Network construction type power supply inertia optimization method and system oriented to frequency safety and medium

Abstract

The invention discloses a frequency-safety-oriented network construction type power supply inertia optimization method and system and a medium. The method comprises the steps of constructing a network construction type power supply inertia optimization model; solving the network construction type power supply inertia optimization model to obtain a plurality of network construction type power supply 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 so as to determine a minimum network construction type power supply inertia parameter value which enables the lowest point of the system frequency and the frequency change rate to meet safety requirements from the plurality of network construction type power supply inertia parameters, thereby realizing optimal configuration of the network construction type power supply inertia. According to the method, part of operation parameters of the network construction type power supply can be reasonably regulated and controlled, optimal configuration of inertia parameters of the network construction type power supply is realized, control is carried out based on the optimal inertia parameters of the network construction type power supply, and the operation stability of a power system can be conveniently improved.

Description

Technical Field

[0001] The present invention relates to the field of power system operation and control technology, and in particular to a frequency safety-oriented grid-type power supply inertia optimization method, system and medium. Background Art

[0002] In modern power systems, rationally regulating some operating parameters of grid-connected power sources can further improve the operational stability of power systems compared to traditional generators. Taking the inertia parameters in the inverter control system of a grid-connected power source as an example, rationally configuring the inertia parameters of the grid-connected power source, combined with the distribution characteristics of the inertia parameters of traditional power system units, can improve the frequency security and operational stability of the power system after large disturbances.

[0003] System inertia is a key characteristic affecting power system frequency security. In the early stages of a system disturbance, the rate of change of system frequency is significantly affected by system inertia. Larger inertia helps suppress rapid changes in system frequency under unbalanced power. Therefore, by combining the inherent inertia configuration of traditional system units and rationally configuring the inertia parameters of grid-connected power sources with adjustable operating parameters, the risk of system frequency exceeding limits during large disturbances can be effectively reduced.

[0004] The rotational inertia of the power system is an important factor affecting the frequency security of the power system. In recent years, the proportion of renewable energy power generation has continued to increase. On the one hand, it has replaced synchronous units of the same capacity, resulting in a decrease in system inertia. On the other hand, some renewable energy units with inertia support capabilities can provide virtual inertia support to the power grid. At the same time, changes in their own operating mode may also cause changes in the level of inertia support provided. System frequencies that are too high or too low will affect the safe and stable operation of the power system. For example, a high frequency may lead to high-frequency shedding, and a low frequency may trigger low-frequency load shedding. Therefore, according to the frequency security requirements of the power system, it is necessary to evaluate the rotational inertia threshold required by the power system and implement further control based on the threshold calculation results. Summary of the Invention

[0005] The present invention aims to, at least to some extent, address the technical problems in the related art. To this end, a first object of the present invention is to provide a method for optimizing the inertia of a grid-type power supply for frequency safety. This method can rationally regulate some operating parameters of the grid-type power supply, achieve optimal configuration of the grid-type power supply inertia parameters, and thereby improve the operational stability of the power system.

[0006] The second object of the present invention is to provide a grid-type power supply inertia optimization system oriented towards frequency safety.

[0007] A third object of the present invention is to provide a computer-readable storage medium.

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

[0009] A frequency safety-oriented grid-type power supply inertia optimization method includes:

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

[0011] Solving the grid-type power supply inertia optimization model to obtain a plurality of grid-type power supply inertia parameters;

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

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

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

[0015]

[0016] Among them, max is the maximum value function, ∑ is the summation function, T j is the fault clearing time in the j-th three-phase short-circuit fault scenario, is the inertia parameter of the nth grid-type power supply, Nt is the total number of three-phase short-circuit fault scenarios, T Nt is the fault clearing time in the Ntth three-phase short circuit fault scenario, st represents the limiting condition, f rocof is the system frequency change rate, is the safety limit of the system frequency change rate, f min is the lowest point of the system frequency, is the safety limit of the system transient frequency, F fre For the single failure safety criterion scenario that occurs in the system, is the hth single failure safety criterion scenario, N f is the total number of single failure safety criterion scenarios.

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

[0018] Preferably, the system frequency response model includes a transfer function link for processing the overall unbalanced power of the system to obtain the frequency deviation of the disturbed system, and the transfer function link includes the inertia parameter of the grid-type power supply.

[0019] Preferably, the system frequency response model also includes transfer function links, dead zone links and limit links of thermal power units, hydropower units and new energy units, and the dead zone links and limit links are nonlinear links.

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

[0021] H th =min H

[0022]

[0023] Among them, H th It is the minimum grid-type power supply inertia parameter value that can make the system frequency minimum point and frequency change rate meet the safety requirements after the single fault safety criterion scenario occurs in the system. min is the minimum value function, H is the grid-type power supply inertia parameter set, is the rate of change of system frequency at the initial stage of system disturbance.

