Searching method and system for dynamic branches of accident chain of high-proportion new energy power grid

Abstract

The invention discloses a searching method and system for a dynamic branch of an accident chain of a high-proportion new energy power grid, and belongs to the technical field of safety and stability analysis and control of a large power grid. The method comprises the steps of obtaining typical data of a high-proportion new energy power grid accident, performing load flow calculation based on the typical data, and obtaining a load flow calculation result; based on the load flow calculation result and the initial fault set of the high-proportion new energy power grid, judging element positions and partitions where accidents of the high-proportion new energy power grid occur, performing transient stability calculation based on the element positions and the partitions, and obtaining a transient stability calculation result; and performing index calculation based on the transient stability calculation result, and searching the accident chain dynamic branch of the high-proportion new energy power grid through the calculation result of the index calculation. The application of the invention is beneficial for operation scheduling personnel to better grasp the stability characteristics of the power grid and take stability control measures in time.

Description

Technical Field

[0001] This invention relates to the field of large power grid safety and stability analysis and control technology, and more specifically, to a search method and system for dynamic branches of accident chains in power grids with a high proportion of new energy sources. Background Technology

[0002] my country's energy and power development is in a period of significant strategic opportunity, with the energy supply and demand pattern undergoing rapid and continuous evolution. By the end of 2023, the installed capacity of new energy power generation in my country reached 35.8%, and its electricity generation accounted for 15.8%. In the Northwest Power Grid, the maximum output of new energy power generation accounted for over 50% of total power generation, reaching 58.6% in April 2024. The development of new energy power generation, new transmission technologies, and control technologies has significantly altered the stability characteristics and fault evolution mechanisms of the power grid, increasing the risk and losses from complex, multi-factor faults such as cascading, successive, and clustered faults. Once encountering natural disasters such as droughts, snowstorms, ice storms, floods, earthquakes, and wildfires, the pressure on the safe and stable operation of the power grid will be greatly intensified. The 2019 UK "8.9" blackout occurred when new energy power generation accounted for 40% of total power generation. The initial fault was a line trip caused by a lightning strike, which subsequently triggered overcurrent protection trips in new energy units, ultimately affecting the power supply to 1 million users. The "9.8" incident in my country's power grid in 2021 was caused by a grounding fault in the AC filter of the Yibin converter station, affecting three inter-regional DC lines and three regional power grids at the sending and receiving ends. The DC lines experienced a maximum power fluctuation of 12.8 million kilowatts, with varying degrees of disturbance affecting 16 DC lines in Southwest, East, and Central China. On December 13, 2023, due to freezing rain, three of the four high-voltage transmission lines in Yuanqu County, Shanxi Province, experienced icing faults, and the fourth line subsequently failed, causing a county-wide power outage affecting approximately 200,000 users. On February 20, 2024, Guizhou Province experienced drought and wildfires, with 14 220kV and above main grid lines simultaneously shutting down in severe cases.

[0003] Accident analysis shows that current routine safety and stability analysis based on experience generally does not consider faults with more than three levels of cascading faults. For large-scale AC / DC hybrid power grids with new energy grid integration, the structure is complex, the types of faults are varied, and the operating mode is highly uncertain. Stability analysis based on human experience cannot fully identify potential cascading faults in the power grid. There is an urgent need to study an accident chain search method applicable to future large power grids with a high proportion of new energy.

[0004] The cascading fault modes in large power grids with a high proportion of renewable energy not only include traditional line cascading overloads, but also renewable energy cascading disconnections, DC cascading commutation failures, and even blocking, significantly increasing the complexity of fault chain search. Traditional AC system cascading fault chain search techniques mainly consider one cascading fault mode: line cascading overloads and line disconnections. In the context of new power systems with high renewable energy penetration and multiple DC infeeds, traditional technologies face multiple challenges: on the one hand, the second-level power fluctuations of wind and solar power and the millisecond-level response characteristics of DC systems lead to dynamic coupling across multiple time scales, making it difficult for simulation models based on quasi-steady-state assumptions to accurately capture the interactive evolution process of cascading faults; on the other hand, the cross-regional and cross-voltage-level network diffusion characteristics of fault propagation paths in AC / DC hybrid systems further cause response lag in traditional regional search systems. Summary of the Invention

[0005] To address the above problems, this invention proposes a search method for dynamic branches of fault chains in high-proportion renewable energy power grids, comprising:

[0006] Obtain typical data on power grid accidents involving high proportions of renewable energy, perform power flow calculations based on the typical data, and obtain the power flow calculation results;

[0007] Based on the power flow calculation results and the initial fault set of the high-proportion renewable energy power grid, the component locations and zones where the high-proportion renewable energy power grid accidents occur are determined, and transient stability calculations are performed based on the component locations and zones to obtain the transient stability calculation results.

