Power system frequency modulation capability demand evaluation method considering frequency fluctuation characteristics

Abstract

The invention belongs to the application field of power system frequency regulation, and particularly relates to a power system frequency modulation capability demand evaluation method considering frequency fluctuation characteristics, which comprises the following steps: S1, constructing power system frequency fluctuation characteristic indexes, and extracting and drawing a frequency fluctuation curve of an out-of-limit part by taking a set frequency dead zone as a boundary; based on the fluctuation curve of the out-of-limit frequency, frequency fluctuation characteristic indexes are provided to comprehensively describe frequency fluctuation characteristics under the daily time scale; s2, establishing a mathematical model of the frequency fluctuation characteristic index and the frequency modulation capability demand, and mapping the associated power system frequency modulation capability demand by using the frequency fluctuation characteristic index; and S3, verifying the effectiveness of the evaluation method. According to the method, the daily frequency modulation capability demand of the power system is quantitatively evaluated only through the fluctuation curve of the frequency, the influence of frequency modulation characteristics of different adjustment resources on the frequency modulation capability demand is revealed, and guidance is provided for frequency modulation resource configuration.

Description

Technical Field

[0001] The present invention belongs to the application field of power system frequency regulation, and particularly relates to a method for evaluating the demand for frequency regulation capacity of a power system considering frequency fluctuation characteristics. Background Art

[0002] China is continuously strengthening the strategic deployment of energy low-carbon transformation. Building a new power system has become an inevitable trend of development, and new energy sources such as wind and light have gradually replaced traditional energy sources such as thermal power. Different from synchronous machines that can stably output frequency regulation power to maintain frequency stability, new energy sources such as wind power have intermittency and strong volatility, resulting in increasingly severe frequency fluctuations and more serious frequency over-limit problems in the new power system. The primary frequency regulation equipment needs to operate continuously, seriously affecting the service life of the equipment and the safe operation of the power system. Therefore, configuring sufficient primary frequency regulation capacity for the power system is of great significance for suppressing frequency fluctuations and ensuring power balance.

[0003] Accurately identifying frequency fluctuation characteristics is the basis for evaluating the demand for frequency regulation capacity. Existing technologies indicate that frequency fluctuations have Gaussian distribution characteristics on short time scales and do not have Gaussian distribution characteristics on long time scales. This is because the continuous access of new energy sources leads to asymmetric frequency regulation capacity in the power system, resulting in an asymmetric skewed distribution of frequency. Therefore, it is necessary to develop the frequency regulation control capabilities of new energy sources and energy storage to suppress the development of the frequency distribution characteristics of the power system towards a new distribution trend. However, only constructing characteristic indicators from the geometric form of frequency fluctuations ignores the power balance problem behind the fluctuations, especially does not characterize the frequency fluctuation characteristics from the perspective of the primary frequency regulation demand brought by the fluctuations. For the method for evaluating the demand for frequency regulation capacity of the power system, existing technologies have all evaluated the demand for the primary frequency regulation capacity of energy storage under large disturbances, and have not quantitatively evaluated the demand for the frequency regulation capacity of the power system from the perspective of suppressing frequency fluctuations and reducing frequency over-limits.

[0004] In summary, there is an urgent need for a method in the existing technology that can consider the frequency fluctuation characteristics of the new power system and realize the evaluation of the demand for the frequency regulation capacity of the power system to solve the problem of frequent frequency over-limits in the new power system. Summary of the Invention

[0005] In order to solve the technical problems existing in the prior art that the method for evaluating the demand for the frequency regulation capacity of the power system only constructs characteristic indicators from the geometric form of frequency fluctuations, ignores the power balance problem behind the fluctuations, especially does not characterize the frequency fluctuation characteristics from the perspective of the primary frequency regulation demand brought by the fluctuations, and existing technologies have all evaluated the demand for the primary frequency regulation capacity of energy storage under large disturbances and have not quantitatively evaluated the demand for the frequency regulation capacity of the power system from the perspective of suppressing frequency fluctuations and reducing frequency over-limits, the embodiments of the present invention provide a method for evaluating the demand for the frequency regulation capacity of a power system considering frequency fluctuation characteristics. The technical solution is as follows:

