Two-stage scheduling method of carbon capture-wind-solar-thermal-storage combined system considering demand response

Abstract

The invention discloses a two-stage scheduling method of a carbon capture-wind-solar-thermal-storage combined system considering demand response. The method comprises the following steps: analyzing operation characteristics of a carbon capture unit, a pumped storage unit and demand response during combined operation in load peak and valley periods; on the basis of considering the constraint of a line on flexible scheduling, a two-stage low-carbon flexible scheduling method is provided: in the first stage, through load prediction and photovoltaic wind power output prediction results, in combination with the setting of time-of-use electricity price, the net load fluctuation of a system in each time period is minimized by utilizing PDR, and a load curve after PDR optimization is obtained; in the second stage, the load obtained after PDR optimization in the first stage is utilized, a carbon capture unit, a pumped storage unit and an IDR are combined, meanwhile, line transmission flexibility constraints are considered, and a scheduling scheme under the optimal cost is obtained. According to the scheduling result obtained through the two-stage low-carbon flexible scheduling method, economic cost is reduced, certain flexibility is guaranteed, economical efficiency is improved, carbon emission is reduced, and the wind and light absorption rate is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible dispatching of power systems, and in particular to a two-stage dispatching method for a carbon capture-wind-solar-thermal-storage combined system taking demand response into consideration. Background Art

[0002] As the low-carbonization process of the power system advances, more and more wind and solar units are connected to the power grid. Due to the volatility and uncertainty of wind and solar output, higher requirements are placed on the flexibility and adjustment capabilities required by the system. At the same time, carbon capture units with better low-carbon performance than traditional thermal power units are gradually being used in the power system. Pumped storage units, as a good flexible scheduling resource, can coordinate and cooperate with output by changing their own working status, thereby enhancing the system's wind and solar absorption level.

[0003] Demand response, as a means of load-side regulation, promotes wind and solar power consumption and reduces carbon emissions by reasonably regulating the load. Most of the existing dispatching strategies consider the combined operation of the above three, and few literatures study the combined operation of the three. At present, a large number of literatures on flexibility research focus on whether the supply of flexibility resources is balanced with the flexibility demand of the system, and there are few literatures that consider whether the line transmission capacity meets the flexibility demand of the system. According to the conclusions drawn from existing literature, when the line transmission capacity is insufficient, it will lead to the inability to dispatch only based on the plan obtained by the balance of supply and demand of resource flexibility, which may lead to the abandonment of wind and solar power or load shedding.

[0004] As the low-carbonization process of the power system advances, wind and solar units account for an increasing proportion of the system, and their own uncertainty and volatility also bring challenges to the flexibility of system scheduling. Currently, few literatures consider the impact of line transmission capacity on flexible scheduling. Therefore, a scheduling scheme that considers line transmission flexibility and can combine flexible resources on both sides of the source and load is needed. Summary of the invention

[0005] Aiming at the scheduling problems caused by the volatility of wind and solar power output in the power system, the low-carbon goal can be better achieved at the same time. The present invention proposes a two-stage scheduling method for a carbon capture-wind, solar, thermal and storage combined system considering demand response. According to the operation mechanism of demand response, the method proposes a two-stage low-carbon flexible scheduling method; in the first stage, the load curve is optimized by using PDR; in the second stage, the obtained results are used to obtain a scheduling scheme through the joint operation of carbon capture units, pumped storage, and IDR, and considering the line transmission flexibility constraints. Finally, CPLEX is used in MATLAB for simulation and solution. The results show that compared with the scheduling scheme proposed in the existing literature, the scheduling results obtained by the two-stage low-carbon flexible scheduling method proposed in the present invention reduce economic costs while ensuring a certain flexibility, improve economic efficiency, reduce carbon emissions, and increase wind and solar power consumption rates.

[0006] The technical solution adopted by the present invention is:

[0007] A two-stage dispatching method for a carbon capture-wind-solar-thermal-storage combined system considering demand response is characterized by comprising the following steps:

[0008] Step 1: Analyze the operating characteristics of the carbon capture unit, pumped storage unit and demand response unit during peak and valley load periods;

[0009] Step 2: Based on the consideration of the line's flexible scheduling constraints, a two-stage low-carbon flexible scheduling method is proposed:

[0010] In the first stage, through the load forecast and photovoltaic and wind power output forecast results, combined with the time-of-use electricity price setting, the price-based demand response (PDR) is used to minimize the net load fluctuation of the system in each period, and the load curve optimized by the price-based demand response (PDR) is obtained;

[0011] In the second stage, the PDR-optimized load obtained in the first stage is used in combination with carbon capture units, pumped storage units, and incentive demand response IDR, while considering line transmission flexibility constraints to obtain a dispatch plan with the optimal cost.

[0012] In step one, on the power supply side, the carbon capture power plant is operated in a comprehensive and flexible mode. During peak load periods, the carbon capture operation energy consumption is reduced to increase the net output of the power plant; during low load periods, the carbon capture energy consumption is increased to further reduce CO2 emissions. Pumped storage units can generate electricity or pump water according to real-time requirements, so they have good flexibility in scheduling. On the load side, price-based demand response (PDR) guides users' electricity consumption to a certain extent by adjusting time-of-use electricity prices, reducing load peaks and increasing load valleys, thereby better balancing the fluctuations in net loads in each period and reducing the scheduling pressure on each unit in the system. Incentive demand response (IDR) reduces loads during specific periods by signing agreements with users, while giving users certain compensation, thereby alleviating scheduling pressure.

[0013] Taking into account the operating characteristics of the above-mentioned carbon capture units, pumped storage units and demand response, the system in which the carbon capture units, pumped storage units and demand response operate jointly is analyzed, and a comparison is made between the two situations with and without considering demand response, and the operating mechanism during the peak and trough periods of net load is analyzed.

[0014] In step 1, the net output analysis of the carbon capture unit with comprehensive and flexible operation is as follows:

[0015] The net output of a carbon capture power plant is equal to the total output minus the total carbon capture energy consumption. The energy consumption of a carbon capture power plant consists of two parts: fixed energy consumption and operating energy consumption. The operating energy consumption is related to the operating state of the carbon capture unit, while the fixed energy consumption is the energy loss generated by the carbon capture power plant itself and has nothing to do with the operating state. The power relationship of a carbon capture power plant is shown in formula (1):

[0016]

[0017] In formula (1): P g represents the total output of the carbon capture power plant; P n represents the net output of the carbon capture power plant; P o represents the operating energy consumption of the carbon capture power plant; P f represents the fixed energy consumption of the carbon capture power plant; λ c E represents the energy consumption required by the carbon capture power plant to capture unit CO2; e Represents the total mass of CO2 produced by the power plant; γ c Indicates the maximum operating coefficient of the compressor and regeneration tower; P gmax represents the maximum output of the carbon capture power plant; Represents the mass of CO2 captured by the carbon capture power plant; β c represents the carbon capture efficiency of the carbon capture power plant; δ c represents the flue gas split ratio of the carbon capture power plant; e c is the carbon emission intensity; is the mass of CO2 to be captured in the solution storage of the carbon capture power plant.

[0018] According to formula (1), the minimum and maximum net output expressions of the carbon capture power plant can be obtained as shown in formula (2):

[0019]

[0020] In formula (2): P omax represents the maximum operating energy consumption of the carbon capture power plant; P gmax and P gmin Respectively represent the maximum and minimum output of the carbon capture power plant; P f represents the fixed energy consumption of the carbon capture power plant; P nmax and P nmin Represent the maximum and minimum output of the carbon capture power plant respectively.

[0021] The maximum operating energy consumption of the carbon capture power plant is calculated as shown in formula (3):

[0022] P omax =γ c e c β c P gmax (3);

[0023] In formula (3): β c Represents the carbon capture efficiency of the carbon capture power plant.

[0024] In step 1, price-based demand response (PDR) is used as a load-side regulation method to guide users' electricity consumption behavior and reduce load fluctuations by adopting a time-of-use electricity price strategy. On the one hand, it reduces the load peak value to a certain extent and improves the low-carbon economic operation of the system. On the other hand, it increases the load valley value and better improves the system's new energy absorption capacity. The relationship between the electricity price and the load change in each period is expressed by formula (4):

[0025]

[0026] In formula (4): p , g , f are the load change rates during the flat, trough and peak periods respectively; D p , D g , D f are the time-of-use electricity prices during flat, trough and peak periods respectively; E is the demand elasticity matrix of PDR.

