Power grid oscillation analysis method based on regional inertia difference

Abstract

The invention belongs to the technical field of electric power grids, and provides a power grid oscillation analysis method based on regional inertia difference, which comprises the following steps of: firstly, establishing a regional equivalent inertia model through regional division and capacity weighted aggregation, and describing frequency response difference of each region under disturbance by combining a regional frequency dynamic equation and a power angle-power coupling relationship; an inter-region low-frequency oscillation mechanism is disclosed; secondly, by means of system state space and characteristic value modal analysis, the weak area of oscillation and tie line coupling parameters can be positioned, and the interpretability and operability of diagnosis are further improved; besides, indexes such as maximum frequency deviation and inertia difference are introduced to realize risk quantification and rapid assessment decision closed loop, an inertia support configuration and operation mode adjustment strategy can be generated accordingly, the frequency deviation and oscillation risk can be reduced, and the method is suitable for a high-proportion new energy access scene.

Description

Technical Field

[0001] This invention relates to the field of power grid technology, and in particular to a method for analyzing power grid oscillations based on regional inertia differences. Background Technology

[0002] With the rapid development and large-scale grid connection of new energy power generation technologies such as wind power and photovoltaics, the power supply structure and operating characteristics of the power system have undergone significant changes. Compared with traditional synchronous generators, new power sources are usually connected to the grid through power electronic devices, which do not possess inherent mechanical inertia characteristics, leading to a continuous decline in the equivalent inertia level of the power system. Under conditions of high proportion of new energy integration, the power system's frequency buffering capacity against disturbances weakens, the frequency change rate accelerates, and the system frequency stability faces new challenges.

[0003] Meanwhile, due to differences in the distribution of new energy resources, grid structure, and regional load characteristics, the number and capacity of synchronous generators in different regions are significantly uneven, resulting in a non-uniform spatial distribution of power system inertia. Under these non-uniform inertia distribution conditions, when the system is subjected to disturbances such as load fluctuations and changes in power output, the dynamic frequency response of different regions varies significantly. Low-inertia regions are more prone to larger frequency change rates and rate deviations, which in turn trigger dynamic power redistribution through inter-regional tie lines. Existing power system frequency stability and oscillation analysis methods are mostly based on single-machine or local grid modeling, or assume a uniform inertia distribution in system analysis, making it difficult to accurately reflect the impact of spatial differences in inertia within the grid on regional frequency response and inter-regional low-frequency oscillations. While some methods consider local or nodal inertia characteristics, they lack a unified regional modeling framework at the system level, making it difficult to systematically characterize inter-regional power coupling, oscillation mode formation mechanisms, and their relationship with inertia distribution. Furthermore, existing technologies for analyzing power system oscillations mostly remain at the qualitative description or offline assessment stage, lacking a comprehensive analysis method that can simultaneously consider regional inertia differences, regional frequency dynamic response, and oscillation risk assessment. This makes it difficult to provide effective basis for identifying low-inertia areas, allocating inertia support resources, and adjusting operating modes.

[0004] Therefore, there is an urgent need for a power system oscillation analysis method that can take into account regional inertia differences, regional frequency dynamics, and inter-regional power coupling relationships from the system and regional levels, so as to improve the frequency stability and operational safety of the power grid under the condition of high proportion of new energy access. Summary of the Invention

[0005] Therefore, one objective of this invention is to propose a power grid oscillation analysis method based on regional inertia differences, in order to solve the problems mentioned in the background art and overcome the shortcomings of the prior art.

[0006] To achieve the above objectives, the present invention provides a method for analyzing power grid oscillations based on regional inertia differences, comprising: Obtain the parameters of synchronous generators within the power system, and divide the power system into regions based on the parameters of the synchronous generators; Establish a regional equivalent inertia model to calculate the equivalent inertia constant and system average inertia constant for each region; Based on the equivalent inertia constant, a system state-space model is constructed and eigenvalue analysis is performed to extract the system's oscillation modes. A regional inertia difference index is constructed based on the equivalent inertia constant and the system average inertia constant. The system oscillation risk is then assessed based on the regional inertia difference index and the oscillation mode quantification.

[0007] As a preferred embodiment, the equivalent inertia model for the region is as follows: ; in, For the region The equivalent inertia constant, and The first in each region The inertia constant and rated capacity of each synchronous generator unit For the region The collection of units within the facility.

