Planning method and system for multi-region asynchronously interconnected power grids considering frequency security constraints

Abstract

Provided in the present application are a planning method and system for multi-region asynchronously interconnected power grids considering frequency security constraints. The method comprises: acquiring parameters related to frequency response characteristics and frequency deviations of alternating-current power grids in regions of a power system; on the basis of the parameters related to frequency response characteristics and the frequency deviations of the alternating-current power grids in the regions of the power system, determining frequency security constraints of the alternating-current power grids in the regions under direct-current faults; and with the frequency security constraints of the alternating-current power grids in the regions under direct-current faults as constraint conditions, constructing a direct-current and power supply planning model for multi-region asynchronously interconnected power grids considering the frequency security constraints, and using a GUROBI optimizer to optimize and solve the planning model, so as to obtain a direct-current and power supply planning scheme for the asynchronously interconnected power grids in the regions of the power system. The technical solution provided in the present application can effectively ensure that a direct-current and power supply planning scheme for multi-region asynchronously interconnected power grids under high-penetration renewable energy integration meets frequency security requirements, thereby providing decision-making support for power system planning.

Description

Planning Methods and Systems for Multi-Region Asynchronous Interconnected Power Grids Considering Frequency Security Constraints

[0001] Cross-reference to related applications

[0002] This disclosure claims priority to Chinese Patent Application No. 202411603206.3, filed by Tsinghua University on November 11, 2024, entitled "Multi-region Asynchronous Interconnected Power Grid Planning Method and System Considering Frequency Security Constraints", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of power system planning, and in particular to a planning method and system for multi-region asynchronous interconnected power grids that considers frequency security constraints. Background Technology

[0004] With the development of wind and solar power resources in deserts, Gobi, and arid regions, and the widespread integration of offshore wind power, large-scale long-distance inter-regional power transmission will become an important way to utilize and consume clean energy. Compared with high-voltage AC transmission, high-voltage direct current (HVDC) transmission is less expensive in long-distance, large-capacity transmission scenarios, and its transmission power is controllable. It is currently widely used in clean energy transmission, submarine cable transmission, and asynchronous grid interconnection. For China, the distance between western power generation bases and load centers in the eastern and southern coastal areas is mostly over 1,000 kilometers. HVDC is a more economical and feasible technical route to achieve large-scale, long-distance power transmission. With the widespread application of HVDC technology, some regional power grids have already formed a structure of asynchronous interconnection with external power grids through DC lines.

[0005] As synchronous generators are gradually replaced by a high proportion of new energy sources, the power system inertia is showing a downward trend, leading to a shortage of frequency regulation resources. Under significant active power disturbances, the power system frequency may drop rapidly, causing low-frequency load shedding or even system frequency collapse, seriously threatening the reliability of power supply. For asynchronous interconnected grids, the failure of large-capacity DC transmission lines can have a significant impact on the frequency security of the regional grid. Therefore, the planning of multi-regional asynchronous interconnected grids requires the rational selection of inter-regional DC capacity and the appropriate allocation of power sources and other frequency regulation resources. Regarding planning that considers frequency security constraints, current technologies mainly focus on adding frequency security constraints to models at the operational simulation level, with the planning objects generally being power sources and energy storage. However, current DC line planning primarily focuses on its economic efficiency and operational benefits, neglecting to consider the impact of large-capacity inter-regional DC transmission on the frequency security of the regional grid, resulting in the grid's inability to operate safely and stably. Summary of the Invention

[0006] This application provides a multi-region asynchronous interconnected power grid planning method and system that considers frequency security constraints, so as to at least solve the technical problem that the planning of large-capacity cross-regional DC transmission lines on the frequency security of regional power grids leads to the inability of the power grid to operate safely and stably.

[0007] The first aspect of this application proposes a multi-region asynchronous interconnected power grid planning method considering frequency security constraints, the method comprising:

[0008] Obtain relevant parameters and frequency deviations of the frequency response characteristics of AC power grids in various regions of the power system;

[0009] Based on the relevant parameters of the frequency response characteristics and frequency deviation of the AC power grid in each region of the power system, determine the frequency security constraints of the AC power grid in each region under DC fault conditions.

[0010] Using the frequency security constraints of the AC power grid in each region under the DC fault as constraints, a DC and power planning model for a multi-region asynchronous interconnected power grid considering frequency security constraints is constructed. The GUROBI optimizer is then used to optimize and solve the planning model to obtain the DC and power planning schemes for the asynchronous interconnected power grid in each region of the power system.

[0011] Preferably, the frequency response characteristic parameters include:

[0012] Load damping ratio, mechanical power gain coefficient of each generator, governor droop control coefficient, high-pressure cylinder output ratio, inertia time constant, and reheat time constant.

[0013] Furthermore, determining the frequency security constraints of the AC power grid in each region under DC fault conditions based on relevant parameters of the frequency response characteristics and frequency deviation of the AC power grid in each region of the power system includes:

[0014] Based on the frequency response characteristics of the AC power grid in each region, the equivalent inertia time constant, load damping ratio, equivalent droop control coefficient, equivalent high-pressure cylinder output ratio, and equivalent reheat time constant of the AC power grid in each region are determined.