[0006] The present invention provides a method for evaluating the frequency regulation capacity demand of a power system considering frequency fluctuation characteristics. A method for evaluating the frequency regulation capacity demand of a power system considering frequency fluctuation characteristics is characterized in that the method includes:

[0007] S1. Construct frequency fluctuation characteristic indexes of the power system. Using a set frequency dead zone as the boundary, extract and plot the frequency fluctuation curve of the over-limit part; based on the fluctuation curve of the over-limit frequency, propose frequency fluctuation characteristic indexes to comprehensively characterize the frequency fluctuation characteristics on a daily time scale.

[0008] S2. Establish a mathematical model between the frequency fluctuation characteristic indexes and the frequency regulation capacity demand. This mathematical model maps the frequency regulation demand of the power system associated with the frequency fluctuation characteristic indexes.

[0009] S3. Verify the effectiveness of the proposed method: Select an actual regional power grid as the example power system, calculate the frequency fluctuation characteristic indexes and the frequency regulation capacity demand of the power system based on the measured frequency data of the power system, and analyze the influence of the frequency regulation characteristics of different regulation resources on the frequency regulation capacity demand.

[0010] The beneficial effects brought by the technical solution provided by the embodiment of the present invention at least include:

[0011] The present invention first constructs a frequency fluctuation characteristic index system on a daily time scale based on the measured daily frequency fluctuation curve, and reveals the frequency fluctuation characteristics from multiple angles such as the maximum amplitude, time ratio, maximum duration and over-limit times of the over-limit frequency; on this basis, constructs a mathematical model between the frequency fluctuation index and the frequency regulation capacity demand, and realizes the quantitative evaluation of the daily frequency regulation capacity demand of the power system only from the frequency fluctuation curve. Finally, based on the measured frequency data and waveforms, reveals the influence of the frequency regulation characteristics of different regulation resources on the frequency regulation capacity demand, and provides guidance for the configuration of frequency regulation resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0013] Figure 1 is a flowchart of a method for evaluating the frequency regulation capacity demand of a power system considering frequency fluctuation characteristics provided by an embodiment of the present invention;

[0014] Figure 2 is a flowchart for evaluating the frequency regulation capacity demand provided in S2 in an embodiment of the present invention;

[0015] Figure 3It is the frequency fluctuation curve diagram on the daily time scale;

[0016] Figure 4 It is the distribution diagram of system frequency regulation power demand on daily time scale;

[0017] Figure 5 It is the distribution diagram of system frequency regulation power demand on a daily time scale;

[0018] Figure 6 This is the distribution diagram of the system frequency regulation power net demand on a daily time scale. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0020] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0021] In the embodiments of the present invention, "image" and "picture" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they intend to express are the same. "of", "corresponding, relevant" and "corresponding" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they intend to express are the same.

[0022] In the embodiments of the present invention, sometimes a subscript such as W1 may be written as a non-subscript such as W1. When the difference is not emphasized, the meanings to be expressed are the same.

[0023] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0024] The embodiment of the present invention provides a method for evaluating the frequency regulation capability requirement of a power system taking into account the frequency fluctuation characteristics, such as Figure 1 As shown, the method comprises the following steps:

[0025] S1. Construct the frequency fluctuation characteristic index of the power system; take the set frequency dead zone as the boundary, extract and draw the frequency fluctuation curve of the over-limit part; based on the fluctuation curve of the over-limit frequency, propose the frequency fluctuation characteristic index to comprehensively characterize the frequency fluctuation characteristics on the daily time scale.

