Method and device for quantifying rapid frequency modulation effect of battery energy storage, equipment and storage medium

Abstract

The embodiments of the present application provide a method and device for quantifying the rapid frequency regulation effect of battery energy storage, an electronic device, and a storage medium, and belong to the field of power grid frequency regulation technology. The method includes: obtaining system parameters of the power system; based on the system parameters, performing inertia merging on the power system to obtain the total system inertia; based on the system parameters and the total system inertia, performing frequency deviation analysis on the power system to obtain frequency deviation data; based on the frequency deviation data, the total system inertia, and the system parameters, performing frequency response characteristic analysis to obtain the aggregated frequency response landslide rate of the generator; based on the system parameters, the total system inertia, and the aggregated frequency response landslide rate of the generator, performing frequency regulation effect quantification to obtain battery energy storage rapid frequency regulation effect data. The embodiments of the present application can improve the reliability of rapid frequency regulation of the power system.

Description

Technical Field

[0001] The present application relates to the technical field of power grid frequency regulation, and in particular to a method and device for quantifying the rapid frequency regulation effect of battery energy storage, an electronic device, and a storage medium. Background Art

[0002] Battery energy storage rapid frequency regulation refers to the process of regulating frequency changes in the power system by leveraging the rapid response characteristics of battery energy storage systems. With the rapid development of new energy technologies and their large-scale integration into the power system, traditional power systems based on synchronous generators are facing challenges in frequency security and stability. Due to the intermittent and uncertain nature of new energy, the inertia level of the power system is reduced, resulting in a weakened resistance to frequency changes and an increased risk of frequency deviation. As a flexible and rapid frequency regulation resource, battery energy storage systems can quickly respond to disturbances in the power system, providing the necessary power support to maintain the stability of the power system's frequency.

[0003] However, existing research and practice mainly focus on the demand response of energy storage systems and the suppression of renewable energy fluctuations, and lack a mechanistic approach, which leads to unreliable rapid frequency regulation of battery energy storage in power systems. Therefore, how to improve the reliability of rapid frequency regulation of battery energy storage has become a technical problem that needs to be solved urgently. Summary of the Invention

[0004] The main purpose of the embodiments of the present application is to propose a method and device for quantifying the rapid frequency modulation effect of battery energy storage, an electronic device and a storage medium, aiming to improve the reliability of rapid frequency modulation of battery energy storage.

[0005] To achieve the above objectives, a first aspect of an embodiment of the present application proposes a method for quantifying the rapid frequency modulation effect of battery energy storage, which is applied to a battery energy storage system. The method includes:

[0006] Obtaining system parameters of the power system;

[0007] Based on the system parameters, performing inertia merging on the power system to obtain a total system inertia;

[0008] performing frequency deviation analysis on the power system based on the system parameters and the total inertia of the system to obtain frequency deviation data;

[0009] Performing frequency response characteristic analysis based on the frequency deviation data, the total inertia of the system, and the system parameters to obtain a generator aggregate frequency response landslide rate;

[0010] Based on the system parameters, the total inertia of the system and the aggregate frequency response ramp rate of the generator, the frequency regulation effect is quantified to obtain battery energy storage rapid frequency regulation effect data.

[0011] In some embodiments, the system parameters include a power system dead zone frequency and a power system minimum stable frequency, and performing frequency deviation analysis on the power system based on the system parameters, the system parameters, and the total inertia of the system to obtain frequency deviation data includes:

[0012] Obtaining a current frequency of the power system;

[0013] Calculating a frequency difference of the power system based on the dead-zone frequency of the power system and the current frequency of the system to obtain a first deviation frequency;

[0014] Based on the first deviation frequency, frequency modulation is performed on the power system to obtain a system frequency modulation frequency;

[0015] Based on the system frequency modulation frequency and the minimum stable frequency of the power system, performing a secondary frequency difference calculation on the power system to obtain a second deviation frequency;

[0016] Data integration is performed on the first deviation frequency and the second deviation frequency to obtain the frequency deviation data.

[0017] In some embodiments, the system parameters include a total number of generators, an inertia time constant, and a maximum power generation power. Based on the system parameters, performing inertia merging on the power system to obtain a total system inertia includes:

[0018] Identifying faulty motors in the power system to obtain the number of faulty generators;

[0019] Determining the number of non-faulty generators based on the number of faulty generators and the total number of generators;

[0020] Calculating the generator inertia based on the inertia time constant, the maximum generated power, and the number of non-faulty generators to obtain the generator inertia;

[0021] The generator inertia is data merged to obtain the total inertia of the system.

[0022] In some embodiments, the system parameters include the generator speed regulation system time constant, the total single frequency regulation of the system's new energy resources, and the total frequency regulation of the battery energy storage system. The frequency regulation effect is quantified based on the system parameters, the total inertia of the system, and the aggregate frequency response ramp rate of the generator to obtain battery energy storage rapid frequency regulation effect data, including:

[0023] Predicting a minimum value of the landslide rate of the aggregate frequency response of the generator to obtain minimum landslide rate data;

[0024] Performing a dynamic response analysis based on the total inertia of the system and the time constant of the generator speed control system to obtain a dynamic response coefficient;

[0025] Based on the minimum landslide rate data, the total inertia of the system, the total single frequency modulation of the system's new energy, and the total frequency modulation of the battery energy storage system, a system stability analysis is performed to obtain a frequency stability index;

[0026] Based on the dynamic response coefficient and the frequency stability index, the frequency modulation effect is analyzed to obtain the battery energy storage rapid frequency modulation effect data.

