A power station operation method based on power supply contribution coefficient change trend

Abstract

The application discloses a power station operation method based on power supply contribution coefficient change trend, comprising the following steps: step S1, calculating power station power supply contribution coefficient to the branch where protection is located and power station power supply contribution coefficient to the branch where power is increased, and analyzing power station power supply contribution coefficient change trend; step S2, according to power station power supply contribution coefficient calculation result, classifying power stations according to influence on positive sequence power increase coefficient; step S3, according to power station power supply contribution coefficient calculation result and change trend, judging power stations with group error; step S4, according to power station power supply contribution coefficient change trend, judging whether power station group error is caused by operation mode change amplitude increase. The application preselects all power stations with group error needing complex iteration calculation, so that correct power station grouping is realized, multiple iterations are avoided, calculation efficiency is improved, and the application has practical engineering significance.

Description

Technical Field

[0001] This invention relates to the field of power system relay technology, and in particular to a substation operation method based on the changing trend of power supply contribution coefficient. Background Technology

[0002] The safe and stable operation of the power grid depends on the correct operation of relay protection devices, which in turn depends on reasonable and accurate protection settings. In offline setting, calculating protection settings by combining substation operating modes to determine the most stringent power grid operating conditions ensures that the protection devices can operate correctly regardless of changes in the power grid's operating mode during online operation.

[0003] The power contribution coefficient method addresses the issue of power plant operation mode combination in the calculation of positive sequence contribution coefficients. It proposes a method that groups all power plants in the entire network based on the numerical characteristics of the power contribution coefficients before combining them. This method has advantages such as involving all power plants in the system, a small number of operation mode combinations, and high computational efficiency. However, for power grids with complex ring network structures, this method suffers from inaccurate grouping and requires multiple iterative calculations, resulting in a significant decrease in computational efficiency.

[0004] To address this issue, a power plant operation method based on the changing trend of the power contribution coefficient is proposed. Summary of the Invention

[0005] The present invention discloses a power plant operation method based on the changing trend of the power contribution coefficient. By combining the power plant operation modes according to the changing trend of the power contribution coefficient, the clustering results can be pre-corrected, avoiding multiple iterations and improving computational efficiency, thus solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The present invention provides a substation operation method based on the changing trend of power contribution coefficient, comprising the following steps: Step S1, calculating the power contribution coefficient of the substation to the protection branch and the power contribution coefficient of the substation to the auxiliary branch, and analyzing the changing trend of the substation power contribution coefficient.

[0008] Step S2: Based on the calculation results of the power contribution coefficient of the power plants, classify the power plants according to their impact on the positive sequence contribution coefficient;

[0009] Step S3: Determine the power plants with clustering errors based on the calculation results and trends of the power contribution coefficients of the power plants.

[0010] Step S4: Based on the changing trend of the power contribution coefficient of the plant, determine whether the plant grouping error is caused by the increased change in the operating mode.

[0011] Preferably, the power supply contribution coefficient C of the substation to the branch where the protection is located is... R(i) The power contribution coefficient C of the power plant to the auxiliary branch. Z(i) Described by the following expression:

[0012]

[0013] In the formula, N represents the number of power plants, X represents the other end node of all auxiliary branches except node q, and Z represents the number of auxiliary branches. Gi Indicates plant G i The equivalent impedance, Y qx Z represents the admittance of the auxiliary branch. ip Z iq Z ix These are the nodal impedance matrix elements of the entire power grid under the basic operation mode of the power plants.

[0014] Preferably, based on the calculation results of the power contribution coefficient of the power plant, the power plants are classified according to their impact on the positive sequence contribution coefficient, including: analyzing the C... R(i) and C Z(i) The sign and amplitude of the value determine the substation's protection level, classifying it into substation G that protects the opposite busbar. + and protection of the back side busbar station G - The G + and G - Described by the following expression:

[0015]

[0016] The formula represents the plant clustering results under the basic operation mode.

[0017] Preferably, the changing trend of the power supply contribution coefficient of the substation includes: establishing a screening expression for the difference condition Cond by comprehensively considering the difference ΔC and the equivalent impedance change r% corresponding to the change in the substation operation mode:

[0018]

[0019] In the formula, d represents the degree of change in the relative distance between the substation and the busbars on the opposite and back sides of the protection when the substation's operating mode changes; by establishing a set of change trend conditions T, substations that will exhibit grouping errors are identified:

[0020]

[0021] In the formula, ΔC is C R(i) and C Z(i) The difference, ΔC R(i) and ΔC Z(i) C represents the situation when the change in the operating mode of the plant increases.R(i) and C Z(i) The change in quantity.

