A power grid power limit calculation method based on multi-section power flow coupling analysis

Abstract

The application discloses a power grid power limit calculation method based on multi-section coupled power flow analysis, relates to the technical field of power calculation, and is used for solving the problem of convergence stability reduction of multi-section power constraints in a joint solving process. By collecting active power flow of key sections and introducing a power flow transfer distribution factor between sections, a coupling strength index is constructed, strong coupling section groups are screened, new energy output time sequence characteristics and DC external sending instructions are fused in the strong coupling section groups, a source-sink power flow driving vector is formed, an occupation direction identifier is determined, on the basis of static stability limits, joint distribution is performed on the strong coupling section groups, fault state joint margins are constructed in combination with fault power flow transfer increments, boundary compression is performed on the joint distribution results, joint limit initial values are generated, in the occupation relationship analysis, active and occupied section margin redistribution is realized based on distribution steepness evaluation, and modified joint limits are generated, and hierarchical scheduling of multi-section coupled power flow driving is realized.

Description

Technical Field

[0001] This invention relates to the field of power calculation technology, and more specifically, to a method for calculating power limit of a power grid based on multi-section power flow coupling analysis. Background Technology

[0002] In a power grid dispatching system that coordinates large-scale renewable energy grid connection with DC transmission, the power flow distribution exhibits a combination of enhanced cross-section coupling and dynamic reconfiguration. Each key section is not only constrained by its own static stability limit, but also affected by a variety of factors such as power output fluctuations of renewable energy power plants on the source side, adjustments to transmission channel commands, and network topology reconfiguration, causing power flow to migrate and overlap between multiple sections.

[0003] The existing technology has the following shortcomings: Currently, existing technologies lack the ability to uniformly couple and hierarchically represent the distribution characteristics of power flow transfer between cross sections and multi-source driving information. This can easily lead to distortion in the division of strong and weak coupling cross sections and unclear influence transmission relationships between cross sections during the joint quota allocation process. Consequently, the convergence stability of multi-section power constraints is reduced and the local margin allocation deviation is amplified during the joint solution process. Therefore, a power limit calculation method based on multi-section power flow coupling analysis is proposed.

[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] To overcome the aforementioned deficiencies in the prior art, embodiments of the present invention provide a power limit calculation method for power grids based on multi-section power flow coupling analysis. This method utilizes active power flow acquisition at key sections and coupling modeling with the power flow transfer distribution factor between sections, constructs a coupling strength index to screen strongly coupled section groups, integrates the power output timing characteristics of new energy sources with DC transmission commands to form source-sink power flow driving vectors, and combines static stability limits and post-fault power flow transfer increments to construct a joint margin and allocation correction mechanism. This joint calculation method addresses the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for calculating power limit of a power grid based on multi-section power flow coupling analysis, comprising the following steps: Step S1: Collect real-time active power flow data at key sections, obtain the power flow transfer distribution factor between sections, generate the inter-section coupling strength index by combining the real-time active power flow data at key sections and the power flow transfer distribution factor between sections, and screen each key section based on the inter-section coupling strength index to generate a group of strongly coupled sections. Step S2: Retrieve the active power output time series data of the new energy power station group within the range of the strongly coupled section group, analyze the source-side power flow driving characteristics, collect the DC power transmission command value, generate the source-sink power flow driving vector by combining the source-side power flow driving characteristics, and generate the crowding direction identifier after classifying the source-sink power flow driving vector according to the coupling strength index between sections. Step S3: Read the single-section static stability limit of the strongly coupled section group, perform joint allocation of the single-section static stability limit within the strongly coupled section group according to the squeezing direction identifier, generate a joint allocation benchmark, collect the transfer power flow increment after the critical line fault, generate the fault state joint margin by combining the source and sink power flow driving vector, and perform boundary compression on the joint allocation benchmark according to the fault state joint margin to obtain the initial value of the joint limit. Step S4: Identify the squeezed sections and actively squeezed sections in the strongly coupled section group based on the squeezed direction identifier, evaluate the allocation steepness assessment amount between the two, determine whether to perform margin transfer on the actively squeezed sections based on the allocation steepness assessment amount, perform margin recovery on the squeezed sections and generate the corrected joint limit.

[0007] In a preferred embodiment, in step S1, the real-time active power flow of the critical section is the algebraic sum of the active power transmitted by all transmission lines constituting the same critical section at the current calculation time in the positive direction of the section. While collecting real-time active power flow data at key cross sections, the power flow transfer distribution factor between cross sections is determined based on the current network topology and operation mode of the power grid. Based on the standardized results of real-time active power flow at key sections, an inter-section coupling strength index is constructed by integrating the power flow transfer distribution factors between sections. The coupling strength index between sections is calculated using key section i and key section j.

[0008] In a preferred embodiment, in step S1, the inter-section coupling strength index is compared with a preset coupling threshold: When the inter-section coupling strength index between key section i and key section j is higher than or equal to the preset coupling threshold, key section i and key section j are marked as coupled key sections and assigned to the same strongly coupled section group. When the inter-section coupling strength index between key section i and key section j is lower than the preset coupling threshold, key section i and key section j do not constitute a strong coupling relationship, and key section i and key section j each exit the joint solution process.

[0009] In a preferred embodiment, in step S2, after the strong coupling section group is formed, the active power output time series data of the new energy power station group associated with each key section is retrieved within the scope of the strong coupling section group. For each new energy power station, the instantaneous rate of change of active power output of the new energy power station group is obtained by the ratio of the difference in active power output at adjacent sampling times to the sampling interval. The arithmetic mean of the instantaneous active power output change rate within the preset backtracking time is taken to obtain the average active power output change rate of the new energy power station, which is used as the ramping driving force of the new energy power station on the cross-sectional power flow in this calculation cycle. Based on the average rate of change of active power output of each new energy power station, the characteristics of power flow driven by the source side are calculated; While collecting source-side driving information, the DC power transmission command value is read from the operation plan of each DC transmission channel issued by the power grid dispatching system.

