A power transmission network bi-level planning method and system considering operation flexibility

Abstract

This application provides a two-layer planning method and system for power transmission networks that considers operational flexibility, relating to the field of power system transmission network planning technology. The two-layer planning method constructs a two-layer planning model for the transmission network that considers operational flexibility: the upper-layer model is the decision-making layer for the capacity of newly built generating units and transmission lines, and transmits the decision results to the lower-layer model. The lower-layer model constrains the system's operational flexibility, feeding back load shedding, load loss, and insufficient operational flexibility to the upper-layer model to optimize line capacity and the results of newly built generating units. In this way, the impact of power system operational flexibility on transmission network planning is considered, and line capacity is corrected through load shedding. This ensures the operational flexibility of the power system in transmission network planning under high wind power integration, thereby improving the transmission network's ability to cope with net load fluctuations under high wind power integration.

Description

Technical Field

[0001] This application relates to the field of power system transmission network planning technology, and in particular to a two-level planning method and system for transmission networks that takes into account operational flexibility. Background Technology

[0002] The statements in this section are merely background information related to this application and do not necessarily constitute prior art known to those skilled in the art.

[0003] Transmission network planning is a fundamental component of power systems. A rational and efficient transmission network is crucial for ensuring the balance of power supply and demand and the safe and economical operation of the system. The main objective of transmission network planning is to determine the capacity of transmission lines based on accurate load growth forecasts and the existing transmission network structure within the planning period. This aims to achieve the optimal grid structure and construction capacity, thereby efficiently allocating regional power resources and ensuring the safe, economical, and reliable operation of the power system. Large-scale wind power integration into the transmission network has become a significant trend in power system development. However, the inherent uncertainties of wind power, such as randomness, intermittency, volatility, and uncontrollability, increase the difficulty of transmission network planning. Therefore, establishing a safe, economical, and reliable transmission network planning model is particularly urgent and important while considering the uncertainties brought about by wind power integration.

[0004] The operational flexibility of a power system refers to its ability to cope with uncertain fluctuations in net load over a given time scale, while ensuring active power balance. In other words, over a given time scale, the system's flexibility supply must exceed its flexibility demand. The supply flexibility of conventional thermal power units is achieved by increasing output to provide upward flexibility and decreasing output to provide downward flexibility. Furthermore, the upward and downward adjustment capabilities of conventional thermal power units are constrained by the ramp rate. The widespread adoption of wind power requires the transmission network to continuously improve its operational flexibility to cope with significant changes in net load caused by the randomness and volatility of wind power. If the system's operational flexibility is insufficient, the flexibility supply cannot meet the net load flexibility demand, forcing the system to abandon wind power or cut loads, resulting in economic losses and resource waste. Therefore, ensuring the operational flexibility of the power system in transmission network planning with a high proportion of wind power integration remains a problem that needs to be solved. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a two-tiered planning method and system for transmission networks that considers operational flexibility. This method takes into account the impact of power system operational flexibility on transmission network planning and modifies line capacity through power flow limit adjustments, thereby ensuring power system operational flexibility in transmission network planning under conditions of high wind power integration.

[0006] To achieve the above objectives, this application mainly includes the following aspects:

[0007] In a first aspect, embodiments of this application provide a two-layer planning method for a power transmission network that considers operational flexibility, including:

[0008] A two-layer planning model for the power transmission network considering operational flexibility is constructed. The two-layer planning model includes an upper-layer model and a lower-layer model. The upper-layer model introduces constraints under N-1 contingency scenarios and new construction flexibility resource constraints. The optimization objective is to minimize the sum of transmission line capacity cost, new generator unit investment cost, thermal power unit operating cost, and wind turbine operating cost. The resulting new generator unit and transmission line capacity schemes are then passed to the lower-layer model. The lower-layer model constrains the system's operational flexibility, using the sum of penalty costs as the optimization objective. It determines the load loss, power flow overrun, and operational flexibility overruns (both upward and downward), and feeds these back to the upper-layer model.