[0027] In step one, the integrated demand response (IDR) is an agreement signed between the power company and users with regulation capabilities to reduce the load during a specific period of time, and the user can receive certain compensation. Therefore, IDR can be used as a scheduling resource.

[0028] In step 1, pumped storage, as a good flexible resource, can accomplish the task of peak load shaving and valley filling to a high degree. It has two working states during operation and needs to satisfy the working condition conversion constraint as shown in formula (5):

[0029]

[0030] In formula (5): t is the time; is the operating state variable of the pumped storage unit at time t. If it is in pumping condition, then is 1, is 0; if it is in power generation condition, is 0, is 1; is the operating state variable of the pumped storage unit at time t-1; T is the scheduling period, which is 24.

[0031] Pumped storage needs to meet the pumping power constraint and reservoir capacity constraint under both working conditions, as shown in formula (6):

[0032]

[0033] In formula (6): t is the time; P se,t is the pumped power of the pumped storage unit at time t; P psmax is the maximum power of the pumped storage unit; is the water capacity of the reservoir at time t; is the water capacity of the reservoir at time t-1; are the initial water capacity of the upper reservoir and the water capacity at the end of scheduling, respectively; η psc , η psg are the water conversion coefficient of the pumped storage unit in the pumping state and the power conversion coefficient in the power generation state; P psc,t , P psg,t are the pumping and generating power of the pumped storage unit at time t, respectively; are the minimum and maximum water capacities of the upper reservoir respectively.

[0034] In step 1, the operating characteristics of the combined operation of the carbon capture unit, the pumped storage unit and the demand response are analyzed as follows:

[0035] On the power supply side, the pumped storage unit and the carbon capture unit are operated together. When the load is peak, the net output of the unit is increased by reducing the energy consumption of the carbon capture unit, and the pumped storage unit is used to generate electricity, so as to absorb as much new energy output as possible and reduce the output of thermal power units, thereby reducing carbon emissions. When the load is low, the carbon capture energy consumption of the carbon capture unit is increased to reduce the carbon emissions of the carbon capture unit, and the pumped storage unit is used to pump water to fill the valley, promote the absorption of new energy, and reduce the generation of wind and solar power abandonment.

[0036] On the load side, price-based demand response (PDR) is used to transfer part of the load during peak hours to off-peak hours to avoid large fluctuations in the load curve. On the one hand, it reduces the use of carbon-emitting and expensive thermal power units due to the need for a large number of thermal power units. On the other hand, it can also increase the output of new energy during off-peak hours, and prevent the abandonment of wind and solar power due to low load demand as much as possible.

[0037] In step 2, the node flexibility demand mainly comes from the fluctuation of net load and the prediction error of wind, solar and load. The net load and flexibility demand of the node at each moment are shown in formula (7):

[0038]

[0039] In formula (7): F de,i,t is the flexibility requirement of node i at time t; P d,i,t is the load forecast value of node i at time t; P net,i,t is the net load demand of node i at time t; P wpre,i,t , P vpre,i,t are the wind power and photovoltaic power forecast outputs at node i at time t; △P l,i,t , △P wpre,i,t , △P vpre,i,t are the prediction errors of the load and wind / solar output of node i at time t; △P net,i,t is the net load error of node i at time t; P net,i,t+1 is the net load demand of node i at time t+1.

[0040] The node flexibility demand is directional. The net load demand of each node obtained by equation (7) can be used to calculate the upward and downward flexibility demands of the corresponding node, as shown in equations (8) and (9):

[0041]

[0042] In formula (8) and formula (9): are the upward and downward flexibility requirements of node i at time t; F de,i,t is the flexibility requirement of node i at time t.

[0043] The flexibility requirements of each node obtained by equations (8) and (9) are used to obtain the line flexibility transmission power requirement of each line using the power transmission distribution factor (PTDF). The calculation process is shown in equation (10):

[0044]

[0045] In formula (10): are the upward and downward transmission requirements of line l at time t respectively; G i,l is the power transfer distribution factor of node i to line l; are the upward and downward flexibility requirements of node i at time t respectively; ∑ represents the summation sign; L is the total number of lines.

[0046] In step 2, the two-stage low-carbon flexible scheduling method is as follows:

[0047] In the first stage, consider using PDR to process the load forecast and wind and solar output forecast results to obtain an optimized load curve. The purpose is to reduce the difference in net load between adjacent time periods, reduce the peak-to-valley difference in load, and alleviate the dispatch pressure of the unit. The minimum net load square difference is taken as the objective function 1, as shown in formula (11):

[0048]

[0049] In formula (11): f1 is the objective function 1; t is the time; P net,t is the net load at time t; P net,t+1 is the net load at time t+1; ∑(·) is the summation function; min(·) is the minimum function.

[0050] In the second stage, the optimal scheduling scheme is obtained with the objective function 2 as the minimum total cost.

[0051] The objective function 2 is shown in formula (12):

[0052] f2=min(C M +C G +C R +C Q +C S +C IDR ) (12);

[0053] In formula (12): f2 represents the objective function 2; C M represents the coal consumption cost of thermal power units; C G represents the start-up and shutdown cost of thermal power units; C R represents the solution loss cost of the carbon capture unit; C Q C represents the penalty cost for abandoning wind and solar power; S represents the operating cost of the pumped storage unit; CIDR represents the call cost of IDR; min(·) represents the minimum function.

[0054] In step 2, the total load before and after price-based demand response (PDR) remains unchanged, as shown in formula (13):

[0055]

[0056] In formula (13): P l,t , P lpdr,t are the load before PDR and the load after PDR of the system at time t respectively;

[0057] In step 2, the user satisfaction constraint is as shown in equations (14) and (15):

[0058]

[0059] In formula (14): It is the minimum value of satisfaction with electricity usage.

[0060]

[0061] In formula (15): P l,t , P lpdr,t are the load before PDR and the load after PDR of the system at time t respectively; D is the minimum satisfaction value of electricity expenditure; t , D pdr,t are the electricity price before PDR and the electricity price after PDR at time t respectively.

[0062] In step 2, the coal consumption cost C of the thermal power unit M , as shown in formula (16):

[0063]

[0064] In formula (16): C M is the coal consumption cost of thermal power units; a i , bi , ci are the coal consumption coefficients of the i-th thermal power plant; P gi,t is the total output of the i-th thermal power plant at time t; N g is the number of conventional thermal power plants; N g is the number of conventional thermal power plants.

[0065] Start-up and shutdown cost of thermal power units C G , as shown in formula (17):

[0066]

[0067] In formula (17): CG is the start-up and shutdown cost of thermal power units; Hu i 、Hd i are the start-up and shutdown costs of the i-th thermal power unit; u gi,t is the operating state variable of the i-th thermal power unit at time t. When it is 1, it means the unit is running at this time; when it is 0, it means the unit is stopped at this time; u gi,t-1 The operating state variables of the i-th thermal power unit at time t-1.

[0068] Solution loss cost of carbon capture power plant C R , as shown in formula (18):

[0069] C R =Q r ψE cap,t (18);

[0070] In formula (18): t is the time; C R is the solution loss cost of the carbon capture power plant; Q r is the cost coefficient of the storage solution of the carbon capture unit; ψ is the solution loss coefficient; E cap,t is the mass of CO2 captured by the carbon capture unit at time t.

[0071] Penalty cost for wind and solar curtailment C Q , as shown in formula (19):

[0072]

[0073] In formula (19): C Q Penalty cost for wind and solar curtailment; K cur P is the penalty coefficient for wind and solar power abandonment; wcur , P vcur are the amount of wind and solar power abandoned at time t respectively.

[0074] Operation cost of pumped storage unit C S , as shown in formula (20):

[0075]

[0076] In formula (20): C S is the operating cost of the pumped storage unit; K psg , K psc are the start-up and shutdown costs of the pumped storage unit for power generation and water pumping, respectively; are the pumping and power generation state variables of the pumped storage unit at time t respectively; are the pumping and power generation state variables of the pumped storage unit at time t-1 respectively.

[0077] IDR call cost C IDR , as shown in formula (21):

[0078]

[0079] In formula (21): C IDR is the IDR call cost; P idr,t K is the load reduced by the system IDR at time t; idr is the call cost coefficient of IDR.

[0080] In step 2, conventional thermal power units need to meet the output constraints, as shown in formula (22):

[0081] u gi,t P gmin,i ≤P gi,t ≤u gi,t P gmax,i (twenty two);

[0082] In formula (22): u gi,t is the operating state variable of the i-th thermal power unit at time t. When it is 1, it means the unit is running at this time; when it is 0, it means the unit is stopped at this time; P gmin,i , P gmax,i are the minimum and maximum output of the i-th thermal power unit at time t; P gi,t is the output of the i-th thermal power unit at time t.

