An Optimal Scheduling Method for Cross-Regional Electric-Hydrogen Coupling System Considering Methanol Storage and Transportation

Abstract

The present invention relates to the technical field of optimal dispatching of power systems, and specifically relates to an optimal dispatching method for an inter-regional electricity-hydrogen coupling system considering methanol storage and transportation, including determining the structure of the inter-regional electricity-hydrogen coupling system and obtaining the basic data of the electricity-hydrogen coupling system in each region; establishing an energy storage and transportation model for the power grid-methanol-hydrogen supply chain; establishing a two-layer optimal economic dispatching model for the inter-regional electricity-hydrogen coupling system considering methanol storage and transportation, and determining the annual operation dispatching plan for the electricity-hydrogen coupling system in each region. The present invention fully considers the energy supply and consumption characteristics of different regions and the operation characteristics of each system. By reasonably dispatching the operation of equipment in the sending and receiving regions, as well as the power and methanol transportation plans, it can effectively improve the operation economy of the inter-regional electricity-hydrogen coupling system and the renewable energy consumption level, and promote the coordinated and complementary operation of the electricity-hydrogen coupling systems between regions.

Description

Technical Field

[0001] The present invention relates to the technical field of optimal dispatching of power systems, and specifically to an optimal dispatching method for an inter-regional electricity-hydrogen coupling system considering methanol storage and transportation. Background Art

[0002] Developing an electricity-hydrogen coupling system is considered an effective way to promote the transformation of the energy structure and the large-scale consumption of renewable energy. However, in practice, the uneven spatio-temporal distribution of renewable energy and energy demand restricts the development of the electricity-hydrogen coupling system. Inter-regional energy interconnection is one of the important means to achieve optimal allocation of resources and improve utilization efficiency. Constructing an inter-regional electricity-hydrogen coupling system can give full play to the complementary benefits between regions and greatly improve the level of renewable energy consumption.

[0003] Existing technical solutions for the optimal dispatching of inter-regional electricity-hydrogen coupling systems mainly focus on using the power grid or transportation network for the inter-regional interconnected transmission of energy, so as to optimize the operation plans of equipment and resource allocation between regions. However, there are problems of limited energy transmission capacity and high transmission costs, which are not conducive to the popularization and development of inter-regional electricity-hydrogen coupling systems. Methanol has a higher volumetric energy density than hydrogen, and there is already a relatively mature storage and transportation system, with low storage and transportation costs. It is considered an excellent future energy carrier and has good development prospects in the inter-regional electricity-hydrogen coupling system. However, at present, there is no optimal dispatching method for an inter-regional electricity-hydrogen coupling system considering methanol storage and transportation, and the role of methanol storage and transportation in the inter-regional electricity-hydrogen coupling system cannot be better exerted. Summary of the Invention

[0004] The purpose of the present invention is to provide an optimal dispatching method for an inter-regional electricity-hydrogen coupling system considering methanol storage and transportation, so as to solve the technical problem in the prior art that the role of methanol storage and transportation in the inter-regional electricity-hydrogen coupling system cannot be better exerted.

[0005] An optimal dispatching method for an inter-regional electricity-hydrogen coupling system considering methanol storage and transportation includes the following steps:

[0006] 1) Determine the structure of the inter-regional electricity-hydrogen coupling system considering methanol storage and transportation, and obtain the basic data of the regional electricity-hydrogen coupling system. Among them, the sending region includes a methanol reactor for producing methanol from hydrogen + carbon dioxide and a methanol storage warehouse, the receiving region includes a methanol reforming reactor for producing hydrogen, the sending and receiving regions are connected by a regional tie line and a methanol transportation network, and conventional generating units, green energy generating units, and hydrogen fuel cells are provided in both the sending and receiving regions;

[0007] 2) Establish an energy storage and transportation model for the power grid-methanol-hydrogen supply chain including corresponding constraint conditions. The energy storage and transportation model for the power grid-methanol-hydrogen supply chain includes an electrolyzer model, a hydrogen storage tank model, a methanol spatio-temporal flexibility model, and a hydrogen supply and demand balance model;

[0008] As described above, in the hydrogen storage tank model, it includes the time series relationship of the hydrogen storage capacity of the hydrogen storage tank at adjacent moments, the safety constraint of the hydrogen storage tank capacity, the hydrogen storage and hydrogen release constraints, and the input and output balance relationship of hydrogen within the scheduling period;

[0009] As described above, the methanol spatio-temporal flexibility model includes a hydrogen-methanol conversion model, a methanol reforming hydrogen production model, and a methanol cross-regional seasonal storage and transportation model;

[0010] In the methanol cross-regional seasonal storage and transportation model, it includes the methanol storage and transportation relationship at the sending end and the methanol storage and transportation capacity constraint;

