Methods, systems, and media for optimizing the inertia of grid-based power supplies for frequency security

Abstract

This invention discloses a method, system, and medium for optimizing the inertia of grid-connected power sources for frequency security. The method includes constructing a grid-connected power source inertia optimization model; solving the grid-connected power source inertia optimization model to obtain multiple grid-connected power source inertia parameters; constructing a system frequency response model and an inertia threshold optimization model; and solving the inertia threshold optimization model based on the system frequency response model to determine the minimum grid-connected power source inertia parameter value from the multiple grid-connected power source inertia parameters that satisfies safety requirements for both the system's lowest frequency and the rate of frequency change, thus achieving optimal configuration of grid-connected power source inertia. This invention can reasonably control some operating parameters of grid-connected power sources to achieve optimal configuration of grid-connected power source inertia parameters, and then perform control based on these optimal grid-connected power source inertia parameters, which can facilitate the improvement of power system operational stability.

Description

Technical Field

[0001] This invention relates to the field of power system operation and control technology, and in particular to a method, system and medium for optimizing the inertia of grid-type power sources for frequency security. Background Technology

[0002] In modern power systems, compared to traditional generator sets, rationally adjusting certain operating parameters of grid-connected power sources can further improve the operational stability of the power system. Taking the inertia parameter in the inverter control system of a grid-connected power source as an example, by rationally configuring the inertia parameter of the grid-connected power source in conjunction with the distribution characteristics of the inertia parameter of traditional power units, the frequency security and operational stability of the power system after large disturbances can be improved.

[0003] System inertia is a crucial characteristic affecting power system frequency security. In the initial stages of a system disturbance, the rate of change of system frequency is significantly influenced by system inertia; a larger inertia helps suppress rapid changes in system frequency under unbalanced power conditions. Therefore, by combining the inherent inertia configuration of traditional generating units with adjustable operating parameters, the inertia parameters of grid-connected power sources can be rationally configured to effectively reduce the risk of system frequency exceeding limits under large disturbances.

[0004] The rotational inertia of a power system is a crucial factor affecting its frequency security. In recent years, the increasing proportion of renewable energy generation has, on the one hand, replaced synchronous generators of the same capacity, leading to a decrease in system inertia; on the other hand, some renewable energy units with inertia support capabilities can provide virtual inertia support to the grid, and changes in their own operating modes may also cause variations in the level of inertia support they provide. Both excessively high and low system frequencies can affect the safe and stable operation of the power system. For example, excessively high frequencies may lead to high-frequency generator shedding, while excessively low frequencies may trigger low-frequency load shedding. Therefore, it is necessary to assess the required rotational inertia threshold of the power system according to its frequency security requirements and implement further control measures based on the calculated threshold. Summary of the Invention

[0005] This invention aims to at least partially address the technical problems in related technologies. Therefore, the first objective of this invention is to provide a method for optimizing the inertia of grid-connected power sources for frequency security. This method can rationally adjust some operating parameters of grid-connected power sources to achieve optimal configuration of their inertia parameters, thereby improving the operational stability of the power system.

[0006] The second objective of this invention is to provide a network-based power inertia optimization system for frequency security.

[0007] A third objective of this invention is to provide a computer-readable storage medium.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0009] A method for optimizing the inertia of grid-based power supplies for frequency security includes:

[0010] Construct a grid-type power supply inertia optimization model;

[0011] Solving the networked power supply inertia optimization model yields multiple networked power supply inertia parameters;

[0012] Construct a system frequency response model and an inertia threshold optimization model;

[0013] The inertia threshold optimization model is solved based on the system frequency response model in order to determine the minimum grid-type power supply inertia parameter value that satisfies the safety requirements for both the lowest system frequency and the rate of frequency change from multiple grid-type power supply inertia parameters, thereby achieving the optimal configuration of grid-type power supply inertia.

