A fast and practical online calculation method for the moment of inertia considering the power difference ratio

Abstract

The present invention belongs to the technical field of power system analysis, and in particular, relates to a fast and practical online calculation method for the moment of inertia that takes into account the power difference ratio. The present invention includes using the simulation cutting machine method and the unit accumulation method to preliminarily calculate the moment of inertia of different operating modes of the power grid in the same region; using the simulation cutting machine method and the unit accumulation method to calculate the moment of inertia values ​​of the same power grid, and performing comparative analysis; determining a fast and practical moment of inertia calculation method suitable for a certain local power grid through the functional relationship between the two algorithms. The present invention has the characteristics of fast calculation speed, high calculation accuracy, and strong practicality. The present invention can quickly calculate the moment of inertia of the system, eliminating the complex calculation process of simulation calculation, and saving a lot of time. The algorithm proposed in the present invention draws on and gives full play to the advantages of the two existing algorithms, can accurately calculate the moment of inertia of a power grid in a certain region, and is a quantitative analysis, summary, and display of the actual operation mode of the power grid.

Description

Technical Field

[0001] The invention belongs to the technical field of power system analysis, and in particular relates to a fast and practical online calculation method for the moment of inertia taking into account the power difference ratio. Background Art

[0002] my country's economy is shifting from high-speed development to high-quality development. In the field of energy, as the revolution in energy production and consumption continues to advance, clean production and electrification on the consumption side have become important trends and characteristics of my country's current energy system. In 2019, State Grid Corporation of my country proposed a dual 50% goal of 50% clean energy rate and 50% terminal electrification rate by 2050, which will make the dynamic characteristics of the world's largest AC / DC interconnected power grid in my country more complex and increase the risk of safe and stable operation. Objectively, higher requirements are put forward for the state of the power system under the new situation, especially more timely moment of inertia perception methods, more accurate moment of inertia calculation technology and more reliable analysis and evaluation methods.

[0003] At present, there are two commonly used rotational inertia algorithms in the world, namely the "simulation cutting method" and the "unit accumulation method".

[0004] The simulation cutting method calculates the frequency drop rate by artificially setting the power shortage in the simulation program. It requires simulation calculation of the power grid. The calculation result can truly reflect the system's rotational inertia, but the calculation process is cumbersome and time-consuming, but the result is highly accurate and is not suitable for online rapid and practical calculation of rotational inertia.

[0005] The unit accumulation method is to simply accumulate the rotational inertia of the grid-connected units. The calculation result can be quickly obtained by simply accumulating the rotational inertia of the given online units. The calculation process is simple and fast, but the error is large and the calculation accuracy is poor. It cannot reflect the actual system rotational inertia result and is not suitable for accurate offline calculation.

[0006] The following is a brief description of the "simulation cutting method" and the "unit accumulation method":

[0007] The simulation cutting method calculates the system moment of inertia by considering the worst case of a local power grid, cutting off a generator with the largest moment of inertia that has been connected to the grid in the area, and calculating by finding the maximum rate of change of frequency. If the initial frequency of the system is 50Hz, the expression of the system moment of inertia obtained by the simulation cutting method is:

[0008]

[0009] In the formula, H 切机 is the system moment of inertia calculated by the machine cutting method; df / dt is the average value of the frequency change rate; △P is the overall system fault loss power, and H′ is the moment of inertia corresponding to a single generator that has been disconnected from the grid.

[0010] The unit accumulation method is a method that uses the known moment of inertia of a single generator and usually needs to be calculated based on the time constant provided by the manufacturer, and the result of the accumulated moment of inertia of all grid-connected units is used as the moment of inertia of the system. The online single generator moment of inertia has a nominal value H1 and an inertia time constant T j1 and the rated capacity of a single generator S N1 The relationship is as follows:

[0011]

[0012] In the above formula, ω is the angular velocity of the generator, unit is rad / s; f is the frequency of the generator, unit is Hz; 2πf is twice the pi π multiplied by the frequency f, unit is Hz.

[0013] If there are N online generators, the total moment of inertia of the system obtained by the accumulation method is H 累加 for

[0014] H 累加 =H1+H2+H3+...+H N (3)

[0015] Among them, H1, H2, H3...H N is the rotational inertia of each of the N online units.

[0016] If a system failure occurs and causes power loss, the relationship between the power shortfall measured at the N online units and the total power shortfall measured at the N online units is as follows:

[0017]

[0018] Among them, the limit value of i is N, △P i is the power shortage measured at the end of the ith online unit, and △P′ is the total power shortage measured at the ends of N online units.

