Methods, apparatus and equipment for assessing the maximum DC transmission capacity of asynchronous interconnected power grids

Abstract

This invention provides a method, apparatus, and equipment for assessing the maximum DC transmission capacity of asynchronous interconnected power grids, relating to the field of power system operation and control technology. The method includes: substituting the frequency regulation segmented response model of each type of frequency regulation resource into the frequency dynamic swing equation and integrating; converting the integral of each frequency regulation segmented response model in the integration result into the product of the frequency regulation reserve capacity and intermediate parameters of that type of frequency regulation resource, obtaining an algebraic mapping of linear form between the disturbance and frequency deviation in the DC maximum transmission capacity assessment, denoted as the frequency deviation analytical expression; performing a discretized linear transformation of the frequency deviation analytical expression to obtain the frequency safety constraint; based on the frequency safety constraint, constructing and solving an optimization model with the maximum DC transmission capacity as the objective function to obtain the DC maximum transmission capacity assessment result. This invention enables more accurate and efficient assessment of the maximum DC transmission capacity of existing asynchronous interconnected power grids.

Description

Technical Field

[0001] This invention relates to the field of power system operation and control technology, and in particular to a method, apparatus and equipment for evaluating the maximum DC transmission capacity of asynchronous interconnected power grids. Background Technology

[0002] Asynchronous interconnected power grids are a type of power system that interconnects two or more independent synchronous power grids through power electronic converters. Their core characteristic is that there are no electrical synchronization frequency constraints between the interconnected synchronous power grids; each grid can maintain its rated power and phase angle independently, and power exchange is entirely regulated by power electronic devices. With the deepening development of power systems, asynchronous interconnected power grids have become a key form supporting regional energy consumption. The total transfer capacity (TTC) of an asynchronous interconnected power grid is a core indicator for measuring its inter-regional power transmission capacity and a crucial basis for grid dispatching in formulating inter-regional plans and controlling safety margins. Therefore, the assessment of the total transfer capacity is essential for the safe and economical operation of the power grid.

[0003] In existing technologies, the assessment of the maximum DC transmission capacity of asynchronous interconnected power grids is based on static security constraints, such as thermal stability and voltage limits. This ignores the dynamic frequency instability risks faced by asynchronous interconnected power grids under low-inertia operation when subjected to large disturbances (such as DC blocking or generator disconnection). This leads to overly optimistic assessment results, resulting in instability risks in TTC (Transmission Control Charge) assessments. Furthermore, the dynamic evolution of frequency in dynamic frequency security is a nonlinear differential process, which cannot be directly embedded into large-scale optimization models, making the assessment process inefficient. Simultaneously, the frequency regulation characteristics of heterogeneous resources such as thermal power, wind power, and energy storage within the system differ significantly. Existing single-modeling methods cannot accurately characterize the frequency evolution process under complex disturbances, nor can they realistically simulate the multi-inflection-point frequency evolution trajectory of asynchronous power grids under large disturbances. This results in TTC assessment values ​​that do not conform to the actual operating patterns of the power grid, leading to inaccurate assessment results. Summary of the Invention

[0004] This invention provides a method, apparatus, and equipment for evaluating the maximum DC transmission capacity of asynchronous interconnected power grids, in order to solve the problems of inaccurate evaluation and inefficient evaluation process of existing asynchronous interconnected power grids.

[0005] In a first aspect, embodiments of the present invention provide a method for evaluating the maximum DC transmission capacity of asynchronous interconnected power grids, including: Substituting the frequency modulation segmented response model of each type of frequency modulation resource in the target asynchronous interconnected power grid into the frequency dynamic swing equation and integrating, the integral of each frequency modulation segmented response model in the integration result is converted into the form of the product of the frequency modulation reserve capacity and intermediate parameters of that type of frequency modulation resource. This yields an algebraic mapping of the linear form between the disturbance and frequency deviation in the DC maximum transmission capacity assessment, denoted as the frequency deviation analytical expression. The intermediate parameters are obtained based on the dead time and ramp-up time of that type of frequency modulation resource. The frequency deviation analytical expression is subjected to a discretized linear transformation to obtain the frequency safety constraint by the minimum frequency point constraint; Based on the frequency security constraints, an optimization model with the maximum DC transmission capacity as the objective function is constructed and solved to obtain the evaluation result of the maximum DC transmission capacity of the target asynchronous interconnected power grid.

[0006] In one possible implementation, the process of constructing the frequency modulation segmented response model for each type of frequency modulation resource includes: Obtain the dead time, ramp time, and frequency regulation reserve capacity of each type of frequency regulation resource in the target asynchronous interconnected power grid; Based on the dead time, the ramp time, and the frequency modulation reserve capacity, a frequency modulation segmented response model is constructed for each type of frequency modulation resource.