[0027] In some embodiments, performing a dynamic response analysis based on the total inertia of the system and the time constant of the generator speed control system to obtain a dynamic response coefficient includes:

[0028] The dynamic response coefficient is calculated by calculating the dynamic characteristics of the power system using the following dynamic response coefficient calculation formula:

[0029] ;

[0030] in, represents the total inertia of the system, represents the time constant of the generator speed control system of the g-th synchronous generator, Represents the preset first constant coefficient, Represents the preset second constant coefficient, Represents the preset third constant coefficient, represents the dynamic response coefficient.

[0031] In some embodiments, performing a system stability analysis based on the minimum landslide rate data, the total system inertia, the total single frequency modulation of the system's new energy, and the total frequency modulation of the battery energy storage system to obtain a frequency stability index includes:

[0032] The following system stability analysis formula is used to calculate the system stability of the power system and obtain the frequency stability index:

[0033] ;

[0034] in, represents the frequency stability index, represents the total inertia of the system, Indicates the total amount of single frequency modulation of the system’s new energy, represents the total frequency regulation of the battery energy storage system, Indicates the minimum data of the landslide rate.

[0035] In some embodiments, performing frequency modulation effect analysis based on the dynamic response coefficient and the frequency stability index to obtain battery energy storage rapid frequency modulation effect data includes:

[0036] The frequency modulation effect of the battery energy storage system is quantitatively calculated using the following formula for quantifying the rapid frequency modulation effect of battery energy storage to obtain the rapid frequency modulation effect data of the battery energy storage:

[0037] ;

[0038] in, represents the battery energy storage rapid frequency modulation effect data of the battery energy storage system at time t, represents the proportional coefficient of the aggregate frequency response ramp rate of the generator to the primary frequency reserve, where the primary frequency reserve represents the reserve capacity reserved in the power system. represents the dynamic response coefficient, represents the frequency stability index, represents the total inertia of the system, represents the time constant of the generator speed control system of the g-th synchronous generator, Indicates the total amount of single frequency modulation of the system’s new energy, Indicates the total frequency regulation of the battery energy storage system.

[0039] To achieve the above-mentioned purpose, a second aspect of an embodiment of the present application provides a device for quantifying the rapid frequency modulation effect of battery energy storage, the device comprising:

[0040] A system parameter acquisition module, used to obtain system parameters of the power system;

[0041] a system inertia calculation module, configured to combine the inertia of the power system based on the system parameters to obtain a total system inertia;

[0042] a frequency deviation analysis module, configured to perform frequency deviation analysis on the power system based on the system parameters and the total inertia of the system to obtain frequency deviation data;

[0043] a landslide rate analysis module, configured to perform frequency response characteristic analysis based on the frequency deviation data, the total inertia of the system, and the system parameters, to obtain a landslide rate of the aggregate frequency response of the generator;

[0044] The frequency modulation effect quantification module is used to quantify the frequency modulation effect based on the system parameters, the total inertia of the system and the aggregate frequency response ramp rate of the generator to obtain battery energy storage rapid frequency modulation effect data.

[0045] To achieve the above-mentioned purpose, the third aspect of an embodiment of the present application proposes an electronic device, which includes a memory and a processor, wherein the memory stores a computer program, and the processor implements the method described in the first aspect when executing the computer program.

[0046] To achieve the above-mentioned purpose, the fourth aspect of the embodiments of the present application proposes a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the method described in the first aspect.

[0047] The method and device, electronic device, and storage medium for quantifying the rapid frequency regulation effect of battery energy storage proposed in this application accurately obtain system parameters of the power system, calculate the total system inertia of the power system, analyze the frequency deviation of the power system, evaluate the aggregate frequency response landslide rate of the generator, and quantify the rapid frequency regulation effect of the battery energy storage system to obtain battery energy storage rapid frequency regulation effect data. This can accurately evaluate and predict the performance of the battery energy storage system in actual operation, thereby improving the power system to enhance the frequency regulation capability of the battery energy storage system, enabling it to more effectively cope with frequency fluctuations in the power system and improve the reliability of the rapid frequency regulation of the battery energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a flow chart of a method for quantifying the rapid frequency modulation effect of battery energy storage provided by an embodiment of the present application;

[0049] Figure 2 is a schematic diagram of the structure of the power system provided in an embodiment of the present application;

[0050] Figure 3 yes Figure 1 Flowchart of step S102 in FIG.

[0051] Figure 4 yes Figure 1 Flowchart of step S103 in FIG.

[0052] Figure 5 yes Figure 1 Flowchart of step S105 in FIG.

[0053] Figure 6 This is a structural diagram of a device for quantifying the rapid frequency modulation effect of battery energy storage provided by an embodiment of the present application;

[0054] Figure 7 This is a schematic diagram of the hardware structure of the electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0056] It should be noted that although the device schematics illustrate functional module divisions and the flowcharts illustrate logical sequences, in certain circumstances, the steps shown or described may be performed in a sequence that differs from the module divisions in the device or the sequence in the flowcharts. The terms "first," "second," and so on, in the specification, claims, and drawings, are used to distinguish similar items and are not necessarily used to describe a specific sequence or precedence.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein are for the purpose of describing the embodiments of this application only and are not intended to limit this application.

[0058] First, let’s analyze some of the terms used in this application:

[0059] Power system: A power system is composed of synchronous generators, renewable energy sources (such as wind and solar), and battery energy storage. Energy storage can be connected at the power source, grid, and load sides. This system uses an analytical model of battery energy storage's rapid frequency regulation to quantify its contribution to system frequency stability. This approach addresses the issues of reduced inertia and increased uncertainty associated with renewable energy integration, thereby improving the frequency security and stability of the power system.

[0060] Battery energy storage rapid frequency regulation refers to the process of regulating frequency changes in the power system by leveraging the rapid response characteristics of battery energy storage systems. With the rapid development of new energy technologies and their large-scale integration into the power system, traditional power systems based on synchronous generators are facing challenges in frequency security and stability. Due to the intermittent and uncertain nature of new energy, the inertia level of the power system is reduced, resulting in a weakened resistance to frequency changes and an increased risk of frequency deviation. As a flexible and rapid frequency regulation resource, battery energy storage systems can quickly respond to disturbances in the power system, providing the necessary power support to maintain the stability of the power system's frequency.