[0083] Conventional thermal power units need to meet the ramp constraints, as shown in formula (23):

[0084]

[0085] In formula (23): P gi,t is the output of the i-th thermal power unit at time t; u gi,t is the operating state variable of the i-th thermal power unit at time t. When it is 1, it means the unit is running at this time; when it is 0, it means the unit is stopped at this time; P gu,i , P gd,i are the upward and downward climbing powers of the i-th thermal power unit respectively; P gi,t-1 is the output of the i-th thermal power unit at time t-1; u gi,t-1 The operating state variables of the i-th thermal power unit at time t-1.

[0086] The CO2 extracted from the solution storage is stored in the amine solution, and the relationship between the CO2 mass and the solution volume is described by equation (24):

[0087]

[0088] In formula (24): V ci,t For the jThe volume of solution consumed by the storage installed in a carbon capture power plant to release CO2 at time t; θ is the amount of CO2 reduced from the rich solution to the lean solution; ε r is the concentration of the solution in the reservoir; The mass of CO2 provided to the storage tank of the i-th carbon capture power plant at time t; ρ r is the concentration of the solution in the storage; M mea , are the molar masses of MEA and CO2, respectively.

[0089] When the carbon capture unit is in operation, the volume of the remaining solution in the storage must also be considered, and its constraint is shown in equation (25):

[0090]

[0091] In formula (25): V pj,t 、V fj,t Respectively j The remaining volume of the lean solution and the rich solution in the solution storage of a carbon capture power plant at time t; V smax,j For the j The maximum capacity of the solution storage in a carbon capture power plant; V cj,t For the j The volume of solution consumed by the storage installed in a carbon capture power plant to release CO2 at time t; V pj,t-1 、V fj,t-1 Respectively j The residual volume of the solution in the lean liquid tank and the rich liquid tank at time t-1 of a carbon capture power plant.

[0092] When the carbon capture power plant is operated according to the constraint of formula (25), in order to enable the system to be normally dispatched, the volume of the solution should also satisfy formula (26):

[0093]

[0094] In formula (26): V pj,0 、V pj,24 Respectively j The initial volume of the lean liquid tank in a carbon capture power plant and the remaining volume at the end of the dispatch; V fj,0 、V pj,24 Respectively j The initial volume of the rich liquid tank in a carbon capture plant and the remaining volume at the end of dispatch.

[0095] In step 2, the entire system needs to meet the unit output power balance constraint when running, as shown in formula (27):

[0096]

[0097] In formula (27): Plpdr,t is the load after PDR of the system at time t; P w,t , P v,t are wind power output and photovoltaic output at time t respectively; P gi,t is the output of the i-th thermal power unit; P n,t is the net output of the carbon capture power plant; P idr,t is the load reduced by the system IDR at time t; P se,t is the pumped power of the pumped storage unit at time t; N g is the number of conventional thermal power plants.

[0098] DC power flow refers to the calculation of power flow between nodes in the power system through the DC power flow equation to achieve system balance and stable operation. The constraint is set by equation (28):

[0099]

[0100] In formula (28): N G 、N L are the number of generator nodes and the number of load nodes respectively; P i,t , P d,t are the output of the generator at node i at time t and the node j Load demand; P l,s,t is the power flow of line s at time t; P lmax,s is the maximum transmission power of line s; G x-i , G x-j are generator node i and load node i respectively j The power transmission distribution factor of line x. In step 2, the influence of line transmission capacity on system flexibility scheduling is considered, which is judged by whether the transmission capacity of the line meets the flexibility requirements of each node mapped to the sum of the requirements on each branch. When discussing flexibility requirements, it is generally divided into two directions: upward and downward. The transmission flexibility constraint of the line is shown in formula (29):

[0101]

[0102] In formula (29): pr{·} is the probability of an event occurring; and are the downward and upward transmission flexibility margins of line s at time t, respectively; and are the downward and upward resource flexibility margins of the system at time t, respectively; The confidence level for the line transmission flexibility constraint.

[0103] When the line power flow direction is opposite to the line transmission flexibility demand direction, the above formula (29) As shown in formula (30):

[0104]

[0105] In formula (30): |·| is the absolute value function; and are the downward and upward transmission flexibility margins of line s at time t, respectively; P l,s,t is the power flow of line s at time t; P lmax,s is the maximum transmission power of line s; are the flexibility upward and downward transmission requirements of line s at time t, respectively.

[0106] When the line power flow direction and the line transmission flexibility demand direction are the same, the above formula (29) As shown in formula (31):

[0107]

[0108] In formula (31): and are the downward and upward transmission flexibility margins of line s at time t, respectively; P l,s,t is the power flow of line s at time t; P lmax,s is the maximum transmission power of line s; are the flexibility upward and downward transmission requirements of line s at time t, respectively.

[0109] In step 2, resource flexibility constraints are as shown in formula (32):

[0110]

[0111] In formula (32): and They are the downward and upward resource flexibility margins of the system at time t respectively.

[0112] In the above formula (32), and They are shown in the following formula (33):

[0113]

[0114] In formula (33): and They are the downward and upward resource flexibility margins of the system at time t respectively; They are the upward and downward flexibility supply of thermal power units at time t respectively; They are the upward and downward flexibility supply of the i-th carbon capture unit at time t, respectively; They are the upward and downward flexible supply of the pumped storage unit at time t; They are the upward and downward flexibility supply of IDR of node i at time t; are the upward and downward flexibility requirements of node i at time t; N G 、N L , N are the number of generator nodes, the number of load nodes and the total number of nodes respectively.

[0115] Step 3: Simulate the operating conditions at the improved IEEE30 node. Compare the scheduling scheme proposed by the present invention with other scheduling schemes, specifically:

[0116] The dispatch results under various schemes are simulated in the improved IEEE30 node system. Carbon capture units and pumped storage units are added to the improved IEEE30 node system, and four different schemes are set to verify the dispatch effect after considering demand response and the impact of line transmission flexibility constraints on the dispatch results.

[0117] The two-stage low-carbon flexible scheduling method proposed in the present invention performs scheduling on both the source and load sides at the same time, takes into account the line transmission flexibility constraints, and obtains the optimal scheduling result by comprehensively considering economy and flexibility. The obtained solution reduces economic costs, reduces carbon emissions, and improves wind and solar power consumption rates.

[0118] The present invention provides a two-stage scheduling method for a carbon capture-wind-solar-thermal-storage combined system considering demand response, and the technical effects are as follows:

[0119] 1) Based on the individual operating characteristics of carbon capture power plants, demand response and pumped storage, the present invention analyzes the operating mechanisms of the three in different load periods when they are operated together.

[0120] 2) Based on the results of the previous analysis, a two-stage low-carbon flexible scheduling method is proposed. In order to fully demonstrate the effectiveness of the model, different scenarios are set for comparison.

[0121] 3) The present invention proposes a two-stage low-carbon flexible dispatching method for the new energy power system. The system is flexibly dispatched on both the source and load sides, and the flexibility of line transmission is taken into consideration. While reducing the carbon emissions of the system, the wind and solar power absorption capacity of the system is improved and the operating cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0122] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0123] Figure 1 This is the improved IEEE 30-node system wiring diagram.

[0124] Figure 2 Schematic diagram of the internal operation of a carbon capture power plant.

[0125] Figure 3 Schematic diagram of system operation in different load periods.

[0126] Figure 4 It is a two-stage scheduling method model.

[0127] Figure 5 Optimize the load curves before and after PDR and the electricity price chart for each time period.

[0128] Figure 6 This is the scheduling result of Scheme 1.

[0129] Figure 7 This is the scheduling result of scheme 2.

[0130] Figure 8 This is the scheduling result of scheme 3.

[0131] Fig. 9 This is the scheduling result for Scheme 4.

[0132] Fig.10 This is a comparison chart of carbon capture energy consumption. DETAILED DESCRIPTION

[0133] Flexible dispatch of carbon capture-wind-solar-thermal-storage combined system considering demand response A dispatch method for the combined operation of pumped storage, demand response, and carbon capture power plants is proposed, including the following steps:

[0134] Step 1: Analysis of the operating characteristics of the carbon capture unit and the operating mechanism of demand response, the flexibility supply capacity of each unit and the requirements of the system flexibility demand on the line transmission capacity, and the operating mechanism of the three combined;

[0135] Step 2: Considering the operation mechanism in step 1 and the line transmission flexibility constraints, a two-stage low-carbon flexible dispatch model is proposed. The first stage uses PDR to optimize the load, and the second stage uses a variety of flexible resources for dispatching.

