Electric power system multi-stage power supply planning method capable of meeting system flexibility requirement

Abstract

The invention discloses a power system multi-stage power supply planning method meeting system flexibility requirements, and relates to the technical field of power planning. The invention aims to solve the problem that an existing power supply planning method cannot meet the novel development requirement of a power supply structure of a power system. According to the electric power system multi-stage power supply planning method meeting the system flexibility requirement, the carbon emission cost of a traditional generator set and ESSs and the power abandoning penalty cost of a new energy generator set are added into the operation cost of a basic multi-stage power supply planning model; and establishing a multi-stage power supply planning model of the power system considering the flexibility constraint, and performing power supply planning on the power system by using the multi-stage power supply planning model of the power system.

Description

Technical Field

[0001] The invention belongs to the technical field of electric power planning. Background Art

[0002] The grid connection of a high proportion of renewable energy has increased the uncertainty of the operation of the new power system, and put forward new requirements for the economic planning of the system power structure, such as balancing multiple objectives such as improving system flexibility and energy utilization. However, the existing power planning methods are difficult to meet the new development requirements. Therefore, it is necessary to comprehensively consider the volatility and flexibility requirements of the system, and build a multi-stage power planning model for the new power system. Under the premise of ensuring the safety and stability of the system, it is necessary to effectively reduce the system cost, improve the energy utilization rate, meet the low-carbon and environmental protection requirements of the new power system, and achieve the coordinated consideration of multiple objectives. Summary of the invention

[0003] The present invention aims to solve the problem that the existing power supply planning method cannot meet the new development requirements of the power supply structure of the power system, and now provides a multi-stage power supply planning method for the power system that meets the system flexibility requirements.

[0004] A multi-stage power planning method for power systems that meets system flexibility requirements, including:

[0005] The carbon emission costs of traditional generators and ESSs and the power abandonment penalty costs of new energy generators are added to the operating costs of the basic multi-stage power planning model, and a multi-stage power planning model for power systems considering flexibility constraints is established. The power system is planned using this multi-stage power planning model.

[0006] The expression of the multi-stage power supply planning model of the power system considering flexibility constraints is:

[0007]

[0008] Where N is the total number of nodes in the power system, n = 1, 2, ..., N, E new , R new and F new are the sets of newly added ESSs, new energy generators and traditional generators at node n, respectively. new =1,2,...,E new , r new =1,2,...,R new , f new =1,2,...,F new , β f , β r , β e are the investment decision variables for traditional power generation units, new energy power generation units and ESSs, and are the investment costs of traditional generator sets, new energy generator sets and ESSs at node n, respectively, n,f ,I n,r and I n,e are the number of traditional generators, new energy generators and ESSs at node n, is the total operating cost;

[0009] The flexibility constraints include: power system flexibility constraints, traditional generator flexibility constraints and ESSs flexibility constraints;

[0010] The power system flexibility constraint includes a power system primary reserve constraint and a power system secondary reserve constraint;

[0011] The flexibility constraints of the traditional generator set include: primary reserve constraints of the traditional generator set, secondary reserve constraints of the traditional generator set, output constraints of the traditional generator set, climbing capacity constraints of the traditional generator set and minimum operating time constraints of the traditional generator set;

[0012] The ESSs flexibility constraints include: ESSs standby time constraints, ESSs standby charge and discharge power constraints, ESSs standby climbing capability constraints, ESSs charge and discharge power constraints and ESSs climbing capability constraints.

[0013] Furthermore, the expression of the primary reserve constraint of the above power system is:

[0014]

[0015] Where: and are the primary reserves provided by the traditional generator set and ESSs at node n in stage t, is the primary reserve demand at node n in phase t, E and F are the sets of all ESSs and all traditional generators at node n, e = 1, 2, ..., E, f = 1, 2, ..., F;

[0016] The expression of the secondary reserve constraint of the power system is:

[0017]

[0018] Where: R is the set of all renewable energy generators at node n, r = 1, 2, ..., R, and are the upward and downward secondary reserves provided by the traditional generator set at node n in phase t, and are the upward and downward secondary reserves provided by ESSs at node n in phase t, α secis the ratio of the secondary reserve required by the new energy generator to the power generation, P n,t,r is the power generation of the new energy generator set at node n in stage t, is the secondary backup requirement at node n in phase t.