[0015] Based on the equivalent inertia time constant, load damping ratio, equivalent droop control coefficient, equivalent high-pressure cylinder output ratio, equivalent reheat time constant, and frequency deviation of the AC power grid in each region, an equivalent frequency response model of the AC power grid in each region is constructed.

[0016] Solve the time-domain solution of the equivalent frequency response model of the AC power grid in each region to obtain the minimum frequency of the AC power grid in each region.

[0017] Historical data of AC power grids in each region are obtained, and a dataset of AC power grids in each region is constructed based on the lowest frequency of AC power grids in each region and the historical data.

[0018] Based on the datasets of AC power grids in various regions, the equivalent frequency response models of AC power grids in various regions are piecewise linearly fitted to obtain the coefficients and intercepts of the piecewise linear fit for AC power grids in various regions.

[0019] Frequency security constraints for AC power grids in each region under DC fault conditions are constructed based on the coefficients and intercepts of piecewise linear fitting of each region's AC power grid.

[0020] Furthermore, the calculation formulas for the equivalent frequency response models of the AC power grids in each region are as follows:

[0021] In the formula, ΔP i (s) represents the unbalanced power of the regional AC power grid i, H i Let be the equivalent inertial time constant, s be a complex variable, and D be the time constant. i F is the load damping ratio. H,i For the equivalent high-pressure cylinder output ratio, T R,i R is the equivalent reheat time constant. i Δf is the equivalent droop control coefficient. i (s) represents the frequency deviation of the regional AC power grid i.

[0022] Furthermore, the calculation formula for the frequency security constraints of the AC power grid in each region under the DC fault is as follows:

[0023] In the formula, Let K be the transpose of the Kth coefficient vector corresponding to the AC power grid of the i-th region. To calculate the frequency characteristic parameters of the AC power grid in the i-th region during time period t in the simulation scenario, β i,k This represents the k-th intercept corresponding to the AC power grid in the i-th region. DC line l DC The power Δf during time period t in the simulated scenario e max,i Let L be the maximum allowable frequency deviation of the AC power grid in the i-th region, K be the number of segments in the linear fitting of the equivalent frequency response model, and L be the maximum allowable frequency deviation. DC,i This is the set of DC lines connected to the AC power grid of the i-th region.

[0024] Furthermore, the construction process of the DC and power supply planning model for the multi-region asynchronous interconnected power grid considering frequency security constraints includes:

[0025] The objective function is constructed with the goal of minimizing the sum of annualized construction cost and annualized operating cost.

[0026] The following constraints are used to construct a multi-regional asynchronous interconnected power grid DC and power supply planning model considering frequency security constraints: frequency security constraints, power flow constraints, DC line power balance constraints, line transmission power constraints, power constraints, ramping constraints, minimum start-up and shutdown time constraints, reserve capacity constraints, constraints between the start-up and shutdown state variables of the generators to be built and the variables to be put into construction, constraints between the line power of the DC lines to be built and the capacity to be put into construction, and constraints on the discretization of the capacity to be put into construction, in combination with the objective function.

[0027] Furthermore, the objective function is calculated as follows:

[0028] In the formula, F is the sum of the annualized construction cost and the annualized operating cost. For annualized construction costs, Annualized operating costs;

[0029] The formula for calculating the annualized construction cost is as follows:

[0030] In the formula, r is the annual interest rate, N is the equipment lifespan, and G... c Let x be the set of generators to be built. g x is the value indicating whether generator g is to be constructed. g A value of 0 indicates no investment or construction; x g An equal value of 1 indicates investment and construction, C g The construction cost of generator g, This is a collection of DC lines to be built. DC line l DC Whether to invest or build A value of 0 indicates no investment or construction; x lDC An equal value of 1 indicates investment or construction. DC line l DC Fixed construction costs DC line l DC The construction capacity, For use with DC line l DC Variable construction costs related to the capacity to be constructed;

[0031] The formula for calculating the annualized operating cost is as follows:

[0032] In the formula, S is the set of simulation scenarios, and π e Let T be the probability of running simulation scenario e, T be the time range within each scenario, and G be the set of all generators. To calculate the power of generator g during time period t in the simulation scenario e, The start-up cost of generator g, For the generator g start-up indicator variable during time period t in the simulation scenario e, The shutdown cost of generator g, This is the shutdown indicator variable for generator g during time period t in the simulation scenario e.

[0033] A second aspect of this application proposes a multi-region asynchronous interconnected power grid planning system considering frequency security constraints, comprising:

[0034] The acquisition module is used to acquire relevant parameters and frequency deviations of the frequency response characteristics of AC power grids in various regions of the power system.

[0035] The determination module is used to determine the frequency security constraints of the AC grid in each region under DC fault based on the relevant parameters of the frequency response characteristics and frequency deviation of the AC grid in each region of the power system.

[0036] The planning module is used to construct a DC and power planning model for a multi-regional asynchronous interconnected power grid that considers frequency security constraints, using the frequency security constraints of the AC power grid in each region under the DC fault as the constraint condition. The planning model is then optimized and solved using the GUROBI optimizer to obtain the DC and power planning schemes for the asynchronous interconnected power grid in each region of the power system.

[0037] Preferably, the frequency response characteristic parameters include:

[0038] Load damping ratio, mechanical power gain coefficient of each generator, governor droop control coefficient, high-pressure cylinder output ratio, inertia time constant, and reheat time constant.