[0014] Preferably, the grid-type power supply inertia optimization model is expressed as follows:

[0015]

[0016] Where max is the function for finding the maximum value, ∑ is the summation function, and T j Let be the fault clearing time in the j-th three-phase short-circuit fault scenario. Let Nt be the inertia parameter of the nth grid-type power supply, and T be the total number of three-phase short-circuit fault scenarios. Nt Let f be the fault clearing time in the Nt-th three-phase short-circuit fault scenario, st represents the constraint condition, and f rocof The system frequency change rate, f is the safety limit for the system's rate of change of frequency. min This is the lowest point of the system frequency. F is the safety limit for the system transient frequency. fre For the single failure safety criterion scenario of the system, For the h-th single failure safety criterion scenario, N f This represents the total number of scenarios for the single fault-tolerant criterion.

[0017] Preferably, the system frequency response model is a primary frequency regulation structure model for thermal power units, hydropower units, and new energy units.

[0018] Preferably, the system frequency response model includes a transfer function component that processes the overall unbalanced power of the system to obtain the frequency deviation of the system after disturbance, and the transfer function component includes the inertia parameter of the grid-type power supply.

[0019] Preferably, the system frequency response model further includes transfer function components, dead zone components, and limiting components for thermal power units, hydropower units, and new energy units, wherein the dead zone components and limiting components are nonlinear components.

[0020] Preferably, the inertia threshold optimization model is expressed as follows:

[0021] H th =min H

[0022]

[0023] Among them, H th The minimum grid-type power supply inertia parameter value that ensures both the system's lowest frequency and rate of change meet safety requirements after a single-failure safety criterion scenario, where min is the minimum value function and H is the set of grid-type power supply inertia parameters. This represents the rate of change of the system frequency in the initial stage of the system being disturbed.

[0024] Preferably, when solving the inertia threshold optimization model based on the system frequency response model, the method includes:

[0025] The differential discretization method is used to process the transfer function in the system frequency response model, and the input and output variables of the system frequency response model on each discrete time section are used as decision variables to reduce model complexity and improve solution efficiency.

[0026] Preferably, when solving the inertia threshold optimization model based on the system frequency response model, the method further includes:

[0027] The penalty factor method is used to transform the piecewise logical judgment equations in the nonlinear link into mixed integer linear inequality equations by introducing integer variables, thereby improving the solution efficiency.

[0028] To achieve the above objectives, a second aspect of the present invention provides a network-based power inertia optimization system for frequency security, comprising:

[0029] The first building module is used to build a grid-type power inertia optimization model;

[0030] The first solution module is used to solve the grid-type power supply inertia optimization model to obtain multiple grid-type power supply inertia parameters.

[0031] The second building module is used to build the system frequency response model and the inertia threshold optimization model.

[0032] The second solution module is used to solve the inertia threshold optimization model based on the system frequency response model, so as to determine the minimum grid-type power supply inertia parameter value that makes the system's lowest frequency point and frequency change rate meet the safety requirements from multiple grid-type power supply inertia parameters, thereby achieving the optimal configuration of grid-type power supply inertia.

[0033] To achieve the above objectives, a third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, it implements the above-described frequency security-oriented network-type power inertia optimization method.

[0034] This invention has at least the following technical effects:

[0035] This invention provides a method for optimizing the inertia of grid-connected power sources for frequency security. Specifically, it involves first constructing a grid-connected power source inertia optimization model, then solving the model to obtain multiple inertia parameters. Next, it constructs a system frequency response model and an inertia threshold optimization model. Finally, it solves the inertia threshold optimization model based on the system frequency response model. This allows the determination of the minimum inertia parameter value (the inertia threshold) from the multiple grid-connected power source inertia parameters, ensuring that both the system's lowest frequency and rate of change meet safety requirements. This enables optimal configuration of the grid-connected power source inertia. Further adjustments based on this inertia threshold can improve the operational safety and stability of the power system. The method employs differential discretization and penalty factor methods to process the transfer function and nonlinear components in the system frequency response model, respectively, eliminating the non-analytical iterative calculation process for system frequency, reducing model complexity, and improving solution efficiency.

