Island energy system optimization scheduling method considering electricity-to-ammonia waste heat power generation

Abstract

The invention provides an island energy system optimization scheduling method considering ammonia-to-electricity waste heat power generation, and the method employs an independent island integrated energy system containing an ammonia-to-electricity system to execute a weekly-day-intra-day multi-stage operation optimization scheduling strategy, and the independent island integrated energy system is a system considering the ammonia supply demand. Wind energy and solar energy are used as energy input, energy is supplied to seawater desalination equipment and an electricity-to-ammonia system, and the electric load requirements of island residents are met; meanwhile, seawater desalination equipment is used as a power demand response resource to increase the water-energy coupling relationship of the system model, and cross-time storage and utilization of fresh water resources are realized through a reservoir, so that an ammonia-hydrogen power ship which is used for meeting daily travel demands of island residents is used as an ammonia load; an electricity-to-ammonia system and an ammonia storage tank are adopted to realize effective consumption of island wind and light resources; according to the invention, the long-period energy supply reliability of the island can be improved, and the problem of uncertainty of wind energy and light energy resources of the island can be effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated energy systems, and in particular to an optimized scheduling method for an island energy system considering power-to-ammonia waste heat power generation. Background Art

[0002] Islands are usually far from the mainland and it is difficult to connect to the external power grid, which poses challenges to the energy supply of the islands. At the same time, traditional diesel power generation will incur high fuel costs and environmental pollution problems, which will limit the sustainable development of the islands. Therefore, constructing an independent island integrated energy system using the rich renewable energy resources on the islands has become one of the important solutions for countries to develop islands.

[0003] Energy storage technology is one of the effective ways to improve the consumption capacity and operation reliability of renewable energy on islands. Electrochemical energy storage technology has the characteristics of high conversion efficiency, fast response speed, easy installation, etc., and has been widely used. The energy supply of independent islands has output characteristics such as randomness, volatility and intermittency, and it is necessary to use the flexible resources of the system to ensure the balance between supply and demand. However, electrochemical energy storage can only meet short-term flexibility needs, and frequent charging and discharging will reduce its service life, making it difficult to ensure the long-term reliable operation of the system. Therefore, it is urgent to explore long-cycle energy storage technologies more suitable for islands. With the gradual maturity of the electrolytic water hydrogen production technology, using hydrogen for long-term large-scale energy storage can effectively promote the consumption of wind and light on the islands and improve the operation reliability of the system. However, hydrogen can only be compressed or liquefied under high pressure (30 - 70 MPa) or low temperature (-250 °C), which is inconvenient for storage and transportation, and hydrogen is flammable and explosive.

[0004] Ammonia has low carbon compared with traditional fossil fuels, and compared with hydrogen, it has the characteristics of easy liquefaction, high energy density, convenient storage and transportation, and high safety. In addition, ammonia is a hydrogen-rich compound, and the hydrogen-ammonia fusion technology using ammonia as a hydrogen storage medium is an effective technical means to realize the safe and efficient utilization of hydrogen energy, and is currently becoming a hot spot in energy development. As an important means of transportation for island residents' daily travel, ammonia-hydrogen powered ships are expected to become an important development direction for future marine transportation vehicles. In addition, liquid ammonia can be used as a refrigerant to quickly freeze and preserve the seafood caught by island residents. Therefore, combining the ammonia demand situation on the islands and constructing an independent island integrated energy system including an electro-ammonia conversion process is one of the effective ways to promote the multi-scenario application of green ammonia.

[0005] Compared with the traditional Haber-Bosch method for synthesizing ammonia, the power-to-ammonia technology only changes in the upstream hydrogen production link, using "green hydrogen" instead of "gray hydrogen" to synthesize ammonia, which will significantly promote the consumption of renewable energy and is more low-carbon. Waste heat power generation technology is one of the commonly used energy-saving and consumption-reducing measures in the ammonia synthesis process. Further research is still needed on the coupled modeling of the overall process of electrolytic water hydrogen production - ammonia synthesis - waste heat recovery in the power-to-ammonia system.

[0006] In addition, with the continuous development of the integrated energy system on islands, its optimal scheduling problem has received extensive attention. However, the integrated energy system on independent islands usually relies on renewable resources for energy supply. Such resources are uncertain, and it is difficult to cope with energy shortages in a longer time range in the future based on the day-ahead scheduling framework alone, which is not conducive to the reliable operation of the system. In addition, the power prediction accuracy for a long period is relatively low. If the long-term source-load uncertainty is directly processed and an optimal scheduling model based on the predicted power for multiple days in the future is established, it is difficult to formulate a reliable scheduling plan. Therefore, by combining the long-cycle energy storage advantage of ammonia energy and dealing with the optimal scheduling problem of the island integrated energy system from the perspective of long-short cycle coordination, the problems brought by large long-term power prediction errors can be effectively addressed, and the long-term energy supply and demand problem on the island can be alleviated.

[0007] Based on this, the present invention proposes an optimal scheduling method for an island energy system considering power generation from the waste heat of power-to-ammonia. Summary of the Invention

[0008] The present invention proposes an optimal scheduling method for an island energy system considering power generation from the waste heat of power-to-ammonia, which can improve the long-cycle energy supply reliability of the island and effectively address the uncertainty problems of wind and solar energy resources on the island.

[0009] The present invention adopts the following technical solutions.

[0010] An optimal scheduling method for an island energy system considering power generation from the waste heat of power-to-ammonia is used to improve the long-cycle energy supply reliability of the island and effectively address the uncertainty problems of wind and solar resources on the island. The method adopts an independent island integrated energy system with a power-to-ammonia system to implement a multi-stage operation optimization scheduling strategy of week-ahead - day-ahead - intra-day. The independent island integrated energy system is a system that takes into account the ammonia supply demand. It uses wind energy and solar energy as energy inputs to supply energy to the seawater desalination equipment and the power-to-ammonia system, and meets the electrical load demand of island residents. At the same time, the seawater desalination equipment is used as a power demand response resource to increase the water-energy coupling relationship of the system model, and the cross-time storage and utilization of fresh water resources are realized through a reservoir. The ammonia-hydrogen powered ship used to meet the daily travel needs of island residents is used as an ammonia load, and the power-to-ammonia system and ammonia storage tank are used to effectively absorb the wind and solar resources on the island.

[0011] The power-to-ammonia system is based on the establishment of a power-to-ammonia system model considering the waste heat power generation unit, including an ammonia synthesis unit, a waste heat power generation unit, a water electrolysis hydrogen production unit, and an air separation nitrogen production unit. When the system operates, hydrogen and nitrogen from the water electrolysis hydrogen production unit and the air separation nitrogen production unit are mixed as the feed gas, pressurized by a compressor to the pressure required for ammonia synthesis reaction, and then enter the ammonia synthesis tower after being heated by a preheater; under the conditions of high temperature and high pressure, the compressed feed gas reacts through a reactor equipped with a catalyst. The reaction gas at the outlet of the ammonia synthesis tower first enters the waste heat boiler of the waste heat power generation unit, and after heat recovery by the waste heat boiler, it enters the refrigeration system through further heat exchange by a heat exchanger; the refrigeration system liquefies ammonia gas and sends it to a separator to improve the purity of liquid ammonia; the separator is used for the effective separation of liquid and gaseous substances, and the uneffectively cooled ammonia gas will re-enter the refrigeration system; in the refrigeration system, the unreacted nitrogen and hydrogen mixed gas needs to be recycled to improve the conversion rate of ammonia synthesis. In the model, each unit is expressed by the following formulas:

[0012] (1) Ammonia synthesis unit

[0013]

[0014] In the formula, is the ammonia production rate; is the ammonia production rate ramp rate; and are the upper and lower limits of the ammonia production rate ramp rate; and are the upper and lower limits of the ammonia production rate respectively; is the energy consumption of the ammonia synthesis unit; is the electric energy consumed per unit mass of ammonia produced.

