Method for identifying weak link of power grid for new energy cluster access region

Abstract

The invention discloses a method for identifying weak links of a new energy cluster accessing a regional power grid, and relates to the technical field of power grid analysis, and the method comprises the steps: S1, making a dynamic model of the new energy cluster and the regional power grid; s2, simulating a real-time power flow state by the model; s3, calculating system response data according to the load curve of the regional power grid to form a database; s4, constructing a node weakness index, and calculating a weakness index value of each node and branch of the regional power grid; s5, the nodes and the branches exceeding the set threshold value serve as weak links of the new energy cluster accessing the regional power grid; s6, performing visual display on the topological graph of the regional power grid, and generating a detailed weak link identification report at the same time; according to the method, the power flow change condition caused by the real-time power generation value of the new energy can be accurately simulated, and the weak link can be accurately identified by constructing the targeted node weakness index and calculating the vulnerability index values of each node and each branch.

Description

Technical Field

[0001] The present invention belongs to the technical field of power grid analysis, and particularly relates to a method for identifying weak links in the power grid in areas with new energy clusters connected to the grid. Background Technique

[0002] With the increasing global emphasis on environmental protection and sustainable development, the energy structure is accelerating the transformation from traditional fossil energy to clean and renewable new energy. New energy sources such as solar energy and wind energy, with their advantages of rich resources and no pollution, are continuously increasing their proportion in energy supply. In order to make full use of new energy resources and improve the stability and economy of energy supply, many new energy power generation projects are often developed and constructed on a large scale in the form of clusters. These new energy clusters are distributed in different regions and transmit the generated electricity to various user terminals by connecting to the local power grid. When a large-scale new energy cluster is connected to the local power grid, the original power balance in the power grid is broken, and the power flow distribution becomes more complex and changeable. Frequent and large-scale power fluctuations may lead to power quality problems such as grid voltage over-limit and frequency fluctuations, and may even threaten the safe and stable operation of the power grid;

[0003] At present, in the field of power grid operation management, although there are already various methods and technologies for evaluating the power grid state and analyzing weak links in the power grid, most of them are designed based on the traditional power grid structure and the situation of relatively stable power source access, focusing on static analysis. It is difficult to accurately simulate the dynamic power flow characteristics of the power grid under the condition of real-time power generation changes of new energy, and it is impossible to comprehensively reflect the actual impact of new energy volatility on each node and branch of the power grid. Therefore, we propose a method for identifying weak links in the power grid in areas with new energy clusters connected to the grid. Summary of the Invention

[0004] To solve the above technical problems, the present invention is realized through the following technical solutions:

[0005] The present invention is a method for identifying weak links in the power grid in areas with new energy clusters connected to the grid, including the following steps;

[0006] Step S1: Collect the cluster information of new energy and the topological information of the local power grid, and make a dynamic model of the new energy cluster and the local power grid;

[0007] Step S2: Add the real-time power generation value of the new energy cluster into the corresponding access points of the dynamic model according to the position of the grid node where it is connected, so that the model simulates the real-time power flow state;

[0008] Step S3: Obtain the data information of each node of the power grid through model data analysis, and at the same time form a power generation output curve, calculate the system response data according to the load curve of the local power grid, and form a database;

[0009] Step S4: Obtain power grid information through database information, evaluate the actual operating status of the power grid after the access of new energy, construct node vulnerability indicators, and calculate the vulnerability indicator values of each node and branch in the regional power grid;

[0010] Step S5: Sort the nodes and branches according to the magnitude of the vulnerability indicator values, set thresholds for the nodes and branches, and select the nodes and branches with vulnerability indicator values exceeding the set thresholds as the weak links for the access of new energy clusters to the regional power grid;

[0011] Step S6: Visually display the identified weak links on the topology map of the regional power grid, and at the same time generate a detailed weak link identification report;

[0012] Furthermore, the said Step S1 includes the following steps:

[0013] Step S11: Collect the information covered by the new energy cluster. For each new energy power generation unit, record its installed capacity, power generation type, and geographical location. The installed capacity is clearly marked in standard power units. The power generation type is distinguished among new energy categories such as wind power, photovoltaic power, biomass energy, and hydropower. The geographical location determines its layout position in the geographical space through coordinate positioning. Collect the operating characteristic parameters of the power generation units, including the power regulation range, power factor variation range, start-up and shutdown conditions, and related characteristics;

[0014] Step S12: Obtain the power grid topology information from the relevant departments responsible for the operation and management of the regional power grid, sort out each node in the power grid, and record the name, number, voltage level, and geographical location information of the node;

[0015] Step S13: According to the information of the new energy cluster and the regional power grid, construct a dynamic model through power system modeling software. During the modeling process, connect each new energy power generation unit to the corresponding power grid node, build the connection architecture between each node and branch, set the electrical parameters for the transformer and reactor equipment in the model according to the component parameters, set the governor model and excitation system model of the generator according to the characteristics of different power generation units, and at the same time configure the dynamic characteristic model for various loads.