[0036] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0037] Figure 1 This is a flowchart of a frequency-safe grid-type power supply inertia optimization method according to an embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram of the system frequency response model structure according to an embodiment of the present invention. Detailed Implementation

[0039] The following describes this embodiment in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0040] The following description, with reference to the accompanying drawings, illustrates a frequency-safe grid-type power inertia optimization method, system, and medium according to this embodiment.

[0041] Figure 1 This is a flowchart of a network-based power supply inertia optimization method for frequency security, according to an embodiment of the present invention. Figure 1 As shown, the method includes:

[0042] Step S101: Construct a grid-type power supply inertia optimization model.

[0043] Step S102: Solve the grid-type power supply inertia optimization model to obtain multiple grid-type power supply inertia parameters.

[0044] Step S103: Construct the system frequency response model and inertia threshold optimization model.

[0045] Step S104: Solve the inertia threshold optimization model based on the system frequency response model in order to determine the minimum grid-type power supply inertia parameter value that makes the system's lowest frequency point and frequency change rate meet safety requirements from multiple grid-type power supply inertia parameters, thereby achieving the optimal configuration of grid-type power supply inertia.

[0046] In this embodiment, a grid-type power supply inertia optimization model is first constructed, and then the grid-type power supply inertia optimization model is solved to obtain multiple grid-type power supply inertia parameters. Then, a system frequency response model and an inertia threshold optimization model are constructed. Based on the system frequency response model, the inertia threshold optimization model is solved. Thus, the minimum grid-type power supply inertia parameter value that makes the system's lowest frequency and frequency change rate meet safety requirements can be determined from the multiple grid-type power supply inertia parameters. This is the inertia threshold, which enables the optimal configuration of grid-type power supply inertia. Further regulation based on this inertia threshold can improve the operational safety and stability of the power system.

[0047] In the frequency security-oriented network-based power supply inertia optimization method, the specific implementation processes of steps S101 and S102 are as follows:

[0048] Suppose that a series of N-1 possible faults occur in the system (N-1 faults represent the N-1 principle or the single fault safety criterion), denoted as: For the Nth f A single failsafe scenario.

[0049] Under the same set of system inertia parameters (generator inertia parameters are...), The inertia parameters of a grid-type power supply are Let m be the inertia parameter of the m-th generator. If the maximum frequency change rate and the minimum frequency point of the system can both meet the safety requirements (for the nth grid-type power supply inertia parameter), then the set of inertia parameters is considered to guarantee the frequency safety of the system.

[0050] Design a corresponding grid-type power supply inertia optimization model to ensure that the system frequency is within the N-1 fault scenario. Under the premise that frequency safety requirements are met, three-phase short-circuit fault scenarios ( For the Nt-th three-phase short-circuit fault scenario, the corresponding extreme fault clearing time needs to be increased as much as possible, that is, the fault clearing time T1, T2, ..., T under the premise of ensuring transient power angle safety. Nt (T Nt To maximize the fault clearing time in the Nt-th three-phase short-circuit fault scenario. Specifically, the grid-type power supply inertia optimization model is expressed as follows:

[0051]

[0052] Where max is the function for finding the maximum value, ∑ is the summation function, and T j Let Nt be the fault clearing time in the j-th three-phase short-circuit fault scenario, Nt be the total number of three-phase short-circuit fault scenarios, st represent the constraint conditions, and f be the fault clearing time. rocof The system frequency change rate, f is the safety limit for the system's rate of change of frequency. min This is the lowest point of the system frequency. F is the safety limit for the system transient frequency. fre For the single failure safety criterion scenario of the system, For the h-th single failure safety criterion scenario, N f Let n be the total number of scenarios under the single fault-tolerant criterion. From this, the inertia parameters of n grid-type power supplies can be obtained.