[0019] Furthermore, the expression of the primary reserve constraint of the above traditional generator set is:

[0020]

[0021] Where: M n,t,f is the number of operating units at node n in stage t, The upper limit of primary reserve that each traditional generator set can provide;

[0022] The expression of the secondary reserve constraint of the traditional generator set is:

[0023]

[0024] Where: The upper limit of secondary reserve that each traditional generator set can provide;

[0025] The expression of the output constraint of the traditional generator set is:

[0026]

[0027] Where: P n,t,f is the power generation of the traditional generator set at node n in stage t, and They are the upper and lower limits of the output of traditional generator sets respectively;

[0028] The expression of the traditional generator set climbing ability constraint is:

[0029]

[0030] Where: and are the upward and downward climbing capabilities of traditional generator sets, U n,t,f and D n,t,f are the number of started units and shut down units at node n in stage t respectively;

[0031] The expression of the minimum operating time constraint of the traditional generator set is:

[0032]

[0033] Where: is the total number of traditional generator sets at node n, Δt and Δt′ are the minimum operating and shutdown times of traditional generator sets, respectively.

[0034] Furthermore, the expression of the above ESSs backup time constraint is:

[0035]

[0036] Where: is the minimum secondary reserve that the e-th energy storage device can provide in stage t, δ prim and δ sec are the minimum duration of primary and secondary backup of ESSs, and are the charging efficiency and discharging efficiency of the e-th energy storage device, respectively. and are the minimum and maximum storage capacity of the e-th energy storage device, is the total number of ESSs at node n;

[0037] The expression of the ESSs backup charge and discharge power constraint is:

[0038]

[0039] Where: and are the maximum discharge and charge capacity of the e-th energy storage device, respectively. and are the discharge power and charging power of ESSs at node n in stage t, respectively;

[0040] The expression of the ESSs backup climbing capacity constraint is:

[0041]

[0042] Where: and are the maximum upward and downward climbing capabilities of the e-th energy storage device; Δt prim and Δt sec are the time required for full activation of the primary and secondary backups of ESSs, respectively;

[0043] The expression of ESSs charging and discharging power constraint is:

[0044]

[0045] Where: and are the minimum discharge and charge capacity of the e-th energy storage device, respectively. and are the number of ESSs being discharged and charged at node n in phase t, respectively;

[0046] The expression of ESSs climbing ability constraint is:

[0047]

[0048] Furthermore, the carbon emission cost expressions of the above traditional generators and ESSs are as follows:

[0049]

[0050] Where: G and E are the sets of all generators and ESSs at node n, g = 1, 2, ..., G, e = 1, 2, ..., E, and are the unit carbon emission costs of traditional generators and ESSs, respectively, car is the carbon tax, f and e are the carbon emission factors of traditional power generation units and ESSs, P n,t,f is the power generation of the traditional generator set at node n in stage t, is the discharge power of ESSs at node n in stage t.

[0051] Furthermore, the penalty cost expression for the power abandonment of the above-mentioned new energy generator set is as follows:

[0052]

[0053] Where: R is the set of all renewable energy generators at node n, r = 1, 2, ..., R, is the unit power abandonment penalty cost of the new energy generator set, A n,t,r is the abandoned power of the new energy generator set at node n in stage t, α n,t,r is the power abandonment rate of the new energy generator set at node n in stage t, P n,t,r is the power generation of the new energy generator set at node n in stage t.

[0054] Furthermore, the above basic multi-stage power planning model expression is:

[0055]

[0056] Where: G new and E new are the sets of newly added generators and ESSs at node n, respectively, new =1,2,...,G new , e new =1,2,...,E new , G and E are the sets of all generators and ESSs at node n, g = 1, 2, ..., G, e = 1, 2, ..., E, T is the total number of stages, t = 1, 2, ..., T, βg is the investment decision variable of the generator set, is the investment cost of the new generator set at node n, I n,g is the number of new generators at node n, and are the charging / discharging costs of the generator and ESSs at node n, is the unit startup cost of the generator set, P n,t,g is the charging / discharging power of the generator set at node n in phase t, is the discharge power of ESSs at node n in stage t, is the capacity of the generator set started at node n in phase t;

[0057] The constraints of the basic multi-stage power planning model include: node installed capacity constraints, line power balance constraints, line flow constraints and generator output constraints.