[0016] Furthermore, the said Step S2 includes the following steps:

[0017] Step S21: Deploy power monitoring devices with communication functions at the new energy power generation site to obtain the power generation values of each new energy power generation unit. Through the communication network, transmit the real-time power generation values to the data processing center. The data processing center adds the real-time power generation values to the corresponding access points of the dynamic model according to the pre-set relationship accurately corresponding to the power grid nodes, and timely remove abnormal data;

[0018] Step S22: Set the boundary conditions for calculating the current load conditions of each node and the reference value of the bus voltage according to the actual operating conditions of the current power grid. Through the iterative calculation process, solve the key variables such as the voltage amplitude, phase angle of each node in the power system, and the power of each branch. The iterative calculation formula is as follows:

[0019]

[0020] Among them, Δθ is the column vector of the correction amount of the node phase angle, and ΔV is the column vector of the correction amount of the node voltage amplitude; ΔP and ΔQ are the column vectors of the active power imbalance and the reactive power imbalance respectively; k represents the number of iterations; R-1 is the inverse matrix of the Jacobian matrix R; simulate the power flow state in the regional power grid under the real-time power generation condition of the new energy cluster.

[0021] Furthermore, the step S3 includes the following steps:

[0022] Step S31: From the results output by the dynamic model simulation, the system extracts the multi-dimensional data information of each node of the power grid. For the voltage data, record the voltage amplitude and phase angle of each node, and analyze the voltage fluctuation conditions of the nodes at different times. For the current data, obtain the magnitude and direction of the injected current of each node, and combine the node voltage information to analyze the power flow characteristics and load levels of the nodes. In terms of power data, calculate and record the active power and reactive power of each node, and analyze the change trend of the power magnitude;

[0023] Step S32: According to the data of the real-time power generation value of each power generation unit in the new energy cluster changing with time, use data processing software to draw the power generation output curves of each power generation unit with time as the horizontal axis and power generation power as the vertical axis according to the time scale and power unit. Integrate the output curves of all power generation units in the same coordinate system, and distinguish different types of new energy power generation curves by means of identification;

[0024] Step S33: Combine the load curve of the regional power grid, and use ATP-EMTP to analyze the voltage changes of each node at the moment and in the short time after the occurrence of preset fault scenarios such as branch short circuits and generator tripping, covering the voltage drop amplitude and recovery time, and evaluate the transient voltage stability of the power grid;

[0025] Step S34: Integrate the extracted node data information, power generation output curve data, and the calculated system response data, select a database management system to establish a database, and in the database, classify and store according to the data type and time series, and set up an indexing mechanism for data query, retrieval, and analysis operations.

[0026] Furthermore, the step S4 includes the following steps:

[0027] Step S41: Retrieve relevant data from the database and comprehensively evaluate the actual operating status of the power grid after the access of new energy. In the voltage stability evaluation link, observe whether the voltage of each node is within the operating range, count the number of voltage violations, the duration, and the amplitude of the violations, and judge the overall voltage stability level of the power grid; for the power balance situation, compare the power generation injection and load power consumption of each node, check whether there is a power deficit or surplus, and whether the power transmission in the power grid is smooth, and pay attention to whether there are branch overloads and power blockages; in terms of the analysis of the fault response ability, check the recovery time and the fault impact range index of the power grid under various fault conditions in the system response data;

[0028] Step S42: Introduce the voltage deviation rate index, and measure the voltage stability of the node by calculating the deviation degree between the actual voltage and the rated voltage of each node. The calculation formula is as follows:

[0029]

[0030] where D is the voltage deviation rate, V is the actual voltage of the node, and VN is the rated voltage of the node. The larger this index value, the farther the node voltage deviates from the rated value, the worse the voltage stability, and the weaker the node;

[0031] Set the power transfer margin index, and judge its power transfer ability by calculating the remaining margin of the node from the power transfer limit under the current operating state. The calculation formula is as follows:

[0032]

[0033] In the formula, S is the power transfer margin, P is the active power actually transmitted by the node currently, and Pmax is the maximum active power that the node can allow to transmit under the current operating conditions; the smaller the power transfer margin, the more likely the node has problems in power transfer, and the higher the vulnerability;