[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 link 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 the model complexity and improve the 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 logical judgment equation with piecewise characteristics in the nonlinear link into a mixed integer linear inequality equation by introducing integer variables, so as to improve the solving efficiency.

[0028] To achieve the above-mentioned object, the second aspect of the present invention provides a frequency safety-oriented grid-type power supply inertia optimization system, comprising:

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

[0030] A first solving module is used to solve the grid-type power supply inertia optimization model to obtain a plurality of grid-type power supply inertia parameters;

[0031] The second building module is used to build a system frequency response model and an inertia threshold optimization model;

[0032] A second solving 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 from multiple grid-type power supply inertia parameters so that the system frequency minimum point and frequency change rate both meet safety requirements, thereby achieving optimal configuration of the grid-type power supply inertia.

[0033] To achieve the above-mentioned objectives, the third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the above-mentioned frequency-safety-oriented grid-type power supply inertia optimization method is implemented.

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

[0035] The present invention provides a frequency safety-oriented grid-type power supply inertia optimization method. Specifically, 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. Then, the inertia threshold optimization model is solved based on the system frequency response model. Thus, the minimum grid-type power supply inertia parameter value, i.e., the inertia threshold value, that satisfies safety requirements at both the lowest system frequency point and the frequency change rate can be determined from the multiple grid-type power supply inertia parameters. Thus, the optimal configuration of the grid-type power supply inertia can be achieved. Further regulation is performed based on the inertia threshold value, thereby improving the operational safety and stability of the power system. A differential discretization method and a penalty factor method are respectively used to process the transfer function link and the nonlinear link in the system frequency response model, thereby eliminating the non-analytical iterative calculation process of the system frequency, reducing model complexity, and improving solution efficiency.

[0036] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0038] Figure 2 Schematic diagram of the system frequency response model structure of an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present embodiment is described in detail below. Examples of the embodiment 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 explain the present invention, but are not to be construed as limiting the present invention.

[0040] The following describes the frequency safety-oriented grid-type power supply inertia optimization method, system, and medium of this embodiment with reference to the accompanying drawings.

[0041] Figure 1 Flowchart of the frequency safety-oriented grid-type power supply inertia optimization method according to an embodiment of the present invention. Figure 1 As shown, the method includes:

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

[0043] Step S102: solving the grid-type power supply inertia optimization model to obtain a plurality of grid-type power supply inertia parameters.

[0044] Step S103: constructing a system frequency response model and an inertia threshold optimization model.

[0045] Step S104: Solve the inertia threshold optimization model based on the system frequency response model to determine the minimum grid-type power supply inertia parameter value from multiple grid-type power supply inertia parameters so that the system frequency minimum point and frequency change rate both meet safety requirements, thereby achieving the optimal configuration of the 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. Then, the inertia threshold optimization model is solved based on the system frequency response model. Thus, the minimum grid-type power supply inertia parameter value, i.e., the inertia threshold, which makes the lowest system frequency point and frequency change rate meet safety requirements can be determined from the multiple grid-type power supply inertia parameters. This allows the optimal configuration of the grid-type power supply inertia to be achieved. Further regulation based on the inertia threshold can improve the operational safety and stability of the power system.

[0047] In the frequency safety-oriented grid-type power supply inertia optimization method, the specific implementation process of steps S101 and S102 is as follows:

[0048] Assume that there are a series of possible N-1 failures in the system (N-1 failures represent the N-1 principle or single failure safety criterion), which are denoted as: For Nth f A single failure safety criterion scenario.

[0049] When the same set of system inertia parameters (generator inertia parameters are The inertia parameter of the grid-type power supply is is the inertia parameter of the mth generator, is the inertia parameter of the nth grid-type power supply), when the maximum frequency change rate and the lowest frequency point of the system can meet the safety requirements, it is considered that this set of inertia parameters can ensure the frequency safety of the system.

[0050] Design the corresponding grid-type power supply inertia optimization model so that the system frequency is in the N-1 fault scenario Under the premise that all frequency safety requirements are met, three-phase short circuit fault scenario ( For the Ntth three-phase short-circuit fault scenario), the corresponding limit 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 the safety of the transient power angle Nt (T Nt is the fault clearing time in the Ntth three-phase short circuit fault scenario) as large as possible. Specifically, the grid-type power supply inertia optimization model is expressed as follows:

[0051]

[0052] Among them, max is the maximum value function, ∑ is the summation function, T j is the fault clearing time in the jth three-phase short circuit fault scenario, Nt is the total number of three-phase short circuit fault scenarios, st represents the limiting condition, f rocof is the system frequency change rate, is the safety limit of the system frequency change rate, f min is the lowest point of the system frequency, is the safety limit of the system transient frequency, F fre For the single failure safety criterion scenario that occurs in the system, is the hth single failure safety criterion scenario, N f is the total number of single fault safety criterion scenarios. Thus, the inertia parameters of n grid-type power supplies can be obtained.