[0022] Preferably, based on the changing trend of the power contribution coefficient of the substation, it is determined whether the substation grouping error is caused by an increase in the magnitude of changes in the operating mode, including the following steps:

[0023] If the substation does not generate grouping error, it is divided into substations connected to the back bus of the protection and substations connected to the opposite bus of the protection based on the power contribution coefficient calculation results.

[0024] If the plant or station produces errors, the corresponding plant or station will be changed to the correct cluster result based on the error analysis.

[0025] By setting the same operating mode for the plants within the same group, the most stringent network operating state is obtained, and the maximum and minimum values ​​of the positive sequence boosting coefficient are determined to complete the tuning calculation.

[0026] Preferably, substations that do not meet condition Cond are classified as Class A substations. Class A substations are used to represent the absolute value of the difference between the power contribution coefficients of the branch and the auxiliary branch.

[0027] Plants that meet condition Cond but not condition set T are classified as Class B plants, indicating that there is no trend of result reversal within a certain range of operating mode changes, and the plant grouping results will not have errors.

[0028] Plants that simultaneously satisfy condition Cond and condition set T are classified as Class C plants. Class C plants are those that may have grouping errors and need to be reclassified.

[0029] Preferably, if the substation does not generate grouping error, it is divided into substations connected to the busbar on the back side of the protection and substations connected to the busbar on the opposite side of the protection based on the power contribution coefficient calculation results. Substations connected to the busbar on the opposite side of the protection have an amplification effect on the amplification coefficient. Let the grouping of substations connected to the busbar on the opposite side of the protection be G. + The substations connected to the back-side busbar of the protection system have a reducing effect on the boosting factor. Let the grouping of the substations connected to the back-side busbar of the protection system be G. - .

[0030] Preferably, the regrouping of Class C substations includes the following steps: if a substation belongs to the protection of the back side busbar under the basic mode, the substation is regrouped to belong to the protection of the opposite side busbar; if a substation belongs to the protection of the opposite side busbar under the basic mode, the substation is regrouped to belong to the protection of the back side busbar.

[0031] Preferably, the corresponding operating mode is set for the redefined grouping results to complete the combination of operating modes and the calculation of the positive sequence boosting coefficient: if the maximum positive sequence boosting coefficient is calculated, all substations connected to the back bus of the protection are in the small mode and all substations connected to the opposite bus of the protection are in the large mode; if the minimum positive sequence boosting coefficient is calculated, all substations connected to the back bus of the protection are in the large mode and all substations connected to the opposite bus of the protection are in the small mode.

[0032] The beneficial effects of this invention are as follows:

[0033] The present invention discloses a power plant operation method based on the changing trend of power contribution coefficient. This method uses the amplitude of the power contribution coefficient to initially screen out plants that will experience C... R(i) and C Z(i) The method involves reversing the relative magnitude of power plants and using the percentage change in equivalent impedance to characterize the variation in power plant operation mode, thereby calculating the trend of the power contribution coefficient corresponding to the power plant. By pre-identifying power plants that may have errors in the grouping results under the basic mode and reclassifying them into the correct group, the impact of the variation in power plant operation mode on the grouping results can be estimated in advance. The positive sequence boosting coefficient can be calculated in only one step, avoiding multiple iterations, improving computational efficiency, solving the efficiency reduction problem caused by iterative correction when calculating the positive sequence boosting coefficient using the power contribution method, and enhancing the engineering applicability of the power plant operation mode combination method. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a power plant operation method based on the changing trend of power contribution coefficient as described in this invention.

[0035] Figure 2 This is a schematic diagram illustrating the calculation of the positive sequence boosting coefficient in a power grid without a ring network structure as described in this invention;

[0036] Figure 3 This is a schematic diagram of the equivalent impedance of the power plant under different operating modes as described in this invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] This invention provides a power plant operation method based on the changing trend of power contribution coefficient, combined with... Figure 1 To explain, the steps include:

[0039] S1. Calculate the power supply contribution coefficient of the power plant to the protection branch and the power supply contribution coefficient of the power plant to the auxiliary branch, and analyze the changing trend of the power supply contribution coefficient of the power plant.