[0039] Furthermore, the determining module includes:

[0040] The first determining unit is used to determine the equivalent inertia time constant, load damping ratio, equivalent droop control coefficient, equivalent high-pressure cylinder output ratio, and equivalent reheat time constant of the AC power grid in each region based on the relevant parameters of the frequency response characteristics of the AC power grid in each region.

[0041] The first construction unit is used to construct the equivalent frequency response model of the AC power grid in each region based on the equivalent inertia time constant, load damping ratio, equivalent droop control coefficient, equivalent high-pressure cylinder output ratio, equivalent reheat time constant and frequency deviation of the AC power grid in each region.

[0042] The solution unit is used to solve the time-domain solution of the equivalent frequency response model of the AC power grid in each region, and to obtain the lowest point of the AC power grid frequency in each region.

[0043] The second construction unit is used to acquire historical data of AC power grids in each region, and to construct a dataset of AC power grids in each region based on the lowest frequency of AC power grids in each region and historical data.

[0044] The linear fitting unit is used to perform piecewise linear fitting on the equivalent frequency response model of the AC power grid in each region based on the dataset of the AC power grid in each region, so as to obtain the coefficients and intercepts of the piecewise linear fitting of the AC power grid in each region.

[0045] The third building unit is used to construct frequency security constraints for AC power grids in each region under DC fault conditions based on the coefficients and intercepts of piecewise linear fitting of AC power grids in each region.

[0046] The technical solutions provided by the embodiments of this application bring at least the following beneficial effects:

[0047] This application proposes a planning method and system for multi-regional asynchronous interconnected power grids considering frequency security constraints. The method includes: obtaining relevant parameters of the frequency response characteristics and frequency deviations of the AC power grids in each region of the power system; determining the frequency security constraints of the AC power grids in each region under DC fault conditions based on the relevant parameters and frequency deviations; constructing a DC and power planning model for the multi-regional asynchronous interconnected power grids considering frequency security constraints using the frequency security constraints of the AC power grids in each region under DC fault conditions; and optimizing the planning model using the GUROBI optimizer to obtain the DC and power planning schemes for the asynchronous interconnected power grids in each region of the power system. The technical solution proposed in this application can effectively ensure that the DC and power planning schemes for multi-regional asynchronous interconnected power grids under high-proportion renewable energy access meet frequency security requirements, providing decision support for power system planning.

[0048] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0049] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0050] Figure 1 is a flowchart of a multi-region asynchronous interconnected power grid planning method considering frequency security constraints according to an embodiment of this application;

[0051] Figure 2 is a structural diagram of a multi-region asynchronous interconnected power grid planning system considering frequency security constraints according to an embodiment of this application;

[0052] Figure 3 is a structural diagram of a determining module provided according to an embodiment of this application. Detailed Implementation

[0053] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0054] This application proposes a planning method and system for multi-regional asynchronous interconnected power grids considering frequency security constraints. The method includes: obtaining relevant parameters of frequency response characteristics and frequency deviations of AC power grids in each region of the power system; determining frequency security constraints of AC power grids in each region under DC fault conditions based on the relevant parameters of frequency response characteristics and frequency deviations of AC power grids in each region of the power system; constructing a DC and power supply planning model for multi-regional asynchronous interconnected power grids considering frequency security constraints using the frequency security constraints of AC power grids in each region under DC fault conditions; and optimizing and solving the planning model using the GUROBI optimizer to obtain DC and power supply planning schemes for asynchronous interconnected power grids in each region of the power system. The technical solution proposed in this application can effectively ensure that the DC and power supply planning schemes for multi-regional asynchronous interconnected power grids under high-proportion renewable energy access meet frequency security requirements, providing decision support for power system planning.

[0055] The following description, with reference to the accompanying drawings, illustrates a multi-region asynchronous interconnected power grid planning method and system that considers frequency security constraints, according to an embodiment of this application.

[0056] Example 1

[0057] Figure 1 is a flowchart of a multi-region asynchronous interconnected power grid planning method considering frequency security constraints according to an embodiment of this application. As shown in Figure 1, the method includes:

[0058] Step 1: Obtain relevant parameters and frequency deviations of the frequency response characteristics of the AC power grid in each region of the power system.

[0059] In this embodiment of the disclosure, the frequency response characteristic related parameters include:

[0060] Load damping ratio, mechanical power gain coefficient of each generator, governor droop control coefficient, high-pressure cylinder output ratio, inertia time constant, and reheat time constant.

[0061] It should be noted that step 1 specifically includes:

[0062] Read relevant parameters of the system's frequency response characteristics. Specifically, this includes the load damping ratio D of each regional power grid. i The mechanical power gain coefficient K of each generator g g Governor droop control coefficient R g High-pressure cylinder output ratio F gInertial time constant H g Reheat time constant T g .

[0063] Read the relevant parameters of the objective function and constraints of the simulation model. Specifically, this includes the power generation cost function C of generator g. g (·), maximum power and minimum power Maximum uphill speed and maximum downhill climbing rate Minimum continuous boot time and minimum continuous downtime Transmission line capacity parameters. Read data from typical operational simulation scenarios, including system power load and renewable energy output.

