Medium-voltage distribution network power supply reliability assessment method, electronic equipment and medium

Abstract

The invention discloses a medium-voltage power distribution network power supply reliability evaluation method, electronic equipment and a medium, and the method comprises the steps: numbering protection equipment of a power distribution network through a topology search algorithm based on a coding rule; generating normal power flow distribution during normal operation of the medium-voltage power distribution network based on a power flow calculation method; traversing contact points in the evaluation area, calculating load-carrying transfer power of the contact points according to normal power flow distribution, and recording serial numbers of associated protection equipment; enumerating an off-line element in the evaluation area, if an associated contact point and an associated node exist in the downstream influence range of the off-line element, constructing a protection equipment set related to the associated contact point based on the associated protection equipment number, and if protection equipment located in the downstream influence range of the off-line element exists in the protection equipment set, constructing a protection equipment set related to the associated contact point based on the associated protection equipment number; and if yes, setting the power of the feeder line section where the protection equipment with the minimum number is located as the transfer power required by the shutdown feeder line. According to the method, the transfer capability of the contact nodes can be formed at one time, and the calculation efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of power distribution network reliability technology, specifically relating to a method for assessing the reliability of medium-voltage power distribution networks, electronic equipment, and media. Background Technology

[0002] A distribution network refers to a power grid that receives electrical energy from the transmission network or regional power plants and distributes it locally or in stages according to voltage to various users through distribution facilities.

[0003] Power supply reliability is a technical and economic indicator that measures the power grid's ability to continuously supply power to users, reflecting the grid's technology, equipment level, and enterprise management level. With the gradual improvement of the main power grid structure, the reliability of the distribution network has gradually become a major bottleneck restricting the improvement of user power supply reliability. In actual distribution networks, medium-voltage lines are used to transmit electrical energy from substations to various areas, and there are situations involving load distribution and distributed power source access. Because power supply reliability assessment can effectively guide the planning, construction, operation, and maintenance of medium-voltage distribution networks, improve power supply reliability, and increase the investment efficiency of the power grid, more and more power supply companies are carrying out or planning to carry out this work.

[0004] As users' requirements for power supply reliability continue to increase, quantitative reliability calculation and analysis are playing an increasingly important role in power supply reliability management. Reliability assessments of medium-voltage distribution networks that consider multiple influencing factors are more realistic. In actual distribution networks, when a component fails, switching some loads to other lines via tie lines requires careful consideration of equipment capacity limitations. However, directly using power flow simulation for reliability assessment under each system failure state during distribution network planning suffers from problems such as unreliable convergence of power flow iterative algorithms, inefficient and repetitive topology searches in outage states, and the impracticality of power flow-based reliability assessment calculations. Summary of the Invention

[0005] The purpose of this invention is to provide a medium-voltage distribution network power supply reliability assessment method that can significantly improve calculation efficiency by using a method for calculating the transfer capacity of distribution network feeder tie points based on power flow distribution.

[0006] To achieve the above objectives, this invention proposes a method for assessing the reliability of medium-voltage distribution network power supply, comprising: numbering the protection devices of the distribution network based on coding rules using a topology search algorithm, wherein the coding rule is that the upstream protection device number is less than the downstream protection device number; generating the normal power flow distribution during normal operation of the medium-voltage distribution network based on a power flow calculation method; traversing the tie points within the assessment area, calculating the transfer power that the tie point can carry based on the normal power flow distribution for each tie point, and recording the protection device numbers between each tie point and the power source point of the line where the tie point is located to obtain the associated protection device numbers; enumerating the out-of-service elements within the assessment area, if there are associated tie points and associated nodes in the downstream influence range of the out-of-service element, constructing a set of protection devices related to the associated tie point based on the associated protection device numbers; if there are protection devices in the protection device set located in the downstream influence range of the out-of-service element, setting the power of the feeder segment where the protection device with the smallest number is located as the transfer power required by the out-of-service feeder.