[0053] In the frequency security-oriented grid-type power supply inertia optimization method, the specific implementation processes of steps S103 and S104 are as follows:

[0054] Considering conventional generating units (such as hydropower and thermal power units) and some new energy generating units with primary frequency regulation capabilities in the power system, a corresponding system frequency response model is constructed to simulate the dynamics of the system frequency after a disturbance. To simplify calculations, similar mathematical models are used to represent the frequency regulation structures of similar generators. Furthermore, to more accurately characterize the system frequency dynamics, this system frequency response model considers some typical nonlinear elements in the power system (such as dead zones and limiting elements), with the specific structure as follows: Figure 2 As shown.

[0055] Figure 2The diagrams represent the primary frequency regulation structure models for thermal power units, hydropower units, and new energy units, respectively. Δf represents the system frequency deviation after a disturbance. and These represent the frequency deviations of thermal power units, hydropower units, and new energy units after they have crossed the dead zone, respectively. and T represents the unit power regulation coefficient of thermal power units and hydropower units, respectively; G T is the time constant of the speed controller; CH T is the turbine time constant; RH F is the reheat time constant; HP T is the reheat coefficient; R R is the reset time constant; T For the temporary decline rate; R P For permanent decline rate; F rpg (s) represents the mathematical model of the primary frequency regulation structure of the new energy unit; H represents the inertia parameter of the grid-type power supply; ΔP dis ΔP represents the power of the disturbance experienced by the system. unb This represents the overall unbalanced power of the system. (By...) Figure 2 It can be seen that the system frequency response model includes a transfer function component that processes the overall unbalanced power of the system to obtain the frequency deviation of the system after disturbance. The transfer function component includes the inertia parameter of the grid-type power source. The system frequency response model also includes transfer function components, dead zone components, and limiting components for thermal power units, hydropower units, and new energy units. The dead zone component and the limiting component are nonlinear components.

[0056] The inertia threshold H of a power system under a certain operating scenario th This represents the minimum system inertia level required to ensure that both the lowest system frequency and the rate of frequency change meet safety requirements after an N-1 fault occurs in the power system. Therefore, an inertia threshold optimization model can be constructed to calculate this inertia threshold. Taking the current scenario of a generator N-1 fault (system frequency drop) as an example, the specific inertia threshold optimization model is as follows:

[0057] H th =minH (3)

[0058]

[0059] Where min is the minimum value function, and H is the set of inertia parameters for the grid-type power supply. The system frequency change rate is the initial stage after the system is disturbed. The decision variable is the inertia parameter of the grid-type power source, which affects the lowest point of the system frequency and the system frequency change rate after the disturbance. Therefore, it is necessary to simulate and calculate the fluctuation of the system transient frequency after the disturbance in order to obtain the lowest point of the system frequency and the frequency change rate under the above constraints.

[0060] Therefore, the inertia threshold optimization model can be solved based on the system frequency response model, and the minimum inertia parameter value of the grid-type power supply that makes the system's lowest frequency point and frequency change rate meet the safety requirements can be determined from multiple grid-type power supply inertia parameters, thus achieving the optimal configuration of grid-type power supply inertia.

[0061] Furthermore, when solving the inertia threshold optimization model based on the system frequency response model, this method includes using a differential discretization method to process the transfer function component in the system frequency response model, and using the input and output variables of the system frequency response model at each discrete time segment as decision variables to reduce model complexity and improve solution efficiency. When solving the inertia threshold optimization model based on the system frequency response model, this method also includes using a penalty factor method to transform the piecewise logical judgment equations in the nonlinear component into mixed-integer linear inequality equations by introducing integer variables, thereby improving solution efficiency.

[0062] Traditionally, optimization model solutions incorporate system frequency calculations based on time-domain simulation software or numerical integration. However, these nonlinear and non-analytical processes increase model complexity. Essentially, the iterative calculations originate from the transfer function component in the system frequency response model. Therefore, a differential discretization method can be used to handle the transfer function component in the system frequency response model. The input and output variables of the system frequency response model at each discrete time point can be added as decision variables in the inertia threshold optimization model, thereby eliminating the non-analytical iterative calculations of system frequency and reducing model complexity.

