Optimal scheduling method for power systems including biomass indirect co-firing units

Abstract

This invention discloses an optimized scheduling method for a power system incorporating biomass indirect co-firing units, belonging to the field of power system optimization. The method includes: establishing a power system scheduling model with the objective function of minimizing the sum of power generation cost, coal-fired unit start-up cost, carbon trading cost, and curtailment penalty; and using the following optimization variables: the quality of thermal coal input to the boiler of each coal-fired unit at each time, the quality of biomass input to the pyrolysis furnace of each coal-fired unit at each time, the start-up status of each coal-fired unit, the net carbon dioxide emissions of each coal-fired unit at each time, and the renewable energy curtailment of each renewable energy unit at each time. The optimized scheduling plan is obtained by solving the power system scheduling model under preset constraints. These preset constraints include the operational constraints of the pyrolysis furnace, boiler, and turbine within the coal-fired units. This invention can simultaneously improve the renewable energy absorption capacity and reduce carbon emissions while satisfying the operational constraints of the pyrolysis furnace, boiler, and turbine within the coal-fired units.

Description

Technical Field

[0001] This invention belongs to the field of power system optimization, and more specifically, relates to an optimized scheduling method for power systems including biomass indirect coupling co-firing units. Background Technology

[0002] There are two main methods for co-firing biomass in coal-fired power units: direct co-firing and indirect co-firing. Currently, power system dispatch mainly considers direct co-firing, but this method causes problems such as corrosion, ash accumulation, and slagging in the original pulverized coal boiler, and has poor fuel compatibility, making it difficult to achieve high co-firing rates. Therefore, it is only suitable for application in the early stages of power system transformation. Indirect co-firing involves pre-treating biomass in gasifiers or pyrolysis furnaces, and only co-firing gasification or pyrolysis products in the pulverized coal boiler, effectively reducing the impact on the boiler and thus achieving higher co-firing rates. However, current research on indirect co-firing mainly focuses on thermodynamics, with only a few studies on self-dispatch optimization for gasification-co-firing units, lacking overall synergistic optimization from the perspective of the power system and other components such as renewable energy. In addition, gasification-co-firing cannot expand the operating range of the original coal-fired power unit's power output, resulting in insufficient operational flexibility. In contrast, pyrolysis-co-firing can adjust the output power and carbon emissions of the co-firing unit by controlling the co-firing rate and flexibly utilizing pyrolysis products, thus expanding the unit's dispatchable space. However, the lack of a scheduling model for indirect co-firing based on biomass pyrolysis and the insufficient overall collaborative optimization methods from the perspective of the power system have resulted in an unknown benefit of biomass pyrolysis co-firing for carbon emission reduction and renewable energy consumption.

[0003] Therefore, there is an urgent need for modeling and optimization methods for the power system dispatch layer, which should incorporate the output power and carbon emission flexible dispatch characteristics of pyrolysis-based indirect coupling co-firing units into a unified dispatch framework. Under the premise of meeting the operational constraints of coal-fired units and biomass pyrolysis systems, the capacity for new energy consumption should be improved in a coordinated manner. Through biomass substitution for coal-fired power generation and the flexible utilization of pyrolysis product biochar, carbon emission reduction from coal-fired power generation and system flexibility should be achieved, thereby supporting the transformation of carbon-neutral power systems characterized by a high proportion of new energy. Summary of the Invention

[0004] To address the shortcomings and improvement needs of existing technologies, this invention provides an optimized scheduling method for power systems that include biomass indirect coupling and co-firing units. The aim is to incorporate coal input, biomass pyrolysis, carbon emissions, and renewable energy into the same scheduling framework, and to perform overall coordinated optimization of coal-fired units, renewable energy units, and other components within the power system. Under the premise of meeting the operational constraints of pyrolysis furnaces, boilers, and steam turbines within coal-fired units, this method synergistically enhances the capacity for new energy absorption and reduces carbon emissions.

[0005] To achieve the above objectives, according to one aspect of the present invention, an optimized scheduling method for a power system comprising a biomass indirect coupling co-firing unit is provided, comprising: The objective function is to minimize the sum of power generation cost, coal-fired unit start-up cost, carbon trading cost, and curtailment penalty, with the mass of thermal coal input to the boiler for each coal-fired unit at each time step as the criterion. The mass of biomass input into the pyrolysis furnace of each coal-fired unit at each time point. Start-up status of each coal-fired unit Net carbon dioxide emissions of each coal-fired unit at each time point and the amount of renewable energy curtailed by each renewable energy unit at each time point. To optimize variables, a power system dispatch model is established; Under preset constraints, the power system dispatch model is solved to obtain the optimized dispatch plan. Among them, subscript Indicates the index of coal-fired power units, subscript Indicates the index of renewable energy units, subscript Indicates time; Indicates coal-fired power unit exist It can be started at any time; the power generation cost includes the cost of thermal coal and the cost of biomass; the preset constraints include: power balance constraints, system reserve constraints, line power flow constraints, renewable energy unit output constraints, and the operation constraints of pyrolysis furnaces, boilers and steam turbines in coal-fired units.