[0007] In one optional implementation, the normal power flow distribution during normal operation of a medium-voltage distribution network is generated based on a power flow calculation method. Specifically, this includes: taking the concentrated load at the end of the medium-voltage line as the starting point for calculation, sequentially calculating the end power and beginning power of each feeder segment towards the power source; traversing other loads and distributed power sources to calculate the end power and beginning power of each feeder segment; and accumulating all end power and all beginning power to generate the normal power flow distribution.

[0008] In one optional implementation, taking the concentrated load at the end of the medium-voltage line as the starting point, the power at the end and the power at the beginning of each feeder segment are calculated sequentially towards the power source. Specifically, this includes calculating the power loss of the admittance branch at the end of the feeder segment. In the formula, U0 is the power loss of the admittance branch at the end of the feeder segment; G is the conductance of the admittance branch of the feeder segment; U2 is the voltage at the end of the feeder segment, U2 = U0. N U N B is the effective value of the rated voltage; B is the susceptance of the feeder segment admittance branch; the complex power of the concentrated load at the end of the feeder segment is superimposed with the power loss of the feeder segment end admittance branch to obtain the end power: In the formula, For end power; The complex power of the concentrated load at the end of the feeder section; The power loss of the admittance branch at the end of the feeder section; In the formula, P2 and Q2 are the active and reactive power of the centralized load or distributed power source at the end, respectively; based on the loss of the feeder segment impedance and the power at the end, the preliminary starting power of the feeder segment is calculated: In the formula, Z is the branch impedance of the feeder section; U1 = U2 = UN U2 is the voltage at the end of the feeder segment; S2′ is the terminal power; The modulus; calculate the loss at the admittance of the feeder segment: The starting power is calculated based on the loss of the feeder segment's starting admittance and the initial starting power of the feeder segment:

[0009] In one alternative implementation, the expression for the power transfer capacity of the connection point is: In the formula, S l,max Rated apparent power; S l B represents the apparent power of the load carried by feeder segment l during normal network operation. tie,i U is the set of feeder segment numbers between connection point i and power point; N I represents the effective value of the rated voltage of the feeder section. l,max is the maximum allowable current for the feeder segment, and l is the feeder segment number.

[0010] In an optional implementation, the medium-voltage distribution network power supply reliability assessment method further includes: calculating a transferability coefficient based on the power to be transferred from the out-of-service feeder and the transferability capacity of the tie point, and correcting the expected outage time of the associated node based on the transferability coefficient. Specifically, this includes: obtaining the number of independent transferable areas and the number of associated tie points downstream of the out-of-service component, wherein the independent transferable area refers to a power supply area downstream of the component that has associated tie points but is no longer interconnected after the component is out of service; calculating the transferability coefficient based on the number of independent transferable areas and the number of associated tie points, the power to be transferred from the out-of-service feeder and the transferability capacity of the tie point; and correcting the expected outage time of the associated node within the independent transferable area based on the transferability coefficient.

[0011] In an optional implementation, if both the number of independent transferable areas and the number of associated contact points are one, then the expression for the transferability coefficient is: In the formula, S tie,m The connection point can carry transferred power; S k,m Power needs to be transferred to the outage feeder; the expression for the expected outage time of the associated node is: u LP =(1-ε m )λ k t k +ε m λ k t df,m In the formula, λ k t represents the average downtime rate of component k; k t represents the average downtime repair time for component k that is out of service.df,m It is the sum of the location and isolation time of the shutdown of the shutdown component k and the switching time of the associated contact point m.

[0012] In one optional implementation, if the number of the independent transferable areas is one, the number of the associated contact points is multiple, and if there is a protective device separation between two of the associated contact points, then the expression for the transferability coefficient is: In the formula: and These are the power transfer capabilities of connection points m1 and m2, respectively; if there is no protective equipment separation between the two associated connection points, then the expression for the power transfer capability coefficient is:

[0013] In an optional implementation, if both the number of independently transferable areas and the number of associated contact points are multiple, and if there is a protective device segmentation between two of the associated contact points, then the expression for the transferability coefficient is: In the formula, and These are the transferable power capacities of connection points m1 and m2, respectively. and The power transfer required by the out-of-service feeders downstream of the out-of-service component k from connection points m1 and m2 is respectively; if there is no protection device separation between the two associated connection points, the expression for the transfer coefficient is:

[0014] The present invention also proposes an electronic device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform any of the medium-voltage power distribution network power supply reliability assessment methods described herein.