[0010] In a preferred embodiment, in step S2, the Max-min normalization algorithm is used to perform normalization processing to obtain the normalized result of the DC power transmission command value; Based on the standardized results of the source-side power flow driving characteristics and DC power transmission command values, the source-sink power flow driving vector is calculated for each key section g in the strongly coupled section group. For each critical section g in the strongly coupled section group, the net encroachment intensity of the critical section g is calculated by combining its source and sink power flow driving vector components with the inter-section coupling strength index of the critical section relative to the other critical sections. Sort the net occupancy intensity of all key sections in the strongly coupled section group from largest to smallest, and perform ternary division within the strongly coupled section group according to the sorting position: When the net encroachment intensity ranking of the critical section g is in the upper third of the strongly coupled section group, the encroachment direction identifier of the critical section g is set to the active encroachment class. When the net occupancy intensity of the critical section g is in the lower third of the strongly coupled section group, the occupancy direction identifier of the critical section g is set to the occupancy class. When the net encroachment intensity of the critical section g is in one-third of the strongly coupled section group, the critical section will be... The squeezing direction identifier is set to a two-way coupling class.

[0011] In a preferred embodiment, in step S3, a joint allocation of the static stability limit of a single section is performed within the strongly coupled section group according to the squeezing direction identifier; When the squeezing direction of critical section g is identified as active squeezing, the joint allocation weight of critical section g is reset to... ; When the occupancy direction of critical section g is identified as the occupied class, the joint allocation weight of critical section g is reset to... ; When the squeezing direction of the critical section g is identified as a bidirectional coupling class, the joint allocation weight of the critical section g is reset to 1; in, The absolute value of the net squeeze strength at the critical section g is given. It represents the maximum absolute value of the net squeezing intensity of all key sections in the strongly coupled section group; Based on the joint allocation weights, the static stability limit of a single section is jointly allocated within a strongly coupled section group to generate a joint allocation benchmark.

[0012] In a preferred embodiment, in step S3, while generating the joint allocation benchmark, the power flow increment after a critical line fault is collected by scanning the anticipated fault set. Based on the transfer of power flow increments after a critical path failure, the joint fault-state margin of strongly coupled section groups is generated by combining the source and sink power flow driving vectors. Based on the joint margin of the fault state, boundary compression is performed on the joint allocation baseline to obtain the initial value of the joint limit: When the joint margin of the fault state is greater than or equal to the preset safety margin, the initial value of the joint limit of the critical section g is taken as the joint allocation benchmark of the critical section g itself. When the joint margin of the fault state is less than the preset safety margin, the initial value of the joint limit of the critical section g is the product of the joint allocation benchmark of the critical section g and the joint margin of the fault state, and then divided by the preset safety margin.

[0013] In a preferred embodiment, in step S4, at the operating point determined by the initial value of the joint quota, the allocation steepness assessment quantity is calculated for each pair of active occupancy section m and each occupied section s. The assigned steepness assessment value is compared with the preset steepness threshold: When the estimated gradient of the distribution between the actively occupied section m and the occupied section s is higher than or equal to the preset gradient threshold, an unequal callback mechanism is triggered for the combination of the actively occupied section m and the occupied section s, and a margin transfer is performed on the actively occupied section m and a margin recovery is performed on the occupied section s. When the estimated gradient of the allocation between the actively encroaching section m and the encroached section s is lower than the preset gradient threshold, the margin allocation between the actively encroaching section m and the encroached section s is considered to be within an acceptable range, and the initial joint limit values ​​of the actively encroaching section m and the encroached section s remain unchanged under this pair of combinations.

[0014] In a preferred embodiment, in step S4, in the unequal callback mechanism, the margin transfer amount and margin recovery amount performed between the active crowding section m and the crowded section s are equal in value and opposite in direction, and the power share transferred from the active crowding section m to the crowded section s is calculated. The active crowding section m performs margin transfer by subtracting the sum of the power share transfer between the active crowding section m and all the crowded sections s that trigger the unequal callback mechanism from the initial value of the joint limit of the active crowding section m, thus obtaining the corrected joint limit of the active crowding section m. The revised joint limit is used as the output of this power limit calculation cycle, and in the next calculation cycle, it is used as the initial value of the joint allocation benchmark to participate in a new round of solution.

[0015] The technical effects and advantages of this invention are as follows: This invention constructs a key section active power flow acquisition mechanism, introduces the inter-section power flow transfer distribution factor to calculate the coupling strength index, and screens strongly coupled section groups. Within the strongly coupled section groups, it integrates the active power output time-series change rate of the new energy power plant group and the DC power transmission command value, normalizes them to form a source-sink power flow driving vector, and completes the division of the crowding direction identification based on the coupling strength index. On the basis of the single section static stability limit, it performs joint allocation of the strongly coupled section group, introduces the post-fault transfer power flow increment to construct the fault state joint margin, and performs boundary compression to form the initial value of the joint limit. In the crowding relationship analysis, based on the allocation steepness evaluation quantity, it performs an unequal margin callback mechanism on the actively crowding section and the crowded section to complete the limit correction and output the final joint limit. This realizes the unified quantification and hierarchical scheduling of multi-section coupled power flow driving relationship, improves the global coordination accuracy of power grid limit calculation, and reduces the fault state boundary convergence deviation and iterative calculation redundancy. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the implementation of a power grid limit calculation method based on multi-section power flow coupling analysis according to the present invention.

[0017] Figure 2 This is a schematic diagram illustrating the steps of a power grid limit calculation method based on multi-section power flow coupling analysis according to the present invention. Detailed Implementation

[0018] 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 embodiments of the present invention, and not all embodiments. 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.

[0019] This invention constructs a key section active power flow acquisition mechanism, introduces the inter-section power flow transfer distribution factor to calculate the coupling strength index, and screens strongly coupled section groups. Within the strongly coupled section groups, it integrates the active power output time-series change rate of the new energy power station group with the DC power transmission command value and normalizes it to form a source-sink power flow driving vector. Combined with the coupling strength index, it completes the division of the crowding direction. Based on the static stability limit of a single section, it performs joint allocation of the strongly coupled section group and introduces the post-fault transfer power flow increment to construct the fault state joint margin and performs boundary compression to form the initial value of the joint limit. In the crowding relationship analysis, based on the allocation steepness evaluation quantity, it performs an unequal margin callback mechanism on the actively crowding section and the crowded section to complete the limit correction and output the final joint limit, realizing the unified quantification and hierarchical scheduling of multi-section coupled power flow driving relationship.