[0006] Furthermore, the net carbon dioxide emissions of each coal-fired unit at each time point. The calculation formula is: ; in, Indicates the emission factor of thermal coal; This indicates the reduction in carbon dioxide emissions due to biochar sequestration, and , This indicates the reduction in carbon dioxide emissions per unit mass of biochar stored. This indicates the mass of biochar produced by biomass pyrolysis. This indicates the quality of biochar used for power generation.

[0007] Furthermore, the operational constraints of the pyrolysis furnace include: The relationship between the production of pyrolysis gas, pyrolysis oil, and biochar and the input of biomass fuel satisfies: ; Among them, superscript This indicates the types of biomass pyrolysis products in the pyrolysis furnace. Indicates pyrolysis gas. Indicates pyrolysis oil. Indicates biochar; The first generation produced by biomass pyrolysis The yield of the product, This indicates the amount of biomass produced per unit mass of pyrolysis. Yield of the product; Energy consumption of pyrolysis furnace satisfy: ; in, For the start-up of the pyrolysis furnace, Coal-fired power units The pyrolysis furnace in Start at any time; The energy required for the pyrolysis of a unit mass of biomass. Energy consumption for starting up a biomass pyrolysis furnace; The biomass mass input to the pyrolysis furnace during operation satisfy: ; in, It is used to indicate coal-fired power units In the intermediate pyrolysis furnace The binary variable representing the running state at any given moment. Indicates coal-fired power unit The pyrolysis furnace in Always online Indicates coal-fired power unit The pyrolysis furnace in Always offline; and These represent the upper and lower limits of the rate at which the pyrolysis furnace processes biomass feedstock; The pyrolysis furnace operates under the following conditions: ; in, As an indicator variable for indirect co-firing modification of biomass, Indicates coal-fired power unit Biomass co-firing modification has been carried out. Indicates coal-fired power unit No biomass co-firing modification was carried out; The minimum start-up and shutdown time for the pyrolysis furnace operation must meet the following requirements: ; in, It is an indicator variable for pyrolysis furnace shutdown. Indicates coal-fired power unit The pyrolysis furnace in The machine is always shut down; and These represent the shortest time spans for the pyrolysis furnace to be in operation and shutdown states, respectively. The relationship between the operating states of the pyrolysis furnace satisfies: ; The number of start-ups and shutdowns of the pyrolysis furnace satisfies: ; in, Indicates the scheduling period; This is the upper limit for the number of times a pyrolysis furnace can be started during the scheduling period; The energy from the pyrolysis products fed into the boiler from the pyrolysis furnace is used to replace the energy from the pyrolysis products of thermal coal. satisfy: ; in, , and The values ​​are the lower heating values ​​of pyrolysis gas, pyrolysis oil, and biochar, respectively.

[0008] Furthermore, the operating constraints of the boiler include: Total heat energy input to boiler satisfy: ; ; in, It has the lower calorific value of thermal coal; To indicate coal-fired power units exist The binary variable representing the online status at any given time. This indicates that the boiler is running online. This indicates that the boiler is offline; and They represent coal-fired power units Minimum and maximum input power of medium-sized boilers; The boiler's minimum online operating time and minimum downtime meet the following requirements: ; in, To indicate coal-fired power units exist Binary variables that are constantly halting. Indicates coal-fired power unit exist The machine is always shut down; and Coal-fired units Minimum continuous online operation and downtime; The boiler's ramp-up rate satisfies: ; in, and Coal-fired units The rate at which the boiler climbs uphill and downhill; and Coal-fired units The start-up and shutdown operating capacity of the medium-sized boiler; The operating state transition relationship of coal-fired power units satisfies: ; Biomass co-firing rate in boilers satisfy: ; ; in, This represents the upper limit of the biomass indirect coupling co-firing rate; The heat power input from the boiler to the steam turbine satisfies: ; ; in, for Coal-fired power units The boiler inputs thermal power to the steam turbine; For coal-fired power units exist Boiler efficiency during indirect coupling of combustion at all times; and Coal-fired units Maximum and minimum input thermal power of the steam turbine; Boiler efficiency satisfy: ; in, This indicates the boiler efficiency when no biomass is burned. It is the slope of the boiler efficiency as a function of the co-firing rate.

[0009] Furthermore, the operating constraints of the steam turbine include: The steam turbine output power meets the following requirements: ; ; ; ; in, For coal-fired power units exist The electrical power output at any given time; For use in coal-fired power units The number of nodes in the output curve segmented for coal-fired power units. The output curve was this Each node is divided into The first node corresponds to the minimum input thermal power of the steam turbine, and the last node corresponds to the maximum input thermal power of the steam turbine. As a continuous auxiliary variable, it represents the coal-fired power unit. exist Time of the first The weight of each node in the turbine power and generator power. It is a non-negative number; This is a binary auxiliary variable indicating whether the current turbine operating state is at the [number]th [position]. part.

[0010] Furthermore, the power balance constraint is: ; Among them, subscript Indicates the index of external power transmission lines, subscript Indicates the load node index; Indicates the number of coal-fired power units. Indicates the number of renewable energy units. Indicates the number of external power transmission lines. Indicates the number of load nodes; Indicates renewable energy units exist Power output at any time Indicates the current area and external power transmission lines exist The switching power at any given moment; Indicates load node exist The workload of the moment.