[0009] The two-level planning model of the power transmission network is solved to obtain a power transmission network planning scheme that takes into account operational flexibility, which can be used to guide the construction capacity of lines, the construction capacity and location distribution of new thermal power units in the power transmission network.

[0010] In one possible implementation, the constraints of the upper-level model also include node power balance constraints, line transmission capacity constraints, and generator output upper and lower limit constraints.

[0011] In one possible implementation, the penalty costs include underload penalty costs, insufficient operational flexibility penalty costs, and line flow overload penalty costs.

[0012] In one possible implementation, the constraints of the lower-level model include node power balance constraints, line transmission capacity constraints, generator output upper and lower limit constraints, logic constraints, unit minimum operating / outage time constraints, unit ramp rate constraints, load shedding constraints, and insufficient operational flexibility constraints.

[0013] In one possible implementation, the nonlinear term of the operating cost of thermal power units is linearized, and the multiplication of two 0 / 1 variables is transformed without error, converting both the upper-level model and the lower-level model into a mixed-integer linear programming model; the mixed-integer linear programming model is solved alternately to obtain a power transmission network planning scheme that takes into account operational flexibility.

[0014] In one possible implementation, a three-segment linearization method is used to linearize the nonlinear term of the operating cost of thermal power units.

[0015] In one possible implementation, the MILP solver is invoked to alternately solve the upper-level model and the lower-level model until a power grid planning scheme that meets the system's operational flexibility requirements is obtained.

[0016] Secondly, embodiments of this application provide a two-tiered planning system for a power transmission network that considers operational flexibility, comprising:

[0017] The model building module is used to construct a two-layer planning model for the power transmission network that considers operational flexibility. The two-layer planning model includes an upper-layer model and a lower-layer model. The upper-layer model introduces constraints under N-1 contingency scenarios and new construction flexibility resource constraints. The optimization objective is to minimize the sum of transmission line capacity cost, new generator unit investment cost, thermal power unit operating cost, and wind power unit operating cost. This results in a new unit and transmission line capacity scheme, which is then passed to the lower-layer model. The lower-layer model constrains the system's operational flexibility, using the sum of penalty costs as the optimization objective. It determines the load loss, power flow exceeding limits, and operational flexibility overruns and underruns, and feeds these back to the upper-layer model.

[0018] The planning scheme determination module is used to solve the two-level planning model of the power transmission network and obtain a power transmission network planning scheme that takes into account operational flexibility. This scheme is used to guide the construction capacity of lines, the construction capacity of new thermal power units, and their location distribution in the power transmission network.

[0019] Thirdly, embodiments of this application provide a computer device, including: a processor, a memory, and a bus. The memory stores machine-readable instructions executable by the processor. When the computer device is running, the processor communicates with the memory via the bus. When the machine-readable instructions are executed by the processor, they perform the steps of the two-layer planning method for power transmission networks that takes into account operational flexibility, as described in the first aspect and any possible implementation of the first aspect above.

[0020] Fourthly, embodiments of this application provide a computer-readable storage medium storing a computer program, which, when executed by a processor, performs the steps of the two-tiered power grid planning method considering operational flexibility as described in the first aspect and any possible implementation thereof.

[0021] The beneficial effects of this application are:

[0022] (1) By constructing a two-layer planning model for the power grid that takes into account operational flexibility: the upper layer model is the decision layer for the capacity of new generating units and transmission lines, and the decision results are transmitted to the lower layer model. The lower layer model constrains the operational flexibility of the system and feeds back the power flow over-limit, load loss and insufficient operational flexibility to the upper layer model so as to optimize the line capacity and the results of new generating units. This not only takes into account the impact of the power system operational flexibility on the power grid planning, but also corrects the line capacity through the power flow over-limit, so as to ensure the operational flexibility of the power system in the power grid planning under the high proportion of wind power integration, thereby helping to improve the ability of the power grid to cope with net load fluctuations under the high proportion of wind power integration.