[0020] Example 1 Please see Figures 1 to 2 A method for calculating power limit of power grid based on multi-section power flow coupling analysis is presented below. Step S1: Collect real-time active power flow data at key sections, obtain the power flow transfer distribution factor between sections, generate the inter-section coupling strength index by combining the real-time active power flow data at key sections and the power flow transfer distribution factor between sections, and screen each key section based on the inter-section coupling strength index to generate a group of strongly coupled sections. Step S2: Retrieve the active power output time series data of the new energy power station group within the range of the strongly coupled section group, analyze the source-side power flow driving characteristics, collect the DC power transmission command value, generate the source-sink power flow driving vector by combining the source-side power flow driving characteristics, and generate the crowding direction identifier after classifying the source-sink power flow driving vector according to the coupling strength index between sections. Step S3: Read the single-section static stability limit of the strongly coupled section group, perform joint allocation of the single-section static stability limit within the strongly coupled section group according to the squeezing direction identifier, generate a joint allocation benchmark, collect the transfer power flow increment after the critical line fault, generate the fault state joint margin by combining the source and sink power flow driving vector, and perform boundary compression on the joint allocation benchmark according to the fault state joint margin to obtain the initial value of the joint limit. Step S4: Identify the squeezed sections and actively squeezed sections in the strongly coupled section group based on the squeezed direction identifier, evaluate the allocation steepness assessment amount between the two, determine whether to perform margin transfer on the actively squeezed sections based on the allocation steepness assessment amount, perform margin recovery on the squeezed sections and generate the corrected joint limit.

[0021] The specific implementation is as follows: In step S1, at the beginning of the current power limit calculation cycle, real-time data is collected from all key sections connected to the power grid.

[0022] Critical sections refer to several transmission sections in the power grid that have a controlling effect on the system's transmission capacity and stability boundary. Each critical section consists of a set of parallel transmission lines. The real-time active power flow at the critical section is the algebraic sum of the active power transmitted by all transmission lines constituting the same critical section at the current calculation time in the positive direction of the section. Specifically, the active power of the transmission lines is synchronously transmitted by the power measurement devices deployed on each transmission line, and the active power of the transmission lines under the jurisdiction of the same critical section is algebraically accumulated in the positive direction of the section to obtain the real-time active power flow of the critical section.

[0023] While collecting real-time active power flow data at key cross-sections, the power flow transfer distribution factor between cross-sections is determined based on the current network topology and operation mode of the power grid.

[0024] The cross-sectional power flow transfer distribution factor is the ratio of the change in active power caused by a unit change in the active power of any transmission line under the jurisdiction of a certain critical cross section to the unit change in active power on another critical cross section. It reflects the power flow coupling and transmission relationship between critical cross sections under the current operating mode. Specifically, based on the current power grid topology, unit combination, and load distribution as the basic operating mode, each key section... With another key section The combination, sequentially at the key cross-section Apply a unit active power disturbance to the transmission line and solve the critical section according to the DC power flow model. The change in active power on the cross section is used as the ratio of this change to the applied unit active power disturbance as the power flow transfer distribution factor between cross sections.

[0025] It should be noted that the real-time active power flow at the critical section is measured in megawatts, while the power flow transfer distribution factor between sections is dimensionless. The two cannot be directly multiplied to construct a comparable coupling strength index. Therefore, before generating the coupling strength index between sections, the real-time active power flow at the critical section is first standardized using the Max-min standardization algorithm.

[0026] in, For the k-th critical section, the real-time active power flow is... and These represent the minimum and maximum real-time active power flow values ​​for all critical sections within this calculation period. The standardized result corresponds to the real-time active power flow of the critical section, and its value ranges from [0,1]. The larger the standardized result of the real-time active power flow of the critical section, the higher the power flow load level of the critical section in the current calculation period.

[0027] Based on the standardized results of real-time active power flow at key sections, an inter-section coupling strength index is constructed by integrating the power flow transfer distribution factors between sections. The formula for calculating the inter-section coupling strength index between key section i and key section j is as follows:

[0028] in, For key sections With key sections The inter-sectional coupling strength index between them For key sections For disturbance sources and key sections The inter-sectional power flow transfer distribution factor at the response surface. For key sections For disturbance sources and key sections The inter-sectional power flow transfer distribution factor at the response surface. and Key sections With key sections Standardized results of real-time active power flow at key cross-sections.

[0029] The larger the absolute value of the power flow transfer distribution factor between critical sections, the more significant the power flow transmission effect between critical sections; the larger the standardized result of the real-time active power flow of critical sections, the closer the load level of the critical section is to its limit, and the stronger its power flow driving ability on adjacent critical sections; therefore, the higher the value of the coupling strength index between sections, the stronger the characterization of the critical section. With key sections The stronger the crowding relationship between trends, the stronger the competition.

[0030] It needs to be explained that the reason for taking the absolute value of the tidal current transfer distribution factor between cross sections and taking the geometric mean over the two directions is that tidal current crowding is physically a two-way interaction. Taking only unidirectional data will cause the coupling strength index between cross sections to be biased in the direction of the disturbance. The reason for using the geometric mean is that when the magnitude of the tidal current transfer distribution factor between cross sections in the two directions is close, the value is close to the arithmetic mean. When the value in either direction is too small, the coupling strength index between cross sections is lowered on the side with the smaller value, so as to avoid the key cross sections dominated by unidirectional coupling being misjudged as strong coupling.

[0031] The inter-section coupling strength index is compared with a preset coupling threshold: When the critical section With key sections When the coupling strength index between the cross sections is higher than or equal to the preset coupling threshold, the critical cross section will be... With key sections They are mutually marked as key coupling sections and grouped into the same strongly coupled section group; When the critical section With key sections When the coupling strength index between the cross sections is lower than the preset coupling threshold, the critical cross section With key sections There is no strong coupling relationship, key section With key sections Each component exits the joint solution process, maintaining its single-section static stability limit as the power limit for this calculation cycle.