[0015] (2) Waste heat power generation unit

[0016]

[0017]

[0018] In the formula, is the heat recovered by the waste heat boiler; M A is the average flow rate of the gas at the outlet of the ammonia synthesis tower per unit mass of ammonia produced; C p is the average specific heat capacity of the gas at the outlet of the ammonia synthesis tower; T1 is the average temperature of the gas at the inlet of the waste heat boiler; T2 is the average temperature of the gas at the outlet of the waste heat boiler; is the by-product steam quantity of the waste heat boiler; η sun is the heat loss rate of the waste heat boiler; H1 is the enthalpy value of the high-pressure steam generated by the waste heat boiler; H2 is the enthalpy value of the hot water of the waste heat boiler; is the generated electric power of the waste heat power generation unit; η Gis the thermoelectric conversion efficiency of the steam turbine; τ is the electrothermal conversion coefficient.

[0019] (3) Hydrogen production unit by electrolyzing water

[0020]

[0021] In the formula, is the hydrogen production of the electrolyzer; η EL is the electro-hydrogen conversion efficiency of the electrolyzer; P t EL is the power of the electrolyzer; is the lower calorific value of hydrogen; Δt is the scheduling step; and are the upper and lower limits of the operating power of the electrolyzer respectively. V t HST is the storage capacity of the hydrogen buffer tank; and are the storage and release efficiencies of the hydrogen buffer tank respectively; is the outlet flow of the hydrogen buffer tank, which is related to the ammonia synthesis rate; is the amount of hydrogen consumed to produce a unit mass of ammonia; and are the upper and lower limits of the storage capacity of the hydrogen buffer tank respectively; is the hydrogen compression energy consumption; is the molar mass of hydrogen; R is the ideal gas constant; T3 is the working temperature of compressor c1; p2 and p1 are the pressures at the inlet and outlet of compressor c1 respectively; η c1 is the working efficiency of compressor c1; are the hydrogen storage amounts at the beginning and end of each day in the hydrogen buffer tank respectively.

[0022] (4) Air separation unit for nitrogen production

[0023] P t AS =[(F t Air / M Air )RT4ln(p4 / p3)] / η c2

[0024]

[0025] In the formula, P t AS is the energy consumption of the air separation unit for nitrogen production; F t Air is the air injection amount of the air separation unit for nitrogen production; M Air is the molar mass of air; R is the ideal gas constant; T4 is the working temperature of compressor c2; p4 and p3 are the pressures at the inlet and outlet of compressor c2 respectively; η c2is the working efficiency of compressor c2; η AS is the conversion efficiency of the air separation device; is the amount of nitrogen produced by the air separation nitrogen production unit, which is equal to the amount of nitrogen required by the ammonia synthesis unit; is the volume fraction of nitrogen in the air; is the amount of nitrogen consumed to produce a unit mass of ammonia.

[0026] In the multi-stage operation optimization scheduling strategy of week-ahead - day-ahead - hour-ahead, the objective function in the week-ahead scheduling stage is expressed as: F1 = min(C q + C om + C ramp )

[0027] In the formula, F1 is the total system operation cost in the week-ahead stage; C q is the cost of abandoned wind and solar energy; C om is the operation and maintenance cost; C ramp is the ammonia production rate ramp penalty cost of the power-to-ammonia system.

[0028] Among them, the cost of abandoned wind and solar energy, the operation and maintenance cost, and the ammonia production rate ramp penalty cost of the power-to-ammonia system are specifically expressed as follows:

[0029]

[0030] In the formula, ζ q is the unit cost of abandoned wind and solar energy; P t WT,pre and P t PV,pre are the predicted output values of wind power and photovoltaic power respectively; P t WT and P t PV are the actual consumption amounts of wind power and photovoltaic power respectively; C des is the operation and maintenance cost of the seawater desalination equipment; C P2A is the operation and maintenance cost of the power-to-ammonia system; ζ des is the unit operation and maintenance cost of the seawater desalination equipment; ζ NH3,WH is the unit operation and maintenance cost of the waste heat power generation unit of the power-to-ammonia system; is the unit operation and maintenance cost of the ammonia synthesis unit, electrolytic water hydrogen production unit and air separation nitrogen production unit of the power-to-ammonia system; ζ ramp is the ammonia production rate ramp penalty coefficient.

[0031] The constraint conditions in the week-ahead scheduling stage include the constraints related to the power-to-ammonia system, the constraints of other equipment, and the power balance constraints. Among them, the constraints of other equipment and the power balance constraints are shown in the following formulas:

[0032] (1) Seawater desalination equipment constraint

[0033] Pt des = GV t des / Δt

[0034]

[0035] Wherein, P t des is the electric power of the seawater desalination equipment; G is the specific energy consumption of water production of the seawater desalination equipment; V t des is the water production volume of the seawater desalination equipment; and are respectively the upper and lower limits of the power of the seawater desalination equipment.

[0036] (2) Reservoir constraint

[0037]

[0038] Wherein, V t res is the water storage capacity of the reservoir; V t res,in and V t res,out are the water inflow and outflow of the reservoir; and are respectively the upper and lower limits of the water storage capacity of the reservoir; V res,in,max and V res,in,min are respectively the maximum and minimum values of the water inflow of the reservoir; V res,out,max and V res,out,min are respectively the maximum and minimum values of the water outflow of the reservoir; is a 0-1 variable. When is the water inflow of the reservoir, and when is the water outflow of the reservoir; are respectively the water storage capacities of the reservoir at the beginning and end of each day.

[0039] (3) Ammonia storage tank constraint

[0040]

[0041] Wherein, is the storage volume of the ammonia storage tank; and are respectively the storage efficiencies of the ammonia storage tank; and are respectively the ammonia inflow and outflow of the ammonia storage tank; and are respectively the upper and lower limits of the storage volume of the ammonia storage tank; and are respectively the maximum and minimum values of the ammonia inflow of the ammonia storage tank; m AST,out,max and mAST,out,min They are the maximum and minimum ammonia output amounts of the ammonia storage tank respectively; is a 0-1 variable. When the ammonia storage tank stores ammonia, when the ammonia storage tank discharges ammonia.

[0042] (4) Wind and solar power output constraints

[0043] 0 ≤ P t WT ≤ P t WT,pre

[0044] 0 ≤ P t PV ≤ P t PV,pre

[0045] In the formula, P t WT and P t PV are the actual consumption amounts of wind power and photovoltaic power respectively; P t WT,pre and P t PV,pre are the predicted output values of wind power and photovoltaic power respectively.

[0046] (5) Power balance constraints

[0047] V t des -V t res,in +V t res,out =V t load

[0048]

[0049] In the formula, V t des is the water production volume of the seawater desalination equipment; V t res,in and V t res,out are the water inflow and outflow volumes of the reservoir; V t load is the predicted value of water load demand; P t L is the predicted value of electric load demand; P t des is the electric power of the seawater desalination equipment; P t P2A is the net energy consumption of the power-to-ammonia system; and are the ammonia inflow and outflow volumes of the ammonia storage tank respectively; is the predicted value of ammonia load demand.

[0050] In the multi-stage operation optimization scheduling strategy of week-ahead - day-ahead - hour-ahead, the objective function in the day-ahead scheduling stage is expressed as: F2 = min(C q + C om + C ramp + C NH3,loss + C s,AST )

[0051] In the formula, F2 is the total system operation cost in the day-ahead stage; is the ammonia load loss cost; C s,AST is the penalty cost for ammonia storage deviation.