[0007] In one possible implementation, the intermediate parameter is: ; in, For the first i Intermediate parameters for this type of frequency modulation resource. τ For time variables, For the first i Dead time of various types of frequency modulation resources For the first i The ramp-up time for various types of FM resources This is the positive value operator.

[0008] In one possible implementation, the frequency deviation analytical expression is: ; in, For frequency deviation, The system's rated frequency, Let be the system's equivalent inertia constant. For the first i Frequency modulation reserve capacity of various types of frequency modulation resources This is the disturbance quantity used in the assessment of maximum DC transmission capacity. J This represents the total number of types of frequency modulation resources.

[0009] In one possible implementation, the minimum frequency constraint includes a maximum allowable frequency deviation, which is the difference between the rated frequency and the minimum frequency limit. A discretized linear transformation of the analytical expression of the minimum frequency constraint yields a frequency safety constraint, including: By setting the frequency deviation analytical expression to be less than or equal to the maximum allowable frequency deviation, a linear inequality constraint is obtained. During a single frequency modulation period, the linear inequality constraints are sampled according to a preset sampling step size to obtain several linear inequalities, which serve as frequency security constraints.

[0010] In one possible implementation, the frequency security constraint is: ; in, For the first i Intermediate parameters for this type of frequency modulation resource. τ For time variables, The system's rated frequency, Let be the system's equivalent inertia constant. For the first i Frequency modulation reserve capacity of various types of frequency modulation resources This is the disturbance quantity used in the assessment of maximum DC transmission capacity. J The total number of FM resource types. To allow the maximum frequency deviation, k For sampling sequences, , N The total number of frequency security constraints. This is the sampling step size.

[0011] In one possible implementation, after obtaining the frequency security constraints, the following is also included: Based on the target asynchronous interconnected power grid parameters, construct resource operation constraints and DC linearity constraints; Based on the aforementioned frequency security constraints, an optimization model is constructed and solved with the objective function of maximizing DC transmission capacity. The resulting evaluation of the maximum DC transmission capacity of the target asynchronous interconnected power grid is obtained, including: Based on the frequency security constraints, resource operation constraints, and DC linear constraints, an optimization model is constructed with the maximum DC transmission capacity as the objective function. The optimization model is input with the load forecast of the target asynchronous interconnected power grid and the predicted operation of each frequency regulation resource. The model is solved with the coordinated frequency regulation output of each frequency regulation resource and the optimal start-up and shutdown of the units as variables to obtain the evaluation result of the maximum DC transmission capacity of the target asynchronous interconnected power grid.

[0012] In one possible implementation, the process of constructing the DC linear constraint includes: The first set of binary variables is introduced to limit the boundaries of forward and reverse power transmission, thereby obtaining DC output constraints; A second set of binary variables is introduced to represent the upward and downward adjustment of DC power, thereby obtaining the DC regulation action constraint; A third set of binary variables is introduced to record the switching of power flow direction, thereby obtaining the constraint on the number of power flow reversals.

[0013] Secondly, embodiments of the present invention provide a device for evaluating the maximum DC transmission capacity of an asynchronous interconnected power grid, comprising: The frequency regulation resource equivalent modeling module is used to substitute the frequency regulation segment response model of each type of frequency regulation resource in the target asynchronous interconnected power grid into the frequency dynamic swing equation and then integrate it. The integral of each frequency regulation segment response model in the integration result is converted into the form of the product of the frequency regulation reserve capacity and intermediate parameters of the frequency regulation resource of that type. This yields an algebraic mapping in linear form between the disturbance and frequency deviation in the DC maximum transmission capacity assessment, denoted as the frequency deviation analytical expression. The intermediate parameters are obtained based on the dead time and ramp-up time of the frequency regulation resource of that type. The frequency safety constraint generation module is used to perform a discretization linear transformation on the frequency deviation analytical expression to obtain the frequency safety constraint; The optimization solution and evaluation module is used to construct and solve an optimization model with the maximum DC transmission capacity as the objective function based on the frequency security constraints, and obtain the evaluation result of the maximum DC transmission capacity of the target asynchronous interconnected power grid.

[0014] Thirdly, embodiments of the present invention provide an asynchronous interconnected power grid DC maximum transmission capacity assessment device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the method described in the first aspect or any possible implementation of the first aspect.