[0032] It should be noted that the preset coupling threshold is set as follows: before the start of the current power limit calculation cycle, the coupling strength index between all key sections recorded in the power grid historical operation archive is retrieved to form a reference sample. The reference samples are arranged in ascending order, and the upper quartile of the reference samples is taken as the preset coupling threshold. This ensures that the key section combinations with the highest coupling strength index are identified as strongly coupled section groups, thus avoiding the introduction of weakly coupled key sections into the joint solution due to a loose preset coupling threshold.

[0033] In step S2, after the strong coupling section group is formed, the active power output time series data of the new energy power station group associated with each key section is retrieved within the scope of the strong coupling section group.

[0034] A new energy power station cluster is a collection of all wind farms and photovoltaic power stations that transmit active power to the main grid through the transmission lines under the jurisdiction of a strongly coupled cross section group; The active power output time series data of the new energy power station group is the active power output sequence of all new energy power stations under the jurisdiction of the strongly coupled section group within the preset backtracking time before this calculation period, recorded at a uniform sampling interval. It is uniformly transmitted by the power monitoring device of each new energy power station through the data acquisition and monitoring control system.

[0035] The source-side power flow driving characteristics are a comprehensive representation of two characteristics in the time dimension of the active power output time series data of the new energy power station group: the collective climbing direction and the consistency of output between stations. This reflects the tendency of the new energy output side to drive the power flow of the strongly coupled cross section group. Specifically, for the active power output time series data of each new energy power station group, the instantaneous active power output change rate of the new energy power station is obtained by the ratio of the difference in active power output at adjacent sampling times to the sampling interval; then, the arithmetic mean of the instantaneous active power output change rate within the preset backtracking time is taken to obtain the mean value of the active power output change rate of the new energy power station, which is used as the ramp-up driving force of the new energy power station on the cross-sectional power flow in this calculation cycle.

[0036] It should be explained that the power monitoring device is a real-time power acquisition unit installed at the grid connection point of a new energy power station. It includes a power transmitter and its supporting communication interface module. It can continuously collect the active power output of each new energy power station at a uniform sampling interval and send it to the dispatch master station through the data acquisition and monitoring control system.

[0037] Based on the average rate of change of active power output of each renewable energy power station, the characteristics of power flow driven by the source side are calculated:

[0038] in, Characterized by the driving force of the source-side current. For the first The average rate of change of active power output of each new energy power station This represents the total number of new energy power stations under the jurisdiction of the strongly coupled section group. For all Standard deviation of the mean rate of change of active power output of each new energy power station Indicates all The sum of the two new energy power stations.

[0039] The first term in the formula The range of values ​​is This reflects the overall climbing direction of the new energy power station cluster: a positive value and the closer it is to 1 indicates that the climbing direction of each new energy power station is more consistent and points in the positive direction of the cross section; a value closer to 0 indicates that the positive and negative climbing directions between new energy power stations cancel each other out, and the overall climbing direction is not obvious. The next item The value range is (0,1], reflecting the degree of clustering of the average active power output change rate among the renewable energy power plant clusters: when the average active power output change rate of all renewable energy power plants is completely consistent, If the value is zero, the value of this item is 1, indicating the highest degree of aggregation on the source side of the slope; when When the average absolute rate of change increases significantly, this term approaches 0, indicating that the ramp-up range of individual new energy power stations is far from the group average and the degree of clustering is poor.

[0040] The source-side tidal current driving characteristic is the product of the above two items. Its sign inherits the climbing direction, and its amplitude is modulated by the degree of aggregation. Therefore, the larger the absolute value of the source-side tidal current driving characteristic and the more consistent the sign with the positive direction of the cross section, the stronger the driving effect of the new energy side on the tidal current of the strongly coupled cross section group.

[0041] While collecting source-side push information, the DC power transmission command value is read from the operation plan of each DC transmission channel issued by the power grid dispatching system; The DC power transmission command value refers to the active power given value on the rectifier side of each DC transmission channel connected to the key section in the strongly coupled section group within this calculation period, in megawatts.

[0042] The source-side power flow driving characteristics are dimensionless, while the DC power transmission command value is in megawatts. The two cannot be directly added to construct the source-sink power flow driving vector. Therefore, the DC power transmission command value is similarly standardized using the Max-min standardization algorithm to obtain the standardized result of the DC power transmission command value.

[0043] Based on the standardized results of source-side power flow characteristics and DC power transmission command values, each key section in the strongly coupled section group is analyzed. Calculate the source-sink power flow driving vector:

[0044] in, For key sections The source and sink current driving vector components, Characterized by the driving force of the source-side current. The inter-section power flow transfer distribution factor is defined as follows: when the overall injection node of the new energy power station group under the jurisdiction of the strongly coupled section group is taken as the disturbance source and the critical section g is taken as the response surface. For the first The standardized results of the DC power transmission command value for the DC transmission channel. For the first The rectifier-side node of the DC transmission channel is a source of disturbance and a critical section. The inter-sectional power flow transfer distribution factor at the response surface. This represents the summation of all DC transmission channels connected to the strongly coupled section group.

[0045] Source and flow current driven vector components When it is positive, it indicates that the ramp-up of new energy power output and the DC transmission plan will jointly boost the key sections. The upward current pushes in the positive direction of the cross section; the source and sink current drive vector components. When it is negative, it indicates that both factors will affect the critical section. The upward current pushes in the opposite direction to the cross section; the source and sink current drive vector components. When it approaches zero, it indicates that the driving force of new energy sources and the driving force of DC transmission are at the key section. The components of the source and sink power flow driving vectors of all key sections in the strongly coupled section group are arranged in the order of the key section numbers, and together they constitute the source and sink power flow driving vector of the strongly coupled section group.

[0046] It needs to be explained that, and The method of obtaining the power flow transfer distribution factor between key sections is consistent with that in step S1. Only the disturbance source node is replaced by the transmission line under the jurisdiction of the key section as the overall injection node of the new energy power station group or the rectifier side node of the DC transmission channel. The solution model and the basic operation mode remain unchanged.