[0064] Read the relevant parameters of the objective function and constraints of the planning model. Specifically, this includes the set of generators to be built, G. c Collection of DC lines to be built Annual interest rate on capital r, equipment lifespan N, and construction cost C of the generator to be built g. g DC transmission line to be built DC Fixed construction costs Variable construction costs related to the capacity to be constructed Minimum capacity that can be built Interval values ​​of available capacity

[0065] Step 2: Determine the frequency safety constraints of the AC power grid in each region under DC fault conditions based on the relevant parameters of the frequency response characteristics and frequency deviation of the AC power grid in each region of the power system.

[0066] In this embodiment of the disclosure, step 2 specifically includes:

[0067] 2.1: Based on the frequency response characteristics of the AC power grid in each region, determine the equivalent inertia time constant, load damping ratio, equivalent droop control coefficient, equivalent high-pressure cylinder output ratio, and equivalent reheat time constant of the AC power grid in each region.

[0068] 2.2: Construct an equivalent frequency response model for the AC power grid of each region based on the equivalent inertia time constant, load damping ratio, equivalent droop control coefficient, equivalent high-pressure cylinder output ratio, equivalent reheat time constant, and frequency deviation of the AC power grid in each region.

[0069] The calculation formulas for the equivalent frequency response models of the AC power grids in each region are as follows:

[0070] In the formula, ΔP i(s) represents the unbalanced power of the regional AC power grid i, Hi is the equivalent inertial time constant, s is a complex variable, and D i F is the load damping ratio. H,i For the equivalent high-pressure cylinder output ratio, T R,i R is the equivalent reheat time constant. i Δf is the equivalent droop control coefficient. i (s) represents the frequency deviation of the regional AC power grid i.

[0071] 2.3: Solve the time-domain solution of the equivalent frequency response model of the AC power grid in each region to obtain the lowest frequency point of the AC power grid in each region;

[0072] 2.4: Obtain historical data of AC power grids in each region, and construct a dataset of AC power grids in each region based on the lowest frequency of AC power grids in each region and historical data;

[0073] 2.5: Based on the datasets of AC power grids in various regions, the equivalent frequency response models of AC power grids in various regions are subjected to piecewise linear fitting to obtain the coefficients and intercepts of the piecewise linear fitting of AC power grids in various regions.

[0074] 2.6: Construct frequency security constraints for AC power grids in each region under DC fault conditions based on the coefficients and intercepts of piecewise linear fitting of AC power grids in each region.

[0075] The calculation formula for the frequency security constraint of the AC power grid in each region under the DC fault is as follows:

[0076] In the formula, Let K be the transpose of the Kth coefficient vector corresponding to the AC power grid of the i-th region. To calculate the frequency characteristic parameters of the AC power grid in the i-th region during time period t in the simulation scenario, β i,k This represents the k-th intercept corresponding to the AC power grid in the i-th region. DC line l DC The power Δf during time period t in the simulated scenario e max,i Let L be the maximum allowable frequency deviation of the AC power grid in the i-th region, K be the number of segments in the linear fitting of the equivalent frequency response model, and L be the maximum allowable frequency deviation. DC,i This is the set of DC lines connected to the AC power grid of the i-th region.

[0077] It should be noted that step 2 specifically includes:

[0078] 1) Construct the equivalent frequency response model of the regional power grid. For the i-th regional power grid, the input variable of the model is the equivalent inertial time constant H. i Load damping ratio D i Equivalent droop control coefficient R iEquivalent high-pressure cylinder output ratio F H,i Equivalent reheat time constant T R,i The equivalent frequency response model is shown below:

[0079] In the formula, Δf i (s) is the frequency deviation of the regional AC power grid i, ΔP i (s) represents the unbalanced power of the regional AC power grid i. This unbalanced power is represented by a step function, where ΔP i This refers to the numerical value of the unbalanced power:

[0080] Solving the time-domain solution of the above model yields the minimum point Δf of the grid frequency in the i-th region under this unbalanced power disturbance. ndr,i :

[0081] In the formula, t ndr,i ω represents the time required for the power grid frequency in the i-th region to reach its lowest point. n,i ξ i ω r,i α i These are the dynamic parameters of the power grid in the i-th region, calculated as follows:

[0082] 2) Construct a dataset based on historical data. The expression for the lowest point of the regional power grid frequency obtained in sub-step S21 is denoted as:

[0083] In the formula, This represents the frequency characteristic parameters of the i-th regional power grid. Based on historical power grid operation data, we can obtain N... i A dataset of data points Based on the expression for the lowest point of the regional power grid frequency h(X) i For each data point Calculate the expression output This results in a dataset containing both input and output.

[0084] 3) Piecewise linear fitting of the frequency response model. Solve the following optimization problem, where... express The fitted value, (α) i,1 ,β i,1 ),...,(α i,K ,β i,K ) represents the coefficients and intercept of the piecewise linear fit, and K represents the number of segments.

[0085] After piecewise linear fitting, the coefficients and intercept (α) of the piecewise linear fit are obtained. i,1 ,β i,1 ),...,(α i,K ,β i,K ).

[0086] 4) Construct frequency security constraints for power grids in various regions under DC fault conditions.