[0061] However, existing research and practice mainly focus on the demand response of energy storage systems and the suppression of renewable energy fluctuations, and lack a mechanistic approach, which leads to unreliable rapid frequency regulation of battery energy storage in power systems. Therefore, how to improve the reliability of rapid frequency regulation of battery energy storage has become a technical problem that needs to be solved urgently.

[0062] Based on this, the embodiments of the present application provide a method and device for quantifying the rapid frequency modulation effect of battery energy storage, an electronic device, and a storage medium, aiming to improve the reliability of rapid frequency modulation of battery energy storage.

[0063] The method and device for quantifying the rapid frequency modulation effect of battery energy storage, the electronic device, and the storage medium provided in the embodiments of the present application are specifically illustrated through the following embodiments. First, the method for quantifying the rapid frequency modulation effect of battery energy storage in the embodiments of the present application is described.

[0064] The embodiments of the present application can acquire and process relevant data based on artificial intelligence technology. Artificial intelligence (AI) refers to the theories, methods, techniques, and application systems that use digital computers or machines controlled by digital computers to simulate, extend, and expand human intelligence, perceive the environment, acquire knowledge, and use that knowledge to achieve optimal results.

[0065] Fundamental AI technologies generally include sensors, dedicated AI chips, cloud computing, distributed storage, big data processing, operating / interaction systems, and mechatronics. AI software technologies primarily encompass computer vision, robotics, biometrics, speech processing, natural language processing, and machine learning / deep learning.

[0066] The method for quantifying the rapid frequency regulation effect of battery energy storage provided in the embodiment of the present application relates to the field of power grid frequency regulation technology. The method for quantifying the rapid frequency regulation effect of battery energy storage provided in the embodiment of the present application can be applied to a terminal, can be applied to a server side, or can be software running in a terminal or a server side. In some embodiments, the terminal can be a smart phone, a tablet computer, a laptop computer, a desktop computer, etc.; the server side can be configured as an independent physical server, or as a server cluster or distributed system composed of multiple physical servers, or as a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, CDN, and big data and artificial intelligence platforms; the software can be an application that implements the method for quantifying the rapid frequency regulation effect of battery energy storage, etc., but is not limited to the above forms.

[0067] The present application can be used in many general or special computer system environments or configurations. For example: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, and the like. The present application can be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, and the like that perform specific tasks or implement specific abstract data types. The present application can also be practiced in distributed computing environments in which tasks are performed by remote processing devices connected via a communication network. In a distributed computing environment, program modules can be located in local and remote computer storage media, including storage devices.

[0068] Figure 1 This is an optional flow chart of the method for quantifying the rapid frequency modulation effect of battery energy storage provided in the embodiment of the present application. Figure 1 The method may include but is not limited to steps S101 to S105.

[0069] Step S101, obtaining system parameters of the power system;

[0070] Step S102: Based on the system parameters, the inertia of the power system is combined to obtain the total inertia of the system;

[0071] Step S103: performing frequency deviation analysis on the power system based on system parameters and system total inertia to obtain frequency deviation data;

[0072] Step S104: performing frequency response characteristic analysis based on the frequency deviation data, the total inertia of the system, and the system parameters to obtain the aggregate frequency response ramp rate of the generator;

[0073] Step S105 , based on the system parameters, the total system inertia and the aggregate frequency response ramp rate of the generator, the frequency modulation effect is quantified to obtain the battery energy storage rapid frequency modulation effect data.

[0074] In the steps S101 to S105 shown in the embodiment of the present application, by obtaining the system parameters of the power system, performing inertia merging to calculate the total inertia of the power system, obtaining the total system inertia, and then using the system parameters and the total system inertia to analyze the frequency deviation of the power system to obtain frequency deviation data, and then based on the frequency deviation data, the total system inertia and the system parameters, performing frequency response characteristic analysis to obtain the generator aggregate frequency response landslide rate, and finally, based on the system parameters, the total system inertia and the generator aggregate frequency response landslide rate, quantifying the rapid frequency regulation effect of the battery energy storage to obtain the battery energy storage rapid frequency regulation effect data. Therefore, the present application can accurately evaluate and predict the performance of the battery energy storage system in actual operation by accurately obtaining the system parameters of the power system, calculating the total system inertia of the power system, analyzing the frequency deviation of the power system, evaluating the generator aggregate frequency response landslide rate, and quantifying the rapid frequency regulation effect of the battery energy storage system to obtain the battery energy storage rapid frequency regulation effect data.

[0075] See also Figure 2 As shown, in step S101 of some embodiments, the power system refers to a complex network consisting of power generation, transmission, transformation, distribution and consumption, and is mainly used to transmit electric energy from the power generation source to the user and ensure its safe, stable and efficient operation. Furthermore, the power system usually integrates a new energy module, an energy storage module and a synchronous generator module, wherein the new energy module refers to the use of renewable energy for frequency modulation, such as wind energy, solar energy, hydropower, etc., which is generally set on the load side of the power system; the energy storage module, i.e., a battery energy storage system, refers to a device that can store and release electric energy and can be set on the power supply side, grid side and load side of the power system; the synchronous generator module is used to provide stable power output and maintain the frequency and voltage stability of the power system, and is set on the power supply side of the power system.

[0076] In the embodiment of the present application, the system parameters include the operating status of the synchronous generator, the speed regulation system time constant, the inertia time constant, the maximum generated power, the maximum generator loss power, the frequency response delay time, and the rated frequency, minimum frequency, and dead-zone frequency of the power system. In addition, the system parameters also include the frequency of rapid frequency regulation provided by the battery energy storage system, the total frequency regulation of the battery energy storage system, the total single frequency regulation of the system's new energy, the response time of primary frequency regulation provided by new energy, the proportional coefficient of the synchronous generator frequency response ramp rate and the primary frequency reserve, the constant coefficient, etc.