[0034] Construct the short-circuit current ratio index, calculate the ratio of the short-circuit current to the rated current of the node. The short-circuit current ratio is the degree of current impact when a short-circuit fault occurs at the node. The calculation formula of the short-circuit current ratio is as follows:

[0035]

[0036] where L is the current short-circuit ratio, ISC is the effective value of the short-circuit current when a short-circuit fault occurs at the node, and IN is the effective value of the rated current of the node. The larger the short-circuit current ratio, the greater the short-circuit current stress of the electrical equipment at this node, the higher the fault risk, and the weaker the node;

[0037] Reasonably weight and combine the above indicators to form a comprehensive indicator that can comprehensively reflect the vulnerability of the node. The calculation formula is as follows:

[0038] Z = w1×D + w2×S + w3×L;

[0039] Where Z is the comprehensive vulnerability index of the node, w1, w2, and w3 are the weight coefficients corresponding to each index respectively, and w1 + w2 + w3 = 1;

[0040] Step S43: Set the branch power flow overload rate index, and measure the power transmission state of the branch by calculating the ratio of the actual transmitted power of the branch to the rated transmission capacity. The calculation formula is as follows:

[0041]

[0042] Where C is the branch power flow overload rate, P is the active power actually transmitted by the branch currently, and PN represents the rated active power transmission capacity of the branch; when this ratio exceeds 100%, the branch is in an overload state. The higher the overload rate, the more likely the branch is to cause faults due to problems such as overheating, and the higher the vulnerability; even if it is not overloaded, a higher overload rate also means that the branch has a smaller margin in power transmission and a weaker ability to cope with emergencies;

[0043] Construct an index for the impact degree of branch faults, and evaluate its vulnerability by analyzing the impact degree on the overall operation index of the power grid when the branch fails. Use the change amount of relevant indicators after the fault to quantitatively represent the impact degree of the fault. The calculation method is as follows:

[0044] G = ΔP = Pb - Pa;

[0045] Where G is the impact degree of branch faults, Pb represents the total active power of the system when the branch is operating normally, and Pa is the total active power of the system after the branch fails and is disconnected; the impact of branch faults on the operation of the power grid is quantified through the index. The greater the impact degree, the higher the importance and vulnerability of the branch in the power grid, and the greater the harm to the power grid once a fault occurs;

[0046] According to actual needs, perform appropriate weighting on the above branch indicators to form a comprehensive branch vulnerability index. The calculation formula is as follows:

[0047] R = w4×C + w5×G;

[0048] Where R is the comprehensive branch vulnerability index, and w4 and w5 are the weight coefficients corresponding to each index respectively.

[0049] Furthermore, the step S5 includes the following steps:

[0050] Step S51: Through the sorting function provided by the database management system, sort the nodes and branches in descending order according to the calculated vulnerability index values, and rank the weakness levels of different parts of the power grid from high to low in sequence;

[0051] Step S52: For the comprehensive node vulnerability index, when the index value is greater than a specific value, it is determined that the node belongs to a weak link; for the comprehensive branch vulnerability index, according to the actual situation, when the index value is greater than the corresponding value, it is determined that the branch is a weak link.

[0052] Step S53: According to the set threshold, from the sorted node and branch lists, select the nodes and branches whose vulnerability index values exceed the corresponding thresholds. These selected nodes and branches are the weak links of the power grid in the area where the new energy cluster is connected. Record the selected weak links in detail, including name, number, location, and the corresponding vulnerability index value content, to form a weak link list.

[0053] Furthermore, in step S6, through the power grid graphic drawing software, on the topological graph file of the regional power grid, the nodes and branches corresponding to the identified weak links are prominently and intuitively displayed on the topological graph. Use eye-catching colors for identification and special icons for differentiation, so that grid operation and maintenance personnel, planning personnel and other relevant professionals can distinguish the specific locations of the weak links and their distributions in the power grid when viewing the topological graph. At the same time, set the mouse hover prompt information interaction function. When the mouse moves to the weak link identifier, the detailed information of the weak link is automatically displayed, which is convenient for the staff to further view and deeply analyze the specific situation of the weak link, improving the convenience and intuitiveness of information acquisition.