[0040] S2. Based on the calculation results of the power contribution coefficient of the power plants, classify the power plants according to their impact on the positive sequence contribution coefficient.

[0041] S3. Determine the plants with grouping errors based on the calculation results and changing trends of the power contribution coefficient of the power plants.

[0042] S4. Based on the changing trend of the power contribution coefficient of the plant, determine whether the plant grouping error is caused by the increased change in the operating mode.

[0043] For the calculation of the positive sequence boosting factor in a power grid without a ring network structure, such as Figure 2 As shown, when R1 and R2 cooperate, the positive sequence boosting coefficients of the branch qk where R2 is located and the branch pq where R1 is located are calculated using the following formula:

[0044]

[0045]

[0046] Where I1 represents the current flowing through branch pq where protection R1 is located, I2 represents the current flowing through branch xq, I3 represents the current flowing through branch qk where protection R2 is located, and z G1 It is the equivalent impedance connected to the busbar on the back side of the protection substation, z G2 It is the equivalent impedance connected to the busbar station on the opposite side of the protection.

[0047] If the substation's operating mode changes from a small mode to a large mode, when the substation is connected to the busbar on the back side of the protection, I1 increases and I2 decreases, and the positive sequence boosting coefficient decreases; when the substation is connected to the busbar on the opposite side of the protection via a branch, I1 decreases and I2 increases, and the positive sequence boosting coefficient increases.

[0048] The branch xq that connects G2 and protects the opposite busbar is often referred to as the auxiliary branch, and the busbar q is referred to as the auxiliary busbar.

[0049] Based on the above pattern, the power contribution coefficient is defined as G for any power plant. i The contribution ratios to the current in the protected branch and the current in the auxiliary branch are denoted as C, respectively. R(i) and C Z(i) The C R(i) and C Z(i) Described by the following expression:

[0050]

[0051] In the formula, N represents the number of power plants, X represents the other end node of all auxiliary branches except node q, and Z represents the number of auxiliary branches. Gi Indicates plant G i The equivalent impedance, Y qx Z represents the admittance of the auxiliary branch. ip Z iq Z ix These are the nodal impedance matrix elements of the entire power grid under the basic operation mode of the power plants.

[0052] Analysis of the C R(i) and C Z(i) The sign and amplitude of the value determine the substation's protection level, classifying it into substation G that protects the opposite busbar. + and protection of the back side busbar station G - The G + and G - Described by the following expression:

[0053]

[0054] The formula represents the plant clustering results under the basic operation mode.

[0055] For power plants located in a ring network structure, when the operating mode changes significantly compared to the basic operating mode, the power plant grouping results determined based on the basic operating mode may contain errors. The equivalent impedance diagrams for power plants under different operating modes are shown below. Figure 3 As shown, the percentage change in equivalent impedance r% is used to characterize the change in the plant's operating mode compared to the basic operating mode, with the basic operating mode corresponding to 0%.

[0056] The difference between the power supply contribution coefficients of the substation to the protection branch and the auxiliary branch is defined as:

[0057] ΔC=C R(i) -C Z(i) ,

[0058] For power plants operating in basic mode where ΔC > 0, when r% increases, if the power contribution coefficient of the power plant changes in a trend that satisfies C... R(i) Decrease C Z(i) Increase, C R(i) and C Z(i) Simultaneously increase and C Z(i) Growth rate C R(i) Fast, C R(i) and C Z(i) Simultaneously decrease and C Z(i) Decrease ratio C R(i) In any of the following situations, the results of plant grouping may differ from those obtained under the basic operating mode, i.e., plant grouping error occurs.

[0059] For power plants where ΔC < 0 under basic operating conditions, if the power contribution coefficient of the power plant changes in a trend that satisfies C when r% increases... R(i) Increase C Z(i) Decrease, C R(i) and C Z(i) Simultaneously increase and C Z(i) Growth rate C R(i) Slow, C R(i) and C Z(i) Simultaneously decrease and C Z(i) Decrease ratio C R(i) If any of the following conditions are met, the results of plant grouping will differ from those obtained under the basic operating mode, resulting in plant grouping errors.

[0060] Based on the above analysis, we can obtain the condition set T for judging whether a power plant is likely to experience grouping errors based on the changing trend of the power contribution coefficient. By establishing the changing trend condition set T, we can identify the power plants that will experience grouping errors.