[0052] The ammonia load loss cost and the penalty cost for ammonia storage deviation in the objective function of the day-ahead scheduling stage are expressed as:

[0053]

[0054] In the formula, T2 is the number of time periods in the day-ahead scheduling stage, taking 24h; ζ loss is the unit ammonia load reduction penalty coefficient; is the amount of ammonia load reduced per unit time; ζ AST is the penalty coefficient for unit ammonia storage deviation; is the reference value of ammonia storage at the end of the day-ahead stage scheduling, that is, the ammonia storage level at the end of the first-day scheduling obtained in the week-ahead stage; is the actual ammonia storage at the end of each day's scheduling in the day-ahead scheduling stage.

[0055] In the multi-stage operation optimization scheduling strategy of week-ahead - day-ahead - hour-ahead, the day-ahead scheduling stage satisfies the corresponding operation constraints and system power balance constraints of the week-ahead scheduling stage; and part of the ammonia load is modeled as a load that can be reduced. The constraints related to ammonia load loss are as follows:

[0056]

[0057] In the formula, is the maximum total amount of ammonia load that can be reduced during the scheduling period; is the maximum amount of ammonia load that can be reduced per unit time.

[0058] In the multi-stage operation optimization scheduling strategy of week-ahead - day-ahead - hour-ahead, the objective function in the hour-ahead scheduling stage is expressed as:

[0059] In the formula, F3 is the total system operation cost in the hour-ahead stage; C p is the cost of adjusting the equipment output plan; C s is the cost of adjusting the storage deviation of the energy storage equipment; C s,resis the adjustment cost of the reservoir storage deviation;

[0060] In the intraday scheduling stage, the adjustment cost of the device output power plan, the adjustment cost of the energy storage device storage deviation, and the adjustment cost of the reservoir storage deviation in the objective function are expressed as:

[0061]

[0062] In the formula, l is the starting time of intraday rolling optimization; T3 is the number of time periods in the intraday scheduling stage, taking 4h; κ u is the unit power deviation penalty coefficient of device u, where device u includes electrolyzers, air separation nitrogen production equipment, and ammonia synthesis equipment in the power-to-ammonia system, as well as seawater desalination equipment; P t u,ref is the reference value of the output power of device u, that is, the output power of device u in the day-ahead stage; P t u is the output power of device u in the intraday scheduling; κ z is the unit storage deviation penalty coefficient of energy storage device z, where energy storage device z includes hydrogen buffer tanks and ammonia storage tanks; V t z,ref is the reference value of the storage of energy storage device z, that is, the storage of energy storage device z in the day-ahead stage; V t z is the storage of energy storage device z in the intraday stage; κ res is the unit storage deviation penalty coefficient of the reservoir; V t res,ref is the reference value of the storage of the reservoir, that is, the storage of the reservoir in the day-ahead stage.

[0063] The intraday scheduling stage takes the day-ahead plan as a reference, does not consider the storage constraints at the end of the daily scheduling of the hydrogen buffer tank and the reservoir, and the remaining constraint conditions are similar to those in the day-ahead stage.

[0064] The solution steps of the multi-stage operation optimization method for the independent island integrated energy system from week-ahead to day-ahead to intraday are as follows:

[0065] Step (1) Input and initialize the system device parameters. i and j respectively represent the rolling optimization times in the week-ahead and intraday stages;

[0066] Step (2) Construct the week-ahead stage operation optimization model and optimize to obtain the week-ahead scheduling plan from the i-th day to the (i + 6)-th day;

[0067] Step (3) Taking the ammonia storage at the end of the i-th day's scheduling under the i-th week-ahead optimization, that is, as a reference, optimize to obtain the day-ahead scheduling plan for the i-th day;

[0068] Step (4): Input the electrolyzer power \(P\) of the ammonia electro-synthesis system in the day-ahead scheduling plan for the \(i\)-th day t EL , the power \(P\) of the air separation nitrogen production equipment t AS and the output power of the ammonia synthesis equipment the output power \(P\) of the seawater desalination equipment t des , the storage capacity of the ammonia storage tank the storage capacity \(V\) of the hydrogen storage tank t HST and the storage capacity \(V\) of the reservoir t res , construct an intra-day stage operation optimization model, and optimize to obtain the intra-day scheduling plan from the \(j\)-th to the \(j + 3\)-th moment;

[0069] Step (5): For the optimization result of the current intra-day optimized control domain, judge whether the current optimization period is within the intra-day rolling optimization cycle. If so, after issuing the scheduling plan for the \(j\)-th to the \(j + 1\)-th period of the \(i\)-th day, return to Step (4) for solution; otherwise, issue the scheduling plan for the \(j\)-th to the \(j + 3\)-th period of the \(i\)-th day;

[0070] Step (6): Judge whether the current weekly pre-rolling optimization times is less than 7. If so, return to Step (2) to update the initial values of the storage capacity of the ammonia storage tank the initial value of the storage capacity of the hydrogen storage tank the initial value of the storage capacity of the reservoir and the initial value of the ammonia synthesis yield until \(i = 7\), complete the multi-stage operation optimization of weekly pre - day-ahead - intra-day.

[0071] The present invention proposes an optimized scheduling method for an island energy system considering ammonia electro-synthesis waste heat power generation. Combining the island's wind and solar resource endowments and the potential demand for ammonia, an integrated island comprehensive energy system architecture considering ammonia supply demand is established. For the process of electrolytic water hydrogen production - ammonia synthesis - waste heat recovery, the waste heat power generation process of the ammonia electro-synthesis system is finely characterized, and an ammonia electro-synthesis system model considering waste heat power generation units is established. To improve the long-term energy supply reliability of the island and effectively address the uncertainty problems existing in the island's wind and solar resources, a multi-stage operation optimization scheduling strategy for an independent island comprehensive energy system including an ammonia electro-synthesis system is proposed.

[0072] The present invention has the following beneficial effects compared with the prior art:

[0073] The present invention considers the waste heat power generation process of the electro-ammonia conversion system. By recovering the waste heat of the gas at the outlet of the ammonia synthesis tower for power generation, it effectively supplements the energy demand during the low periods of wind and light, and the waste heat recovery unit can improve the ammonia supply reliability of the system. Secondly, the present invention deals with the operation scheduling problem of the system in the way of coordinated optimization of long and short cycles, and proposes a multi-stage operation optimization scheduling method of week-ahead, day-ahead and hour-ahead, which effectively promotes the consumption of wind and light and further improves the ammonia supply reliability of the system. Finally, under the long cycle, the electro-ammonia conversion system can better adapt to the fluctuations of wind and light by the method of "peak shaving and valley filling", so that the peak-valley difference of the ammonia production rate ramp rate of the electro-ammonia conversion system is reduced compared with the day-ahead and hour-ahead optimization scheduling strategies, effectively improving the level of stable ammonia production. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments:

[0075] FIG Figure 1 is a schematic diagram of an independent island integrated energy system considering ammonia supply demand in the present invention;

[0076] FIG Figure 2 is a schematic diagram of an electro-ammonia conversion system model considering a waste heat power generation unit in the present invention;

[0077] FIG Figure 3 is a schematic diagram of the process flow of the waste heat power generation unit in the present invention;

[0078] FIG Figure 4 is a schematic diagram of the week-ahead, day-ahead and hour-ahead multi-stage operation optimization scheduling process in the present invention;

[0079] FIG Figure 5 is a schematic diagram of the optimization variables and variable transfer relationships at each stage under a single iteration in the present invention;

[0080] FIG Figure 6 is a schematic diagram of the predicted wind power output curve for week-ahead in the following embodiment of the present invention;

[0081] FIG Figure 7 is a schematic diagram of the predicted photovoltaic power output curve for week-ahead in the following embodiment of the present invention;

[0082] FIG Figure 8 is a schematic diagram of the predicted electricity demand curve for week-ahead in the following embodiment of the present invention;