[0047] Based on the source-sink tidal current driving vector, the direction of the source-sink tidal current driving vector is classified according to the coupling strength index between sections, and a squeezing direction identifier is generated for each key section in the strongly coupled section group. Specifically, for each key section in the strongly coupled section group By combining the source and sink tidal current driving vector components with the inter-section coupling strength index of this critical section relative to other critical sections, the critical section is calculated. Net squeeze intensity:

[0048] in, The net squeeze strength of the critical section g, For key sections Key sections in the same group The inter-sectional coupling strength index between them and Key sections With key sections The source and sink current driving vector components, It is a strongly coupled section group. This indicates that, excluding the key sections, the group of strongly coupled sections... Summing all critical sections outside itself.

[0049] Key section When the net squeezing intensity is positive and large, the critical section The source-sink tidal current driving vector component is significantly higher within the group than other key sections, and its inter-section coupling strength exponent with other key sections is large, indicating that the key sections... The power flow pushes pressure to other key sections; key sections When the net squeezing intensity is negative and the value is small, it indicates that the critical section Bearing the driving pressure output from the other key sections within the group; key sections When the net squeezing intensity is close to zero, it indicates that the critical section The directions of propulsion between the two sections are mutually in and out.

[0050] Sort the net occupancy intensity of all key sections in the strongly coupled section group from largest to smallest, and perform ternary division within the strongly coupled section group according to the sorting position: When the critical section When the net squeezing intensity ranking is in the upper third of the strongly coupled section group, the key section will be... The direction of the squeeze is set to the active squeeze category; When the critical section When the net squeezing intensity ranking is in the lower third of the strongly coupled section group, the key section will be... The direction of the squeeze is set to the squeezed class; When the critical section When the net squeezing intensity ranking is in one-third of the strongly coupled section group, the key section will be... The squeezing direction identifier is set to a two-way coupling class.

[0051] By extracting the source-side tidal current driving characteristics, constructing the source-sink tidal current driving vector, and sorting and classifying the net squeezing intensity, we can objectively determine the relative pushing position of each key section in the strongly coupled section group under the driving effect of the source and sink. This provides a directional category basis for subsequent joint allocation of weights based on the squeezing direction identifier and for identifying the active squeezing section and the squeezed section in the unequal callback mechanism.

[0052] It should be noted that the reason for using the three-part division method to determine the squeezing direction identifier is that its classification basis comes entirely from the relative order of the net squeezing intensity of each key section within the strongly coupled section group. It does not introduce new preset thresholds and avoids classification bias between the active squeezing class and the squeezed class due to the absolute threshold offset.

[0053] In step S3, after the strong coupling section group and the squeeze direction identifier are formed, the single section static stability limit of each key section in the strong coupling section group is read from the power grid static stability calculation result library.

[0054] The single-section static stability limit refers to the maximum active power that a single critical section can transmit when the power grid maintains a stable power angle with small disturbances, without considering the influence of other critical sections. It is calculated offline for each critical section under the current operating mode by the power grid static stability calculation result library, and is measured in megawatts.

[0055] It should be explained that the power grid static stability calculation result library is a structured database in which the dispatching agency performs static stability calculations offline when the power grid operation mode changes, and centrally stores the single-section static stability limits of each key section under the current network topology and operation mode. This result library is triggered to update after each adjustment of the power grid operation mode (including unit start-up and shutdown, changes in DC transmission plans and changes in the main grid topology), ensuring that the single-section static stability limits read in this calculation cycle are consistent with the current operation mode.

[0056] The static stability limit of a single section is jointly allocated within a strongly coupled section group based on the squeezing direction identifier. Specifically, the joint allocation weight is first determined based on the squeezing direction identifier and the net squeezing intensity of each critical section g in the strongly coupled section group: When the squeezing direction of the critical section g is identified as active squeezing, the critical section... The joint allocation rights are reset to ; When the squeezing direction of the critical section g is identified as the squeezing class, the critical section will be... The joint allocation rights are reset to ; When the critical section When the squeezing direction is identified as a bidirectional coupling class, the key section will be... The joint allocation right is reset to 1.

[0057] in, For key sections The absolute value of net squeeze intensity. It represents the maximum absolute value of the net squeezing intensity of all key sections in the strongly coupled section group.

[0058] The larger the absolute value of the net crowding intensity of the active crowding-type critical section, the more critical the section... The smaller the joint allocation weight, the more critical the section. The lower the share undertaken in the joint allocation, the greater the absolute value of the net crowding intensity of the crowded key sections, and the more critical the key section. The larger the joint allocation weight, the more critical the section. The higher the share undertaken in the joint allocation, the higher the weight of the joint allocation of the bidirectional coupling key section, which is always 1 and does not participate in the weight adjustment.

[0059] It should be noted that the reason for using the ratio of the absolute value of net crowding intensity to the maximum value of net crowding intensity as the weight bias is that the ratio ranges from [0,1], is dimensionless, and is determined entirely by the autocorrelation of data within the strongly coupled section group, without the need to introduce additional preset ratio parameters; at the same time, the weight of the active crowding class will not be lower than 0, and the weight of the crowded class will not be higher than 2, to avoid extreme weights causing the static stability limit of a single section to be excessively transferred or excessively increased.

[0060] Based on the joint weight allocation, the static stability limit of a single section is jointly allocated within a strongly coupled section group to generate a joint allocation benchmark:

[0061] in, For key sections The joint allocation benchmark, For key sections The single-section static stability limit, For key sections The joint allocation weights, This is the sum of the single-section static stability limits of all critical sections in the strongly coupled section group. This is the summation result of the joint weight allocation of pairs in a strongly coupled section group, with the static stability limit of a single section as the weight.

[0062] Normalization factor in the formula This is used to ensure that the sum of the joint allocation benchmarks of all key sections in the strongly coupled section group is exactly equal to the sum of the static stability limits of each single key section. This ensures that while the share ceded by the actively squeezed-out key sections is transferred to the squeezed-out key sections, the overall transport capacity of the strongly coupled section group is not artificially amplified or reduced.