[0061]

[0062] In the formula, ΔC is C R(i) and C Z(i) The difference, ΔC R(i) and ΔC Z(i) C represents the situation when the change in the operating mode of the plant increases. R(i) and C Z(i) The change in quantity.

[0063] For substations where the absolute value of the difference between the power contribution coefficients of the protected branch and the auxiliary branch is large, it is assumed that the relative distance between the substation and the protection back-side bus and the auxiliary bus is large. Within a certain range of substation operation mode changes, the sign of ΔC remains unchanged, and it will not cause the grouping results to differ from the grouping results under the basic operation mode. Therefore, it is unnecessary to calculate the trend of power contribution coefficient changes. The following condition Cond is used to determine which substations need further analysis based on the trend of power contribution coefficient changes to determine whether grouping errors will occur, thereby reducing the computational workload of the substations:

[0064]

[0065] In the formula, d represents the degree of change in the relative distance between the power plant and the busbar on the opposite side of the protection and the busbar on the back side of the protection when the operation mode of the power plant changes. Its value can be adjusted according to the actual engineering conditions.

[0066] Based on the changing trend of the power supply contribution coefficient, the iterative problem of the power supply contribution coefficient method is solved, including the following steps:

[0067] Determine whether the power plant needs further analysis based on the trend of power contribution coefficient changes, and whether the increased variation in operating mode has caused the plant grouping error.

[0068] If the substation does not generate grouping error, it is divided into substations connected to the back bus of the protection and substations connected to the opposite bus of the protection based on the power contribution coefficient calculation results.

[0069] If the plant or station produces errors, the corresponding plant or station will be changed to the correct cluster result based on the error analysis.

[0070] By setting the same operating mode for the plants within the same group, the most stringent network operating state is obtained, and the maximum and minimum values ​​of the positive sequence boosting coefficient are determined to complete the tuning calculation.

[0071] Substations that do not meet the Cond condition are classified as Class A substations. Class A substations have a large absolute value of the difference between the power supply contribution coefficients of the protected branch and the auxiliary branch.

[0072] Plants that meet condition Cond but not condition set T are classified as Class B plants, indicating that there is no trend of result reversal within a certain range of operating mode changes, and the plant grouping results will not have errors.

[0073] Plants that simultaneously satisfy condition Cond and condition set T are classified as Class C plants. Class C plants are those that may have grouping errors and need to be reclassified.

[0074] (1) If there is no grouping error in the power plant, it is divided into two groups based on the power contribution coefficient calculation results: For Class A and Class B power plants, the numerical characteristics reflected in the power contribution coefficient are that the coefficient increases with the change in operating mode (r%), C R(i) and C Z(i) It can be either one positive and one negative, or both positive but with a fixed relative size, i.e., |C R(i) |>|C Z(i) |or|C R(i) |<|C Z(i) |;

[0075] It is believed that under a certain range of changes in the operation mode of the substation, the relative distance between Class A and Class B substations and the busbar is fixed, that is, fixedly connected to the busbar on the back side of the protection or connected to the busbar on the opposite side of the protection. Therefore, they can be directly grouped according to the power contribution coefficient calculation results under the basic operation mode.

[0076] (2) If the plant will produce errors, the corresponding plant will be changed to the correct grouping result according to the error analysis: For Class C plants, as the change in operating mode increases, the influence of the plant on the boosting coefficient will change significantly. The power contribution coefficient value characteristics are that it changes from ΔC>0 to ΔC<0, or from ΔC<0 to ΔC>0, and the relative electrical distance from the protection back bus and the boosting bus changes.

[0077] At this point, the grouping results calculated under the basic operating mode are not applicable to situations where the range of operating mode changes has increased. To avoid the decrease in computational efficiency caused by iterative correction in the power supply contribution factor method, after determining the range of equivalent impedance changes in the substations, substations that will exhibit grouping errors, i.e., Class C substations, are regrouped. If under the basic mode they belong to substation group G... + Then the grouping changes to G. - Conversely, if it belongs to the plant cluster G - Then change to G + ;

[0078] Connected to the busbar on the opposite side of the protection, it has a gain effect on the amplification factor. Let the group it belongs to be G. + Substations connected to the back-side busbar of the protection system have a reducing effect on the boosting factor. Let the substation belong to group G. - .

