Multi-region asynchronous interconnected power grid planning method and system considering frequency security constraint

Abstract

The invention provides a multi-region asynchronous interconnected power grid planning method and system considering frequency security constraints. The method comprises the steps of obtaining frequency response characteristic related parameters and frequency deviations of alternating current power grids in all regions of a power system; according to the frequency response characteristic related parameters and the frequency deviation of the AC power grid in each region of the power system, determining the frequency safety constraint of the AC power grid in each region under the DC fault; and constructing a multi-region asynchronous interconnected power grid direct current and power supply planning model considering the frequency safety constraint by taking the frequency safety constraint of the alternating current power grid of each region under the direct current fault as a constraint condition, and carrying out optimization solution on the planning model by utilizing a GUROBI optimizer to obtain a direct current and power supply planning scheme of the asynchronous interconnected power grid of each region of the power system. According to the technical scheme, it can be effectively guaranteed that the direct current and power source planning scheme of the multi-region asynchronous power grid interconnected power grid meets the frequency safety requirement under high-proportion new energy access, and decision support is provided for power system planning.

Description

Technical Field

[0001] The present application relates to the field of power system planning, and in particular to a method and system for planning a multi-region asynchronous interconnected power grid taking into account frequency safety constraints. Background Art

[0002] With the development of wind power and photovoltaic resources in deserts, Gobi and wasteland areas, as well as the widespread access to offshore wind power, large-scale long-distance cross-regional power transmission will become an important way to utilize and consume clean energy. Compared with high-voltage AC transmission, high-voltage DC transmission has lower costs in long-distance and large-capacity transmission scenarios, and the transmission power is controllable. It has been widely used in scenarios such as clean energy transmission, submarine cable transmission, and asynchronous power grid interconnection. For China, the distance between the western power generation base and the eastern and southern coastal load centers is mostly more than 1,000 kilometers. HVDC is a more economical and feasible technical route to achieve large-scale long-distance transmission of power resources. With the widespread application of high-voltage DC transmission technology, some regional power grids have now formed a structure that is asynchronously interconnected with external power grids through DC lines.

[0003] As synchronous units are gradually replaced by high-proportion renewable energy, the inertia of the power system shows a downward trend, and frequency regulation resources are lacking. In the case of large active power disturbances, the frequency of the power system may drop rapidly, resulting in low-frequency load shedding or even system frequency collapse, which seriously threatens the reliability of power supply. For asynchronous interconnected power grids, when a large-capacity DC transmission line fails, it will have a great impact on the frequency safety of the regional power grid. Therefore, the planning of multi-region asynchronous interconnected power grids requires the reasonable selection of cross-regional DC capacity and the reasonable allocation of frequency regulation resources such as power supplies. In terms of planning considering frequency safety constraints, the existing technology mainly considers adding frequency safety constraints to the model at the operation simulation level, and the planning objects are generally power supplies and energy storage. However, the current planning of DC lines mainly focuses on its economy and operation benefits, and lacks consideration of the impact of cross-regional large-capacity DC on the frequency safety of regional power grids in planning, resulting in the inability of the power grid to operate safely and stably. Summary of the invention

[0004] The present application provides a multi-region asynchronous interconnected power grid planning method and system taking into account frequency safety constraints, so as to at least solve the technical problem that the power grid cannot operate safely and stably due to the impact of cross-regional large-capacity direct current on regional power grid frequency safety during planning.

[0005] The first aspect of the present application provides a method for planning a multi-region asynchronous interconnected power grid considering frequency safety constraints, the method comprising:

[0006] Obtain frequency response characteristic related parameters and frequency deviation of AC power grid in each area of ​​power system;

[0007] Determine frequency safety constraints of AC power grids in each region under DC faults according to frequency response characteristic related parameters and frequency deviation of AC power grids in each region of the power system;

[0008] Taking the frequency safety constraints of the AC power grids in each region under the DC fault as constraints, a DC and power supply planning model for multi-regional asynchronous interconnected power grids considering frequency safety constraints is constructed, and the planning model is optimized and solved using the GUROBI optimizer to obtain the DC and power supply planning schemes for the asynchronous interconnected power grids in each region of the power system.

[0009] Preferably, the frequency response characteristic related parameters include:

[0010] 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.

[0011] Furthermore, determining the frequency safety constraints of the AC power grids in each region under a DC fault according to the frequency response characteristic related parameters and frequency deviation of the AC power grids in each region of the power system includes:

[0012] 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 grids in each region based on the frequency response characteristic related parameters of the AC power grids in each region;

[0013] Constructing an equivalent frequency response model of each regional AC power grid according to 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 each regional AC power grid;

[0014] Solve the time domain solution of the equivalent frequency response model of the AC power grid in each region to obtain the lowest point of the frequency of the AC power grid in each region;

[0015] Acquire historical data of AC power grids in each region, and construct data sets of AC power grids in each region based on the lowest point of the frequency of the AC power grids in each region and the historical data;

[0016] Based on the data sets of the AC power grids in each region, piecewise linear fitting is performed on the equivalent frequency response model of the AC power grids in each region, and coefficients and intercepts of the piecewise linear fitting of the AC power grids in each region are obtained;

[0017] Based on the coefficients and intercepts of the piecewise linear fitting of the AC power grid in each region, the frequency security constraints of the AC power grid in each region under DC faults are constructed.