[0011] 3) Based on the cross-regional electricity-hydrogen coupling system considering methanol storage and transportation, an optimal economic dispatch model is established to determine the annual operation dispatch plan of the electricity-hydrogen coupling system in each region;

[0012] The optimal economic dispatch model includes an upper-layer daily dispatch model. Based on the upper-layer daily dispatch model, with a day as the dispatch time scale, the annual operation dispatch plan of the system is obtained with the goal of minimizing the system cost;

[0013] The system cost needs to include the hydrogen supply chain cost C obtained from the power grid-methanol-hydrogen supply chain energy storage and transportation model HSC ;

[0014] Among the considered constraint conditions, it needs to include the hydrogen supply and demand balance constraint, electrolyzer, hydrogen storage tank and methanol storage and transportation constraints based on the aforementioned power grid-methanol-hydrogen supply chain energy storage and transportation model; and the power balance constraint and the start-stop constraint of the conventional generator set;

[0015] The annual operation dispatch plan of the system includes the medium- and long-term daily start-stop arrangements of the conventional generator sets and the methanol transportation plan.

[0016] Furthermore, the optimal economic dispatch model also includes a lower-layer hourly dispatch model. Based on the lower-layer hourly dispatch model, under the start-stop of the conventional generator sets and the methanol transportation plan determined by the upper-layer daily dispatch model, with an hour as the dispatch time scale, the annual operation dispatch plan of the system is obtained with the goal of minimizing the system cost;

[0017] The system cost of the lower-layer hourly dispatch model needs to include the operation and maintenance cost of the hydrogen fuel cell and the load shedding penalty cost, and does not include the start-stop cost of the conventional generator set and the transportation cost part of the hydrogen supply chain cost;

[0018] Among the considered constraint conditions, it needs to include the power balance constraint, the ramp constraint of the conventional generator set, and the hydrogen fuel cell constraint, and does not include the power balance constraint and the start-stop constraint of the conventional generator set;

[0019] The annual operation dispatch plan of the system includes the dispatch output plans of the sending and receiving end units, the power transmission plan, and the operation plans of each device in the hydrogen energy subsystem.

[0020] Furthermore, the electrolyzer model is as follows:

[0021]

[0022] 0 ≤ E s,E,t ≤ E s,E,max (2)

[0023] Wherein, m H2 s,E,t is the hydrogen production amount of the electrolyzer at time t in area s, S is the area set, including the sending area j and the receiving area r; η H2 is the operating efficiency of the electrolyzer; E s,E,t is the power input to the electrolyzer at time t in area s, LHV H2 is the lower heating value of hydrogen, which is 33.3 kWh / kg, and E s,E,max is the upper limit of the power input to the electrolyzer.

[0024] Furthermore, the hydrogen storage tank model includes:

[0025] The time-series relationship of the hydrogen storage capacity of adjacent moments of the hydrogen storage tank is as follows:

[0026]

[0027] And the following safety constraints for the hydrogen storage tank capacity:

[0028]

[0029] And the following hydrogen storage and hydrogen release constraints:

[0030]

[0031] And the following input and output balance of hydrogen within the scheduling period

[0032]

[0033] Wherein, is the hydrogen storage capacity of the hydrogen storage tank at time t in area s; are respectively the hydrogen storage and hydrogen release amounts at time t in area s; and are respectively the upper limits of the hydrogen storage tank capacity, hydrogen input amount and hydrogen release amount.

[0034] Furthermore, the hydrogen-methanol conversion model is as follows:

[0035]

[0036] Wherein, is the methanol production amount at time t, and η HMis the conversion coefficient of hydrogen plus carbon dioxide to methanol, m H2,M,t is the amount of green hydrogen input at time t, m H2,M,max is the upper limit of hydrogen input to the methanol reactor.

[0037] Furthermore, the methanol reforming for hydrogen production model is as follows:

[0038]

[0039] In the formula, is the amount of hydrogen produced by methanol reforming at time t, η MH is the conversion coefficient of methanol steam reforming for hydrogen production, m M,H2,t is the amount of methanol input at time t, m M,H2,max is the upper limit of methanol input.

[0040] Furthermore, in the methanol cross-region seasonal storage and transportation model, it is assumed that there is a green methanol warehouse in the sending region and methanol outward transportation is considered, while there is no corresponding methanol warehouse in the receiving region, and the changes in methanol storage and transportation are calculated on a daily basis. Specifically, it includes:

[0041] The following relationship of green methanol storage and transportation in the sending region:

[0042]

[0043] And the following, taking the amount of methanol sent into the receiving region as the methanol inventory in the receiving region and not considering the methanol storage and transportation capacity constraint of the amount of methanol sent into the receiving region:

[0044]

[0045] In the formula, are respectively the storage, outward transportation volume and sent-in volume of green methanol in area s on day d; E M s,max is the upper limit of green methanol storage; d is the transportation delay time, which is related to the transportation distance.