[0083] FIG Figure 9 is a schematic diagram of the predicted water load demand curve for week-ahead in the following embodiment of the present invention;

[0084] FIG Figure 10 is a schematic diagram of the predicted ammonia load demand curve for week-ahead in the following embodiment of the present invention;

[0085] FIG Figure 11Schematic diagram of the predicted new energy output of the system within a week in the following embodiments of the present invention;

[0086] Appendix Figure 12 Schematic diagram of the change in the ammonia storage volume on the first day after each weekly pre-optimization under Scheme 3 in the following embodiments of the present invention;

[0087] Appendix Figure 13 Schematic diagram of the increase and decrease in the electric power under different schemes in the intraday stage in the following embodiments of the present invention;

[0088] Appendix Figure 14 Schematic diagram of the increase and decrease in the ammonia power under different schemes in the intraday stage in the following embodiments of the present invention;

[0089] Appendix Figure 15 Schematic diagram of the increase and decrease in the water power under different schemes in the intraday stage in the following embodiments of the present invention;

[0090] Appendix Figure 16 Schematic diagram of the comparison of the total ammonia load loss in a week under different schemes in the following embodiments of the present invention;

[0091] Appendix Figure 17 Schematic diagram of the comparison of the total abandoned wind and light energy in a week under different schemes in the following embodiments of the present invention. Detailed implementation manners

[0092] As shown in the figure, an optimized scheduling method for an island energy system considering power-to-ammonia waste heat power generation is used to improve the long-term energy supply reliability of the island and effectively cope with the uncertainty problems existing in the island's wind and light resources. The method adopts an independent island integrated energy system with a power-to-ammonia system to execute a multi-stage operation optimization scheduling strategy of weekly pre - daily - intraday. The independent island integrated energy system is a system considering ammonia supply demand, which uses wind energy and solar energy as energy inputs to supply energy to the seawater desalination equipment and the power-to-ammonia system, and meets the electrical load demand of island residents; at the same time, the seawater desalination equipment is used as a power demand response resource to increase the water - energy coupling relationship of the system model, and the cross - time storage and utilization of fresh water resources are realized through a reservoir. The ammonia - hydrogen powered ship used to meet the daily travel needs of island residents is used as the ammonia load, and the power-to-ammonia system and ammonia storage tank are used to effectively absorb the island's wind and light resources.

[0093] The power-to-ammonia system is based on establishing a power-to-ammonia system model considering a waste heat power generation unit, including an ammonia synthesis unit, a waste heat power generation unit, an electrolyzed water hydrogen production unit, and an air separation nitrogen production unit. When the system operates, hydrogen and nitrogen from the electrolyzed water hydrogen production unit and the air separation nitrogen production unit are mixed as raw material gas, pressurized by a compressor to the pressure required for ammonia synthesis reaction, and then enter the ammonia synthesis tower after being heated by a preheater; under the conditions of high temperature and high pressure, the compressed raw material gas reacts through a reactor equipped with a catalyst. The reaction gas at the outlet of the ammonia synthesis tower first enters the waste heat boiler of the waste heat power generation unit, and after heat recovery by the waste heat boiler, it further exchanges heat through a heat exchanger and enters the refrigeration system; the refrigeration system liquefies ammonia gas and sends it to a separator to improve the purity of liquid ammonia; the separator is used for the effective separation of liquid and gaseous substances, and the uneffectively cooled ammonia gas will re-enter the refrigeration system; in the refrigeration system, the unreacted nitrogen and hydrogen mixed gas needs to be recycled to improve the conversion rate of ammonia synthesis. In the model, each unit is expressed by the following formulas:

[0094] (1) Ammonia synthesis unit

[0095]

[0096] In the formula, is the ammonia production rate; is the ammonia production rate ramp rate; and are the upper and lower limits of the ammonia production rate ramp rate; and are the upper and lower limits of the ammonia production rate respectively; is the energy consumption of the ammonia synthesis unit; is the electric energy consumed per unit mass of ammonia produced.

[0097] (2) Waste heat power generation unit

[0098]

[0099]

[0100] In the formula, is the heat recovered by the waste heat boiler; M A is the average flow rate of the gas at the outlet of the ammonia synthesis tower per unit mass of ammonia produced; C p is the average specific heat capacity of the gas at the outlet of the ammonia synthesis tower; T1 is the average temperature of the gas at the inlet of the waste heat boiler; T2 is the average temperature of the gas at the outlet of the waste heat boiler; is the by-product steam amount of the waste heat boiler; η sun is the heat loss rate of the waste heat boiler; H1 is the enthalpy value of the high-pressure steam generated by the waste heat boiler; H2 is the enthalpy value of the hot water of the waste heat boiler; is the generated electric power of the waste heat power generation unit; η Gis the thermoelectric conversion efficiency of the steam turbine; τ is the electrothermal conversion coefficient.

[0101] (3) Electrolytic water hydrogen production unit

[0102]

[0103] In the formula, is the hydrogen production of the electrolyzer; η EL is the electro-hydrogen conversion efficiency of the electrolyzer; P t EL is the electrolyzer power; is the lower heating value of hydrogen; Δt is the scheduling step; and are the upper and lower limits of the operating power of the electrolyzer respectively. V t HST is the storage capacity of the hydrogen buffer tank; and are the storage and release efficiencies of the hydrogen buffer tank respectively; is the outlet flow of the hydrogen buffer tank, which is related to the ammonia synthesis rate; is the amount of hydrogen consumed to produce a unit mass of ammonia; and are the upper and lower limits of the storage capacity of the hydrogen buffer tank respectively; is the hydrogen compression energy consumption; is the molar mass of hydrogen; R is the ideal gas constant; T3 is the operating temperature of compressor c1; p2 and p1 are the pressures at the inlet and outlet of compressor c1 respectively; η c1 is the operating efficiency of compressor c1; are the hydrogen storage amounts at the beginning and end of each day in the hydrogen buffer tank respectively.

[0104] (4) Air separation nitrogen production unit

[0105] P t AS =[(F t Air / M Air )RT4ln(p4 / p3)] / η c2

[0106]

[0107] In the formula, P t AS is the energy consumption of the air separation nitrogen production unit; F t Air is the air injection amount of the air separation nitrogen production unit; M Air is the molar mass of air; R is the ideal gas constant; T4 is the operating temperature of compressor c2; p4 and p3 are the pressures at the inlet and outlet of compressor c2 respectively; η c2is the working efficiency of the compressor c2; η AS is the conversion efficiency of the air separation device; is the amount of nitrogen produced by the air separation nitrogen production unit, which is equal to the amount of nitrogen required by the ammonia synthesis unit; is the volume fraction of nitrogen in the air; is the amount of nitrogen consumed to produce a unit mass of ammonia.

[0108] In the multi-stage operation optimization scheduling strategy of week-ahead - day-ahead - hour-ahead, the objective function of the week-ahead scheduling stage is expressed as: F1 = min(C q +C om +C ramp )

[0109] In the formula, F1 is the total system operation cost in the week-ahead stage; C q is the cost of wind and solar energy curtailment; C om is the operation and maintenance cost; C ramp is the ammonia production rate ramp penalty cost of the power-to-ammonia system.

[0110] Among them, the cost of wind and solar energy curtailment, the operation and maintenance cost, and the ammonia production rate ramp penalty cost of the power-to-ammonia system are specifically expressed as follows:

[0111]

[0112] In the formula, ζ q is the unit cost of wind and solar energy curtailment; P t WT,pre and P t PV,pre are the predicted output values of wind power and photovoltaic power respectively; P t WT and P t PV are the actual consumption amounts of wind power and photovoltaic power respectively; C des is the operation and maintenance cost of the seawater desalination equipment; C P2A is the operation and maintenance cost of the power-to-ammonia system; ζ des is the unit operation and maintenance cost of the seawater desalination equipment; is the unit operation and maintenance cost of the waste heat power generation unit of the power-to-ammonia system; is the unit operation and maintenance cost of the ammonia synthesis unit, electrolytic water hydrogen production unit and air separation nitrogen production unit of the power-to-ammonia system; ζ ramp is the ammonia production rate ramp penalty coefficient.