[0077] It should be noted that the operating states of the synchronous generator include the startup state and the shutdown state. The speed regulation system time constant is a parameter used to indicate the response speed of the synchronous generator module. Specifically, the larger the speed regulation system time constant, the slower the response of the synchronous generator module. The inertia time constant is used to indicate the ability of the synchronous generator module to maintain its original speed. The maximum generated power refers to the maximum power that the synchronous generator module can output. The maximum generator power loss refers to the power loss caused by the maximum generator failure that may occur in the power system. The frequency response delay time indicates the delay time for the synchronous generator module to respond to frequency changes. The rated power refers to the standard frequency during normal operation of the power system. The minimum frequency refers to the lowest frequency allowed during power system operation. The power system deadband frequency refers to the frequency deviation range allowed by the power system. The frequency provided by the battery energy storage system for rapid frequency regulation refers to the target frequency of the power system when the battery energy storage system participates in rapid frequency regulation. The total frequency regulation capacity of the battery energy storage system refers to the total power that the battery energy storage system can provide for rapid frequency regulation. The total frequency regulation capacity of the system's new energy modules refers to the power adjustment capacity provided by the new energy modules during a single frequency regulation. The response time of renewable energy for primary frequency regulation refers to the time it takes for the renewable energy module to respond to frequency changes. The proportional coefficient between the synchronous generator's frequency response ramp rate and the primary frequency reserve is used to describe the relationship between the synchronous generator module's frequency response ramp rate and the primary frequency reserve. This constant coefficient appears as a fixed factor in the frequency regulation effect calculation and is often used to adjust and optimize the frequency regulation effect calculation formula to ensure the accuracy of the results.

[0078] In the embodiment of the present application, the system parameters of the power system can be obtained by querying the power system operator, and the system parameters of the power system can also be obtained by querying the databases of relevant metering departments, power plants, energy storage power stations, market trading departments and other units.

[0079] In step S102 of some embodiments, the total system inertia refers to the ability of the power system to resist frequency changes.

[0080] In an embodiment of the present application, the number of running synchronous generators can be determined based on the operating status of the synchronous generators in the system parameters, and then the resistance of each running synchronous generator to frequency changes can be calculated. Finally, the resistance of the synchronous generators to frequency changes is summarized to obtain the total system inertia of the power system.

[0081] For details, see Figure 3 In some embodiments, step S102 may include but is not limited to steps S301 to S304:

[0082] Step S301, identifying faulty motors in the power system to obtain the number of faulty generators;

[0083] Step S302, determining the number of non-faulty generators based on the number of faulty generators and the total number of generators;

[0084] Step S303, calculating the generator inertia based on the inertia time constant, the maximum power generation and the number of non-faulty generators to obtain the generator inertia;

[0085] Step S304: Merge the generator inertia data to obtain the total system inertia.

[0086] In some embodiments, in steps S301 and S302, the number of faulty generators refers to the number of synchronous generators in a shutdown state. The total number of generators refers to the total number of synchronous generators in the power system. The number of non-faulty generators refers to the number of synchronous generators in a startup state.

[0087] In an embodiment of the present application, the number of synchronous generators in a stopped state, that is, the number of faulty generators, can be determined based on the operating status of the synchronous generators in the system parameters. Furthermore, based on the number of synchronous generators and the number of faulty generators recorded in the power system, the number of synchronous generators in a started state can be estimated, and the number of non-faulty generators can be obtained.

[0088] In step S303 and step S304 of some embodiments, the calculation may be based on the sum of the products of the inertia time constants of all synchronous generators in the power system and their maximum power generation and the operating status of the synchronous generators.

[0089] In detail, the total system inertia of the power system can be calculated using the following system inertia formula:

[0090] ;

[0091] in, represents the inertia time constant of the g-th synchronous generator, represents the maximum power generation of the g-th synchronous generator, Indicates the number of non-faulty generators, Indicates the operating status of the g-th synchronous generator.

[0092] In some embodiments, in steps S301 to S304, faulty motors are identified in the power system to determine the number of faulty generators. Based on the number of faulty generators, the number of intact generators is determined. Next, the inertia of the synchronous generators is calculated based on the inertia time constant, maximum power generation, and the number of intact generators to determine the generator inertia. Finally, the generator inertia data is merged to determine the total system inertia. This lays the foundation for quantifying the rapid frequency regulation effect of battery energy storage, enabling the battery energy storage system to adjust its frequency regulation strategy based on the total system inertia of the power system to ensure that the system frequency stability can be effectively supported under different inertia conditions.

[0093] In step S103 of some embodiments, the frequency deviation data includes a first deviation frequency and a second deviation frequency. The first deviation frequency refers to the difference between the frequency when the power system enters the frequency regulation dead zone and the frequency when the battery energy storage system begins to provide frequency regulation services. The second deviation frequency refers to the difference between the frequency when the battery energy storage system provides rapid frequency regulation services and the minimum frequency at which the power system can operate stably. It should also be noted that the frequency regulation dead zone refers to the point where the frequency deviation of the power system reaches a threshold that requires the battery energy storage system to perform frequency regulation.

[0094] In an embodiment of the present application, a frequency deviation analysis can be performed based on the dead-zone frequency of the power system and the current system frequency of the power system to obtain a first deviation frequency. Then, based on the first deviation frequency, a battery energy storage system can be used to perform rapid frequency modulation to obtain a system frequency modulation frequency. Then, a frequency difference calculation is performed based on the system frequency modulation frequency and the minimum stable frequency of the power system to obtain a second deviation frequency. Finally, the first deviation frequency and the second deviation frequency are integrated to obtain frequency deviation data.

