A coordinated scheduling method for energy and frequency reserve in electricity-hydrogen system based on successive feasible convex relaxation

Abstract

This application applies to the field of power-gas network collaborative optimization technology and provides a method for coordinated scheduling of energy, frequency, and reserve reserves in an electric-hydrogen system based on successive feasible convex relaxation. The method includes: first, obtaining operating parameters and multi-scenario load data for the power grid, gas grid, and renewable output; establishing a power, hydrogen electrolysis, and hydrogen-blended natural gas model that includes generator sets and three-state electrolyzers; taking into account frequency control reserve and spinning reserve ancillary services; relaxing a non-convex model with bilinear constraints into a convex model using McCormick envelope; and alternately solving the convex relaxation and the original non-convex model using successive feasible point-convex hull relaxation, with the goal of minimizing total cost. By introducing a three-state electrolyzer model and employing a successive feasible point-convex hull relaxation method, the method fully exploits the frequency control reserve and spinning reserve potential provided by the electrolyzer's hot standby state, improving scheduling accuracy, reducing system operating costs, and alleviating the backup pressure on traditional units.

Description

Technical Field

[0001] The present application belongs to the technical field of coordinated optimization of electric power and natural gas networks, and in particular relates to a method for coordinated scheduling of energy and frequency reserves in an electric-hydrogen system based on successive feasible convex relaxation. Background Art

[0002] The global energy system is undergoing a structural transformation from a fossil fuel-dominated to a renewable energy-dominated system. However, the inherent intermittent and uncertain nature of renewable energy poses significant challenges to system operation. Against this backdrop, integrated energy systems based on the coupling of electricity, hydrogen, and gas offer significant advantages. By converting surplus renewable energy into green hydrogen through electrolyzers and injecting it into the natural gas pipeline network, they can both achieve large-scale renewable energy consumption and effectively enhance system operational flexibility. Specifically, as controllable power loads and flexible regulation units, the rapid response of electrolyzers complements the advantages of traditional gas-fired generators. When power fluctuates, electrolyzers can provide auxiliary services such as frequency regulation to the grid through rapid startup and shutdown and power regulation. This multi-energy coupling coordinated regulation mechanism enables electricity, hydrogen, and gas hybrid integrated energy systems to adapt to the supply and demand balance requirements of high renewable energy penetration scenarios. Therefore, as a key vehicle for balancing energy supply and demand, it is crucial to fully tap and utilize the flexibility potential of electrolyzers in electricity, hydrogen, and gas hybrid integrated energy systems, leveraging their rapid response capabilities to provide auxiliary services such as frequency regulation to improve the reliability and economic efficiency of integrated energy systems.

[0003] However, traditional electrolyzer models usually use a two-state model (operating and shutting down), ignoring the flexibility and economic potential of the hot standby state in providing backup auxiliary services during actual electrolyzer operation. In addition, the optimization of this integrated energy system that takes into account equipment start-up and shutdown and involves unit combinations is often a mixed integer nonlinear optimization problem. As a result, the current electricity-hydrogen-gas hybrid integrated energy system is difficult to efficiently and accurately solve the coordinated scheduling of energy, frequency and backup under multi-media coupling. Summary of the Invention

[0004] The embodiment of the present application provides a method for coordinated scheduling of energy, frequency and backup in an electric-hydrogen-gas system based on successive feasible convex relaxation, which can solve the problem that it is difficult to efficiently and accurately solve the coordinated scheduling of energy, frequency and backup in the current electric-hydrogen-gas hybrid integrated energy system under multi-medium coupling.

[0005] In the first aspect, the embodiment of the present application provides a method for coordinated scheduling of energy and frequency reserve of an electric-hydrogen-gas system based on successive feasible convex relaxation, comprising the following steps: Step 1, obtaining the network coefficients and operating coefficients of the power grid and gas grid models, the network coefficients including the power grid topology, gas grid topology, line resistance and impedance, natural gas, and hydrogen calorific value, the operating coefficients including the power generation coefficient of the generator set, the wind power photovoltaic inverter coefficient, gas source parameters, electrolyzer device parameters, and pressure station parameters; Step 2, obtaining dynamic operation scenario data under different time sections, the dynamic operation scenario data including power grid load demand, gas grid load demand, wind power photovoltaic output, frequency control reserve demand, and rotating reserve demand scenario data; Step 3, combining the network coefficients, the operating coefficients, and the dynamic operation scenario data, taking the total cost of the electric-hydrogen-gas hybrid integrated energy system as the objective function, according to First, establish an electric power system operation model considering the combination of units and electrolyzers, an operation model providing frequency control reserves and spinning reserve auxiliary services, and a dynamic natural gas system operation model taking into account pipeline hydrogen blending, and combine the objective function with the three established models to construct a non-convex model for the optimal scheduling of the electric-hydrogen-gas hybrid integrated energy system considering the frequency control reserve, spinning reserve and unit combination; Step 4, for the non-convex model for the optimal scheduling of the electric-hydrogen-gas hybrid integrated energy system established in Step 3, perform convex relaxation on all bilinear terms in the non-convex constraints in the model through the McCormick envelope to obtain the convex model for the optimal scheduling of the electric-hydrogen-gas hybrid integrated energy system; Step 5, use the successive feasible point-convex hull relaxation method to alternately solve the convex model for the optimal scheduling of the electric-hydrogen-gas hybrid integrated energy system and the non-convex model for the optimal scheduling of the electric-hydrogen-gas hybrid integrated energy system to obtain the optimal scheduling method.

[0006] In a possible implementation of the first aspect, the objective function in step 3 is specifically as follows:

[0007] (A-1)

[0008] Among them, the subscript Indicates a generator set, including coal-fired units and gas-fired units; Indicates a time section; subscript Indicates electrolytic cell; subscript Indicates power load; subscript Indicates natural gas source; subscript Indicates gas load; Represents a collection of coal-fired units; Represents a collection of gas generator sets; It represents the unit startup cost of the generator set; represents the unit shutdown cost of the generator set; It represents the unit reserve cost of the spinning reserve of the generator set; It represents the unit reserve cost of the spinning reserve of the generator set; represents the unit power generation cost of coal-fired units; Indicates the unit non-fuel operation and maintenance cost of the gas unit; It represents the unit cost of gas-fired units for frequency control reserve; represents the unit cost of gas-fired units in standby mode under frequency control reserve; represents the unit startup cost of the electrolyzer; It represents the unit load shedding cost; Indicates the unit gas supply cost of the gas source; represents the unit gas load cost; Indicates the starting action of the generator set; Indicates the shutdown action of the generator set; Indicates the spinning reserve capacity provided by the generator set; Indicates the reserve capacity under spinning reserve provided by the generator set; Indicates the active power generated by the generator set; Indicates the frequency control reserve upper spare capacity provided by the gas unit; Indicates the spare capacity under frequency control reserve provided by gas units; Indicates the start-up action of the electrolytic cell; Indicates the required active power of the power load; Indicates the active power actually supplied to the power load; Indicates the gas supply volume of the natural gas source; Indicates the required mass flow rate of natural gas load; Indicates the mass flow rate actually supplied to the natural gas load;

[0009] The first term of the objective function in formula (A-1) is the startup and shutdown cost and spinning reserve cost of the generator set, which includes coal-fired units and gas-fired units. The second term is the power generation cost of the coal-fired unit. The third term is the cost of power generation and frequency control reserve provision for the gas-fired unit. The cost of power generation and frequency control reserve provision includes upper reserve cost and lower reserve cost. The fourth term is the startup cost of the electrolyzer. The fifth term is the cost of shedding electric load. The sixth term is the gas supply cost of the natural gas source. The seventh term is the cost of shedding gas load.