[0136] Step 3: Simulate the scheduling in the improved IEEE30-node system and compare it with the scheduling results of the carbon capture unit, pumped storage and demand response respectively. The scheduling results obtained by the model proposed in the present invention reduce carbon emissions, increase the wind and solar power consumption rate and improve economy while ensuring flexibility.

[0137] On the source side, the combined operation of carbon capture and pumped storage can reduce carbon emissions while utilizing the flexible adjustment capabilities of pumped storage units to ensure the flexibility of the system; on the load side, demand response can be considered to further promote the low-carbon operation of the system; on the grid side, the line transmission flexibility of the power grid can be considered to optimize the scheduling of the system.

[0138] (I) Analysis of the operation of each resource:

[0139] At present, carbon capture power plants mostly adopt a comprehensive and flexible operation mode. During peak load periods, the power used for carbon capture by the units is reduced to increase the net output of the power plant. Conversely, during low load periods, the power used for carbon capture by the units is increased to further reduce CO2 emissions, and the net output of the power plant is reduced at this time. The specific internal structure operation diagram is as follows Figure 2 As shown, from Figure 2 It can be seen that the CO2 generated by the combustion of the carbon capture power plant will first be discharged directly into the atmosphere through the flue gas bypass, and the other part will be processed by the absorption tower, and one part of the CO2 will be absorbed into the solution in the rich liquid tank, and the other part will be directly discharged. The CO2 stored in the rich liquid tank will be separated from the solution by the regeneration tower, and finally compressed and sealed by the compression device. The lean and rich liquid tank is used to achieve the reuse of the solution.

[0140] The net output of a carbon capture power plant is equal to the total output minus the total power used by the unit to capture CO2. The energy consumption of a carbon capture power plant consists of two parts: fixed energy consumption and operating energy consumption. The operating energy consumption is related to the operating state of the carbon capture unit, while the fixed energy consumption is the energy loss generated by the start-up operation of the carbon capture power plant unit, which is independent of the current operating state and generally takes a fixed value. The power relationship of a carbon capture power plant is shown in formula (1):

[0141]

[0142] In formula (1): P g represents the total output of the carbon capture power plant; P n represents the net output of the carbon capture power plant; P o represents the operating energy consumption of the carbon capture power plant; P f represents the fixed energy consumption of the carbon capture power plant; λ c E represents the energy consumption required by the carbon capture power plant to capture unit CO2; e Represents the total mass of CO2 produced by the power plant; γ c Indicates the maximum operating coefficient of the compressor and regeneration tower; P gmax represents the maximum output of the carbon capture power plant; Represents the mass of CO2 captured by the carbon capture power plant; β c represents the carbon capture efficiency of the carbon capture power plant; δ c represents the flue gas split ratio of the carbon capture power plant; e c is the carbon emission intensity; is the mass of CO2 to be captured in the solution storage of the carbon capture power plant.

[0143] According to formula (1), the minimum and maximum net output of the carbon capture power plant can be obtained, as shown in formula (2):

[0144]

[0145] In formula (2): P gmax , P gmin are the maximum and minimum total output of the carbon capture power plant respectively; P nmin , P nmin are the minimum and maximum net outputs of the carbon capture power plant respectively; P f is the fixed energy consumption of the carbon capture power plant; P omax is the maximum operating energy consumption of the carbon capture power plant, and its size is shown in formula (3):

[0146] P omax =γ c e c β c P gmax

[0147] (3); In formula (3): P omax is the maximum operating energy consumption of the carbon capture power plant; γ c is the maximum working state coefficient of the compressor and regeneration tower; β c is the carbon capture intensity; δ c is the flue gas split ratio; P gmax are the maximum total output of the carbon capture power plant; e c is the carbon emission intensity.

[0148] PDR guides users' electricity consumption behavior and reduces load fluctuations by adopting a time-of-use electricity price strategy. On the one hand, it reduces the load peak value to a certain extent and improves the low-carbon economic operation of the system. On the other hand, it increases the load valley value and better improves the system's new energy absorption capacity. The relationship between the electricity price and the load change rate in each period is shown in equation (4):

[0149]

[0150] In formula (4): p , g , f are the load change rates during the flat, trough and peak periods respectively; D p , D g , D f are the time-of-use electricity prices during flat, trough and peak periods respectively; E is the demand elasticity matrix of PDR.

[0151] During the operation of pumped storage, it is necessary to consider the conversion of two working conditions, which are constrained by formula (5):

[0152]

[0153] In formula (5): t is the time; are the operating state variables of the pumped storage unit at time t. If it is in pumping condition, then is 1, is 0; if it is in power generation condition, is 0, is 1; are the operating state variables of the pumped storage unit at time t-1; T is the scheduling period, which is 24.

[0154] At the same time, the pumping and power generation constraints of pumped storage and the reservoir capacity constraints need to be considered, as shown in formula (6):

[0155]

[0156] In formula (6): t is the time; P se,t is the pumped power of the pumped storage unit at time t; P psmax is the maximum power of the pumped storage unit; is the water capacity of the reservoir at time t; is the water capacity of the reservoir at time t-1; are the initial water capacity of the upper reservoir and the water capacity at the end of scheduling, respectively; η psc , η psg are the water conversion coefficient of the pumped storage unit in the pumping state and the power conversion coefficient in the power generation state; P psc,t , P psg,t are the pumping and generating power of the pumped storage unit at time t, respectively; are the minimum and maximum water capacities of the upper reservoir respectively.

[0157] According to the above analysis, carbon capture units can better promote the low-carbon operation of the system. Pumped storage units have good regulation capabilities as a type of energy storage. Demand response can well achieve the effect of peak shaving and valley filling. Joint scheduling of the combined system can further improve low-carbon and flexible operation. Therefore, this section analyzes the combined system in which the three operate together.

[0158] On the power supply side, by operating pumped-storage units and carbon capture power plants together, the net output of the units can be increased during peak load periods by reducing carbon capture energy consumption, and the pumped-storage units can be used to generate electricity, absorb as much new energy output as possible, reduce the output of thermal power units, and thus reduce carbon emissions; when the load is low, the carbon emissions of the units can be reduced by increasing carbon capture energy consumption, and pumped-storage units can be used to pump water to "fill the valley" of the load, thereby promoting the absorption of new energy and reducing the occurrence of wind and solar power abandonment.

[0159] On the load side, PDR can be used to avoid large fluctuations in the load curve during peak hours to off-peak hours. On the one hand, it can reduce the use of carbon-emitting and expensive thermal power units due to the need for a large number of thermal power units. On the other hand, it can also increase the output of new energy during off-peak hours, and prevent the abandonment of wind and solar power due to low load demand and insufficient absorption of new energy.

[0160] Select two time points, load trough and peak, to compare the operation of the combined system with demand response and the system without demand response. The operation diagrams of the two are shown in Figure 2. Figure 3 shown.

[0161] (II): Analysis of power system flexibility:

[0162] The flexibility demand of the power grid comes from the random fluctuation of the net load obtained by combining wind and solar loads.

[16] . It should start from the supply and demand analysis of flexible resources and line transmission capacity.

[0163] The node's flexibility demand mainly comes from the fluctuation of net load and the prediction error of wind, solar and load. The net load of the node refers to the difference between the load and the wind and solar output. The net load and flexibility demand of the node at each moment are shown in formula (7):

[0164]

[0165] In formula (7): t is the time; F de,i,t is the flexibility requirement of node i at time t; P d,i,t is the load forecast value of node i at time t; P net,i,t is the net load demand of node i at time t; P wpre,i,t , P vpre,i,t are the wind power and photovoltaic power forecast outputs at node i at time t; △P l,i,t , △P wpre,i,t , △P vpre,i,t are the prediction errors of the load and wind / solar output of node i at time t; △P net,i,t is the net load error of node i at time t; P net,i,t+1 is the net load demand of node i at time t+1.

[0166] The node flexibility demand is directional. The net load demand of each node obtained by equation (7) can be used to calculate the upward and downward flexibility demands of the corresponding node, as shown in equations (8) and (9):

[0167]

[0168] In formulas (8) and (9): t is the time; are the upward and downward flexibility requirements of node i at time t; F de,i,t is the flexibility requirement of node i at time t.