[0054] Generate a weak link identification report based on the drawn topological graph file, introduce the basic situation of the regional power grid, including the power grid coverage, voltage level structure, main substations and transmission line elements, and describe the overall situation of the new energy cluster. List all the identified weak links. For each weak link, explain its location and the corresponding vulnerability index value respectively. At the same time, combined with the power grid operation principle and the previous data analysis results, analyze the reasons for its weakness, so that readers can comprehensively understand the specific conditions and formation reasons of each weak link; for the identified weak links, evaluate the risks they bring to the operation of the regional power grid, analyze from multiple dimensions such as the risk of power outage accidents, the decline of power grid voltage quality, and the impact on the power grid power supply reliability and power quality, and describe them in a quantitative way, so that relevant personnel can clearly and intuitively recognize the severity of the potential hazards of the weak links, providing a key basis for formulating subsequent countermeasures.

[0055] The present invention has the following beneficial effects:

[0056] 1. The present invention can accurately simulate the power flow changes brought about by the real-time power generation value of new energy. By constructing targeted node vulnerability indicators and calculating the vulnerability indicator values of each node and branch, the weak links can be accurately identified, which helps grid operators to know in advance the parts that may have potential safety hazards under complex new energy conditions, and thus take targeted measures such as strengthening the grid structure and optimizing reactive power compensation to effectively prevent problems such as voltage over-limit and frequency fluctuation caused by new energy volatility, greatly improving the overall operation safety and stability of the power grid and reducing the risk of accidents such as power outages.

[0057] 2. The present invention analyzes and evaluates the actual operation state of the power grid by collecting detailed new energy cluster information and regional power grid topology information and based on the formed database. Based on the identified weak link information, it can provide accurate data support and decision-making basis for the optimization and transformation of the power grid, and also helps to reasonably layout new energy access points and adjust the grid structure in the long-term power grid planning, so that it can better adapt to the operation requirements after new energy access, and improve the rationality and overall efficiency of power grid resource allocation.

[0058] 3. By effectively identifying the weak links of the regional power grid, the present invention can timely discover the key parts that restrict new energy consumption, such as power transmission limitation and power quality influence caused by new energy access. On this basis, grid operators can formulate corresponding operation and dispatching strategies to overcome the limitations brought by weak links, enabling the power grid to more smoothly accept the power generated by new energy, and then improving the new energy consumption level of the regional power grid and promoting the continuous optimization and transformation of the energy structure towards the green and low-carbon direction.

[0059] Of course, it is not necessary for any product implementing the present invention to achieve all the above-mentioned advantages simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0061] Figure 1 It is a schematic flow chart of the method for identifying weak links in the regional power grid accessed by the new energy cluster of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0062] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0063] Please refer to Figure 1 as shown, the present invention is a method for identifying weak links in the regional power grid for new energy cluster access, including the following steps;

[0064] Step S1: Collect the cluster information of new energy and the topological information of the regional power grid, and make a dynamic model of the new energy cluster and the regional power grid;

[0065] Step S2: Add the real-time power generation value of the new energy cluster into the corresponding access points of the dynamic model according to the position of the grid nodes where it is connected, and let the model simulate the real-time power flow state;

[0066] Step S3: Obtain the data information of each node of the power grid through model data analysis, and at the same time form a power generation output curve. Calculate the system response data according to the load curve of the regional power grid to form a database;

[0067] Step S4: Obtain the power grid information through the database information, evaluate the actual operation state of the power grid after the access of new energy, construct a node vulnerability index, and calculate the vulnerability index values of each node and branch of the regional power grid;

[0068] Step S5: Sort the nodes and branches according to the magnitude of the vulnerability index values, set thresholds for the nodes and branches, and select the nodes and branches with vulnerability index values exceeding the set thresholds as the weak links in the regional power grid for new energy cluster access;

[0069] Step S6: Visually display the identified weak links on the topological map of the regional power grid, and at the same time generate a detailed weak link identification report;

[0070] Step S1 includes the following steps:

[0071] Step S11: Collect the information covered by the new energy cluster. For each new energy power generation unit, record its installed capacity, power generation type and geographical location. The installed capacity is clearly marked in standard power units. The power generation type is distinguished into new energy categories such as wind power, photovoltaic power, biomass energy and water energy. The geographical location determines its layout position in the geographical space through coordinate positioning. Collect the operation characteristic parameters of the power generation unit, including the power regulation range, power factor variation range, start-up and shutdown conditions and related characteristics;

[0072] Step S12: Obtain the power grid topology information from the relevant departments responsible for the operation and management of the regional power grid. Sort out each node in the power grid and record the name, number, voltage level, and geographical location information of the node.

[0073] Step S13: According to the information of the new energy cluster and the regional power grid, construct a dynamic model through power system modeling software. During the modeling process, connect each new energy generation unit to the corresponding power grid node, build the connection architecture between each node and branch, set the electrical parameters for the transformers and reactors in the model according to the component parameters, set the governor model and excitation system model for the generators according to the characteristics of different generation units, and at the same time configure the dynamic characteristic models for various loads.