[0010] The power system operation model considering the combination of units and electrolyzers in step 3 is as follows:

[0011] (A-2)

[0012] (A-3)

[0013] (A-4)

[0014] (A-5)

[0015] (A-6)

[0016] (A-7)

[0017] (A-8)

[0018] (A-9)

[0019] (A-10)

[0020] (A-11)

[0021] (A-12)

[0022] (A-13)

[0023] (A-14)

[0024] (A-15)

[0025] (A-16)

[0026] (A-17)

[0027] (A-18)

[0028] (A-19)

[0029] (A-20)

[0030] (A-21)

[0031] (A-22)

[0032] (A-23)

[0033] Among them, the subscript and Indicates power node; subscript Represented by power nodes To power node Line; subscript Indicates new energy units; subscript represents the reference bus; Representation and Node the collection of connected generator sets; Representation and Node A collection of connected new energy units; Representation and Node The set of connected nodes; Representation and Node the collection of connected electrical loads; Representation and Node a collection of connected electrolytic cells; Represents new energy units In the period Active power connected to the grid; For slave nodes To Node Active power of the line; For slave nodes To Node The square of the current in the circuit; For slave nodes To Node The resistance of the circuit; Indicates the hydrogen production power of the electrolyzer; Indicates the reactive power generated by the generator set; Represents new energy units In the period The online reactive power; For slave nodes To Node Reactive power of the line; For slave nodes To Node reactance of the inter-line; is the reactive power actually supplied to the power load; For nodes The square of the voltage amplitude; and For nodes and nodes The voltage phase angle; and Node The minimum and maximum squared voltage amplitudes; For slave nodes To Node the capacity of the inter-line; The reactive power required by the power load; Predict the active power of new energy units on the previous day; Predict reactive power for new energy units on the day before; is the voltage phase angle of the reference bus; is an integer variable, indicating the operating status of the generator set in period t, 1 represents the operating status, and 0 represents the non-operating status; and Respectively for units The minimum and maximum active power generation; and Respectively for units Minimum and maximum generated reactive power; Indicates the unit Maximum climbing power; Indicates the unit Minimum continuous running time after startup; and are the minimum and maximum power consumption of the electrolyzer during operation; The power consumed when the electrolyzer is in hot standby mode; is an integer variable, indicating the operating state of the electrolytic cell in time period t, 1 represents the operating state, and 0 represents the non-operating state; is an integer variable, indicating the hot standby state of the electrolytic cell in time period t, 1 means it is in hot standby state, and 0 means it is not in hot standby state; is the mass flow rate of hydrogen produced by the electrolyzer; is the higher calorific value of hydrogen, which is taken as 142MJ / kg; is the hydrogen production conversion efficiency of the electrolyzer; is an integer variable, indicating the closed state of the electrolytic cell in time period t, 1 for closed state and 0 for open state;

[0034] Formula (A-2) is the node active power balance equation; Formula (A-3) is the node reactive power balance equation; Formula (A-4) is the relationship between node voltage and line power; Formula (A-5) is the relationship between voltage phase angle and line power; Formula (A-6) is the second-order cone relaxation form of branch power flow; Formula (A-7) is the upper and lower limit constraints of node voltage; Formula (A-8) is the line transmission capacity constraint; Formula (A-9) is the active load demand constraint; Formula (A-10) is the upper and lower limit constraints of reactive load; Formula (A-11) is the grid-connected renewable energy active power constraint; Formula (A-12) is the grid-connected renewable energy reactive power constraint; Formula (A-13) stipulates that the phase angle of the reference bus is 0; Formula (A-14) is the generator in operation The upper and lower limits of active power output are set when the generator is in the running state; Formula (A-15) is the upper and lower limits of reactive power output when the generator is in the running state; Formula (A-16) is the active power ramp constraint of the generator; Formula (A-17) is the start-stop action and state constraint of the generator; Formula (A-18) is the shortest running time constraint of the generator; Formula (A-19) is the upper and lower limits of power when the electrolyzer is in the running state or hot standby state; Formula (A-20) is the efficiency constraint of the electrolyzer when producing hydrogen by electrolysis; Formula (A-21) is the state constraint of the electrolyzer, which can only be in the running state, hot standby state or shut down state at the same time; Formula (A-22) is the startup state constraint of the electrolyzer; Formula (A-23) restricts the electrolyzer from directly switching from the shut down state to the hot standby state;

[0035] The operational model for providing frequency control reserve and spinning reserve ancillary services in step 3 is as follows:

[0036] (A-24)

[0037] (A-25)

[0038] (A-26)

[0039] (A-27)

[0040] (A-28)

[0041] in, Spinning reserve upper spare capacity provided for electrolysers; Spare capacity for required spinning reserve; Spinning reserve lower reserve capacity provided for electrolysers; The required spinning reserve capacity; Frequency control reserve capacity provided for electrolysers; Reserve capacity for required frequency control; Frequency control reserve capacity provided for electrolysers; Reserve capacity for required frequency control;

[0042] Formula (A-24) indicates that the spinning reserve is jointly provided by the coal-fired units, gas-fired units, and electrolyzers; Formula (A-25) indicates that the frequency control reserve is jointly provided by the gas-fired units and electrolyzers; Formula (A-26) indicates the upper and lower limit constraints and ramping constraints for the spinning reserve provided by the coal-fired units; Formula (A-27) indicates the upper and lower limit constraints and ramping constraints for the spinning reserve and frequency control reserve provided by the gas-fired units; Formula (A-28) indicates the capacity limit for the electrolyzer to provide spinning reserve and frequency control reserve in the operating and hot standby states;

[0043] The dynamic natural gas system operation model taking into account pipeline hydrogen blending in step 3 is as follows:

[0044] (A-29)

[0045] (A-30)

[0046] (A-31)

[0047] (A-32)

[0048] (A-33)

[0049] (A-34)

[0050] (A-35)

[0051] (A-36)

[0052] (A-37)

[0053] (A-38)

[0054] (A-39)

[0055] (A-40)

[0056] (A-41)

[0057] (A-42)

[0058] (A-43)

[0059] (A-44)

[0060] (A-45)

[0061] (A-46)

[0062] (A-47)

[0063] (A-48)

[0064] (A-49)

[0065] Among them, the subscript and Represents a natural gas node; subscript Represents a natural gas node and gas nodes Pipes between; collections For gas nodes A collection of connected nodes; a collection For gas nodes A collection of connected natural gas sources; a collection For gas nodes A collection of connected electrolytic cells; a collection For gas nodes A collection of connected booster stations; a collection For gas nodes A collection of connected gas units; a collection For gas nodes connected load collection; is the density of the natural gas-hydrogen mixture in the natural gas pipeline; is the time section length; and are the gas mass flow rates at the beginning and end of the natural gas pipeline respectively; is the cross-sectional area of ​​the natural gas pipeline; is the length of the natural gas pipeline; and is the pressure at the natural gas node; is the mass flow rate of gas in the natural gas pipeline; is the friction factor of turbulent flow in natural gas pipelines; is the diameter of the natural gas pipeline; is the mass fraction of hydrogen in the natural gas pipeline; and are the mass fractions of hydrogen at the beginning and end of the natural gas pipeline, respectively; is the pressure of the pipeline; is the specific gas constant of the natural gas-hydrogen mixture in the pipeline; is the compressibility coefficient of the pipeline; is the ambient temperature; is the specific gas constant of hydrogen; is the specific gas constant of natural gas; is the mass flow rate of gas in the boosting station; is the mass flow rate of natural gas consumed by the gas generating unit; is the required mass flow rate of natural gas-hydrogen mixture; is the higher calorific value of natural gas, which is taken as 53.37MJ / kg; is the hydrogen mass fraction at the natural gas node; is the mass fraction of hydrogen in the compression station; is the power generation efficiency of the gas-fired unit; The maximum mass fraction of hydrogen injected into the natural gas pipeline; The maximum mole fraction of hydrogen injected into a natural gas pipeline; and are the densities of hydrogen and natural gas under standard conditions respectively; and is the minimum and maximum value of pipeline pressure; and The minimum and maximum values ​​of the gas mass flow rate of the natural gas source; The maximum value of the gas supply ramp rate of the natural gas source; and are the minimum and maximum values ​​of gas density in natural gas pipelines, respectively; and are the minimum and maximum values ​​of the boosting coefficient of the boosting station respectively; and are the minimum and maximum values ​​of the gas mass flow rate in the compression station, respectively;