[0169] Based on the flexibility requirements of each node obtained above, the power transmission distribution factor (PTDF) is used to obtain the line flexibility transmission power requirement of each line. The calculation process is shown in formula (10):

[0170]

[0171] In formula (10): t is the time; are the upward and downward transmission requirements of line l at time t respectively; G i,l is the power transfer distribution factor of node i to line l; are the upward and downward flexibility requirements of node i at time t respectively; ∑ represents the summation sign; L is the total number of lines.

[0172] (III): Two-stage low-carbon flexible scheduling method:

[0173] In order to better reduce the carbon emissions of the system and improve the flexibility of the system, a two-stage flexibility scheduling model is constructed based on the combined operation of carbon capture and pumped storage units combined with the demand response mechanism, while considering the impact of line transmission capacity on system flexibility. The first stage aims to minimize the net load fluctuation after PDR, and the second stage aims to minimize the comprehensive cost under the premise of system flexibility. The two are combined to obtain the final scheduling plan. The model diagram of the two-stage scheduling method is shown in the figure below. Figure 4 shown.

[0174] In the first stage, the minimum fluctuation of net load is taken as the objective function. The PDR is used to guide the user's electricity consumption, adjust the load in each period, and reduce the peak and valley difference of net load, as shown in formula (11):

[0175]

[0176] In formula (11): t is the time; P net,t is the net load of the system at time t; P net,t+1 is the net load at time t+1; f1 is the objective function 1; T is the scheduling period, which is 24 in the present invention; min(·) is the minimum value function; ∑ represents the summation symbol.

[0177] The constraints are:

[0178] (1) The total load before and after PDR remains unchanged, as shown in formula (13):

[0179]

[0180] In formula (13), t is the time; Pl,t , P lpdr,t are the load before PDR and the load after PDR of the system at time t respectively; T is the scheduling period, which is 24 in the present invention; ∑ represents the summation symbol.

[0181] (2) User satisfaction constraint, as shown in equations (13) and (14):

[0182]

[0183] In formula (14), t is the time; P l,t , P lpdr,t are the load before PDR and the load after PDR of the system at time t respectively; is the minimum value of the satisfaction with the electricity consumption mode; T is the scheduling period, which is 24 in the present invention; ∑ represents the summation symbol.

[0184]

[0185] In formula (15), t is the time; P l,t , P lpdr,t are the load before PDR and the load after PDR of the system at time t respectively; D is the minimum satisfaction value of electricity expenditure; t , D pdr,t are respectively the electricity price before PDR and the electricity price after PDR at time t; T is the dispatching period, which is 24 in the present invention; ∑ represents the summation symbol.

[0186] The second stage takes the optimal total operating cost of the system as the objective function, as shown in formula (12):

[0187] f2=C M +C G +C R +C Q +C K +C IDR (12);

[0189] In formula (12): f2 is the objective function 2; C M is the coal consumption cost of thermal power units; C G is the start-up and shutdown cost of thermal power units; C R is the solution loss cost of the carbon capture power plant; C Q Penalty cost for wind and solar curtailment; C S is the operating cost of the pumped storage unit; C IDR Call cost for IDR.

[0190] The cost expressions are as follows:

[0191] (1) Coal consumption cost C of thermal power unitsM , as shown in formula (16):

[0192]

[0193] In formula (16): t is the time; C M is the coal consumption cost of thermal power units; a i , b i 、c i are the coal consumption coefficients of the i-th thermal power plant; P gi,t is the total output of the i-th thermal power plant at time t; N g is the number of conventional thermal power plants; T is the dispatching period, which is 24 in the present invention; N g is the number of conventional thermal power plants; ∑ represents the summation symbol.

[0194] (2) Start-up and shutdown cost of thermal power units C G , as shown in formula (17):

[0195]

[0196] In formula (17): t is the time; C G is the start-up and shutdown cost of thermal power units; Hu i 、Hd i are the start-up and shutdown costs of the i-th thermal power unit; u gi,t is the operating state variable of the i-th thermal power unit at time t. When it is 1, it means the unit is running at this time; when it is 0, it means the unit is stopped at this time; u gi,t-1 is the operating state variable of the i-th thermal power unit at time t-1; T is the scheduling period, which is 24 in the present invention; N g is the number of conventional thermal power plants; ∑ represents the summation symbol.

[0197] (3) Solution loss cost of carbon capture power plant C R , as shown in formula (18):

[0198] C R =Q r ψE cap,t

[0199] (18); In formula (18): t is the time; C R is the solution loss cost of the carbon capture power plant; Q r is the cost coefficient of the storage solution of the carbon capture unit; ψ is the solution loss coefficient; E cap,t is the mass of CO2 captured by the carbon capture unit at time t.

[0200] (4) Penalty cost for wind and solar curtailment C Q , as shown in formula (19):

[0201]

[0202] In formula (19): t is the time; C Q Penalty cost for wind and solar curtailment; K cur P is the penalty coefficient for wind and solar power abandonment; wcur , P vcur are the wind curtailment amount and solar curtailment amount at time t respectively; T is the scheduling period, which is 24 in the present invention; ∑ represents the summation sign.

[0203] (5) Operation cost of pumped storage unit C S , as shown in formula (20):

[0204]

[0205] In formula (20): t is the time; C S is the operating cost of the pumped storage unit; K psg , K psc are the start-up and shutdown costs of the pumped storage unit for power generation and water pumping, respectively; are the pumping and power generation state variables of the pumped storage unit at time t respectively; are the pumping and power generation state variables of the pumped storage unit at time t-1 respectively; T is the dispatching period, which is 24 in the present invention; ∑ represents the summation symbol.

[0206] (6) IDR call cost C IDR , as shown in formula (21):

[0207]

[0208] In formula (21): t is the time; C IDR is the IDR call cost; P idr,t is the load reduced by the system IDR at time t; T is the scheduling period, which is 24 in the present invention; K idr is the call cost coefficient of IDR; ∑ represents the summation symbol.

[0209] The constraints are:

[0210] (1) Output constraints of conventional thermal power units:

[0211] u gi,t P gmin,i ≤P gi,t ≤u gi,t P gmax,i (twenty two);

[0213] In formula (22): t is the time; u gi,t is the operating state variable of the i-th thermal power unit at time t. When it is 1, it means the unit is running at this time; when it is 0, it means the unit is stopped at this time; Pgmin,i , P gmax,i are the minimum and maximum output of the i-th thermal power unit at time t; P gi,t is the output of the i-th thermal power unit at time t;.

[0214] (2) Climbing constraints of conventional thermal power units:

[0215]

[0216] In formula (23): t is the time; P gi,t is the output of the i-th thermal power unit at time t; P gi,t-1 is the output of the i-th thermal power unit at time t-1; u gi,t is the operating state variable of the i-th thermal power unit at time t. When it is 1, it means the unit is running at this time; when it is 0, it means the unit is stopped at this time; u gi,t-1 is the operating state variable of the i-th thermal power unit at time t-1; P gu,i , P gd,i are the upward and downward climbing powers of the i-th thermal power unit respectively.

[0217] (3) Carbon capture power plant constraints:

[0218] The power constraint of the carbon capture power plant is shown in equation (1) above.

[0219] The CO2 extracted from the solution storage is stored in the amine solution, and the relationship between the CO2 mass and the solution volume is described by equation (24):

[0220]

[0221] In formula (24): t is the time; V ci,t is the volume of solution consumed by the storage installed in the jth carbon capture power plant to release CO2 at time t; θ is the amount of CO2 reduced from the rich solution to the lean solution; ε r is the concentration of the solution in the reservoir; The mass of CO2 provided to the storage tank of the i-th carbon capture power plant at time t; ρ r is the concentration of the solution in the storage; M mea , are the molar masses of MEA and CO2, respectively. When the carbon capture unit is in operation, the volume of the remaining solution in the storage must also be considered, and its constraint is shown in formula (25):

[0222]

[0223] In formula (25): t is the time; V pj,t 、V fj,tV is the remaining amount of lean solution and rich solution in the solution storage of the jth carbon capture power plant at time t; pj,t-1 、V fj,t-1 is the remaining amount of lean solution and rich solution in the solution storage of the jth carbon capture power plant at time t-1; V smax,j is the maximum capacity of the solution storage in the jth carbon capture power plant; V cj,t is the volume of solution consumed by the storage installed in the jth carbon capture power plant to release CO2 at time t. In order for the system to be normally dispatched, the volume of the solution should also satisfy formula (26):

[0224]

[0225] In formula (26): t is the time; V pj,0 、V pj,24 Respectively j The initial volume of the lean liquid tank in a carbon capture power plant and the remaining volume at the end of the dispatch; V fj,0 、V pj,24 Respectively j The initial volume of the rich liquid tank in a carbon capture plant and the remaining volume at the end of dispatch.