[0046] Furthermore, considering that there is no methanol steam reforming for hydrogen production process in the sending region and no electricity-hydrogen-methanol process in the receiving region, the hydrogen supply and demand balance model is as follows:

[0047]

[0048] In the formula, is the amount of hydrogen purchased from outside in area s, is the hydrogen demand in area s.

[0049] Furthermore, the cost objective function of the upper-layer model system is as follows:

[0050] min{C}

[0051] C = C HSC + CO +C L +C Q +C H +C K +C E ,

[0052] where C is the total cost of the upper-layer scheduling model, C HSC is the cost of the hydrogen supply chain, C O is the operation and maintenance cost of the hydrogen storage tank, C L is the cost of transmitting electricity outside the power grid, C Q is the cost of penalty for curtailed energy, C H is the power generation cost of the thermal power unit, C K is the start-up and shut-down cost of the conventional generating unit, C E is the carbon emission cost of the conventional generating unit, and there is:

[0053]

[0054] where D is the scheduling period, λ T is the unit transportation price of methanol, D d is the transportation distance, λ e is the transmission and distribution price at the receiving end, E r,E,d， is the daily transmission and distribution electricity volume at the receiving end, λ p is the unit cost of hydrogen production from methanol, λ MH is the unit cost of hydrogen production from methanol reforming, λ E are the selling price of coal-based methanol and the environmental penalty cost coefficient respectively, λ H is the selling price of hydrogen; λ g is the unit operation and maintenance cost of the hydrogen storage tank; λ line is the unit cost of transmitting electricity outside the power grid, E line,d is the electricity volume transmitted outside; N h is the number of conventional generating units, E H,d,n is the power generation volume of the conventional generating unit in n days, f(E H,d,n ) is the power generation cost function of the conventional generating unit; U n,d is the start-up and shut-down state of the conventional generating unit in d days, 0 means shut down, 1 means start up, is the start-up and shut-down cost of the conventional generating unit in n; λ EH is the unit carbon emission cost of the conventional generating unit, g(E H,d,n ) is the carbon emission function of the conventional generating unit.

[0055] Furthermore, the power balance constraint is as follows:

[0056]

[0057] where E s,L,d is the daily electricity load demand of each region, E s,L,dDaily power transmission and distribution volume in each region; E r,d For the abandoned green energy power generation, E R,d For the sum of daily green energy power generation; N j,h 、N r,h Are the numbers of conventional generating units at the sending and receiving ends respectively;

[0058] Start - stop constraints of conventional generating units:

[0059]

[0060] In the formula, Is the start - up / shutdown time of unit n on day d - 1, Are the shortest start - up and shutdown durations respectively.

[0061] Furthermore, the operation and maintenance cost of the hydrogen fuel cell is as follows:

[0062]

[0063] Furthermore, the load shedding penalty cost is as follows:

[0064]

[0065] In the formula, T is the lower - layer scheduling period; λ B Is the unit operation and maintenance cost coefficient of the hydrogen fuel cell, P s,EB,t Is the output of the hydrogen fuel cell at time t in area s; λ F Is the load shedding penalty cost coefficient, P s,FL,t Is the load shedding volume at time t in area s.

[0066] Furthermore, the power balance constraint is as follows:

[0067]

[0068] The ramp - rate constraint of the conventional generating unit is as follows:

[0069] P n,down ≤(P H,t,n -P H,t-1,n )U n,t-1 U n,t ≤P n,up

[0070] In the formula, P n,up 、P n,down Are the upper and lower limits of the ramp - rate of unit n at adjacent times respectively.

[0071] Furthermore, the hydrogen fuel cell constraint is as follows:

[0072]

[0073] 0 ≤ P s,EB,t ≤ P EB,max

[0074] Where η EB is the power generation efficiency of the hydrogen fuel cell, the hydrogen consumption of the fuel cell of the hydrogen fuel at the current moment, P EB,max is the maximum power generation of the hydrogen fuel, LHV H2 is the lower heating value of hydrogen.

[0075] The present invention fully considers the characteristics of energy supply and consumption in different regions and the operating characteristics of each system. By reasonably scheduling the operation of equipment in the sending and receiving regions, the power and methanol transportation plans, hydrogen and methanol are produced using surplus renewable energy during periods and seasons with abundant renewable energy, and the surplus energy in the sending region is transferred to the receiving region by relying on the cheap storage and transportation of methanol, providing guarantee for the energy consumption in the receiving region, reducing external hydrogen purchase, thus effectively improving the operating economy of the cross-regional electricity-hydrogen coupling system, promoting the large-scale consumption of renewable energy, and enhancing the level of regional complementarity. The present invention can perform system operation scheduling on multiple time scales such as weekly, monthly, and quarterly, providing certain reference for the operation and planning of the cross-regional electricity-hydrogen coupling system, and having important significance and advantages. Brief Description of the Drawings

[0076] Figure 1 is a flowchart of the optimal scheduling method for the cross-regional electricity-hydrogen coupling system considering methanol storage and transportation in the embodiment of the present invention.