[0018] Furthermore, the calculation formula of the equivalent frequency response model of the AC power grid in each region is as follows:

[0019]

[0020] Where ΔP i (s) is the unbalanced power of regional AC power grid i, H i is the equivalent inertia time constant, s is a complex variable, D i is the load damping ratio, F H，i is the equivalent high-pressure cylinder output ratio, T R，i is the equivalent reheat time constant, R i is the equivalent droop control coefficient, Δf i (s) is the frequency deviation of regional AC power grid i.

[0021] Furthermore, the calculation formula for the frequency safety constraint of the AC power grid in each region under the DC fault is as follows:

[0022]

[0023] In the formula, is the transpose of the Kth coefficient vector corresponding to the i-th regional AC power grid, is the frequency characteristic parameter of the AC power grid in the ith region during the period t of the simulation scenario e, β i，k is the kth intercept corresponding to the AC power grid in the ith region, For DC line l DC The power during the period t of the running simulation scenario e, Δf max,i is, K is the number of segments of the linear fitting of the equivalent frequency response model, is the set of DC lines connected to the AC grid in the i-th region.

[0024] Furthermore, the construction process of the multi-region asynchronous interconnected power grid DC and power supply planning model 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 frequency safety constraints of the AC power grids in each region under DC faults, power flow constraints, power balance constraints of DC lines, line transmission power constraints, power constraints, climbing constraints, minimum start-up and shutdown time constraints, spare capacity constraints, constraints between the start-up and shutdown state variables of the generator to be built and the construction variables, constraints between the operating power of the DC lines to be built and the construction capacity, and constraints on the discrete value of the construction capacity are used as constraint conditions, and combined with the objective function, a DC and power supply planning model for multi-regional asynchronous interconnected power grids considering frequency safety constraints is constructed.

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

[0028]

[0029] Where F is the sum of annual construction cost and annual operation cost. is the annualized construction cost, is the annualized operating cost;

[0030] The calculation formula of the annualized construction cost is as follows:

[0031]

[0032] In the formula, r is the annual interest rate, N is the equipment life, is the set of generators to be built, x g is the value of whether the generator g is put into construction, x g Equal to 0 means no investment, x g Equal to 1 means investment, C g is the construction cost of generator g, is the set of DC lines to be built, For DC line l DC Whether to invest in construction, Equal to 0 means no investment, Equal to 1 means investment and construction, For DC line l DC Fixed construction costs, For DC line l DC The investment capacity, For the DC line l DC Variable construction costs related to construction capacity;

[0033] The annualized operating cost is calculated as follows:

[0034]

[0035] In the formula, To run a set of simulation scenarios, π e is the probability of running simulation scenario e, For the time range within each scene, is the set of all generators, is the power of generator g during period t of running simulation scenario e, is the startup cost of generator g, is the startup indicator variable of generator g in period t of running simulation scenario e, is the shutdown cost of generator g, is the shutdown indicator variable of generator g during period t of running simulation scenario e.

[0036] The second aspect of the present application provides a multi-region asynchronous interconnected power grid planning system considering frequency safety constraints, including:

[0037] An acquisition module is used to obtain frequency response characteristic related parameters and frequency deviation of AC power grids in various regions of the power system;

[0038] A determination module, used to determine the frequency safety constraints of the AC power grids in each region under a DC fault according to the frequency response characteristic related parameters and frequency deviation of the AC power grids in each region of the power system;

[0039] The planning module is used to construct a DC and power supply planning model for multi-region asynchronous interconnected power grids considering frequency safety constraints based on the frequency safety constraints of the AC power grids in each region under the DC fault, and use the GUROBI optimizer to optimize and solve the planning model to obtain the DC and power supply planning schemes for the asynchronous interconnected power grids in each region of the power system.

[0040] Preferably, the frequency response characteristic related parameters include:

[0041] 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.