[0058] Furthermore, the expression of the above node installed capacity constraint is:

[0059]

[0060] Where: G old and E old are the sets of original generators and ESSs at node n, g old =1,2,...,G old , e old =1,2,...,E old , O n,g and O n,e are the capacities of the original generators and ESSs at node n, and are the maximum capacities of generator sets and ESSs, respectively, and are the maximum capacities of the generators and ESSs at node n, respectively;

[0061] The expression of the line power balance constraint is:

[0062]

[0063] Where: is the charging power of ESSs at node n in phase t, L and B are the transmission line and transmission line connected to node n, respectively, l = 1, 2, ..., L, b = 1, 2, ..., B, P n,t,l and P n,t,b are the transmission power and power delivered through node n in phase t, respectively, n,t is the power of node n in stage t;

[0064] The expression of the line power flow constraint is:

[0065]

[0066] Where: a is any line, P n,t,a is the power flow of line a in stage t, is the maximum capacity that can be transmitted by line a;

[0067] The expression of the generator set output constraint is:

[0068]

[0069] Furthermore, the above total operating cost The expression is:

[0070]

[0071] Where: T is the total number of stages, t = 1, 2, ..., T, F, R and E are the sets of all traditional generators, all new energy generators and all ESSs at node n, f = 1, 2, ..., F, r = 1, 2, ..., R, e = 1, 2, ..., E, and are the charging / discharging costs of the traditional generator set, new energy generator set and ESSs at node n, respectively, n,t,f and P n,t,r are the charging / discharging power of the traditional generator set and the new energy generator set at node n in stage t, is the discharge power of ESSs at node n in stage t, and are the unit carbon emission costs of traditional generators and ESSs, is the unit startup cost of traditional generator sets, is the capacity of the traditional generator set started at node n in phase t, is the unit power abandonment penalty cost of the new energy generator set, A n,t,r is the amount of power abandoned by the new energy generator set at node n in stage t.

[0072] The purpose of this invention is to design a new multi-stage power planning method for power systems that meets the system flexibility requirements. First, a basic multi-stage power planning model is constructed, and then the carbon emission costs and power abandonment penalty costs of multiple types of energy are integrated, and the system flexibility requirements are considered. A multi-stage power planning model considering flexibility constraints is constructed, which solves the core problem of coordinating multiple objectives such as power economic planning, system flexibility requirements, low-carbon environmental protection requirements, and efficient energy utilization under the new power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 A bar chart of the installed capacity of new units;

[0074] Figure 2 It is the curve diagram of actual output of PVGs;

[0075] Figure 3 This is a graph showing the impact of carbon emission prices on installed capacity;

[0076] Figure 4 The following is a cost comparison chart for each scenario. DETAILED DESCRIPTION

[0077] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0078] Specific implementation method 1: The multi-stage power supply planning method for the power system that meets the system flexibility requirements described in this implementation method includes:

[0079] 1. Build a basic power supply planning model

[0080] The basic multi-stage power planning model can be used to plan the investment of generator sets and energy storage systems (ESSs). The objective function is to minimize the stage investment and operating costs, which is expressed as:

[0081]

[0082] Where: N is the total number of nodes in the power system, n = 1, 2, ..., N; G new and E new are the sets of newly added generators and ESSs at node n, g new =1,2,...,G new , e new =1,2,...,E new β g and β e are the investment decision variables for generator sets and ESSs, respectively, with values ​​of 1 or 0, indicating the decision to invest or not; and are the investment costs of the new generators and ESSs at node n, respectively; I n,g and I n,eare the number of newly added generators and ESSs at node n, respectively; T is the total number of stages, t=1,2,...,T; G and E are the sets of all generators and ESSs at node n, g=1,2,...,G, e=1,2,...,E, respectively; and are the charging / discharging costs of the generator and ESSs at node n, respectively; P n,t,g is the charging / discharging power of the generator set at node n in phase t, is the discharge power of ESSs at node n in stage t; is the unit startup cost of the generator set; is the capacity of the generator set started at node n in phase t.