[0019] If the data calculated by the simulation cutting method comes from the offline research state, the result is accurate but cannot reflect the real-time state of the power grid; if the data calculated by the unit accumulation method comes from the online real-time state, the result is highly timely but less accurate. Therefore, no algorithm can meet the requirements of fast and accurate moment of inertia calculation and evaluation. Summary of the invention

[0020] In view of the shortcomings of the above-mentioned prior art, the present invention provides a fast and practical online calculation method for the moment of inertia taking into account the power difference ratio, which aims to achieve the invention purpose of meeting the requirements of fast and accurate moment of inertia calculation and evaluation.

[0021] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0022] A fast and practical online calculation method for the moment of inertia considering the power difference ratio includes a simulation machine cutting method and a unit accumulation method, and the system moment of inertia is calculated by using the simulation machine cutting method and the unit accumulation method; and the following steps are also included:

[0023] Step 1. Use the simulated machine cutting method and the unit accumulation method to preliminarily calculate the rotation inertia of different operation modes of the same regional power grid;

[0024] Step 2. Calculate the moment of inertia value of the same power grid using the simulated machine cutting method and the unit accumulation method, and conduct comparative analysis;

[0025] Step 3. Determine a fast and practical method for calculating the moment of inertia suitable for the power grid through the proportional relationship between the two algorithms.

[0026] Furthermore, the simulated machine cutting method and the unit accumulation method are used in step 1 to preliminarily calculate the rotation inertia of different operation modes of the power grid in the same area, including:

[0027] In the simulation program, a single generator with the largest rotational inertia of the entire grid is simulated to be removed. After simulation, the average value of the frequency change rate in the interval of 0-3 seconds is obtained. The average value of the frequency change rate df / dt, the overall fault power loss △P of the system, and the rotational inertia H' corresponding to the single generator that has been disconnected from the grid are substituted into formula (1) to automatically calculate H 切机 value;

[0028] At the same time, the inertia time constant T given by the manufacturer is j1 and the rated capacity of a single generator S N1 Substitute the value into formula (2) to calculate the moment of inertia of a single generator, and use the unit accumulation method (3) to calculate the sum of the moments of inertia of all grid-connected generators H 累加 .

[0029] Furthermore, in step 2, the values ​​of the moment of inertia calculated by the simulation cutting method and the unit accumulation method for the same power grid are compared and analyzed, including:

[0030] After analyzing the different operation modes of regional power grids H 切机 With H 累加 A large number of calculations found that H 切机 With H 累加 The results are proportional to each other, and the proportional factor is the ratio of the overall system fault loss power △P to the total power shortage △P′ measured at the N online units. 切机 With H 累加 The proportional relationship equation between the two is as follows:

[0031]

[0032] Where △P is the power loss of the whole system due to fault, △P′ is the total power shortage measured at the end of N online units, and H 切机 is the system moment of inertia calculated by the cutting machine method, H 累加 It is the system rotational inertia calculated by the unit accumulation method.

[0033] Furthermore, the method of determining a fast and practical moment of inertia calculation method applicable to the power grid by using the proportional relationship between the two algorithms in step 3 includes:

[0034] First, the moment of inertia of multiple operating modes is calculated using two methods as a data sample library, and then the multivariate linear regression function relationship between the ratio of the two algorithm results in the data sample library and the proportion of new energy is found; the sample library is obtained by calculating the data of N operating modes, and the proportional relationship equation (5) is obtained;

[0035] After obtaining the overall system fault power loss △P and the total power shortage △P′ measured at the N online units, the cumulative method is used to quickly calculate the moment of inertia H of a given operating mode. 累加 Then substitute the ratio of the total system fault loss power △P in the actual operation mode and the total power shortage △P′ measured at the N online units into the proportional relationship equation (5), and use H 累加 Reverse H 切机 ; Using the inherent relationship characteristics of the existing regional power grid cutting method and accumulation method, H is quickly calculated 切机 result.