[0087] Let Δf max,i Let represent the maximum allowable frequency deviation of the power grid in the i-th region. Then, the frequency security constraint of the power grid in the i-th region can be expressed as:

[0088] During the simulation scenario s-time period t, let This indicates the start-stop status of generator g. Let represent the total load of the i-th regional power grid, then the frequency characteristic parameters of the i-th regional power grid are... The calculation method is as follows:

[0089] In the formula, G i H represents the set of generators in the i-th regional power grid. g This represents the inertial time constant of generator g. R represents the maximum power of generator g. g F represents the governor droop control coefficient of generator g. g This indicates the output ratio of the high-pressure cylinder of generator g.

[0090] Under DC fault conditions, the unbalanced power of the regional power grid is equal to the DC power before the fault. Therefore, the frequency security constraint for the i-th regional power grid within time period t of the simulation scenario e is:

[0091] In the formula, Let K be the transpose of the Kth coefficient vector corresponding to the AC power grid of the i-th region. To calculate the frequency characteristic parameters of the AC power grid in the i-th region during time period t in the simulation scenario, β i,k This represents the k-th intercept corresponding to the AC power grid in the i-th region. DC line l DC The power Δf during time period t in the simulated scenario e max,i Let L be the maximum allowable frequency deviation of the AC power grid in the i-th region, K be the number of segments in the linear fitting of the equivalent frequency response model, and L be the maximum allowable frequency deviation. DC,i This is the set of DC lines connected to the AC power grid of the i-th region.

[0092] Step 3: Using the frequency security constraints of the AC power grid in each region under the DC fault as constraints, construct a DC and power planning model for a multi-region asynchronous interconnected power grid that considers frequency security constraints, and use the GUROBI optimizer to optimize and solve the planning model to obtain the DC and power planning schemes for the asynchronous interconnected power grid in each region of the power system.

[0093] In this embodiment of the disclosure, the process of constructing the DC and power planning model for a multi-region asynchronous interconnected power grid that considers frequency security constraints includes:

[0094] The objective function is constructed with the goal of minimizing the sum of annualized construction cost and annualized operating cost.

[0095] The following constraints are used to construct a multi-regional asynchronous interconnected power grid DC and power supply planning model considering frequency security constraints: frequency security constraints, power flow constraints, DC line power balance constraints, line transmission power constraints, power constraints, ramping constraints, minimum start-up and shutdown time constraints, reserve capacity constraints, constraints between the start-up and shutdown state variables of the generators to be built and the variables to be put into construction, constraints between the line power of the DC lines to be built and the capacity to be put into construction, and constraints on the discretization of the capacity to be put into construction, in combination with the objective function.

[0096] The objective function is calculated as follows:

[0097] In the formula, F is the sum of the annualized construction cost and the annualized operating cost. For annualized construction costs, Annualized operating costs;

[0098] The formula for calculating the annualized construction cost is as follows:

[0099] In the formula, r is the annual interest rate, N is the equipment lifespan, and G... c Let x be the set of generators to be built. g x is the value indicating whether generator g is to be constructed. g A value of 0 indicates no investment or construction; x g An equal value of 1 indicates investment and construction, C g The construction cost of generator g, This is a collection of DC lines to be built. DC line l DC Whether to invest or build A value of 0 indicates no investment or construction. An equal value of 1 indicates investment or construction. DC line l DC Fixed construction costs DC line l DC The construction capacity, For use with DC line l DC Variable construction costs related to the capacity to be constructed;

[0100] The formula for calculating the annualized operating cost is as follows:

[0101] In the formula, S is the set of simulation scenarios, and π e Let T be the probability of running simulation scenario e, T be the time range within each scenario, and G be the set of all generators. To calculate the power of generator g during time period t in the simulation scenario e, The start-up cost of generator g, For the generator g start-up indicator variable during time period t in the simulation scenario e, The shutdown cost of generator g, This is the shutdown indicator variable for generator g during time period t in the simulation scenario e.

[0102] It should be noted that for communication systems, power flow constraints must be satisfied, among which... This represents the sum of the power generated by node p. N represents the electrical load of node p. AC (p) represents the set of nodes that have an AC connection with node p. and X represents the voltage phase angles at nodes p and q, respectively. pq This represents the equivalent reactance between node p and node q. Indicates DC line l DC The power injected into node p, L DC,p This represents the set of DC lines connected to node p.

[0103] The formula for calculating the power flow constraint is as follows:

[0104] For DC lines, neglecting line losses, the following power balance constraints are satisfied, and the formula for calculating the DC line power balance constraints is as follows:

[0105] In the formula, L DC (p,q) represents the set of DC lines between node p and node q;

[0106] For both AC and DC lines, line transmission power constraints must be met, among which... and Indicates the maximum transmission power of AC and DC lines. Indicates AC line l AC The reactance, L AC(p,q) and L DC (p, q) represent the sets of AC lines and DC lines between nodes p and q, respectively. and Let p and q represent the power injected into the DC line. The formula for calculating the power transmission constraint of the line is as follows:

[0107] For generators, power constraints, ramp constraints, and minimum start-up and shutdown time constraints must be met, among which... and This represents the maximum and minimum power of generator g. and This represents the maximum uphill and downhill power of generator g. and Let g represent the minimum start-up time and minimum shutdown time of generator g, wherein the calculation formulas for the power constraint, the ramp constraint, and the minimum start-up / shutdown time constraint are as follows:

[0108] For generators participating in frequency regulation, the reserve capacity constraint under the maximum frequency deviation must be met. The calculation formula for the reserve capacity constraint is as follows:

[0109] For the generator to be built, the start-up and shutdown state variables must be satisfied. With investment variable x g The constraint between the generator to be built, namely the inability to start the generator when it is not under construction, is calculated as follows:

[0110] For the DC lines to be built, their operating power It needs to meet the requirements of the construction capacity. The constraint between the line power and the installed capacity of the proposed DC line is calculated as follows:

[0111] For the construction capacity of DC lines The constraints of discretization must be met, where This indicates the minimum capacity that can be built. This represents the interval value indicating the available capacity for construction. Let M be an integer variable, and its maximum value is M. (When this DC line is not to be built) The constraint formula for calculating the discretized value of the construction capacity, which must be 0, is as follows:

[0112] It should be noted that the constructed DC and power supply planning model for a multi-regional asynchronous interconnected power grid considering frequency security constraints is a mixed-integer linear programming problem. Solving this optimization model using optimization problem-solving software such as GUROBI yields the DC and power supply planning schemes for the multi-regional asynchronous interconnected power grid, including generator deployment schemes, DC deployment schemes, and the capacity of each deployed DC line. Furthermore, the solution to this optimization model provides the unit combination and scheduling scheme for typical operational simulation scenarios, including the start-up and shutdown status and power of all generator units in the system, and the transmission power of DC lines. The execution logs and intermediate results of all previous steps are compiled and stored in a backup database for future verification.

[0113] In summary, the multi-region asynchronous interconnected power grid planning method proposed in this embodiment, which considers frequency security constraints, can effectively ensure that the DC and power supply planning schemes of multi-region asynchronous interconnected power grids with a high proportion of new energy access meet the frequency security requirements, and provide decision support for power system planning.

[0114] Example 2

[0115] Figure 2 is a structural diagram of a multi-region asynchronous interconnected power grid planning system considering frequency security constraints according to an embodiment of this application. As shown in Figure 2, the system includes:

[0116] The acquisition module 100 is used to acquire relevant parameters of frequency response characteristics and frequency deviation of AC power grids in various regions of the power system.

[0117] The determination module 200 is used to determine the frequency safety constraints of the AC power grid in each region under DC fault based on the relevant parameters of the frequency response characteristics and frequency deviation of the AC power grid in each region of the power system.

[0118] The planning module 300 is used to construct a DC and power planning model for a multi-regional asynchronous interconnected power grid that considers frequency security constraints, using the frequency security constraints of the AC power grid in each region under the DC fault as the constraint condition, and to optimize and solve the planning model using the GUROBI optimizer to obtain the DC and power planning schemes for the asynchronous interconnected power grid in each region of the power system.

[0119] It should be noted that the frequency response characteristic parameters include:

[0120] Load damping ratio, mechanical power gain coefficient of each generator, governor droop control coefficient, high-pressure cylinder output ratio, inertia time constant, and reheat time constant.

[0121] In this embodiment of the disclosure, as shown in FIG3, the determining module 200 includes:

[0122] The first determining unit 201 is used to determine the equivalent inertia time constant, load damping ratio, equivalent droop control coefficient, equivalent high-pressure cylinder output ratio, and equivalent reheat time constant of the AC power grid in each region based on the frequency response characteristic parameters of the AC power grid in each region.

[0123] The first construction unit 202 is used to construct the equivalent frequency response model of the AC power grid in each region based on the equivalent inertia time constant, load damping ratio, equivalent droop control coefficient, equivalent high-pressure cylinder output ratio, equivalent reheat time constant and frequency deviation of the AC power grid in each region.

[0124] The calculation formulas for the equivalent frequency response models of the AC power grids in each region are as follows:

[0125] In the formula, ΔP i (s) represents the unbalanced power of the regional AC power grid i, Hi is the equivalent inertial time constant, s is a complex variable, and D i F is the load damping ratio. H,i For the equivalent high-pressure cylinder output ratio, T R,i R is the equivalent reheat time constant. i Δf is the equivalent droop control coefficient. i (s) represents the frequency deviation of the regional AC power grid i.

[0126] Solver 203 is used to solve the time-domain solution of the equivalent frequency response model of the AC power grid in each region, and to obtain the lowest point of the frequency of the AC power grid in each region.

[0127] The second construction unit 204 is used to acquire historical data of AC power grids in each region, and construct a dataset of AC power grids in each region based on the lowest point of AC power grid frequency in each region and historical data.

[0128] The linear fitting unit 205 is used to perform piecewise linear fitting on the equivalent frequency response model of the AC power grid in each region based on the dataset of the AC power grid in each region, so as to obtain the coefficients and intercepts of the piecewise linear fitting of the AC power grid in each region.

[0129] The third building unit 206 is used to construct frequency security constraints for AC power grids in each region under DC fault conditions based on the coefficients and intercepts of piecewise linear fitting of AC power grids in each region.

[0130] The calculation formula for the frequency security constraint of the AC power grid in each region under the DC fault is as follows:

[0131] In the formula, Let K be the transpose of the Kth coefficient vector corresponding to the AC power grid of the i-th region. To calculate the frequency characteristic parameters of the AC power grid in the i-th region during time period t in the simulation scenario, β i,k This represents the k-th intercept corresponding to the AC power grid in the i-th region. DC line l DC The power Δf during time period t in the simulated scenario e max,i Let L be the maximum allowable frequency deviation of the AC power grid in the i-th region, K be the number of segments in the linear fitting of the equivalent frequency response model, and L be the maximum allowable frequency deviation. DC,i This is the set of DC lines connected to the AC power grid of the i-th region.