[0063] While generating the joint allocation baseline, the incremental power flow after a critical line fault is collected by scanning the anticipated fault set.

[0064] The anticipated fault set refers to the set of transmission lines under the jurisdiction of a strongly coupled section group in the event of a fault. A finite set of all single fault combinations under the criterion; The incremental shift of power flow after a critical path failure refers to the shift of power flow after each critical path failure in the anticipated fault set. The change in active power borne by the remaining transmission lines of the critical section to which the fault belongs and the transmission lines under the jurisdiction of the other critical sections in the same group at the instant the fault is cleared. Specifically, for each critical path fault in the anticipated fault set. Based on the operating mode before the fault, the transmission line where the fault occurred is disconnected, and the power flow of the power grid is resolved according to the DC power flow model. The difference between the real-time active power flow of the critical section g after the fault and the real-time active power flow of the critical section before the fault is recorded as the critical section. Corresponding fault Transfer of power flow increment after critical line fault , measured in megawatts.

[0065] Based on the transfer of power flow increments after a critical path failure, and combined with the source-sink power flow driving vectors, a joint fault-state margin for strongly coupled cross-section groups is generated:

[0066] in, For the joint fault-state margin of strongly coupled section groups, For key sections The single-section static stability limit, For the critical section g, the real-time active power flow is defined. For key sections Corresponding critical path fault After a critical line failure, the power flow increment is transferred. Let g be the source-sink power flow driving vector component of the critical section g. For the anticipated fault set, It is a strongly coupled section group. The coefficient is used to convert the source and sink power flow driving vector components into dimensions. Its value is the ratio of the maximum value of the DC power command value of all DC power transmission channels connected to the strongly coupled section group within this calculation period to the maximum value of the static stability limit of a single section of all key sections in the strongly coupled section group. pass The conversion of the source-sink power flow driving vector components (dimensionless) is mapped back to megawatt dimensions, which are the same dimension as the real-time active power flow at key sections and the power flow increment transferred after a fault on a key line, and can be directly subtracted in the formula.

[0067] The joint fault-state margin reflects the remaining tolerable proportion of the critical section with the strongest relative pressure under the most severe critical line fault in a strongly coupled section group, further driven by the source-sink power flow driving vector. The closer the joint fault-state margin is to 1, the larger the overall tolerable space of the strongly coupled section group under fault conditions; the closer the joint fault-state margin is to 0, the weakest critical section in the group has approached its single-section static stability limit after the most severe critical line fault.

[0068] Based on the joint margin of the fault state, boundary compression is performed on the joint allocation baseline to obtain the initial value of the joint limit: When the combined fault condition margin is greater than or equal to the preset safety margin, the critical section The initial value of the joint limit is taken as the key section. The joint allocation benchmark itself; When the combined fault margin is less than the preset safety margin, the critical section The initial value of the joint limit is taken as the key section. The product of the joint allocation benchmark and the joint margin of the fault state is then divided by the preset safety margin.

[0069] The above formula for calculating boundary compression can be uniformly expressed as:

[0070] in, Let g be the initial joint limit value for the critical section g. For key sections The joint allocation benchmark, For the joint fault-state margin of strongly coupled section groups, This is to pre-set a safety margin.

[0071] The lower the combined fault margin is compared to the preset safety margin, the lower the compression ratio. The smaller the value, the greater the boundary compression force; when the joint margin of the fault state is exactly equal to the preset safety margin, the compression ratio is 1, and the joint allocation benchmark remains unchanged; when the joint margin of the fault state is higher than the preset safety margin, the joint allocation benchmark is already within the allowable range of the safety margin, the min value is 1, and the initial value of the joint limit is equal to the joint allocation benchmark.

[0072] It should be noted that the preset safety margin is set as follows: before the start of the current power limit calculation cycle, the historical operation records of the power grid are retrieved according to... The joint margin values ​​of the fault states corresponding to the qualified operating sections after fault scanning constitute a reference sample. The reference samples are arranged in ascending order, and the lower quartile of the reference samples is taken as the preset safety margin. This ensures that the preset safety margin is on the stricter side of the historical qualified operating boundary, and avoids the preset safety margin being too loose, which would cause the weakest critical section in the group to exceed the limit after the most serious critical line fault.

[0073] In step S4, after the initial value of the joint limit is generated, the active squeezing section and the squeezed section are identified in the strongly coupled section group based on the squeezing direction identifier.

[0074] Actively squeezed sections are key sections in a strongly coupled section group whose squeezing direction is identified as actively squeezed; squeezed sections are key sections in a strongly coupled section group whose squeezing direction is identified as squeezed.

[0075] Key sections with a squeeze direction marked as bidirectional coupling do not enter the asymmetric callback mechanism of this step, and their initial joint limit value is directly used as the corrected joint limit output within this calculation cycle.

[0076] At the operating point determined by the initial value of the joint quota, assess the degree of inequality in the allocation of margin between the actively squeezed section and the squeezed section, and generate an allocation steepness assessment quantity. Specifically, for each pairwise combination of an actively encroaching cross section m and each encroached cross section s, the formula for calculating the steepness assessment is as follows:

[0077] in, , To actively squeeze the cross section m and the squeezed cross section The percentage of steepness between the distributions is the assessment value. and These are the actively encroaching section m and the encroached section, respectively. The initial value of the joint quota, and These are the active encroachment sections. The real-time active power flow of the critical sections of the occupied section s within this calculation cycle. and These are the active encroachment sections. With the squeezed cross section The proportion of remaining margin under the initial value of the joint limit.

[0078] Actively encroaching on the cross section With the squeezed cross section The larger the difference in the remaining margin ratio and the smaller the sum of the two remaining margin ratios, the closer the allocation steepness assessment is to 1. This indicates that under the current initial value of the joint quota, the actively squeezed section has been pushed to near its share limit, while the squeezed section still has a large remaining space, and the margin allocation between the two is highly unequal; the actively squeezed section With the squeezed cross section The closer the remaining margin ratios are, the closer the allocation steepness assessment is to 0, indicating that the margin allocation between the two is relatively balanced.