[0008] Preferably, the formula for calculating the system's average inertia constant is as follows: ; in, Let be the system's average inertia constant. The number of regions to be divided, For the region The equivalent inertia constant.

[0009] Preferably, constructing the system state-space model based on the equivalent inertia constant includes: Based on the equivalent inertia constant of the region, a frequency dynamic model for each region is established, and its expression is as follows: ; in, For the region The equivalent inertia constant, For the region Real-time frequency deviation, and They are respectively regions The real-time equivalent mechanical power and equivalent electrical power, For the region The equivalent damping coefficient; Establish an inter-regional power coupling model, region With the region Power variation of the connecting lines between Represented as: ; in, For the region With the region The equivalent synchronous power coefficient between them and They are respectively regions With the region The equivalent work angle; Furthermore, the equivalent power angle and frequency in the region satisfy the following relationship: ; By combining the aforementioned frequency dynamic model and power coupling model, a system state-space model considering regional inertia differences is formed: ; in, The system state matrix, This is the system state vector.

[0010] Preferably, the eigenvalue analysis to extract the oscillation modes of the system includes: Eigenvalue analysis of the system state matrix yields the inter-regional low-frequency oscillation modes of the system, with the eigenvalues ​​in the following form: ; in, Modal damping; The modal oscillation angular frequency; Under the dual-region equivalent condition, the relationship between the oscillation angular frequency of the low-frequency oscillation between regions and the region inertia and the coupling strength of the tie line is expressed as follows: ; in, and They are respectively regions and region The equivalent inertia constant; For the region With the region The equivalent synchronous power coefficient between them.

[0011] Preferably, the regional inertia difference index is as follows: ; in, The number of regions to be divided, Let be the system's average inertia constant. For the region The equivalent inertia constant.

[0012] As a preferred option, it also includes: constructing a regional maximum frequency deviation index. : ; in, For the region Real-time frequency deviation.

[0013] Preferably, the equivalent damping coefficient is as follows: ; in, For the first in the region Damping coefficient of a single synchronous generator unit For the first in the region The rated capacity of each synchronous generator unit For the region The load damping coefficient, For the region Total load capacity, For the region The collection of units within the facility.

[0014] Preferably, the region With the region Equivalent synchronous power coefficient between The power transmission capacity and coupling strength of inter-regional tie lines are characterized as follows: ; in, As the system's baseline capacity, The system's rated frequency, For the region With the region The equivalent reactance of the interconnection line is expressed as follows: ; in, For the region With the region The number of inter-connection lines For the region With the region Interval The equivalent reactance of the tie line after reduction ,in For line reactance, This refers to the transformer reactance.

[0015] Preferably, the method further includes dividing the region into a high inertia region, a medium inertia region, and a low inertia region based on the equivalent inertia constant and the system average inertia constant.

[0016] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: This invention presents a power grid oscillation analysis method based on regional inertia differences, which offers significant advantages over traditional methods based on equal inertia across the entire network or offline empirical assessments. First, by establishing regional equivalent inertia models through regional division and capacity-weighted aggregation, and combining regional frequency dynamic equations with power angle-power coupling relationships, the differences in frequency response across regions under disturbances can be characterized, revealing the low-frequency oscillation mechanism between regions. Second, by utilizing system state space and eigenvalue mode analysis, weak areas of oscillation and tie-line coupling parameters can be located, improving the interpretability and operability of the diagnosis. Furthermore, by introducing indicators such as maximum frequency deviation and inertia difference to quantify risk, a rapid assessment and decision-making closed loop can be achieved. Based on this, inertia support configuration and operation mode adjustment strategies can be generated to reduce frequency deviation and oscillation risks, making it suitable for scenarios with a high proportion of renewable energy integration.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is an overall flowchart of a power grid oscillation analysis method based on regional inertia differences according to the present invention. Figure 2 An improved IEEE 39-bus system topology diagram for a power grid oscillation analysis method based on regional inertia differences, provided for embodiments of the present invention; Figure 3 Frequency dynamic response curve of a power grid oscillation analysis method based on regional inertia differences provided in this embodiment of the invention. Figure 4 The diagram shows the power variation of a power grid oscillation analysis method based on regional inertia differences, provided in an embodiment of the present invention.

[0019] Figure 5 This diagram illustrates the correspondence between inertia difference indices and oscillation risk levels in a power grid oscillation analysis method based on regional inertia differences, provided as an embodiment of the present invention.