[0015] The present invention also proposes a medium storing a computer program, which, when executed by a processor, implements any of the medium-voltage power distribution network power supply reliability assessment methods described in the present invention.

[0016] The beneficial effects of this invention are as follows: the algorithm complexity is independent of the number of out-of-service components, and the transferable capacity of the interconnection node can be formed at one time. It can be directly used when the components are out of service, which greatly improves the calculation efficiency. Attached Figure Description

[0017] Figure 1 A flowchart of a medium-voltage power distribution network reliability assessment method provided in an embodiment of the present invention;

[0018] Figure 2 A load transfer model diagram between feeders during component outages in the medium-voltage distribution network power supply reliability assessment method provided for the implementation of this invention;

[0019] Figure 3 A simplified power flow calculation diagram of the medium-voltage distribution network power supply reliability assessment method provided in this embodiment of the invention;

[0020] Figure 4 A flowchart of a medium-voltage power distribution network reliability assessment method provided in another embodiment of the present invention;

[0021] Figure 5 A diagram illustrating a single independent power transfer area and a single connection point in the medium-voltage distribution network power supply reliability assessment method provided in this embodiment of the invention.

[0022] Figure 6 A diagram illustrating a single independent power transfer area and multiple connection points in the medium-voltage distribution network power supply reliability assessment method provided for the implementation of this invention.

[0023] Figure 7 A diagram illustrating multiple independent power transfer areas and multiple connection points in the medium-voltage distribution network power supply reliability assessment method provided in this embodiment of the invention.

[0024] Figure 8 The distribution network topology diagram is an example of the medium-voltage distribution network power supply reliability assessment method provided in the embodiments of the present invention.

[0025] Figure 9 A power flow distribution diagram illustrating an example of a medium-voltage distribution network power supply reliability assessment method provided in an embodiment of the present invention;

[0026] Figure 10 A schematic diagram of the outage state of a branch (1) of an example of the medium-voltage distribution network power supply reliability assessment method provided for the implementation of the present invention. Attached image description:

[0028] 10. Out-of-service feeder; 11. First feeder section; 12. Second feeder section; 13. Third feeder section; 14. Fourth feeder section; 1001. Out-of-service component; 1002. First associated connection point; 1003. Second associated connection point; 1004. Isolable protection device; 20. Connection feeder; 21. First connection feeder; 22. Second connection feeder; 30. Connection switch; 41. First load; 42. Second load; 43. Third load; 50. Power supply point; A. First independent transferable area; B. Second independent transferable area; C. Third independent transferable area; D. Fourth independent transferable area. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] like Figure 1 and Figure 2 As shown in the embodiments of the present invention, in one aspect, a method for assessing the reliability of power supply in a medium-voltage distribution network is provided, comprising the following steps:

[0031] Step S101: Based on the coding rules, the protection devices of the distribution network are numbered using a topology search algorithm. The coding rule is that the upstream protection device number is less than the downstream protection device number.

[0032] Step S103: Generate the normal power flow distribution during normal operation of the medium-voltage distribution network based on the power flow calculation method.

[0033] Step S105: Traverse all connection points within the evaluation area. For each connection point, calculate the transfer power that the connection point can carry based on the normal power flow distribution, and record the protection device number between each connection point and the power supply point 50 of the line where the connection point is located, to obtain the associated protection device number.

[0034] Step S107: Enumerate the out-of-service components 1001 in the evaluation area. If there are associated connection points and associated nodes in the downstream influence range of the out-of-service component 1001, construct a set of protection devices related to the associated connection points based on the associated protection device numbers. If there are protection devices in the protection device set that are located in the downstream influence range of the out-of-service component 1001, set the power of the feeder segment where the protection device with the smallest number is located as the power that the out-of-service feeder 10 needs to transfer.