[0011] Furthermore, the system standby constraint is as follows: ; in, Indicates coal-fired power unit Maximum electrical power, Indicates coal-fired power unit Minimum electrical power; Indicates renewable energy units exist Capacity factor at time, Indicates renewable energy units Rated capacity; and These are the upper and lower reserve coefficients of the system, respectively.

[0012] Furthermore, for any external transmission line The power flow constraints of the line are: ; in, Indicates external power transmission line The power transmission limit of the current, Indicates coal-fired power unit External power transmission lines The power flow distribution transfer factor Indicates renewable energy units External power transmission lines The power flow distribution transfer factor Indicates external power transmission line The node and the external transmission line The power flow distribution transfer factor Indicates load node External power transmission lines The power flow distribution transfer factor.

[0013] Furthermore, the output constraints for renewable energy units are as follows: .

[0014] According to another aspect of the present invention, a computer-readable storage medium is provided, including a stored computer program; when the computer program is executed by a processor, it implements the optimized scheduling method for a power system including a biomass indirect coupling co-firing unit provided by the present invention.

[0015] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects: (1) This invention takes the minimum sum of power generation cost, coal-fired unit start-up cost, carbon trading cost and curtailment penalty as the objective function. Under the constraints of power balance, system reserve, line power flow, renewable energy output and operation of pyrolysis furnace, boiler and steam turbine in coal-fired unit, it optimizes the time-level scheduling plan of biomass pyrolysis, coal input, carbon emissions and renewable energy. It incorporates coal input, biomass pyrolysis, carbon emissions and renewable energy into the same scheduling framework. As a result, it can carry out overall coordinated optimization of coal-fired unit, renewable energy unit and other components in the power system. Under the premise of meeting the operation constraints of pyrolysis furnace, boiler and steam turbine in coal-fired unit, it can coordinately improve the new energy absorption capacity and reduce carbon emissions.

[0016] (2) In this invention, the net carbon dioxide emissions of each coal-fired unit at each time point are calculated. At the same time, the impact of thermal coal combustion and biochar storage on carbon dioxide emissions is fully considered. By flexibly arranging the power generation and storage of pyrolysis product biochar, the heat power input to the boiler can be flexibly adjusted, and the operating range of coal-fired units can be expanded.

[0017] (3) The pyrolysis furnace operation constraints established in this invention reflect the operation model of the pyrolysis furnace and the energy coupling relationship between the pyrolysis furnace and the boiler. By flexibly arranging the power generation and storage of biochar from pyrolysis products, the thermal power input to the boiler can be flexibly adjusted, expanding the operating range of the coal-fired unit. At the same time, by storing biochar, the carbon emissions of the unit can be offset, achieving lower carbon emissions.

[0018] (4) The boiler operation constraints established by this invention reflect the boiler operation model and the influence of biomass co-firing rate on the substitution effect of biomass pyrolysis products on power coal. Thus, by adjusting the biomass co-firing rate of coal-fired units, flexible substitution of power coal can be achieved, reducing the power generation emissions of coal-fired units.

[0019] (5) In this invention, the real-time carbon emissions and output power of the coal-fired unit are included in the objective function and power balance respectively, which effectively realizes the coordinated scheduling of coal-fired units and renewable energy units.

[0020] Overall, through the above-described technical solutions conceived in this invention, the minimum technical output of the co-firing unit is reduced, the flexibility of operation is increased, and the power system's ability to absorb renewable energy is enhanced. At the same time, through the synergistic effect of biomass pyrolysis products replacing thermal coal and biochar sequestration, the carbon emissions of the power system are effectively reduced, and the total operating cost of the system can be reduced. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the internal energy flow and carbon dioxide emissions of an existing biomass indirect co-firing unit.

[0022] Figure 2 The present invention provides a nonlinear efficiency curve and piecewise linear method for a steam turbine-power generation system in a coal-fired unit.

[0023] Figure 3 An optimized scheduling method for a power system including a biomass indirect coupling co-firing unit is provided in this embodiment of the invention.

[0024] Figure 4 This is a schematic diagram comparing the time-series power balance results in different scenarios provided in the embodiments of the present invention.

[0025] Figure 5 This is a schematic diagram comparing the timing of power curtailment in different scenarios provided in the embodiments of the present invention.

[0026] Figure 6This is a schematic diagram illustrating the utilization of biochar according to an embodiment of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0028] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0029] Biomass indirect co-firing units are units that have been modified from traditional coal-fired units. Their basic components are as follows: Figure 1 As shown, the system includes a biomass pyrolysis and separation system (i.e., a pyrolysis furnace), a boiler combustion system (i.e., a boiler), and a steam turbine-power generation system (i.e., a steam turbine). Their respective functions are: pyrolyzing biomass to produce multiple byproducts and separating and purifying them; co-firing power coal with pyrolysis products; and generating electricity using high-temperature, high-pressure steam. The energy flow and carbon dioxide emissions within the biomass indirect coupling co-firing unit are shown in the attached figure. Figure 1 As shown, the pyrolysis furnace receives heat from boiler flue gas and converts the input biomass raw materials into pyrolysis oil, pyrolysis gas, and biochar through an anaerobic pyrolysis reaction. The pyrolysis gas and pyrolysis oil are fed into the boiler to partially replace coal for power generation. Since biochar has a carbon fixation function, it can be flexibly selected to be fed into the power plant boiler as fuel or stored to reduce carbon emissions from coal-fired units.