[0020] Figure 6 This invention provides a regional equivalent inertia and total capacity diagram for a power grid oscillation analysis method based on regional inertia differences, as provided in an embodiment of the present invention. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0022] like Figure 1 As shown, an embodiment of the present invention provides a power grid oscillation analysis method based on regional inertia differences, comprising steps S1-S4.

[0023] S1: Obtain the parameters of the synchronous generators in the power system, and divide the power system into regions based on the parameters of the synchronous generators.

[0024] In this embodiment, firstly, the inertial constants of all synchronous generators in the power system are obtained. and rated capacity Calculate the system's average inertia using capacity weighting. ;by Based on the established thresholds, the power system is divided into Region 1, Region 2, and Region 3 (Region 1: Area 2: Area 3: Simultaneously, it acquires the inertia constant and rated capacity of synchronous generators in each zone, as well as the real-time frequency data, regional active power injection data, and inter-zone tie line power data of each zone.

[0025] S2: Establish a regional equivalent inertia model to calculate the equivalent inertia constant and the system average inertia constant for each region.

[0026] Secondly, regional division and equivalent inertia calculation: Based on the type of power grid units, the penetration rate of new energy sources, and load characteristics, and according to the N regions with similar operating characteristics of the power grid, the synchronous generators in each region are aggregated in a capacity-weighted manner to calculate the regional equivalent inertia constant, which is used to characterize the regional inertial support capacity. The equivalent inertia constant of each region is expressed as: ; in, and The first in each region The inertia constant and rated capacity of each synchronous generator unit; Indicates the area The collection of units within the facility.

[0027] The system's average inertia constant is defined as: .

[0028] S3: Construct a system state-space model based on the equivalent inertia constant and perform eigenvalue analysis to extract the system's oscillation modes.

[0029] Then, a regional frequency dynamics and power coupling model is constructed. Based on the equivalent inertia constant of the region, a frequency dynamics model for each region is established to describe the dynamic relationship between regional frequency deviation and regional power imbalance under disturbance conditions. Its expression is: ; in, Indicates the first Frequency deviation in each region and These represent the equivalent mechanical power and equivalent electrical power of the region, respectively. Indicates the equivalent damping coefficient of the region: ; in, For the first in the region Damping coefficient of a single synchronous machine ( Or PU, typically 0.05 to 0.15 PU); For the region The load damping coefficient ( Or PU, generally taken as 0.02~0.08 PU). For the region Total load capacity (MVA, taken as the maximum or average load capacity of the area).

[0030] Furthermore, the power coupling relationship between regions is modeled; under small perturbation conditions, the power coupling relationship between regions is established. With the region The change in power of the tie line between them is expressed as: ; in: and They are respectively regions and region The equivalent work angle; For the region With the region The equivalent synchronization power coefficient between regions is used to characterize the power transmission capacity and coupling strength of the inter-regional tie line; ; in, The system baseline capacity (MVA, typically 100MVA or the total installed capacity of the region, can be compared with the rated capacity of the synchronous generator). (Standardization) The system's rated frequency (Hz) ); For the region With the region Equivalent reactance of the interconnection line: ; in, Let pu be the reduced equivalent reactance of the k-th tie line. , For line reactance, This refers to the transformer reactance.

[0031] Furthermore, the equivalent power angle and frequency in the region satisfy the following relationship: ; The system dynamic model and oscillation mode analysis combine the regional frequency dynamic model and the inter-regional power coupling model to construct a system state-space model that considers regional inertia differences. ; The system state vector is: ; By performing eigenvalue analysis on the system state matrix, the inter-regional low-frequency oscillation modes of the system are obtained, and their eigenvalue form is as follows: ; in, Indicates modal damping; This represents the angular frequency of the modal oscillation.

[0032] Regarding the relationship between oscillation frequency and inertia difference, under the dual-region equivalent condition, the relationship between the oscillation angular frequency of low-frequency oscillations between regions and the regional inertia and the coupling strength of the tie line can be approximately expressed as: ; in, and They represent the first The region and the first The equivalent inertia constant of each region; Indicates the area With the region The equivalent synchronous power coefficient between them; Based on this, an oscillation risk assessment index is constructed; the regional maximum frequency deviation index and the regional inertia difference index are introduced to assess the system oscillation risk, wherein the regional maximum frequency deviation is defined as: ; Where T is the time window, For the region Real-time frequency deviation.