[0083] The basic power planning model meets the following constraints:

[0084] 1) Node installed capacity constraints:

[0085]

[0086] Where: G old and E old are the sets of original generators and ESSs at node n, g old =1,2,...,G old , e old =1,2,...,E old ;O n,g and O n,e are the capacities of the original generators and ESSs at node n, respectively; and is the maximum capacity of the generator sets and ESSs; and are the maximum capacities of the generator sets and ESSs at node n, respectively.

[0087] 2) Line power balance constraints:

[0088]

[0089] Where: is the charging power of ESSs at node n in phase t; L and B are the transmission line and transmission line connected to node n, respectively, l = 1, 2, ..., L, b = 1, 2, ..., B; P n,t,l and P n,t,b are the transmission power and power delivered through node n in phase t respectively; P n,t is the power of node n in stage t.

[0090] 3) Line flow constraints:

[0091]

[0092] Where: a is any line, P n,t,a is the power flow of line a in stage t, is the maximum capacity that line a can transmit.

[0093] 4) Generator output constraints:

[0094]

[0095] 2. Calculating the carbon emission costs of traditional generators and ESSs

[0096]

[0097] Where: and are the unit carbon emission costs of traditional generators and ESSs respectively; P n,t,f is the power generation of the traditional generator set at node n in stage t; γ car is the carbon tax; f and e are the carbon emission factors of traditional power generating units and ESSs, respectively.

[0098] 3. Calculate the penalty cost of power abandonment of new energy generators

[0099]

[0100] Where: R is the set of all renewable energy generators at node n, r = 1, 2, ..., R; A is the penalty cost of unit power abandonment of new energy generators; n,t,r is the abandoned power of the new energy generator set at node n in stage t; α n,t,r is the power abandonment rate of the new energy generator set at node n in stage t; P n,t,r is the power generation of the new energy generator set at node n in stage t.

[0101] The curtailment penalty cost meets the following constraints:

[0102] 1) Output constraints of new energy generator sets:

[0103]

[0104] Where: and are the maximum capacities of any traditional generator set and new energy generator set respectively, and F is the set of all traditional generator sets at node n.

[0105] 2) Carbon emission constraints:

[0106]

[0107] Where: is the upper limit of carbon emissions at node n in stage t.

[0108] 4. Determining Power System Flexibility Constraints

[0109] 1) Primary backup constraint:

[0110]

[0111] Where: and are the primary reserves (capacity or power) provided by the traditional generators and ESSs at node n in stage t, is the primary backup requirement at node n in phase t.

[0112] 2) Secondary backup constraints:

[0113] To ensure the economical, efficient and stable operation of the system, when the load in the system suddenly increases or the generator set suddenly exits, the system needs to call the upward secondary reserve. On the contrary, when the load suddenly decreases or the generator set outputs too much, the system needs to release the downward secondary reserve. Therefore, the secondary reserve constraint is:

[0114]

[0115] Where: R is the set of all renewable energy generators at node n, r = 1, 2, ..., R, and are the upward and downward secondary reserves provided by the traditional generator set at node n in phase t, and are the upward and downward secondary reserves provided by ESSs at node n in phase t, α sec is the ratio of the secondary reserve required by the new energy generator to the power generation, P n,t,r is the power generation of the new energy generator set at node n in stage t, is the secondary backup requirement at node n in phase t.

[0116] 5. Determine the flexibility constraints of traditional generators

[0117] 1) Unit combination state equation:

[0118]

[0119] Where: M n,t,f , U n,t,f and D n,t,f are the number of running units, starting units and shut-down units at node n in stage t, respectively, n,t-1,fis the number of operating units at node n in stage t-1, is the total number of traditional generator sets at node n.