[0030] Currently, research on indirect co-firing mainly focuses on thermodynamics, with only a few studies targeting self-scheduling optimization of gasification-co-firing units. There is a lack of overall synergistic optimization from the perspective of the power system and other components such as renewable energy. Furthermore, gasification-co-firing cannot expand the original power output operating domain of coal-fired units, resulting in insufficient operational flexibility. To address this issue, this invention provides an optimized scheduling method for power systems incorporating biomass indirect co-firing units. The overall concept is to fully consider the operating characteristics and energy coupling relationships between pyrolysis furnaces, boilers, and turbines in coal-fired units, integrating coal input, biomass pyrolysis, carbon emissions, and renewable energy into the same scheduling framework. This allows for overall synergistic optimization of coal-fired units, renewable energy units, and other components within the power system. Under the premise of meeting the operational constraints of pyrolysis furnaces, boilers, and turbines within coal-fired units, this collaboratively enhances the capacity for renewable energy absorption and reduces carbon emissions.

[0031] Based on the above concepts, this invention first analyzes the energy and material input / output flow of a biomass pyrolysis furnace, and constructs a refined operating model for the biomass pyrolysis furnace. Specifically: For a pyrolysis furnace, the relationship between the production of pyrolysis gas, pyrolysis oil, and biochar and the biomass fuel input is expressed by equation (1): (1) In the formula, superscript This indicates the types of biomass pyrolysis products in the pyrolysis furnace. Indicates pyrolysis gas. Indicates pyrolysis oil. Indicates biochar; for biomass pyrolysis The yield of the product; The mass of biomass used for pyrolysis, The production of biomass pyrolysis per unit mass Yield of the product.

[0032] Since biomass pyrolysis is an endothermic reaction, with the heat source being boiler flue gas, the energy consumption of the biomass pyrolysis furnace is calculated using equation (2): (2) In the formula, For the start-up of the pyrolysis furnace, Indicates coal-fired power unit The pyrolysis furnace in Start at any time; The energy required for the pyrolysis of a unit mass of biomass. This refers to the start-up energy consumption of a biomass pyrolysis furnace.

[0033] The mass of biomass fuel processed by the pyrolysis furnace during operation is limited by equation (3): (3) In the formula, It refers to coal-fired power units In the intermediate pyrolysis furnace Operating status during a given time period This indicates that the generator unit is online. This indicates that the generator set is offline; and These are the upper and lower limits of the rate at which the pyrolysis furnace processes biomass feedstock.

[0034] The pyrolysis furnace operation constraints only apply to biomass indirect coupling and co-firing units. Therefore, the operating state of the pyrolysis furnace satisfies equation (4): (14) In the formula, As an indicator variable for indirect co-firing modification of biomass, This indicates that the unit has undergone biomass co-firing modification.

[0035] The minimum start-up and shutdown time limit for the pyrolysis furnace is expressed by equation (5): (5) In the formula, It is an indicator variable for pyrolysis furnace shutdown. Indicates coal-fired power unit In the intermediate pyrolysis furnace Always shut down and These represent the shortest time spans for the pyrolysis furnace to be in operation and shutdown, respectively.

[0036] The relationship between the operating states of the pyrolysis furnace is constrained by equation (6): (6) In order to reduce metal fatigue and thermal stress damage to equipment such as pyrolysis furnaces caused by start-up and shutdown, Equation (7) also limits the number of start-ups and shutdowns of biomass pyrolysis furnaces during operation to avoid frequent start-ups and shutdowns during the scheduling cycle.

[0037] (7) In the formula, Indicates the scheduling period; This is a limit on the number of times the pyrolysis furnace can be started during the scheduling period.

[0038] The energy of the pyrolysis products transported from the biomass pyrolysis furnace to the coal-fired boiler to replace thermal coal is calculated by equation (8): (8) In the formula, Indicates coal-fired power unit exist The quality of biochar used for power generation at all times. , and The values ​​are the lower heating values ​​of pyrolysis gas, pyrolysis oil, and biochar, respectively.

[0039] The reduction in carbon dioxide emissions from biochar storage is calculated using equation (9): (9) In the formula, This indicates the amount of carbon dioxide emissions reduced by the amount of biochar stored per unit mass.

[0040] Secondly, this invention considers the impact of co-firing of biomass pyrolysis products on boiler operating efficiency and carbon emissions, and performs refined modeling of the boiler combustion system. Specifically: The total thermal energy input to the boiler combustion system includes two parts: the thermal energy of pyrolysis products and the thermal energy of power coal, as expressed by equation (10): (10) In the formula, and They are respectively Time-of-use coal-fired units Total thermal energy and mass of power coal input to the boiler; It is the lower heating value of thermal coal.

[0041] The upper and lower limits of boiler input power are constrained by equation (11): (11) In the formula, A binary variable indicating the online status of a coal-fired power unit. Indicates coal-fired power unit exist Always online and running. Indicates coal-fired power unit exist Always offline. and Coal-fired units Minimum and maximum input power of the boiler.