[0113] The constraint conditions of the week-ahead scheduling stage include the constraints related to the power-to-ammonia system, the constraints of other equipment, and the power balance constraint. Among them, the constraints of other equipment and the power balance constraint are shown in the following formulas:

[0114] (1) Seawater desalination equipment constraint

[0115] Pt des = GV t des / Δt

[0116]

[0117] Wherein, P t des is the electric power of the seawater desalination equipment; G is the specific energy consumption of water production of the seawater desalination equipment; V t des is the water production volume of the seawater desalination equipment; and are the upper and lower limits of the power of the seawater desalination equipment respectively.

[0118] (2) Reservoir constraint

[0119]

[0120] Wherein, V t res is the water storage capacity of the reservoir; V t res,in and V t res,out are the water inflow and outflow of the reservoir; and are the upper and lower limits of the water storage capacity of the reservoir respectively; V res,in,max and V res,in,min are the maximum and minimum values of the water inflow of the reservoir respectively; V res,out,max and V res,out,min are the maximum and minimum values of the water outflow of the reservoir respectively; is a 0-1 variable. When is the water inflow of the reservoir, and when is the water outflow of the reservoir; are the water storage capacities of the reservoir at the beginning and end of each day respectively.

[0121] (3) Ammonia storage tank constraint

[0122]

[0123] Wherein, is the storage capacity of the ammonia storage tank; and are the storage efficiencies of the ammonia storage tank respectively; and are the ammonia inflow and outflow of the ammonia storage tank respectively; and are the upper and lower limits of the storage capacity of the ammonia storage tank respectively; and are the maximum and minimum values of the ammonia inflow of the ammonia storage tank respectively; m AST,out,max and mAST,out,min They are the maximum and minimum ammonia output amounts of the ammonia storage tank, respectively; is a 0-1 variable. When the ammonia storage tank stores ammonia, when the ammonia storage tank discharges ammonia.

[0124] (4) Wind and solar power output constraints

[0125] 0 ≤ P t WT ≤ P t WT,pre

[0126] 0 ≤ P t PV ≤ P t PV,pre

[0127] In the formula, P t WT and P t PV are the actual consumption amounts of wind power and photovoltaic power, respectively; P t WT,pre and P t PV,pre are the predicted output values of wind power and photovoltaic power, respectively.

[0128] (5) Power balance constraints

[0129]

[0130] In the formula, V t des is the water production volume of the seawater desalination equipment; V t res,in and V t res,out are the water inflow and outflow volumes of the water storage tank; V t load is the predicted value of the water load demand; P t L is the predicted value of the electric load demand; P t des is the electric power of the seawater desalination equipment; P t P2A is the net energy consumption of the power-to-ammonia system; and are the ammonia inflow and outflow amounts of the ammonia storage tank, respectively; is the predicted value of the ammonia load demand.

[0131] In the weekly - daily - intraday multi-stage operation optimization scheduling strategy, the objective function of the daily scheduling stage is expressed as:

[0132] wherein, F2 is the total system operation cost in the day-ahead stage; is the ammonia load loss cost; C s,AST is the ammonia storage deviation penalty cost.

[0133] The ammonia load loss cost and the ammonia storage deviation penalty cost in the objective function of the day-ahead scheduling stage are expressed as:

[0134]

[0135] wherein, T2 is the number of time periods in the day-ahead scheduling stage, taking 24h; ζ loss is the unit ammonia load reduction penalty coefficient; is the amount of ammonia load reduced per unit time; ζ AST is the penalty coefficient for unit ammonia storage deviation; is the reference value of the ammonia storage at the end of the day-ahead scheduling stage, that is, the ammonia storage level at the end of the first-day scheduling obtained in the week-ahead stage; is the actual ammonia storage at the end of each day's scheduling in the day-ahead scheduling stage.

[0136] In the week-ahead - day-ahead - intra-day multi-stage operation optimization scheduling strategy, the day-ahead scheduling stage satisfies the corresponding operation constraints and the system power balance constraints of the week-ahead scheduling stage; and part of the ammonia load is modeled as a load that can be reduced. The constraints related to ammonia load loss are as follows:

[0137]

[0138] wherein, is the maximum total amount of ammonia load that can be reduced within the scheduling period; is the maximum amount of ammonia load that can be reduced per unit time.

[0139] In the week-ahead - day-ahead - intra-day multi-stage operation optimization scheduling strategy, the objective function in the intra-day scheduling stage is expressed as:

[0140] wherein, F3 is the total system operation cost in the intra-day stage; C p is the equipment output plan adjustment cost; C s is the energy storage equipment storage deviation adjustment cost; C s,res is the reservoir storage deviation adjustment cost;

[0141] The equipment output plan adjustment cost, the energy storage equipment storage deviation adjustment cost, and the reservoir storage deviation adjustment cost in the objective function of the intra-day scheduling stage are expressed as:

[0142]

[0143] wherein, l is the starting time of the intra-day rolling optimization; T3 is the number of time periods in the intra-day scheduling stage, taking 4h; κu is the unit power deviation penalty coefficient of device u, where device u includes electrolyzers, air separation nitrogen production equipment, and ammonia synthesis equipment in the ammonia electrolysis system, as well as seawater desalination equipment; P t u,ref is the reference output power of device u, that is, the output power of device u in the day-ahead stage; P t u is the output power of device u in the intraday dispatch; κ z is the unit storage deviation penalty coefficient of energy storage device z, where energy storage device z includes hydrogen buffer tanks and ammonia storage tanks; V t z,ref is the reference storage of energy storage device z, that is, the storage of energy storage device z in the day-ahead stage; V t z is the storage of energy storage device z in the intraday stage; κ res is the unit storage deviation penalty coefficient of the reservoir; V t res,ref is the reference storage of the reservoir, that is, the storage of the reservoir in the day-ahead stage.

[0144] In the intraday dispatch stage, taking the day-ahead plan as a reference, the storage constraints at the end of the daily dispatch of hydrogen buffer tanks and reservoirs are not considered, and the remaining constraint conditions are similar to those in the day-ahead stage.

[0145] The solution steps of the multi-stage operation optimization method for the independent island integrated energy system from week-ahead to day-ahead to intraday are as follows:

[0146] Step (1) Input and initialization of system device parameters, where i and j respectively represent the rolling optimization times in the week-ahead and intraday stages;

[0147] Step (2) Construct a week-ahead stage operation optimization model and optimize to obtain the week-ahead dispatch plan from the i-th day to the i + 6-th day;

[0148] Step (3) Taking the ammonia storage at the end of the i-th day's dispatch under the i-th week-ahead optimization, that is as a reference, optimize to obtain the day-ahead dispatch plan for the i-th day;

[0149] Step (4) Input the power P t EL of the electrolyzer in the ammonia electrolysis system, the power P t AS of the air separation nitrogen production equipment, and the output power of the ammonia synthesis equipment, the output power P t des of the seawater desalination equipment, the storage of the ammonia storage tank, the storage V t HST of the hydrogen storage tank, and the storage V tres , construct an intraday stage operation optimization model, and optimize to obtain the intraday scheduling plan from the j-th to the (j + 3)-th moment;

[0150] Step (5) For the optimized control domain optimization result in the current intraday period, determine whether the current optimization period is within the intraday rolling optimization cycle. If so, after issuing the scheduling plan for the j-th to the (j + 1)-th period of the i-th day, return to Step (4) for solution; otherwise, issue the scheduling plan for the j-th to the (j + 3)-th period of the i-th day;

[0151] Step (6) Determine whether the current number of times of pre-week rolling optimization is less than 7. If so, return to Step (2) to update the initial value of the ammonia storage tank storage Initial value of the hydrogen storage tank storage Initial value of the reservoir storage and the initial value of the ammonia synthesis rate Until i = 7, complete the multi-stage operation optimization of pre-week - day-ahead - intraday.