[0015] In this embodiment of the invention, the frequency regulation segmented response model of each type of frequency regulation resource in the target asynchronous interconnected power grid is substituted into the frequency dynamic swing equation and integrated. The integral of each frequency regulation segmented response model in the integration result is converted into the product of the frequency regulation reserve capacity and intermediate parameters of that type of frequency regulation resource to obtain the frequency deviation analytical expression. The frequency deviation analytical expression is then discretized by performing a frequency minimum point constraint to obtain the frequency security constraint. On the one hand, the frequency regulation segmented response model of each segment form is used to accurately characterize the cooperative frequency support characteristics of different types of frequency regulation resources, avoiding the TTC evaluation error caused by the oversimplification of the response model of the frequency regulation resource, and making the TTC evaluation value more consistent with the actual operation law of the power grid. Based on this, through integration, transformation of partial integrals in the integration results, and discretization, the original infinite-dimensional, nonlinear differential equation constraints (i.e., the minimum frequency point constraint of the frequency deviation analytical expression) are cleverly transformed into a finite-dimensional set of linear algebraic inequalities (i.e., frequency safety constraints). This transforms complex dynamic frequency constraints into linear algebraic constraints that can be directly processed by linear optimization solvers, thereby significantly improving the computational efficiency and practicality of DC maximum transmission capacity assessment for asynchronous interconnected power grids in complex power grid environments. Moreover, by explicitly introducing frequency safety constraints, when constructing optimization models based on frequency safety constraints and solving for DC maximum transmission capacity assessment results, it is possible to automatically identify and avoid operating ranges that may cause frequency collapse, ensuring that frequency deviation remains within safe limits under anticipated disturbances (such as DC blocking), thereby maintaining system frequency stability. Attached Figure Description

[0016] Figure 1 This is an application scenario diagram of the asynchronous interconnected power grid DC maximum transmission capacity assessment method provided in the embodiments of the present invention; Figure 2 This is a flowchart illustrating the implementation of the asynchronous interconnected power grid DC maximum transmission capacity assessment method provided in this embodiment of the invention. Figure 3 This is a flowchart illustrating the implementation of the method for evaluating the maximum DC transmission capacity of an asynchronous interconnected power grid based on thermal power generating units, wind power generating units, and energy storage systems, as provided in this embodiment of the invention. Figure 4 This is a hardware architecture diagram of the method for evaluating the maximum DC transmission capacity of an asynchronous interconnected power grid based on thermal power generator sets, wind power generator sets, and energy storage systems, provided in an embodiment of the present invention. Figure 5 This is a schematic diagram of the structure of the asynchronous interconnected power grid DC maximum transmission capacity assessment device provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the asynchronous interconnected power grid DC maximum transmission capacity assessment device provided in an embodiment of the present invention. Detailed Implementation

[0017] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0018] Figure 1 This diagram illustrates an application scenario of the asynchronous interconnected power grid DC maximum transmission capacity assessment method provided in this embodiment of the invention. The asynchronous interconnected power grid DC maximum transmission capacity assessment method is applied to the dispatch decision center of the interconnected power grid, and the physical and logical architecture of the dispatch decision center is as follows: Figure 1 As shown, it includes: Physical layer: Used to asynchronously connect the sending-end power grid and the receiving-end power grid through multiple high-voltage direct current (HVDC) transmission channels; the receiving-end power grid includes thermal power units (including frequency regulators), wind farms, energy storage power stations, and various loads.

[0019] Data acquisition and monitoring layer: used to collect key operating data of each unit and the power grid in real time.

[0020] Core algorithm layer: Deployed on the scheduling server, including frequency modulation resource equivalent modeling module, frequency security constraint generation module, optimization solution module, etc.

[0021] Output layer: Provides real-time feedback to the dispatcher on 24-hour DC TTC limits and optimized start-up and shutdown plans for the generating units.

[0022] The application scenarios of the asynchronous interconnected power grid DC maximum transmission capacity assessment method provided in this invention include: Scenario 1: Formulation of day-ahead / weekly inter-regional power trading plans. The auxiliary dispatch center optimizes DC transmission power to maximize the absorption of inter-provincial resources while meeting frequency safety boundaries.

[0023] Scenario 2: System stability assessment under high-proportion renewable energy access. To address the randomness of renewable energy output fluctuations, the limit of DC power transmission is calculated dynamically in real time to prevent the risk of frequency collapse due to insufficient inertia.

[0024] Scenario 3: Preventive control under power grid emergency conditions. Before a anticipated accident (such as large-capacity unit disconnection or DC blockage) occurs, preventive power reserves are made on the load side or DC side based on the safe capacity value calculated by this invention.