[0079] Connected to the busbar on the opposite side of the protection, it has a gain effect on the amplification factor. Let the group it belongs to be G. + Substations connected to the back-side busbar of the protection system have a reducing effect on the boosting factor. Let the substation belong to group G. - .

[0080] The corresponding operating modes are set for the re-divided cluster results to complete the combination of operating modes and the calculation of the positive sequence boosting coefficient: if the maximum positive sequence boosting coefficient is calculated, all substations connected to the back side bus of the protection are in the small mode and all substations connected to the opposite side bus of the protection are in the large mode; if the minimum positive sequence boosting coefficient is calculated, all substations connected to the back side bus of the protection are in the large mode and all substations connected to the opposite side bus of the protection are in the small mode.

[0081] To further illustrate the method for combining power plant operation modes based on the changing trend of power contribution coefficient provided in the embodiments of the present invention, the present invention will be further described below in conjunction with embodiments.

[0082] A New England 10-unit 39-bus system is selected, assuming the per-unit electromotive force of the power supply is 1 and the phases are consistent, the transformer turns ratio is 1, and resistance is not considered in the calculation. Taking the protection coordination at bus 8 of line 8-5 and the protection at bus 5 of the downstream line 5-4 as an example, the fault occurs at bus 4, and the fault type is a three-phase metallic short circuit.

[0083] Table 1 shows the calculation and trend analysis of the power contribution coefficients of substations 37 and 38 under different operating modes:

[0084]

[0085] Table 1. Analysis of the changing trends of power contribution coefficients of substations 37 and 38 under different operating modes.

[0086] The plant clustering results were calculated for each plant under the basic operating mode. The maximum positive order boosting coefficient was used as the sorting index to determine the extreme operating mode of the system. The results were compared with those obtained by the enumeration method. The error analysis results are shown in Table 2.

[0087]

[0088]

[0089] Table 2 Comparison of calculation results for extreme system operation modes under different conditions

[0090] The analysis results in Tables 1 and 2 show that the influence of each plant on the positive sequence boosting coefficient is different and changes with the increase of the plant's operating mode. The enumeration results of plants 30-37 and 39 under different variation ranges are consistent with the grouping results under the basic operating mode, while the results of plant 38 are inconsistent.

[0091] Among them, substations 30-36 and 39 are Class A substations, 37 is Class B substation, and 38 is Class C substation. The analysis in Tables 1 and 2 is consistent, that is, as the change range increases, only the relative distance of substation 38 from the protection back bus and the auxiliary bus will change. The grouping results under the basic operation mode are not applicable.

[0092] The improved power plant operation mode combination method based on the power contribution coefficient change trend pre-classifies all power plants in the system. For A and B type power plants, the grouping results under the basic operation mode can be directly applied to determine the power plant operation mode. For C type power plants, the grouping results are further corrected before setting the operation mode. This effectively avoids repeated iterative calculation of the power plant grouping results, and effectively improves the calculation efficiency while taking into account the calculation accuracy.

[0093] In summary, the power plant operation method provided by this invention, based on the changing trend of the power contribution coefficient, preliminarily screens out plants that will experience C-level fluctuations by using the amplitude of the power contribution coefficient. R(i) and C Z(i) The method involves reversing the relative magnitude of power plants and using the percentage change in equivalent impedance to characterize the variation in power plant operation mode, thereby calculating the trend of the power contribution coefficient corresponding to the power plant. By pre-identifying power plants that may have errors in the grouping results under the basic mode and reclassifying them into the correct group, the impact of the variation in power plant operation mode on the grouping results can be estimated in advance. The positive sequence boosting coefficient can be calculated in only one step, avoiding multiple iterations, improving computational efficiency, solving the efficiency reduction problem caused by iterative correction when calculating the positive sequence boosting coefficient using the power contribution method, and enhancing the engineering applicability of the power plant operation mode combination method.