[0008] Based on the transient stability calculation results, index calculations are performed, and the dynamic branches of the accident chain of high-proportion new energy power grids are searched using the calculation results of the index calculations.

[0009] Optionally, the method also includes:

[0010] After obtaining the power flow calculation results, the grid connection points of the high-proportion new energy power grid, the DC converter station bus, and the load nodes are classified and the power grid is partitioned, and the classification results and partitioning results are obtained.

[0011] The classification results include: the location of each component;

[0012] The zoning results include: DC near zone, new energy near zone, and AC zone.

[0013] Optionally, based on the transient stability calculation results, it is determined whether there is a voltage or frequency collapse in the high-proportion renewable energy power grid. If there is a voltage or frequency collapse, the transient stability calculation is terminated; otherwise, the index calculation is performed.

[0014] Optionally, the calculation results based on the aforementioned indicators are used to search for dynamic branches of the fault chain in high-proportion renewable energy power grids, including:

[0015] If protection control occurs in the transient stability calculation results, the control and protection of the high-proportion new energy power grid is considered the next link in the accident chain. If not, the corresponding component is set as the next link in the accident chain if the component index result is 1. If the index results of all components are less than 1, several components with larger index values ​​are selected as the next link in the accident chain according to the accident chain branching and screening algorithm, and the accident chain search is performed by branching.

[0016] Optional protection controls include: new energy grid disconnection, stabilization control action, DC commutation failure, or lockout.

[0017] Optionally, after entering the next accident chain link, after determining the accident location and partition, transient stability calculation and index calculation are performed again, and the dynamic branches of the accident chain of high-proportion new energy power grid are searched until the system voltage or frequency collapses.

[0018] Optionally, a chain of failures may include one or more faulty components.

[0019] Optional, the calculation of indicators includes: calculation of AC area fault indicators, calculation of new energy area fault indicators and calculation of DC near-area fault indicators;

[0020] The fault indicators for the AC area include: line indicators;

[0021] The fault indicators for the new energy zone include: voltage indicators at the new energy grid connection point, frequency change rate indicators, and frequency indicators.

[0022] The DC near-field fault indicators include: commutation failure indicators, blocking indicators, and transient overvoltage indicators.

[0023] Furthermore, this invention also proposes a search system for dynamic branches of accident chains in high-proportion renewable energy power grids, comprising:

[0024] The power flow calculation unit is used to acquire typical data of power grid accidents with a high proportion of renewable energy, perform power flow calculation based on the typical data, and obtain the power flow calculation results.

[0025] The stability calculation unit is used to determine the component location and partition of the high-proportion renewable energy power grid accident based on the power flow calculation results and the initial fault set of the high-proportion renewable energy power grid, and to perform transient stability calculation based on the component location and partition, and obtain the transient stability calculation results.

[0026] The indicator calculation unit is used to calculate indicators based on the transient stability calculation results, and to search for dynamic branches of the accident chain in high-proportion renewable energy power grids using the calculation results.

[0027] Optionally, the power flow calculation unit is also used for:

[0028] After obtaining the power flow calculation results, the grid connection points of the high-proportion new energy power grid, the DC converter station bus, and the load nodes are classified and the power grid is partitioned, and the classification results and partitioning results are obtained.

[0029] The classification results include: the location of each component;

[0030] The zoning results include: DC near zone, new energy near zone, and AC zone.

[0031] Optionally, based on the transient stability calculation results, it is determined whether there is a voltage or frequency collapse in the high-proportion renewable energy power grid. If there is a voltage or frequency collapse, the transient stability calculation is terminated; otherwise, the index calculation is performed.

[0032] Optionally, the calculation results based on the aforementioned indicators are used to search for dynamic branches of the fault chain in high-proportion renewable energy power grids, including:

[0033] If protection control occurs in the transient stability calculation results, the control and protection of the high-proportion new energy power grid is considered the next link in the accident chain. If not, the corresponding component is set as the next link in the accident chain if the component index result is 1. If the index results of all components are less than 1, several components with larger index values ​​are selected as the next link in the accident chain according to the accident chain branching and screening algorithm, and the accident chain search is performed by branching.

[0034] Optional protection controls include: new energy grid disconnection, stabilization control action, DC commutation failure, or lockout.

[0035] Optionally, after entering the next accident chain link, after determining the accident location and partition, transient stability calculation and index calculation are performed again, and the dynamic branches of the accident chain of high-proportion new energy power grid are searched until the system voltage or frequency collapses.

[0036] Optionally, a chain of failures may include one or more faulty components.

[0037] Optional, the calculation of indicators includes: calculation of AC area fault indicators, calculation of new energy area fault indicators and calculation of DC near-area fault indicators;

[0038] The fault indicators for the AC area include: line indicators;

[0039] The fault indicators for the new energy zone include: voltage indicators at the new energy grid connection point, frequency change rate indicators, and frequency indicators.