[0023] (2) Considering that the effective response range of thermal power unit flexibility is related to the grid structure, the situation of transmission congestion or power flow section limitation will restrict the regulation capacity of the regional power grid. Therefore, the power flow limit is included in the lower-level model to ensure the transferability of power system operation flexibility. The operation flexibility of thermal power unit is combined with the decision of transmission grid line capacity, making the decision result more reasonable.

[0024] (3) The line capacity and newly built thermal power units of the upper-level decision are passed to the lower-level model as parameters. The lower-level model not only considers the insufficient up / down climbing ability of the operation flexibility, but also passes the load loss and power flow over-limit to the upper level. The rich transmission variables improve the reliability of the decision of the two-level planning model and are closer to real life. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0026] Figure 1 This is one of the flowcharts of the two-layer planning method for power transmission networks that takes into account operational flexibility, provided in the embodiments of this application;

[0027] Figure 2 This is the second flowchart of the two-layer planning method for power transmission networks that takes into account operational flexibility, provided in the embodiments of the present invention.

[0028] Figure 3 This is a schematic diagram of the transfer variables between the upper and lower layer models of power transmission network planning provided in the embodiments of this application;

[0029] Figure 4 This is a schematic diagram of piecewise linearization of thermal power unit operating costs provided in the embodiments of this application;

[0030] Figure 5 This is a schematic diagram of the structure of a two-layer planning system for a power grid that takes into account the operational flexibility of the power system, provided in an embodiment of this application.

[0031] Figure 6 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application. Detailed Implementation

[0032] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0033] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0034] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0035] Transmission network planning is a fundamental aspect of power systems. A rational and efficient transmission network is crucial for ensuring power supply and demand balance and the safe and economical operation of the system. Transmission network planning can be defined as follows: within the planning period, based on forecasts of load growth trends and power source construction plans, determining when, where, and how much transmission capacity to expand. This optimizes the existing power network, achieving the optimal grid structure and construction capacity, thereby efficiently allocating regional power resources and meeting the system's requirements for safe, economical, and reliable power transmission. The large-scale integration of wind power into the transmission network, with its inherent randomness and volatility, can cause significant changes in net load, leading to a decrease in system reliability. Therefore, transmission network planning that considers the uncertainties of wind power has become a research hotspot.

[0036] The operational flexibility of a power system refers to its ability to cope with uncertain fluctuations in net load over a given time scale, while ensuring active power balance. In other words, over a given time scale, the system's flexibility supply must exceed its flexibility demand. The ability of thermal power units to adjust their output power within a certain range plays a crucial role in balancing large-scale wind power fluctuations and promoting wind power consumption. Furthermore, considering operational flexibility in transmission network planning allows for a trade-off between economic efficiency and flexibility.

[0037] The economic and reliability objectives of power transmission network planning are contradictory. Due to the order-of-magnitude difference between them, the selection of objective weights is highly subjective. Therefore, bi-level programming theory is introduced into power transmission network planning modeling, placing multiple decision problems within a certain decision hierarchy, with each problem having its own decision variables, objectives, and constraints. Moreover, higher-level decisions influence lower-level decisions, and lower-level decisions are determined by higher-level decisions in selecting decision objectives and solutions, creating a feedback and mutual influence between the upper and lower levels.

[0038] Example 1

[0039] Please see Figure 1 and Figure 2 This application provides a two-layer planning method for power transmission networks that considers operational flexibility, specifically including the following steps:

[0040] S101: Construct a two-layer planning model for the power transmission network that considers operational flexibility. The two-layer planning model includes an upper-layer model and a lower-layer model. The upper-layer model introduces constraints under the N-1 contingency scenario and constraints on new flexible resources. The optimization objective is to minimize the sum of transmission line capacity cost, new generator unit investment cost, thermal power unit operating cost, and wind turbine operating cost. The upper-layer model obtains the capacity schemes for new generator units and transmission lines and transmits them to the lower-layer model. The lower-layer model constrains the system's operational flexibility, with the sum of penalty costs as the optimization objective. It determines the load loss, power flow exceeding limits, and the insufficiency of operational flexibility (both upward and downward), and feeds these back to the upper-layer model.