[0036] Furthermore, the step 1 described in which the simulation cutting method and the unit accumulation method are used to preliminarily calculate the moment of inertia of different operation modes of the power grid in the same region respectively refers to using the simulation cutting method and the unit accumulation method to calculate the moment of inertia of the same power grid respectively; using the simulation cutting method and the unit accumulation method to preliminarily calculate the moment of inertia of 11 different operation modes respectively; simulating the removal of a single generator with a maximum moment of inertia of 1000MW, importing the system frequency change curve data obtained by simulating the power system analysis and comprehensive program PSASP into the Matlab program, and obtaining the average value of the frequency change rate in the range of 0-3 seconds after simulation, and substituting the average value of the frequency change rate df / dt, the system overall fault loss power △P, and the moment of inertia H′ corresponding to the single generator that has been disconnected from the grid into formula (1) to automatically calculate H 切机 value; at the same time, the inertia time constant T given by the manufacturer is j1 and the rated capacity of a single generator S N1 Substitute the value into formula (2) to calculate the moment of inertia of a single generator, and use the unit accumulation method (3) to calculate the sum of the moments of inertia of all grid-connected generators H 累加 .

[0037] Furthermore, in step 2, the moment of inertia values ​​of the same power grid are calculated by using the simulated machine cutting method and the unit accumulation method, and a comparative analysis is performed; 切机 , H 累加 , △P′ / △P, and preliminarily calculate H in 11 different operation modes. 累加 / H 切机 The results show: H 累加 / H 切机 The ratio △P′ / △P has a regularity, △P′ / △P is greater than 1, so △P / △P′ in formula (5) is less than 1; Based on the existing results, it is preliminarily inferred that: H 切机 With H 累加 The mathematical relationship between the results of the two algorithms has a proportional characteristic. After fitting, the power grid H is obtained. 切机 With H 累加 The proportional relationship equation between:

[0038] H 切机 =H 累加 ×0.7948 (6)

[0039] In the above formula, H 切机 is the system moment of inertia calculated by the cutting machine method, H 累加 It is the system rotational inertia calculated by the unit accumulation method.

[0040] Furthermore, the method for calculating the moment of inertia of the power grid using the proportional relationship between the two algorithms in step 3 includes: 累加 Substitute the data into formula (6) and get H 切机 ; The accuracy and practicality of proportional relationship equations (5) and (6) are proved. (5) and (6) can be used for rapid and practical online evaluation of power grid rotation inertia.

[0041] Furthermore, the regression equations (5) and (6) are used to perform a rapid and practical online evaluation of the power grid moment of inertia, including: the measured H 累加 Substitute the data into formula (6) and get H 切机 It is 325810.2MW.s, which proves the accuracy and practicality of regression equations (5) and (6). Equations (5) and (6) can be used to conduct rapid and practical online evaluation of the moment of inertia of the Northeast Power Grid.

[0042] A computer storage medium stores a computer program, which, when executed by a processor, implements the steps of the method for rapidly and practically calculating the moment of inertia in consideration of the power difference ratio online.

[0043] The present invention has the following beneficial effects and advantages:

[0044] (1) Fast calculation speed. After obtaining the moment of inertia value through simple unit accumulation method, the system moment of inertia can be quickly calculated by using the existing functional relationship between the accumulation method and simulation cutting method for a certain area of ​​power grid units, eliminating the complex calculation process of simulation calculation and saving a lot of time.

[0045] (2) High calculation accuracy. The proposed algorithm draws on and gives full play to the advantages of the two existing algorithms and can accurately calculate the moment of inertia of a regional power grid.

[0046] (3) Strong practicability. Different from previous theoretical algorithms, the proposed algorithm calculates the moment of inertia based on the actual grid operation parameters. It is a quantitative analysis, summary, and display of the actual grid operation mode, and has strong practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0048] Figure 1 It is a flow chart of a rapid and practical online calculation method of the moment of inertia taking into account the power difference ratio of the present invention. DETAILED DESCRIPTION

[0049] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0050] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0051] Refer to the following Figure 1 The technical solutions of some embodiments of the present invention are described.

[0052] Example 1

[0053] The present invention is a fast and practical online calculation method for the moment of inertia taking into account the power difference ratio. After combining and improving the simulation cutting method and the unit accumulation method, the present invention finds the functional relationship between the results of the two methods, and thus proposes the present invention.

[0054] The grid rotational inertia described in the present invention is a measure of the inertia of a rigid body when it rotates around an axis. The grid rotational inertia is the sum of the rotational inertias of all online generator sets and loads in the power system under a specific operating mode.

[0055] like Figure 1 As shown, Figure 1 The present invention is a flowchart of a fast and practical online calculation method of the moment of inertia considering the power difference ratio. The present invention includes a simulation cutting method and a unit accumulation method, and uses the classical algorithm of the moment of inertia to calculate the moment of inertia of the system by simulating the cutting method and the unit accumulation method. The present invention specifically includes the following steps:

[0056] Step 1. Use the simulated machine cutting method and the unit accumulation method to preliminarily calculate the rotational inertia of different operating modes of the same regional power grid.