[0152] Example:

[0153] Taking an independent island in Fujian Province as the research object, the installed capacities of the wind power and photovoltaic units are 2500 kW and 1000 kW respectively. The historical data of the output of the wind-solar units and the load demand in the example are from the measured data of a certain year of the island provided by the local power grid company. The actual wind-solar output and the power and water load demand of the typical week of the island are taken as the pre-week predicted power curve. Considering that the current ammonia-hydrogen powered marine vessels are still in the technical R & D stage, this paper combines the travel characteristics of the island residents and the energy consumption level of the ammonia-hydrogen powered vessels, and uses the method of multiplying the ammonia consumption per unit nautical mile by the travel distance of the residents to quantify the ammonia demand of the island. The pre-week predicted output curve is as Figures 6 - 10 shown. At the same time, by superimposing the normal distribution on the actual wind power output curve and the load curve respectively, and superimposing the TLS (t location-scale) distribution on the actual photovoltaic output curve, the wind-solar power and load curves in the day-ahead and intraday stages are simulated. The specific parameters of each unit of the power-to-ammonia system are shown in Table 1. To verify the effectiveness of the proposed method in improving the operation ability of the independent island integrated energy system considering ammonia supply demand, 3 operation schemes are set, as shown in Table 2. Taking one week as the scheduling period, the optimization results of different stages are analyzed.

[0154] Table 1 Parameters of each equipment in the system

[0155]

[0156] Table 2 Example settings

[0157]

[0158] Among them: "√" indicates considering this factor; "×" indicates not considering this factor.

[0159] In the pre-week stage, the ammonia storage level at the end of the first-day scheduling is obtained through continuous rolling optimization for multiple times. Taking Scheme 3 as an example, the pre-week optimization results are analyzed. Assuming that there are no obvious differences in the daily curves of electricity, ammonia, and water loads, the new energy predicted output in the system within a week is statistically analyzed, as Figure 11 shown. For the convenience of description, the sum of the installed capacities of wind power and photovoltaic units is used as the reference value. It is defined that the day with the new energy average output lower than 30% of the reference value is a day with insufficient wind and light, the day between 30% - 40% of the reference value is a day with sufficient wind and light, and the day higher than 40% of the reference value is a day with excessive wind and light. In addition, to more intuitively reflect the changing trend of ammonia storage obtained in the pre-week stage, the ammonia storage on the first day after each pre-week optimization is arranged in sequence, as Figure 12 shown. Among them, the change in ammonia storage on the first day after the first pre-week optimization is the change in ammonia storage on the 1st day, and the change in ammonia storage on the first day after the second pre-week optimization is the change in ammonia storage on the 2nd day, and so on.

[0160] Combined with Figure 12 it can be found that the wind and light level and the change in ammonia storage show a changing trend of "high storage, medium slow release, and low consumption", that is, on the day with excessive wind and light, the system stores ammonia to fully absorb wind and light; on the day with sufficient wind and light, the ammonia storage does not change significantly; on the day with insufficient wind and light, the system consumes the previously stored ammonia. Specifically, the ammonia storage at the end of the first-day scheduling after the first pre-week optimization reaches 64.12% of the rated capacity. This is because the wind and light on the island are excessive on this day. To ensure the reliable ammonia supply on the island when there is insufficient energy in the future, the system stores a large amount of ammonia to absorb wind and light, realizing the transfer of energy between different days. In addition, the wind and light levels on the first day during the 3rd and 4th pre-week optimizations are relatively low. To ensure the reliable operation of the island's integrated energy system, the system consumes the previously stored ammonia, resulting in the ammonia storage dropping to 47.27% and 28.17% of the rated capacity. It can be seen that the pre-week stage can better exert the long-cycle storage advantage of ammonia energy. By reasonably evaluating the energy situation in the next week, while making full use of wind and light resources, it meets the ammonia demand of the system during the period of insufficient wind and light, so as to improve the reliability of ammonia supply of the system.

[0161] The total system operating cost and each sub-item cost in the day-ahead stage under the three schemes are shown in Table 3.

[0162] Table 3 Day-ahead optimization results under different schemes

[0163]

[0164] As can be seen from Table 3, due to the introduction of the waste heat power generation unit, Scheme 2 meets the ammonia demand of the island during low wind and light periods, reducing the ammonia load loss cost by 4.08%. It can be seen that the waste heat power generation unit of the power-to-ammonia system can effectively improve the ammonia supply reliability of the system. In addition, although Scheme 3 increases the operation and maintenance cost and adjustment cost of the system, considering the energy situation in the next week in the pre-week stage, the energy in the next few days is reasonably allocated. Therefore, Scheme 3 can meet the ammonia demand of the island, and its wind and light abandonment cost is reduced by 91.26% compared with Scheme 2. At the same time, compared with Scheme 2, the ammonia synthesis ramp penalty cost of Scheme 3 is reduced by 45.83%, and the total system operation cost is reduced by 45.64%, further verifying the effectiveness of the proposed pre-week - intra-day - intra-day multi-stage scheduling strategy for the independent island integrated energy system in improving the ammonia supply reliability, wind and light resource utilization rate, and ammonia stable production capacity of the system.

[0165] Compared with the day-ahead stage, the power increase and decrease amounts in the intra-day stage under each scheme are as Figures 13 - 15 shown. From Figures 13 - 15 it can be seen that in the intra-day stage, the system mainly reduces the impact brought by the prediction deviation of wind, light output and electricity load by adjusting the power of the electrolyzed water hydrogen production unit and the ammonia synthesis unit. At the same time, the ammonia load fluctuation relies on the flexible regulation ability of the power-to-ammonia system, and is smoothed by flexibly adjusting the ammonia synthesis rate, the inflow and outflow of the ammonia storage tank, and the reducible ammonia load. In addition, the water demand on the island is only provided by the seawater desalination equipment. Therefore, in the intra-day scheduling process, the system preferentially adjusts the water inflow and outflow of the reservoir, and then adjusts the water production of the seawater desalination equipment.

[0166] From Figure 16 and Figure 17 it can be found that the total ammonia load loss and the total wind and light abandonment in a week are the best in Scheme 3. Compared with Scheme 1 and Scheme 2, the total ammonia load loss in a week of Scheme 3 is reduced by 89.60% and 89.16% respectively, and the total wind and light abandonment is reduced by 82.58% and 82.99% respectively. In addition, the total ammonia load loss in a week in Scheme 2 is reduced by 4.72% compared with Scheme 1. The relevant reasons for the above phenomena have been specifically analyzed in the day-ahead stage and will not be elaborated here. In addition, the total ammonia load loss and the total wind and light abandonment in a week in the intra-day stage under each scheme are higher than the sum of the total ammonia load loss and the total wind and light abandonment in each day in the day-ahead stage. This is because the scheduling plan formulated in the day-ahead stage is phased, and the formulated scheduling strategy is too conservative, only providing a reference value for the intra-day stage. The wind and light load prediction accuracy in the intra-day stage is high, and the scheduling plan can be updated according to the change of the wind and light load, and the obtained scheduling plan is more accurate, but Scheme 3 is still the optimal scheme.

[0167] In summary, the proposed weekly-day-ahead-intraday multi-stage optimal scheduling strategy for the integrated energy system of independent islands considering waste heat power generation of the electro-ammonia conversion system can effectively promote the consumption of wind and light in the system and improve the reliability of ammonia supply on the islands.