[0077] Figure 2 is a schematic structural diagram of the cross-regional electricity-hydrogen coupling system considering methanol storage and transportation in the embodiment of the present invention.

[0078] Figure 3 is a schematic diagram of methanol storage and transportation of the cross-regional electricity-hydrogen coupling system obtained with an annual scheduling period in the embodiment of the present invention. Detailed Embodiment

[0079] The present invention will be further described below in conjunction with embodiments, but it should not be understood that the above-mentioned subject scope of the present invention is limited to the following embodiments. Without departing from the above-mentioned technical idea of the present invention, various substitutions and changes made according to common general knowledge and customary means in the art should be included within the protection scope of the present invention.

[0080] The optimal scheduling method for the cross-regional electricity-hydrogen coupling system considering methanol storage and transportation in this embodiment is basically as Figure 1 shown, and the main steps are as follows:

[0081] 1) Determine the structure of the cross-regional electricity-hydrogen coupling system and obtain the basic data of the electricity-hydrogen coupling system in each region.

[0082] 1.1) As Figure 2As shown in the figure, the cross-regional electricity-hydrogen coupling system structure in this embodiment includes a sending area and a receiving area. Among them, the sending area includes a conventional generating unit, a photovoltaic unit, a wind turbine unit, an electric load, a hydrogen load, an electrolyzer, a hydrogen storage tank, a hydrogen fuel cell, a hydrogen + carbon dioxide to methanol reactor, and a methanol storage warehouse; the receiving area includes a conventional generating unit, an electric load, a hydrogen load, an electrolyzer, a hydrogen storage tank, a hydrogen fuel cell, and a methanol reforming to hydrogen reactor. Since the energy consumption in the receiving area is relatively large, the purchase of methanol needs to be considered. The sending and receiving areas are connected through a regional connection line and a methanol transportation network. The conventional generating unit in the system is a thermal power unit.

[0083] 1.2) The basic data of the electricity-hydrogen coupling system includes the time-series data of electricity and hydrogen loads in each region, the wind and light output data in the sending area, the parameters of conventional units, and the upper and lower limits of methanol storage and transportation and regional connection line operation, etc.

[0084] 2) Based on various flexible conversion paths such as PtX and methanol-hydrogen in the electricity-hydrogen coupling system, an energy storage and transportation model of the power grid-methanol-hydrogen supply chain is established.

[0085] The energy storage and transportation model of the power grid-methanol-hydrogen supply chain includes an electrolyzer model, a hydrogen storage tank model, a methanol spatio-temporal flexibility model, and a hydrogen supply and demand balance model.

[0086] 2.1) Electrolyzer model

[0087]

[0088] In the formula, m H2 s,E,t is the hydrogen production amount of the electrolyzer at time t in area s, S is the area set, including the sending area j and the receiving area r; η H2 is the operating efficiency of the electrolyzer; E s,E,t is the electricity input to the electrolyzer at time t in area s, LHV H2 is the lower heating value of hydrogen, which is 33.3 kWh / kg. E s,E,max is the upper limit of the electricity input to the electrolyzer;

[0089] 2.2) Hydrogen storage tank model

[0090]

[0091] In the formula, is the hydrogen storage capacity of the hydrogen storage tank at time t in area s; are the hydrogen storage and hydrogen release amounts at time t in area s respectively; and They are the upper limits of the hydrogen storage tank capacity, hydrogen input, and hydrogen release, respectively. Equation (3) represents the chronological relationship of the hydrogen storage capacity in the hydrogen storage tank at adjacent times, Equation (4) represents the safety constraint of the hydrogen storage tank capacity, Equations (5)-(6) represent the hydrogen storage and release constraints, and Equation (7) represents the input-output balance of hydrogen within the scheduling period.

[0092] 2.3) Methanol Spatiotemporal Flexibility Model

[0093] The methanol spatiotemporal flexibility model includes a hydrogen-methanol conversion model, a methanol reforming for hydrogen production model, and a methanol cross-regional seasonal storage and transportation model.

[0094] Hydrogen-Methanol Conversion Model:

[0095]

[0096] In the formula, is the methanol production at time t, η HM is the conversion coefficient of hydrogen plus carbon dioxide to methanol, m H2,M,t is the amount of green hydrogen input at time t, m H2,M,max is the upper limit of hydrogen input to the methanol reactor.