[0040] The DC near-field fault indicators include: commutation failure indicators, blocking indicators, and transient overvoltage indicators.

[0041] In another aspect, the present invention also provides a computing device, comprising: one or more processors;

[0042] A processor is used to execute one or more programs;

[0043] When the one or more programs are executed by the one or more processors, the method described above is implemented.

[0044] In another aspect, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the method described above.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] This invention provides a method for searching dynamic branches of fault chains in high-percentage renewable energy power grids, comprising: acquiring typical data of faults in high-percentage renewable energy power grids; performing power flow calculations based on the typical data to obtain power flow calculation results; determining the component locations and zones where faults occur based on the power flow calculation results and the initial fault set of the high-percentage renewable energy power grid, performing transient stability calculations based on the component locations and zones, and obtaining transient stability calculation results; performing index calculations based on the transient stability calculation results, and searching for dynamic branches of fault chains in high-percentage renewable energy power grids using the results of the index calculations. The application of this invention helps operation and dispatch personnel better understand the stability characteristics of the power grid and take timely stability control measures. Attached Figure Description

[0047] Figure 1 This is a flowchart of the method of the present invention;

[0048] Figure 2 This is a flowchart illustrating the calculation process of the accident chain branch search method in an embodiment of the present invention.

[0049] Figure 3 This is a schematic diagram of the accident chain branch in an embodiment of the method of the present invention;

[0050] Figure 4 This is a schematic diagram of an IEEE 39-node computational example containing a high proportion of new energy sources and DC power, as an embodiment of the method of the present invention.

[0051] Figure 5 This is a graph showing the bus frequency deviation of an embodiment of the method of the present invention.

[0052] Figure 6 This is a bus voltage curve diagram of an embodiment of the method of the present invention;

[0053] Figure 7 This is a structural diagram of the system of the present invention. Detailed Implementation

[0054] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0055] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0056] Example 1:

[0057] This invention proposes a search method for dynamic branches of fault chains in high-proportion renewable energy power grids, such as... Figure 1 Shown, including:

[0058] Step 1: Obtain typical data of power grid accidents with a high proportion of renewable energy sources, perform power flow calculation based on the typical data, and obtain the power flow calculation results;

[0059] Step 2: Based on the power flow calculation results and the initial fault set of the high-proportion renewable energy power grid, determine the component location and partition where the high-proportion renewable energy power grid accident occurs, and perform transient stability calculation based on the component location and partition, and obtain the transient stability calculation results.

[0060] Step 3: Based on the transient stability calculation results, perform index calculations, and use the results of the index calculations to search for dynamic branches of the accident chain in high-proportion renewable energy power grids.

[0061] The methods also include:

[0062] After obtaining the power flow calculation results, the grid connection points of the high-proportion new energy power grid, the DC converter station bus, and the load nodes are classified and the power grid is partitioned, and the classification results and partitioning results are obtained.

[0063] The classification results include: the location of each component;

[0064] The zoning results include: DC near zone, new energy near zone, and AC zone.

[0065] Based on the transient stability calculation results, it is determined whether there is a voltage or frequency collapse in the high-proportion new energy power grid. If there is a voltage or frequency collapse, the transient stability calculation is terminated; otherwise, the index calculation is performed.

[0066] The calculation results based on the aforementioned indicators are used to search for dynamic branches of the accident chain in high-proportion renewable energy power grids, including:

[0067] If protection control occurs in the transient stability calculation results, the control and protection of the high-proportion new energy power grid is considered the next link in the accident chain. If not, the corresponding component is set as the next link in the accident chain if the component index result is 1. If the index results of all components are less than 1, several components with larger index values ​​are selected as the next link in the accident chain according to the accident chain branching and screening algorithm, and the accident chain search is performed by branching.

[0068] Among them, protection and control include: new energy grid disconnection, stabilization control action, DC commutation failure or lockout.

[0069] In this process, after entering the next accident chain link, the accident location and partition are determined, and transient stability calculation and index calculation are performed again. The dynamic branches of the accident chain of high-proportion new energy power grid are searched until the system voltage or frequency collapses.

[0070] One link in an accident chain includes one or more faulty components.

[0071] The calculation of indicators includes: calculation of AC zone fault indicators, calculation of new energy zone fault indicators, and calculation of DC near-zone fault indicators.

[0072] The fault indicators for the AC area include: line indicators;

[0073] The fault indicators for the new energy zone include: voltage indicators at the new energy grid connection point, frequency change rate indicators, and frequency indicators.

[0074] The DC near-field fault indicators include: commutation failure indicators, blocking indicators, and transient overvoltage indicators.