[0042] Furthermore, the determination module includes:

[0043] A first determination unit is used to determine an equivalent inertia time constant, a load damping ratio, an equivalent droop control coefficient, an equivalent high-pressure cylinder output ratio, and an equivalent reheat time constant of the AC power grids in each region based on frequency response characteristic related parameters of the AC power grids in each region;

[0044] A first construction unit is used to construct an equivalent frequency response model of each regional AC power grid according to an equivalent inertia time constant, a load damping ratio, an equivalent droop control coefficient, an equivalent high-pressure cylinder output ratio, an equivalent reheat time constant and a frequency deviation of each regional AC power grid;

[0045] A solving unit, used for solving the time domain solution of the equivalent frequency response model of the AC power grid in each region, and obtaining the lowest point of the frequency of the AC power grid in each region;

[0046] A second construction unit is used to obtain historical data of the AC power grid in each region, and to construct a data set of the AC power grid in each region based on the lowest point of the frequency of the AC power grid in each region and the historical data;

[0047] A linear fitting unit is used to perform piecewise linear fitting on an equivalent frequency response model of each regional AC power grid based on a data set of each regional AC power grid, so as to obtain coefficients and intercepts of the piecewise linear fitting of each regional AC power grid;

[0048] The third construction unit is used to construct frequency safety constraints of the AC power grids in each region under a DC fault based on coefficients and intercepts of the piecewise linear fitting of the AC power grids in each region.

[0049] The technical solution provided by the embodiments of the present application brings at least the following beneficial effects:

[0050] The present application proposes a multi-region asynchronous interconnected power grid planning method and system considering frequency safety constraints, the method comprising: obtaining frequency response characteristic related parameters and frequency deviation of AC power grids in each region of the power system; determining the frequency safety constraints of AC power grids in each region under DC faults according to the frequency response characteristic related parameters and frequency deviation of AC power grids in each region of the power system; taking the frequency safety constraints of AC power grids in each region under DC faults as constraints, constructing a DC and power planning model of multi-region asynchronous interconnected power grids considering frequency safety constraints, and optimizing and solving the planning model using the GUROBI optimizer to obtain DC and power planning schemes of asynchronous interconnected power grids in each region of the power system. The technical solution proposed in the present application can effectively ensure that the DC and power planning schemes of the interconnected power grids of multi-region asynchronous power grids under high proportion of new energy access meet the requirements of frequency safety, and provide decision support for power system planning. 。

[0051] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0053] Figure 1 A flowchart of a multi-region asynchronous interconnected power grid planning method considering frequency security constraints provided according to an embodiment of the present application;

[0054] Figure 2 A structural diagram of a multi-region asynchronous interconnected power grid planning system considering frequency safety constraints provided according to an embodiment of the present application;

[0055] Figure 3 The present invention is a structural diagram of a determination module provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0056] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0057] The present application proposes a method and system for planning a multi-region asynchronous interconnected power grid that considers frequency safety constraints, the method comprising: obtaining frequency response characteristic-related parameters and frequency deviation of the AC power grids in each region of the power system; determining the frequency safety constraints of the AC power grids in each region under a DC fault according to the frequency response characteristic-related parameters and frequency deviation of the AC power grids in each region of the power system; taking the frequency safety constraints of the AC power grids in each region under the DC fault as constraints, constructing a DC and power supply planning model for a multi-region asynchronous interconnected power grid that considers frequency safety constraints, and using the GUROBI optimizer to optimize and solve the planning model to obtain the DC and power supply planning schemes for the asynchronous interconnected power grids in each region of the power system. The technical solution proposed in the present application can effectively ensure that the DC and power supply planning schemes of the interconnected power grids of multi-region asynchronous power grids under a high proportion of new energy access meet the requirements of frequency safety, and provide decision support for power system planning.

[0058] The following describes, with reference to the accompanying drawings, a multi-region asynchronous interconnected power grid planning method and system taking into account frequency safety constraints in an embodiment of the present application.

[0059] Embodiment 1

[0060] Figure 1 The flowchart of a multi-region asynchronous interconnected power grid planning method considering frequency safety constraints is provided according to an embodiment of the present application. Figure 1 As shown, the method includes:

[0061] Step 1: Obtain the frequency response characteristic related parameters and frequency deviation of the AC power grid in each area of ​​the power system.

[0062] In the embodiment of the present disclosure, the frequency response characteristic related parameters include:

[0063] 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.

[0064] It should be noted that step 1 specifically includes:

[0065] Read the system frequency response characteristics related parameters. Specifically including the load damping ratio D of each regional power grid i , the mechanical power gain coefficient K of each generator g g , speed governor droop control coefficient R g , High pressure cylinder output ratio F g , inertia time constant H g , Reheat time constant T g .

[0066] Read the relevant parameters of the objective function and constraints of the simulation model. Specifically, it includes the power generation cost function C of the generator g.g (·), maximum power and minimum power Maximum climbing rate and maximum downhill climbing rate Minimum continuous power-on time and minimum continuous downtime Transmission line capacity parameters. Read typical operation simulation scenario data, including system power load, new energy output, etc.