[0066] Equation (A-29) represents the conservation of mass of the natural gas-hydrogen mixture in the pipeline; Equation (A-30) represents the conservation of momentum of the natural gas-hydrogen mixture in the pipeline; Equation (A-31) is the hydrogen advection transport equation, which represents the conservation of mass of hydrogen in the pipeline; Equation (A-32) is the state equation, which shows that the pressure and density of the natural gas-hydrogen mixture are related to the temperature; Equation (A-33) is the calculation rule for the specific gas constant of the natural gas-hydrogen mixture; Equation (A-34) is the formula for calculating the average pressure of the natural gas-hydrogen mixture in the pipeline; Equation (A-35) is the formula for calculating the average mass flow rate of the natural gas-hydrogen mixture in the pipeline; Equation (A-36) is the formula for calculating the average mass fraction of hydrogen in the pipeline; Equation (A-37) is the nodal mass flow balance equation for the natural gas-hydrogen mixture; Equation (A-38) represents the energy conversion relationship between the demand for the natural gas-hydrogen mixture and the demand for the original natural gas; Equation (A-39) Formula (A-40) represents the node mass flow balance equation for hydrogen; Formula (A-41) represents the relationship between the maximum hydrogen injection mole fraction and the maximum hydrogen injection mass fraction in the pipeline; Formula (A-42) is the limitation on the hydrogen injection mass fraction in the pipeline; Formula (A-43) is the pressure limitation of the natural gas node; Formula (A-44) is the gas supply limitation of the natural gas source; Formula (A-45) is the ramp constraint of the natural gas source; Formula (A-46) is the gas density limitation of the pipeline; Formula (A-47) is the boost ratio constraint of the boosting station; Formula (A-48) is the gas mass flow limitation of the boosting station; Formula (A-49) is the limitation on natural gas demand.

[0067] Optionally, in another possible implementation of the first aspect, in step 4 above, the bilinear terms in all non-convex constraints in the model are convexly relaxed using the McCormick envelope to obtain a convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system, as follows:

[0068] The six nonlinear constraints (A-30), (A-31), (A-32), (A-38), (A-39), and (A-40) in the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system established in step 3 are transformed and the bilinear terms therein are relaxed using the McCarmick envelope, as follows:

[0069] Convert (A-30)-(A-32) to:

[0070] (A-50)

[0071] (A-51)

[0072] (A-52)

[0073] Convert (A-38)-(A-40) to:

[0074] (A-53)

[0075] (A-54)

[0076] (A-55)

[0077] in, , is the auxiliary variable introduced;

[0078] Combining equations (A-1)-(A-29), (A-33)-(A-37), (A-41)-(A-49), and (A-51)-(A-55), we obtain the convex model for the optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system.

[0079] Optionally, in another possible implementation of the first aspect, in step 5 above, a successive feasible point-convex hull relaxation method is used to alternately solve a convex model for optimal scheduling of an electricity-hydrogen-gas hybrid integrated energy system and a non-convex model for optimal scheduling of an electricity-hydrogen-gas hybrid integrated energy system, as follows:

[0080] Step 51: Solve the optimal scheduling convex model of the electricity-hydrogen-gas hybrid integrated energy system using the GUROBI solver to obtain the target value lower limit and scheduling strategy. The scheduling strategy includes the output and start-stop status of the generator set and electrolyzer, the power grid flow, the wind power and photovoltaic power output, the natural gas source output, and the flow rate of the gas network pipeline;

[0081] Step 52: Solve the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system using a fixed scheduling strategy to obtain the upper limit of the target value and the values ​​of all variables. The fixed scheduling strategy is to fix the values ​​of all variables included in the scheduling strategy in step 51 and solve the model using the DICOPT solver.

[0082] Step 53, referring to the values ​​of the variables corresponding to the bilinear terms in the convex relaxation constraints obtained from the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system, narrowing the upper and lower limits of the variables in the bilinear terms in the convex relaxation constraints to solve the convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system and increase the lower limit of the target value;

[0083] Step 54: solving the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system according to the fixed scheduling strategy, and updating the upper limit of the target value;

[0084] Step 55, repeat steps 53 and 54 until the difference between the upper limit of the target value and the lower limit of the target value is less than the preset value, and determine the target value and scheduling strategy obtained at this time as the optimal scheduling method.

[0085] Beneficial effect: In the technical solution of the present application, the network coefficients and operation coefficients of the power grid and gas grid models are first obtained, and then the dynamic operation scenario data under different time sections are obtained. Then, the network coefficients, operation coefficients and dynamic operation scenario data are combined, and the total cost of the electric-hydrogen-gas hybrid integrated energy system is used as the objective function. The power system operation model considering the combination of units and electrolyzers, the operation model providing frequency control reserve and rotating standby auxiliary services, and the dynamic natural gas system operation model taking into account pipeline hydrogen blending are successively established. The objective function is combined with the three established models to construct a system considering frequency A non-convex model for the optimal scheduling of an electric-hydrogen-gas hybrid integrated energy system with frequency control reserve, spinning reserve, and unit combination is constructed. Next, the bilinear terms in all non-convex constraints of the established non-convex model for the optimal scheduling of the electric-hydrogen-gas hybrid integrated energy system are convexly relaxed using the McCormick envelope to obtain a convex model for the optimal scheduling of the electric-hydrogen-gas hybrid integrated energy system. Finally, the convex model and the non-convex model for the optimal scheduling of the electric-hydrogen-gas hybrid integrated energy system are alternately solved using the successive feasible point-convex hull relaxation method to obtain the optimal scheduling method. By introducing a three-state model of the electrolyzer and adopting the successive feasible point-convex hull relaxation method, the frequency control reserve and spinning reserve potential provided by the hot standby state of the electrolyzer are fully exploited, improving scheduling accuracy, reducing system operating costs, and alleviating the reserve pressure of traditional units. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0087] Figure 1 This is a flow chart of a method for coordinated scheduling of energy and frequency reserves in an electricity-hydrogen system based on successive feasible convex relaxation provided in one embodiment of the present application;

[0088] Figure 2 is a schematic diagram of the amount of spinning reserve (SR) provided by a coal-fired unit under a three-state model provided in one embodiment of the present application;

[0089] Figure 3 is a schematic diagram of the frequency control reserve (FCR) and spinning reserve (SR) provided by a gas turbine under a three-state model provided in one embodiment of the present application;

[0090] Figure 4 is a schematic diagram of the frequency control reserve (FCR) and spinning reserve (SR) provided by the electrolyzer under the three-state model provided in one embodiment of the present application;

[0091] Figure 5 is a schematic diagram of the amount of spinning reserve (SR) provided by a coal-fired unit under a two-state model provided in one embodiment of the present application;

[0092] Figure 6 is a schematic diagram of the frequency control reserve (FCR) and spinning reserve (SR) provided by a gas turbine under a two-state model provided in one embodiment of the present application;

[0093] Figure 7 is a schematic diagram of the frequency control reserve (FCR) and spinning reserve (SR) provided by the electrolyzer under the two-state model provided in one embodiment of the present application;

[0094] Figure 8 This is a comparison chart of the default amounts of the optimal scheduling results of the electric-hydrogen-gas hybrid integrated energy system solved based on the successive feasible point-convex hull relaxation method provided by an embodiment of the present application and the default amounts of the energy-frequency reserve coordinated scheduling results of the electric-hydrogen-gas hybrid integrated energy system solved based on the general boundary successive tightening method. DETAILED DESCRIPTION

[0095] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obscuring the description of the present application with unnecessary detail.