[0033] S4: Construct a regional inertia difference index based on the equivalent inertia constant and the system average inertia constant, and assess the system oscillation risk based on the regional inertia difference index and the oscillation mode.

[0034] The regional inertia difference index is defined as follows: ; in, Used to measure the degree of dispersion of the system's inertia distribution (generally) For high-risk areas medium-risk area (This refers to low-risk areas); the larger the regional inertia difference index, the smaller the oscillation damping ratio generally will be; N represents the number of regions divided into the system. Indicates the first The equivalent inertia constant of each region; This represents the system's average inertia constant. Based on the oscillation analysis and risk assessment results, low-inertia weak regions (high-inertia regions: Medium inertia region: Low inertia region: This is to suppress low-frequency oscillations between regions and improve the safety of power system operation.

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 2 This is a topology diagram of the improved IEEE 39-node system of the present invention. The diagram illustrates the simulation platform topology adapted to the invention, clearly showing 39 buses, 10 synchronous generators (G1-G10, parameters consistent with Table 1), inter-regional tie lines, and three regions divided by inertia level. A standardized simulation platform with non-uniform inertia distribution is constructed, providing a clear physical basis for subsequent equivalent inertia calculation and model construction. By clearly defining region boundaries and generator affiliations, it directly supports region division and equivalent inertia calculation, and provides a basic platform for power coupling modeling between regions.

[0036] Figure 3 This is a frequency dynamic response curve diagram of the present invention. This figure presents the frequency changes of three inertia regions after load disturbance, with the curves showing characteristics such as the rate of frequency change and the maximum frequency deviation; it intuitively quantifies the impact of inertia differences on frequency response, verifies the accuracy of the regional frequency dynamic equation, directly confirms the construction of the regional frequency dynamic model and the analysis of the oscillation mechanism, clearly shows the logic of inertia non-uniformity - frequency response differentiation - oscillation induction, and provides data support for the identification of weak regions.

[0037] Figure 4 This is a power variation diagram of the present invention. This diagram shows the dynamic changes in the power of the inter-regional tie lines and the active power within the region after the disturbance. The core of the diagram is the oscillation of the power of the regional tie lines, which reveals the coupled oscillation mechanism of power angle-frequency-power and verifies the effectiveness of the inter-regional power coupling model. It echoes the modeling of the inter-regional power coupling relationship and the oscillation mode analysis, proving that the system state-space model can accurately characterize the coupled oscillation mechanism.

[0038] Figure 5 This diagram illustrates the correspondence between the inertia difference index and the oscillation risk level of this invention. The diagram uses curves to show the relationship between the inertia difference index and the oscillation damping ratio, dividing the risk into low / medium / high risk zones using dashed lines representing inertia difference indices of 0.2 and 0.3. It establishes a quantitative mapping between inertia difference and oscillation risk, providing an intuitive risk assessment tool; it directly reflects the construction of oscillation risk assessment indicators, overcoming the limitations of traditional qualitative assessments.

[0039] Figure 6 This is a diagram showing the equivalent inertia and total capacity of the regions in this invention. The diagram uses a dual-axis comparison to display the equivalent inertia constants and total capacity of the three regions, clearly demonstrating the non-proportional relationship between capacity size and inertia level; it quantifies the differences in regional inertia distribution, accurately identifying low-inertia, weak regions; and it echoes the calculation of regional equivalent inertia and oscillation risk assessment, verifying the conclusion that low-inertia regions are the core of risk in this invention.

[0040] In one embodiment, refer to Figure 1-4 This embodiment focuses on improving the IEEE 39-bus system, implementing a power grid oscillation analysis and operation optimization method based on regional inertia differences. The specific process is as follows: Regional Division and Equivalent Inertia Calculation: The IEEE 39-node system is divided into three regions: Region 1 (including G1, G2, and G3), Region 2 (including G4, G5, G6, and G7), and Region 3 (including G8, G9, and G10). Based on the synchronous generator parameters in Table 1, the equivalent inertia of each region is calculated. Table 1 Parameters of Synchronous Generator Units Area 1: ; Area 2: ; Area 3: ; System average inertia: Region 3 is a low inertia region.

[0041] Let the area equivalent damping coefficient be... Equivalent synchronization power coefficient of inter-regional tie lines =0.8 pu / rad =0.6 pu / rad =0.4 pu / rad; Eigenvalue analysis was performed on the system dynamic model to extract the dominant oscillation mode: (damping ratio) oscillation angular frequency ); Calculate the maximum frequency deviation in each region (region 3 after disturbance). The system inertia difference index is: . Area 3 is a high-risk area, and there is a risk of oscillation.