[0026] To cope with the inevitable small - scale frequency fluctuations in the power system, a frequency dead - zone is generally set. If the frequency is within the dead - zone, the active power imbalance in the power system is small and does not affect the safe operation of the power system, and no frequency regulation is required. When the frequency fluctuation exceeds the dead - zone range, the active power imbalance is large, which poses a threat to the safe operation of the power system. The power system needs to have sufficient frequency - modulation capacity to restore the frequency to the normal range.

[0027] The frequency - fluctuation characteristic indexes include: the maximum amplitude of the out - of - limit frequency, the time proportion of the out - of - limit frequency, the maximum duration of the out - of - limit frequency, and the number of frequency out - of - limits;

[0028] (1) The maximum amplitude of the out - of - limit frequency:

[0029] Equations (1) and (2) are the expressions for the maximum amplitude Δf up of the out - of - dead - zone upper - limit frequency and the maximum amplitude Δf down of the out - of - dead - zone lower - limit frequency respectively:

[0030] Δf up =max{f(t)-f up}(1);

[0031] Δf down =max{f down -f(t)} (2);

[0032] In Equations (1) - (2), f up is the out - of - dead - zone upper - limit frequency, f down is the out - of - dead - zone lower - limit frequency, and f(t) is the frequency of the power system at time t.

[0033] (2) The time proportion of the out - of - limit frequency:

[0034] Let T be the total measurement time, T up be the cumulative time when the frequency crosses the dead - zone upper - limit, and T down be the cumulative time when the frequency crosses the dead - zone lower - limit. Then the total time proportion R of the out - of - limit frequency is defined as:

[0035]

[0036] In Equation (3), R up is the time proportion of the out - of - dead - zone upper - limit frequency, and R down is the time proportion of the out - of - dead - zone lower - limit frequency.

[0037] T up and T down can be calculated by Equation (4):

[0038]

[0039] In Equation (4), I() is an indicator function that has a value of 1 when the condition inside the parentheses holds and a value of 0 otherwise. Therefore, the above integral represents the cumulative time during which the frequency crosses the upper and lower limits of the dead zone within the total measurement time.

[0040] (3) Maximum duration of the over-limit frequency:

[0041] Let ΔT up and ΔT down represent the maximum duration of the frequency crossing the upper limit of the dead zone and the maximum duration of the frequency crossing the lower limit of the dead zone, respectively, as shown in Equation (5).

[0042]

[0043] In Equation (5), k refers to the k-th event of the frequency crossing the dead zone; and represent the start and end time points of the k-th event of crossing the upper limit of the dead zone, respectively; and represent the start and end time points of the k-th event of crossing the lower limit of the dead zone, respectively.

[0044] (4) Number of frequency over-limit times:

[0045] Suppose there is a time series of frequency data {f1, f2, …, f n}, where f i represents the frequency at the i-th time point. Define the number of times the frequency crosses the upper limit of the dead zone as N up , and the number of times the frequency crosses the lower limit of the dead zone as N down . Equation (6) is the mathematical expression.

[0046]

[0047] If the value of N up or N down is large, it proves that the power system frequency is continuously crossing the upper and lower limits of the dead zone. At this time, the primary frequency regulation equipment needs to operate continuously, which means that the frequency regulation equipment should have the ability to maintain stable performance and long service life at a high operation frequency.

[0048] S2. Establish a mathematical model of the frequency fluctuation characteristic index and the frequency regulation capacity requirement. This mathematical model maps the frequency regulation requirements of the power system associated with the frequency fluctuation characteristic index.

[0049] The maximum amplitude of the over-limit frequency directly maps the maximum demand for frequency regulation power of the power system. The frequency regulation power demand of the power system is proportional to the amplitude of the over-limit frequency fluctuation, that is, the larger the fluctuation amplitude, the greater the required frequency regulation power. Equation (7) is the expression for the maximum demand of frequency regulation power.

[0050]

[0051] In Equation (7), ΔP re and ΔP in respectively represent the maximum downward power demand and the maximum upward power demand of the power system; K = ΣK j , which is the unit regulation power of the power system, and K j is the unit regulation power of the j-th unit with frequency regulation capability.