[0075] The invention will be further illustrated below with specific examples:

[0076] This invention aims to address two core shortcomings of traditional fault chain search technologies in high-proportion renewable energy and AC / DC hybrid power grids: high false negative rates for multi-mode fault paths and low efficiency of cross-temporal dynamic extrapolation. Addressing novel fault evolution modes such as low-voltage ride-through or disconnection of renewable energy clusters, DC commutation failure or blocking, and transient overvoltage caused by single or multiple faults in the AC system, as well as the damage to the grid structure caused by traditional line cascading overload modes, this invention overcomes the bottleneck of traditional quasi-steady-state simulation's inability to characterize multi-timescale interactions by constructing a dynamic characteristic fault chain model for renewable energy-AC / DC hybrid equipment. Based on electromechanical transient characteristic parameters, a heuristic search rule is established to effectively identify fault propagation paths involving multi-dimensional coupling of voltage, frequency, power angle, and power. A multi-branch path dynamic screening mechanism is designed to achieve accurate identification of high-risk fault chains and optimized allocation of computational resources. The core value of this invention lies in establishing a multi-branch fault chain search technology system adapted to new power system configurations, providing decision support for the safe and stable operation of the power grid and the interruption of cascading faults. Its specific implementation process is as follows: Figure 2 Shown, including:

[0077] (1) Based on a typical data, power flow calculation is performed first, and then the new energy grid connection point, DC converter station bus and load node are classified. At the same time, the power grid is divided into DC near zone, new energy near zone and AC zone.

[0078] (2) Based on the power flow calculation results, call the initial fault set, determine which power grid zone the fault occurred in, and perform stability calculation.

[0079] (3) Read the transient stability calculation results and determine whether there is a voltage or frequency collapse. If there is a voltage or frequency collapse, terminate the calculation; if there is no voltage or frequency collapse, record the stability calculation results and then perform index calculation.

[0080] (4) For the protection and control that occurs in the stability calculation of (3), such as new energy grid disconnection, stability control action, DC commutation failure or blockage, it is considered as the next link of the accident chain and the link is assigned a value of 1; if there is no such protection and control action, proceed directly to (5).

[0081] (5) By calculating the index, the component with an index result of 1 is set as the next link in the accident chain (an accident chain link may contain multiple faulty components); when the index results of all components are less than 1, according to the accident chain branching and filtering algorithm, several components with larger indexes are selected as the next links in the accident chain, and the accident chain search is performed by branching.

[0082] (6) After all the components of the next accident chain link are set to fail, the fault location and zone are determined first, and then stability calculation and index calculation are performed.

[0083] (7) Continue with steps (3), (4), (5), and (6) until the system voltage or frequency collapses.

[0084] The calculation indicators include:

[0085] The calculation indicators mentioned in the calculation process include: line indicators for AC zone faults, voltage indicators, frequency change rate indicators, and frequency indicators for new energy grid connection points for new energy zone faults, and commutation failure (blocking) indicators and transient overvoltage (blocking) indicators for DC near-zone faults.

[0086] (1) AC area malfunction:

[0087] After a fault occurs in the AC area (usually a line fault), considering the cascading faults caused by the operation of out-of-step protection, overcurrent protection, or backup protection, calculate the following line parameters:

[0088]

[0089] Where k represents the k-th line, i represents the fault chain caused by the i-th initial fault, and j represents the j-th fault that has already occurred. This refers to the line index after the j-th link of the i-th accident chain occurs on the k-th line in the system. The phase angle difference between the two ends of the line after the j-th link of the i-th fault chain in the system occurs is generally only calculated for the tie line power angle. These are the transient current amplitude and steady-state current of line k after the j-th link of the i-th fault chain in the system occurs, respectively. The initial current of line k is (if not the rated value, then the rated value); parameter a is a value between [5, 10], b is a value between [1, 1, 2], and c is a value between [0, 1].

[0090] (2) Fault in the new energy zone:

[0091] After a fault occurs in the new energy area, the voltage and frequency indicators of the new energy grid connection point are calculated, taking into account the grid disconnection caused by high and low voltage ride-through and frequency over-limit.

[0092] Grid connection point voltage specifications (voltage values ​​are all per-unit values):

[0093]

[0094] Where m represents the mth new energy grid connection point, i represents the accident chain caused by the ith initial fault, and j represents the jth fault that has already occurred. This is the voltage evaluation index for the m-th new energy grid connection point after the j-th fault occurs in the i-th fault chain in the system. This represents the transient voltage value at the m-th renewable energy grid connection point after the j-th fault occurs in the i-th fault chain of the system. Let be the initial voltage value of the m-th renewable energy grid connection point in the system; parameter d is a value between [0,1] used to set the weights of the two calculations. By sorting the calculation results of the renewable energy grid connection points, several grid connection points most prone to grid disconnection accidents can be found.