[0041] In practice, the objective function of the upper-level model is to minimize the sum of the transmission line capacity cost, the investment cost of new generator units, the operating cost of thermal power units, and the operating cost of wind power units.

[0042] (1)

[0043] (2)

[0044] (3)

[0045] (4)

[0046] (5)

[0047] in, The cost of investment in transmission capacity for power lines; Investment cost for newly built generator sets; Operating costs of thermal power units; For wind turbine operating costs; A collection of transmission lines; For the line l Investment cost per unit length and unit capacity; For the line Length; For the line l In the n The transmission capacity of the next generation; For the construction of a new generator set collection; For the construction of new units g Investment costs; For generator The capacity; To indicate the unit g Is this a newly created 0 / 1 variable? To optimize the number of time periods, this embodiment sets it to 24 hours; This is a collection of existing generator sets; For generator sets exist Active power at any given moment; , , Generator sets Cost coefficient item; A collection of wind turbine units; For wind turbine Operating costs; For wind turbine exist Active power at any given moment.

[0048] As an optional implementation, the constraints of the upper-level model include node power balance constraints, line transmission capacity constraints, generator output upper and lower limit constraints, constraints under N-1 contingency scenarios, and new flexible resource constraints. Specifically:

[0049] (1) Node power balance constraints

[0050] (6)

[0051] in, For access nodes A collection of thermal power units; For access nodes A collection of wind farms; For wind farm exist Predicted active power output at any given time; This refers to the set of nodes at the end of the line. For the line exist The flow of the line at any moment; This is the set of nodes for the first segment of the line; For nodes exist Active load at any given moment; The node returned by the lower-level model exist The amount of load loss at any given moment.

[0052] (2) Line transmission capacity constraints

[0053] (7)

[0054] (8)

[0055] (9)

[0056] (10)

[0057] in, Indicates transmission line l The reactance; and They represent the lines respectively. l Two-end nodes i and j exist t Phase angle at any given moment; For power transmission lines l The more limited the power flow is in the (n-1)th lower-level model, the better. ; , Transmission lines l Upper and lower limits of capacity, Set to 0, We set a maximum value to approximate it as follows: .

[0058] (3) Generator output upper and lower limit constraints

[0059] (11)

[0060] (12)

[0061] (13)

[0062] in, Indicates wind turbine w The installed capacity, var w,t Indicates time period t Fluctuations in wind turbine output. This represents the lower limit of the active power output of thermal power units.

[0063] (4) Constraints under N-1 contingency scenarios

[0064] (14)

[0065] (15)

[0066] (16)

[0067] (17)

[0068] (18)

[0069] (19)

[0070] (20)

[0071] Among them, superscript k Indicates anticipated accidentsk Under the following operating conditions, this embodiment only considers the N-1 single line failure as a contingency scenario, i.e., the superscript... k Representing the k A line break occurred.

[0072] (5) Establish new flexibility resource constraints

[0073] (twenty one)

[0074] (twenty two)

[0075] in, and For newly built units g The rate of ascent and descent; Δ R up With Δ R down These represent the insufficient operational flexibility returned by the lower-level model, i.e., the unit's inadequate ability to cope with net load increases and decreases. The above two formulas forcefully ensure that newly built units meet the system's operational flexibility requirements while considering unit start-up and shutdown.

[0076] As an optional implementation, the lower-level model constrains the system's operational flexibility, with the sum of penalty costs as the optimization objective. These penalty costs include the cost of load shedding. Insufficient operational flexibility and penalty costs and the cost of exceeding the limit for line flow The details are as follows:

[0077] (twenty three)

[0078] (twenty four)

[0079] (25)

[0080] (26)

[0081] in, A set of nodes; for The penalty cost coefficient for switching off loads at any time; and These represent the insufficient system operational flexibility resulting from the calculation of operational flexibility in the lower-level transmission network, i.e., the lack of capacity of the generating units to cope with net load climb-up and climb-down. and This represents the penalty coefficient corresponding to insufficient flexibility in climbing up or down. The penalty coefficient for exceeding the line power flow limit; For the line lThe more limited the trend, the more it returns to the upper level as a decision variable at the lower level, influencing the decisions made at the upper level.