[0120] 2) Primary backup constraint:

[0121]

[0122] Where: The upper limit of primary backup that each traditional generator set can provide.

[0123] 3) Secondary backup constraints:

[0124]

[0125] Where: The upper limit of secondary backup that each traditional generator set can provide.

[0126] 4) Unit output constraints:

[0127]

[0128] Where: and They are respectively the upper and lower limits of the output of traditional generator sets.

[0129] 5) Climbing ability constraints:

[0130]

[0131] Where: and They are the upward and downward climbing capabilities of traditional generator sets respectively.

[0132] 6) Minimum running time constraint:

[0133]

[0134] Where: Δt and Δt′ are the minimum operation and shutdown time of the traditional generator set respectively.

[0135] VI. Determining ESSs flexibility constraints

[0136] 1) Backup-Duration Constraint:

[0137] It is used to ensure that there is enough energy in the ESSs to provide operating reserve within the required time, and stipulates that at the end of the reserve provision time, the energy must be within the capacity limit of the storage system. It is assumed that the reserve provision time does not exceed the one-hour time step of the model.

[0138] first, Calculate the minimum secondary reserve that the e-th energy storage device (ESSe) can provide at stage t As shown in formula (20):

[0139]

[0140] Where: is the hourly self-discharge rate of ESSe, δ sec is the minimum duration of secondary backup of ESSs, W n,t-1,e is the amount of electricity stored in ESSe during stage t-1, and are the charging efficiency and discharging efficiency of ESSe respectively.

[0141] Next, the backup time of ESSs is constrained:

[0142]

[0143] Where: prim is the minimum duration of primary backup of ESSs, and are the minimum and maximum storage capacity of ESSe, is the total number of ESSs at node n.

[0144] 2) Standby-charge and discharge power constraints:

[0145]

[0146] Where: and are the maximum discharge and charge capacity of ESSe respectively.

[0147] 3) Reserve-climbing capability constraints:

[0148]

[0149] Where: and are the maximum upward and downward climbing capabilities of the e-th energy storage device; Δt prim and Δt sec are the time required for full activation of the primary and secondary backup of ESSs, respectively.

[0150] 4) Charge and discharge power constraints:

[0151]

[0152] Where: and are the minimum discharge and charge capacity of ESSe, and are the numbers of ESSs being discharged and charged at node n in phase t, respectively.

[0153] Constraints on the number of ESSs running in phase t:

[0154]

[0155] The constraint on the number of ESSs operating in phase t is used to avoid simultaneous charging and discharging of ESSs.

[0156] 5) Climbing ability constraints:

[0157]

[0158] 7. Constructing a multi-stage power planning model considering flexibility constraints

[0159] Add the carbon emission costs of traditional generators and ESSs and the penalty costs of renewable energy curtailment to the operating costs of the basic multi-stage power planning model to obtain the total operating cost of the multi-stage power planning model.

[0160]

[0161] Where: is the power generation cost of the traditional generator set at node n, is the unit startup cost of traditional generator sets, is the capacity of the traditional generator set started at node n in phase t, The power generation cost of the new energy generator group at node n.

[0162] The objective function is to minimize the sum of the investment and operating cost of the power supply, as shown in formula (28):

[0163]

[0164] E new , R new and F new are the sets of newly added ESSs, new energy generators and traditional generators at node n, respectively, and e new =1,2,...,E new , r new =1,2,...,R new , f new =1,2,...,F new β f , β r , I n,f ,I n,r ,I n,e

[0165] Example

[0166] The case analysis system selected the NREL 118 bus medium-sized system. The power planning period is set from 2021 to 2030. The overall planning period considers five stages, each of which lasts for two years. The first stage represents the root node, corresponding to the period from 2021 to 2022. The NREL 118 bus system has higher data resolution and higher penetration of new energy sources, which can better simulate the new power system. The power sources of the system are clustered according to the technology and location of the existing generators to form 46 power plants. The power sources that can be invested include 18 fire power units FRUs (Fire Power Units, FRUs), photovoltaic power stations PVGs (Photovoltaic Power Generations, PVGs) and ESSs, assuming a given investment in wind energy. CO2 emission limits are set for each stage, with the goal of reducing emissions by 50% in 2030 relative to the initial year. By setting up three different scenarios, the results of power planning are compared and analyzed. The scenarios are set as Scenario 1: a scenario without considering carbon emission costs, power abandonment penalty costs and system flexibility constraints; Scenario 2: a scenario with carbon emission costs and power abandonment penalty costs, but without considering system flexibility constraints; Scenario 3: the scenario in this article, with carbon emission costs, power abandonment penalty costs and system flexibility constraints.