[0095] Frequency indicators:

[0096] a. After a fault occurs at the previous level, and the area is a new energy zone, the frequency change rate index value of the new energy grid connection point is determined using the following method:

[0097]

[0098] Where n is the nth renewable energy grid connection point or load node, This is an evaluation index for the frequency change rate of the nth new energy grid connection point / load node after the jth failure of the i-th accident chain in the system. The frequency change rate at the nth node is related to the system inertia, the proportion of new energy sources, and the power deficit in the power grid. Let n be the frequency of the nth node before the jth failure in the i-th incident chain. This is the point of maximum frequency deviation after the j-th failure in the i-th accident chain. The time from the frequency to the point of maximum deviation; parameter This is the setting value for the frequency change rate protection action, typically taken as [0.1, 0.8]. If the renewable energy power stations in the power grid are equipped with slip protection, this indicator needs to be calculated. For multiple renewable energy power stations within a regional power grid, the calculated result of the frequency change rate indicator is the same for each grid connection point. If there is no such protection, it is not calculated.

[0099] b. After a fault occurs at the previous level, and the area is a new energy zone, calculate the frequency index of the new energy grid connection point:

[0100]

[0101] In the formula, For the frequency index of new energy grid connection points, Let n be the frequency of the nth renewable energy grid connection point. By calculating the index, we can identify the renewable energy power station most prone to frequency disconnection. Generally, for multiple renewable energy power stations within a regional power grid, the calculated frequency index for each grid connection point is the same.

[0102] DC near-field fault:

[0103] Commutation failure (lock-in) indicators:

[0104] Before calculating the commutation failure (blocking) index, first calculate the per-unit value of the critical commutation voltage of the p-th commutator bus:

[0105]

[0106] in, Let X be the per-unit value of the critical commutation voltage of the p-th converter bus. k % represents the per-unit reactance of the converter transformer, and β represents the lead-fire angle of the converter bus. This is the per-unit value of the DC operating current.

[0107] Considering the voltage drop at the converter bus after a fault, which could lead to commutation failure and protection activation, the commutation failure indicators are calculated as follows:

[0108]

[0109] The above formula is the prediction index for DC commutation failure after the j-th fault in the i-th accident chain. If there are multiple DC commutation failure index values ​​of 1, then it is set as multiple DC commutation failure.

[0110] If the fault has occurred at several levels, i.e., j≥2, or if the power grid structure is relatively weak, there may be a situation where the voltage cannot be restored after the commutation failure, resulting in a lockout. Therefore, it is necessary to further calculate whether a lockout fault will occur.

[0111] Calculate the short-circuit ratio index of the p-th converter bus, set a short-circuit ratio threshold for comparison, and define the blocking index as follows:

[0112]

[0113] In the above formula This is the DC blocking index. If the index value is 1, the next level fault is set as the p-th DC blocking fault. The short-circuit ratio is the DC short-circuit ratio after the j-th fault in the i-th fault chain, and the short-circuit ratio threshold parameter is... If this condition is not met, the next level of fault search will be performed again after the commutation fails.

[0114] Transient overvoltage (blocking) indicators:

[0115] After a fault occurs at the next higher level, the transient overvoltage threshold is calculated according to the following formula. The threshold value can be set to 0.95. If the threshold value is lower than 0.95, the transient overvoltage problem is not considered. If it exceeds 0.95, the next higher level fault is set to DC blocking.

[0116]

[0117] Termination criteria include:

[0118] After any level of fault is set, stability calculations are performed. If frequency instability or voltage collapse occurs, the search is terminated. The calculation indicators of each link in each fault chain are recorded as the basis for risk assessment.

[0119] To determine if there is a voltage collapse issue, the voltage index of the central point (main grid node) can be used. If the steady-state voltage of three or more central points meets the following index, the search is terminated:

[0120]

[0121] To determine if there is a frequency collapse issue, the steady-state frequency of the central point (main network node) can be used for judgment. The judgment is terminated if the following indicators are met:

[0122] and

[0123] The accident chain branch filtering algorithm includes:

[0124] When all the calculated indicators for a given link in the accident chain are less than 1, a dynamic threshold for that link is set using quantiles. The top p% of data closest to the maximum value are retained, with each data point representing a branch of the accident chain. A diagram illustrating the accident chain branches is shown below. Figure 3 As shown.

[0125] During the search process, each step can calculate a set of data, represented as follows:

[0126] {x1,x2,...,x n}

[0127] Iterate through the dataset, select the maximum value as max_val, calculate the difference, and form a set of differences:

[0128] d i =|x i -max_val|where i = 1, 2, 3...n

[0129] D = {d1, d2, ..., d} n}

[0130] Set D is sorted in ascending order as follows:

[0131] d (1) ≤d (2) ≤...≤d (n)

[0132] Retain the p% data points with the smallest differences and round them to the nearest integer as follows:

[0133] k = trunc[p % (n-1)]

[0134] Therefore, the critical value in set D is: T = d (k+1)

[0135] The set D only needs to retain the k data with the smallest difference, that is, the set D satisfies d i Data points ≤ T. These k smallest differences represent the k branches of the next level of the accident chain. The parameter p ∈ [1, 100]. The larger p is, the more accident chain branches are retained, but the computational load is greater; the smaller the parameter is, the fewer accident chain branches are retained, but the computational efficiency is higher. Considering all factors, the parameter p is generally taken as 20.