[0079] The assigned steepness assessment value is compared with the preset steepness threshold: When actively squeezing the cross section With the squeezed cross section When the gradient assessment value between the two sections is higher than or equal to the preset gradient threshold, the active encroachment section is... With the squeezed cross section The combined triggering of the unequal callback mechanism addresses the issue of actively seizing cross-sections. Implementation margin transfer, for the encroached cross section Execute margin recovery; When actively squeezing the cross section With the squeezed cross section When the assessed steepness of the distribution between sections is lower than the preset steepness threshold, the cross-section is actively encroached upon. With the squeezed cross section The margin allocation between them is considered to be within an acceptable range, and the cross-section is actively encroached upon. With the squeezed cross section The initial joint quota values ​​for each pair remain unchanged under this pair.

[0080] The asymmetrical callback mechanism refers to the process of transferring power shares between the actively occupying section and the occupied section based on the difference between their joint initial limits, according to the allocated steepness assessment amount, thereby readjusting the share between the two key sections. In the asymmetrical callback mechanism, the margin transfer amount and margin recovery amount executed between the actively occupying section m and the occupied section s are equal in value and opposite in direction. The calculation formula is as follows:

[0081] in, In order to actively encroach on the cross section To the squeezed section The share of power transferred; In order to actively encroach on the cross section With the squeezed cross section The absolute value of the difference between the initial values ​​of the joint quotas makes The constant non-negative nature ensures that the joint quota for actively squeezed sections decreases constantly during margin transfer, while the joint quota for squeezed sections increases constantly during margin recovery, strictly consistent with the share transfer direction determined by the squeeze direction indicator.

[0082] Actively encroaching on the cross section The implementation margin transfer will proactively squeeze the cross-section. The initial value of the joint quota minus the value of the actively squeezed section The squeezed section that triggers the unequal callback mechanism. The sum of the power share transfers between them yields the active encroachment section. Revised joint quota:

[0083] Encroached cross section Implementing margin recovery will result in the encroachment of cross-sections. The initial value of the joint limit plus the active crowding section triggered by the unequal callback mechanism With the squeezed cross section The sum of the power share transfers between them gives the squeezed section. Revised joint quota:

[0084] in, and These are the active encroachment sections. With the squeezed cross section The revised joint quota, This indicates the squeezed sections that trigger the unequal callback mechanism. Summation, This indicates an active crowding of sections that trigger the unequal callback mechanism. Sum.

[0085] Since the margin transfer amount and the margin recovery amount are on the same pair of active squeeze sections With the squeezed cross section Under the combination of equal and opposite values, the power share transfer between the actively squeezed section and the squeezed section maintains the total share conservation within the strongly coupled section group, without changing the overall transmission capacity of the strongly coupled section group determined in the initial stage of the joint limit.

[0086] It should be noted that the preset steepness threshold is set as follows: Before the start of the current power limit calculation cycle, the corresponding allocation steepness assessment values ​​of the active crowding-out key sections and the crowded-out key sections are retrieved from the historical power grid operation archives under the conditions of stable operation and no triggering of key section over-limit. These values ​​form a reference sample. The reference sample is sorted in ascending order, and the upper quartile of the reference sample is taken as the preset steepness threshold. This ensures that combinations of active crowding-out sections and crowded-out sections whose allocation steepness assessment values ​​fall outside the historical stable operation experience are identified as combinations that need to enter the unequal callback mechanism.

[0087] The corrected joint limit is used as the output of the current power limit calculation cycle, and in the next calculation cycle, it is used as the initial value of the joint allocation benchmark to participate in the new round of solution, so that the joint allocation process of the strongly coupled section group has the ability to continuously correct with direction awareness in multiple consecutive calculation cycles.

[0088] Finally, it should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0089] Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0090] In this document, the singular forms “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that terms such as “comprising / including” or “having” specify the presence of the stated features, integrals, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, integrals, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0091] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0092] The above description of the disclosed embodiments will enable those skilled in the art to make or use various modifications to these embodiments. It will be readily apparent to those skilled in the art that the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for calculating power limit of a power grid based on multi-section power flow coupling analysis, characterized in that: Includes the following steps: Step S1: Collect real-time active power flow data at key sections, obtain the power flow transfer distribution factor between sections, generate the inter-section coupling strength index by combining the real-time active power flow data at key sections and the power flow transfer distribution factor between sections, and screen each key section based on the inter-section coupling strength index to generate a group of strongly coupled sections. Step S2: Retrieve the active power output time series data of the new energy power station group within the range of the strongly coupled section group, analyze the source-side power flow driving characteristics, collect the DC power transmission command value, generate the source-sink power flow driving vector by combining the source-side power flow driving characteristics, and generate the crowding direction identifier after classifying the source-sink power flow driving vector according to the coupling strength index between sections. Step S3: Read the single-section static stability limit of the strongly coupled section group, perform joint allocation of the single-section static stability limit within the strongly coupled section group according to the squeezing direction identifier, generate a joint allocation benchmark, collect the transfer power flow increment after the critical line fault, generate the fault state joint margin by combining the source and sink power flow driving vector, and perform boundary compression on the joint allocation benchmark according to the fault state joint margin to obtain the initial value of the joint limit. Step S4: Identify the squeezed sections and actively squeezed sections in the strongly coupled section group based on the squeezed direction identifier, evaluate the allocation steepness assessment amount between the two, determine whether to perform margin transfer on the actively squeezed sections based on the allocation steepness assessment amount, perform margin recovery on the squeezed sections and generate the corrected joint limit.

2. The power limit calculation method for power grids based on multi-section power flow coupling analysis according to claim 1, characterized in that: In step S1, the real-time active power flow of the critical section is the algebraic sum of the active power transmitted by all transmission lines constituting the same critical section in the positive direction of the section at the current calculation time. While collecting real-time active power flow data at key cross sections, the power flow transfer distribution factor between cross sections is determined based on the current network topology and operation mode of the power grid. Based on the standardized results of real-time active power flow at key sections, an inter-section coupling strength index is constructed by integrating the power flow transfer distribution factors between sections. The coupling strength index between sections is calculated using key section i and key section j.