[0095] For details, see Figure 4 In some embodiments, step S103 may include but is not limited to steps S401 to S405:

[0096] Step S401, obtaining the current frequency of the power system;

[0097] Step S402, calculating a frequency difference between the power system and the power system based on the dead-zone frequency of the power system and the current frequency of the system to obtain a first deviation frequency;

[0098] Step S403: performing frequency modulation on the power system based on the first deviation frequency to obtain a system frequency modulation frequency;

[0099] Step S404: performing a secondary frequency difference calculation on the power system based on the system frequency modulation frequency and the minimum stable frequency of the power system to obtain a second deviation frequency;

[0100] In step S405 , the first deviation frequency and the second deviation frequency are integrated to obtain frequency deviation data.

[0101] In step S401 of some embodiments, the current system frequency refers to the frequency data at the current moment after a disturbance occurs in the power system.

[0102] In an embodiment of the present application, the frequency data of the power system can be monitored in real time by a frequency measuring device installed in the power system. Furthermore, a data acquisition system can be used to collect the frequency data and perform frequency analysis on the frequency data, so as to obtain the current frequency of the system.

[0103] In step S402 of some embodiments, the first deviation frequency can be determined by calculating the difference between the power system dead-zone frequency and the current system frequency. For example, when the power system dead-zone frequency is set to 49.8 Hz, if the electronic system frequency drops to 49.7 Hz due to a sudden increase in load at a certain moment, the battery energy storage system begins to intervene to provide frequency regulation services. At this time, the first deviation frequency is 49.8 Hz − 49.7 Hz = 0.1 Hz.

[0104] In detail, the present application can calculate the first deviation frequency between the dead zone frequency of the power system and the current frequency of the system by the following first deviation frequency calculation formula:

[0105] ;

[0106] in, represents the first deviation frequency, Indicates the dead-zone frequency of the power system, Indicates the current system frequency of the power system.

[0107] In step S403 of some embodiments, when the first deviation frequency indicates that the frequency of the power system is already lower than the dead-zone frequency of the power system, it indicates that the battery energy storage system needs to intervene to provide frequency regulation services. Therefore, the battery energy storage system is used to store or release electric energy to achieve rapid frequency regulation of the power system, thereby obtaining the frequency of the power system after the battery energy storage system provides frequency regulation, that is, the system frequency regulation frequency.

[0108] In step S404 of some embodiments, the second deviation frequency can be determined by calculating the difference between the system frequency modulation frequency and the minimum stable frequency of the power system. For example, when the minimum stable frequency of the power system is 49.5 Hz, the frequency of the power system drops from 50 Hz to 49.7 Hz, and after the battery energy storage system intervenes, the system frequency recovers from 49.7 Hz to 49.9 Hz, then the second deviation frequency is 49.9 Hz − 49.5 Hz = 0.4 Hz.

[0109] In detail, the present application can calculate the second deviation frequency of the power system by the following second deviation frequency calculation formula:

[0110] ;

[0111] in, represents the second deviation frequency, Indicates the system frequency modulation frequency of the power system, Indicates the minimum stable frequency of the power system.

[0112] In step S405 of some embodiments, frequency deviation data may be obtained by filling the first deviation frequency and the second deviation frequency into a preset frequency deviation table.

[0113] In steps S401 to S405 of some embodiments, a frequency deviation analysis can be performed on the power system based on the acquired current system frequency of the power system and the dead-zone frequency of the power system to obtain a first deviation frequency. Furthermore, based on the first deviation frequency, the power system is rapidly frequency-modulated to obtain a system frequency modulation frequency. Secondly, based on the system frequency modulation frequency and the minimum stable frequency of the power system, a frequency difference calculation is performed on the power system to obtain a second deviation frequency. Finally, data integration is performed on the first deviation frequency and the second deviation frequency to obtain frequency deviation data.

[0114] In step 104 of some embodiments, the generator aggregate frequency response landslide rate refers to the rate at which the synchronous generator frequency decreases when a disturbance occurs in the power system. It should be noted that the smaller the generator aggregate frequency response landslide rate, the stronger the synchronous generator's resistance to frequency decrease and the better the frequency stability of the power system.

[0115] In the embodiment of the present application, the frequency response rate of the power system can be simulated based on the system parameters of the power system and a pre-built traditional synchronous generator aggregate frequency response landslide rate model to obtain the generator aggregate frequency response landslide rate.

[0116] In detail, the frequency response characteristics can be analyzed based on system parameters such as the rated frequency, minimum frequency, system loss, frequency response delay time, the vector consisting of the response time of primary frequency regulation provided by new energy, the total amount of rapid frequency regulation provided by battery energy storage, and the total inertia and frequency deviation data of the above-mentioned system to obtain the generator aggregate frequency response landslide rate.

[0117] In the embodiment of the present application, the following landslide rate calculation formula can be used to calculate the aggregate frequency response landslide rate of the generators in the power system:

[0118] ;

[0119] ;

[0120] ;

[0121] ;

[0122] in, represents the generator aggregate frequency response ramp rate, It represents the total frequency regulation provided by the battery energy storage system during the rapid frequency regulation of the power system. Indicates the maximum generator loss power in the power system, Indicates the total amount of single frequency modulation of the system's new energy. It indicates the difference between the power loss of the largest generator in the power system and the total amount of primary frequency regulation provided by the new energy module. It is used to reflect the power shortage that the traditional synchronous generator actually needs to compensate for in the power system when new energy participates in frequency regulation. Indicates the total frequency regulation of the battery energy storage system, represents the frequency response delay time of the power system, Indicates the frequency deviation caused by the frequency response delay time, It indicates the correction value of the frequency deviation caused by the frequency response delay time after the influence of factors such as the new energy response time. It represents the vector formed by the response time of the new energy in the power system to provide primary frequency regulation, represents the total inertia of the system, Indicates the rated frequency of the power system.