[0167] The installed capacity of new FRUs, PVGs and ESSs in each stage under the three scenarios is shown in Figure 1 , where stage 1 represents the initial state of the system. Each operation stage is represented by 4 typical weeks to take into account the seasonal changes in load and renewable energy. Figure 1 The comparison results show that in scenario 1, the investment in PVGs increases, while the investment in ESSs does not increase significantly, indicating that the planning model overestimates the system's ability to integrate new energy, and does not fully consider the system's flexibility needs; the power planning scheme obtained by the planning model in scenario 2 is not adaptable to different system development stages. Starting from stage 2, scenario 2 does not consider system flexibility constraints, and its investment capacity is lower than that of scenario 3. Therefore, scenario 3 fully considers the system's flexibility needs and low-carbon development requirements, and is more adaptable under the new power system.

[0168] Taking the average output of PVGs in a typical week as the typical day data, the ratio of the actual output of PVGs to the predicted output in different scenarios is calculated, such as Figure 2 As shown. Figure 2From the simulation results, it can be seen that the actual output of PVGs in scenario 1 is not ideal. Under the condition of sufficient sunlight at noon, the actual output is only 50% of the predicted value; the actual output of PVGs in scenario 2 is better than that in scenario 1, and the maximum ratio can reach 60%; the actual output of PVGs in scenario 3 is the best, higher than other scenarios in all time periods, and its actual output can reach 80% of the predicted value when the average is calculated, which greatly improves the energy availability.

[0169] The impact of carbon emission prices on installed capacity is calculated in each scenario. Since scenario 1 is not affected by carbon emission prices, its installed capacity can be set as the standard value. The comparison between the installed capacity of each scenario and the standard capacity value is shown in the following figure. Figure 3 As shown. Figure 3 From the installed capacity of Scenario 2 and Scenario 3, it can be seen that the installed capacities of FRUs, PVGs and ESSs in Scenario 2 and Scenario 3 are affected to varying degrees by the carbon emission price, and the impact is greater in Scenario 3. Therefore, the planning model in Scenario 3 is more in line with the requirements of low-carbon development of the new power system.

[0170] The planning cost comparison under each scenario is as follows: Figure 4 As shown. Figure 4 From the cost comparison of each scenario, we can see that the total system cost of scenario 1 is nearly 50% higher than that of scenario 3; the system cost of scenario 2 is about 10% higher than that of scenario 3, and the operating cost is nearly 2 billion yuan higher. Therefore, the total cost of the power planning model under scenario 3 is lower. The carbon emission cost of scenario 1 is nearly 100% higher than that of scenario 3, and the carbon emission cost of scenario 2 is about 50% higher than that of scenario 3. The carbon emission cost of the power planning model under scenario 3 is lower, which can basically fully meet the load demand, the system redundancy and flexibility are good, and the utilization rate of new energy is greatly improved.