[0097] Methanol Reforming for Hydrogen Production Model:

[0098]

[0099] In the formula, is the hydrogen production from methanol at time t, η MH is the conversion coefficient of methanol steam reforming for hydrogen production, m M,H2,t is the amount of methanol input at time t, m M,H2,max is the upper limit of methanol input.

[0100] Methanol Cross-Regional Seasonal Storage and Transportation Model:

[0101] Considering the energy structures of the sending and receiving ends, assume that there is a green methanol warehouse in the sending region and methanol is considered for external transportation, and there is no corresponding methanol warehouse in the receiving region. And according to the characteristics of transportation, the changes in methanol storage and transportation are calculated in days, as shown below:

[0102]

[0103] In the formula, are the green methanol storage, external transportation volume, and incoming volume in region s on day d, respectively; E M s,max is the upper limit of green methanol storage; d is the transportation delay time, which is related to the transportation distance. Equation (12) represents the relationship between the storage and transportation of green methanol at the sending end. Since there is no green methanol storage warehouse at the receiving end and it is a methanol demand region, its methanol inventory is the incoming volume of methanol. And the sending end is a typical energy supply region, so the incoming volume of methanol is not considered. Equations (13)-(14) represent the constraints on the storage and transportation capacity of methanol.

[0104] 2.4) Hydrogen supply - demand balance model

[0105]

[0106] In the formula, is the amount of hydrogen purchased externally in area s, is the hydrogen demand in area s. Considering that the sending - end area is rich in renewable energy, the receiving - end area has a large energy demand, and there are energy conversion losses, there is no methanol steam reforming hydrogen production process in the sending - end area and no electricity - hydrogen - methanol process in the receiving - end area.

[0107] 3) Considering different system operation characteristics, establish a two - layer optimal economic dispatch model for the cross - regional electricity - hydrogen coupling system considering methanol storage and transportation, and determine the annual operation dispatch plan for the electricity - hydrogen coupling system in each region.

[0108] Among them, the two - layer optimal economic dispatch model of the cross - regional electricity - hydrogen coupling system includes an upper - layer daily dispatch model and a lower - layer hourly dispatch model.

[0109] 3.1) The upper - layer daily dispatch model takes a day as the dispatch time scale, aims to minimize the system cost, and considers power balance constraints, generation constraints of each unit, start - stop constraints of thermal power units, standby constraints of thermal power units, curtailment constraints, regional tie - line constraints, hydrogen supply - demand balance constraints, hydrogen and methanol purchase constraints, and constraints of electrolyzers, hydrogen storage tanks and methanol storage and transportation. Thus, determine the medium - and long - term daily start - stop arrangements of thermal power units and methanol transportation plans, providing boundaries for the lower - layer hourly dispatch. The objective function of the upper - layer model is as follows:

[0110] Min{C}

[0111] C=C HSC +C O +C L +C Q +C H +C K +C E ; (16)

[0112] In the formula, C is the total cost of the upper - layer dispatch model, C HSC is the cost of the hydrogen supply chain, C O is the operation and maintenance cost of the hydrogen storage tank, C L is the cost of electricity transmission outside the region, C Q is the curtailment penalty cost, C H is the generation cost of the thermal power unit, C K is the start - stop cost of the thermal power unit, C E is the carbon emission cost of the thermal power unit.

[0113]

[0114] where \(D = 365\) is the scheduling period, \(\lambda\) T is the unit transportation price of methanol, \(D\) d is the transportation distance, \(\lambda\) e is the receiving-end transmission and distribution price, \(\lambda\) p is the unit cost of hydrogen production from methanol, \(\lambda\) MH is the unit cost of hydrogen production from methanol reforming, \(\lambda\) E are the selling price of coal-based methanol and the environmental penalty cost coefficient respectively, \(\lambda\) H is the selling price of hydrogen; \(\lambda\) g is the unit operation and maintenance cost of the hydrogen storage tank; \(\lambda\) line is the unit cost of power transmission outside the power grid, \(E\) line,d is the amount of power transmitted outside; \(N\) h is the number of thermal power units, \(E\) H,d,n is the power generation of thermal power unit \(n\) in \(n\) days, \(f(E\) H,d,n ) is the power generation cost function of the thermal power unit; \(U\) n,d is the start-stop state of the thermal power unit in \(d\) days, 0 means off, 1 means on, is the start-stop cost of thermal power unit \(n\); \(\lambda\) EH is the unit carbon emission cost of the thermal power unit, \(g(E\) H,d,n ) is the carbon emission function of the thermal power unit.

[0115] Among them, the power balance constraint and the start-stop constraint of the thermal power unit in the upper-layer scheduling model are as follows:

[0116] Power balance constraint:

[0117]

[0118] where \(E\) s,L,d is the daily power load demand of each region, \(E\) s,E,d is the transmission and distribution power of each region; \(E\) r,d is the amount of curtailed wind and light, \(E\) R,d is the sum of the daily power generation of wind and light; \(N\) j,h 、\(N\) r,h are the numbers of sending-end and receiving-end thermal power units respectively.