[0052] The time proportion of the out-of-limit frequency maps the power system's demand for frequency regulation power. When the time proportion of the out-of-limit frequency is relatively large, it means that the cumulative time for the frequency to cross the dead zone is relatively long. This requires that the power system not only has sufficient frequency regulation power but also provides long-term frequency regulation support, that is, has sufficient frequency regulation power. Use ΔE re to represent the total downward power demand of the power system, and ΔE in to represent the total upward power demand of the power system:

[0053]

[0054] In Equation (8), P re (t) and P in (t) respectively represent the changes in the upward power demand and the downward power demand of the power system over time.

[0055] The maximum continuous duration of the out-of-limit frequency directly maps the minimum continuous frequency regulation duration required by the power system and also represents the minimum time scale for the analysis of the power system's frequency regulation capability demand. Use ΔT re to represent the downward duration demand of the power system, and ΔT in to represent the upward duration demand of the power system:

[0056]

[0057] The number of frequency out-of-limit times directly maps the power system's demand for the number of operations of the primary frequency regulation equipment. When the frequency frequently crosses the upper and lower limits of the dead zone, the primary frequency regulation equipment continuously operates to maintain frequency stability. This requires that the power system not only has sufficient frequency regulation power and frequency regulation power but also that the frequency regulation equipment can withstand frequent start-up and stop operations. Use N re to represent the demand for the number of operations of the primary frequency regulation equipment when the power system performs downward frequency regulation, and N in to represent the demand for the number of operations of the primary frequency regulation equipment when the power system performs upward frequency regulation:

[0058]

[0059] Input the frequency data of the power system to be evaluated into the mathematical model obtained in S2; the frequency data of the power system to be evaluated includes a frequency sequence and a time sequence; as Figure 2As shown in the figure, the process of evaluating the daily frequency regulation capacity demand of the power system according to the mathematical model obtained in S2 includes the following steps:

[0060] S301. Input the measured frequency sequence and time sequence;

[0061] S302. Perform data preprocessing, and use a low-pass filter to filter out the high-frequency noise in the above input sequence;

[0062] S303. Determine the time scale for analysis and divide it into n time windows;

[0063] S304. Set and initialize the number of loops, i = 1;

[0064] S305. Find the maximum amplitude Δf of the frequency crossing the upper dead zone limit upi and the maximum amplitude Δf of the frequency crossing the lower dead zone limit downi , calculate the time ratio R of the frequency crossing the upper dead zone limit upi and the time ratio R of the frequency crossing the lower dead zone limit downi , determine the maximum duration ΔT of the frequency crossing the upper dead zone limit upi and the maximum duration ΔT of the frequency crossing the lower dead zone limit downi , count the number of times N that the frequency crosses the upper dead zone limit upi and the number of times that the frequency crosses the lower dead zone limit is N downi ;

[0065] S306. Calculate ΔP rei and ΔP ini according to Equation (7); calculate ΔE rei and ΔE ini according to Equation (8);

[0066] S307. Determine ΔT rei and ΔT ini； according to Equation (9), and determine N rei or N ini according to Equation (10);

[0067] S308. Obtain the vector describing the frequency fluctuation characteristics of the power system:

[0068] c i = [Δf upi , Δf dowmi , R upi , R downi , ΔT upi , ΔT downi , N upi , N downi ;

[0069] Obtain the vector describing the frequency regulation capacity demand of the power system:

[0070] d i = [ΔP rei , ΔP ini , ΔE rei , ΔE ini , ΔT rei , ΔT ini , N rei , N ini .

[0071] S309. Judge whether i is greater than or equal to n. If so, execute S310; if not, let i = i + 1 and jump to execute S305;

[0072] S310. Obtain the power system frequency fluctuation characteristic description matrix: C = [c1, c2, …, c i , …, c n T ;

[0073] Obtain the power system frequency regulation capacity demand description matrix: D = [d1, d2, …, d i , …, d n T ; End the loop.