[0067] Read the relevant parameters of the planning model objective function and constraints. Specifically, it includes the set of generators to be built DC lines to be built Annual interest rate of capital r, equipment life N, construction cost C of the generator g to be built g , DC lines to be built DC Fixed construction costs Variable construction costs related to construction capacity Minimum capacity that can be built Interval value of the capacity that can be put into construction

[0068] Step 2: Determine frequency safety constraints of the AC power grids in each region under a DC fault according to frequency response characteristic-related parameters and frequency deviations of the AC power grids in each region of the power system.

[0069] In the embodiment of the present disclosure, step 2 specifically includes:

[0070] 2.1: 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 grids in each region based on the frequency response characteristic related parameters of the AC power grids in each region;

[0071] 2.2: Constructing an equivalent frequency response model of the AC power grid in each region according to 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;

[0072] The calculation formula of the equivalent frequency response model of the AC power grid in each region is as follows:

[0073]

[0074] Where ΔP i (s) is the unbalanced power of regional AC power grid i, H i is the equivalent inertia time constant, s is a complex variable, D i is the load damping ratio, F H，i is the equivalent high-pressure cylinder output ratio, T R，iis the equivalent reheat time constant, R i is the equivalent droop control coefficient, Δf i (s) is the frequency deviation of regional AC power grid i.

[0075] 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 point of the AC power grid frequency in each region;

[0076] 2.4: Obtain historical data of the AC power grid in each region, and construct a data set of the AC power grid in each region based on the lowest point of the frequency of the AC power grid in each region and the historical data;

[0077] 2.5: Based on the data sets of the AC power grids in each region, the equivalent frequency response model of the AC power grids in each region is fitted piecewise linearly to obtain the coefficients and intercepts of the piecewise linear fitting of the AC power grids in each region;

[0078] 2.6: Based on the coefficients and intercepts of the piecewise linear fitting of the AC power grid in each region, the frequency security constraints of the AC power grid in each region under DC faults are constructed.

[0079] The calculation formula of the frequency safety constraint of the AC power grid in each region under the DC fault is as follows:

[0080]

[0081] In the formula, is the transpose of the Kth coefficient vector corresponding to the i-th regional AC power grid, is the frequency characteristic parameter of the AC power grid in the ith region during the period t of the simulation scenario e, β i，k is the kth intercept corresponding to the AC power grid in the ith region, For DC line l DC The power during the period t of the running simulation scenario e, Δf max，i is, K is the number of segments of the linear fitting of the equivalent frequency response model, is the set of DC lines connected to the AC grid in the i-th region.

[0082] It should be noted that step 2 specifically includes:

[0083] 1) Construct an 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 inertia time constant H i , load damping ratio D i , equivalent droop control coefficient R i , Equivalent high pressure cylinder output ratio F H，i , equivalent reheat time constant T R，i , the equivalent frequency response model is as follows:

[0084]

[0085] Where Δf i (s) is the frequency deviation of regional AC power grid i, ΔP i (s) is the unbalanced power of regional AC power grid i. The unbalanced power is represented by a step function, where ΔP i is the numerical value of unbalanced power:

[0086]

[0087] Solving the time domain solution of the above model, we can obtain the lowest point Δf of the grid frequency in the i-th region under the unbalanced power disturbance. ndr，i :

[0088]

[0089] In the formula, t ndr，i It represents the time required for the grid frequency in the ith region to reach the lowest point, ω n，i , i ,ω r，i , α i are the dynamic parameters of the ith regional power grid, and the calculation method is as follows:

[0090]

[0091] 2) Construct a data set based on historical data. The lowest point expression of the regional power grid frequency obtained in sub-step S21 is recorded as:

[0092]

[0093] In the formula, Represents the frequency characteristic parameters of the ith regional power grid. Based on the historical operation data of the power grid, we can get i Dataset with data points Based on the lowest point expression of the regional power grid frequency h(X i ), for each data point Calculate expression output This results in a data set containing input and output

[0094] 3) Piecewise linear fitting frequency response model. Solve the following optimization problem, where express The fitted value of (α i，1 , β i，1 ),...,(α i，K , β i，K ) represents the coefficient and intercept of piecewise linear fitting, and K represents the number of segments.

[0095]

[0096] After piecewise linear fitting, the coefficients and intercept (α i，1 , β i，1 ),...,(α i，K , β i，K ).

[0097] 4) Establish frequency safety constraints for power grids in each region under DC faults.

[0098] Let Δf max，i represents the maximum frequency deviation allowed by the ith regional power grid, then the frequency security constraint of the ith regional power grid can be expressed as:

[0099]

[0100] In the simulation scenario s period t, let Indicates the start and stop status of the generator g, represents the total load of the ith regional power grid, then the frequency characteristic parameter of the ith regional power grid is The calculation method is as follows:

[0101]

[0102] In the formula, represents the set of generators in the ith regional power grid, H g represents the inertia time constant of the generator g, represents the maximum power of the generator g, R g represents the governor droop control coefficient of generator g, F g Indicates the output ratio of the high-pressure cylinder of the generator g.