[0119] Start-stop constraint of thermal power unit:

[0120]

[0121] where is the start-up (shutdown) time of unit \(n\) on day \(d - 1\), are the shortest start-up and shutdown durations respectively.

[0122] 3.2) Lower - layer hourly scheduling model Under the start - stop and methanol transportation plans of thermal power units determined by the upper layer, with an hourly scheduling time scale and aiming at minimizing the system cost, compared with the upper layer, the lower - layer system cost reduces the start - stop cost of thermal power units and the transportation cost in the hydrogen supply chain, and increases the operation and maintenance cost of hydrogen fuel cells and the load - shedding penalty cost. Considering the power balance constraint, the ramp - up and ramp - down constraint of thermal power units, the energy curtailment constraint, the output constraint of each unit, the hydrogen supply - demand balance constraint, the operation constraint of hydrogen fuel cells, and the constraints of electrolyzers, hydrogen storage tanks and methanol storage and transportation, the annual operation and scheduling plan of the regional power - hydrogen coupling system is determined accordingly.

[0123] In the lower - layer hourly scheduling model, the parameters with the counting unit of day (d) in the cost calculation are changed to the parameters with the technical unit of hour (t). Thus, all daily - based electrical energy parameters E become hourly - based power parameters P.

[0124] Then there is the system cost objective function

[0125] Min{C h}

[0126]

[0127] Among them, is the hydrogen supply chain cost without considering the transportation cost. The operation and maintenance cost of hydrogen fuel cells and the load - shedding penalty cost are as follows:

[0128]

[0129] In the formula, T is the lower - layer scheduling period, which is 8760 h; λ B is the unit operation and maintenance cost coefficient of hydrogen fuel cells, P s,EB,t is the output of the hydrogen fuel cell at time t in area s; λ F is the load - shedding penalty cost coefficient, P s,FL,t is the load - shedding amount at time t in area s;

[0130] The constraints that are different or need to be emphasized in the lower layer compared with the upper layer include the power balance constraint, the ramp - up and ramp - down constraint of thermal power units, and the hydrogen fuel cell constraint.

[0131] Power balance constraint:

[0132]

[0133] Ramp - up and ramp - down constraint of thermal power units:

[0134] P n,down (P H,t,n -P H,t-1,n )U n,t-1 U n,t P n,up (24)

[0135] In the formula, P n,up and P n,down are respectively the upper and lower limits of the ramp rate of the unit at n adjacent moments.

[0136] Hydrogen fuel cell constraint:

[0137]

[0138] 0 ≤ P s,EB,t ≤ P EB,max (26)

[0139] In the formula, η EB is the power generation efficiency of the hydrogen fuel cell, P EB,max is the maximum power generation of the hydrogen fuel, and LHV H2 is the lower heating value of hydrogen.

[0140] 4) Application analysis:

[0141] To facilitate the description of the application of this method, a numerical example analysis is carried out taking a certain regional power grid in the northwest as an example. In this system, the installed thermal power capacity in the sending area is 178 GW, the installed wind and photovoltaic capacities are 90 GW and 139.5 GW respectively, and the peak power and hydrogen loads are 95299 MW / h and 2516 t / d; the installed thermal power capacity in the receiving area is 83.6 GW, and the peak power and hydrogen loads are 73520 MW / h and 9743 t / d. The regional electrolyzer capacity is 22800 MW, the hydrogen storage tank capacity is 380 tons, the hydrogen fuel cell is 50 MW, and the capacity of the connection line between the sending and receiving areas is 25000 MW.

[0142] 4.1) Set up a comparison group: In the sending and receiving areas, methanol storage and transportation are not considered, and only the connection line is used to transfer energy between regions;

[0143] 4.2) After obtaining the dispatching plans of the power-hydrogen coupling systems in the sending and receiving areas of the present invention and the comparison group, the total system cost, the abandoned energy, and the hydrogen supply chain cost in the two different cases can be calculated as shown in Table 1.

[0144] Table 1 Comparison of calculation results between the proposed scheme and the comparison scheme

[0145]

[0146] As can be seen from Table 1, compared with the optimized dispatching scheme of the cross-regional power-hydrogen coupling system without considering methanol storage and transportation, the system operation cost of the optimized dispatching scheme of the cross-regional power-hydrogen coupling system considering methanol storage and transportation is reduced by 48.219 billion yuan, a year-on-year decrease of 11.36%; the abandoned energy is reduced by 3264 GWh, a year-on-year decrease of 31.49%. It can be seen that the economy and the renewable energy consumption of the system are significantly improved after considering methanol storage and transportation.