[0074] The maximum amplitude of the out-of-limit frequency can intuitively reflect the severity of the power system frequency fluctuation. By analyzing the maximum amplitude of the out-of-limit frequency, the maximum unbalance of the active power in the power system can be determined, which helps the dispatching personnel to adjust the power system output in time and also provides direct guidance for the evaluation of the power system frequency regulation power demand; the time proportion of the out-of-limit frequency can directly reflect the power system's demand for frequency regulation time and also indirectly reflect the power system's demand for frequency regulation power; define the longest time that the power system frequency lasts when crossing the dead zone once as the maximum duration of the out-of-limit frequency, which can reveal the most severe situation of the frequency fluctuation and determine the minimum demand of the power system for the continuous frequency regulation duration; the number of frequency out-of-limit times can intuitively show the frequency of the power system crossing the dead zone. According to the above process, the frequency fluctuation characteristics can be obtained from the frequency data, so as to realize the evaluation of the daily frequency regulation capacity demand of the power system.

[0075] S3. Verify the effectiveness of the proposed power system frequency regulation capacity demand evaluation method: Select the actual regional power grid as the example power system, calculate the frequency fluctuation characteristic index and frequency regulation capacity demand of the power system based on the measured frequency data of the power system, and reveal the influence of the frequency regulation characteristics of different regulation resources on the frequency regulation capacity demand.

[0076] ​​Select a certain actual regional power grid as the example power system, obtain the measured frequency data of the power system continuously for one month with a sampling interval of 1 minute, and calculate the frequency fluctuation characteristic index and the frequency regulation capacity demand of the example power system in this month. The example results show that the proposed index system comprehensively depicts the frequency over-limit situation on the daily time scale. It can be found from the index that the frequency over-limit problem within a day is serious and the frequency regulation actions are very frequent, which will greatly accelerate the life consumption of the primary frequency regulation equipment. At the same time, considering the differences in the frequency regulation characteristics of different regulation resources, it is found that the demand for frequency regulation power of the frequency regulation resources with two-way regulation ability is significantly lower than that of the unidirectional regulation resources. The proposed method can provide guidance for the frequency regulation resource allocation of the power system.

[0077] Specifically, select a certain actual regional power grid as the example system. The maximum power load of this system is 60,000 MW, the maximum new energy penetration rate is 61.13%, the frequency dead zone is ±0.033 Hz, and the measured frequency data of the system continuously for one month are obtained with a sampling interval of 1 minute.

[0078] (1) Frequency fluctuation characteristics on the daily time scale

[0079] The load demand and new energy output of the system will experience significant changes within a day, showing daily change characteristics. Analyzing the frequency fluctuation characteristics on the daily time scale can provide support for daily dispatching plans and frequency forecasts, etc. Figure 3 Figure 11 is the fluctuation curve of the over-limit frequency drawn according to the measured frequency data of a certain day. It is not difficult to see that the fluctuation amplitude of the over-limit frequency within this day is relatively large, the curve is serrated, the frequency continuously crosses the dead zone, and the proportion of the over-limit frequency is relatively high.

[0080] From the calculation results of the frequency fluctuation characteristic index of the example system within this month, it can be seen that the Δf up is up to 0.049 Hz at most, and the Δf down is up to 0.046 Hz at most. The relatively large fluctuation amplitude indicates that the power imbalance of the system is relatively large. The proportion of the frequency crossing the upper limit of the dead zone can reach 45.56% at most, and the proportion of the frequency crossing the lower limit of the dead zone is up to 28.96% at most. And the total proportion of the frequency crossing the dead zone is as high as 71.25% at most and reaches 34.31% at least. The high proportion of the over-limit frequency reveals that the frequency over-limit phenomenon of the system is extremely serious.