[0096] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0097] It will also be understood that the term "and / or" used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0098] As used in this specification and the appended claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0099] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0100] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0101] The energy and frequency reserve coordinated scheduling method for the electric-hydrogen system based on successive feasible convex relaxation provided in this application is described in detail below with reference to the accompanying drawings.

[0102] Figure 1 A flow chart of a method for coordinated scheduling of energy and frequency reserves in an electric-hydrogen system based on successive feasible convex relaxation provided in an embodiment of the present application is shown.

[0103] like Figure 1 As shown, the energy-frequency reserve coordinated scheduling method of the electric-hydrogen system based on successive feasible convex relaxation includes the following steps:

[0104] Step 101: Obtain network coefficients and operating coefficients of the power grid and gas grid models. The network coefficients include the power grid topology, gas grid topology, line resistance and impedance, natural gas, and hydrogen calorific value. The operating coefficients include the power generation coefficient of the generator set, the wind power and photovoltaic inverter coefficients, gas source parameters, electrolyzer device parameters, and booster station parameters.

[0105] Step 102: Acquire dynamic operation scenario data at different time sections, where the dynamic operation scenario data includes grid load demand, gas grid load demand, wind power and photovoltaic output, frequency control reserve demand, and spinning reserve demand scenario data;

[0106] Step 103: In combination with the network coefficient, the operating coefficient, and the dynamic operating scenario data, the total cost of the electricity-hydrogen-gas hybrid integrated energy system is used as the objective function. An electric power system operation model that considers the combination of units and electrolyzers, an operation model that provides frequency control reserves and spinning reserve ancillary services, and a dynamic natural gas system operation model that takes into account pipeline hydrogen blending are sequentially established. The objective function is combined with the three established models to construct a non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system that considers frequency control reserves, spinning reserves, and unit combinations.

[0107] Furthermore, in the embodiment of the present application, the objective function in the above step 103 is specifically as follows:

[0108] (A-1)

[0109] Among them, the subscript Indicates a generator set, including coal-fired units and gas-fired units; Indicates a time section; subscript Indicates electrolytic cell; subscript Indicates power load; subscript Indicates natural gas source; subscript Indicates gas load; Represents a collection of coal-fired units; Represents a collection of gas generator sets; It represents the unit startup cost of the generator set; represents the unit shutdown cost of the generator set; It represents the unit reserve cost of the spinning reserve of the generator set; It represents the unit reserve cost of the spinning reserve of the generator set; represents the unit power generation cost of coal-fired units; Indicates the unit non-fuel operation and maintenance cost of the gas unit; It represents the unit cost of gas-fired units for frequency control reserve; represents the unit cost of gas-fired units in standby mode under frequency control reserve; represents the unit startup cost of the electrolyzer; It represents the unit load shedding cost; Indicates the unit gas supply cost of the gas source; represents the unit gas load cost; Indicates the starting action of the generator set; Indicates the shutdown action of the generator set; Indicates the spinning reserve capacity provided by the generator set; Indicates the reserve capacity under spinning reserve provided by the generator set; Indicates the active power generated by the generator set; Indicates the frequency control reserve upper spare capacity provided by the gas unit; Indicates the spare capacity under frequency control reserve provided by gas units; Indicates the start-up action of the electrolytic cell; Indicates the required active power of the power load; Indicates the active power actually supplied to the power load; Indicates the gas supply volume of the natural gas source; Indicates the required mass flow rate of natural gas load; Indicates the mass flow rate actually supplied to the natural gas load;

[0110] The first term of the objective function in formula (A-1) is the startup and shutdown cost and spinning reserve cost of the generator set, which includes coal-fired units and gas-fired units. The second term is the power generation cost of the coal-fired unit. The third term is the cost of power generation and frequency control reserve provision for the gas-fired unit. The cost of power generation and frequency control reserve provision includes upper reserve cost and lower reserve cost. The fourth term is the startup cost of the electrolyzer. The fifth term is the cost of shedding electric load. The sixth term is the gas supply cost of the natural gas source. The seventh term is the cost of shedding gas load.

[0111] The power system operation model considering the combination of units and electrolyzers in step 3 above is as follows:

[0112] (A-2)

[0113] (A-3)

[0114] (A-4)

[0115] (A-5)

[0116] (A-6)

[0117] (A-7)

[0118] (A-8)

[0119] (A-9)

[0120] (A-10)

[0121] (A-11)

[0122] (A-12)

[0123] (A-13)

[0124] (A-14)

[0125] (A-15)

[0126] (A-16)

[0127] (A-17)

[0128] (A-18)

[0129] (A-19)

[0130] (A-20)

[0131] (A-21)

[0132] (A-22)

[0133] (A-23)

[0134] Among them, the subscript and Indicates power node; subscript Represented by power nodes To power node Line; subscript Indicates new energy units; subscript represents the reference bus; Representation and Node the collection of connected generator sets; Representation and Node A collection of connected new energy units; Representation and Node The set of connected nodes; Representation and Node the collection of connected electrical loads; Representation and Node a collection of connected electrolytic cells; Represents new energy units In the period Active power connected to the grid; For slave nodes To Node Active power of the line; For slave nodes To Node The square of the current in the circuit; For slave nodes To Node The resistance of the circuit; Indicates the hydrogen production power of the electrolyzer; Indicates the reactive power generated by the generator set; Represents new energy units In the period The online reactive power; For slave nodes To Node Reactive power of the line; For slave nodes To Node reactance of the inter-line; is the reactive power actually supplied to the power load; For nodes The square of the voltage amplitude; and For nodes and nodes The voltage phase angle; and Node The minimum and maximum squared voltage amplitudes; For slave nodes To Node the capacity of the inter-line; The reactive power required by the power load; Predict the active power of new energy units on the previous day; Predict reactive power for new energy units on the day before; is the voltage phase angle of the reference bus; is an integer variable, indicating the operating status of the generator set in period t, 1 represents the operating status, and 0 represents the non-operating status; and Respectively for units The minimum and maximum active power generation; and Respectively for units Minimum and maximum generated reactive power; Indicates the unit Maximum climbing power; Indicates the unit Minimum continuous running time after startup; and are the minimum and maximum power consumption of the electrolyzer during operation; The power consumed when the electrolyzer is in hot standby mode; is an integer variable, indicating the operating state of the electrolytic cell in time period t, 1 represents the operating state, and 0 represents the non-operating state; is an integer variable, indicating the hot standby state of the electrolytic cell in time period t, 1 means it is in hot standby state, and 0 means it is not in hot standby state; is the mass flow rate of hydrogen produced by the electrolyzer; is the higher calorific value of hydrogen, which is taken as 142MJ / kg; is the hydrogen production conversion efficiency of the electrolyzer; is an integer variable, indicating the closed state of the electrolytic cell in time period t, 1 for closed state and 0 for open state;