[0057] In the simulation program, the single generator with the largest rotational inertia of the entire grid is simulated to be removed. After the simulation, the average value of the frequency change rate df / dt in the interval of 0-3 seconds is obtained. The average value of the frequency change rate df / dt, the overall fault power loss △P of the system, and the rotational inertia H' corresponding to the single generator that has been disconnected from the grid are substituted into formula (1) to automatically calculate H 切机 value.

[0058] At the same time, the inertia time constant T given by the manufacturer is j1 and the rated capacity of a single generator S N1 Substitute the value into formula (2) to calculate the moment of inertia of a single generator, and use the unit accumulation method (3) to calculate the sum of the moments of inertia of all grid-connected generators H 累加 .

[0059] Step 2. For the same power grid, use the simulated machine cutting method and the unit accumulation method to calculate the moment of inertia values, and perform a comparative analysis.

[0060] Generally speaking, after studying different operation modes of a certain area power grid, 切机 With H 累加 A large number of calculations can be found that H 切机 With H 累加 The results are proportional, and the proportional factor is the ratio of the overall system fault power loss △P to the total power shortage △P′ measured at the N online units. 切机 With H 累加 The proportional relationship equation between the two is as follows:

[0061]

[0062] Where △P is the power loss due to the overall system failure, and △P′ is the total power shortage measured at the end of N online units.

[0063] Step 3. Determine a fast and practical method for calculating the moment of inertia suitable for the power grid through the proportional relationship between the two algorithms.

[0064] Based on the above inference, we can first use two methods to calculate the moment of inertia of multiple operating modes as a data sample library, and then find the multivariate linear regression function relationship between the ratio of the two algorithm results in the data sample library and the proportion of new energy. Using N operating modes to calculate the data sample library, we can get the proportional relationship equation (5).

[0065] After obtaining the overall system fault power loss △P and the total power shortage △P′ measured at the N online units, first use the accumulation method to quickly calculate the moment of inertia H of the given operating mode. 累加 Then substitute the ratio of the total system fault loss power △P in the actual operation mode and the total power shortage △P′ measured at the N online units into the proportional relationship (5) and use H 累加 Reverse H 切机 This is done by using the inherent relationship between the existing regional power grid cutting method and the accumulation method to quickly calculate H 切机 result.

[0066] In the actual operation of the power grid, this method can quickly and accurately perform online calculation and evaluation of the moment of inertia, eliminating the tedious steps of simulation calculation while ensuring accuracy.

[0067] Example 2

[0068] The present invention further provides an embodiment, a fast and practical online calculation method for the moment of inertia taking into account the power difference ratio, and the moment of inertia calculation method of the present invention is verified in actual power grid.

[0069] A fast and practical online calculation method for the moment of inertia taking into account the power difference ratio is improved on the basis of the simulation of the machine cutting method and the unit accumulation method through the moment of inertia algorithm.

[0070] The present invention specifically comprises the following steps:

[0071] Step (1) calculates the rotational inertia of the same power grid using the simulated machine cutting method and the unit accumulation method respectively.

[0072] Taking the Northeast Power Grid as an example, the rotational inertia of 11 different operating modes was preliminarily calculated using the simulation cutting method and the unit accumulation method. The simulation was performed to cut off a single generator with the maximum rotational inertia of 1000MW. The system frequency change curve data obtained by simulating the power system analysis comprehensive program PSASP (Power System Analysis Software Package) was imported into the Matlab program. After the simulation, the average value df / dt of the frequency change rate in the range of 0-3 seconds was obtained. The average value df / dt of the frequency change rate, the overall fault loss power △P of the system, and the rotational inertia H' corresponding to the single generator that has been disconnected from the grid were substituted into formula (1) to automatically calculate H 切机At the same time, the inertia time constant T given by the manufacturer is j1 and the rated capacity of a single generator S N1 Substitute the value into formula (2) to calculate the moment of inertia of a single generator, and use the unit accumulation method (3) to calculate the sum of the moments of inertia of all grid-connected generators H 累加 .

[0073] Step (2) uses the simulated machine cutting method and the unit accumulation method to calculate the moment of inertia values ​​of the same power grid, and conducts comparative analysis.

[0074] H 切机 , H 累加 The data sample library composed of , △P′ / △P, etc. is shown in Table 1.