[0082] As an optional implementation, the constraints of the lower-level model include node power balance constraints, line transmission capacity constraints, generator output upper and lower limit constraints, logic constraints, minimum unit operation / outage time constraints, unit ramp rate constraints, load shedding constraints, and insufficient operational flexibility constraints. Specifically:

[0083] (1) Node power balance constraints

[0084] (27)

[0085] in, It is a collection of the initially planned generating units and the newly built generating units above.

[0086] (2) Line transmission capacity constraints

[0087] (28)

[0088] (29)

[0089] (3) Generator output upper and lower limit constraints

[0090] (30)

[0091] (31)

[0092] in, To reflect the generator set g Time period t The binary variable for internal start / stop status indicates that the unit is running when its value is 1.

[0093] (5) Unload constraint

[0094] (32)

[0095] (33)

[0096] (6) Insufficient operational flexibility constraint

[0097] (34)

[0098] (35)

[0099] (36)

[0100] (37)

[0101] Expressions (34)-(37) calculate the system flexibility deficiency arising from the operational flexibility calculation of the lower-level transmission network, namely the shortfall in the unit's ability to cope with net load climb-up and climb-down. This constraint is related to the unit output and the load during the load period. t and t-1 It is related to the changes in time. ΔR up and ΔR down These respectively indicate insufficient operational flexibility of the lower-level model returning to the upper-level model, and represent the information transfer between the upper and lower layers.

[0102] (7) Logical variable constraints

[0103] (38)

[0104] (39)

[0105] (40)

[0106] in, and These are the labeling units. exist A 0 / 1 variable indicating whether the time period is started or stopped. Representative unit exist Starts during specific time periods, otherwise does not start. Representative unit exist The system will be shut down during designated times; otherwise, it will remain operational. These are 0 / 1 variables representing the initial operating state of the unit; Indicates the unit The initial operating status is indicated by a positive value, which represents the unit being in operation and the value represents the operating time. A negative value indicates that the unit is out of operation.

[0107] (8) Minimum operating time constraint of the unit

[0108] (41)

[0109] in, Indicates the unit g Minimum runtime after startup.

[0110] (9) Minimum downtime constraint of the unit

[0111] (42)

[0112] in, Indicates the unit g Minimum downtime.

[0113] (10) Unit ramp rate constraint

[0114] (43)

[0115] (44)

[0116] (45)

[0117] (46)

[0118] like Figure 3 As shown in the figure, this embodiment divides the power grid planning into two levels: First, the upper-level model is used to decide on the construction of new generating units to compensate for the insufficient uphill ramping capability of the lower-level model, and at the same time, the line capacity is decided to ensure the smooth transmission of the unit output power on the transmission lines; The lower-level model transmits the load shedding, power flow exceeding the limit, insufficient uphill ramping capability, and insufficient downhill ramping capability to the upper-level model to optimize the decision results. The upper and lower levels alternate calculations until the system meets the operational flexibility requirements, reflecting the interaction and mutual influence of the upper and lower level decisions.

[0119] S102: Solve the two-level planning model of the power transmission network to obtain a power transmission network planning scheme that takes into account operational flexibility, which is used to guide the construction capacity of lines, the construction capacity and location distribution of new thermal power units in the power transmission network.

[0120] As an optional implementation, the nonlinear terms of the thermal power unit operating cost are linearized, and the multiplication of two 0 / 1 variables is transformed without error, converting both the upper and lower level models into mixed-integer linear programming models. The mixed-integer linear programming models are then solved alternately to obtain a transmission network planning scheme that considers operational flexibility. Optionally, a three-piece linearization method is used to linearize the nonlinear terms of the thermal power unit operating cost.

[0121] In practical implementation, the quadratic polynomial of the operating cost of thermal power units can be approximated using piecewise linearization, such as... Figure 4 As shown, a three-part piecewise linear function is used to linearize the nonlinear term of the operating cost of thermal power units.