[0074] Step S2 includes the following steps:

[0075] Step S21: Deploy power monitoring devices with communication functions at the new energy power generation site to obtain the power generation values of each new energy generation unit. Transmit the real-time power generation values to the data processing center through the communication network. The data processing center adds the real-time power generation values to the corresponding access points of the dynamic model according to the pre-set relationship that accurately corresponds to the power grid nodes, and removes abnormal data in a timely manner.

[0076] Step S22: Set the boundary conditions for calculating the current load situation and bus voltage reference value of each node according to the actual operating conditions of the current power grid. Through the iterative calculation process, solve the key variables such as the voltage amplitude, phase angle of each node in the power system, and the power of each branch. The iterative calculation formula is as follows:

[0077]

[0078] Where Δθ is the column vector of the correction amount of the node phase angle, and ΔV is the column vector of the correction amount of the node voltage amplitude; ΔP and ΔQ are the column vectors of the active power imbalance and reactive power imbalance respectively; k represents the number of iterations; R-1 is the inverse matrix of the Jacobian matrix R; simulate the power flow state in the regional power grid under the real-time power generation situation of the new energy cluster.

[0079] Step S3 includes the following steps:

[0080] Step S31: From the results simulated and output by the dynamic model, the system extracts the multi-dimensional data information of each node in the power grid. For the voltage data, record the voltage amplitude and phase angle of each node, and analyze the voltage fluctuation situation of the node at different times. For the current data, obtain the magnitude and direction of the injected current of each node, and combine the node voltage information to analyze the power flow characteristics and load level of the node. In terms of power data, calculate and record the active power and reactive power of each node, and analyze the trend of the change in power magnitude.

[0081] Step S32: According to the data of the real-time power generation values of each power generation unit in the new energy cluster changing with time, using data processing software, with time as the horizontal axis and power generation power as the vertical axis, and in accordance with the time scale and power unit, plot the power generation output curves of each power generation unit, integrate the output curves of all power generation units in the same coordinate system, and distinguish different types of new energy power generation curves by means of identification;

[0082] Step S33: Combine with the load curve of the regional power grid, and use ATP-EMTP to analyze the changes in the voltage of each node at the moment when preset fault scenarios such as branch short circuits and generator tripping occur and in the subsequent short period of time, covering the voltage drop amplitude and recovery time, to evaluate the transient voltage stability of the power grid;

[0083] Step S34: Integrate the extracted node data information, power generation output curve data, and the calculated system response data, select a database management system to establish a database, and in the database, classify and store according to data types and time series, and set up an indexing mechanism for data query, retrieval, and analysis operations.

[0084] Step S4 includes the following steps:

[0085] Step S41: Retrieve relevant data from the database to comprehensively evaluate the actual operating state of the power grid after the access of new energy. In the voltage stability evaluation link, observe whether the voltage of each node is within the operating range, count the number of times, duration, and over-limit amplitude of voltage over-limit, and judge the overall voltage stability level of the power grid; for the power balance situation, compare the power generation power injection and load power consumption of each node, check whether there is a power deficit or surplus phenomenon, and whether the power transmission in the power grid is smooth, and pay attention to whether there are problems such as branch overload and power congestion; in the analysis of the fault response ability, by checking the recovery time and fault impact range indicators of the power grid under various fault conditions in the system response data;

[0086] Step S42: Introduce the voltage deviation rate index, and measure the voltage stability of the node by calculating the deviation degree between the actual voltage and the rated voltage of each node. The calculation formula is as follows:

[0087]

[0088] Where D is the voltage deviation rate, V is the actual voltage of the node, and VN is the rated voltage of the node. The larger this index value is, the farther the node voltage deviates from the rated value, the worse the voltage stability, and the weaker the node;

[0089] Set the power transmission margin index, and evaluate its power transmission ability by calculating the remaining margin of the node from the power transmission limit in the current operating state. The calculation formula is as follows:

[0090]

[0091] In the formula, S is the power transfer margin, P is the active power actually transmitted by the node currently, and Pmax is the maximum active power that the node can allow to transmit under the current operating conditions; the smaller the power transfer margin, the more likely the node is to have problems in power transfer and the higher the vulnerability.