[0042] Boiler operation is also constrained by minimum online operation and downtime, as shown in equation (12): (12) In the formula, To indicate coal-fired power units exist Binary variables that are started at any time, Indicates coal-fired power unit exist Start at any time; To indicate coal-fired power units exist Binary variables that are constantly halting. Indicates coal-fired power unit exist The machine is always shut down; and The units Minimum continuous online operation and downtime.

[0043] The ramp-up rate of boiler operation is constrained by equation (13): (13) In the formula, and Coal-fired units The rate at which the boiler climbs uphill and downhill; and These refer to the boiler's operating capacity during startup and shutdown, respectively.

[0044] The state transition relationship of a coal-fired power unit must satisfy equation (14): (14) Biomass co-firing rate in boilers Calculated by equation (15), that is, the ratio of the heat generated by the combustion of pyrolysis products to the total combustion input into the boiler; the upper limit of the co-firing rate is limited by equation (16): (15) (16) In the formula, This represents the upper limit of the biomass indirect coupling co-firing rate.

[0045] The heat power input from the boiler to the turbine system is calculated by equation (17), which is the total usable heat energy generated by combustion minus the heat energy supplied for biomass pyrolysis: (17) In the formula, for Time-of-use coal-fired units Input the thermal power of the steam turbine; For coal-fired power units exist The efficiency of coal-fired boilers during indirect coupling of combustion.

[0046] Because the pyrolysis products differ significantly from thermal coal in terms of elemental composition and calorific value, co-firing them leads to a near-linear decrease in boiler operating efficiency as the co-firing rate increases. Therefore, coal-fired power units... exist Efficiency of coal-fired boilers when indirect coupling combustion Calculated by equation (18): (18) In the formula, It is the slope of boiler efficiency as a function of co-firing rate. This indicates the boiler efficiency when biomass is not co-fired.

[0047] The upper and lower limits of the turbine input power, i.e. the heat power input from the boiler to the turbine system, are constrained as shown in equation (19): (19) In the formula, and Coal-fired units The maximum and minimum input thermal power of the steam turbine.

[0048] The net emissions of coal-fired units are calculated using equation (20), including carbon dioxide produced by the combustion of thermal coal and carbon dioxide offset by biochar sequestration: (20) In the formula, For coal-fired power units exist Net carbon dioxide emissions during the period This refers to the emission factor for thermal coal.

[0049] Next, the steam turbine is modeled. The steam turbine system uses high-temperature, high-pressure steam generated by the boiler system to drive the blades to rotate, thus generating electricity by the rotor cutting the magnetic field. The nonlinear power generation efficiency curve is considered, such as... Figure 2 As shown, the output power is calculated and constrained by equations (21)-(24): (twenty one) (twenty two) (twenty three) (twenty four) in, For coal-fired power units exist The electrical power output at any given time; For use in coal-fired power units The number of nodes in the output curve segmented for coal-fired power units. The output curve was this Each node is divided into The first node corresponds to the minimum input thermal power of the steam turbine, and the last node corresponds to the maximum input thermal power of the steam turbine. As a continuous auxiliary variable, it represents the coal-fired power unit. exist Time of the first The weight of each node in the turbine power and generator power. It is a non-negative number; This is a binary auxiliary variable indicating whether the current turbine operating state is at the [number]th [position]. part.

[0050] Finally, the modeling results of the biomass pyrolysis furnace, pulverized coal boiler, and steam turbine system of this invention generate a power system dispatch model that considers internal energy flow coupling. The objective function is to minimize the sum of power generation cost, coal-fired unit start-up cost, carbon trading cost, and curtailment penalty. Under the premise of satisfying the constraints of power balance, system reserve, line power flow, renewable energy output, and the operation of pyrolysis furnace, boiler, and steam turbine in coal-fired units, the model optimizes the use of coal-fired fuel, biomass fuel, carbon emissions, renewable energy output, and curtailment in co-fired units. This achieves coordinated operation of coal-fired units, co-fired units, and renewable energy units, improves renewable energy absorption, and reduces carbon emissions from power system operation.

[0051] The following is an example: Example 1: An optimized scheduling method for a power system including biomass indirect coupling co-firing units, such as Figure 3 As shown, it includes: The objective function is to minimize the sum of power generation cost, coal-fired unit start-up cost, carbon trading cost, and curtailment penalty, with the mass of thermal coal input to the boiler for each coal-fired unit at each time step as the criterion. The mass of biomass input into the pyrolysis furnace of each coal-fired unit at each time point. Start-up status of each coal-fired unit Net carbon dioxide emissions of each coal-fired unit at each time point and the amount of renewable energy curtailed by each renewable energy unit at each time point. To optimize variables, a power system dispatch model is established; Under preset constraints, the power system dispatch model is solved to obtain the optimized dispatch plan. Among them, subscript Indicates the index of coal-fired power units, subscript Indicates the index of renewable energy units, subscript Indicates time; Indicates coal-fired power unit exist It can be started at any time; the power generation cost includes the cost of thermal coal and the cost of biomass; the preset constraints include: power balance constraints, system reserve constraints, line power flow constraints, renewable energy unit output constraints, and the operation constraints of pyrolysis furnaces, boilers and steam turbines in coal-fired units.