[0035] In this embodiment, the feeder load transfer model used for calculation and analysis is as follows: Figure 2 As shown, and defined: Interconnecting feeder 20 refers to the feeder in the distribution network that provides temporary power to the transferred loads; the component that goes out of service due to a fault is the out-of-service component 1001, and the out-of-service feeder 10 refers to the feeder in the distribution network where the component goes out of service. There is an interconnecting switch 30 between the out-of-service feeder 10 and the interconnecting feeder 20. Normal power flow distribution during normal operation refers to the steady-state distribution of power flow in the power grid under conditions of no faults, no equipment maintenance, and no outages. This state is the benchmark operating condition for power grid reliability assessment and is a prerequisite for fault analysis and power transfer scheme calculations.

[0036] Topology search algorithms such as Depth-First Search (DFS) or Breadth-First Search (BFS) can be used to traverse each protection device starting from the power source point 50 of the distribution network and following the direction of power transmission. During the traversal, the coding rules are strictly followed, meaning the upstream protection device number is lower than the downstream protection device number. This numbering method clearly reflects the upstream and downstream relationships between protection devices in the distribution network, providing an ordered and intuitive basic data structure for subsequent analysis and calculations. For example, starting with the substation outgoing line switch numbered 1, the numbers are sequentially increased downstream for sectionalizing switches, branch switches, and other devices, thus constructing a complete protection device numbering system.

[0037] By numbering the protected devices using a topology search algorithm based on specific coding rules, a clear upstream and downstream relationship between the devices is established. This enables the rapid location and processing of relevant device information in subsequent analysis and calculations, improving the efficiency and accuracy of data processing and avoiding calculation errors and analysis difficulties caused by data chaos.

[0038] Based on the network topology, injected power at each node, and line parameters of the distribution network, power flow calculations are performed on the voltage amplitude and phase angle at each node and the power distribution of each line. Through power flow calculations, a comprehensive understanding of the power flow in the distribution network under normal operating conditions can be obtained, along with the operating parameters of each component. This provides crucial foundational data for subsequent assessments of power supply reliability and serves as a reference benchmark for analyzing the network's operational status after a fault.

[0039] A tie point primarily refers to the connection point used for interconnection between different power supply lines and distribution areas. When a line or area experiences a fault and outage, the tie point allows for load transfer, thereby improving power supply reliability. In a sense, a tie point is a node with a specific function (achieving power connection and transfer), but the concept of a node is broader, including other types of nodes such as power supply nodes and load nodes. Tie points mainly focus on connection points related to the interconnection function of the power supply network. Calculating the transfer capacity of a tie point requires comprehensive consideration of factors such as the capacity limitations of the lines at both ends of the tie point, node voltage constraints, and system stability.

[0040] In the specific calculations, based on the normal power flow distribution, the maximum transfer power that the tie point can withstand is determined by adjusting the power distribution of the lines at both ends of the tie point while meeting various constraints. Simultaneously, the protection device numbers between each tie point and the power source point 50 of the line where the tie point is located are recorded, resulting in associated protection device numbers. These associated protection device numbers clearly define the connection relationship between the protection devices of the tie point and the power source point 50, providing crucial information for subsequent analysis of the power transfer path during faults.

[0041] The mainstream methods for power supply reliability assessment are Failure Mode and Effects Analysis (FMEA) and the least path method. Both require enumerating the outage states of components for evaluation and analysis, which generally leads to wasted computational resources due to repetitive topology analysis. This invention proposes a method for calculating the transferable power capacity of distribution network feeder tie points based on power flow distribution. The algorithm complexity is independent of the number of outage components (1001), and it can generate the transferable power capacity of tie points in one step. This capacity can be directly retrieved when enumerating outage components, significantly improving computational efficiency.

[0042] When a component fails, its downstream impact range is first determined, i.e., the area where power is lost due to the component's failure. If there are associated tie points and nodes within the downstream impact range of the failed component 1001, a set of protection devices related to the associated tie points is constructed based on the associated protection device numbers. This set of protection devices includes all protection devices along the path from power source 50 to the tie point. Then, it is checked whether any protection devices in the set are located within the downstream impact range of the failed component 1001. If so, the power of the feeder segment containing the protection device with the lowest number is set as the power that needs to be transferred through the failed feeder 10. This is because the protection device with the lowest number is closer to power source 50, and the power of its feeder segment can more accurately reflect the amount of power that needs to be transferred through the tie point, thus providing crucial data support for the subsequent power restoration strategy.