[0025] See Figure 2 The document illustrates a flowchart of the implementation of the asynchronous interconnected power grid DC maximum transmission capacity assessment method provided in this embodiment of the invention, which is described in detail below: Step 201: Substitute the frequency regulation segment response model of each type of frequency regulation resource in the target asynchronous interconnected power grid into the frequency dynamic swing equation and integrate. Then, convert the integral of each frequency regulation segment response model in the integration result into the form of the product of the frequency regulation reserve capacity and intermediate parameters of that type of frequency regulation resource. This yields an algebraic mapping of the linear form between the disturbance and frequency deviation in the DC maximum transmission capacity assessment, denoted as the frequency deviation analytical expression. The intermediate parameters are obtained based on the dead time and ramp-up time of that type of frequency regulation resource.

[0026] In one embodiment, the process of constructing the frequency modulation segmented response model for each type of frequency modulation resource includes: Obtain the dead time, ramp time, and frequency regulation reserve capacity of each type of frequency regulation resource in the target asynchronous interconnected power grid.

[0027] Based on dead time, ramp time, and FM reserve capacity, construct a segmented response model for each type of FM resource.

[0028] Among them, ramp time is the time required for FM resources to go from responding to FM commands to reaching maximum FM reserve power. It is the core time parameter that characterizes the FM response speed of resources and directly determines how quickly FM resources can be put into frequency support after a disturbance.

[0029] In this embodiment, the frequency modulation segmented response model of the frequency modulation resource is as follows: ; Substituting the frequency modulation segmented response model of the above frequency modulation resources into the following frequency dynamic swing equation: ; By integrating the frequency dynamic swing equation of the frequency modulation segmented response model substituted with the frequency modulation resources, the analytical expression of frequency deviation is obtained. The integral of each frequency modulation segmented response model in the integration result is in the form of the product of the frequency modulation reserve capacity and intermediate parameters of that type of frequency modulation resource. ; The intermediate parameters are: ; in, τ For time variables, For the first i Dead time of various types of frequency modulation resources For the first i The ramp-up time for various types of FM resources For the first i The power increment of this type of frequency modulation resource For the first i Intermediate parameters for this type of frequency modulation resource. For positive value operators, For frequency deviation, The system's rated frequency, Let be the system's equivalent inertia constant. For the first i Frequency modulation reserve capacity of various types of frequency modulation resources This is the disturbance quantity used in the assessment of maximum DC transmission capacity. J This represents the total number of types of frequency modulation resources.

[0030] Step 202: Perform a discretization linear transformation on the frequency deviation analytical expression to obtain the frequency safety constraint.

[0031] In one embodiment, the minimum frequency constraint includes the maximum allowable frequency deviation, which is the difference between the rated frequency and the minimum frequency limit. The frequency deviation is set to be less than or equal to the maximum allowable frequency deviation to obtain a linear inequality constraint. During one frequency modulation time, the linear inequality constraint is sampled according to a preset sampling step size to obtain several linear inequalities as frequency safety constraints.

[0032] In this embodiment, the frequency security constraint is: ; in, To allow the maximum frequency deviation, k For sampling sequences, , N The total number of frequency security constraints. This is the sampling step size.

[0033] Step 203: Based on frequency security constraints, construct and solve an optimization model with the maximum DC transmission capacity as the objective function to obtain the evaluation result of the maximum DC transmission capacity of the target asynchronous interconnected power grid.

[0034] In one embodiment, after obtaining the frequency security constraints, the method further includes: Based on the target asynchronous interconnected power grid parameters, resource operation constraints and DC linear constraints are constructed.

[0035] Based on frequency security constraints, resource operation constraints, and DC linear constraints, an optimization model is constructed with the maximum DC transmission capacity as the objective function.

[0036] The optimization model is input with the load forecast of the target asynchronous interconnected power grid and the predicted operation of each frequency regulation resource. The model is solved with the coordinated frequency regulation output of each frequency regulation resource and the optimal start-up and shutdown of the units as variables to obtain the evaluation result of the maximum DC transmission capacity of the target asynchronous interconnected power grid.

[0037] In this embodiment, the process of constructing the DC linear constraint includes: The first set of binary variables is introduced to limit the boundaries of forward and reverse power transmission, thus obtaining DC output constraints.

[0038] A second set of binary variables is introduced to represent the upward and downward adjustment of DC power, thereby obtaining the DC regulation action constraint.

[0039] A third set of binary variables is introduced to record the switching of power flow direction, thereby obtaining the constraint on the number of power flow reversals.

[0040] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0041] The following specific embodiments illustrate the method for evaluating the maximum DC transmission capacity of asynchronous interconnected power grids provided by the present invention: In this embodiment, the frequency regulation resources are thermal power generator sets, wind power generator sets, and energy storage systems.

[0042] like Figure 3 As shown, the method for assessing the maximum DC transmission capacity of an asynchronous interconnected power grid based on thermal power generating units, wind power generating units, and energy storage systems specifically includes the following steps: S1. Construct a refined piecewise linear function of the frequency modulation response of heterogeneous resources (i.e., frequency modulation resources) such as fire-wind-storage.