[0136] The transition period of new power systems is characterized by a high proportion of renewable energy and large-scale DC integration. Traditional fault chain searches mainly consider line cascading overloads, but fail to adequately consider the voltage coupling characteristics of renewable energy and DC with the system. They also neglect potential high- and low-voltage ride-throughs and grid disconnections from renewable energy sources, as well as potential commutation failures, transient overvoltages, and blocking in DC systems. Conventional fault tree analysis methods have too many branches and large fault chains, resulting in high computational costs and an inability to grasp the typical paths of large power grids with a high proportion of renewable energy. Therefore, this invention, based on electromechanical transient simulation of the power system, prunes most of the extremely low-probability branches and branches that do not conform to the characteristics of the power system through index calculation, while retaining a relatively important cluster of data. This makes the search for power grid fault chains more accurate and efficient, enabling operation and dispatch personnel to better understand the stability characteristics of the power grid and take timely stability control measures.

[0137] This invention is applied to the IEEE 39-node standard example. Since this example is a pure AC system, some improvements were made to reflect its high proportion of renewable energy. At buses Bus-33, Bus-35, and Bus-38, thermal power units were replaced with centralized wind turbines; at Bus-34 and Bus-36, thermal power units were replaced with centralized photovoltaic units; and a DC transmission line was added to buses Bus-22 and Bus-23 to transmit power externally. (See attached diagram) Figure 4 As shown, the output of new energy sources is 3180MW, accounting for 55.5% of the total output. The local load is 4150MW, and the DC power transmission is 1500MW, which is a typical high proportion of new energy power system.

[0138] According to the aforementioned invention process, an initial fault is manually set, and a three-phase short-circuit permanent fault occurs on the Bus-15-Bus-16 line. This line is located in the near-new energy zone and the near-DC zone, which is a composite area of ​​AC, new energy and DC. It is necessary to calculate the indicators of the AC zone, new energy zone and DC zone after the fault at the same time. Considering that the control action of power electronic components is relatively fast, under the condition that the indicators are all 1 for faults in the composite area, the next level of the accident chain should prioritize new energy, then DC, and finally AC faults.

[0139] Calculation results of the communication area indicators:

[0140] Calculations showed that none of the lines experienced transient power angle instability. Based on the assumption that the initial power flow did not exceed the limit, the rated current of the lines in the IEEE 39-bus system was set to 2kA. The calculated steady-state power flow parameters are shown in Table 1.

[0141] Table 1

[0142] Line Name Initial current (A) Transient current (A) Steady-state current (A) Indicator value Bus-2-Bus-3 2423 8601 3289 0.841 Bus-3-Bus-4 1547 7118 2143 0.624 Bus-8-Bus-9 554 3242 1186 0.310 Bus-9-Bus-39 449 3135 1138 0.299 Bus-10-Bus-13 1095 6452 2369 0.619 Bus-13-Bus-14 887 6260 2291 0.599 Bus-14-Bus-15 896 7342 2025 0.620 Bus-16-Bus-17 592 10991 1317 1 Bus-16-Bus-19 5814 2417 3329 0.536 Bus-17-Bus-18 1828 6727 1721 0.551 Bus-17-Bus-27 1239 4825 1627 0.445 Bus-26-Bus-27 1714 5396 2058 0.526

[0143] Calculations were performed on all lines, and the 12 lines with the highest indicators were selected as shown in Table 1. The top 1% of data were selected for the fault chain branches. The indicator of line Bus-16-Bus-17 was 1. Only the indicator value of Bus-16-Bus-17 was retained and selected as the next level fault in the AC area.

[0144] Calculation results of indicators for the new energy zone:

[0145] The voltage and frequency indicators of the new energy area were calculated separately. If the voltage or frequency indicators of the five centralized new energy power stations all reached 1, the next level of fault setting would disconnect the five centralized new energy power stations from the grid, as shown in Table 2.

[0146] Table 2

[0147]

[0148] The calculation results of the DC region indicators are shown in Table 3:

[0149] Table 3

[0150]

[0151] After the initial fault occurred, the transient voltage dropped below the critical voltage value, indicating that commutation failure had occurred in both DC circuits at the next stage. Since the grid structure did not suffer significant damage after the fault in one circuit, and the short-circuit ratio remained high, no fault blocking was set for the next stage fault.