[0075] Table 111 Sample library of operation mode data

[0076]

[0077]

[0078] As can be seen from Table 1, the preliminary calculation results of 11 different operation modes show that the ratio of accumulation / cutting results △P′ / △P has a certain regularity, and △P′ / △P is generally greater than 1, so △P / △P′ in formula (5) should be less than 1. Although the sample is small, it can be preliminarily inferred from the existing results that: H 切机 With H 累加 The mathematical relationship between the results of the two algorithms has a proportional characteristic. After fitting, the Northeast Power Grid H 切机 With H 累加 The proportional relationship equation between the results is:

[0079] H 切机 =H 累加 ×0.7948 (6).

[0080] Step (3) The measured H 累加 Substitute the data into formula (6) and get H 切机 The accuracy and practicality of the proportional relationship equations (5) and (6) are proved, so the proportional relationship equations (5) and (6) can be used for rapid and practical online evaluation of the power grid rotation inertia.

[0081] The specific operations are as follows:

[0082] The measured H in a 1000MW large single generator tripping event in Northeast China Power Grid in 2019 累加 Substitute the data into formula (6) and get H 切机It is 325810.2MW.s. The accuracy and practicality of the proportional relationship equations (5) and (6) are proved, so equations (5) and (6) can be used for rapid and practical online evaluation of the rotational inertia of the Northeast Power Grid.

[0083] Among them, the 2019 tripping event of a 1000MW large single generator in the Northeast Power Grid refers to the tripping of a 1000MW large single generator in the Northeast Power Grid on a certain day in November 2019, causing the frequency of the Liaoning Power Grid to drop from 50.05Hz to 49.90Hz, a decrease of 0.15Hz. The fault occurred during the early peak period of the Liaoning Power Grid. The total power generation capacity of the Northeast Power Grid was 62.21 million kilowatts, and the unified load was 48.32 million kilowatts. At the time of the fault, the total thermal power generation of the Northeast Power Grid was 44.17 million kilowatts, accounting for 69%, the new energy power generation was 13.6 million kilowatts, accounting for 21%, and the nuclear power generation was 4.44 million kilowatts, accounting for 9.2%.

[0084] Example 3

[0085] Based on the same inventive concept, an embodiment of the present invention further provides a computer storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method for quickly and practically calculating the moment of inertia taking into account the power difference ratio described in Examples 1 and 2 are implemented.

[0086] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0087] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0088] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0089] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A fast and practical online calculation method for the moment of inertia considering the power difference ratio, which is characterized by: The following steps are involved: Step 1. Use the simulated machine cutting method and the unit accumulation method to preliminarily calculate the rotation inertia of different operation modes of the same regional power grid; Step 2. Calculate the moment of inertia of the same power grid using the simulated machine cutting method and the unit accumulation method, and conduct comparative analysis, including: 切机 With H 累加 A large number of calculations have found that H 切机 With H 累加 The results are proportional to each other, and the proportional factor is the ratio of the overall system fault loss power △P to the total power shortage △P′ measured at the N online units. 切机 With H 累加 The proportional relationship equation between the two is as follows: Among them, △P is the power loss of the whole system due to fault, △P′ is the total power shortage measured at the end of N online units, and H 切机 is the system moment of inertia calculated by the cutting machine method, H 累加 is the system moment of inertia calculated by the unit accumulation method; Step 3. Determine a fast and practical method for calculating the moment of inertia applicable to the power grid through the proportional relationship between the two algorithms, including: first, using the two methods to calculate the moment of inertia of multiple operating modes as a data sample library, then finding the ratio of the results of the two algorithms in the data sample library to obtain the proportional relationship equation (5); after obtaining the overall system fault loss power △P and the total power shortage △P′ measured at the N online units, use the accumulation method to quickly calculate the moment of inertia H of the given operating mode 累加 Then substitute the ratio of the total system fault loss power △P in the actual operation mode and the total power shortage △P′ measured at the N online units into the proportional relationship equation (5), and use H 累加 Reverse H 切机 ; Using the inherent relationship characteristics of the existing regional power grid cutting method and accumulation method, H is quickly calculated 切机 result.