[0043] For frequency regulation resources with three different characteristics in the receiving-end power grid, dead time is introduced. Climbing time and frequency modulation reserve capacity Establish the following specific power output function. (Among them, the frequency regulation resources of thermal power generating units are defined as the first type of frequency regulation resources, i.e.) i =1, subscript is G ; Define the frequency regulation resources of wind turbine generators as the second type of frequency regulation resources, that is i =2, subscript is W The frequency regulation resources of the energy storage system are defined as the third type of frequency regulation resources, namely... i =3, subscript is E ): S11 constructs a segmented response model for frequency regulation of thermal power generating units.

[0044] Obtaining the dead time of frequency regulation in thermal power plants Thermal power plant frequency regulation ramp-up time and thermal power frequency regulation reserve capacity Thermal power frequency regulation power increment Depicted in the following three stages: Thermal power frequency regulation response delay stage: when the frequency drop begins At that time, the frequency regulation power increment of thermal power plants =0; Thermal power plant frequency regulation linear ramp-up stage: when At that time, the power increment increases at a constant slope, and the frequency regulation power increment of thermal power plants... ; Thermal power frequency regulation power maintenance phase: when At that time, the frequency regulation power increment of thermal power plants Reaching the reserve capacity of thermal power frequency regulation .

[0045] S12 constructs a segmented response model for frequency regulation of wind turbine generators (including virtual inertia and speed recovery).

[0046] Obtaining wind power response dead time Wind power ramp-up time (Used to characterize the duration of virtual inertia support) and wind power frequency regulation reserve capacity Wind power frequency regulation power increment Depicted in the following three stages: Phase 1 (Quiet Period): When hour, ; Phase Two (Virtual Inertia Support): When At that time, the wind power frequency regulation power increment is calculated according to Linear injection to simulate the wind kinetic energy release process; Phase Three (Backup Support / Speed ​​RPM Restoration and Balance): At that time, the increase in wind power frequency regulation Maintain as This characterizes the equilibrium state between the speed recovery period and the system support.

[0047] S13 constructs a frequency regulation segmented response model for energy storage systems (fast frequency support).

[0048] Obtaining the ultra-fast response dead time of energy storage Energy storage full-power response time and backup energy storage systems Energy storage system power increment Expressed as: when hour, ; when hour, ; when hour, .

[0049] S2. Substitute the power output of heterogeneous resources (frequency-modulated resources) into the swing equation describing the frequency dynamics of the power system: ; Define intermediate parameters for thermal power plants Wind power intermediate parameters and intermediate parameters of energy storage They are defined as follows: ; ; ; By integrating the swing equation using this definition, we obtain the system frequency deviation Δ in linear form. f ( τ Analytical expression: ; This analytical expression establishes the perturbation in the assessment of maximum DC transmission capacity. A direct algebraic mapping between frequency deviation and frequency offset.

[0050] S3. Perform a discretization linear transformation on the frequency deviation analytical expression to obtain the frequency safety constraint by the frequency nadir (FN) constraint.

[0051] Regarding the time variable in the analytical expression For problems where continuity prevents the model from being solved directly, the following specific transformation steps should be performed: S31 determines the sampling space: sets the sampling period to the entire frequency modulation process (e.g., 10s), and sets the sampling step size. Generate sampling sequence .

[0052] S32 constructs a set of linear security constraints: for each sampling time... A linear inequality constraint is generated based on the analytical expression of S2. The frequency deviation of the system at any sampling point is required to satisfy: ; This collection contains These linear inequalities together constitute the dynamic frequency safety boundary that limits the maximum DC transmission capacity.

[0053] S4. Construct a frequency-constrained total transfer capacity (FC-TTC) mixed-integer linear programming optimization model and resource operation constraints.

[0054] Based on the topology and resource allocation of the receiving-end power grid, an optimization model is constructed with the goal of maximizing DC transmission capacity and including the operating boundaries of various frequency regulation resources.

[0055] S41 defines the evaluation objective function of the optimization model.

[0056] The objective function is set as the DC channel within a preset scheduling period (e.g., 24 hours, with a step size of 1 hour). Maximize the net cumulative amount of power transferred in both the forward (from grid 1 to grid 2) and reverse (from grid 2 to grid 1) directions. Its mathematical expression is defined as: ; in, t For time period index, T Let ΘH be the set of time periods within the scheduling cycle, and let ΘH be the sum of all DC channels within the system. For the time period t DC channel h The active power transmitted in the forward direction, that is, the power flowing from grid 1 to grid 2. For the time period t DC channel h The active power transmitted in the reverse direction is the power flowing from grid 2 to grid 1.