[0081] It can also be found that the ΔT up is in the range of 15 min to 40 min, and the ΔT downIn the range of 6 minutes to 35 minutes, the longer the maximum duration of the out-of-limit frequency, the higher the minimum demand of the system for the frequency modulation duration. The total number of frequency out-of-limit times is at least 511 times and at most 671 times, indicating that the frequency crosses the dead zone every 2 to 3 minutes, meaning that the primary frequency modulation equipment has to operate every 2 to 3 minutes, and the frequency modulation operation is very frequent, which will greatly accelerate the life consumption of the primary frequency modulation equipment.

[0082] The proposed index system comprehensively depicts the frequency out-of-limit situation on a daily time scale. It can be found from the index that the frequency out-of-limit problem within a day is serious, so the evaluation of the system's daily frequency modulation ability demand is very important.

[0083] (2) Frequency modulation ability demand on a daily time scale

[0084] From the calculation results of the frequency modulation ability demand index of the example system within this month, it can be seen that the maximum of ΔP re in this month is 118.55 MW and the minimum is 59.96 MW; the maximum of ΔP in is 111.23 MW and the minimum is 30.66 MW. The distribution of ΔP re and ΔP in is shown as Figure 4 . It can be seen that on a daily time scale, the system has a high demand for frequency modulation power. If only considering the system's frequency modulation ability demand and not considering the type and characteristics of frequency modulation resources, the distribution of ΔE re and ΔE in is shown as Figure 5 . The maximum of ΔE re in this month is 236.03 MWh and the minimum is 62.15 MWh; the maximum of ΔE in is 127.39 MWh and the minimum is 19.89 MWh; the maximum of the total demand for frequency modulation electricity is 363.42 MWh and the minimum is 93.69 MWh. It can be seen that on a daily time scale, the system also has a high demand for frequency modulation electricity.

[0085] If considering the type and characteristics of frequency modulation resources, taking energy storage as an example, as a new type of frequency modulation resource with two-way regulation ability, it can transfer the system energy. When participating in system frequency modulation, the energy storage switches repeatedly between the charge and discharge states, and there is a certain cancellation between the charge and discharge electricity, resulting in a reduction in the demand for frequency modulation electricity. The frequency modulation electricity demand calculated after considering the two-way regulation characteristics of energy storage is defined as the net demand for frequency modulation electricity of the system. Through statistics, it is obtained that the net demand for the down-regulation electricity and up-regulation electricity of the system is compared with ΔE re and ΔE inAll of them have decreased significantly. In fact, on 9 days, the net demand for downward regulation power was 0, indicating that within these 9 days, the system's daily downward regulation power was sufficient to offset the demand for upward regulation power. For the distribution of the net demand for total frequency regulation power, please refer to Figure 6 , from which it can be seen that the highest value is 146.78 MWh, the lowest value is 18.43 MWh, and it is mainly distributed in the range of 50 MWh to 100 MWh.

[0086] Through statistics, it can also be obtained that the system requires the primary frequency regulation equipment to continuously participate in frequency regulation for no less than 40 minutes, and it needs to maintain stable performance and a long service life under nearly 700 high-frequency operations within a day. The above data together reveal that on the daily time scale, in order to suppress frequency fluctuations and reduce the number of out-of-limit occurrences, the system faces high demands in terms of frequency regulation power, frequency regulation power quantity, frequency regulation duration, and the number of operations of the primary frequency regulation equipment.

[0087] Through the above analysis, it can be known that a new method for evaluating the frequency regulation capacity demand of a power system considering frequency fluctuation characteristics according to the present invention constructs a frequency fluctuation characteristic index system on a daily time scale based on the measured daily frequency fluctuation curve, and reveals the frequency fluctuation characteristics from multiple perspectives such as the maximum amplitude, time proportion, maximum duration, and number of out-of-limit occurrences of the out-of-limit frequency; and establishes a mathematical model between the frequency fluctuation index and the frequency regulation capacity demand, realizing the quantitative evaluation of the system's daily frequency regulation capacity demand only from the frequency fluctuation curve; finally, based on the measured data and waveforms of the frequency, it reveals the influence of the frequency regulation characteristics of different regulation resources on the frequency regulation capacity demand, which can provide guidance for the configuration of frequency regulation resources.