[0092] Construct a short-circuit current ratio index, calculate the ratio of the short-circuit current of the node to the rated current. The short-circuit current ratio is the degree of current impact when a short-circuit fault occurs at the node. The calculation formula of the short-circuit current ratio is as follows:

[0093]

[0094] Where L is the current short-circuit ratio, ISC is the effective value of the short-circuit current when a short-circuit fault occurs at the node, and IN is the effective value of the rated current of the node. The larger the short-circuit current ratio, the greater the short-circuit current stress on the electrical equipment of the node, the higher the fault risk, and the weaker the node.

[0095] Reasonably weight and combine the above indicators to form a comprehensive indicator that can comprehensively reflect the vulnerability of the node. The calculation formula is as follows:

[0096] Z = w1×D + w2×S + w3×L;

[0097] Where Z is the comprehensive vulnerability index of the node, and w1, w2, and w3 are the weights corresponding to each index respectively

[0098]

[0099] Step S43: Set the branch power flow overload rate index, and measure the power transfer state of the branch by calculating the ratio of the power actually transmitted by the branch to the rated transmission capacity. The calculation formula is as follows:

[0100]

[0101] Where C is the branch power flow overload rate, P is the active power actually transmitted by the branch currently, and PN represents the rated active power transmission capacity of the branch; when this ratio exceeds 100%, the branch is in an overload state. The higher the overload rate, the more likely the branch is to cause faults due to problems such as overheating, and the higher the vulnerability; even if it is not overloaded, a higher overload rate also means that the branch has a smaller margin in power transfer and weaker ability to cope with emergencies.

[0102] Construct an index for the impact degree of branch faults, and evaluate its vulnerability by analyzing the impact degree on the overall operation index of the power grid when a branch fault occurs. Use the change amount of relevant indicators after the fault to quantitatively represent the impact degree of the fault. The calculation method is as follows:

[0103] G = ΔP = Pb - Pa;

[0104] Where G is the impact degree of branch fault, Pb represents the total active power of the system when the branch is operating normally, and Pa is the total active power of the system after the branch fails and is disconnected; by quantifying the impact of branch faults on the operation of the power grid, the greater the impact degree, the higher the importance and vulnerability of the branch in the power grid, and the greater the harm to the power grid once a fault occurs;

[0105] According to actual needs, the above branch indicators are appropriately weighted to form a comprehensive index of branch vulnerability. The calculation formula is as follows:

[0106] R = w4 × C + w5 × G;

[0107] Where R is the comprehensive index of branch vulnerability, and w4 and w5 are the weight coefficients corresponding to each index respectively.

[0108] Step S5 includes the following steps:

[0109] Step S51: Using the sorting function built into the database management system, according to the magnitude of the calculated vulnerability index values, the nodes and branches are sorted in descending order respectively, and the weak degree of different parts of the power grid is arranged from high to low;

[0110] Step S52: For the comprehensive index of node vulnerability, when the index value is greater than a specific value, it is determined that the node belongs to the weak link; for the comprehensive index of branch vulnerability, similarly, according to the actual situation, when the index value is greater than the corresponding value, it is determined that the branch is the weak link;

[0111] Step S53: According to the set threshold, from the sorted lists of nodes and branches, the nodes and branches with vulnerability index values exceeding the corresponding threshold are screened out. These screened and determined nodes and branches are the weak links of the power grid in the area where the new energy cluster is connected. The selected weak links are recorded in detail, including name, number, location, and the corresponding vulnerability index value content, to form a weak link list.

[0112] In step S6, through the power grid graphic drawing software, on the topology diagram file of the regional power grid, the nodes and branches corresponding to the identified weak links are prominently and intuitively displayed on the topology diagram, marked with eye-catching colors and distinguished by special icons, so that grid operation and maintenance personnel, planning personnel, and relevant professionals can distinguish the specific locations of the weak links and their distributions in the power grid when viewing the topology diagram. At the same time, a mouse hover tooltip information interaction function is set. When the mouse moves to the weak link mark, the detailed information of the weak link is automatically displayed, facilitating the staff to further view and deeply analyze the specific situation of the weak link, and improving the convenience and intuitiveness of information acquisition.

[0113] According to the drawn topological graph file, generate a weak link identification report, introduce the basic situation of the regional power grid, including the grid coverage, voltage level structure, main substations and transmission line elements, and describe the overall situation of the new energy cluster, list all the identified weak links. For each weak link, explain its location and the corresponding vulnerability index value respectively. At the same time, combined with the power grid operation principle and the results of previous data analysis, analyze the reasons for its weakness, so that readers can comprehensively understand the specific situation and formation reasons of each weak link; for the identified weak links, evaluate the risks brought to the operation of the regional power grid, analyze from multiple dimensions such as the risk of power outage accidents, the decline of power grid voltage quality, and the impact degree on the power grid power supply reliability and power quality, and describe them in a quantitative way, so that relevant personnel can clearly and intuitively recognize the severity of the potential hazards of weak links, providing a key basis for formulating subsequent countermeasures.