[0057] S42 establishes start-up and shutdown and technical constraints for thermal power units.

[0058] State logic constraints: Introduce binary state variables Indicates the unit's online status and defines the startup variables. With shutdown variables Establish an equation to characterize the state transition logic: ; Minimum start / stop time constraint: Introducing an on / off parameter and related parameters By time period The sequence of startup variables within the unit is summed to ensure that once the unit is started or shut down, the time it maintains this state is not less than the minimum start / stop limit.

[0059] Output limits and ramp-up constraints: Setting the active power output of the generator unit With primary frequency regulation reserve capacity The sum must not exceed the maximum output. At the same time, the change in active power output between adjacent time periods must not exceed the unit's ramp rate limit. and landslide rate limits .

[0060] S43 establishes constraints for the energy storage system's power evolution model.

[0061] Power balance constraint: Introducing state variables express The State of Charge (SOC) of stored energy at the end of the time period. Its evolution logic is defined as follows: ; in, For charging and discharging efficiency, This is the charging status item (1 for charging, 0 for not charging). For energy storage power stations during time periods t The charging power, This is the discharge status item (1 indicates discharge in progress, 0 indicates no discharge). For energy storage power stations during time periods t The discharge power.

[0062] Charge / discharge mutual exclusion logic: Introduce charge / discharge binary variables and Through constraints Ensure that the energy storage system can only be in one of the following states at any given time: charging, discharging, or resting.

[0063] S44 establishes AC line transmission limit constraints.

[0064] Using a DC power flow model, the power transfer distribution factor (PTDF) parameters of various power sources and DC nodes to AC line l are obtained. The required power flow (i.e., the power injected into each node and the corresponding power) of line l is to be determined. The sum of the products of all three (the products of the two products) is always within the thermal stability limit of the line. Within the range, among which, For communication lines l The maximum permissible transmission power.

[0065] Under the premise of meeting frequency safety boundaries, by jointly optimizing unit start-up and shutdown, energy storage capacity and AC line transmission limits, the potential of DC transmission channels can be tapped, providing more reasonable and reliable technical support for the formulation of inter-regional power trading plans.

[0066] S5. Perform linearization (DC linear constraint) and optimization model solution for HVDC multi-operation mode logic.

[0067] To address the nonlinear logic arising from the flexible adjustment characteristics of the DC channel, the Big-M method is used for equivalent linearization transformation, and the final calculation is then completed. S51 DC transmission direction and limit linearization.

[0068] Introducing the first group of binary variables: positive binary variables With reverse binary variable .

[0069] Limiting DC output through linear constraints: for example, forward power transmission. The lower bound constraint must be satisfied. and upper limit constraints .when At that time, the positive power is forcibly reduced to zero. Among them, DC channel h The minimum forward transmission power, DC channel h The maximum forward transmission power.

[0070] Logic activation of S52 DC power regulation action (implemented using Big-M technology).

[0071] Introducing a second set of binary variables: Up-regulating binary variables and down-adjusting binary variables These represent the upward and downward adjustment actions of DC power, respectively.

[0072] Minimum adjustment range constraint: Establish the following linearized inequality: ; in, It is a very large constant (e.g., 10000). When the DC performs an upward adjustment ( When this condition is met, the constraint takes effect, forcing the DC regulation value to be no less than that of the DC channel. h Minimum regulating power When the action is not performed ( When the constraint passes Automatic relaxation.

[0073] S53 operating frequency and power flow reversal number limitations.

[0074] Inverted logic definition: Introducing a third set of binary variables Recording time period compared to Has a shift in the trend direction occurred?

[0075] Number of occurrences constraint: For all [events] within the scheduling period and moderating variables The sums are calculated separately, and the total is limited to the preset maximum number of adjustments. and the total maximum allowable adjustment range This is to reduce mechanical wear and operational shocks on converter station equipment.

[0076] The final solution for the S54 optimization model was obtained.

[0077] The frequency security constraints generated by S3, the resource operation constraints generated by S4, and the DC linear constraints generated by S5 are combined to form a standard mixed integer linear programming (MILP) optimization model.

[0078] Input the initial data, which includes load forecasting, wind power output forecasting, and heterogeneous frequency regulation (three types of frequency regulation resources) parameters, into the Gurobi or CPLEX optimization solver.

[0079] Output results: The solver outputs a DC TTC evaluation curve that satisfies the frequency safety of each dynamic sampling point for 24 hours (the frequency change rate and the lowest frequency point are both within the safety threshold), a coordinated frequency regulation output plan for each resource, and the optimal start-up and shutdown scheme for the unit.