[0135] Formula (A-2) is the node active power balance equation; Formula (A-3) is the node reactive power balance equation; Formula (A-4) is the relationship between node voltage and line power; Formula (A-5) is the relationship between voltage phase angle and line power; Formula (A-6) is the second-order cone relaxation form of branch power flow; Formula (A-7) is the upper and lower limit constraints of node voltage; Formula (A-8) is the line transmission capacity constraint; Formula (A-9) is the active load demand constraint; Formula (A-10) is the upper and lower limit constraints of reactive load; Formula (A-11) is the grid-connected renewable energy active power constraint; Formula (A-12) is the grid-connected renewable energy reactive power constraint; Formula (A-13) stipulates that the phase angle of the reference bus is 0; Formula (A-14) is the generator in operation The upper and lower limits of active power output are set when the generator is in the running state; Formula (A-15) is the upper and lower limits of reactive power output when the generator is in the running state; Formula (A-16) is the active power ramp constraint of the generator; Formula (A-17) is the start-stop action and state constraint of the generator; Formula (A-18) is the shortest running time constraint of the generator; Formula (A-19) is the upper and lower limits of power when the electrolyzer is in the running state or hot standby state; Formula (A-20) is the efficiency constraint of the electrolyzer when producing hydrogen by electrolysis; Formula (A-21) is the state constraint of the electrolyzer, which can only be in the running state, hot standby state or shut down state at the same time; Formula (A-22) is the startup state constraint of the electrolyzer; Formula (A-23) restricts the electrolyzer from directly switching from the shut down state to the hot standby state;

[0136] The operational model for providing frequency control reserve and spinning reserve ancillary services in step 3 above is as follows:

[0137] (A-24)

[0138] (A-25)

[0139] (A-26)

[0140] (A-27)

[0141] (A-28)

[0142] in, Spinning reserve upper spare capacity provided for electrolysers; Spare capacity for required spinning reserve; Spinning reserve lower reserve capacity provided for electrolysers; The required spinning reserve capacity; Frequency control reserve capacity provided for electrolysers; Reserve capacity for required frequency control; Frequency control reserve capacity provided for electrolysers; Reserve capacity for required frequency control;

[0143] Formula (A-24) indicates that the spinning reserve is jointly provided by the coal-fired units, gas-fired units, and electrolyzers; Formula (A-25) indicates that the frequency control reserve is jointly provided by the gas-fired units and electrolyzers; Formula (A-26) indicates the upper and lower limit constraints and ramping constraints for the spinning reserve provided by the coal-fired units; Formula (A-27) indicates the upper and lower limit constraints and ramping constraints for the spinning reserve and frequency control reserve provided by the gas-fired units; Formula (A-28) indicates the capacity limit for the electrolyzer to provide spinning reserve and frequency control reserve in the operating and hot standby states;

[0144] The dynamic natural gas system operation model taking into account pipeline hydrogen blending in step 3 above is as follows:

[0145] (A-29)

[0146] (A-30)

[0147] (A-31)

[0148] (A-32)

[0149] (A-33)

[0150] (A-34)

[0151] (A-35)

[0152] (A-36)

[0153] (A-37)

[0154] (A-38)

[0155] (A-39)

[0156] (A-40)

[0157] (A-41)

[0158] (A-42)

[0159] (A-43)

[0160] (A-44)

[0161] (A-45)

[0162] (A-46)

[0163] (A-47)

[0164] (A-48)

[0165] (A-49)

[0166] Among them, the subscript and Represents a natural gas node; subscript Represents a natural gas node and gas nodes Pipes between; collections For gas nodes A collection of connected nodes; a collection For gas nodes A collection of connected natural gas sources; a collection For gas nodes A collection of connected electrolytic cells; a collection For gas nodes A collection of connected booster stations; a collection For gas nodes A collection of connected gas units; a collection For gas nodes connected load collection; is the density of the natural gas-hydrogen mixture in the natural gas pipeline; is the time section length; and are the gas mass flow rates at the beginning and end of the natural gas pipeline respectively; is the cross-sectional area of ​​the natural gas pipeline; is the length of the natural gas pipeline; and is the pressure at the natural gas node; is the mass flow rate of gas in the natural gas pipeline; is the friction factor of turbulent flow in natural gas pipelines; is the diameter of the natural gas pipeline; is the mass fraction of hydrogen in the natural gas pipeline; and are the mass fractions of hydrogen at the beginning and end of the natural gas pipeline, respectively; is the pressure of the pipeline; is the specific gas constant of the natural gas-hydrogen mixture in the pipeline; is the compressibility coefficient of the pipeline; is the ambient temperature; is the specific gas constant of hydrogen; is the specific gas constant of natural gas; is the mass flow rate of gas in the boosting station; is the mass flow rate of natural gas consumed by the gas generating unit; is the required mass flow rate of natural gas-hydrogen mixture; is the higher calorific value of natural gas, which is taken as 53.37MJ / kg; is the hydrogen mass fraction at the natural gas node; is the mass fraction of hydrogen in the compression station; is the power generation efficiency of the gas-fired unit; The maximum mass fraction of hydrogen injected into the natural gas pipeline; The maximum mole fraction of hydrogen injected into a natural gas pipeline; and are the densities of hydrogen and natural gas under standard conditions respectively; and is the minimum and maximum value of pipeline pressure; and The minimum and maximum values ​​of the gas mass flow rate of the natural gas source; The maximum value of the gas supply ramp rate of the natural gas source; and are the minimum and maximum values ​​of gas density in natural gas pipelines, respectively; and are the minimum and maximum values ​​of the boosting coefficient of the boosting station respectively; and are the minimum and maximum values ​​of the gas mass flow rate in the compression station, respectively;

[0167] Equation (A-29) represents the conservation of mass of the natural gas-hydrogen mixture in the pipeline; Equation (A-30) represents the conservation of momentum of the natural gas-hydrogen mixture in the pipeline; Equation (A-31) is the hydrogen advection transport equation, which represents the conservation of mass of hydrogen in the pipeline; Equation (A-32) is the state equation, which shows that the pressure and density of the natural gas-hydrogen mixture are related to the temperature; Equation (A-33) is the calculation rule for the specific gas constant of the natural gas-hydrogen mixture; Equation (A-34) is the formula for calculating the average pressure of the natural gas-hydrogen mixture in the pipeline; Equation (A-35) is the formula for calculating the average mass flow rate of the natural gas-hydrogen mixture in the pipeline; Equation (A-36) is the formula for calculating the average mass fraction of hydrogen in the pipeline; Equation (A-37) is the nodal mass flow balance equation for the natural gas-hydrogen mixture; Equation (A-38) represents the energy conversion relationship between the demand for the natural gas-hydrogen mixture and the demand for the original natural gas; Equation (A-39) Formula (A-40) represents the node mass flow balance equation for hydrogen; Formula (A-41) represents the relationship between the maximum hydrogen injection mole fraction and the maximum hydrogen injection mass fraction in the pipeline; Formula (A-42) is the limitation on the hydrogen injection mass fraction in the pipeline; Formula (A-43) is the pressure limitation of the natural gas node; Formula (A-44) is the gas supply limitation of the natural gas source; Formula (A-45) is the ramp constraint of the natural gas source; Formula (A-46) is the gas density limitation of the pipeline; Formula (A-47) is the boost ratio constraint of the boosting station; Formula (A-48) is the gas mass flow limitation of the boosting station; Formula (A-49) is the limitation on natural gas demand.

[0168] Step 104: For the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system established in step 103, perform convex relaxation on the bilinear terms in all non-convex constraints in the model using the McCormick envelope to obtain a convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system;

[0169] Furthermore, in the embodiment of the present application, the above step 104 includes:

[0170] The six nonlinear constraints (A-30), (A-31), (A-32), (A-38), (A-39), and (A-40) in the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system established in step 103 are transformed and the bilinear terms therein are relaxed using the McCarmick envelope, as follows:

[0171] Convert (A-30)-(A-32) to:

[0172] (A-50)

[0173] (A-51)

[0174] (A-52)

[0175] Convert (A-38)-(A-40) to:

[0176] (A-53)

[0177] (A-54)

[0178] (A-55)

[0179] in, , is the auxiliary variable introduced;

[0180] Combining equations (A-1)-(A-29), (A-33)-(A-37), (A-41)-(A-49), and (A-51)-(A-55), we obtain the convex model for the optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system.