[0052] The objective function of the power system dispatch model established in this embodiment is: ; in, This represents the cost per unit mass of thermal coal. This represents the cost per unit mass of biomass fuel. The cost of starting up a coal-fired power unit once. This represents the unit mass carbon emission trading cost. This indicates the penalty for abandoning renewable energy by a unit. Indicates renewable energy units exist The amount of renewable energy power curtailed at any given time This indicates the number of renewable energy generating units. For coal-fired power units exist The start indicator variable at a given time. Indicates coal-fired power unit exist Start at any time.

[0053] In the objective function described above, the net carbon dioxide emissions of each coal-fired unit at each time point are... The calculation expression is shown in equation (20).

[0054] In this embodiment, the operating constraints of the pyrolysis furnace are shown in equations (1), (2), (3), (4), (5), (6), (7), and (8), the operating constraints of the boiler are shown in equations (10), (11), (12), (13), (14), (15), (16), (17), (18), and (19), and the operating constraints of the steam turbine are shown in equations (21), (22), (23), and (24).

[0055] In this embodiment, the power balance constraint is: ; Among them, subscript Indicates the index of external power transmission lines, subscript Indicates the load node index; Indicates the number of coal-fired power units. Indicates the number of renewable energy units. Indicates the number of external power transmission lines. Indicates the number of load nodes; Indicates renewable energy units exist Power output at any time Indicates the current area and external power transmission lines exist The switching power at any given moment; Indicates load node exist The workload of the moment.

[0056] In this embodiment, the remaining constraints are as follows: The system's standby constraints are: ; in, Indicates coal-fired power unit Maximum electrical power, Indicates coal-fired power unit Minimum electrical power; Indicates renewable energy units exist Capacity factor at time, Indicates renewable energy units Rated capacity; and These are the upper and lower reserve coefficients of the system, respectively.

[0057] For any external transmission line The power flow constraints of the line are: ; in, Indicates external power transmission line The power transmission limit of the current, Indicates coal-fired power unit External power transmission lines The power flow distribution transfer factor Indicates renewable energy units External power transmission lines The power flow distribution transfer factor Indicates external power transmission line The node and the external transmission line The power flow distribution transfer factor Indicates load node External power transmission lines The power flow distribution transfer factor.

[0058] The output constraints for renewable energy units are: .

[0059] In summary, this embodiment proposes a biomass indirect coupling co-firing unit operation modeling method for power system optimized scheduling. It constructs a refined model of biomass pyrolysis furnace operation, the energy coupling relationship between the pyrolysis furnace and pulverized coal boiler, and the flexible application of biomass pyrolysis products. This effectively reduces carbon emissions from the power system and enhances the power system's renewable energy absorption capacity. By adjusting the biomass co-firing rate of coal-fired units, flexible substitution of thermal coal can be achieved, reducing emissions from coal-fired power generation. By flexibly arranging the power generation and storage of pyrolysis product biochar, the thermal power input to the boiler can be flexibly adjusted, expanding the operating domain of coal-fired units. Simultaneously, by storing biochar, additional carbon emissions from the units can be offset, achieving even lower carbon emissions. Furthermore, a method is proposed for co-firing units to participate in power system scheduling by flexibly adjusting unit output and carbon emissions. A model is constructed in which the real-time carbon emissions and power generation of co-firing units are respectively included in the objective function and power balance, achieving coordinated scheduling with renewable energy. Through the above technical solutions conceived in this embodiment, the minimum technical output of the co-firing unit is reduced, the flexible operation capability is increased, and the power system's ability to absorb renewable energy is improved. At the same time, through the synergistic effect of biomass pyrolysis products replacing thermal coal and biochar sequestration, the carbon emissions of the power system are effectively reduced, and the total operating cost of the system can be reduced.

[0060] The following analysis, based on simulation results, further verifies the beneficial effects achievable in this embodiment.

[0061] Based on the IEEE-6-bus power system, a case study analysis is conducted to compare the operating costs, carbon emissions, and renewable energy consumption of the power system after the coal-fired units undergo biomass indirect coupling and co-firing retrofit.

[0062] The IEEE-6-bus system comprises three conventional thermal power units ( , , Both have a rated capacity of 169MW; two coal-fired units capable of indirect co-firing biomass ( , Both wind farms have a rated capacity of 247MW and can achieve a maximum biomass co-firing rate of 30%. and a photovoltaic power station All nodes are 4. The load of the system is equally shared by nodes 3 and 6. In this implementation example, it is assumed that the carbon tax price is 200 yuan / ton, the curtailment penalty is 300 yuan / MWh, the biomass price is 450 yuan / ton, and the thermal coal price is 750 yuan / ton.

[0063] Based on the above IEEE-6-bus power system, two simulation scenarios are set up using the controlled variable method. In scenario one, the unit... and Without co-firing biomass, it participates in power system optimization and dispatch; in scenario two, the unit and It can be used for biomass co-firing and participate in power system optimization and dispatch. (Except for generating units) and In addition, the load, wind and solar power output, and other constraints in the power system are the same in both scenario one and scenario two.

[0064] Based on simulation analysis, the main operating results of Scenario 1 and Scenario 2 are shown in Table 1, including details of operating costs, renewable energy consumption, and carbon dioxide emissions.