[0063] Here, the transfer function F in the above system frequency response model is used as an example. rpg Taking (s) as an example, its output power command The frequency deviation from the input feedback frequency, i.e., the frequency after the new energy unit crosses the dead zone. The following relationship exists between them:

[0064]

[0065] By differentially discretizing the above transfer function model, we can obtain the corresponding autoregressive moving average model, as follows:

[0066]

[0067] in, The output power command at the k-th sampling time point, where p represents the order of the corresponding transfer function; α i and β j Let represent the corresponding constant coefficients, and i and j represent different orders. The sampling time interval for the above differential discretization process is constant at T, and the total duration of the numerical integration for calculating the system frequency is T. max There are a total of t m There are 3 sampling time points, and the corresponding equality constraints for each sampling time point are as follows:

[0068]

[0069] For the tth m The output power command at each sampling time point. Ultimately, the above totals t m The set of linear equations will serve as constraints on the aforementioned inertia threshold optimization model, while... and This will also be introduced as a new intermediate variable to be optimized in the inertia threshold optimization model. In addition, the other transfer functions of the system frequency response model also undergo differential discretization, thereby separating their respective values ​​from 0 to T. max The numerical integration process within a time period is converted to t m This involves linear equality constraints that include intermediate variables. In summary, based on the above transformation approach, we can cleverly avoid directly solving for frequency dynamics using numerical integration, thereby improving computational efficiency.

[0070] In addition to the linear transfer function mentioned above, the system frequency response model also includes nonlinear elements such as dead zones and amplitude limiting. This embodiment primarily employs the Big M method (penalty factor method) to transform the piecewise logical judgment equations into a system of mixed-integer linear inequalities by introducing integer variables. Taking the amplitude limiting element as an example, the specific process is as follows:

[0071]

[0072] in, ΔP represents the actual power regulation of the new energy output after the power limiting process; up and ΔP down The upper and lower limits for power regulation of new energy generating units; s rpg The introduced 0 / 1 integer variable, where 1 indicates that the upper limit has been reached and 0 indicates that the limit boundary has not yet been reached.

[0073] Furthermore, the above piecewise functional expression, i.e., the logical judgment equation, can be transformed into a system of mixed integer inequalities, as follows:

[0074]

[0075] Where M is a constant, the constraints on the minimum frequency point and the rate of change of frequency in the inertia threshold optimization model will be transformed into a series of mixed integer nonlinear constraints, and the entire optimization problem will be transformed into a mixed integer linear programming problem, thereby achieving higher solution efficiency and solution quality.

[0076] Furthermore, this invention also provides a network-based power supply inertia optimization system for frequency security, comprising a first construction module, a first solution module, a second construction module, and a second solution module connected in sequence. The first construction module is used to construct a network-based power supply inertia optimization model; the first solution module is used to solve the network-based power supply inertia optimization model to obtain multiple network-based power supply inertia parameters; the second construction module is used to construct a system frequency response model and an inertia threshold optimization model; the second solution module is used to solve the inertia threshold optimization model based on the system frequency response model, so as to determine the minimum network-based power supply inertia parameter value from the multiple network-based power supply inertia parameters that satisfies the safety requirements for both the system's lowest frequency point and the rate of frequency change, thereby achieving optimal configuration of the network-based power supply inertia.

[0077] Furthermore, the present invention also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, can implement the above-described frequency-safe grid-type power inertia optimization method.