[0147] As can be seen from Figure 3 it, considering methanol storage and transportation, the system can produce methanol using surplus renewable energy during periods with abundant renewable energy or seasonally, and store and transport the methanol, achieving cross-time and even cross-season energy transfer, improving the flexibility of the system, thus promoting the consumption of renewable energy in the system. At the same time, relying on the flexible and inexpensive transportation of methanol, it supports the energy use of the green economy in the receiving region, reduces the purchase of external hydrogen, and further improves the operating economy of the system and the level of regional mutual assistance.

[0148] In summary, it can be seen that the optimized scheduling method for the cross-regional electricity-hydrogen coupling system considering methanol storage and transportation is feasible and has certain application value.

[0149] The above description is only the implementation mode of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. An optimized scheduling method for a cross-regional electricity-hydrogen coupling system considering methanol storage and transportation, characterized in that, It includes the following steps: 1) Determine the structure of the cross-regional electricity-hydrogen coupling system considering methanol storage and transportation, and obtain the basic data of the regional electricity-hydrogen coupling system. Among them, the sending region includes a hydrogen + carbon dioxide to methanol reactor and a methanol storage warehouse, and the receiving region includes a methanol reforming to hydrogen reactor. The sending and receiving regions are connected by a regional connection line and a methanol transportation network. Conventional power generation units, green energy power generation units, and hydrogen fuel cells are installed in both the sending and receiving regions; 2) Establish an energy storage and transportation model of the power grid-methanol-hydrogen supply chain with corresponding constraint conditions. The energy storage and transportation model of the power grid-methanol-hydrogen supply chain includes an electrolyzer model, a hydrogen storage tank model, a methanol spatio-temporal flexibility model, and a hydrogen supply and demand balance model; In the hydrogen storage tank model, it includes the sequential relationship of the hydrogen storage capacity of the hydrogen storage tank at adjacent times, the safety constraint of the hydrogen storage tank capacity, the hydrogen storage and hydrogen release constraints, and the input and output balance relationship of hydrogen within the scheduling period; The methanol spatio-temporal flexibility model includes a hydrogen-methanol conversion model, a methanol reforming to hydrogen model, and a methanol cross-regional seasonal storage and transportation model; In the methanol cross-regional seasonal storage and transportation model, it includes the methanol storage and transportation relationship at the sending end and the methanol storage and transportation capacity constraint; 3) Based on the cross-regional electricity-hydrogen coupling system considering methanol storage and transportation, establish an optimal economic dispatch model to determine the annual operation dispatch plan of the regional electricity-hydrogen coupling system; The optimal economic dispatch model includes an upper-layer daily dispatch model. Based on the upper-layer daily dispatch model, with a day as the dispatch time scale, the annual operation dispatch plan of the system is obtained with the goal of minimizing the system cost; The system cost shall include the hydrogen supply chain cost C obtained from the power grid - methanol - hydrogen supply chain energy storage and transportation model HSC ; Among the considered constraint conditions, it is necessary to include the hydrogen supply and demand balance constraint, electrolyzer, hydrogen storage tank, and methanol storage and transportation constraints based on the aforementioned energy storage and transportation model of the power grid-methanol-hydrogen supply chain; and the power balance constraint and the start-stop constraint of the conventional power generation unit; The annual operation dispatch plan of the system includes the medium- and long-term daily start-stop arrangements of the conventional power generation unit and the methanol transportation plan.

2. The method according to claim 1, characterized in that, The optimal economic dispatch model also includes a lower-layer hourly dispatch model. Based on the lower-layer hourly dispatch model, with an hour as the dispatch time scale under the start-stop of the conventional power generation unit and the methanol transportation plan determined by the upper-layer daily dispatch model, the annual operation dispatch plan of the system is obtained with the goal of minimizing the system cost; The system cost of the lower-layer hourly dispatch model needs to include the operation and maintenance cost of the hydrogen fuel cell and the load shedding penalty cost, and does not include the start-stop cost of the conventional power generation unit and the transportation cost part of the hydrogen supply chain cost; Among the considered constraint conditions, it is necessary to include the power balance constraint, the ramp constraint of the conventional power generation unit, and the hydrogen fuel cell constraint, and does not include the power balance constraint and the start-stop constraint of the conventional power generation unit; The annual operation dispatch plan of the system includes the dispatch output plan of each unit at the sending and receiving ends, the power transmission plan, and the operation plan of each device in the hydrogen energy subsystem.

3. The method according to claim 1, wherein The electrolyzer model is as follows: 0 ≤ E s,E,t ≤ E s,E,max In the formula, is the hydrogen production of the electrolytic cell at time t in area s, S is the area set, including the sending end area j and the receiving end area r; η H2 is the operating efficiency of the electrolytic cell; E s,E,t is the electricity input to the electrolytic cell at time t in area s, LHV H2 is the lower heating value of hydrogen, E s,E,max is the upper limit of the electricity input to the electrolytic cell.