[0171] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A multi-stage power supply planning method for a power system that meets system flexibility requirements, characterized in that: include: The carbon emission costs of traditional generators and ESSs and the power abandonment penalty costs of new energy generators are added to the operating costs of the basic multi-stage power planning model, and a multi-stage power planning model for power systems considering flexibility constraints is established. The power system is planned using this multi-stage power planning model. The expression of the multi-stage power supply planning model of the power system considering flexibility constraints is: Where N is the total number of nodes in the power system, n = 1, 2, ..., N, E new , R new and F new are the sets of newly added ESSs, new energy generators and traditional generators at node n, respectively. new =1,2,...,E new , r new =1,2,...,R new , f new =1,2,...,F new , β f , β r , β e are the investment decision variables for traditional power generation units, new energy power generation units and ESSs, and are the investment costs of traditional generator sets, new energy generator sets and ESSs at node n, respectively, n,f ,I n,r and I n,e are the number of traditional generators, new energy generators and ESSs at node n, is the total operating cost; The flexibility constraints include: power system flexibility constraints, traditional generator flexibility constraints and ESSs flexibility constraints; The power system flexibility constraint includes a power system primary reserve constraint and a power system secondary reserve constraint; The flexibility constraints of the traditional generator set include: primary reserve constraints of the traditional generator set, secondary reserve constraints of the traditional generator set, output constraints of the traditional generator set, climbing capacity constraints of the traditional generator set and minimum operating time constraints of the traditional generator set; The ESSs flexibility constraints include: ESSs standby time constraints, ESSs standby charge and discharge power constraints, ESSs standby climbing capability constraints, ESSs charge and discharge power constraints and ESSs climbing capability constraints.

2. The method for multi-stage power supply planning of a power system that meets the system flexibility requirements according to claim 1 is characterized in that: The expression of the primary reserve constraint of the power system is: Where: and are the primary reserves provided by the traditional generator set and ESSs at node n in stage t, is the primary reserve demand at node n in phase t, E and F are the sets of all ESSs and all traditional generators at node n, e = 1, 2, ..., E, f = 1, 2, ..., F; The expression of the secondary reserve constraint of the power system is: Where: R is the set of all renewable energy generators at node n, r = 1, 2, ..., R, and are the upward and downward secondary reserves provided by the traditional generator set at node n in phase t, and are the upward and downward secondary backups provided by ESSs at node n in phase t, α sec is the ratio of the secondary reserve required by the new energy generator to the power generation, P n,t,r is the power generation of the new energy generator set at node n in stage t, is the secondary backup requirement at node n in phase t.

3. The method for multi-stage power supply planning of a power system that meets the system flexibility requirements according to claim 2 is characterized in that: The expression of the primary reserve constraint of the traditional generator set is: Where: M n,t,f is the number of operating units at node n in stage t, The upper limit of primary reserve that each traditional generator set can provide; The expression of the secondary reserve constraint of the traditional generator set is: Where: The upper limit of secondary reserve that each traditional generator set can provide; The expression of the output constraint of the traditional generator set is: Where: P n,t,f is the power generation of the traditional generator set at node n in stage t, and They are the upper and lower limits of the output of traditional generator sets respectively; The expression of the traditional generator set climbing ability constraint is: Where: and are the upward and downward climbing capabilities of traditional generator sets, U n,t,f and D n,t,f are the number of started units and shut down units at node n in stage t respectively; The expression of the minimum operating time constraint of the traditional generator set is: Where: is the total number of traditional generator sets at node n, Δt and Δt′ are the minimum operating and shutdown times of traditional generator sets, respectively.

4. The method for multi-stage power supply planning of a power system that meets the system flexibility requirements according to claim 3 is characterized in that: The expression of the ESSs backup time constraint is: Where: is the minimum secondary reserve that the e-th energy storage device can provide in stage t, δ prim and δ sec are the minimum duration of primary and secondary backup of ESSs, and are the charging efficiency and discharging efficiency of the e-th energy storage device, respectively. and are the minimum and maximum storage capacity of the e-th energy storage device, is the total number of ESSs at node n; The expression of the ESSs backup charge and discharge power constraint is: Where: and are the maximum discharge and charge capacity of the e-th energy storage device, respectively. and are the discharge power and charging power of ESSs at node n in stage t, respectively; The expression of the ESSs backup climbing capacity constraint is: Where: and are the maximum upward and downward climbing capabilities of the e-th energy storage device; Δt prim and Δt sec are the time required for full activation of the primary and secondary backups of ESSs, respectively; The expression of ESSs charging and discharging power constraint is: Where: and are the minimum discharge and charge capacity of the e-th energy storage device, respectively. and are the number of ESSs being discharged and charged at node n in phase t, respectively; The expression of ESSs climbing ability constraint is:

5. The method for multi-stage power supply planning of an electric power system that meets the system flexibility requirements according to claim 1, 2, 3 or 4, characterized in that: The carbon emission cost expressions of the traditional generator sets and ESSs are as follows: Where: G and E are the sets of all generators and ESSs at node n, g = 1, 2, ..., G, e = 1, 2, ..., E, and are the unit carbon emission costs of traditional generators and ESSs, γ car is the carbon tax, f and e are the carbon emission factors of traditional power generation units and ESSs, P n,t,f is the power generation of the traditional generator set at node n in stage t, is the discharge power of ESSs at node n in stage t.