[0078] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0079] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A frequency security-oriented networked power source inertia optimization method, characterized in that, The method comprises the following steps: A grid-connected power source inertia optimization model is constructed, and the grid-connected power source inertia optimization model is expressed as follows: s.t. Where max is the function for finding the maximum value. For the summation function, For the first Fault clearing time in a three-phase short-circuit fault scenario For the first n Individual grid-type power supply inertia parameters This represents the total number of three-phase short-circuit fault scenarios. For the first The fault clearing time in a three-phase short-circuit fault scenario, where st represents the constraint condition. The system frequency change rate, The safety limit for the system frequency change rate, This is the lowest point of the system frequency. The safety limit for the system transient frequency. For the single failure safety criterion scenario of the system, For the first h A single failsafe scenario. The total number of scenarios for a single fail-safe criterion; A plurality of grid-connected power source inertia parameters are obtained by solving the grid-connected power source inertia optimization model; A system frequency response model and an inertia threshold optimization model are constructed; The inertia threshold optimization model is solved based on the system frequency response model, so that the minimum grid-connected power source inertia parameter value that makes the system frequency minimum point and the frequency change rate both meet the safety requirements is determined from the plurality of grid-connected power source inertia parameters, and the optimal configuration of the grid-connected power source inertia is realized. 2.The frequency safety oriented networked power source inertia optimization method of claim 1, wherein, The system frequency response model is a primary frequency modulation structure model of a thermal power unit, a hydroelectric unit and a new energy unit. 3.The frequency safety oriented networked power source inertia optimization method of claim 2, wherein, The system frequency response model comprises a transfer function link for obtaining a disturbed system frequency deviation by processing system overall unbalanced power, and the transfer function link comprises the grid-connected power source inertia parameter. 4.The frequency security oriented networked power source inertia optimization method of claim 3, wherein, The system frequency response model further comprises a transfer function link, a dead zone link and an amplitude limiting link of the thermal power unit, the hydroelectric unit and the new energy unit, and the dead zone link and the amplitude limiting link are nonlinear links. 5.The frequency safety oriented networked power source inertia optimization method of claim 1, wherein, The inertia threshold optimization model is expressed as follows: s.t. wherein, is the minimum inertia parameter value of the grid-forming power source that enables the system frequency nadir and the rate of change of frequency to meet the safety requirements after the single fault safety criterion scenario, min is a minimum function, is the set of inertia parameters of the grid-forming power source, is the rate of change of frequency of the system at the beginning of the disturbance. 6.The frequency security oriented networked power source inertia optimization method of claim 4, wherein, When the inertia threshold optimization model is solved based on the system frequency response model, the method comprises the following steps: The transfer function link in the system frequency response model is processed by using a difference discretization method, and the input and output variables of the system frequency response model at each discrete time section are used as decision variables, so as to reduce the model complexity and improve the solving efficiency. 7.The frequency security oriented networked power source inertia optimization method of claim 4, wherein, When the inertia threshold optimization model is solved based on the system frequency response model, the method further comprises the following steps: The logic judgment equation with a segmented characteristic in the nonlinear link is converted into a mixed integer linear inequality equation by introducing an integer variable through a penalty factor method, so as to improve the solving efficiency. 8.A frequency security oriented networked power source inertia optimization system, characterized in that, The method comprises the following steps: A first construction module is configured to construct a grid-connected power source inertia optimization model, and the grid-connected power source inertia optimization model is expressed as follows: s.t. Where max is the function for finding the maximum value. For the summation function, For the first Fault clearing time in a three-phase short-circuit fault scenario For the first n Individual grid-type power supply inertia parameters This represents the total number of three-phase short-circuit fault scenarios. For the first The fault clearing time in a three-phase short-circuit fault scenario, where st represents the constraint condition. The system frequency change rate, The safety limit for the system frequency change rate, This is the lowest point of the system frequency. The safety limit for the system transient frequency. For the single failure safety criterion scenario of the system, For the first h A single failsafe scenario. The total number of scenarios for a single fail-safe criterion; A first solving module is configured to solve the grid-connected power source inertia optimization model to obtain a plurality of grid-connected power source inertia parameters; A second construction module is configured to construct a system frequency response model and an inertia threshold optimization model; A second solving module is configured to solve the inertia threshold optimization model based on the system frequency response model, so that the minimum grid-connected power source inertia parameter value that makes the system frequency minimum point and the frequency change rate both meet the safety requirements is determined from the plurality of grid-connected power source inertia parameters, and the optimal configuration of the grid-connected power source inertia is realized.

9. A computer readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the frequency safety-oriented grid-connected power source inertia optimization method in any one of claims 1-7.

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