[0080] In this embodiment, the hardware architecture diagram for implementing the above-mentioned asynchronous interconnected power grid DC maximum transmission capacity assessment method is shown below. Figure 4 As shown.

[0081] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above.

[0082] Figure 5 A schematic diagram of the asynchronous interconnected power grid DC maximum transmission capacity assessment device provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below: like Figure 5 As shown, the asynchronous interconnected power grid DC maximum transmission capacity assessment device 5 includes: The frequency regulation resource equivalent modeling module 501 is used to substitute the frequency regulation segment response model of each type of frequency regulation resource in the target asynchronous interconnected power grid into the frequency dynamic swing equation and then integrate it. The integral of each frequency regulation segment response model in the integration result is converted into the product of the frequency regulation reserve capacity and intermediate parameters of the frequency regulation resource of that type. This yields an algebraic mapping of the linear form between the disturbance and the frequency deviation in the DC maximum transmission capacity assessment, denoted as the frequency deviation analytical expression. The intermediate parameters are obtained based on the dead time and ramp-up time of the frequency regulation resource of that type.

[0083] The frequency safety constraint generation module 502 is used to perform a discretization linear transformation on the frequency deviation analytical expression to obtain the frequency safety constraint.

[0084] The optimization solution and evaluation module 503 is used to construct and solve an optimization model based on frequency security constraints, with the maximum DC transmission capacity as the objective function, to obtain the evaluation result of the maximum DC transmission capacity of the target asynchronous interconnected power grid.

[0085] Figure 6This is a schematic diagram of an electronic device provided in an embodiment of the present invention. For example... Figure 6 As shown, the asynchronous interconnected power grid DC maximum transmission capacity assessment device 6 of this embodiment includes a processor 60 and a memory 61. The memory 61 stores a computer program 62. When the processor 60 executes the computer program 62, it implements the steps in the above-described method embodiments. Alternatively, when the processor 60 executes the computer program 62, it implements the functions of each module / unit in the above-described device embodiments.

[0086] For example, computer program 62 may be divided into one or more modules / units, which are stored in memory 61 and executed by processor 60 to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of computer program 62 in electronic device 6.

[0087] Electronic device 6 may include, but is not limited to, processor 60 and memory 61. Those skilled in the art will understand that... Figure 6 This is merely an example of electronic device 6 and does not constitute a limitation on electronic device 6. It may include more or fewer components than shown, or combine certain components, or different components. For example, electronic device 6 may also include input / output devices, network access devices, buses, etc.

[0088] For the sake of simplicity and clarity, only the above-described functional modules / units are used as examples. In practical applications, the functions described above can be assigned to different functional modules / units as needed. These modules / units can be implemented in hardware, software, or a combination of both.

[0089] In the above embodiments, the descriptions of each embodiment have their own emphasis. Parts not detailed or described in a particular embodiment can be referred to in the relevant descriptions of other embodiments. Unless otherwise specified or in conflict with logic, the terminology and / or descriptions between different embodiments are consistent and can be referenced interchangeably. Technical features in different embodiments can be combined to form new embodiments based on their inherent logical relationships.

[0090] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for evaluating the maximum DC transmission capacity of an asynchronous interconnected power grid, characterized in that, include: Substituting the frequency modulation segmented response model of each type of frequency modulation resource in the target asynchronous interconnected power grid into the frequency dynamic swing equation and integrating, the integral of each frequency modulation segmented response model in the integration result is converted into the form of the product of the frequency modulation reserve capacity and intermediate parameters of that type of frequency modulation resource. This yields an algebraic mapping of the linear form between the disturbance and frequency deviation in the DC maximum transmission capacity assessment, denoted as the frequency deviation analytical expression. The intermediate parameters are obtained based on the dead time and ramp-up time of that type of frequency modulation resource. The frequency deviation analytical expression is subjected to a discretized linear transformation to obtain the frequency safety constraint by the minimum frequency point constraint; Based on the frequency security constraints, an optimization model with the maximum DC transmission capacity as the objective function is constructed and solved to obtain the evaluation result of the maximum DC transmission capacity of the target asynchronous interconnected power grid.

2. The method for evaluating the maximum DC transmission capacity of asynchronous interconnected power grids according to claim 1, characterized in that, The process of constructing the frequency modulation segmented response model for each type of frequency modulation resource includes: Obtain the dead time, ramp time, and frequency regulation reserve capacity of each type of frequency regulation resource in the target asynchronous interconnected power grid; Based on the dead time, the ramp time, and the frequency modulation reserve capacity, a frequency modulation segmented response model is constructed for each type of frequency modulation resource.