[0114] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not elaborate on all the details, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for identifying weak links in power grids in areas where new energy clusters are connected, characterized by: The steps include: Step S1: Collecting cluster information of new energy and topological information of regional power grid, and making dynamic models of new energy cluster and regional power grid; Step S2: Add the real-time power generation value of the new energy cluster information to the corresponding access point of the dynamic model according to the location of the connected grid node, so that the model can simulate the real-time power flow state; Step S3: Obtain data information of each node of the power grid through dynamic model data analysis, and form a power generation output curve at the same time, calculate system response data according to the load curve of the regional power grid, and form a database; Step S4: Obtain power grid information through database information, evaluate the actual operation status of the power grid after the access of new energy, construct node weakness index, and calculate the vulnerability index value of each node and branch of the regional power grid; Step S5: Sort the nodes and branches according to the value of the vulnerability index, set thresholds for the nodes and branches, and select the nodes and branches whose vulnerability index values ​​exceed the set thresholds as the weak links of the regional power grid for the new energy cluster to access; Step S6: Visually display the identified weak links on the topological map of the regional power grid, and generate a detailed weak link identification report.

2. The method for identifying weak links in the power grid for access to a new energy cluster according to claim 1 is characterized in that: In step S1, making a dynamic model of the new energy cluster and the regional power grid includes the following steps: Step S11: Collect information covered by the new energy cluster. For each new energy power generation unit, record its installed capacity, power generation type and geographical location, and collect operating characteristic parameters of the power generation unit, including power adjustment range, power factor variation range, start-up and shutdown conditions and related characteristics; Step S12: Obtain grid topology information from relevant departments of regional grid operation and management, sort out various nodes in the grid, and record the name, number, voltage level and geographical location information of the nodes; Step S13: Based on the information of the new energy cluster and the regional power grid, a dynamic model is constructed through the power system modeling software. During the modeling process, each new energy power generation unit is connected to the corresponding power grid node, and a connection structure is built between each node and the branch. The electrical parameters are set for the transformer and reactor equipment in the model according to the component parameters, and the generator speed regulator model and excitation system model are set according to the characteristics of different power generation units. At the same time, dynamic characteristic models are configured for various types of loads.

3. The method for identifying weak links in the power grid for access to a new energy cluster according to claim 1 is characterized in that: In step S2, the model simulates the real-time power flow state, including the following steps: Step S21: deploy power monitoring equipment with communication function at the renewable energy power generation site, obtain the power generation value of each renewable energy power generation unit, and transmit the real-time power generation value to the data processing center through the communication network. The data processing center adds the real-time power generation value to the corresponding access point of the dynamic model according to the pre-set relationship corresponding to the grid node; Step S22: According to the actual operation condition of the current power grid, the current load condition of each node and the bus voltage reference value calculation boundary conditions are set, and through the iterative calculation process, the voltage amplitude, phase angle of each node and the power of each branch of the power system are solved to simulate the power flow state in the regional power grid under the real-time power generation condition of the new energy cluster. The iterative calculation formula is as follows: Where Δθ is the correction column vector of the node phase angle, ΔV is the correction column vector of the node voltage amplitude; ΔP and ΔQ are the column vectors of active power unbalance and reactive power unbalance, respectively; k represents the number of iterations; R-1 is the inverse matrix of the Jacobian matrix R.

4. The method for identifying weak links in power grids for access to new energy clusters according to claim 1 is characterized in that: In step S3, calculating the system response data according to the load curve of the regional power grid to form a database includes the following steps: Step S31: From the results of the dynamic model simulation output, the system extracts multi-dimensional data information of each node in the power grid. For voltage data, the voltage amplitude and phase angle of each node are recorded, and the fluctuation of node voltage at different times is analyzed. For current data, the magnitude and direction of the injected current of each node are obtained. Combined with the node voltage information, the power flow characteristics and load level of the node are analyzed. For power data, the active power and reactive power of each node are calculated and recorded, and the trend of power size change is analyzed. Step S32: Based on the data of the real-time power generation value of each power generation unit of the new energy cluster changing with time, the data processing software is used to draw the power generation output curve of each power generation unit according to the time scale and power unit, with time as the horizontal axis and power generation as the vertical axis, and the output curves of all power generation units are integrated in the same coordinate system, and different types of new energy power generation curves are distinguished by identification; Step S33: Combined with the load curve of the regional power grid, ATP-EMTP is used to analyze the voltage changes of each node at the moment when the preset fault scenario of branch short circuit and generator tripping occurs and in the short period of time thereafter, including the voltage drop amplitude and recovery time, to evaluate the transient voltage stability of the power grid; Step S34: Integrate the extracted node data information, power generation output curve data and calculated system response data, select a database management system to establish a database, classify and store data in the database according to data type and time series, and set an index mechanism for data query and retrieval.