6. The method for multi-stage power supply planning of an electric power system that meets the system flexibility requirements according to claim 1, 2, 3 or 4, characterized in that: The penalty cost expression of the new energy generator set for power abandonment is as follows: Where: R is the set of all renewable energy generators at node n, r = 1, 2, ..., R, is the unit power abandonment penalty cost of the new energy generator set, A n,t,r is the abandoned power of the new energy generator set at node n in stage t, α n,t,r is the power abandonment rate of the new energy generator set at node n in stage t, P n,t,r is the power generation of the new energy generator set at node n in stage t.

7. The method for multi-stage power supply planning of an electric power system that meets the system flexibility requirements according to claim 1, 2, 3 or 4, characterized in that: The basic multi-stage power planning model expression is: Where: G new and E new are the sets of newly added generators and ESSs at node n, respectively, new =1,2,...,G new , e new =1,2,...,E new , G and E are the sets of all generators and ESSs at node n, g = 1, 2, ..., G, e = 1, 2, ..., E, T is the total number of stages, t = 1, 2, ..., T, β g is the investment decision variable of the generator set, is the investment cost of the new generator set at node n, I n,g is the number of new generators at node n, and are the charging / discharging costs of the generator and ESSs at node n, is the unit startup cost of the generator set, P n,t,g is the charging / discharging power of the generator set at node n in phase t, is the discharge power of ESSs at node n in stage t, is the capacity of the generator set started at node n in phase t; The constraints of the basic multi-stage power planning model include: node installed capacity constraints, line power balance constraints, line flow constraints and generator output constraints.

8. The method for multi-stage power supply planning of a power system that meets system flexibility requirements according to claim 7, characterized in that: The expression of the node installed capacity constraint is: Where: G old and E old are the sets of original generators and ESSs at node n, g old =1,2,...,G old , e old =1,2,...,E old , O n,g and O n,e are the capacities of the original generators and ESSs at node n, and are the maximum capacities of generator sets and ESSs, respectively, and are the maximum capacities of the generators and ESSs at node n, respectively; The expression of the line power balance constraint is: Where: is the charging power of ESSs at node n in phase t, L and B are the transmission line and transmission line connected to node n, respectively, l = 1, 2, ..., L, b = 1, 2, ..., B, P n,t,l and P n,t,b are the transmission power and power delivered through node n in phase t, respectively, n,t is the power of node n in stage t; The expression of the line power flow constraint is: Where: a is any line, P n,t,a is the power flow of line a in stage t, is the maximum capacity that can be transmitted by line a; The expression of the generator set output constraint is:

9. The method for multi-stage power supply planning of a power system that meets system flexibility requirements according to claim 1, characterized in that: The total operating cost The expression is: Where: T is the total number of stages, t = 1, 2, ..., T, F, R and E are the sets of all traditional generators, all new energy generators and all ESSs at node n, f = 1, 2, ..., F, r = 1, 2, ..., R, e = 1, 2, ..., E, and are the charging / discharging costs of the traditional generator set, new energy generator set and ESSs at node n, respectively, n,t,f and P n,t,r are the charging / discharging power of the traditional generator set and the new energy generator set at node n in stage t, is the discharge power of ESSs at node n in stage t, and are the unit carbon emission costs of traditional generators and ESSs, is the unit startup cost of traditional generator sets, is the capacity of the traditional generator set started at node n in phase t, is the unit power abandonment penalty cost of the new energy generator set, A n,t,r is the amount of power abandoned by the new energy generator set at node n in stage t.

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