[0065] Table 1. Results of running Scenario 1 and Scenario 2

[0066] As shown in Table 1, compared to Scenario 1, Scenario 2, which allows for indirect co-firing of biomass, reduces daily operating costs by RMB 228,000. Specifically, fuel costs increased by RMB 88,000, mainly due to the lower calorific value of biomass and the reduced boiler efficiency caused by indirect co-firing based on pyrolysis, resulting in a higher total fuel requirement. Carbon tax costs decreased by RMB 266,000, primarily because biomass pyrolysis products replaced some coal-fired power generation, and some biochar was used for storage to offset emissions from coal-fired units, reducing daily carbon dioxide emissions by 1,323 tons, a decrease of 15.2%. Renewable energy curtailment penalty costs decreased by RMB 49,000, mainly because the co-firing units have better operational flexibility, increasing the capacity for renewable energy absorption, and reducing system curtailment by 42.9%.

[0067] Comparison of time-series power balance in Scenario 1 and Scenario 2 Figure 4 As shown. According to Figure 4 It can be seen that during the periods of 2-8 AM and 1 PM, the units in Scenario 1... and The output is 176MW, while in scenario two the output is 151.4MW. The output of the two co-firing units is reduced by 14%, which promotes wind power consumption at night. Figure 5 The chart shows a comparison of renewable energy curtailment for Scenario 1 and Scenario 2 during the 2-1 PM time period. Curtailment is minimal during other times. Scenario 2 shows lower curtailment in each time period compared to Scenario 1, with the largest decrease occurring in the third time period, where curtailment decreased by 47.7%.

[0068] Figure 6 The image shows the utilization of biochar in Scenario 2. According to... Figure 6It is known that during most periods, biochar is mainly used for power generation along with other pyrolysis products. However, during periods of renewable energy curtailment, such as 3-8 AM and 1 PM, some biochar is used for sequestration. This serves two purposes: firstly, to offset carbon emissions from coal-fired power generation, and secondly, to reduce the heat energy input to the boiler, thereby reducing the output of co-firing units and providing space for renewable energy consumption. The biochar used for sequestration amounts to 67.8 tons, which is equivalent to reducing carbon dioxide emissions by 186.4 tons.

[0069] Example 2: A computer-readable storage medium includes a stored computer program; when executed by a processor, the computer program implements the optimized scheduling method for a power system including a biomass indirect coupling co-firing unit provided in Embodiment 1 above.

[0070] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An optimized scheduling method for a power system comprising biomass indirect coupling and co-firing units, characterized in that, include: The objective function is to minimize the sum of power generation cost, coal-fired unit start-up cost, carbon trading cost, and curtailment penalty, with the mass of thermal coal input to the boiler for each coal-fired unit at each time step as the criterion. The mass of biomass input into the pyrolysis furnace of each coal-fired unit at each time point. Start-up status of each coal-fired unit Net carbon dioxide emissions of each coal-fired unit at each time point and the amount of renewable energy curtailed by each renewable energy unit at each time point. To optimize variables, a power system dispatch model is established; The power system scheduling model is solved under preset constraints to obtain an optimized scheduling plan. Among them, subscript Indicates the index of coal-fired power units, subscript Indicates the index of renewable energy units, subscript Indicates time; Indicates coal-fired power unit exist The system is set to start at any time; the power generation cost includes the cost of thermal coal and the cost of biomass; the preset constraints include: power balance constraints, system reserve constraints, line power flow constraints, renewable energy unit output constraints, and operating constraints of pyrolysis furnaces, boilers, and steam turbines in coal-fired units.

2. The optimized dispatching method for a power system including biomass indirect coupling and co-firing units as described in claim 1, characterized in that, Net carbon dioxide emissions of each coal-fired unit at each time point The calculation formula is: ； in, Indicates the emission factor of thermal coal; This indicates the reduction in carbon dioxide emissions due to biochar sequestration, and , This indicates the reduction in carbon dioxide emissions per unit mass of biochar stored. This indicates the mass of biochar produced by biomass pyrolysis. This indicates the quality of biochar used for power generation.

3. The optimized scheduling method for a power system including biomass indirect coupling and co-firing units as described in claim 2, characterized in that, The operational constraints of a pyrolysis furnace include: The relationship between the production of pyrolysis gas, pyrolysis oil, and biochar and the input of biomass fuel satisfies: ； Among them, superscript This indicates the types of biomass pyrolysis products in the pyrolysis furnace. Indicates pyrolysis gas. Indicates pyrolysis oil. Indicates biochar; The first generation produced by biomass pyrolysis The yield of the product, This indicates the amount of biomass produced per unit mass of pyrolysis. Yield of the product; Energy consumption of pyrolysis furnace satisfy: ； in, For the start-up of the pyrolysis furnace, Indicates coal-fired power unit The pyrolysis furnace in Start at any time; The energy required for the pyrolysis of a unit mass of biomass. This is the start-up energy consumption of the biomass pyrolysis furnace; The biomass mass input to the pyrolysis furnace during operation satisfy: ； in, It is used to indicate coal-fired power units In the intermediate pyrolysis furnace The binary variable representing the running state at any given moment. Indicates coal-fired power unit The pyrolysis furnace in Always online Indicates coal-fired power unit The pyrolysis furnace in Always offline; and These represent the upper and lower limits of the rate at which the pyrolysis furnace processes biomass feedstock; The pyrolysis furnace operates under the following conditions: ； in, As an indicator variable for indirect co-firing modification of biomass, Indicates coal-fired power unit Biomass co-firing modification has been carried out. Indicates coal-fired power unit No biomass co-firing modification was carried out; The minimum start-up and shutdown time for the pyrolysis furnace operation must meet the following requirements: ； in, It is an indicator variable for pyrolysis furnace shutdown. Indicates coal-fired power unit The pyrolysis furnace in The machine is always shut down; and These represent the shortest time spans for the pyrolysis furnace to be in operation and shutdown states, respectively. The relationship between the operating states of the pyrolysis furnace satisfies: ； The number of start-ups and shutdowns of the pyrolysis furnace satisfies: ； in, Indicates the scheduling period; This is the upper limit for the number of times a pyrolysis furnace can be started during the scheduling period; The energy from the pyrolysis products fed into the boiler from the pyrolysis furnace is used to replace the energy from the pyrolysis products of thermal coal. satisfy: ； in, , and The values ​​are the lower heating values ​​of pyrolysis gas, pyrolysis oil, and biochar, respectively.