[0181] It should be noted that the McCarmick envelope uses a set of linear constraints to replace the bilinear terms in the nonlinear constraints, convexifying the non-convex constraints and replacing them with bilinear terms. For example, its The McCarmick envelope represented by is as follows:

[0182] .

[0183] Step 105: Use the successive feasible point-convex hull relaxation method to alternately solve the convex model of optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system and the non-convex model of optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system to obtain the optimal scheduling method.

[0184] Furthermore, in the embodiment of the present application, the above step 105 includes:

[0185] Step 1051: Solve the optimal scheduling convex model of the electricity-hydrogen-gas hybrid integrated energy system using the GUROBI solver to obtain the target value lower limit and scheduling strategy. The scheduling strategy includes the output and start-stop status of the generator set and electrolyzer, the power grid flow, the wind power and photovoltaic power output, the natural gas source output, and the flow rate of the gas network pipeline;

[0186] Step 1052: Solve the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system using a fixed scheduling strategy to obtain the upper limit of the target value and the values ​​of all variables. The fixed scheduling strategy is to fix the values ​​of all variables included in the scheduling strategy in step 51 and solve the model using the DICOPT solver.

[0187] Step 1053, referring to the values ​​of the variables corresponding to the bilinear terms in the convex relaxation constraints obtained from the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system, narrowing the upper and lower limits of the variables in the bilinear terms in the convex relaxation constraints to solve the convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system and increase the lower limit of the target value;

[0188] Step 1054 , solving the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system according to the fixed scheduling strategy, and updating the upper limit of the target value;

[0189] Step 1055, repeat steps 1053-1054 until the difference between the upper limit of the target value and the lower limit of the target value is less than the preset value, and determine the target value and scheduling strategy obtained at this time as the optimal scheduling method.

[0190] The method for coordinated dispatch of energy, frequency and reserve of electric-hydrogen-gas system based on successive feasible convex relaxation provided in this application first obtains the network coefficient and operation coefficient of the power grid and gas grid models, then obtains the dynamic operation scenario data under different time sections, and then combines the network coefficient, operation coefficient and dynamic operation scenario data, takes the total cost of the electric-hydrogen-gas hybrid integrated energy system as the objective function, and successively establishes the power system operation model considering the combination of units and electrolyzers, the operation model providing frequency control reserve and rotating reserve auxiliary services, and the dynamic natural gas system operation model taking into account pipeline hydrogen blending, and compares the objective function with the three established models. Combined with the above, a non-convex model for the optimal scheduling of an electric-hydrogen-gas hybrid integrated energy system is constructed, taking into account frequency control reserve, spinning reserve, and unit combination. Then, for the established non-convex model for the optimal scheduling of an electric-hydrogen-gas hybrid integrated energy system, the bilinear terms in all non-convex constraints in the model are convexly relaxed using the McCormick envelope to obtain a convex model for the optimal scheduling of the electric-hydrogen-gas hybrid integrated energy system. Finally, the convex model for the optimal scheduling of the electric-hydrogen-gas hybrid integrated energy system and the non-convex model for the optimal scheduling of the electric-hydrogen-gas hybrid integrated energy system are alternately solved using the successive feasible point-convex hull relaxation method to obtain the optimal scheduling method. By introducing a three-state model of the electrolyzer and adopting the successive feasible point-convex hull relaxation method, the frequency control reserve and spinning reserve potential provided by the hot standby state of the electrolyzer are fully exploited, the scheduling accuracy is improved, the system operating cost is reduced, and the reserve pressure of traditional units is alleviated.

[0191] The progress of this application is illustrated by an example below. This example uses a 24-node power system and a 20-node natural gas system. In order to compare the superiority of the method proposed in this application, the traditional method for coordinated scheduling of energy and frequency reserves of an electric-hydrogen system based on a two-state model of an electrolyzer to provide backup, the method for coordinated scheduling of energy and frequency reserves of an electric-hydrogen system based on a general boundary successive tightening method (gradually tightening the upper and lower limits of the variables in the relaxed bilinear terms during the iteration process) and the method for coordinated scheduling of energy and frequency reserves of an electric-hydrogen system based on successive feasible convex relaxation proposed in this application are used to compare the scheduling results and solution accuracy. This application solves the MIQCP and MINLP problems of the basic solution through the GAMS optimization platform with GUROBI and DICOPT solvers.

[0192] Based on this example, the cost comparison results of the traditional method for coordinating the energy and frequency reserve of the electric-hydrogen system based on the two-state model of the electrolyzer to provide backup and the method for coordinating the energy and frequency reserve of the electric-hydrogen system based on the successive feasible point-convex hull relaxation proposed in this application (the electrolyzer model is a three-state model) are shown in Table 1. The comparison results with the provided frequency control reserve and spinning reserve are shown in Figure 2 — Figure 7 ,in, Figure 2 Schematic diagram of the spinning reserve (SR) amount provided by coal-fired units under the three-state model. Figure 3 Schematic diagram of the frequency control reserve (FCR) and spinning reserve (SR) provided by the gas turbine unit under the three-state model. Figure 4 Schematic diagram of the frequency control reserve (FCR) and spinning reserve (SR) provided by the electrolyzer under the three-state model. Figure 5 Schematic diagram of the amount of spinning reserve (SR) provided by coal-fired units under the two-state model. Figure 6 Schematic diagram of the frequency control reserve (FCR) and spinning reserve (SR) provided by the gas turbine unit under the two-state model. Figure 7 A schematic diagram showing the frequency control reserve (FCR) and spinning reserve (SR) provided by the electrolyzer under the two-state model, and a comparison between the energy-frequency reserve coordinated scheduling method for the power-hydrogen system based on the general boundary successive tightening method and the energy-frequency reserve coordinated scheduling method for the power-hydrogen system based on successive feasible point-convex hull relaxation proposed in this application (the results are shown in Figure 8). It shows that the scheduling cost of the electrolyzer model using the three-state model in the energy-frequency reserve coordinated scheduling method of the electric-hydrogen-gas system based on the successive feasible convex relaxation is reduced by 0.82% compared with the scheduling cost when the electrolyzer model uses the traditional two-state model. Compared with the coordinated scheduling of energy-frequency reserve of the electric-hydrogen-gas integrated energy system based on the traditional two-state model of the electrolyzer model, the coordinated scheduling of energy-frequency reserve of the electrolyzer model using the three-state model for the electric-hydrogen-gas hybrid integrated energy system can make full use of the additional frequency control reserve and rotating reserve that can be provided in the hot standby state of the electrolyzer, reduce the pressure of the frequency control reserve and rotating reserve required by the gas-fired units in the power system, and the rotating reserve required by the coal-fired units, reduce the additional cost of the power system caused by the frequent start and stop of the electrolyzer and the cost of natural gas as the fuel of the unit, so as to reduce the cost of the natural gas system. Compared with the general boundary successive tightening method, the use of the successive feasible point-convex hull relaxation method developed in this application can reduce the violation amount of constraints in the iterative solution process, so that the final converged result is more accurate and closer to the true value of the solution.