[0103] Under a DC fault, the unbalanced power of the regional power grid is the DC power before the fault. The frequency security constraint of the ith regional power grid in the simulation scenario e during period t is:

[0104]

[0105] In the formula, is the transpose of the Kth coefficient vector corresponding to the i-th regional AC power grid, is the frequency characteristic parameter of the AC power grid in the ith region during the period t of the simulation scenario e, β i，k is the kth intercept corresponding to the AC power grid in the ith region, For DC line l DC The power during the period t of the running simulation scenario e, Δf max，i is, K is the number of segments of the linear fitting of the equivalent frequency response model, is the set of DC lines connected to the AC grid in the i-th region.

[0106] Step 3: Taking the frequency safety constraints of the AC power grids in each region under the DC fault as constraints, a DC and power supply planning model for multi-region asynchronous interconnected power grids considering frequency safety constraints is constructed, and the planning model is optimized and solved using the GUROBI optimizer to obtain the DC and power supply planning schemes for the asynchronous interconnected power grids in each region of the power system.

[0107] In the embodiment of the present disclosure, the process of constructing the multi-region asynchronous interconnected power grid DC and power supply planning model considering frequency security constraints includes:

[0108] The objective function is constructed with the goal of minimizing the sum of annualized construction cost and annualized operating cost;

[0109] The frequency safety constraints of the AC power grids in each region under DC faults, power flow constraints, power balance constraints of DC lines, line transmission power constraints, power constraints, climbing constraints, minimum start-up and shutdown time constraints, spare capacity constraints, constraints between the start-up and shutdown state variables of the generator to be built and the construction variables, constraints between the operating power of the DC lines to be built and the construction capacity, and constraints on the discrete value of the construction capacity are used as constraint conditions, and combined with the objective function, a DC and power supply planning model for multi-regional asynchronous interconnected power grids considering frequency safety constraints is constructed.

[0110] The objective function is calculated as follows:

[0111]

[0112] Where F is the sum of annual construction cost and annual operation cost. is the annualized construction cost, is the annualized operating cost;

[0113] The calculation formula of the annualized construction cost is as follows:

[0114]

[0115] In the formula, r is the annual interest rate, N is the equipment life, is the set of generators to be built, x g is the value of whether the generator g is put into construction, x g Equal to 0 means no investment, x g Equal to 1 means investment, C g is the construction cost of generator g, is the set of DC lines to be built, For DC line l DC Whether to invest in construction, Equal to 0 means no investment, Equal to 1 means investment and construction, For DC line l DC Fixed construction costs, For DC line l DC The investment capacity, For the DC line l DC Variable construction costs related to construction capacity;

[0116] The annualized operating cost is calculated as follows:

[0117]

[0118] In the formula, To run a set of simulation scenarios, π e is the probability of running simulation scenario e, For the time range within each scene, is the set of all generators, is the power of generator g during period t of running simulation scenario e, is the startup cost of generator g, is the startup indicator variable of generator g in period t of running simulation scenario e, is the shutdown cost of generator g, It is the shutdown indicator variable of generator g during period t of running simulation scenario e.

[0119] It should be noted that for AC systems, power flow constraints need to be met, where represents the sum of the power generated by node p, represents the power load of node p, represents the set of nodes that have AC line connections with node p, Hehe They represent the voltage phase angles at node p and node q, respectively, and X pq represents the equivalent reactance between node p and node q, Indicates the DC line l DC The power injected into node p, represents the set of DC lines connected to node p.

[0120] The calculation formula of the power flow constraint is as follows:

[0121]

[0122] For the DC line, ignoring the loss on the line, the following power balance constraint is satisfied. The calculation formula of the DC line power balance constraint is as follows:

[0123]

[0124] In the formula, represents the set of DC lines between node p and node q;

[0125] For AC and DC lines, the line transmission power constraints need to be met, where Hehe represents the maximum transmission power of AC and DC lines, Indicates AC line l AC The reactance, and They represent the set of AC lines and the set of DC lines between nodes p and q respectively. and represents the power injected into the DC line by nodes p and q, and the calculation formula of the line transmission power constraint is as follows:

[0126]

[0127] For the generator, it is necessary to meet the power constraint, ramp constraint, and minimum start-stop time constraint. Hehe represents the maximum power and minimum power of generator g, and represents the maximum up-slope and down-slope power of the generator g, and represents the minimum start-up time and minimum shutdown time of the generator g, wherein the calculation formulas of the power constraint, the ramp constraint, and the minimum start-up and shutdown time constraint are respectively as follows:

[0128]