[0042] Deploying two 50MW energy storage units in Region 3 (virtual inertia constant HESS=4s) increases the equivalent inertia of Region 3 to: After compensation, the satisfaction is achieved. It is no longer in the low inertia region.

[0043] Apply a 10MW load disturbance to Area 3: (Decrease of 47.5%) System inertia difference index oscillation damping ratio It meets safety requirements.

[0044] Understandable, As a core indicator for measuring the spatial dispersion of a system's inertia, it is also the root cause of the other three parameters: when As the inertia increases, the differences in equivalent inertia between regions intensify, leading to a significant decrease in the synchronicity of regional frequency response. This results in uncoordinated dynamic changes in the power angle difference between regions, causing a phase lag between power feedback and frequency changes. This process directly leads to modal damping. Reduced damping of oscillations makes it easier to form sustained oscillations, as shown in the examples. =0.35 =0.016, indicating a low-damping, high-risk state; simultaneously, according to the approximate formula for the dual-region oscillation angular frequency... , An increase in this value implies a greater dynamic fluctuation in the mean of the equivalent inertia of the region. Combined with the dynamic changes in the coupling strength between regions, this ultimately leads to... Reduce (oscillation frequency decreases, duration increases, as in the example) ≈0.19Hz, which is a typical low-frequency oscillation between regions; in addition, The larger the equivalent inertia in the low inertia region The smaller the value, the better, according to the regional frequency dynamic equation Its rate of change of frequency Deviation from maximum frequency This increases significantly, and these large frequency deviation regions become concentrated areas of oscillation energy, further intensifying... The reduction and The offset.

[0045] In oscillation analysis: To reveal the root causes of oscillation risks, it is clear that non-uniform inertia distribution is the core cause of oscillation. It reflects the persistence of oscillations and determines whether oscillations are prone to spread and propagate. Characterizing the dynamic properties of oscillations; The actual degree of harm caused by oscillations is directly related to the frequency safety threshold. For example, in the embodiment, through... =0.35 identifies a high-risk operating state, combined with =0.016 (low damping) ≈0.19Hz (low-frequency oscillation) Collaborative analysis at -0.8Hz (severe frequency deviation) accurately pinpointed the low inertia region as the core weak link in the oscillation. It dropped to 0.28, driving Increased to 0.045 (damping enhancement) trending towards a reasonable range The frequency dropped to -0.42 Hz, validating the guiding value of correlation analysis for oscillation optimization.

[0046] Compared with the prior art, the present invention has at least the following advantages: The technical solution of this invention establishes a regional equivalent inertia model by dividing the region and weighting the aggregation of capacity, and constructs a system state space model by combining the regional frequency dynamic equation and the power angle-power coupling relationship. This model describes the frequency response differences in each region caused by inertia differences under disturbance conditions, thereby revealing the low-frequency oscillation mechanism between regions. It solves the problem that traditional methods based on the assumption of equal inertia across the entire network or local modeling methods cannot reflect the impact of inertia spatial differences in the power grid on regional frequency response and low-frequency oscillations between regions.

[0047] The technical solution of this invention utilizes the system state-space model and eigenvalue modal analysis to locate the weak regions that cause oscillations and the key connection coupling parameters, thereby improving the interpretability and operability of the oscillation diagnosis process and overcoming the limitations of existing methods, which result in ambiguous analysis results and are difficult to guide actual operation.

[0048] This invention introduces quantitative assessment tools such as regional maximum frequency deviation and regional inertia difference indicators, enabling rapid and objective assessment of oscillation risk. This effectively reduces system frequency deviation and oscillation risk, making it suitable for the real-time requirements of grid safety operation in scenarios with high proportions of renewable energy integration. By employing optimized strategies for deploying energy storage in low-inertia regions (as described in the embodiments), the oscillation suppression effect is significantly improved. Figure 5 The correlation between the inertia difference index and oscillation risk shown provides an intuitive and quantitative basis for risk assessment.