[0193] Table 1 Comparison of scheduling costs under two electrolyzer models

[0194]

[0195] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0196] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A method for coordinated scheduling of energy and frequency reserves in an electricity-hydrogen system based on successive feasible convex relaxation, characterized in that: The following steps are involved: Step 1: Obtain network coefficients and operating coefficients of the power grid and gas grid models. The network coefficients include power grid topology, gas grid topology, line resistance and impedance, natural gas, and hydrogen calorific value. The operating coefficients include generator set power generation coefficients, wind power and photovoltaic inverter coefficients, gas source parameters, electrolyzer device parameters, and booster station parameters. Step 2: Acquire dynamic operation scenario data at different time sections, wherein the dynamic operation scenario data includes grid load demand, gas grid load demand, wind power and photovoltaic output, frequency control reserve demand, and spinning reserve demand scenario data; Step 3: Combining the network coefficient, the operating coefficient, and the dynamic operating scenario data, and taking the total cost of the electricity-hydrogen-gas hybrid integrated energy system as the objective function, sequentially establish an electric power system operation model that considers the combination of units and electrolyzers, an operation model that provides frequency control reserves and spinning reserve ancillary services, and a dynamic natural gas system operation model that takes into account pipeline hydrogen blending. The objective function is combined with the three established models to construct a non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system that considers frequency control reserves, spinning reserves, and unit combinations. Step 4: For the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system established in step 3, perform convex relaxation on all bilinear terms in the non-convex constraints of the model using the McCormick envelope to obtain a convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system; Step 5: Use the successive feasible point-convex hull relaxation method to alternately solve the convex model of the optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system and the non-convex model of the optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system to obtain the optimal scheduling method; the specific details of step 5 are as follows: Step 51: Solve the optimal scheduling convex model of the electricity-hydrogen-gas hybrid integrated energy system using the GUROBI solver to obtain the target value lower limit and the scheduling strategy. The scheduling strategy includes the output and start-stop status of the generator set and electrolyzer, the power grid flow, the wind power and photovoltaic power output, the natural gas source output, and the flow rate of the gas network pipeline; Step 52: Solve the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system using a fixed scheduling strategy to obtain the upper limit of the target value and the values ​​of all variables. The fixed scheduling strategy is to fix the values ​​of all variables included in the scheduling strategy in step 51 and solve the model using the DICOPT solver. Step 53, referring to the values ​​of the variables corresponding to the bilinear terms in the convex relaxation constraints obtained from the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system, narrowing the upper and lower limits of the variables in the bilinear terms in the convex relaxation constraints to solve the convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system and increase the lower limit of the target value; Step 54: solving the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system according to the fixed scheduling strategy, and updating the upper limit of the target value; Step 55, repeat steps 53 and 54 until the difference between the upper limit of the target value and the lower limit of the target value is less than the preset value, and determine the target value and scheduling strategy obtained at this time as the optimal scheduling method.