[0168] The above are the preferred embodiments of the present invention. All changes made according to the technical solution of the present invention and whose functional effects do not exceed the scope of the technical solution of the present invention belong to the protection scope of the present invention.

Claims

1. An optimized scheduling method for an island energy system considering power generation using the waste heat from electro-amination, which is used to improve the long-term energy supply reliability of the island and effectively address the uncertainty issues of the island's wind and solar resources. It is characterized in that: The method adopts an independent island integrated energy system with an ammonia electrolysis system to implement a multi-stage operation optimization scheduling strategy from week-ahead to day-ahead to intra-day. The independent island integrated energy system is a system that takes into account the ammonia supply demand. It uses wind energy and solar energy as energy inputs to supply energy to the seawater desalination equipment and the ammonia electrolysis system, and meets the electricity load demand of island residents. At the same time, the seawater desalination equipment is used as a power demand response resource to increase the water-energy coupling relationship of the system model, and the cross-time storage and utilization of fresh water resources are realized through a reservoir. The ammonia-hydrogen powered ship used to meet the daily travel needs of island residents is used as an ammonia load, and the ammonia electrolysis system and ammonia storage tank are used to effectively absorb the island's wind and light resources.

2. The optimized scheduling method for the island energy system considering power generation using the waste heat of electrotransfer ammonia according to claim 1, wherein: The ammonia electrolysis system is based on the establishment of an ammonia electrolysis system model considering a waste heat power generation unit, including an ammonia synthesis unit, a waste heat power generation unit, an electrolytic water hydrogen production unit, and an air separation nitrogen production unit. When the system operates, the hydrogen and nitrogen mixed from the electrolytic water hydrogen production unit and the air separation nitrogen production unit are used as raw material gas, pressurized by a compressor to the pressure required for the ammonia synthesis reaction, and then enter the ammonia synthesis tower after being heated by a preheater. Under the conditions of high temperature and high pressure, the compressed raw material gas reacts through a reactor equipped with a catalyst. The reaction gas at the outlet of the ammonia synthesis tower first enters the waste heat boiler of the waste heat power generation unit, and after heat recovery by the waste heat boiler, it enters the refrigeration system through further heat exchange by a heat exchanger. The refrigeration system liquefies the ammonia gas and sends it to a separator to improve the purity of the liquid ammonia. The separator is used for the effective separation of liquid substances and gaseous substances, and the uneffectively cooled ammonia gas will re-enter the refrigeration system. In the refrigeration system, the unreacted nitrogen and hydrogen mixed gas needs to be recycled to improve the conversion rate of ammonia synthesis. In the model, each unit is expressed by the following formulas: (1) Ammonia synthesis unit Wherein, is the ammonia production rate; is the ammonia production rate ramp-up rate; and are the upper and lower limits of the ammonia production rate ramp-up rate; and They are the upper and lower limits of ammonia production rate respectively; It is the energy consumption of the ammonia synthesis unit; It is the electric energy consumed for producing unit mass of ammonia. (2) Waste heat power generation unit In the formula, is the heat recovered by the waste heat boiler; M A is the average flow rate of the outlet gas of the ammonia synthesis tower when producing unit mass of ammonia; C p is the average specific heat capacity of the outlet gas of the ammonia synthesis tower. T1 is the average temperature of the gas at the inlet of the waste heat boiler; T2 is the average temperature of the gas at the outlet of the waste heat boiler; is the by-product steam output of the waste heat boiler; η sun is the heat loss rate of the waste heat boiler; H1 is the enthalpy value of the high-pressure steam generated by the waste heat boiler; H2 is the enthalpy value of the hot water of the waste heat boiler; is the generated electric power of the waste heat power generation unit; η G is the thermoelectric conversion efficiency of the steam turbine; τ is the electrothermal conversion coefficient. (3) Electrolytic water hydrogen production unit In the formula, is the hydrogen production of the electrolyzer; η EL is the electro-hydrogen conversion efficiency of the electrolyzer; P t EL is the electrolyzer power; is the lower calorific value of hydrogen; Δt is the scheduling step size; and are the upper and lower limits of the operating power of the electrolyzer, respectively. V t HST is the storage capacity of the hydrogen buffer tank; and are the storage and release efficiencies of the hydrogen buffer tank, respectively; is the outlet flow rate of the hydrogen buffer tank, which is related to the ammonia synthesis rate; is the amount of hydrogen consumed to produce a unit mass of ammonia; and are the upper and lower limits of the storage capacity of the hydrogen buffer tank, respectively; is the hydrogen compression energy consumption; is the molar mass of hydrogen; R is the ideal gas constant; T3 is the operating temperature of compressor c1; p2 and p1 are the pressures at the inlet and outlet of compressor c1, respectively; η c1 is the working efficiency of compressor c1; V0 HST , are the hydrogen storage amounts in the hydrogen buffer tank at the beginning and end of each day respectively. (4) Air separation nitrogen production unit P t AS = [(F t Air / M Air )RT4ln(p4 / p3)] / η c2 Wherein, P t AS is the energy consumption of the air separation nitrogen production unit; F t Air is the air injection volume of the air separation nitrogen production unit; M Air is the molar mass of air; R is the ideal gas constant; T4 is the working temperature of compressor c2; p4 and p3 are the pressures at the inlet and outlet of compressor c2 respectively; η c2 is the working efficiency of compressor c2; η AS is the conversion efficiency of the air separation device; is the amount of nitrogen produced by the air separation nitrogen production unit, which is equal to the amount of nitrogen required by the ammonia synthesis unit; is the volume fraction of nitrogen in the air; is the amount of nitrogen consumed to produce a unit mass of ammonia.

3. The optimized scheduling method of the island energy system considering power generation using the waste heat of electrotransamination according to claim 2, characterized in that: In the multi-stage operation optimization scheduling strategy of before-week, before-day, and within-day, the objective function in the before-week scheduling stage is expressed as: F1 = min(C q + C om + C ramp ) In the formula, F1 is the total system operation cost in the before-week stage; C q is the cost of wind and light curtailment; C om is the operation and maintenance cost; C ramp is the ammonia production rate ramp penalty cost of the power-to-ammonia system. Among them, the curtailment cost of wind and light energy, the operation and maintenance cost, and the ammonia production rate ramp penalty cost of the ammonia electrolysis system are specifically expressed as follows: Where ζ q is the unit cost of abandoned wind and solar energy; P t WT,pre and P t PV,pre are the predicted output values of wind power and photovoltaic power respectively; P t WT and P t PV are the actual consumption amounts of wind power and photovoltaic power respectively; C des is the operation and maintenance cost of the seawater desalination equipment; C P2A is the operation and maintenance cost of the power-to-ammonia system; ζ des is the unit operation and maintenance cost of the seawater desalination equipment; is the unit operation and maintenance cost of the waste heat power generation unit of the power-to-ammonia system; ζ NH3,main is the unit operation and maintenance cost of the ammonia synthesis unit, electrolytic water hydrogen production unit and air separation nitrogen production unit of the power-to-ammonia system; ζ ramp is the ammonia production rate ramp penalty coefficient.