[0088] The above embodiments can be implemented in whole or in part by software, hardware (such as circuits), firmware, or any combination thereof. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, the processes or functions described in the embodiments of the present invention are generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (such as infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that contains one or more collections of available media. The available media can be magnetic media (such as floppy disks, hard disks, magnetic tapes), optical media (such as DVDs), or semiconductor media. The semiconductor media can be a solid-state drive.

[0089] It should be understood that the term "and / or" in this document is merely a description of the association relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Here, A and B can be singular or plural. Additionally, the character " / " in this document generally represents an "or" relationship between the associated objects before and after, but it may also represent an "and / or" relationship, which can be specifically understood by referring to the context before and after.

[0090] In the present invention, "at least one" means one or more, and "a plurality" means two or more. "At least one of the following" or similar expressions refer 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 represent: a, b, c, a - b, a - c, b - c, or a - b - c, where a, b, and c can be single or multiple.

[0091] It should be understood that in various embodiments of the present invention, the magnitudes of the sequence numbers of the above processes do not mean the order of execution is prior or subsequent. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0092] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0093] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the above-described devices, apparatuses, and units can refer to the corresponding processes in the foregoing method embodiments, and will not be elaborated herein.

[0094] In several embodiments provided by the present invention, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces. The indirect couplings or communication connections of the devices or units can be in electrical, mechanical, or other forms.

[0095] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place, or can be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0096] In addition, the functional units in each embodiment of the present invention can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit.

[0097] When the above-mentioned functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The foregoing storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories (ROM), random access memories (RAM), magnetic disks, or optical discs.

[0098] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for evaluating the frequency regulation capacity demand of a power system taking into account frequency fluctuation characteristics, characterized in that: The method includes: S1. Construct the frequency fluctuation characteristic index of the power system, use the set frequency dead zone as the boundary, extract and draw the frequency fluctuation curve of the over-limit part; based on the fluctuation curve of the over-limit frequency, propose the frequency fluctuation characteristic index to comprehensively characterize the frequency fluctuation characteristics on the daily time scale; S2. Establishing a mathematical model of frequency fluctuation characteristic index and frequency regulation capacity demand, wherein the mathematical model uses the frequency fluctuation characteristic index to map the associated power system frequency regulation demand; S3. Verify the effectiveness of the proposed method for evaluating the frequency regulation capacity demand of the power system: select an actual regional power grid as the example power system, calculate the frequency fluctuation characteristic indicators and frequency regulation capacity demand of the power system based on the measured frequency data of the power system, and reveal the impact of the frequency regulation characteristics of different regulation resources on the frequency regulation capacity demand.

2. A method for evaluating the frequency regulation capability demand of a power system taking into account frequency fluctuation characteristics according to claim 1, characterized in that: The frequency fluctuation characteristic indicators include: the amplitude of the over-limit frequency, the time proportion of the over-limit frequency, the duration of the over-limit frequency and the number of frequency over-limits; the power system frequency regulation demand includes the power system's demand for frequency regulation electricity, the power system's demand for frequency regulation power, the power system's required continuous frequency regulation time and the power system's demand for the number of primary frequency regulation equipment operations; the maximum amplitude of the over-limit frequency directly maps the power system's maximum demand for frequency regulation power; the time proportion of the over-limit frequency maps the power system's demand for frequency regulation electricity; the maximum duration of the over-limit frequency directly maps the minimum continuous frequency regulation time required by the power system; the number of frequency over-limits directly maps the power system's demand for the number of primary frequency regulation equipment operations.