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

[0054] Considering conventional units (such as hydropower and thermal power units) and some new energy 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 the power system is disturbed. In order to simplify the calculation, some frequency regulation structures of the same type of generators are uniformly represented using similar mathematical models. In addition, in order to more accurately characterize the system frequency dynamics, the system frequency response model takes into account some typical nonlinear links in the power system (such as dead zones and limiter links, etc.). The specific structure is as follows: Figure 2 shown.

[0055] Figure 2The primary frequency regulation structure models of thermal power units, hydropower units, and renewable energy units are shown in Figure 1. Δf represents the system frequency deviation after the disturbance; and Respectively represent the frequency deviations of thermal power units, hydropower units and new energy units after crossing the dead zone; and Represent the unit power regulation coefficients of thermal power units and hydropower units respectively; T G is the time constant of the speed regulator; T CH is the turbine time constant; T RH is the reheating time constant; F HP is the reheat coefficient; T R is the reset time constant; R T is the temporary descent rate; R P is the permanent descent 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 Indicates the disturbance power suffered by the system; ΔP unb Indicates the unbalanced power of the entire system. Figure 2 It can be seen that the system frequency response model includes a transfer function link that processes the overall system unbalanced power to obtain the system frequency deviation after the disturbance. This transfer function link includes the inertia parameters of the grid-type power supply. The system frequency response model also includes the transfer function link, dead zone link, and limiter link for thermal power units, hydropower units, and renewable energy units. The dead zone link and limiter link are nonlinear links.

[0056] The inertia threshold H of the power system in a certain operating scenario th The inertia threshold optimization model is constructed to calculate the inertia threshold. Taking the case of generator N-1 failure (system frequency drop) in the current scenario as an example, the inertia threshold optimization model is expressed as follows:

[0057] H th =minH (3)

[0058]

[0059] Among them, min is the minimum value function, H is the inertia parameter set of the grid power supply, is the rate of change of the system frequency at the initial stage of a disturbance. The decision variable is the inertia parameter of the grid-type power supply, which affects the lowest point of the system frequency and the rate of change of the system frequency after the disturbance. Therefore, it is necessary to simulate and calculate the fluctuation of the transient frequency of the system after the disturbance to obtain the lowest point of the system frequency and the rate of change of the frequency within the above constraints.

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

[0061] Furthermore, when solving the inertia threshold optimization model based on the system frequency response model, the method includes using a differential discretization method to process the transfer function link in the system frequency response model, and using the input and output variables of the system frequency response model at each discrete time section 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, the method also includes using a penalty factor method to convert the logical judgment equation with piecewise characteristics in the nonlinear link into a mixed integer linear inequality equation by introducing integer variables to improve solution efficiency.

[0062] Traditionally, the optimization model solution involves embedding a system frequency calculation step based on time-domain simulation software or numerical integration. However, this nonlinear, non-analytical process increases the complexity of the model solution. Essentially, the iterative calculation step is the transfer function step in the system frequency response model. Therefore, a differential discretization method can be used to process the transfer function step in the system frequency response model. The input and output variables in the system frequency response model at each discrete time section can be added as decision variables in the inertia threshold optimization model. This eliminates the non-analytical, iterative calculation step of the system frequency and reduces model complexity.

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

[0064]

[0065] By performing differential discretization on the above transfer function model, the corresponding autoregressive moving average model can be obtained as follows:

[0066]

[0067] in, is the output power instruction at the kth sampling time point, p represents the order of the corresponding transfer function; α i and β j Denotes the corresponding constant coefficient, i and j denote different orders. The sampling time interval of the above differential discretization process is constant at T, and the total time of numerical integration for system frequency calculation is T max , a total of t m Sampling time points, the equality constraints corresponding to each sampling time point are as follows:

[0068]

[0069] For the tth m The output power command at each sampling time point. m The set of linear equations will serve as constraints for the above inertia threshold optimization model. and It 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 perform differential discretization operations, so that each of them in the range of 0~T max The numerical integration process in the period is converted to t m In summary, based on the above transformation ideas, we can cleverly avoid directly solving the frequency dynamics based on numerical integration, thereby improving the solution efficiency.