[0129] For the generators participating in frequency regulation, the reserve capacity constraint under the maximum frequency deviation needs to be met. The calculation formula of the reserve capacity constraint is as follows:

[0130]

[0131] For the generator to be built, the start and stop state variables must be met With the investment variable x g The constraint between the start-up and shutdown state variables of the generator to be built and the construction variable is calculated as follows:

[0132]

[0133] For the DC lines to be built, their operating power Need to meet the investment and construction capacity The constraint between the running power of the DC line to be built and the construction capacity is calculated as follows:

[0134]

[0135] For the construction capacity of DC lines The constraints of discretization value need to be satisfied, where Indicates the minimum capacity that can be built. Indicates the interval value of the capacity that can be put into construction. is an integer variable, its maximum value is M, and (The DC line is not built) It must be 0. The calculation formula for the constraint of the discretization value of the investment capacity is as follows:

[0136]

[0137] It should be noted that the DC and power planning model for multi-region asynchronous interconnected power grids considering frequency safety constraints is a mixed integer linear programming problem. By calling GUROBI and other optimization problem solving software to solve the optimization model, the DC and power planning scheme for multi-region asynchronous interconnected power grids can be obtained, including the construction scheme of generators, the construction scheme of DC, and the capacity of each DC line. In addition, the unit combination scheduling scheme in the typical operation simulation scenario can be obtained from the solution of the optimization model, including the start and stop status and power of all generator sets in the system, and the transmission power of DC lines. The execution log records and intermediate results of all previous steps are sorted out and stored in the backup database as required for future verification.

[0138] To sum up, the multi-region asynchronous interconnected power grid planning method considering frequency safety constraints proposed in this embodiment can effectively ensure that the DC and power supply planning schemes of the multi-region asynchronous interconnected power grids under a high proportion of new energy access meet the frequency safety requirements, and provide decision support for power system planning.

[0139] Embodiment 2

[0140] Figure 2 The structure diagram of a multi-region asynchronous interconnected power grid planning system considering frequency safety constraints is provided according to an embodiment of the present application, such as Figure 2 As shown, the system comprises:

[0141] An acquisition module 100 is used to acquire frequency response characteristic related parameters and frequency deviation of AC power grids in each region of the power system;

[0142] A determination module 200, configured to determine frequency safety constraints of AC power grids in each region under a DC fault according to frequency response characteristic-related parameters and frequency deviations of the AC power grids in each region of the power system;

[0143] The planning module 300 is used to construct a DC and power supply planning model for a multi-region asynchronous interconnected power grid taking into account frequency safety constraints based on the frequency safety constraints of the AC power grids in each region under the DC fault, and to optimize and solve the planning model using the GUROBI optimizer to obtain DC and power supply planning schemes for the asynchronous interconnected power grids in each region of the power system.

[0144] It should be noted that the frequency response characteristic related parameters include:

[0145] 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.

[0146] In the embodiments of the present disclosure, Figure 3 As shown, the determination module 200 includes:

[0147] The first determination 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 grids in each region based on the frequency response characteristic related parameters of the AC power grids in each region;

[0148] A first construction unit 202 is used to construct an equivalent frequency response model of each regional AC power grid according to an equivalent inertia time constant, a load damping ratio, an equivalent droop control coefficient, an equivalent high-pressure cylinder output ratio, an equivalent reheat time constant and a frequency deviation of each regional AC power grid;

[0149] The calculation formula of the equivalent frequency response model of the AC power grid in each region is as follows:

[0150]

[0151] Where ΔP i (s) is the unbalanced power of regional AC power grid i, H i is the equivalent inertia time constant, s is a complex variable, D i is the load damping ratio, F H，i is the equivalent high-pressure cylinder output ratio, T R，i is the equivalent reheat time constant, R i is the equivalent droop control coefficient, Δf i (s) is the frequency deviation of regional AC power grid i.

[0152] A solving unit 203 is used to solve the time domain solution of the equivalent frequency response model of the AC power grid in each region to obtain the lowest point of the frequency of the AC power grid in each region;

[0153] The second construction unit 204 is used to obtain historical data of the AC power grid in each region, and to construct a data set of the AC power grid in each region based on the lowest point of the frequency of the AC power grid in each region and the historical data;

[0154] The linear fitting unit 205 is used to perform piecewise linear fitting on the equivalent frequency response model of each regional AC power grid based on the data set of each regional AC power grid, and obtain the coefficient and intercept of the piecewise linear fitting of each regional AC power grid;

[0155] The third constructing unit 206 is used to construct frequency safety constraints of the AC power grids in each region under a DC fault based on the coefficients and intercepts of the piecewise linear fitting of the AC power grids in each region.