[0049] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0050] It will be readily understood by those skilled in the art that this invention includes any combination of the inventive description and specific embodiments outlined in the foregoing specification, as well as the various parts shown in the accompanying drawings. Due to space limitations and for the sake of brevity, not all of these combinations have been described in detail. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

[0051] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for power grid oscillation analysis based on regional inertia difference, characterized in that, include: Obtain the parameters of synchronous generators within the power system, and divide the power system into regions based on the parameters of the synchronous generators; Establish a regional equivalent inertia model to calculate the equivalent inertia constant and system average inertia constant for each region; Based on the equivalent inertia constant, a system state-space model is constructed and eigenvalue analysis is performed to extract the system's oscillation modes. A regional inertia difference index is constructed based on the equivalent inertia constant and the system average inertia constant. The system oscillation risk is then assessed based on the regional inertia difference index and the oscillation mode quantification.

2. The method of claim 1, wherein, The equivalent inertia model for the region is as follows: ； wherein, is the equivalent inertia constant of the area, is the equivalent inertia constant of the area, and are the inertia constant and the rated capacity of the i-th synchronous unit in the area, respectively, are the inertia constant and the rated capacity of the i-th synchronous unit in the area, respectively, is the set of units in the area is the set of units in the area 3. The method of claim 1, wherein the step of determining the difference between the regional inertia of the first region and the regional inertia of the second region is performed by a processor of a computer system. The formula for calculating the system's average inertia constant is as follows: ； wherein, is the system average inertia constant, is the number of divided regions, is the equivalent inertia constant of the region .

4. The method of claim 1, wherein the step of determining the difference between the regional inertia of the first region and the regional inertia of the second region is performed by a processor. The construction of the system state-space model based on the equivalent inertia constant includes: Based on the equivalent inertia constant of the region, a frequency dynamic model for each region is established, and its expression is as follows: ； wherein is the equivalent inertia constant of the area , is the real-time frequency deviation of the area , and are the real-time equivalent mechanical power and equivalent electrical power of the area , is the equivalent damping coefficient of the area ; The inter-area power coupling model is established, and the power variation of the tie line between the areas and the areas is represented as: ​ ； wherein, is the equivalent power angle of region is the equivalent power angle of region is the equivalent synchronization power coefficient between regions and are the equivalent power angles of regions and are the equivalent power angles of regions Furthermore, the equivalent power angle and frequency in the region satisfy the following relationship: ； By combining the aforementioned frequency dynamic model and power coupling model, a system state-space model considering regional inertia differences is formed: ； in, The system state matrix, This is the system state vector.

5. The power grid oscillation analysis method based on regional inertia differences as described in claim 4, characterized in that, The step of performing eigenvalue analysis to extract the oscillation modes of the system includes: Eigenvalue analysis of the system state matrix yields the inter-regional low-frequency oscillation modes of the system, with the eigenvalues ​​in the following form: ； in, Modal damping; The modal oscillation angular frequency; Under the dual-region equivalent condition, the relationship between the oscillation angular frequency of the low-frequency oscillation between regions and the region inertia and the coupling strength of the tie line is expressed as follows: ； in, and They are respectively regions and region The equivalent inertia constant; For the region With the region The equivalent synchronous power coefficient between them.

6. The power grid oscillation analysis method based on regional inertia differences as described in claim 1, characterized in that, The regional inertia difference indicators are as follows: ； in, The number of regions to be divided, Let be the system's average inertia constant. For the region The equivalent inertia constant.

7. The power grid oscillation analysis method based on regional inertia differences as described in claim 1, characterized in that, Also includes: Construct the maximum frequency deviation index for the region: ； in, For the region Real-time frequency deviation.

8. The power grid oscillation analysis method based on regional inertia differences as described in claim 4, characterized in that, The equivalent damping coefficient is as follows: ； in, For the first in the region Damping coefficient of a single synchronous generator unit For the first in the region The rated capacity of each synchronous generator unit For the region The load damping coefficient, For the region Total load capacity, For the region The collection of units within the facility.

9. The power grid oscillation analysis method based on regional inertia differences as described in claim 4, characterized in that, The area With the region Equivalent synchronous power coefficient between The power transmission capacity and coupling strength of inter-regional tie lines are characterized as follows: ； in, As the system's baseline capacity, The system's rated frequency, For the region With the region The equivalent reactance of the interconnection line is expressed as follows: ； in, For the region With the region The number of inter-connection lines For the region With the region Interval The equivalent reactance of the tie line after calculation ,in For line reactance, This refers to the transformer reactance.

10. The power grid oscillation analysis method based on regional inertia differences as described in claim 1, characterized in that, Also includes: The region is divided into high inertia region, medium inertia region and low inertia region based on the equivalent inertia constant and the system average inertia constant.

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