[0226] (4) Power balance constraints:

[0227]

[0228] In formula (27): t is the time; P lpdr,t is the load after PDR of the system at time t; P w,t , P v,t are wind power output and photovoltaic output at time t respectively; P gi,t is the output of the i-th thermal power unit; P n,t is the net output of the carbon capture power plant; P idr,t is the load reduced by the system IDR at time t; P se,t is the pumped power of the pumped storage unit at time t; N g is the number of conventional thermal power plants; ∑ represents the summation symbol.

[0229] (5) DC power flow constraints:

[0230]

[0231] In formula (28): t is the time; N G 、N L are the number of generator nodes and the number of load nodes respectively; P i,t , P d,t are the output of the generator at node i and the load demand at node j at time t; P l,s,t is the power flow of line s at time t; Plmax,s is the maximum transmission power of line s; G x-i , G x-j are the power transmission distribution factors of generator node i and load node j to line x respectively; ∑ represents the summation symbol.

[0232] (6) Flexibility constraints:

[0233] The flexibility constraint is divided into flexibility resource constraint and line transmission flexibility constraint. The line transmission flexibility constraint is expressed by formula (29):

[0234]

[0235] In formula (29), pr{·} is the probability of an event occurring; t is the time; and are the downward and upward transmission flexibility margins of line s at time t, respectively; and are the downward and upward resource flexibility margins of the system at time t, respectively; The confidence level for the line transmission flexibility constraint.

[0236] When the line power flow direction is opposite to the line transmission flexibility demand direction, the above formula (29) As shown in formula (30):

[0237]

[0238] In formula (30), |·| is the absolute value function; t is the time; and are the downward and upward transmission flexibility margins of line s at time t, respectively; P l,s,t is the power flow of line s at time t; P lmax,s is the maximum transmission power of line s; are the flexibility upward and downward transmission requirements of line s at time t, respectively.

[0239] When the line power flow direction and the line transmission flexibility demand direction are the same, the above formula (29) As shown in formula (31):

[0240]

[0241] In formula (31): |·| is the absolute value function; t is the time; and are the downward and upward transmission flexibility margins of line s at time t, respectively; P l,s,t is the power flow of line s at time t; P lmax,s is the maximum transmission power of line s; are the flexibility upward and downward transmission requirements of line s at time t, respectively.

[0242] The line transmission flexibility constraint is expressed by equation (32):

[0243]

[0244] In formula (32), pr{·} is the probability of an event occurring; t is the time; and are the downward and upward resource flexibility margins of the system at time t, respectively; The confidence level for the line transmission flexibility constraint.

[0245] In the above formula (32), and They are shown in the following formula (33):

[0246]

[0247] In formula (33): and They are the downward and upward resource flexibility margins of the system at time t respectively; They are the upward and downward flexibility supply of thermal power units at time t respectively; They are the upward and downward flexibility supply of the i-th carbon capture unit at time t, respectively; They are the upward and downward flexible supply of the pumped storage unit at time t; They are the upward and downward flexibility supply of IDR of node i at time t; are the upward and downward flexibility requirements of node i at time t; N G 、N L , N are the number of generator nodes, the number of load nodes and the total number of nodes respectively.

[0248] The technical effects of the present invention will be further illustrated by examples below:

[0249] The present invention uses an improved IEEE-30 node system for simulation verification. The system includes 4 thermal power units. The system wiring diagram is as follows: Figure 1 As shown. Node 5 is connected to a 120MW wind turbine, node 9 is connected to a 60MW photovoltaic unit, and a pumped storage unit is connected to node 5 with a capacity of 50MW. G1 is a carbon capture unit. The confidence level is 0.9, and the flue gas diversion ratio limit is 0.9.

[0250] In order to verify the effectiveness of the scheduling model, four scheduling schemes are used for comparison based on the above example.

[0251] Option 1: Without considering demand response, the carbon capture power plant is dispatched with the pumped storage unit;

[0252] Option 2: Pumped storage is not considered, and demand response and pumped storage units are dispatched;

[0253] Option 3: No carbon capture power plant is considered, and demand response and pumped storage units are dispatched;

[0254] Option 4: Demand response, carbon capture power plants and pumped storage units are dispatched.

[0255] Figure 5 The DR optimized curve and electricity prices for each period are given in Figure 5 It can be seen that price-based demand response (PDR) has good peak-shaving and valley-filling characteristics. By increasing the electricity price during peak load periods and reducing the electricity price during low load periods, the load of a cycle is shifted, the volatility of the load is reduced, and the system is enabled to better absorb wind and solar power.

[0256] Table 1 shows the dispatch results under the four schemes. From the data in Table 1, it can be seen that scheme 1 does not consider demand response, and the total cost and carbon emissions are $202686.74 and 4723.19t respectively, and the amount of wind and solar power abandoned is 8.50MW; scheme 2 does not consider pumped storage, resulting in more output of thermal power units, and the emission increased by 79.41t compared with scheme 1. At the same time, IDR participates in the dispatch, and the IDR cost increases by $2834.06, the total cost increases by $1677.21, and the amount of wind and solar power abandoned also increases by 23.61MW, indicating that compared with demand response, pumped storage can better improve the economy and low carbon of the system, and also promote the system to better absorb wind and solar power; scheme 3 does not consider carbon capture power plants, and the total cost increases by 18. 87%, 17.32%, carbon emissions increased by 55.23%, 52.69% respectively, the amount of wind and solar curtailment increased by 55.65% compared with Scheme 1, but decreased by 40.30% compared with Scheme 2. Overall, the economy and low carbon performance are not as good as the first two schemes, and the effect of promoting the wind and solar consumption of the system is also average; Scheme 4 combines the above factors, through the processing of PDR, transfers peak load to valley load, reduces the net load trough difference, and cuts peaks and fills valleys; the introduction of pumped storage reduces the output of thermal power units on the one hand, and better promotes the consumption of wind and solar on the other hand; the introduction of IDR further reduces the operating cost of thermal power units and reduces carbon dioxide emissions. The total cost and carbon emissions of Scheme 4 are reduced by $563.88 and 18.28t respectively compared with the minimum values ​​of the first three schemes, and the amount of wind and solar curtailment is reduced to 1.39MW. Thus, the advantages of this dispatching model are verified.

[0257] Table 1 Scheduling costs of various schemes

[0258]

[0259] The unit output under each scheme is as follows Figure 6-Figure 9 As shown:

[0260] Figure 6 and Fig. 9 In contrast, in Scheme 4, the pumped storage units and IDR replaced part of the thermal power output at 14:00 and 18:00 respectively. At 11:00, since PDR shifted part of the load to other time periods, the system was able to absorb more wind and solar power while meeting the flexibility constraints. Figure 7 and Fig. 9 In contrast, without the participation of carbon capture power plants, conventional thermal power units have poor low-carbon performance, so pumped storage serves as a power source for more periods of time. Figure 8 and Fig. 9 In contrast, without the participation of pumped-storage units, wind and solar power abandonment occurred in the 0-5 period, 16-17 period and 24:00, and thermal power output also increased significantly.

[0261] The increase in confidence level is an improvement in the requirements for system flexibility. The scheduling results under different confidence levels are compared and a suitable confidence interval is selected. The results are shown in Table 2:

[0262] Table 2 Comparison of results at different confidence levels

[0263]

[0264] From the results in Table 2, it can be seen that as the confidence level increases, within the confidence interval of 0.6 to 0.85, the operating cost and carbon emissions of the system increase accordingly, and both wind and solar are fully absorbed. However, when the confidence level increases to 0.9 and above, the phenomenon of wind and solar abandonment begins to appear. This is because the flexibility demand of the system also increases with the increase of the confidence level, and higher requirements are placed on the dispatching capacity of the unit and the transmission capacity of the line. When the confidence level increases from 0.7 to 0.9, the operating costs increase by $96.52, $591.16, and $353.7, respectively. At the same time, carbon emissions increase by 27.74t, 113.61t, and 0.4t. Therefore, the optimal confidence level can be selected between 0.7 and 0.85. Within this range, the economy and low carbon nature of the system operation can be guaranteed while ensuring a certain flexibility of the system.