3. The method for evaluating the maximum DC transmission capacity of asynchronous interconnected power grids according to claim 1, characterized in that, The intermediate parameter is: ； in, For the first i Intermediate parameters for this type of frequency modulation resource. τ For time variables, For the first i Dead time of various types of frequency modulation resources For the first i The ramp-up time for various types of FM resources This is the positive value operator.

4. The method for evaluating the maximum DC transmission capacity of asynchronous interconnected power grids according to claim 3, characterized in that, The analytical expression for the frequency deviation is: ； in, For frequency deviation, The system's rated frequency, Let be the system's equivalent inertia constant. For the first i Frequency modulation reserve capacity of various types of frequency modulation resources This is the disturbance quantity used in the assessment of maximum DC transmission capacity. J This represents the total number of types of frequency modulation resources.

5. The method for evaluating the maximum DC transmission capacity of asynchronous interconnected power grids according to claim 1, characterized in that, The minimum frequency constraint includes a maximum allowable frequency deviation, which is the difference between the rated frequency and the minimum frequency limit. A discretized linear transformation of the analytical expression of the minimum frequency constraint yields the frequency safety constraint, including: By setting the frequency deviation analytical expression to be less than or equal to the maximum allowable frequency deviation, a linear inequality constraint is obtained. During a single frequency modulation period, the linear inequality constraints are sampled according to a preset sampling step size to obtain several linear inequalities, which serve as frequency security constraints.

6. The method for evaluating the maximum DC transmission capacity of asynchronous interconnected power grids according to claim 1, characterized in that, The frequency security constraint is: ； in, For the first i Intermediate parameters for this type of frequency modulation resource. τ For time variables, The system's rated frequency, Let be the system's equivalent inertia constant. For the first i Frequency modulation reserve capacity of various types of frequency modulation resources This is the disturbance quantity used in the assessment of maximum DC transmission capacity. J The total number of FM resource types. To allow the maximum frequency deviation, k For sampling sequences, , N The total number of frequency security constraints. This is the sampling step size.

7. The method for evaluating the maximum DC transmission capacity of asynchronous interconnected power grids according to claim 1, characterized in that, After obtaining frequency security constraints, the following is also included: Based on the target asynchronous interconnected power grid parameters, construct resource operation constraints and DC linearity constraints; Based on the aforementioned frequency security constraints, an optimization model is constructed and solved with the objective function of maximizing DC transmission capacity. The resulting evaluation of the maximum DC transmission capacity of the target asynchronous interconnected power grid is obtained, including: Based on the frequency security constraints, resource operation constraints, and DC linear constraints, an optimization model is constructed with the maximum DC transmission capacity as the objective function. The optimization model is input with the load forecast of the target asynchronous interconnected power grid and the predicted operation of each frequency regulation resource. The model is solved with the coordinated frequency regulation output of each frequency regulation resource and the optimal start-up and shutdown of the units as variables to obtain the evaluation result of the maximum DC transmission capacity of the target asynchronous interconnected power grid.

8. The method for evaluating the maximum DC transmission capacity of asynchronous interconnected power grids according to claim 7, characterized in that, The process of constructing the DC linear constraint includes: The first set of binary variables is introduced to limit the boundaries of forward and reverse power transmission, thereby obtaining DC output constraints; A second set of binary variables is introduced to represent the upward and downward adjustment of DC power, thereby obtaining the DC regulation action constraint; A third set of binary variables is introduced to record the switching of power flow direction, thereby obtaining the constraint on the number of power flow reversals.

9. A device for evaluating the maximum DC transmission capacity of an asynchronous interconnected power grid, characterized in that, include: The frequency regulation resource equivalent modeling module is used to substitute the frequency regulation segment response model of each type of frequency regulation resource in the target asynchronous interconnected power grid into the frequency dynamic swing equation and then integrate it. The integral of each frequency regulation segment response model in the integration result is converted into the form of the product of the frequency regulation reserve capacity and intermediate parameters of the frequency regulation resource of that type. This yields an algebraic mapping in linear form between the disturbance and frequency deviation in the DC maximum transmission capacity assessment, denoted as the frequency deviation analytical expression. The intermediate parameters are obtained based on the dead time and ramp-up time of the frequency regulation resource of that type. The frequency safety constraint generation module is used to perform a discretization linear transformation on the frequency deviation analytical expression to obtain the frequency safety constraint; The optimization solution and evaluation module is used to construct and solve an optimization model with the maximum DC transmission capacity as the objective function based on the frequency security constraints, and obtain the evaluation result of the maximum DC transmission capacity of the target asynchronous interconnected power grid.

10. A device for assessing the maximum DC transmission capacity of an asynchronous interconnected power grid, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the method as described in any one of claims 1 to 8.

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