[0043] When calculating the transfer power capacity of the tie point, multiple constraints are comprehensively considered to ensure that the calculation results meet actual operational requirements, avoiding grid operation risks caused by unreasonable determination of transfer power. Simultaneously, by constructing a set of protection devices based on their associated protection device numbers and determining the transfer power required for outage feeder 10 according to specific rules, the power that needs to be transferred after a fault can be accurately identified. This provides crucial data for formulating reasonable power restoration strategies, helping to improve the recovery efficiency and power supply reliability after grid faults.

[0044] Accurate power flow simulation calculations suffer from challenges such as difficulty in guaranteeing convergence for each calculation, high data volume requirements, and stringent data quality requirements. For actual distribution networks, the accuracy of the basic data needed for power supply reliability assessment (such as reliability parameters, load shedding methods, and distribution transformer load sizes) is generally low, resulting in approximate estimates. Furthermore, the requirements for basic data are not necessarily stringent for comparing and selecting distribution network planning and renovation schemes, as scheme selection relies more on the relative rather than absolute values ​​of reliability assessment results under the same data conditions. Therefore, to balance accuracy and efficiency, a simplified power flow calculation is adopted. This involves continuously accumulating load data from the end of medium-voltage lines to upstream equipment (including losses based on rated voltage) until reaching the power source side (such as substations) to generate an approximate power flow distribution.

[0045] For actual distribution networks, the accuracy of the basic data required for power supply reliability assessment is generally low, and the calculation results are usually approximate estimates. Accurate power flow simulation uses iterative algorithms, which suffer from problems such as unreliable convergence and low computational efficiency in power flow-based reliability assessment. Furthermore, the requirements for basic data are not necessarily stringent when comparing and selecting distribution network planning and renovation schemes, because under the same basic data conditions, scheme selection relies more on the relative values ​​of reliability assessment results than their absolute values. Based on the need to adjust power supply reliability assessment results considering transfer capacity, the simplified power flow method proposed in this invention satisfies the accuracy requirements of power supply reliability assessment considering transfer capacity while also taking into account computational accuracy, convergence, and efficiency.

[0046] Further, step S103, generating the normal power flow distribution during normal operation of the medium-voltage distribution network based on the power flow calculation method, specifically includes the following steps:

[0047] Step S1031: Taking the concentrated load at the end of the medium-voltage line as the starting point of the calculation, calculate the end power and start power of each feeder segment sequentially towards the power source.

[0048] Step S1033: Traverse other loads and distributed power sources to calculate the end power and beginning power of each feeder segment;

[0049] Step S1035: Accumulate all end power and all beginning power to generate a normal power flow distribution.

[0050] In this embodiment, the calculation starts from the concentrated load at the end of the medium-voltage line and proceeds towards the power source (step S1031), following the physical logic of actual power transmission feedback from the load end to the power source end. This clear calculation sequence reduces redundancy and confusion in the calculation process, avoids repeated calculations or errors caused by unclear calculation paths, and can quickly and orderly complete the power calculation of each feeder segment, greatly improving the efficiency of power flow calculation, which is especially suitable for complex and large-scale medium-voltage distribution network systems.

[0051] In step S1033, the power of the feeder segment is calculated by traversing other loads and distributed generation sources, fully considering the actual situation of multiple energy accesses and load distribution in the distribution network. The access of distributed generation sources changes the unidirectional power flow characteristics of the traditional distribution network. This step can accurately reflect the impact of distributed generation sources on power flow distribution, while also taking into account the power demands of different types of loads, making the calculation results closer to the actual operating state of the power grid, and effectively improving the comprehensiveness and accuracy of power flow distribution calculation.

[0052] Step S1035 accumulates all end-point and beginning-point power to generate a normal power flow distribution, which clearly shows the power flow direction, power distribution at each node, and line transmission power of the entire medium-voltage distribution network from an overall perspective. This provides a complete and accurate data foundation for assessing the power grid's operating status, analyzing faults, and evaluating subsequent power supply reliability. It also allows power workers to intuitively understand the overall operation of the power grid and provides strong support for formulating reasonable operation control strategies and reliability improvement measures.

