2; represents the molar amount of hydrogen; (4) Considering renewable energy power generation and hydrogen production, photovoltaic power generation is used as the power generation output of renewable energy; considering electric hydrogen production, renewable energy power generation is first used, and then the grid output is used to make up for the hydrogen production gap. The constraints of renewable energy power generation and hydrogen production are shown in formula (21): （21）； Where, It is the output of distributed renewable energy configured by the electrolysis hydrogen production system. It is the power output of the power grid used for hydrogen production by electrolysis. is the amount of renewable energy load curtailment; (5) Combining the above-mentioned renewable energy and grid hybrid hydrogen production system, considering the cost of purchasing electricity from the grid for hydrogen production by the electrolyzer, the cost of renewable energy for hydrogen production by the electrolyzer, and the cost of purchasing electricity for production of steel production equipment, the total production cost of the hydrogen reduction steel plant is solved as shown in Equations (22) to (23): （22）； Where, represents the electricity cost of the electrolysis hydrogen production system; Indicates the power purchased by the electrolysis hydrogen production system from the grid at that moment; Indicates the length of a single simulation time granularity; Indicates time electricity prices; Indicates the power drawn from the renewable energy system by the electrolysis hydrogen production system at that moment; is the unit output cost of distributed renewable energy; （23）； Where, represents the total cost of hydrogen reduction steel plant; Step 3.3: Combine the proposed hydrogen reduction steel plant steel production equipment load control model, electrolysis hydrogen production system model, hydrogen storage system constraints, and renewable energy power generation hydrogen production constraints to construct a hydrogen reduction steel plant steel production equipment load optimization scheduling model considering renewable energy.

2. The method for optimizing load scheduling in a hydrogen reduction steel production process taking renewable energy into consideration according to claim 1, characterized in that: The step 1 comprises the following steps: Step 1.1: Classify hydrogen reduction steel production equipment into two types: solid-state steel-molten steel interaction equipment and liquid-state steel-molten steel interaction equipment. Solid-state steel-molten steel interaction equipment is used to manufacture and process solid raw materials or products; liquid-state steel interaction equipment is used to manufacture and process liquid raw materials or products. Step 1.2: Based on the flow shop scheduling architecture, construct a matrix representing the start and stop status of production equipment in the hydrogen reduction steel plant for each production step. ,in, Represents the production heat, Represents the production steps, represents the moment of production; Step 1.3: a: Construct production equipment startup constraints: Considering product quality and production safety factors, each process in the hydrogen reduction steel production process cannot be interrupted after it starts, and it is a continuous load. Therefore, the processing time of each production process is constrained, as shown in Equations (1) to (3): （1）； （2）； （3）； Where, Indicates that each batch is at time The process start action status; Representation process the period of operation; Indicates the rated production time of process l; Is a 0-1 variable, indicating that Moment, steel production batch In the production step Production status on b: Build production equipment end constraints: Taking into account the production and transportation time of production equipment and the maximum waiting time of molten steel, the production equipment end constraints are set, as shown in Equations (4) to (7): （4）； （5）； （6）； （7）； Where, Indicates the waiting time before molten steel enters the next process; Indicates imminent During the period, steel production batches In the next production step Production status on Indicates that each batch of steel is at time The process shutdown state; EAF and AOD represent the production processes of electric arc furnace and argon oxygen decarburization furnace respectively; Indicates the maximum waiting time of molten steel at room temperature; represents the total time scale of the simulation; c: Considering the strict sequence requirements of the production steps of the hydrogen reduction steel plant and the influence of the processing equipment of the hydrogen reduction steel plant on the connection between its products, the production step sequence constraint and the production equipment quantity constraint are constructed, as shown in Equation (8) and Equation (9): （8）； （9）； Where, At the moment Steel production batches In the previous production step Production status on Indicates production steps Rated production time; Indicates the total number of batches of steel production tasks; Representation process The number of production equipment in.

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