3. A method for evaluating the frequency regulation capability demand of a power system taking into account frequency fluctuation characteristics according to claim 2, characterized in that: Frequency fluctuation characteristic indicators: (1) The maximum amplitude of the over-limit frequency is shown in equations (1) and (2): Δf up =max{f(t)-f up } (1); Δf down =max{f down -f(t)} (2); Formula (1) and Formula (2) are the maximum amplitude Δf of the upper limit frequency of the dead zone respectively. up and the maximum amplitude of the lower limit frequency of the dead zone Δf down In formula (1)-(2), f up is the upper frequency of the dead zone, f down is the lower limit frequency of the dead zone, f(t) is the frequency of the power system at time t; (2) Time proportion of over-limit frequency: Let T be the total measurement time, T up T is the cumulative time that the frequency exceeds the upper limit of the dead zone. down is the cumulative time that the frequency exceeds the lower limit of the dead zone, and the total time proportion R of the frequency exceeding the limit is defined as: In formula (3), R up R is the time proportion of exceeding the upper limit frequency of the dead zone, down The time proportion of the frequency exceeding the lower limit of the dead zone; T up and T down It can be calculated by formula (4): In formula (4), I() is an indicator function. When the condition in the brackets is met, its value is 1, otherwise its value is 0. Therefore, the above integral represents the cumulative time that the frequency crosses the upper and lower limits of the dead zone within the total measurement time; (3) Maximum duration of frequency exceeding the limit: The maximum duration of the power system frequency crossing the dead zone is defined as the maximum duration of the frequency crossing, and ΔT is used to represent the maximum duration of the frequency crossing. up and ΔT down It represents the maximum duration of exceeding the upper limit frequency of the dead zone and the maximum duration of exceeding the lower limit frequency of the dead zone, as shown in formula (5): In formula (5), k refers to the kth frequency crossing the dead zone event; and Respectively represent the start and end time points of the kth dead zone upper limit crossing event; and Respectively represent the start and end time points of the kth dead zone lower limit crossing event; (4) Frequency limit violations: Assume there is a time series frequency data {f1, f2, ..., f n }, f i Represents the frequency at the i-th time point, and defines the number of times the frequency crosses the dead zone upper limit as N up , the frequency exceeds the lower limit of the dead zone for N times down , N up、 N down The mathematical formula is shown in formula (6):

4. A method for evaluating the frequency regulation capability demand of a power system taking into account frequency fluctuation characteristics according to claim 3, characterized in that: The maximum amplitude of the over-limit frequency directly reflects the maximum demand of the power system for frequency modulation power: the frequency modulation power demand of the power system is proportional to the amplitude of the over-limit frequency fluctuation; Formula (7) is the expression of the maximum demand for frequency modulation power: In formula (6), ΔP re and ΔP in They represent the maximum downward power demand and the maximum upward power demand of the power system respectively; K = ΣK j , is the unit regulation power of the power system, K j The unit regulation power of the jth unit with frequency regulation capability; The time proportion of over-limit frequency maps the power system's demand for frequency regulation: ΔEre is used to represent the total demand for down-regulation power in the power system, ΔE in Indicates the total demand for increased power in the power system: Where P re (t) and P in (t) represent the changes of upward power demand and downward power demand of the power system over time. The maximum duration of the over-limit frequency directly maps to the minimum continuous frequency regulation duration required by the power system, expressed as ΔT re Indicates the down-regulation time requirement of the power system, ΔT in Indicates the time required for the power system to increase: The frequency over-limit times directly reflects the power system's demand for the number of times the primary frequency regulation equipment operates: N re Indicates the number of times the frequency regulation equipment needs to operate when the power system is modulating downward, N in Indicates the number of times the frequency regulation equipment needs to operate when the power system is adjusted upward:

5. The method for evaluating the power system frequency regulation capability requirement taking into account the frequency fluctuation characteristics according to claim 1, characterized in that: A real regional power grid is selected as the example power system. The measured frequency data of the example power system for one month is obtained with a sampling interval of 1 minute. The frequency fluctuation characteristic indicators and frequency regulation capacity requirements of the example power system in that month are calculated.

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