[0094] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A power plant operation method based on the changing trend of power contribution coefficient, characterized in that, Includes the following steps: Step S1: Calculate the power supply contribution coefficient of the substation to the protection branch and the power supply contribution coefficient of the substation to the auxiliary branch, and analyze the changing trend of the substation power supply contribution coefficient. Step S2: Based on the calculation results of the power contribution coefficient of the power plants, classify the power plants according to their impact on the positive sequence contribution coefficient; Step S3: Determine the power plants with clustering errors based on the calculation results and trends of the power contribution coefficients of the power plants. Step S4: Based on the changing trend of the power contribution coefficient of the power plant, determine whether the plant grouping error is caused by the increased change in the operating mode. The changing trend of the power supply contribution coefficient of the power plant in step (3) includes: by comprehensively considering the difference When the equivalent impedance change (r%) corresponds to a change in the operating mode of the power plant, a difference condition Cond screening expression is established: ， In the formula, d represents the degree of change in the relative distance between the substation and the busbars on the opposite and back sides of the protection when the substation's operating mode changes; by establishing a set of change trend conditions T, substations that will exhibit grouping errors are identified: ， In the formula, for and The difference, and When the change in the operation mode of the plant increases and The change in; Substations that do not meet the Cond condition are classified as Class A substations. Class A substations are used to represent the absolute value of the difference between the power contribution coefficients of their respective branch and auxiliary branch. Plants that meet condition Cond but not condition set T are classified as Class B plants, indicating that there is no trend of result reversal within a certain range of operating mode changes, and the plant grouping results will not have errors. Plants that simultaneously satisfy condition Cond and condition set T are classified as Class C plants. Class C plants are those that may have grouping errors and need to be reclassified.

2. The power plant operation method based on the changing trend of power contribution coefficient according to claim 1, characterized in that, The power supply contribution coefficient of the power plant to the protection branch is... The power contribution coefficient of the power plant to the auxiliary branch. Described by the following expression: ， In the formula, N represents the number of power plants, and X represents the other end node of all auxiliary branches except node q. Indicates factory station The equivalent impedance, This indicates the admittance of the auxiliary branch. , , These are the nodal impedance matrix elements of the entire power grid under the basic operation mode of the power plants.

3. The power plant operation method based on the changing trend of power contribution coefficient according to claim 2, characterized in that, Based on the calculation results of the power contribution coefficient of power plants, power plants are classified according to their impact on the positive sequence contribution coefficient, including: analyzing the aforementioned and The sign and amplitude of the signal determine which substation is protected and which is assigned to the opposite busbar substation. and protection of the back side busbar station The and Described by the following expression: ， The formula represents the plant clustering results under the basic operation mode.

4. The power plant operation method based on the changing trend of power contribution coefficient according to claim 1, characterized in that, Based on the changing trend of the power contribution coefficient of the substation, determine whether the substation grouping error is caused by the increased amplitude of changes in operating mode, including the following steps: If the substation does not generate grouping error, it is divided into substations connected to the back bus of the protection and substations connected to the opposite bus of the protection based on the power contribution coefficient calculation results. If a plant or station generates a grouping error, the corresponding plant or station will be changed to the correct grouping result based on the error analysis. By setting the same operating mode for the plants within the same group, the most stringent network operating state is obtained, and the maximum and minimum values ​​of the positive sequence boosting coefficient are determined to complete the tuning calculation.

5. A power plant operation method based on the changing trend of power contribution coefficient according to claim 4, characterized in that, If no grouping error occurs in the substation, it is divided into substations connected to the busbar on the back side of the protection and substations connected to the busbar on the opposite side of the protection, based on the power contribution coefficient calculation results. Substations connected to the busbar on the opposite side of the protection have a gain effect on the enhancement coefficient. Let the grouping of substations connected to the busbar on the opposite side of the protection be... ; Substations connected to the back-side busbar of the protection system have a reducing effect on the amplification factor. Let the substations connected to the back-side busbar of the protection system be grouped as follows: .

6. A power plant operation method based on the changing trend of power contribution coefficient according to claim 1, characterized in that, The regrouping of Class C substations includes the following steps: if a substation belongs to the protection of the back side busbar under the basic mode, the substation group is changed to the protection of the opposite side busbar; if a substation belongs to the protection of the opposite side busbar under the basic mode, the substation group is changed to the protection of the back side busbar.

7. A power plant operation method based on the changing trend of power contribution coefficient according to claim 6, characterized in that, The corresponding operating modes are set for the redefined grouping results to complete the combination of operating modes and the calculation of the positive sequence boosting coefficient: if the maximum positive sequence boosting coefficient is calculated, all substations connected to the back bus of the protection are in the small mode and all substations connected to the opposite bus of the protection are in the large mode; if the minimum positive sequence boosting coefficient is calculated, all substations connected to the back bus of the protection are in the large mode and all substations connected to the opposite bus of the protection are in the small mode.

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