[0156] The calculation formula of the frequency safety constraint of the AC power grid in each region under the DC fault is as follows:

[0157]

[0158] In the formula, is the transpose of the Kth coefficient vector corresponding to the i-th regional AC power grid, is the frequency characteristic parameter of the AC power grid in the ith region during the period t of the simulation scenario e, β i，k is the kth intercept corresponding to the AC power grid in the ith region, For DC line l DC The power during the period t of the running simulation scenario e, Δf max,i is, K is the number of segments of the linear fitting of the equivalent frequency response model, is the set of DC lines connected to the AC grid in the i-th region.

[0159] In the embodiment of the present disclosure, the planning module 300 is further used for:

[0160] The objective function is constructed with the goal of minimizing the sum of annualized construction cost and annualized operating cost;

[0161] The frequency safety constraints of the AC power grids in each region under DC faults, power flow constraints, power balance constraints of DC lines, line transmission power constraints, power constraints, climbing constraints, minimum start-up and shutdown time constraints, spare capacity constraints, constraints between the start-up and shutdown state variables of the generator to be built and the construction variables, constraints between the operating power of the DC lines to be built and the construction capacity, and constraints on the discrete value of the construction capacity are used as constraint conditions, and combined with the objective function, a DC and power supply planning model for multi-regional asynchronous interconnected power grids considering frequency safety constraints is constructed.

[0162] The objective function is calculated as follows:

[0163]

[0164] Where F is the sum of annual construction cost and annual operation cost. is the annualized construction cost, is the annualized operating cost;

[0165] The calculation formula of the annualized construction cost is as follows:

[0166]

[0167] In the formula, r is the annual interest rate, N is the equipment life, is the set of generators to be built, x g is the value of whether the generator g is put into construction, x g Equal to 0 means no investment, x g Equal to 1 means investment, C g is the construction cost of generator g, is the set of DC lines to be built, For DC line l DC Whether to invest in construction, Equal to 0 means no investment, Equal to 1 means investment and construction, For DC line l DC Fixed construction costs, For DC line l DC The investment capacity, For the DC line l DC Variable construction costs related to construction capacity;

[0168] The annualized operating cost is calculated as follows:

[0169]

[0170] In the formula, To run a set of simulation scenarios, π e is the probability of running simulation scenario e, For the time range within each scene, is the set of all generators, is the power of generator g during period t of running simulation scenario e, is the startup cost of generator g, is the startup indicator variable of generator g in period t of running simulation scenario e, is the shutdown cost of generator g, is the shutdown indicator variable of generator g during period t of running simulation scenario e.

[0171] To sum up, the multi-region asynchronous interconnected power grid planning system considering frequency safety constraints proposed in this embodiment can effectively ensure that the DC and power supply planning schemes of the multi-region asynchronous interconnected power grids under a high proportion of new energy access meet the frequency safety requirements, and provide decision support for power system planning.

[0172] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0173] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0174] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A multi-region asynchronous interconnected power grid planning method considering frequency security constraints, characterized in that: The method comprises: Obtain frequency response characteristic related parameters and frequency deviation of AC power grid in each area of ​​power system; Determine frequency safety constraints of AC power grids in each region under DC faults according to frequency response characteristic related parameters and frequency deviation of AC power grids in each region of the power system; Taking the frequency safety constraints of the AC power grids in each region under the DC fault as constraints, a DC and power supply planning model for multi-regional asynchronous interconnected power grids considering frequency safety constraints is constructed, and the planning model is optimized and solved using the GUROBI optimizer to obtain the DC and power supply planning schemes for the asynchronous interconnected power grids in each region of the power system.

2. The method according to claim 1, characterized in that The frequency response characteristic 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 according to claim 2, characterized in that The determining of frequency safety constraints of AC power grids in each region under a DC fault according to frequency response characteristic related parameters and frequency deviation of AC power grids in each region of the power system includes: 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 grids in each region based on the frequency response characteristic related parameters of the AC power grids in each region; Constructing an equivalent frequency response model of each regional AC power grid according to 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 each regional AC power grid; Solve the time domain solution of the equivalent frequency response model of the AC power grid in each region to obtain the lowest point of the frequency of the AC power grid in each region; Acquire historical data of AC power grids in each region, and construct data sets of AC power grids in each region based on the lowest point of the frequency of the AC power grids in each region and the historical data; Based on the data sets of the AC power grids in each region, piecewise linear fitting is performed on the equivalent frequency response model of the AC power grids in each region, and coefficients and intercepts of the piecewise linear fitting of the AC power grids in each region are obtained; Based on the coefficients and intercepts of the piecewise linear fitting of the AC power grid in each region, the frequency security constraints of the AC power grid in each region under DC faults are constructed.

4. The method according to claim 3, characterized in that The calculation formula of the equivalent frequency response model of the AC power grid in each region is as follows: In the formula, ΔP i (s) is the unbalanced power of regional AC power grid i, H i is the equivalent inertia time constant, s is a complex variable, D i is the load damping ratio, F H,i is the equivalent high-pressure cylinder output ratio, T R,i is the equivalent reheat time constant, R i is the equivalent droop control coefficient, Δf i (s) is the frequency deviation of regional AC power grid i.