[0053] In this context, voltage drop is ignored (i.e., the voltage phasors at both ends of each feeder segment are the rated voltage). Its effective value is U N Let the complex power of the concentrated load at the end be... (S2′ is) P2 and Q2 are the active and reactive power of the terminal centralized load (or distributed power source), and the feeder segment branch admittance Y = G + jB.

[0054] Furthermore, such as Figure 3 As shown, the outage feeder 10 is divided into a first feeder segment 11, a second feeder segment 12, a third feeder segment 13 and a fourth feeder segment 14. The end of the fourth feeder segment 14 is connected to the third load 43, the end of the third feeder segment 13 is connected to the second load 42, and the end of the second feeder segment 12 is connected to the first load 41.

[0055] Step S1031, taking the concentrated load at the end of the medium-voltage line as the starting point, calculates the end power and beginning power of each feeder segment sequentially towards the power source, specifically including the following steps:

[0056] Step S10311: Calculate the power loss of the admittance branch at the end of the feeder segment:

[0057]

[0058] In the formula, U0 is the power loss of the admittance branch at the end of the feeder section; G is the conductance of the admittance branch of the feeder section, reflecting the active power loss of the line, such as active power loss caused by insulation leakage; U2 is the voltage at the end of the feeder section, U2 = U0. N U N B is the effective value of the rated voltage; B is the susceptance of the feeder section admittance branch, reflecting the reactive power characteristics of the line, such as the reactive power throughput of the line capacitor; active power loss is generated by the conductance G. The susceptance B generates reactive power loss. This reflects the reactive throughput characteristics of capacitors.

[0059] This calculation method accurately considers the active and reactive power losses of the line admittance branch, making the calculation of line power loss more consistent with the actual electrical characteristics of the line, and laying an accurate foundation for subsequent power flow calculation.

[0060] Step S10313: The complex power of the concentrated load at the end of the feeder segment is superimposed with the power loss of the admittance branch at the end of the feeder segment to obtain the end power:

[0061]

[0062] In the formula, For end power; The complex power of the concentrated load at the end of the feeder section; This refers to the power loss of the admittance branch at the end of the feeder section.

[0063]

[0064] In the formula, P2 and Q2 are the active and reactive power of the centralized load at the end or the distributed power source, respectively.

[0065] This superposition operation combines the power demand of the load with the power loss of the line itself, comprehensively reflecting the actual power situation at the end of the feeder segment, ensuring the integrity and accuracy of the end power calculation, and providing reliable input data for subsequent calculation of the beginning power.

[0066] Step S10315: Based on the loss and end power of the feeder segment impedance, calculate the preliminary beginning power of the feeder segment:

[0067]

[0068] In the formula, Z is the branch impedance of the feeder section; U1 = U2 = U N U2 is the voltage at the end of the feeder segment; S2′ is the terminal power; The magnitude of the complex power transferred from the end to the impedance branch.

[0069] This formula takes into account the losses generated by the impedance of the feeder segment during power transmission, so that the calculation of the power at the beginning not only includes the power at the end, but also covers the power changes caused by the line impedance. This further improves the accuracy of power distribution in power flow calculation and can more realistically reflect the power transmission from the end to the beginning in the distribution network.

[0070] Step S10317: Calculate the loss at the beginning admittance of the feeder segment:

[0071]

[0072] Step S10319: Calculate the starting power based on the loss of the feeder segment's starting admittance and the preliminary starting power of the feeder segment:

[0073]

[0074] like Figure 3 As shown, the calculation proceeds step by step from the centralized load 3 to the power source, i.e., the power at the beginning and end of the fourth feeder segment 14 to the first feeder segment 11. Then, the above method is repeated for other centralized loads and distributed power sources, and the calculated power at the beginning and end is accumulated.

[0075] Since the power change of the branch lines after load transfer is small, only the capacity constraint of the main line is considered. When a component is out of service, the load in its transfer area is transferred by the tie feeder 20. After the transfer, the power of the main line of the tie feeder 20 is its normal power plus the total transferred load. Calculate the difference between the rated apparent power of each feeder segment between the tie point and the power source 50 and its normal load apparent power. The minimum value is the transfer power that the tie point of the tie feeder 20 can carry.