3. The power limit calculation method for power grids based on multi-section power flow coupling analysis according to claim 2, characterized in that: In step S1, the inter-section coupling strength index is compared with a preset coupling threshold: When the inter-section coupling strength index between key section i and key section j is higher than or equal to the preset coupling threshold, key section i and key section j are marked as coupled key sections and assigned to the same strongly coupled section group. When the inter-section coupling strength index between key section i and key section j is lower than the preset coupling threshold, key section i and key section j do not constitute a strong coupling relationship, and key section i and key section j each exit the joint solution process.

4. The power limit calculation method for power grids based on multi-section power flow coupling analysis according to claim 1, characterized in that: In step S2, after the strong coupling section group is formed, the active power output time series data of the new energy power station group associated with each key section is retrieved within the scope of the strong coupling section group. For each new energy power station, the instantaneous rate of change of active power output of the new energy power station group is obtained by the ratio of the difference in active power output at adjacent sampling times to the sampling interval. The arithmetic mean of the instantaneous active power output change rate within the preset backtracking time is taken to obtain the average active power output change rate of the new energy power station, which is used as the ramping driving force of the new energy power station on the cross-sectional power flow in this calculation cycle. Based on the average rate of change of active power output of each new energy power station, the characteristics of power flow driven by the source side are calculated; While collecting source-side driving information, the DC power transmission command value is read from the operation plan of each DC transmission channel issued by the power grid dispatching system.

5. The power limit calculation method for power grids based on multi-section power flow coupling analysis according to claim 4, characterized in that: In step S2, the Max-min normalization algorithm is used to perform normalization processing to obtain the normalized result of the DC power transmission command value; Based on the standardized results of the source-side power flow driving characteristics and DC power transmission command values, the source-sink power flow driving vector is calculated for each key section g in the strongly coupled section group. For each critical section g in the strongly coupled section group, the net encroachment intensity of the critical section g is calculated by combining its source and sink power flow driving vector components with the inter-section coupling strength index of the critical section relative to the other critical sections. Sort the net occupancy intensity of all key sections in the strongly coupled section group from largest to smallest, and perform ternary division within the strongly coupled section group according to the sorting position: When the net encroachment intensity ranking of the critical section g is in the upper third of the strongly coupled section group, the encroachment direction identifier of the critical section g is set to the active encroachment class. When the net occupancy intensity of the critical section g is in the lower third of the strongly coupled section group, the occupancy direction identifier of the critical section g is set to the occupancy class. When the net encroachment intensity of the critical section g is in one-third of the strongly coupled section group, the critical section will be... The squeezing direction identifier is set to a two-way coupling class.

6. The power limit calculation method for power grids based on multi-section power flow coupling analysis according to claim 1, characterized in that: In step S3, the static stability limit of a single section is jointly allocated within the strongly coupled section group according to the squeezing direction identifier; When the squeezing direction of critical section g is identified as active squeezing, the joint allocation weight of critical section g is reset to... ; When the occupancy direction of critical section g is identified as the occupied class, the joint allocation weight of critical section g is reset to... ; When the squeezing direction of the critical section g is identified as a bidirectional coupling class, the joint allocation weight of the critical section g is reset to 1; in, The absolute value of the net squeeze strength of the critical section g. It represents the maximum absolute value of the net squeezing intensity of all key sections in the strongly coupled section group; Based on the joint allocation weights, the static stability limit of a single section is jointly allocated within a strongly coupled section group to generate a joint allocation benchmark.

7. The power limit calculation method for power grids based on multi-section power flow coupling analysis according to claim 6, characterized in that: In step S3, while generating the joint allocation benchmark, the power flow increment after a critical line fault is collected by scanning the anticipated fault set. Based on the transfer of power flow increments after a critical path failure, the joint fault-state margin of strongly coupled section groups is generated by combining the source and sink power flow driving vectors. Based on the joint margin of the fault state, boundary compression is performed on the joint allocation baseline to obtain the initial value of the joint limit: When the joint margin of the fault state is greater than or equal to the preset safety margin, the initial value of the joint limit of the critical section g is taken as the joint allocation benchmark of the critical section g itself. When the joint margin of the fault state is less than the preset safety margin, the initial value of the joint limit of the critical section g is the product of the joint allocation benchmark of the critical section g and the joint margin of the fault state, and then divided by the preset safety margin.

8. The power limit calculation method for power grids based on multi-section power flow coupling analysis according to claim 7, characterized in that: In step S4, at the operating point determined by the initial value of the joint quota, the allocation steepness assessment quantity is calculated for each pair of active squeezing section m and each squeezed section s. The assigned steepness assessment value is compared with the preset steepness threshold: When the estimated gradient of the distribution between the actively occupied section m and the occupied section s is higher than or equal to the preset gradient threshold, an unequal callback mechanism is triggered for the combination of the actively occupied section m and the occupied section s, and a margin transfer is performed on the actively occupied section m and a margin recovery is performed on the occupied section s. When the estimated gradient of the allocation between the actively encroaching section m and the encroached section s is lower than the preset gradient threshold, the margin allocation between the actively encroaching section m and the encroached section s is considered to be within an acceptable range, and the initial joint limit values ​​of the actively encroaching section m and the encroached section s remain unchanged under this pair of combinations.

9. The power limit calculation method for power grids based on multi-section power flow coupling analysis according to claim 8, characterized in that: In step S4, in the unequal callback mechanism, the margin transfer amount and margin recovery amount performed between the active squeezing section m and the squeezed section s are equal in value and opposite in direction, and the power share transferred from the active squeezing section m to the squeezed section s is calculated. The active crowding section m performs margin transfer by subtracting the sum of the power share transfer between the active crowding section m and all the crowded sections s that trigger the unequal callback mechanism from the initial value of the joint limit of the active crowding section m, thus obtaining the corrected joint limit of the active crowding section m. The revised joint limit is used as the output of this power limit calculation cycle, and in the next calculation cycle, it is used as the initial value of the joint allocation benchmark to participate in a new round of solution.

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