[0123] In step S105 of some embodiments, after obtaining the system parameters of the power system and calculating the total system inertia of the power system and the generator aggregate frequency response landslide rate of the synchronous generator using the system parameters, the effect of the power system frequency regulation can be quantitatively quantified by using a pre-built analytical model of the energy storage rapid frequency regulation effect of new energy participating in rapid frequency regulation.

[0124] For details, see Figure 5 In some embodiments, step S105 may include but is not limited to steps S501 to S504:

[0125] Step S501, estimating the minimum value of the landslide rate of the aggregate frequency response of the generator to obtain minimum landslide rate data;

[0126] Step S502: Perform dynamic response analysis based on the total inertia of the system and the time constant of the generator speed control system to obtain a dynamic response coefficient;

[0127] Step S503: Perform system stability analysis based on the minimum landslide rate data, the total system inertia, the total single frequency modulation of the system's new energy resources, and the total frequency modulation of the battery energy storage system to obtain a frequency stability index;

[0128] Step S504: Analyze the frequency modulation effect based on the dynamic response coefficient and the frequency stability index to obtain battery energy storage rapid frequency modulation effect data.

[0129] In step S501 of some embodiments, the minimum landslide rate data refers to the minimum value of the landslide rate of the aggregated frequency response of the generators that meets the frequency deviation safety constraint.

[0130] In an embodiment of the present application, by substituting the first deviation frequency and the second deviation frequency of the power system into the above-mentioned landslide rate calculation formula, adding the frequency deviation safety constraint, and performing minimum value estimation, the minimum landslide rate data of each frequency adjustment of the power system can be obtained.

[0131] In detail, the present application can calculate the minimum landslide rate data that meets the frequency deviation safety constraint by using the following landslide rate minimum data calculation formula:

[0132] ;

[0133] in, Indicates the minimum data of landslide rate, represents the total amount of fast frequency regulation provided by the battery energy storage system, represents the second deviation frequency, represents the first deviation frequency, represents the total inertia of the system, Indicates the rated frequency of the power system, Indicates the maximum generator loss power in the power system, represents the frequency response delay time of the power system, It represents the vector formed by the response time of the new energy in the power system to provide primary frequency regulation, It represents the total amount of primary frequency regulation provided by renewable energy. It indicates the difference between the power loss of the largest generator in the power system and the total amount of primary frequency regulation provided by renewable energy. It is used to reflect the power shortage that the power system actually needs to compensate with traditional synchronous generators when renewable energy participates in frequency regulation. Indicates the total amount of fast frequency regulation provided by the battery energy storage system.

[0134] In step S502 of some embodiments, the dynamic response coefficient represents the influence of the total inertia of the system and the speed regulation time constant of the synchronous generator on the frequency regulation effect of the power system.

[0135] In the embodiment of the present application, the following dynamic response coefficient calculation formula can be used to calculate the system dynamic characteristics of the power system to obtain the dynamic response coefficient:

[0136] ;

[0137] in, represents the total inertia of the system, represents the time constant of the generator speed control system of the g-th synchronous generator, represents the first constant coefficient, represents the second constant coefficient, represents the third constant coefficient, Represents the dynamic response coefficient.

[0138] In step S503 of some embodiments, the frequency stability index refers to the time from when the battery energy storage system provides rapid frequency regulation to when the power system reaches the minimum stable frequency of the power system.

[0139] The following system stability analysis formula can be used to calculate the system stability of the power system and obtain the frequency stability index:

[0140] ;

[0141] in, represents the frequency stability index, represents the total inertia of the system, Indicates the total amount of single frequency modulation of the system's new energy. Indicates the total frequency regulation of the battery energy storage system, Indicates the minimum landslide rate data.

[0142] In step S504 of some embodiments, the battery energy storage rapid frequency regulation effect data is used to represent the rapid frequency regulation effect of the battery energy storage system at any time point.

[0143] In the embodiment of the present application, the following formula for quantifying the rapid frequency modulation effect of battery energy storage can be used to quantify the frequency modulation effect of the battery energy storage system to obtain the rapid frequency modulation effect data of the battery energy storage:

[0144] ;

[0145] in, It represents the battery energy storage rapid frequency modulation effect data of the battery energy storage system at time t, It represents the proportional coefficient of the aggregate frequency response ramp rate of the generator and the primary frequency reserve. The primary frequency reserve represents the reserve capacity reserved in the power system. represents the dynamic response coefficient, represents the frequency stability index, represents the total inertia of the system, represents the time constant of the generator speed control system of the g-th synchronous generator, Indicates the total amount of single frequency modulation of the system's new energy. Indicates the total frequency regulation of the battery energy storage system.

[0146] In steps S501 to S504 of this embodiment, a minimum landslide rate estimate is performed on the aggregated frequency response of the generator to obtain minimum landslide rate data. Then, a dynamic response analysis is performed based on the total system inertia and the time constant of the generator speed regulation system to obtain a dynamic response coefficient. Furthermore, a system stability analysis is performed based on the minimum landslide rate data and system parameters to obtain a frequency stability index. Finally, based on the system parameters, the dynamic response coefficient, and the frequency stability index, the rapid frequency regulation effect of the battery energy storage is analyzed to obtain rapid frequency regulation effect data of the battery energy storage. This allows for quantitative quantification of the rapid frequency regulation effect of the battery energy storage system, thereby facilitating the formulation of a suitable power system rapid frequency regulation scheme based on the rapid frequency regulation effect of the battery energy storage system, thereby improving the reliability of the power system rapid frequency regulation.