[0076] Among them, based on the simplified power flow calculation method to calculate the power flow distribution of the feeders during normal network operation, the expression for the transfer power that the tie point of tie feeder 20 can carry is:

[0077]

[0078]

[0079] In the formula, S l,max Rated apparent power; S l B represents the apparent power of the load carried by feeder segment l during normal network operation. tie,i Let S be the set of feeder segment numbers between connection point i and power source point i. tie,i If the calculation result is negative, then let S... tie,i =0; U N I represents the effective value of the rated voltage of the feeder section. l,max is the maximum allowable current for the feeder segment, and l is the feeder segment number.

[0080] In this embodiment, to calculate the transfer power that connection point i can carry, it is necessary to find the set B of feeder segments from connection point i to the power source point. tie,i For each feeder segment l in the set, first calculate the rated apparent power S of that feeder segment. l,max The apparent power S of the load carried during normal operation l The difference S l,max -S l Then, the minimum of these differences is the transfer power S that connection point i can carry. tie,i This is done because the power transfer is limited to the "weakest" (least remaining capacity) feeder segment on the path from the connection point to the power point 50. Taking the minimum value ensures that none of the feeder segments will be overloaded during power transfer.

[0081] By calculating the transfer power that the tie point can carry, the remaining capacity of each feeder segment between the tie point and the power source 50 is fully considered, and the transfer power that the tie point can carry is accurately determined. This avoids transfer failure due to overload of a single feeder segment and provides a reliable basis for power transfer restoration during power distribution network faults.

[0082] Based on the calculation of rated apparent power, combined with the maximum allowable current and rated voltage of the feeder section, and strictly following the capacity limits of the power grid equipment, it is ensured that each feeder section will not exceed its safe operating power carrying capacity during the power transfer process, thus effectively guaranteeing the safe and stable operation of the distribution network.

[0083] This calculation method comprehensively considers the actual operating load and capacity limitations of feeder segments in the distribution network, making the assessment of the transfer power that the connection point can carry more closely match the actual operation of the power grid. This improves the accuracy of the power supply reliability assessment of the entire medium-voltage distribution network and provides more scientific support for power grid planning, operation and maintenance decisions.

[0084] A simplified power flow calculation method is used to determine the power flow distribution of feeder segments during normal operation. Based on this, the power transfer capacity of tie points is calculated. The calculation process is logically clear and the steps are simple, making it easy for engineering technicians to understand and apply. It can quickly provide key data for the power supply reliability analysis of distribution networks.

[0085] When using power supply reliability assessment methods (generally failure mode consequence analysis), enumerate the element k (1≤k≤N). comp k is the component number that may be out of service, N comp To assess the total number of components that could potentially shut down in the region, if there is a connection point m downstream of the shut-down component 1001k, search for the PD of the connection point. m Set, if PD m There is a protection device located downstream of the out-of-service component 1001. Record the power of the feeder segment where the protection device with the smallest number is located; this is the power S that component k needs to transfer from tie point m when it is out of service. k,m Finally, based on the power S required to be transferred from the out-of-service feeder 10... k,m and the transfer power S that the connection point can carry tie,m Calculate the transferable coefficient ε m .

[0086] Traditional power supply reliability assessment methods generally do not address the issue of power transfer capacity constraints, and their assessment accuracy is not suitable for power grids with high power supply reliability requirements. The proposed method for calculating the distribution network power transfer coefficient and correcting the expected outage time clarifies a power supply reliability assessment correction method that considers power transfer capacity constraints under various component outage conditions. This method boasts high calculation accuracy, simplicity, and strong practicality.

[0087] Furthermore, it can be combined with Figure 4 As shown, the reliability assessment method for medium-voltage distribution networks also includes: calculating the transferability coefficient based on the power required to be transferred from the out-of-service feeder 10 and the transferability capacity of the tie point, and correcting the expected outage time of the associated nodes based on the transferability coefficient. Specifically, this includes the following steps:

[0088] Step S201: Obtain the number of independent transferable areas and the number of associated contact points downstream of the shut-down component 1001. Independent transferable areas refer to the power supply areas downstream of the component that have associated contact points but are no longer connected to each other after the component is shut down.