[0132] In this embodiment of the disclosure, the planning module 300 is further configured to:

[0133] The objective function is constructed with the goal of minimizing the sum of annualized construction cost and annualized operating cost.

[0134] The following constraints are used to construct a multi-regional asynchronous interconnected power grid DC and power supply planning model considering frequency security constraints: frequency security constraints, power flow constraints, DC line power balance constraints, line transmission power constraints, power constraints, ramping constraints, minimum start-up and shutdown time constraints, reserve capacity constraints, constraints between the start-up and shutdown state variables of the generators to be built and the variables to be put into construction, constraints between the line power of the DC lines to be built and the capacity to be put into construction, and constraints on the discretization of the capacity to be put into construction, in combination with the objective function.

[0135] The objective function is calculated as follows:

[0136] In the formula, F is the sum of the annualized construction cost and the annualized operating cost. For annualized construction costs, Annualized operating costs;

[0137] The formula for calculating the annualized construction cost is as follows:

[0138] In the formula, r is the annual interest rate, N is the equipment lifespan, and G... c Let x be the set of generators to be built. g x is the value indicating whether generator g is to be constructed. g A value of 0 indicates no investment or construction; x g An equal value of 1 indicates investment and construction, C g The construction cost of generator g, This is a collection of DC lines to be built. DC line l DC Whether to invest or build A value of 0 indicates no investment or construction. An equal value of 1 indicates investment or construction. DC line lDC Fixed construction costs DC line l DC The construction capacity, For use with DC line l DC Variable construction costs related to the capacity to be constructed;

[0139] The formula for calculating the annualized operating cost is as follows:

[0140] In the formula, S is the set of simulation scenarios, and π e Let T be the probability of running simulation scenario e, T be the time range within each scenario, and G be the set of all generators. To calculate the power of generator g during time period t in the simulation scenario e, The start-up cost of generator g, For the generator g start-up indicator variable during time period t in the simulation scenario e, The shutdown cost of generator g, This is the shutdown indicator variable for generator g during time period t in the simulation scenario e.

[0141] In summary, the multi-region asynchronous interconnected power grid planning system proposed in this embodiment, which considers frequency security constraints, can effectively ensure that the DC and power supply planning schemes of multi-region asynchronous interconnected power grids with a high proportion of new energy access meet the frequency security requirements, and provide decision support for power system planning.

[0142] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0143] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0144] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A planning method for multi-region asynchronous interconnected power grids considering frequency security constraints, characterized in that, The method includes: Obtain relevant parameters and frequency deviations of the frequency response characteristics of AC power grids in various regions of the power system; Based on the relevant parameters of the frequency response characteristics and frequency deviation of the AC power grid in each region of the power system, determine the frequency security constraints of the AC power grid in each region under DC fault conditions. Using the frequency security constraints of the AC power grid in each region under the DC fault as constraints, a DC and power planning model for a multi-region asynchronous interconnected power grid considering frequency security constraints is constructed. The GUROBI optimizer is then used to optimize and solve the planning model to obtain the DC and power planning schemes for the asynchronous interconnected power grid in each region of the power system.

2. The method as described in claim 1, characterized in that, The frequency response characteristics related parameters include: Load damping ratio, mechanical power gain coefficient of each generator, governor droop control coefficient, high-pressure cylinder output ratio, inertia time constant, and reheat time constant.

3. The method as described in claim 2, characterized in that, The determination of frequency security constraints for AC power grids in each region under DC fault conditions based on relevant parameters of frequency response characteristics and frequency deviations of AC power grids in each region of the power system includes: Based on the frequency response characteristics of the AC power grid in each region, the equivalent inertia time constant, load damping ratio, equivalent droop control coefficient, equivalent high-pressure cylinder output ratio, and equivalent reheat time constant of the AC power grid in each region are determined. Based on the equivalent inertia time constant, load damping ratio, equivalent droop control coefficient, equivalent high-pressure cylinder output ratio, equivalent reheat time constant, and frequency deviation of the AC power grid in each region, an equivalent frequency response model of the AC power grid in each region is constructed. Solve the time-domain solution of the equivalent frequency response model of the AC power grid in each region to obtain the minimum frequency of the AC power grid in each region. Historical data of AC power grids in each region are obtained, and a dataset of AC power grids in each region is constructed based on the lowest frequency of AC power grids in each region and the historical data. Based on the datasets of AC power grids in various regions, the equivalent frequency response models of AC power grids in various regions are piecewise linearly fitted to obtain the coefficients and intercepts of the piecewise linear fit for AC power grids in various regions. Frequency security constraints for AC power grids in each region under DC fault conditions are constructed based on the coefficients and intercepts of piecewise linear fitting of each region's AC power grid.

4. The method as described in claim 3, characterized in that, The calculation formulas for the equivalent frequency response models of the AC power grids in each region are as follows: In the formula, ΔP i (s) represents the unbalanced power of the regional AC power grid i, H i Let be the equivalent inertial time constant, s be a complex variable, and D be the time constant. i F is the load damping ratio. H,i For the equivalent high-pressure cylinder output ratio, T R,i R is the equivalent reheat time constant. i Δf is the equivalent droop control coefficient. i (s) represents the frequency deviation of the regional AC power grid i.