4. The optimized dispatching method for a power system including biomass indirect coupling and co-firing units as described in claim 3, characterized in that, Boiler operating constraints include: Total heat energy input to boiler satisfy: ； ； in, It has the lower calorific value of thermal coal; To indicate coal-fired power units exist The binary variable representing the online status at any given time. This indicates that the boiler is running online. This indicates that the boiler is offline; and They represent coal-fired power units Minimum and maximum input power of medium-sized boilers; The boiler's minimum online operating time and minimum downtime meet the following requirements: ； in, To indicate coal-fired power units exist Binary variables that are constantly halting. Indicates coal-fired power unit exist The machine is always shut down; and Coal-fired units Minimum continuous online operation and downtime; The boiler's ramp-up rate satisfies: ； in, and Coal-fired units The rate at which the boiler climbs uphill and downhill; and Coal-fired units The start-up and shutdown operating capacity of the medium-sized boiler; The operating state transition relationship of coal-fired power units satisfies: ； Biomass co-firing rate in boilers satisfy: ； ； in, This represents the upper limit of the biomass indirect coupling co-firing rate; The heat power input from the boiler to the steam turbine satisfies: ； ； in, for Coal-fired power units The boiler inputs thermal power to the steam turbine; For coal-fired power units exist Boiler efficiency during indirect coupling of combustion at all times; and Coal-fired units Maximum and minimum input thermal power of the steam turbine; Boiler efficiency satisfy: ； in, This indicates the boiler efficiency when no biomass is burned. It is the slope of the boiler efficiency as a function of the co-firing rate.

5. The optimized dispatching method for a power system including biomass indirect coupling and co-firing units as described in claim 4, characterized in that, The operating constraints of a steam turbine include: The steam turbine output power meets the following requirements: ； ； ； ； in, For coal-fired power units exist The electrical power output at any given time; For use in coal-fired power units The number of nodes in the output curve segmented for coal-fired power units. The output curve was this Each node is divided into The first node corresponds to the minimum input thermal power of the steam turbine, and the last node corresponds to the maximum input thermal power of the steam turbine. As a continuous auxiliary variable, it represents the coal-fired power unit. exist Time of the first The weight of each node in the turbine power and generator power. It is a non-negative number; This is a binary auxiliary variable indicating whether the current turbine operating state is at the [number]th [position]. part.

6. The optimized scheduling method for a power system including biomass indirect coupling and co-firing units as described in claim 5, characterized in that, The power balance constraint is: ； Among them, subscript Indicates the index of external power transmission lines, subscript Indicates the load node index; Indicates the number of coal-fired power units. Indicates the number of renewable energy units. Indicates the number of external power transmission lines. Indicates the number of load nodes; Indicates renewable energy units exist Power output at any time Indicates the current area and external power transmission lines exist The switching power at any given moment; Indicates load node exist The workload of the moment.

7. The optimized dispatching method for a power system including biomass indirect coupling and co-firing units as described in claim 6, characterized in that, The system's backup constraint is: ； in, Indicates coal-fired power unit Maximum output power Indicates coal-fired power unit Minimum output power; Indicates renewable energy units exist Capacity factor at time, Indicates renewable energy units Rated capacity; and These are the upper and lower reserve coefficients of the system, respectively.

8. The optimized dispatching method for a power system including biomass indirect coupling and co-firing units as described in claim 7, characterized in that, For any external transmission line The power flow constraint of the line is: ； in, Indicates external power transmission line The power transmission limit of the current, Indicates coal-fired power unit External power transmission lines The power flow distribution transfer factor Indicates renewable energy units External power transmission lines The power flow distribution transfer factor Indicates external power transmission line The node and the external transmission line The power flow distribution transfer factor Indicates load node External power transmission lines The power flow distribution transfer factor.

9. The optimized dispatching method for a power system including biomass indirect coupling and co-firing units as described in claim 8, characterized in that, The output constraint of the renewable energy unit is: 。 10. A computer-readable storage medium, characterized in that, The system includes a stored computer program; when the computer program is executed by a processor, it implements the optimized scheduling method for a power system comprising a biomass indirect coupling co-firing unit as described in any one of claims 1 to 9.

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