4. The optimized scheduling method for an island energy system considering power generation using the waste heat of electrotransamination according to claim 3, characterized in that: The constraint conditions in the week-ahead scheduling stage include the constraints related to the ammonia electrolysis system, the constraints of other equipment, and the power balance constraint. Among them, the constraints of other equipment and the power balance constraint are shown in the following formulas: (1) Seawater desalination equipment constraint P t des = GV t des / Δt Wherein, P t des is the electric power of the seawater desalination equipment; G is the specific energy consumption of water production of the seawater desalination equipment; V t des is the water production volume of the seawater desalination equipment; and are respectively the upper and lower limits of the power of the seawater desalination equipment. (2) Reservoir constraint Where, V t res is the water storage volume of the reservoir; V t res,in and V t res,out are the water inflow and outflow of the reservoir; and are the upper and lower limits of the water storage volume of the reservoir respectively; V res,in,max and V res,in,min are the maximum and minimum values of the water inflow of the reservoir respectively; V res,out,max and V res,out,min are the maximum and minimum values of the water outflow of the reservoir respectively; is a 0-1 variable. When is for the reservoir to intake water, and when is for the reservoir to discharge water; are the water storage volumes of the reservoir at the beginning and end of each day respectively. (3) Ammonia storage tank constraint In the formula, is the storage capacity of the ammonia storage tank; and are the storage efficiencies of the ammonia storage tank respectively; and are the ammonia inlet volume and ammonia outlet volume of the ammonia storage tank respectively; and are the upper and lower limits of the storage capacity of the ammonia storage tank respectively; and are the maximum and minimum values of the ammonia inlet volume of the ammonia storage tank respectively; m AST,out,max and m AST,out,min are the maximum and minimum values of the ammonia outlet volume of the ammonia storage tank respectively; is a 0-1 variable. When the ammonia storage tank stores ammonia, and when the ammonia storage tank discharges ammonia. (4) Wind and light power output constraint 0 ≤ P t WT ≤ P t WT,pre 0 ≤ P t PV ≤ P t PV,pre Wherein, P t WT and P t PV are respectively the actual accommodation amounts of wind power and photovoltaic power; P t WT,pre and P t PV,pre are respectively the predicted output values of wind power and photovoltaic power. (5) Power balance constraint V t des -V t res,in +V t res,out = V t load Wherein, V t des is the water production volume of the seawater desalination equipment; V t res,in and V t res,out are the water inflow and outflow of the reservoir; V t load is the predicted value of water load demand; P t L is the predicted value of electric load demand; P t des is the electric power of the seawater desalination equipment; P t P2A is the net energy consumption of the electro-ammonia conversion system; m t AST,in and m t AST,out are the ammonia inflow and outflow of the ammonia storage tank respectively; is the predicted value of ammonia load demand.

5. The optimized scheduling method for an island energy system considering power generation using the waste heat of electrotransamination according to claim 2, characterized in that: In the multi-stage operation optimization scheduling strategy from week-ahead to day-ahead to intra-day, the objective function in the day-ahead scheduling stage is expressed as: where F2 is the total operating cost of the system in the day-ahead stage; is the cost of ammonia load loss; C s,AST is the penalty cost for ammonia storage deviation.

6. The optimized scheduling method for island energy systems considering power generation using the waste heat of electro-transamination according to claim 5, characterized in that: The ammonia load loss cost and the ammonia storage deviation penalty cost in the objective function of the day-ahead scheduling stage are expressed as: Where, T2 is the number of time periods in the day-ahead scheduling stage, taking 24 h; ζ loss is the penalty coefficient for unit ammonia load reduction; is the amount of ammonia load reduced per unit time; ζ AST is the penalty coefficient for unit ammonia storage deviation; is the reference value of ammonia storage at the end of the day-ahead stage scheduling, that is, the ammonia storage level at the end of the first-day scheduling obtained in the week-ahead stage; is the actual ammonia storage at the end of each day's scheduling in the day-ahead scheduling stage.

7. The optimized scheduling method for an island energy system considering power generation using the waste heat from electro-amination according to claim 2, characterized in that: In the multi-stage operation optimization scheduling strategy from week-ahead to day-ahead to intra-day, the day-ahead scheduling stage meets the corresponding operation constraints and the system power balance constraint in the week-ahead scheduling stage; and part of the ammonia load is modeled as a load that can be curtailed. The constraints related to the ammonia load loss are as follows: In the formula, is the maximum total amount of ammonia load that can be reduced during the scheduling period; is the maximum amount of ammonia load that can be reduced per unit time.

8. An optimized scheduling method for an island energy system considering power generation from the waste heat of electro-transamination according to claim 2, characterized in that: In the multi-stage operation optimization scheduling strategy of weeks before - days before - hours within a day, the objective function in the hourly scheduling stage is expressed as: Wherein, F3 is the total operating cost of the intraday stage system; C p is the cost of adjusting the equipment output plan; C s is the cost of adjusting the storage deviation of the energy storage device; C s,res is the cost of adjusting the storage deviation of the reservoir; The equipment output plan adjustment cost, the energy storage equipment storage deviation adjustment cost, and the reservoir storage deviation adjustment cost in the objective function in the intra-day scheduling stage are expressed as: Wherein, l is the starting time of intraday rolling optimization; T3 is the number of time periods in the intraday scheduling stage, taking 4h; κ u is the unit power deviation penalty coefficient of device u, where device u includes electrolyzers, air separation nitrogen production equipment, and ammonia synthesis equipment in the power-to-ammonia system, as well as seawater desalination equipment; P t u,ref is the reference output power value of device u, that is, the output power of device u in the day-ahead stage; P t u is the output power of device u in the intraday scheduling; κ z is the unit storage deviation penalty coefficient of energy storage device z, where energy storage device z includes hydrogen buffer tanks and ammonia storage tanks; V t z,ref is the reference storage value of energy storage device z, that is, the storage of energy storage device z in the day-ahead stage; V t z is the storage of energy storage device z in the intraday stage; κ res is the unit storage deviation penalty coefficient of the reservoir; V t res ,ref is the reference storage value of the reservoir, that is, the storage of the reservoir in the day-ahead stage.

9. The optimized scheduling method for an island energy system considering power generation using the waste heat of electrotransamination according to claim 8, characterized in that: The intra-day scheduling stage takes the day-ahead plan as a reference and does not consider the storage constraints at the end of each day's scheduling for the hydrogen buffer tank and the reservoir.

10. The optimized scheduling method for an island energy system considering power generation using the waste heat of electrotransamination according to claim 2, characterized in that: The solution steps of the multi-stage operation optimization method for the independent island integrated energy system from weekly to daily to hourly are as follows: Step (1) Input and initialization of system equipment parameters, where i and j represent the rolling optimization times in the weekly and hourly stages respectively; Step (2) Construct a weekly operation optimization model to optimize and obtain the weekly scheduling plan from the i-th day to the (i + 6)-th day; Step (3) uses the ammonia storage at the end of the i-th day's scheduling under the i-th weekly pre-optimization as a reference to optimize and obtain the day-ahead scheduling plan for the i-th day; Step (4) Input the electrolyzer power P of the ammonia electrolysis system in the day-ahead scheduling plan for the i-th day t EL , the power P of the air separation nitrogen production equipment t AS and the output power of the ammonia synthesis equipment , the output power P of the seawater desalination equipment t des , the storage capacity m of the ammonia storage tank t AST , the storage capacity V of the hydrogen storage tank t HST and the storage capacity V of the reservoir t res , construct an intraday stage operation optimization model, and optimize to obtain the intraday scheduling plan from the j-th to the j+3-th moment; Step (5) For the optimized control domain optimization result in the current hour, determine whether the current optimization period is within the hourly rolling optimization cycle. If so, after issuing the scheduling plan for the j-th to (j + 1)-th periods on the i-th day, return to Step (4) for solution; Otherwise, issue the scheduling plan for the j-th to (j + 3)-th periods on the i-th day; Step (6) determines whether the number of rolling optimizations before the current week is less than 7. If so, return to step (2) to update the initial value of the ammonia storage tank's storage Initial value of the hydrogen storage tank's storage V0 HST , initial value of the reservoir's storage V0 res and the initial value of the ammonia synthesis rate Until i = 7, complete the multi-stage operation optimization of week-before - day-before - hour-before

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