[0070] In addition to the linear transfer function mentioned above, the system frequency response model also includes some nonlinear links such as dead zones and clipping. This embodiment mainly uses the Big M method (penalty factor method) to transform the above-mentioned logical judgment equations with piecewise characteristics into mixed integer linear inequality equations by introducing integer variables. Taking the clipping link as an example, the specific process is as follows:

[0071]

[0072] in, Indicates the actual power regulation of the new energy output after the power limit link; ΔP up and ΔP down The upper and lower limits of the power adjustment of the new energy unit; s rpg It is an introduced 0 / 1 integer variable, 1 indicates that the upper limit is reached, and 0 indicates that the limit has not been reached yet.

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

[0074]

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

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

[0077] Furthermore, the present invention also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the above-mentioned frequency-safety-oriented grid-type power supply inertia optimization method can be implemented.

[0078] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0079] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A frequency safety-oriented grid-type power supply inertia optimization method, characterized in that: include: Construct a grid-type power supply inertia optimization model; Solving the grid-type power supply inertia optimization model to obtain a plurality of grid-type power supply inertia parameters; Construct system frequency response model and inertia threshold optimization model; The inertia threshold optimization model is solved based on the system frequency response model to determine the minimum grid-type power supply inertia parameter value that makes the system frequency minimum point and frequency change rate meet safety requirements from multiple grid-type power supply inertia parameters, thereby achieving the optimal configuration of the grid-type power supply inertia.

2. The frequency safety-oriented grid-type power supply inertia optimization method according to claim 1, characterized in that: The grid-type power supply inertia optimization model is expressed as follows: Among them, max is the maximum value function, ∑ is the summation function, T j is the fault clearing time in the jth three-phase short-circuit fault scenario, is the inertia parameter of the nth grid-type power supply, Nt is the total number of three-phase short-circuit fault scenarios, T Nt is the fault clearing time in the Ntth three-phase short-circuit fault scenario, st represents the limiting condition, and f rocof is the system frequency change rate, is the safety limit of the system frequency change rate, f min is the lowest frequency point of the system. is the safety limit of the system transient frequency, F fre For the single failure safety criterion scenario that occurs in the system, is the hth single failure safety criterion scenario, N f is the total number of single fault safety criterion scenarios.

3. The frequency safety-oriented grid-type power supply inertia optimization method according to claim 1, characterized in that: The system frequency response model is a primary frequency regulation structure model of thermal power units, hydropower units and new energy units.

4. The frequency safety-oriented grid-type power supply inertia optimization method according to claim 3, characterized in that: The system frequency response model includes a transfer function link for processing the overall unbalanced power of the system to obtain the frequency deviation of the disturbed system, and the transfer function link includes the inertia parameter of the grid-type power supply.

5. The frequency safety-oriented grid-type power supply inertia optimization method according to claim 4, characterized in that: The system frequency response model also includes transfer function links, dead zone links and amplitude limiting links of thermal power units, hydropower units and new energy units, and the dead zone links and amplitude limiting links are nonlinear links.

6. The frequency safety-oriented grid-type power supply inertia optimization method according to claim 2, characterized in that: The inertia threshold optimization model is expressed as follows: H th =min H Among them, H th is the minimum grid-type power supply inertia parameter value that can make the system frequency minimum point and frequency change rate meet the safety requirements after the single fault safety criterion scenario occurs in the system, min is the minimum value function, H is the grid-type power supply inertia parameter set, It is the rate of change of system frequency at the initial stage of system disturbance.

7. The frequency safety-oriented grid-type power supply inertia optimization method according to claim 5, characterized in that: When solving the inertia threshold optimization model based on the system frequency response model, the method includes: The differential discretization method is used to process the transfer function link 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 the model complexity and improve the solution efficiency.

8. The frequency safety-oriented grid-type power supply inertia optimization method according to claim 5, characterized in that: When solving the inertia threshold optimization model based on the system frequency response model, the method further includes: The penalty factor method is used to transform the logical judgment equation with piecewise characteristics in the nonlinear link into a mixed integer linear inequality equation by introducing integer variables, so as to improve the solving efficiency.

9. A frequency safety-oriented grid-type power supply inertia optimization system, characterized in that: include: The first building module is used to build a grid-type power supply inertia optimization model; A first solving module is used to solve the grid-type power supply inertia optimization model to obtain a plurality of grid-type power supply inertia parameters; The second building module is used to build a system frequency response model and an inertia threshold optimization model; The second solving 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 from multiple grid-type power supply inertia parameters so that the system frequency minimum point and frequency change rate both meet the safety requirements, thereby achieving the optimal configuration of the grid-type power supply inertia.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the frequency safety-oriented grid-type power supply inertia optimization method as described in any one of claims 1 to 8 is implemented.

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