[0152] After setting the next-level faults in the AC, new energy, and DC zones, the system experienced frequency and voltage collapses, such as... Figure 5 and 6 As shown, the calculation terminates, and the fault chain generated under this initial fault is output as follows: {Three-phase permanent short circuit fault of line Bus-15-Bus-16——Bus-33, Bus-34, Bus-35, Bus-36, Bus-38 disconnected from the grid——DC1 and DC2 commutation failure——Line Bus-16-Bus-17 open circuit fault}.

[0153] Example 2:

[0154] This invention also proposes a search system 200 for dynamic branches of fault chains in high-proportion renewable energy power grids, such as... Figure 7 Shown, including:

[0155] The power flow calculation unit 201 is used to acquire typical data of power grid accidents with a high proportion of new energy sources, perform power flow calculation based on the typical data, and obtain power flow calculation results.

[0156] The stability calculation unit 202 is used to determine the component location and partition of the high-proportion renewable energy power grid accident based on the power flow calculation results and the initial fault set of the high-proportion renewable energy power grid, and to perform transient stability calculation based on the component location and partition, and obtain the transient stability calculation results.

[0157] The indicator calculation unit 203 is used to calculate indicators based on the transient stability calculation results, and to search for dynamic branches of the accident chain in high-proportion renewable energy power grids using the calculation results.

[0158] The power flow calculation unit 201 is also used for:

[0159] After obtaining the power flow calculation results, the grid connection points of the high-proportion new energy power grid, the DC converter station bus, and the load nodes are classified and the power grid is partitioned, and the classification results and partitioning results are obtained.

[0160] The classification results include: the location of each component;

[0161] The zoning results include: DC near zone, new energy near zone, and AC zone.

[0162] Based on the transient stability calculation results, it is determined whether there is a voltage or frequency collapse in the high-proportion new energy power grid. If there is a voltage or frequency collapse, the transient stability calculation is terminated; otherwise, the index calculation is performed.

[0163] The calculation results based on the aforementioned indicators are used to search for dynamic branches of the accident chain in high-proportion renewable energy power grids, including:

[0164] If protection control occurs in the transient stability calculation results, the control and protection of the high-proportion new energy power grid is considered the next link in the accident chain. If not, the corresponding component is set as the next link in the accident chain if the component index result is 1. If the index results of all components are less than 1, several components with larger index values ​​are selected as the next link in the accident chain according to the accident chain branching and screening algorithm, and the accident chain search is performed by branching.

[0165] Among them, protection and control include: new energy grid disconnection, stabilization control action, DC commutation failure or lockout.

[0166] In this process, after entering the next accident chain link, the accident location and partition are determined, and transient stability calculation and index calculation are performed again. The dynamic branches of the accident chain of high-proportion new energy power grid are searched until the system voltage or frequency collapses.

[0167] One link in an accident chain includes one or more faulty components.

[0168] The calculation of indicators includes: calculation of AC zone fault indicators, calculation of new energy zone fault indicators, and calculation of DC near-zone fault indicators.

[0169] The fault indicators for the AC area include: line indicators;

[0170] The fault indicators for the new energy zone include: voltage indicators at the new energy grid connection point, frequency change rate indicators, and frequency indicators.

[0171] The DC near-field fault indicators include: commutation failure indicators, blocking indicators, and transient overvoltage indicators.

[0172] Example 3:

[0173] Based on the same inventive concept, this invention also provides a computer device, which includes a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions from the computer storage medium to implement corresponding method flows or corresponding functions, thereby implementing the steps of the methods in the above embodiments.

[0174] Example 4:

[0175] Based on the same inventive concept, this invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the method in the above embodiments.

[0176] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0177] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0178] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0179] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0180] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0181] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A search method for dynamic branches of an accident chain in a high-proportion renewable energy power grid, characterized in that, include: Obtain typical data on power grid accidents involving high proportions of renewable energy, perform power flow calculations based on the typical data, and obtain the power flow calculation results; Based on the power flow calculation results and the initial fault set of the high-proportion renewable energy power grid, the component locations and zones where the high-proportion renewable energy power grid accidents occur are determined, and transient stability calculations are performed based on the component locations and zones to obtain the transient stability calculation results. Based on the transient stability calculation results, index calculations are performed, and the dynamic branches of the accident chain of high-proportion new energy power grids are searched using the calculation results of the index calculations.

2. The search method according to claim 1, characterized in that, The method further includes: After obtaining the power flow calculation results, the grid connection points of the high-proportion new energy power grid, the DC converter station bus, and the load nodes are classified and the power grid is partitioned, and the classification results and partitioning results are obtained. The classification results include: the location of each component; The zoning results include: DC near zone, new energy near zone, and AC zone.

3. The search method according to claim 1, characterized in that, Based on the transient stability calculation results, it is determined whether there is a voltage or frequency collapse in the high-proportion renewable energy power grid. If there is a voltage or frequency collapse, the transient stability calculation is terminated; otherwise, the index calculation is performed.