[0147] This application obtains battery energy storage rapid frequency regulation effect data by accurately acquiring the system parameters of the power system, calculating the total system inertia of the power system, analyzing the frequency deviation of the power system, evaluating the aggregate frequency response landslide rate of the generator, and quantifying the rapid frequency regulation effect of the battery energy storage system. This can accurately evaluate and predict the performance of the battery energy storage system in actual operation, thereby improving the power system to enhance the frequency regulation capability of the battery energy storage system, enabling it to more effectively cope with frequency fluctuations in the power system and improve the reliability of the battery energy storage rapid frequency regulation.

[0148] See also Figure 6 The embodiment of the present application further provides a device for quantifying the rapid frequency modulation effect of battery energy storage, which can implement the above-mentioned method for quantifying the rapid frequency modulation effect of battery energy storage, and the device includes:

[0149] System parameter acquisition module 601, used to obtain system parameters of the power system;

[0150] The system inertia calculation module 602 is used to combine the inertia of the power system based on the system parameters to obtain the total inertia of the system;

[0151] The frequency deviation analysis module 603 is used to perform frequency deviation analysis on the power system based on system parameters and system total inertia to obtain frequency deviation data;

[0152] The landslide rate analysis module 604 is used to perform frequency response characteristic analysis based on frequency deviation data, system total inertia and system parameters to obtain the generator aggregate frequency response landslide rate;

[0153] The frequency modulation effect quantification module 605 is used to quantify the frequency modulation effect based on system parameters, total system inertia and generator aggregate frequency response ramp rate to obtain battery energy storage rapid frequency modulation effect data.

[0154] The specific implementation of the device for quantifying the rapid frequency modulation effect of battery energy storage is basically the same as the specific embodiment of the method for quantifying the rapid frequency modulation effect of battery energy storage, and will not be repeated here.

[0155] The present application also provides an electronic device comprising a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the aforementioned method for quantifying the rapid frequency modulation effect of battery energy storage. The electronic device can be any smart terminal, including a tablet computer and an in-vehicle computer.

[0156] See also Figure 7 , Figure 7 The hardware structure of an electronic device according to another embodiment is shown. The electronic device includes:

[0157] The processor 701 may be implemented as a general-purpose CPU (Central Processing Unit), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of the present application.

[0158] The memory 702 can be implemented in the form of a read-only memory (ROM), a static storage device, a dynamic storage device, or a random access memory (RAM). The memory 702 can store an operating system and other application programs. When the technical solutions provided in the embodiments of this specification are implemented through software or firmware, the relevant program code is stored in the memory 702 and is called by the processor 701 to execute the battery energy storage rapid frequency modulation effect quantification method of the embodiment of the present application;

[0159] Input / output interface 703, used to implement information input and output;

[0160] Communication interface 704, used to implement communication interaction between this device and other devices, which can be achieved through wired means (such as USB, network cable, etc.) or wireless means (such as mobile network, WiFi, Bluetooth, etc.);

[0161] Bus 705 , which transmits information between various components of the device (e.g., processor 701 , memory 702 , input / output interface 703 , and communication interface 704 );

[0162] The processor 701 , the memory 702 , the input / output interface 703 and the communication interface 704 are connected to each other in communication within the device via a bus 705 .

[0163] An embodiment of the present application further provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the above-mentioned method for quantifying the rapid frequency modulation effect of battery energy storage.

[0164] The memory, as a non-transient computer-readable storage medium, can be used to store non-transient software programs and non-transient computer executable programs. In addition, the memory may include a high-speed random access memory and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some embodiments, the memory may optionally include a memory remotely arranged relative to the processor, and these remote memories may be connected to the processor via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0165] The embodiments of the present application provide a method for quantifying the rapid frequency modulation effect of battery energy storage, a device for quantifying the rapid frequency modulation effect of battery energy storage, an electronic device, and a storage medium. These methods obtain system parameters of a power system, perform inertia merging to calculate the total inertia of the power system, and obtain the total system inertia. The system parameters and the total system inertia are then used to perform frequency deviation analysis on the power system to obtain frequency deviation data. Furthermore, based on the frequency deviation data, the total system inertia, and the system parameters, a frequency response characteristic analysis is performed to obtain the aggregated frequency response landslide rate of the generator. Finally, based on the system parameters, the total system inertia, and the aggregated frequency response landslide rate of the generator, the rapid frequency modulation effect of battery energy storage is quantified to obtain the rapid frequency modulation effect data of battery energy storage.

[0166] The embodiments described in the embodiments of this application are intended to more clearly illustrate the technical solutions of the embodiments of this application and do not constitute a limitation on the technical solutions provided by the embodiments of this application. Those skilled in the art will appreciate that with the evolution of technology and the emergence of new application scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0167] Those skilled in the art will understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of the present application, and may include more or fewer steps than shown in the figures, or a combination of certain steps, or different steps.

[0168] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, i.e., they may be located in one place or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of this embodiment.

[0169] Those skilled in the art will appreciate that all or some of the steps in the methods, systems, and functional modules / units in the devices disclosed above may be implemented as software, firmware, hardware, or appropriate combinations thereof.

[0170] The terms "first", "second", "third", "fourth", etc. (if any) in the specification of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0171] It should be understood that in this application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0172] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the above-mentioned units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. The mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0173] The units described above as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0174] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0175] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes multiple instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of various embodiments of the present application. The aforementioned storage medium includes: various media that can store programs, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0176] The preferred embodiments of the present invention are described above with reference to the accompanying drawings, but are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and essence of the present invention should be within the scope of the present invention.