[0122] A three-piece linear function can be expressed in the following form:

[0123] (47)

[0124] (48)

[0125] (49)

[0126] (50)

[0127] (51)

[0128] (52)

[0129] (53)

[0130] (54)

[0131] (55)

[0132] in, m Index for the number of segments; For the unit g exist t During the period m Segmented active power; For the unit g exist m Maximum active power of each segment; For the unit g exist m Minimum active power in segments; To identify the state of unit g in the m-th segment at time t; For the corresponding unit g Operating costs at the lower limit of output; For the unit g exist m The slope when segmented.

[0133] The error-free method for multiplying two 0 / 1 variables is as follows:

[0134] After performing piecewise linearization on the operating cost of thermal power units, the upper and lower limits of output of newly built generator units will contain 0 / 1 variables multiplied by 0 / 1 variables, which will bring a stronger partial linearization and computational burden to the model. Therefore, the above problem can be transformed into a zero-error numerical linearization form by means of the following method:

[0135] linearization Where x and y are both 0 / 1 variables, they can be transformed according to the method of equation (56):

[0136] (56)

[0137] Therefore, both the upper-level model and the lower-level model are transformed into mixed-integer linear programming models. Furthermore, a MILP solver (such as CPLEX) is called to solve the upper-level model and the lower-level model alternately until a power grid planning scheme that meets the system's operational flexibility requirements is obtained.

[0138] By expressing generator operating costs piecewise linearly, the two-layer transmission network planning model considering operational flexibility is transformed into a mixed-integer linear programming model, and the solution is obtained to obtain a transmission network planning scheme that meets the system's operational flexibility requirements. This approach considers both the impact of power system operational flexibility on transmission network planning and corrects line capacity through power flow limits, thereby improving the rationality of transmission network planning.

[0139] Example 2

[0140] Please see Figure 5 , Figure 5 This is a schematic diagram of the structure of a two-layer planning system for a power transmission network that takes into account operational flexibility, as provided in the embodiments of this application. Figure 5 As shown in the illustration, this application embodiment also provides a two-tiered power grid planning system that considers operational flexibility. The two-tiered power grid planning system 500 includes:

[0141] The model building module 510 is used to construct a two-layer planning model for the transmission network that considers operational flexibility. The two-layer planning model includes an upper-layer model and a lower-layer model. The upper-layer model introduces constraints under the N-1 contingency scenario and constraints on new construction flexibility resources. The optimization objective is to minimize the sum of transmission line capacity cost, new generator unit investment cost, thermal power unit operating cost, and wind power unit operating cost. The upper-layer model obtains the capacity scheme for new generator units and transmission lines and passes it to the lower-layer model. The lower-layer model constrains the system's operational flexibility. The optimization objective is to determine the load loss, power flow overrun, and insufficient upward and downward creepage of operational flexibility. The lower-layer model feeds these constraints back to the upper-layer model.

[0142] The planning scheme determination module 520 is used to solve the two-layer planning model of the power transmission network and obtain a power transmission network planning scheme that takes into account operational flexibility. This scheme is used to guide the construction capacity of lines, the construction capacity of new thermal power units, and their location distribution in the power transmission network.

[0143] Example 3

[0144] Please see Figure 6 , Figure 6 This is a schematic diagram of a computer device according to an embodiment of this application. Figure 6 As shown, the computer device 600 includes a processor 610, a memory 620, and a bus 630.

[0145] The memory 620 stores machine-readable instructions executable by the processor 610. When the computer device 600 is running, the processor 610 communicates with the memory 620 via the bus 630. When the machine-readable instructions are executed by the processor 610, they can perform the operations described above. Figure 1 , Figure 2The steps of the two-layer planning method for the transmission network that considers operational flexibility in the method embodiment shown are specifically implemented in the method embodiment and will not be repeated here.

[0146] Example 4

[0147] Based on the same concept, embodiments of this application also provide a computer-readable storage medium storing a computer program, which, when run by a processor, executes the steps of the two-layer planning method for power transmission networks that considers operational flexibility as described in the above method embodiments.