4. The search method according to claim 1, characterized in that, The calculation results based on the aforementioned indicators are used to search for dynamic branches of the fault chain in high-proportion renewable energy power grids, including: If protection control occurs in the transient stability calculation results, the control and protection of the high-proportion new energy power grid is considered the next link in the accident chain. If not, the corresponding component is set as the next link in the accident chain if the component index result is 1. If the index results of all components are less than 1, several components with larger index values ​​are selected as the next link in the accident chain according to the accident chain branching and screening algorithm, and the accident chain search is performed by branching.

5. The search method according to claim 4, characterized in that, The protection and control measures include: new energy grid disconnection, stabilization control action, DC commutation failure, or blocking.

6. The search method according to claim 4, characterized in that, After entering the next accident chain link, the accident location and partition are determined, and transient stability calculation and index calculation are performed again. The dynamic branches of the accident chain of high-proportion new energy power grid are searched until the system voltage or frequency collapses.

7. The search method according to claim 4, characterized in that, A chain of failures includes one or more faulty components.

8. The search method according to claim 1, characterized in that, The calculation of the indicators includes: the calculation of AC zone fault indicators, the calculation of new energy zone fault indicators, and the calculation of DC near-zone fault indicators. The fault indicators for the AC area include: line indicators; The fault indicators for the new energy zone include: voltage indicators at the new energy grid connection point, frequency change rate indicators, and frequency indicators. The DC near-field fault indicators include: commutation failure indicators, blocking indicators, and transient overvoltage indicators.

9. A search system for dynamic branches of an accident chain in a high-proportion renewable energy power grid, characterized in that, include: The power flow calculation unit is used to acquire typical data of power grid accidents with a high proportion of renewable energy, perform power flow calculation based on the typical data, and obtain the power flow calculation results. The stability calculation unit is used to determine the component location and partition of the high-proportion renewable energy power grid accident based on the power flow calculation results and the initial fault set of the high-proportion renewable energy power grid, and to perform transient stability calculation based on the component location and partition, and obtain the transient stability calculation results. The indicator calculation unit is used to calculate indicators based on the transient stability calculation results, and to search for dynamic branches of the accident chain of high-proportion new energy power grids through the calculation results of the indicator calculation.

10. The search system according to claim 9, characterized in that, The power flow calculation unit is also used for: After obtaining the power flow calculation results, the grid connection points of the high-proportion new energy power grid, the DC converter station bus, and the load nodes are classified and the power grid is partitioned, and the classification results and partitioning results are obtained. The classification results include: the location of each component; The zoning results include: DC near zone, new energy near zone, and AC zone.

11. The search system according to claim 8, characterized in that, Based on the transient stability calculation results, it is determined whether there is a voltage or frequency collapse in the high-proportion renewable energy power grid. If there is a voltage or frequency collapse, the transient stability calculation is terminated; otherwise, the index calculation is performed.

12. The search system according to claim 8, characterized in that, The calculation results based on the aforementioned indicators are used to search for dynamic branches of the fault chain in high-proportion renewable energy power grids, including: If protection control occurs in the transient stability calculation results, the control and protection of the high-proportion new energy power grid is considered the next link in the accident chain. If not, the corresponding component is set as the next link in the accident chain if the component index result is 1. If the index results of all components are less than 1, several components with larger index values ​​are selected as the next link in the accident chain according to the accident chain branching and screening algorithm, and the accident chain search is performed by branching.

13. The search system according to claim 12, characterized in that, The protection and control measures include: new energy grid disconnection, stabilization control action, DC commutation failure, or blocking.

14. The search system according to claim 12, characterized in that, After entering the next accident chain link, the accident location and partition are determined, and transient stability calculation and index calculation are performed again. The dynamic branches of the accident chain of high-proportion new energy power grid are searched until the system voltage or frequency collapses.

15. The search system according to claim 12, characterized in that, A chain of failures includes one or more faulty components.

16. The search system according to claim 9, characterized in that, The calculation of the indicators includes: the calculation of AC zone fault indicators, the calculation of new energy zone fault indicators, and the calculation of DC near-zone fault indicators. The fault indicators for the AC area include: line indicators; The fault indicators for the new energy zone include: voltage indicators at the new energy grid connection point, frequency change rate indicators, and frequency indicators. The DC near-field fault indicators include: commutation failure indicators, blocking indicators, and transient overvoltage indicators.

17. A computer device, characterized in that, include: One or more processors; A processor is used to execute one or more programs; When the one or more programs are executed by the one or more processors, the method described in any one of claims 1-8 is implemented.

18. A computer-readable storage medium, characterized in that, It contains a computer program, which, when executed, implements the method as described in any one of claims 1-8.

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