4. The method according to claim 1, characterized in that The hydrogen storage tank model includes: The sequential relationship of the hydrogen storage capacity of the hydrogen storage tank at adjacent times is as follows: And the safety constraint of the hydrogen storage tank capacity is as follows: And the hydrogen storage and hydrogen release constraints are as follows: And the input and output balance of hydrogen within the scheduling period is as follows In the formula, is the hydrogen storage capacity of the hydrogen storage tank in area s at time t; are the hydrogen storage and hydrogen release amounts in area s at time t, respectively; and are the upper limits of the hydrogen storage tank capacity, hydrogen input amount, and hydrogen release amount, respectively.

5. The method according to claim 1, characterized in that The hydrogen-methanol conversion model is as follows: In the formula, is the methanol production at time t, and η HM is the conversion coefficient of hydrogen plus carbon dioxide to methanol, m H2,M,t is the amount of green hydrogen input at time t, m H2,M,max is the upper limit of hydrogen input to the methanol reactor.

6. The method according to claim 1, wherein The methanol reforming to hydrogen model is as follows: In the formula, is the hydrogen production amount of methanol at time t, and η MH is the hydrogen production conversion coefficient of methanol steam reforming, m M,H2,t is the methanol input amount at time t, and m M,H2,max is the upper limit of methanol input.

7. The method according to claim 1, wherein In the seasonal methanol storage and transportation model across regions, it is assumed that there is a green methanol warehouse in the sending region and methanol is considered for external transportation. There is no corresponding methanol warehouse in the receiving region, and the changes in methanol storage and transportation are calculated on a daily basis. Specifically, it includes: The following storage and transportation relationship of green methanol in the sending region: And the following, taking the methanol input volume in the receiving region as the methanol inventory in the receiving region, and not considering the methanol storage and transportation capacity constraint of the methanol input volume in the receiving region: In the formula, are respectively the storage, external delivery volume, and delivery volume of green methanol in the s area for d days; E M s,max is the upper limit of green methanol storage; d is the transportation delay time, which is related to the transportation distance.

8. The method according to claim 1, characterized in that, Considering that there is no methanol steam reforming for hydrogen production process in the sending region and no electricity-hydrogen-methanol process in the receiving region, the hydrogen supply and demand balance model is as follows: In the formula, is the amount of hydrogen purchased from outside the s region, is the hydrogen demand in the s region.

9. The method according to claim 1, characterized in that The cost objective function of the system in the upper-layer daily scheduling model is as follows: min{C} C=C HSC +C O +C L +C Q +C H +C K +C E , Where C is the total cost of the upper-level scheduling model, C HSC is the cost of the hydrogen supply chain, C O is the operation and maintenance cost of the hydrogen storage tank, C L is the cost of exporting electric energy, C Q is the penalty cost of curtailed energy, C H is the power generation cost of the thermal power unit, C K is the start-up and shut-down cost of the conventional generating unit, C E is the carbon emission cost of the conventional generating unit, and we have: where D is the scheduling period, λ T is the unit transportation price of methanol, D d is the transportation distance, λ e is the receiving-end transmission and distribution price, E r,E,d， is the receiving-end daily transmission and distribution volume, λ p is the unit cost of hydrogen production from methanol, λ MH is the unit cost of hydrogen production by methanol reforming, λ E are the selling price of coal-based methanol and the environmental penalty cost coefficient respectively, λ H is the selling price of hydrogen; λ g is the unit operation and maintenance cost of the hydrogen storage tank; λ line is the unit cost of external power transmission of electric energy, E line,d is the external power transmission volume; N h is the number of conventional generating units, E H,d,n is the power generation volume of the conventional generating unit in n days, f(E H,d,n ) is the power generation cost function of the conventional generating unit; U n,d is the start-stop state of the conventional generating unit in d days, 0 means off, 1 means on, is the start-stop cost of the conventional generating unit in n; λ EH is the unit cost of carbon emissions for a conventional generating unit, g(E H,d,n ) is the carbon emission function of a conventional generating unit.

10. The method according to claim 1, wherein The power balance constraint is as follows: Where, E s,L,d is the daily electricity load demand of each region, and E s,L,d is the daily power transmission and distribution volume of each region; E r,d is the generated electricity of abandoned green energy, and E R,d is the sum of the daily generated electricity of green energy; N j,h and N r,h are the numbers of conventional generating units at the sending and receiving ends respectively; Start-stop constraint of conventional generating units: wherein, is the startup / shutdown time of unit n on the (d - 1)th day, are the shortest startup and shutdown durations respectively.

Images