5. The method as described in claim 4, characterized in that, The calculation formulas for the frequency security constraints of the AC power grid in each region under the DC fault are as follows: In the formula, Let K be the transpose of the Kth coefficient vector corresponding to the AC power grid of the i-th region. To calculate the frequency characteristic parameters of the AC power grid in the i-th region during time period t in the simulation scenario, β i,k This represents the k-th intercept corresponding to the AC power grid in the i-th region. DC line l DC The power Δf during time period t in the simulated scenario e max,i Let L be the maximum allowable frequency deviation of the AC power grid in the i-th region, K be the number of segments in the linear fitting of the equivalent frequency response model, and L be the maximum allowable frequency deviation. DC,i This is the set of DC lines connected to the AC power grid of the i-th region.

6. The method as described in claim 5, characterized in that, The construction process of the DC and power supply planning model for the multi-region asynchronous interconnected power grid considering frequency security constraints includes: The objective function is constructed with the goal of minimizing the sum of annualized construction cost and annualized operating cost. The following constraints are used to construct a multi-regional asynchronous interconnected power grid DC and power supply planning model considering frequency security constraints: frequency security constraints, power flow constraints, DC line power balance constraints, line transmission power constraints, power constraints, ramping constraints, minimum start-up and shutdown time constraints, reserve capacity constraints, constraints between the start-up and shutdown state variables of the generators to be built and the variables to be put into construction, constraints between the line power of the DC lines to be built and the capacity to be put into construction, and constraints on the discretization of the capacity to be put into construction, in combination with the objective function.

7. The method as described in claim 6, characterized in that, The objective function is calculated as follows: In the formula, F is the sum of the annualized construction cost and the annualized operating cost. For annualized construction costs, Annualized operating costs; The formula for calculating the annualized construction cost is as follows: In the formula, r is the annual interest rate, N is the equipment lifespan, and G... c Let x be the set of generators to be built. g x is the value indicating whether generator g is to be constructed. g A value of 0 indicates no investment or construction; x g An equal value of 1 indicates investment and construction, C g The construction cost of generator g, This is a collection of DC lines to be built. DC line l DC Whether to invest or build A value of 0 indicates no investment or construction. An equal value of 1 indicates investment or construction. DC line l DC Fixed construction costs DC line l DC The construction capacity, For use with DC line l DC Variable construction costs related to the capacity to be constructed; The formula for calculating the annualized operating cost is as follows: In the formula, S is the set of simulation scenarios, and π e Let T be the probability of running simulation scenario e, T be the time range within each scenario, and G be the set of all generators. To calculate the power of generator g during time period t in the simulation scenario e, The start-up cost of generator g, For the generator g start-up indicator variable during time period t in the simulation scenario e, The shutdown cost of generator g, This is the shutdown indicator variable for generator g during time period t in the simulation scenario e.

8. A multi-region asynchronous interconnected power grid planning system considering frequency security constraints, characterized in that, The system includes: The acquisition module is used to acquire relevant parameters and frequency deviations of the frequency response characteristics of AC power grids in various regions of the power system. The determination module is used to determine the frequency security constraints of the AC grid in each region under DC fault based on the relevant parameters of the frequency response characteristics and frequency deviation of the AC grid in each region of the power system. The planning module is used to construct a DC and power planning model for a multi-regional asynchronous interconnected power grid that considers frequency security constraints, using the frequency security constraints of the AC power grid in each region under the DC fault as the constraint condition. The planning model is then optimized and solved using the GUROBI optimizer to obtain the DC and power planning schemes for the asynchronous interconnected power grid in each region of the power system.

9. The system as described in claim 8, characterized in that, The frequency response characteristics related parameters include: Load damping ratio, mechanical power gain coefficient of each generator, governor droop control coefficient, high-pressure cylinder output ratio, inertia time constant, and reheat time constant.

10. The system as described in claim 9, characterized in that, The determining module includes: The first determining unit is used to determine the equivalent inertia time constant, load damping ratio, equivalent droop control coefficient, equivalent high-pressure cylinder output ratio, and equivalent reheat time constant of the AC power grid in each region based on the relevant parameters of the frequency response characteristics of the AC power grid in each region. The first construction unit is used to construct the equivalent frequency response model of the AC power grid in each region based on the equivalent inertia time constant, load damping ratio, equivalent droop control coefficient, equivalent high-pressure cylinder output ratio, equivalent reheat time constant and frequency deviation of the AC power grid in each region. The solution unit is used to solve the time-domain solution of the equivalent frequency response model of the AC power grid in each region, and to obtain the lowest point of the AC power grid frequency in each region. The second construction unit is used to acquire historical data of AC power grids in each region, and to construct a dataset of AC power grids in each region based on the lowest frequency of AC power grids in each region and historical data. The linear fitting unit is used to perform piecewise linear fitting on the equivalent frequency response model of the AC power grid in each region based on the dataset of the AC power grid in each region, so as to obtain the coefficients and intercepts of the piecewise linear fitting of the AC power grid in each region. The third building unit is used to construct frequency security constraints for AC power grids in each region under DC fault conditions based on the coefficients and intercepts of piecewise linear fitting of AC power grids in each region.

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