5. The method according to claim 4, characterized in that The calculation formula for the frequency safety constraint of the AC power grid in each region under the DC fault is as follows: In the formula, is the transpose of the Kth coefficient vector corresponding to the i-th regional AC power grid, is the frequency characteristic parameter of the AC power grid in the ith region during the period t of the simulation scenario e, β i,k is the kth intercept corresponding to the AC power grid in the ith region, For DC line l DC The power during the period t of the running simulation scenario e, Δf max,i is, K is the number of segments of the linear fitting of the equivalent frequency response model, is the set of DC lines connected to the AC grid in the i-th region.

6. The method according to claim 5, characterized in that The construction process of the multi-region asynchronous interconnected power grid DC and power supply planning model 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 frequency safety constraints of the AC power grids in each region under DC faults, power flow constraints, power balance constraints of DC lines, line transmission power constraints, power constraints, climbing constraints, minimum start-up and shutdown time constraints, spare capacity constraints, constraints between the start-up and shutdown state variables of the generator to be built and the construction variables, constraints between the operating power of the DC lines to be built and the construction capacity, and constraints on the discrete value of the construction capacity are used as constraint conditions, and combined with the objective function, a DC and power supply planning model for multi-regional asynchronous interconnected power grids considering frequency safety constraints is constructed.

7. The method according to claim 6, characterized in that The objective function is calculated as follows: Where F is the sum of annual construction cost and annual operation cost. is the annualized construction cost, is the annualized operating cost; The calculation formula of the annualized construction cost is as follows: In the formula, r is the annual interest rate, N is the equipment life, is the set of generators to be built, x g is the value of whether the generator g is put into construction, x g Equal to 0 means no investment, x g Equal to 1 means investment, C g is the construction cost of generator g, is the set of DC lines to be built, For DC line l DC Whether to invest in construction, Equal to 0 means no investment, Equal to 1 means investment and construction, For DC line l DC Fixed construction costs, For DC line l DC The investment capacity, For the DC line l DC Variable construction costs related to construction capacity; The annualized operating cost is calculated as follows: In the formula, To run a set of simulation scenarios, π e is the probability of running simulation scenario e, For the time range within each scene, is the set of all generators, is the power of generator g during period t of running simulation scenario e, is the startup cost of generator g, is the startup indicator variable of generator g in period t of running simulation scenario e, is the shutdown cost of generator g, is the shutdown indicator variable of generator g during period t of running simulation scenario e.

8. A multi-region asynchronous interconnected power grid planning system considering frequency security constraints, characterized in that: The system comprises: An acquisition module is used to obtain frequency response characteristic related parameters and frequency deviation of AC power grids in various regions of the power system; A determination module, used to determine the frequency safety constraints of the AC power grids in each region under a DC fault according to the frequency response characteristic related parameters and frequency deviation of the AC power grids in each region of the power system; The planning module is used to construct a DC and power supply planning model for multi-region asynchronous interconnected power grids considering frequency safety constraints based on the frequency safety constraints of the AC power grids in each region under the DC fault, and use the GUROBI optimizer to optimize and solve the planning model to obtain the DC and power supply planning schemes for the asynchronous interconnected power grids in each region of the power system.

9. The system according to claim 8, characterized in that The frequency response characteristic 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 according to claim 9, characterized in that The determining module comprises: A first determination unit is used to determine an equivalent inertia time constant, a load damping ratio, an equivalent droop control coefficient, an equivalent high-pressure cylinder output ratio, and an equivalent reheat time constant of the AC power grids in each region based on frequency response characteristic related parameters of the AC power grids in each region; A first construction unit is used to construct an equivalent frequency response model of each regional AC power grid according to an equivalent inertia time constant, a load damping ratio, an equivalent droop control coefficient, an equivalent high-pressure cylinder output ratio, an equivalent reheat time constant and a frequency deviation of each regional AC power grid; A solving unit, used for solving the time domain solution of the equivalent frequency response model of the AC power grid in each region, and obtaining the lowest point of the frequency of the AC power grid in each region; A second construction unit is used to obtain historical data of the AC power grid in each region, and to construct a data set of the AC power grid in each region based on the lowest point of the frequency of the AC power grid in each region and the historical data; A linear fitting unit is used to perform piecewise linear fitting on an equivalent frequency response model of each regional AC power grid based on a data set of each regional AC power grid, so as to obtain coefficients and intercepts of the piecewise linear fitting of each regional AC power grid; The third construction unit is used to construct frequency safety constraints of the AC power grids in each region under a DC fault based on coefficients and intercepts of the piecewise linear fitting of the AC power grids in each region.

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