[0265] When the system contains other flexible resources, the carbon capture unit can adjust the carbon capture energy consumption at any time according to the load demand, thereby minimizing carbon emissions and reducing economic costs. Fig.10The carbon capture energy consumption of the carbon capture unit under the three schemes is shown. It can be seen from the comparison between Scheme 4 and Scheme 1 that Scheme 4 includes demand response. In the 0-8 period, PDR makes the load in this period higher than Scheme 1. Although IDR replaces part of the unit output, the overall carbon capture energy consumption is low, so that the net output can meet the load demand. In the 9-15 period, PDR makes the load in this period lower than Scheme 1, the carbon capture energy consumption increases, and the net output of the unit is reduced. Scheme 4 is compared with Scheme 2. Scheme 2 does not include pumped storage. In the 0-8 period, the net output of the carbon capture unit needs to be reduced, that is, the carbon capture energy consumption is increased, so that the system can absorb as much wind and solar power as possible, but the phenomenon of wind and solar power abandonment still occurs in this period. In the 9-15 period, there is no pumped storage unit to replace the thermal power output, forcing the net output of the carbon capture unit to increase and the carbon capture energy consumption to decrease.

Claims

1. Two-stage dispatch method for carbon capture-wind-solar-thermal-storage combined system considering demand response, Features The following steps are involved: Step 1: Analyze the operating characteristics of the carbon capture unit, pumped storage unit and demand response unit during peak and valley load periods; Step 2: Based on the consideration of the line's flexible scheduling constraints, a two-stage low-carbon flexible scheduling method is proposed: In the first stage, through load forecasting, photovoltaic and wind power output forecasting results, combined with the setting of time-of-use electricity prices, PDR is used to minimize the net load fluctuation of the system in each period, and the load curve optimized by PDR is obtained; In the second stage, the PDR-optimized load obtained in the first stage is used in combination with carbon capture units, pumped storage units, and IDR, while considering line transmission flexibility constraints to obtain a dispatch plan with the optimal cost.

2. According to the two-stage scheduling method of the carbon capture-wind-solar-thermal-storage combined system considering demand response as described in claim 1, Features: In step 1, the net output analysis of the carbon capture unit with comprehensive and flexible operation is as follows: The net output of the carbon capture power plant is equal to the total output minus the total carbon capture energy consumption. The power relationship of the carbon capture power plant is shown in formula (1): In formula (1): P g represents the total output of the carbon capture power plant; P n represents the net output of the carbon capture power plant; P o represents the operating energy consumption of the carbon capture power plant; P f represents the fixed energy consumption of the carbon capture power plant; λ c Indicates the unit CO captured by the carbon capture plant 2 Energy consumption required; E e Indicates that the power plant produces CO 2 The total mass of c Indicates the maximum operating coefficient of the compressor and regeneration tower; P gmax represents the maximum output of the carbon capture power plant; Carbon capture power plants capture CO 2 The quality of c represents the carbon capture efficiency of the carbon capture power plant; δ c represents the flue gas split ratio of the carbon capture power plant; e c is the carbon emission intensity; The CO2 to be captured in the solution storage of the carbon capture power plant 2 quality; According to formula (1), the minimum and maximum net output expressions of the carbon capture power plant are shown in formula (2): In formula (2): P omax represents the maximum operating energy consumption of the carbon capture power plant; P gmax and P gmin Respectively represent the maximum and minimum output of the carbon capture power plant; P f represents the fixed energy consumption of the carbon capture power plant; P nmax and P nmin They represent the maximum and minimum output of the carbon capture power plant respectively; The maximum operating energy consumption of the carbon capture power plant is calculated as shown in formula (3): P omax =c c e c b c P gmax (3); In formula (3): β c Represents the carbon capture efficiency of the carbon capture power plant.

3. According to the two-stage scheduling method of the carbon capture-wind-solar-thermal-storage combined system considering demand response as described in claim 2, Features: PDR guides users' electricity consumption behavior and reduces load fluctuations by adopting a time-of-use electricity price strategy. The relationship between electricity prices and load changes in each period is expressed by formula (4): In formula (4): p , g , f are the load change rates during the flat, trough and peak periods respectively; D p , D g , D f are the time-of-use electricity prices during flat, trough and peak periods respectively; E is the demand elasticity matrix of PDR.

4. According to the two-stage scheduling method of the carbon capture-wind-solar-thermal-storage combined system considering demand response as described in claim 3, Features: In step 1, pumped storage can accomplish the task of peak load shaving and valley filling to a high degree. It has two working states during operation and needs to satisfy the working condition conversion constraint as shown in formula (5): In formula (5): t is the time; is the operating state variable of the pumped storage unit at time t. If it is in pumping condition, then is 1, is 0; if it is in power generation condition, is 0, is 1; is the operating state variable of the pumped storage unit at time t-1; T is the dispatching period; Pumped storage meets the power generation constraint and reservoir capacity constraint under both operating conditions, as shown in formula (6): In formula (6): t is the time; P se,t is the pumped power of the pumped storage unit at time t; P psmax is the maximum power of the pumped storage unit; is the water capacity of the reservoir at time t; is the water capacity of the reservoir at time t-1; are the initial water capacity of the upper reservoir and the water capacity at the end of dispatch, respectively; η psc , η psg are the water conversion coefficient of the pumped storage unit in the pumping state and the power conversion coefficient in the power generation state; P psc,t , P psg,t are the pumping and generating power of the pumped storage unit at time t, respectively; are the minimum and maximum water capacities of the upper reservoir respectively.

5. According to the two-stage scheduling method of the carbon capture-wind-solar-thermal-storage combined system considering demand response as described in claim 4, Features: In step 1, the operating characteristics of the combined operation of the carbon capture unit, the pumped storage unit and the demand response are analyzed as follows: On the power supply side, the pumped storage unit and the carbon capture unit are operated together. When the load is peak, the net output of the unit is increased by reducing the energy consumption of the carbon capture unit, and the pumped storage unit is used to generate electricity, absorbing as much new energy output as possible, reducing the output of thermal power units, and thus reducing carbon emissions; when the load is low, the carbon capture energy consumption of the carbon capture unit is increased to reduce the carbon emissions of the carbon capture unit, and the pumped storage unit is used to pump water to fill the load valley; On the load side, PDR is used to transfer part of the load during peak hours to off-peak hours.

6. According to the two-stage scheduling method of the carbon capture-wind-solar-thermal-storage combined system considering demand response as described in claim 1, Features: In step 2, the node flexibility demand comes from the fluctuation of net load and the forecast error of wind, solar and load; the net load and flexibility demand of the node at each moment are shown in formula (7): In formula (7): F de,i,t is the flexibility requirement of node i at time t; P d,i,t is the load forecast value of node i at time t; P net,i,t is the net load demand of node i at time t; P wpre,i,t , P vpre,i,t are the predicted wind power and photovoltaic output at node i at time t; △P l,i,t , △P wpre,i,t , △P vpre,i,t are the prediction errors of the load and wind / solar output of node i at time t; △P net,i,t is the net load error of node i at time t; P net,i,t+1 is the net load demand of node i at time t+1; The node flexibility demand is directional. The net load demand of each node obtained by equation (7) can be used to calculate the upward and downward flexibility demands of the corresponding node, as shown in equations (8) and (9): In formula (8) and formula (9): are the upward and downward flexibility requirements of node i at time t; F de,i,t is the flexibility requirement of node i at time t; The flexibility requirements of each node obtained by equations (8) and (9) are used to obtain the line flexibility transmission power requirement of each line using the power transmission distribution factor (PTDF). The calculation process is shown in equation (10): In formula (10): are the upward and downward transmission requirements of line l at time t respectively; G i,l is the power transfer distribution factor of node i to line l; are the upward and downward flexibility requirements of node i at time t respectively; ∑ represents the summation sign; L is the total number of lines.

7. The two-stage dispatching method of the carbon capture-wind-solar-thermal-storage combined system considering demand response according to claim 6, Features: The two-stage low-carbon flexible scheduling method is as follows: In the first stage, the PDR is used to process the load forecast and wind and solar output forecast results to obtain the optimized load curve. The minimum net load square error is taken as the objective function 1, as shown in formula (11): In formula (11): f 1 is the objective function 1; t is the time; P net,t is the net load at time t; P net,t+1 is the net load at time t+1; ∑(·) is the summation function; min(·) is the minimum function; In the second stage, the optimal scheduling scheme is obtained by taking objective function 2 as the minimum total cost; The objective function 2 is shown in formula (12): f 2 =min(C M +C G +C R +C Q +C S +C IDR ) (12); In formula (12): f 2 represents the objective function 2; C M represents the coal consumption cost of thermal power units; C G represents the start-up and shutdown cost of thermal power units; C R represents the solution loss cost of the carbon capture unit; C Q C represents the penalty cost for abandoning wind and solar power; S represents the operating cost of the pumped storage unit; C IDR represents the call cost of IDR; min(·) represents the minimum function.