5. The method for identifying weak links in the power grid for access to a new energy cluster according to claim 1 is characterized in that: In step S4, constructing a node weakness index and calculating the vulnerability index value of each node and branch of the regional power grid includes the following steps: Step S41: Retrieve relevant data from the database, conduct a comprehensive assessment of the actual operating status of the power grid after the access of new energy, and in terms of fault response capability analysis, check the recovery time and fault impact range indicators of the power grid under various fault conditions in the system response data; Step S42: Introduce the voltage deviation rate index, and measure the node voltage stability by calculating the deviation between the actual voltage of each node and the rated voltage. The calculation formula is as follows: Where D is the voltage deviation rate, V is the actual node voltage, and VN is the rated node voltage; Set the power transmission margin index to judge the power transmission capability of the node by calculating the remaining margin from the power transmission limit in the current operating state. The calculation formula is as follows: Where S is the power transmission margin, P is the active power actually transmitted by the node, and Pmax is the maximum active power that the node can be allowed to transmit under the current operating conditions; Construct the short-circuit current ratio index and calculate the ratio of the short-circuit current of the node to the rated current. The short-circuit current ratio is the current impact degree of the node when a short-circuit fault occurs. The calculation formula of the short-circuit current ratio is as follows: Where L is the current short-circuit ratio, ISC is the effective value of the short-circuit current when a short-circuit fault occurs at the node, and IN is the effective value of the rated current of the node; The above indicators are reasonably weighted and combined to form a comprehensive indicator that can fully reflect the weakness of the node. The calculation formula is as follows: Z = w1×D+w2×S+w3×L; Where Z is the comprehensive weakness index of the node, w1, w2 and w3 are the weight coefficients corresponding to each index, and w1+w2+w3=1; Step S43: Set the branch power flow overload rate index, and measure the power transmission state of the branch by calculating the ratio of the actual power transmitted by the branch to the rated transmission capacity. The calculation formula is as follows: Where C is the branch power flow overload rate, P is the active power actually transmitted by the branch, and PN represents the rated active power transmission capacity of the branch; The branch fault impact index is constructed to judge the vulnerability by analyzing the impact of branch faults on the overall operation indicators of the power grid. The change in relevant indicators after the fault is used to quantify the impact of the fault. The calculation method is as follows: G = ΔP = Pb-Pa; Where G is the impact degree of branch fault, Pb is the total active power of the system when the branch is operating normally, and Pa is the total active power of the system after the branch is disconnected due to fault; According to actual needs, the above branch indicators are appropriately weighted to form a comprehensive branch vulnerability index. The calculation formula is as follows: R = w4 × C + w5 × G; Where R is the comprehensive index of branch vulnerability, w4 and w5 are the weight coefficients corresponding to each index.

6. The method for identifying weak links in the power grid for access to a new energy cluster according to claim 1, characterized in that: In step S5, the nodes and branches exceeding the set threshold are used as weak links for the new energy cluster to access the regional power grid, including the following steps: Step S51: using the sorting function of the database management system, the nodes and branches are sorted in descending order according to the calculated vulnerability index values, and the vulnerability of different parts of the power grid are arranged from high to low; Step S52: For the node weakness comprehensive index, when the index value is greater than a specific value, the node is considered to be a weak link; for the branch vulnerability comprehensive index, when the index value is greater than a corresponding value, the branch is considered to be a weak link according to the actual situation; Step S53: According to the set threshold, the nodes and branches whose vulnerability index values ​​exceed the corresponding threshold are screened out from the list of sorted nodes and branches. These screened nodes and branches are the weak links of the new energy cluster access regional power grid. The selected weak links are recorded in detail, including the name, number, location and corresponding vulnerability index value content, to form a list of weak links.

7. The method for identifying weak links in the power grid for access to a new energy cluster according to claim 1, characterized in that: In the step S6, the nodes and branches corresponding to the identified weak links are highlighted and intuitively displayed on the topology map of the regional power grid using the power grid graphics drawing software; Based on the drawn topology map file, a weak link identification report is generated to introduce the basic situation of the regional power grid.

Images