[0148] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0149] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A power transmission network bi-level planning method considering operational flexibility, characterized in that, include: A two-layer planning model for the power transmission network considering operational flexibility is constructed. The two-layer planning model includes an upper-layer model and a lower-layer model. The upper-layer model introduces constraints under N-1 contingency scenarios and new construction flexibility resource constraints. The optimization objective is to minimize the sum of transmission line capacity cost, new generator unit investment cost, thermal power unit operating cost, and wind turbine operating cost. This results in a new generator unit and transmission line capacity scheme, which is then passed to the lower-layer model. The lower-layer model includes constraints on insufficient operational flexibility. The optimization objective is to determine the load loss, power flow overrun, and insufficient upward and downward operational flexibility, and these are fed back to the upper-layer model. The two-level planning model of the power transmission network is solved to obtain a power transmission network planning scheme that takes into account operational flexibility, which can be used to guide the construction capacity of lines, the construction capacity and location distribution of new thermal power units in the power transmission network.

2. The power transmission network bi-level planning method considering operational flexibility according to claim 1, characterized in that, The constraints of the upper-level model also include node power balance constraints, line transmission capacity constraints, and upper and lower limits of generator output constraints.

3. The power transmission network bi-level planning method considering operational flexibility according to claim 1, characterized in that, The penalty costs include the cost of load depletion, the cost of insufficient operational flexibility, and the cost of exceeding the line power flow limit.

4. The power transmission network bi-level planning method considering operational flexibility according to claim 3, characterized in that, The constraints of the lower-level model also include node power balance constraints, line transmission capacity constraints, generator output upper and lower limit constraints, logic constraints, unit minimum operating / outage time constraints, unit ramp rate constraints, and load shedding constraints.

5. The two-layer planning method for transmission networks considering operational flexibility as described in claim 1, characterized in that, The nonlinear terms of thermal power unit operating costs are linearized, and the multiplication of two 0 / 1 variables is transformed without error, converting both the upper and lower level models into mixed integer linear programming models. The mixed integer linear programming models are solved alternately to obtain a power grid planning scheme that considers operational flexibility.

6. The two-layer planning method for transmission networks considering operational flexibility as described in claim 5, characterized in that, The nonlinear term of the operating cost of thermal power units is linearized using a three-piece linearization method.

7. The two-layer planning method for transmission networks considering operational flexibility as described in claim 5, characterized in that, The MILP solver is invoked to solve the upper-level and lower-level models alternately until a power grid planning scheme that meets the system's operational flexibility requirements is obtained.

8. A two-layer planning system for a power transmission network that considers operational flexibility, characterized in that, include: The model building module is used to construct a two-layer planning model for the power transmission network that considers operational flexibility. The two-layer planning model includes an upper-layer model and a lower-layer model. The upper-layer model introduces constraints under the N-1 contingency scenario and constraints on new construction flexibility resources. The optimization objective is to minimize the sum of transmission line capacity cost, new generator unit investment cost, thermal power unit operating cost, and wind power unit operating cost. This results in a new unit and transmission line capacity scheme, which is then passed to the lower-layer model. The lower-layer model includes constraints on insufficient operational flexibility. The optimization objective is to determine the load loss, power flow overrun, and insufficient upward and downward operational flexibility, and then feeds these back to the upper-layer model. The planning scheme determination module is used to solve the two-level planning model of the power transmission network and obtain a power transmission network planning scheme that takes into account operational flexibility. This scheme is used to guide the construction capacity of lines, the construction capacity of new thermal power units, and their location distribution in the power transmission network.

9. A computer device, characterized in that, include: The computer device includes a processor, a memory, and a bus. The memory stores machine-readable instructions executable by the processor. When the computer device is running, the processor communicates with the memory via the bus. When the machine-readable instructions are executed by the processor, they perform the steps of the two-tiered power grid planning method considering operational flexibility as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, performs the steps of the two-tiered planning method for transmission networks that takes into account operational flexibility as described in any one of claims 1 to 7.

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