2. The method for rapid and practical online calculation of the moment of inertia taking into account the power difference ratio according to claim 1 is characterized by: Step 1 uses the simulated machine cutting method and the unit accumulation method to preliminarily calculate the rotation inertia of different operation modes of the same regional power grid, including: In the simulation program, the single generator with the largest rotational inertia of the entire grid is simulated to be removed. After the simulation, the average value of the frequency change rate in the interval of 0-3 seconds is obtained. The average value of the frequency change rate df / dt, the overall fault power loss of the system △P, and the rotational inertia H′ corresponding to the single generator that has been disconnected from the grid are substituted into formula (1) to automatically calculate H 切机 value; In the formula, H 切机 is the system moment of inertia calculated by the machine cutting method; df / dt is the average value of the frequency change rate; △P is the overall system fault loss power, and H′ is the moment of inertia corresponding to the single generator that has been disconnected from the grid; At the same time, the inertia time constant T given by the manufacturer is j1 and the rated capacity of a single generator S N1 Substitute the value into formula (2) to calculate the moment of inertia of a single generator: In the above formula, ω is the angular velocity of the generator, in rad / s; f is the frequency of the generator, in Hz; 2πf is twice the circumference of π multiplied by the frequency f, in Hz; The sum of the moments of inertia of all grid-connected generators H is obtained by the unit accumulation method (3): 累加 : H 累加 =H1+H2+H3+...+H N (3) Among them, H1, H2, H3...H N is the rotational inertia of each of the N online units.

3. The method for rapid and practical online calculation of the moment of inertia taking into account the power difference ratio according to claim 2 is characterized by: The step 1 described in that the simulation cutting machine method and the unit accumulation method are used to preliminarily calculate the moment of inertia of different operation modes of the power grid in the same region, refers to using the simulation cutting machine method and the unit accumulation method to calculate the moment of inertia of the same power grid respectively; using the simulation cutting machine method and the unit accumulation method to preliminarily calculate the moment of inertia of 11 different operation modes respectively; simulating the removal of a single generator with a maximum moment of inertia of 1000MW, importing the system frequency change curve data obtained by simulating the power system analysis and comprehensive program PSASP into the Matlab program, and obtaining the average value df / dt of the frequency change rate in the range of 0-3 seconds after simulation, and substituting the average value df / dt of the frequency change rate, the overall fault loss power △P of the system, and the moment of inertia H' corresponding to the single generator that has been disconnected from the grid into formula (1), and automatically calculating H 切机 value; at the same time, the inertia time constant T given by the manufacturer is j1 and the rated capacity of a single generator S N1 Substitute the value into formula (2) to calculate the moment of inertia of a single generator, and use the unit accumulation method (3) to calculate the sum of the moments of inertia of all grid-connected generators H 累加 .

4. The method for rapid and practical online calculation of the moment of inertia taking into account the power difference ratio according to claim 3 is characterized by: Step 2: For the same power grid, the simulation cutting method and the unit accumulation method are used to calculate the moment of inertia value, and a comparative analysis is performed, specifically including using H 切机 , H 累加 , △P′ / △P, and preliminarily calculate H in 11 different operation modes. 累加 / H 切机 The results show: H 累加 / H 切机 The ratio △P′ / △P has a regularity, △P′ / △P is greater than 1, so △P / △P′ in formula (5) is less than 1; Based on the existing results, it is preliminarily inferred that: H 切机 With H 累加 The mathematical relationship between the results of the two algorithms has a proportional characteristic. After fitting, the power grid H is obtained. 切机 With H 累加 The proportional relationship equation between them is: H 切机 =H 累加 ×0.7948 (6) In the above formula, H 切机 is the system moment of inertia calculated by the cutting machine method, H 累加 is the system moment of inertia calculated by the unit accumulation method; Step 3 determines a fast and practical method for calculating the moment of inertia suitable for the power grid through the proportional relationship between the two algorithms, including: 累加 Substitute the data into formula (6) and get H 切机 ; The accuracy and practicality of the proportional relationship equations (5) and (6) are proved, so the proportional relationship equations (5) and (6) can be used for rapid and practical online evaluation of the power grid rotation inertia.

5. The method for rapid and practical online calculation of the moment of inertia taking into account the power difference ratio according to claim 4 is characterized by: The proportional relationship equations (5) and (6) are used to perform a rapid and practical online evaluation of the power grid rotation inertia, including: converting the measured H in a 1000MW large single generator trip event in the power grid into 累加 Substitute the data into formula (6) and get H 切机 It is 325810.2MW.s, which proves the accuracy and practicality of proportional equations (5) and (6). Equations (5) and (6) can be used for rapid and practical online evaluation of power grid rotation inertia.

6. A computer storage medium, characterized in that: The computer storage medium stores a computer program, which, when executed by a processor, implements the steps of the method for rapid and practical online calculation of the moment of inertia taking into account the power difference ratio as described in any one of claims 1 to 5.

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