Claims

1. A method for quantifying the rapid frequency modulation effect of battery energy storage, applied to a battery energy storage system, characterized in that: The method comprises: Obtaining system parameters of the power system; Based on the system parameters, performing inertia merging on the power system to obtain a total system inertia; performing frequency deviation analysis on the power system based on the system parameters and the total inertia of the system to obtain frequency deviation data; Performing frequency response characteristic analysis based on the frequency deviation data, the total inertia of the system, and the system parameters to obtain a generator aggregate frequency response landslide rate; Based on the system parameters, the total inertia of the system and the aggregate frequency response ramp rate of the generator, the frequency regulation effect is quantified to obtain battery energy storage rapid frequency regulation effect data.

2. The method according to claim 1, characterized in that The system parameters include a dead-zone frequency of the power system and a minimum stable frequency of the power system. The frequency deviation analysis of the power system is performed based on the system parameters, the system parameters and the total inertia of the system to obtain frequency deviation data, including: Obtaining a current frequency of the power system; Calculating a frequency difference of the power system based on the dead-zone frequency of the power system and the current frequency of the system to obtain a first deviation frequency; Based on the first deviation frequency, frequency modulation is performed on the power system to obtain a system frequency modulation frequency; Based on the system frequency modulation frequency and the minimum stable frequency of the power system, performing a secondary frequency difference calculation on the power system to obtain a second deviation frequency; Data integration is performed on the first deviation frequency and the second deviation frequency to obtain the frequency deviation data.

3. The method according to claim 1, characterized in that The system parameters include the total number of generators, the inertia time constant, and the maximum power generation. Based on the system parameters, the inertia merging of the power system to obtain the total system inertia includes: Identifying faulty motors in the power system to obtain the number of faulty generators; Determining the number of non-faulty generators based on the number of faulty generators and the total number of generators; Calculating the generator inertia based on the inertia time constant, the maximum generated power, and the number of non-faulty generators to obtain the generator inertia; The generator inertia is data merged to obtain the total inertia of the system.

4. The method according to claim 1, wherein The system parameters include the generator speed regulation system time constant, the total single frequency regulation of the system's new energy, and the total frequency regulation of the battery energy storage system. Based on the system parameters, the total inertia of the system, and the aggregate frequency response ramp rate of the generator, the frequency regulation effect is quantified to obtain the battery energy storage rapid frequency regulation effect data, including: Predicting a minimum value of the landslide rate of the aggregate frequency response of the generator to obtain minimum landslide rate data; Performing a dynamic response analysis based on the total inertia of the system and the time constant of the generator speed control system to obtain a dynamic response coefficient; Based on the minimum landslide rate data, the total inertia of the system, the total single frequency modulation of the system's new energy, and the total frequency modulation of the battery energy storage system, a system stability analysis is performed to obtain a frequency stability index; Based on the dynamic response coefficient and the frequency stability index, the frequency modulation effect is analyzed to obtain the battery energy storage rapid frequency modulation effect data.

5. The method according to claim 4, characterized in that The dynamic response analysis is performed based on the total inertia of the system and the time constant of the generator speed control system to obtain the dynamic response coefficient, including: The dynamic response coefficient is calculated by calculating the dynamic characteristics of the power system using the following dynamic response coefficient calculation formula: ； in, represents the total inertia of the system, represents the time constant of the generator speed control system of the g-th synchronous generator, Represents the preset first constant coefficient, Represents the preset second constant coefficient, Represents the preset third constant coefficient, represents the dynamic response coefficient.

6. The method according to claim 4, characterized in that The system stability analysis is performed based on the minimum landslide rate data, the total system inertia, the total single frequency modulation amount of the system's new energy, and the total frequency modulation amount of the battery energy storage system to obtain a frequency stability index, including: The following system stability analysis formula is used to calculate the system stability of the power system and obtain the frequency stability index: ； in, represents the frequency stability index, represents the total inertia of the system, Indicates the total amount of single frequency modulation of the system’s new energy, represents the total frequency regulation of the battery energy storage system, Indicates the minimum data of the landslide rate.

7. The method according to claim 4, characterized in that The frequency modulation effect analysis is performed based on the dynamic response coefficient and the frequency stability index to obtain battery energy storage rapid frequency modulation effect data, including: The frequency modulation effect of the battery energy storage system is quantitatively calculated using the following formula for quantifying the rapid frequency modulation effect of battery energy storage to obtain the rapid frequency modulation effect data of the battery energy storage: ； in, represents the battery energy storage rapid frequency modulation effect data of the battery energy storage system at time t, represents the proportional coefficient of the aggregate frequency response ramp rate of the generator to the primary frequency reserve, where the primary frequency reserve represents the reserve capacity reserved in the power system, represents the dynamic response coefficient, represents the frequency stability index, represents the total inertia of the system, represents the time constant of the generator speed control system of the g-th synchronous generator, Indicates the total amount of single frequency modulation of the system’s new energy, Indicates the total frequency regulation of the battery energy storage system.

8. A device for quantifying the rapid frequency modulation effect of battery energy storage, characterized in that: The device comprises: A system parameter acquisition module, used to obtain system parameters of the power system; a system inertia calculation module, configured to combine the inertia of the power system based on the system parameters to obtain a total system inertia; a frequency deviation analysis module, configured to perform frequency deviation analysis on the power system based on the system parameters and the total inertia of the system to obtain frequency deviation data; a landslide rate analysis module, configured to perform frequency response characteristic analysis based on the frequency deviation data, the total inertia of the system, and the system parameters, to obtain a landslide rate of the aggregate frequency response of the generator; The frequency modulation effect quantification module is used to quantify the frequency modulation effect based on the system parameters, the total inertia of the system and the aggregate frequency response ramp rate of the generator to obtain battery energy storage rapid frequency modulation effect data.

9. An electronic device, characterized in that: The electronic device includes a memory and a processor, the memory stores a computer program, and when the processor executes the computer program, it implements the method for quantifying the rapid frequency modulation effect of battery energy storage as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method for quantifying the rapid frequency modulation effect of battery energy storage according to any one of claims 1 to 7 is implemented.

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