2. The method for coordinated scheduling of energy and frequency reserve in an electricity-hydrogen system based on successive feasible convex relaxation according to claim 1 is characterized in that: The objective function in step 3 is as follows: Wherein, subscript v represents the generator set, including coal-fired units and gas-fired units; subscript t represents the time section; subscript h represents the electrolyzer; subscript d represents the power load; subscript w represents the natural gas source; subscript e represents the gas load; Ω C represents the coal-fired units; Ω G Represents a collection of gas generator sets; It represents the unit startup cost of the generator set; represents the unit shutdown cost of the generator set; It represents the unit reserve cost of the spinning reserve of the generator set; It represents the unit reserve cost of the spinning reserve of the generator set; represents the unit power generation cost of coal-fired units; Indicates the unit non-fuel operation and maintenance cost of the gas unit; It represents the unit cost of gas-fired units for frequency control reserve; represents the unit cost of gas-fired units in standby mode under frequency control reserve; represents the unit startup cost of the electrolyzer; It represents the unit load shedding cost; Indicates the unit gas supply cost of the gas source; represents the unit gas load cost; Indicates the starting action of the generator set; Indicates the shutdown action of the generator set; Indicates the spinning reserve capacity provided by the generator set; Indicates the reserve capacity under spinning reserve provided by the generator set; Indicates the active power generated by the generator set; Indicates the frequency control reserve upper spare capacity provided by the gas unit; Indicates the spare capacity under frequency control reserve provided by gas units; Indicates the start-up action of the electrolytic cell; Indicates the required active power of the power load; Indicates the active power actually supplied to the power load; Indicates the gas supply volume of the natural gas source; Indicates the required mass flow rate of natural gas load; Indicates the mass flow rate actually supplied to the natural gas load; The first term of the objective function in formula (A-1) is the start-up and shutdown cost and spinning reserve cost of the generator set, which includes coal-fired units and gas-fired units. The second term is the power generation cost of the coal-fired unit. The third term is the cost of power generation and frequency control reserve provision for the gas-fired unit. The cost of power generation and frequency control reserve provision includes upper reserve cost and lower reserve cost. The fourth term is the startup cost of the electrolyzer. The fifth term is the cost of power load shedding. The sixth term is the gas supply cost of the natural gas source. The seventh term is the cost of gas load shedding. The power system operation model considering the combination of units and electrolyzers in step 3 is specifically as follows: Wherein, subscripts i and j represent power nodes; subscript ij represents the line from power node i to power node j; subscript r represents the new energy unit; subscript REF represents the reference bus; U v (i) represents the set of generator sets connected to node i; U r (i) represents the set of new energy units connected to node i; U(i) represents the set of nodes connected to node i; U d (i) represents the set of power loads connected to node i; U h (i) represents the set of electrolytic cells connected to node i; P represents the grid-connected active power of the new energy unit r in period t; ij，t is the active power of the line from node i to node j; l ij，t is the square of the current in the line from node i to node j; r ij is the resistance of the line from node i to node j; Indicates the hydrogen production power of the electrolyzer; Indicates the reactive power generated by the generator set; represents the online reactive power of the new energy unit r in time period t; Q ij，t is the reactive power of the line from node i to node j; x ij is the reactance of the line from node i to node j; is the reactive power actually supplied to the power load; V i，t is the square of the voltage amplitude at node i; θ i，t and θ j，t is the voltage phase angle between node i and node j; V i min and V i max are the minimum and maximum squared voltage amplitudes of node i, respectively; is the capacity of the line from node i to node j; The reactive power required by the power load; Predict the active power of new energy units on the previous day; is the reactive power predicted by the new energy unit on the day before; θ REF，t is the voltage phase angle of the reference bus; is an integer variable, indicating the operating status of the generator set in period t, 1 represents the operating status, and 0 represents the non-operating status; and are the minimum and maximum active power generation of unit v respectively; and are the minimum and maximum generated reactive power of unit v respectively; Indicates the maximum climbing power of unit v; Indicates the minimum continuous running time of unit v after startup; and are the minimum and maximum power consumption of the electrolyzer during operation; The power consumed when the electrolyzer is in hot standby mode; is an integer variable, indicating the operating state of the electrolytic cell in time period t, 1 represents the operating state, and 0 represents the non-operating state; is an integer variable, indicating the hot standby state of the electrolytic cell in time period t, 1 means it is in hot standby state, and 0 means it is not in hot standby state; is the mass flow rate of hydrogen produced by the electrolyzer; is the higher calorific value of hydrogen, which is 142MJ / kg; η h is the hydrogen production conversion efficiency of the electrolyzer; is an integer variable, indicating the closed state of the electrolytic cell in time period t, 1 for closed state and 0 for open state; Formula (A-2) is the node active power balance equation; Formula (A-3) is the node reactive power balance equation; Formula (A-4) is the relationship between node voltage and line power; Formula (A-5) is the relationship between voltage phase angle and line power; Formula (A-6) is the second-order cone relaxation form of branch power flow; Formula (A-7) is the upper and lower limit constraints of node voltage; Formula (A-8) is the line transmission capacity constraint; Formula (A-9) is the active load demand constraint; Formula (A-10) is the upper and lower limit constraints of reactive load; Formula (A-11) is the grid-connected renewable energy active power constraint; Formula (A-12) is the grid-connected renewable energy reactive power constraint; Formula (A-13) stipulates that the phase angle of the reference bus is 0; Formula (A-14) is the generator in operation The upper and lower limits of active power output are set when the generator is in the running state; Formula (A-15) is the upper and lower limits of reactive power output when the generator is in the running state; Formula (A-16) is the active power ramp constraint of the generator; Formula (A-17) is the start-stop action and state constraint of the generator; Formula (A-18) is the shortest running time constraint of the generator; Formula (A-19) is the upper and lower limits of power when the electrolyzer is in the running state or hot standby state; Formula (A-20) is the efficiency constraint of the electrolyzer when producing hydrogen by electrolysis; Formula (A-21) is the state constraint of the electrolyzer, which can only be in the running state, hot standby state or shut down state at the same time; Formula (A-22) is the startup state constraint of the electrolyzer; Formula (A-23) restricts the electrolyzer from directly switching from the shut down state to the hot standby state; The operation model for providing frequency control reserve and spinning reserve ancillary services in step 3 is as follows: in, Spinning reserve capacity provided for electrolyzers; P t SR，U Spare capacity for required spinning reserve; The spinning reserve capacity provided for the electrolyzer; P t SR，D The required spinning reserve capacity; Frequency control reserve capacity provided for electrolyzers; P t FCR，U Reserve capacity for required frequency control; The frequency control reserve capacity provided for the electrolyzer; P t FCR，U Reserve capacity for required frequency control; Formula (A-24) indicates that the spinning reserve is jointly provided by the coal-fired units, gas-fired units, and electrolyzers; Formula (A-25) indicates that the frequency control reserve is jointly provided by the gas-fired units and electrolyzers; Formula (A-26) indicates the upper and lower limit constraints and ramping constraints for the spinning reserve provided by the coal-fired units; Formula (A-27) indicates the upper and lower limit constraints and ramping constraints for the spinning reserve and frequency control reserve provided by the gas-fired units; Formula (A-28) indicates the capacity limit for the electrolyzer to provide spinning reserve and frequency control reserve in the operating and hot standby states; The dynamic natural gas system operation model taking into account pipeline hydrogen blending in step 3 is specifically as follows: Where, subscripts m and n represent gas nodes; subscript mn represents the pipeline between gas node m and gas node n; set G(m) is the set of nodes connected to gas node m; set G w (m) is the set of natural gas sources connected to natural gas node m; the set G h (m) is the set of electrolyzers connected to the natural gas node m; the set G k (m) is the set of compression stations connected to the natural gas node m; the set G g (m) is the set of gas generators connected to the natural gas node m; the set G e (m) is the load set connected to the natural gas node m; ρ mn，t is the density of the natural gas-hydrogen mixture in the natural gas pipeline; Δt is the time section length; and are the gas mass flow rates at the beginning and end of the natural gas pipeline respectively; A mn is the cross-sectional area of ​​the natural gas pipeline; Δx mn is the length of the natural gas pipeline; π m，t and π n，t is the pressure at the natural gas node; F mn，t is the mass flow rate of gas in the natural gas pipeline; f mn is the friction factor of turbulent flow in natural gas pipelines; D mn is the diameter of the natural gas pipeline; c mn，t is the mass fraction of hydrogen in the natural gas pipeline; and are the mass fractions of hydrogen at the beginning and end of the natural gas pipeline respectively; π mn，t is the pressure of the pipeline; r mn，t is the specific gas constant of the natural gas-hydrogen mixture in the pipeline; Z mn is the compression coefficient of the pipeline; T is the ambient temperature; is the specific gas constant of hydrogen; R NG is the specific gas constant of natural gas; is the mass flow rate of gas in the boosting station; is the mass flow rate of natural gas consumed by the gas generating unit; is the required mass flow rate of natural gas-hydrogen mixture; HHV NG is the higher calorific value of natural gas, which is 53.37MJ / kg; c m,t is the hydrogen mass fraction at the natural gas node; is the mass fraction of hydrogen in the compression station; η v is the power generation efficiency of the gas turbine unit; c max The maximum mass fraction of hydrogen injected into the natural gas pipeline; α max The maximum mole fraction of hydrogen injected into a natural gas pipeline; and ρ NG are the densities of hydrogen and natural gas under standard conditions respectively; and is the minimum and maximum value of pipeline pressure; and The minimum and maximum values ​​of the gas mass flow rate of the natural gas source; The maximum value of the gas supply ramp rate of the natural gas source; and are the minimum and maximum values ​​of gas density in natural gas pipelines, respectively; and are the minimum and maximum values ​​of the boosting coefficient of the boosting station respectively; and are the minimum and maximum values ​​of the gas mass flow rate in the compression station, respectively; Formula (A-29) represents the conservation of mass of the natural gas-hydrogen mixture in the pipeline; Formula (A-30) represents the conservation of momentum of the natural gas-hydrogen mixture in the pipeline; Formula (A-31) is the horizontal transport equation of hydrogen, which represents the conservation of mass of hydrogen in the pipeline; Formula (A-32) is the state equation, which indicates that the pressure and density of the natural gas-hydrogen mixture are related to the temperature; Formula (A-33) is the calculation rule for the specific gas constant of the natural gas-hydrogen mixture; Formula (A-34) is the formula for calculating the average pressure of the natural gas-hydrogen mixture in the pipeline; Formula (A-35) is the formula for calculating the average mass flow rate of the natural gas-hydrogen mixture in the pipeline; Formula (A-36) is the formula for calculating the average mass fraction of hydrogen in the pipeline; Formula (A-37) is the nodal mass flow balance of the natural gas-hydrogen mixture Equation; Equation (A-38) represents the energy conversion relationship between the demand for natural gas-hydrogen mixture and the demand for original natural gas; Equation (A-39) represents the node mass flow balance equation for hydrogen; Equation (A-40) represents the power generation efficiency of the gas turbine unit; Equation (A-41) represents the relationship between the maximum mole fraction of hydrogen injected into the pipeline and the maximum mass fraction of hydrogen injected; Equation (A-42) is the limitation of the mass fraction of hydrogen injected into the pipeline; Equation (A-43) is the pressure limitation of the natural gas node; Equation (A-44) is the gas supply limitation of the natural gas source; Equation (A-45) is the ramp constraint of the natural gas source; Equation (A-46) is the gas density limitation of the pipeline; Equation (A-47) is the boost ratio constraint of the boosting station; Equation (A-48) is the gas mass flow limitation of the boosting station; Equation (A-49) is the limitation of natural gas demand.

3. The method for coordinated scheduling of energy and frequency reserve in an electricity-hydrogen system based on successive feasible convex relaxation according to claim 2 is characterized in that: In step 4, the bilinear terms in all non-convex constraints in the model are convexly relaxed using the McCormick envelope to obtain a convex model for the optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system, as follows: The six nonlinear constraints (A-30), (A-31), (A-32), (A-38), (A-39), and (A-40) in the non-convex model for optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system established in step 3 are transformed and the bilinear terms therein are relaxed using the McCarmick envelope, as follows: Convert (A-30)-(A-32) to: Convert (A-38)-(A-40) to: Among them, β mn，t , is the auxiliary variable introduced; Combining equations (A-1)-(A-29), (A-33)-(A-37), (A-41)-(A-49), and (A-51)-(A-55), we obtain the convex model for the optimal scheduling of the electricity-hydrogen-gas hybrid integrated energy system.

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