8. The two-stage dispatching method of the carbon capture-wind-solar-thermal-storage combined system considering demand response according to claim 7, Features: Coal consumption cost of thermal power units C M , as shown in formula (16): In formula (16): C M is the coal consumption cost of thermal power units; a i , bi , ci are the coal consumption coefficients of the i-th thermal power plant; P gi,t is the total output of the i-th thermal power plant at time t; N g is the number of conventional thermal power plants; N g is the number of conventional thermal power plants; Start-up and shutdown cost of thermal power units C G , as shown in formula (17): In formula (17): C G is the start-up and shutdown cost of thermal power units; Hu i 、Hd i are the start-up and shutdown costs of the i-th thermal power unit; u gi,t is the operating state variable of the i-th thermal power unit at time t. When it is 1, it means that the unit is running at this time; When it is 0, it means the unit stops running; gi,t-1 The operating state variables of the i-th thermal power unit at time t-1; Solution loss cost of carbon capture power plant C R , as shown in formula (18): C R =Q r ψE cap,t (18); In formula (18): t is the time; C R is the solution loss cost of the carbon capture power plant; Q r is the cost factor of the storage solution for the carbon capture unit; ψ is the solution loss coefficient; E cap,t is the CO captured by the carbon capture unit at time t 2 quality; Penalty cost for wind and solar curtailment C Q , as shown in formula (19): In formula (19): C Q Penalty cost for wind and solar curtailment; K cur P is the penalty coefficient for wind and solar power abandonment; wcur , P vcur are the wind curtailment and solar curtailment at time t respectively; Operation cost of pumped storage unit C S , as shown in formula (20): In formula (20): C S is the operating cost of the pumped storage unit; K psg , K psc are the start-up and shutdown costs of the pumped storage unit for power generation and water pumping, respectively; are the pumping and power generation state variables of the pumped storage unit at time t respectively; are the pumping and power generation state variables of the pumped storage unit at time t-1 respectively; IDR call cost C IDR , as shown in formula (21): In formula (21): C IDR is the IDR call cost; P idr,t K is the load reduced by the system IDR at time t; idr is the call cost coefficient of IDR; Conventional thermal power units need to meet the output constraints, as shown in formula (22): u gi,t Q gmin,i ≤P gi,t ≤u gi,t Q gmax,i (22); In formula (22): u gi,t is the operating state variable of the i-th thermal power unit at time t. When it is 1, it means that the unit is running at this time; When it is 0, it means the unit stops running; P gmin,i , P gmax,i are the minimum and maximum output of the i-th thermal power unit at time t; P gi,t is the output of the i-th thermal power unit at time t; Conventional thermal power units need to meet the ramp constraints, as shown in formula (23): In formula (23): P gi,t is the output of the i-th thermal power unit at time t; u gi,t is the operating state variable of the i-th thermal power unit at time t. When it is 1, it means that the unit is running at this time; When it is 0, it means the unit stops running; P gu,i , P gd,i are the upward and downward climbing powers of the i-th thermal power unit respectively; P gi,t-1 is the output of the i-th thermal power unit at time t-1; u gi,t-1 The operating state variables of the i-th thermal power unit at time t-1; The CO extracted from the solution storage 2 Stored in an amine solution, CO is described by equation (24) 2 Relationship between mass and solution volume: In formula (24): V ci,t For the j The storage installed in a carbon capture power plant releases CO at time t 2 The volume of solution consumed; θ is the reduction of CO in the process from rich solution to lean solution 2 Quantity; ε r is the concentration of the solution in the reservoir; Provide CO to the storage tank of the i-th carbon capture power plant at time t 2 The quality of r is the concentration of the solution in the storage; M mea , MEA and CO 2 The molar mass of When the carbon capture unit is in operation, the volume of the remaining solution in the storage must also be considered, and its constraint is shown in equation (25): In formula (25): V pj,t 、V fj,t Respectively j The remaining volume of the lean solution and the rich solution in the solution storage of a carbon capture power plant at time t; V smax,j For the j The maximum capacity of the solution storage in a carbon capture power plant; V cj,t For the j The storage installed in a carbon capture power plant releases CO at time t 2 The volume of solution consumed; V pj,t-1 、V fj,t-1 Respectively j The residual volume of the solution in the lean liquid tank and the rich liquid tank of a carbon capture power plant at time t-1; When the carbon capture power plant is operated according to the constraint of formula (25), in order to enable the system to be normally dispatched, the volume of the solution should also satisfy formula (26): In formula (26): V pj,0 、V pj,24 Respectively j The initial volume of the lean liquid tank in a carbon capture power plant and the remaining volume at the end of the dispatch; V fj,0 、V pj,24 Respectively j The initial volume of the rich liquid tank in each carbon capture plant and the remaining volume at the end of dispatch; The entire system needs to meet the unit output power balance constraint when it is running, as shown in formula (27): In formula (27): P lpdr,t is the load after PDR of the system at time t; P w,t , P v,t are wind power output and photovoltaic output at time t respectively; P gi,t is the output of the i-th thermal power unit; P n,t is the net output of the carbon capture power plant; P idr,t is the load reduced by the system IDR at time t; P se,t is the pumped power of the pumped storage unit at time t; N g is the number of conventional thermal power plants; DC power flow refers to the calculation of power flow between nodes in the power system through the DC power flow equation to achieve system balance and stable operation; it is constrained by equation (28): In formula (28): N G 、N L are the number of generator nodes and the number of load nodes respectively; P i,t , P d,t are the output of the generator at node i and the load demand at node j at time t; P l,s,t is the power flow of line s at time t; P lmax,s is the maximum transmission power of line s; G x-i , G x-j are generator node i and load node i respectively j Power transfer distribution factor for line x.

9. The two-stage dispatching method of the carbon capture-wind-solar-thermal-storage combined system considering demand response according to claim 8, Features: Considering the impact of line transmission capacity on system flexibility scheduling, the line transmission capacity is judged by whether it meets the flexibility requirements of each node mapped to the sum of the requirements of each branch. When discussing flexibility requirements, it is generally divided into two directions: upward and downward. The transmission flexibility constraint of the line is shown in formula (29): In formula (29): pr{·} is the probability of an event occurring; and are the downward and upward transmission flexibility margins of line s at time t, respectively; and are the downward and upward resource flexibility margins of the system at time t, respectively; confidence levels for line transmission flexibility constraints; When the line power flow direction is opposite to the line transmission flexibility demand direction, the above formula (29) As shown in formula (30): In formula (30): |·| is the absolute value function; and are the downward and upward transmission flexibility margins of line s at time t, respectively; P l,s,t is the power flow of line s at time t; P lmax,s is the maximum transmission power of line s; are the flexibility upward and downward transmission requirements of line s at time t, respectively; When the line power flow direction and the line transmission flexibility demand direction are the same, the above formula (29) As shown in formula (31): In formula (31): and are the downward and upward transmission flexibility margins of line s at time t, respectively; P l,s,t is the power flow of line s at time t; P lmax,s is the maximum transmission power of line s; are the flexibility upward and downward transmission requirements of line s at time t, respectively; Resource flexibility constraint, as shown in formula (32): In formula (32): and are the downward and upward resource flexibility margins of the system at time t, respectively; In the above formula (32), and They are shown in the following formula (33): In formula (33): and They are the downward and upward resource flexibility margins of the system at time t respectively; They are the upward and downward flexibility supply of thermal power units at time t respectively; They are the upward and downward flexibility supply of the i-th carbon capture unit at time t, respectively; They are the upward and downward flexible supply of the pumped storage unit at time t; They are the upward and downward flexibility supply of IDR of node i at time t; are the upward and downward flexibility requirements of node i at time t; N G 、N L , N are the number of generator nodes, the number of load nodes and the total number of nodes respectively.

10. The two-stage dispatching method of the carbon capture-wind-solar-thermal-storage combined system considering demand response according to claim 1, Features: It also includes step 3: simulating the scheduling results under various schemes in the improved IEEE30-node system; Carbon capture units and pumped storage units are added to the improved IEEE30-node system, and four different schemes are set up to verify the dispatch effect after considering demand response and the impact of line transmission flexibility constraints on the dispatch results.

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