[0089] Step S203: Calculate the transferability coefficient based on the number of independent transferable areas and the number of associated connection points, the power required to transfer power from out-of-service feeder 10 and the transferable power that the connection points can bear.

[0090] Step S205: For associated nodes within an independent power transfer area, adjust the expected outage time of the associated nodes based on the power transfer coefficient.

[0091] In step S201, an independent transferable power supply area is identified, which is a power supply area that has downstream connection points after the component is shut down but is no longer interconnected. This division method can accurately locate the specific area that needs to be transferred, clarify the scope of the transfer target, avoid confusion in the formulation of transfer strategies caused by ambiguous transfer area definitions, and provide a clear regional basis for the subsequent allocation of transfer power and the correction of power outage time.

[0092] Step S203 calculates the transferability coefficient based on the number of independent transferable areas, the number of associated connection points, the power required for transfer by out-of-service feeder 10, and the transferability capacity of the connection points. This coefficient comprehensively considers the supply and demand relationship of transfer and the distribution of areas and connection points, scientifically quantifies the transferability capacity of the distribution network, and provides key quantitative indicators for judging the feasibility and degree of transfer, making the transferability decision more scientific and reasonable.

[0093] Step S205 corrects the expected outage time of associated nodes within an independent power transferable area based on the power transferability coefficient. Traditional outage time assessments are often static and do not fully consider the impact of power transfer on outage time. Dynamic correction using the power transferability coefficient can more realistically reflect the actual outage duration of associated nodes when power transfer capability is available, greatly improving the accuracy of medium-voltage distribution network power supply reliability assessment and making the assessment results more consistent with actual grid operation.

[0094] The entire process, from regional division and quantification of transfer capacity to outage time correction, forms a complete power supply reliability assessment logic for transfer situations. Based on these more accurate assessment results, power departments can formulate more optimized power restoration strategies, making more efficient use of the transfer capacity of interconnection points when components are out of service, reducing power outage time for users, and thus effectively improving the power supply reliability of the medium-voltage distribution network.

[0095] Based on the number of independent supply areas and contact points downstream of the out-of-service component 1001k, there are three scenarios.

[0096] Among them, such as Figure 5 As shown, if the number of independent transferable areas and the number of associated contact points are both one, that is, there exists a first independent transferable area A, and there is one associated contact point within the first independent transferable area A, namely the first associated contact point 1002, then the expression for the transferability coefficient is:

[0097]

[0098] In the formula, S tie,m The connection point can carry transferred power; S k,m Power needs to be transferred to feeder 10 to prevent it from being shut down;

[0099] The expression for the expected power outage time of the associated node is:

[0100]

[0101] In the formula, λ k The average downtime rate of 1001k components; t k The mean time to repair (MT) for 1001k components that are out of service; t df,m This is the sum of the location and isolation time of the shutdown of component 1001k and the switching time of the associated contact point m.

[0102] Among them, such as Figure 6 As shown, if the number of independently transferable areas is one, i.e., the second independently transferable area B, and the number of associated connection points is multiple, for example, the associated connection points include the first associated connection point 1002 and the second associated connection point 1003, and if there is a protective device (such as a load switch) separating two of the associated connection points, i.e., there is an isolating protective device 1004, then the expression for the transferability coefficient is:

[0103]

[0104] In the formula: and These are the transferable power capacities of connection points m1 and m2, respectively.

[0105] If there is no protective equipment separation between two associated connection points, the expression for the transfer coefficient is:

[0106]

[0107] For associated nodes within the second independent power transfer zone B, the expected value of the outage time for each node caused by the outage component 1001 is corrected. LP Process according to formula (9). Wherein,

[0108] i) It can be further divided into more different sub-independent regions for calculation based on the protection equipment between the associated contact points, but this requires additional topology search and generally has a large computational cost.

[0109] ii) If multiple associated connection points correspond to the same feeder, only the maximum power transfer capacity of such connection points should be retained.

[0110] Among them, such as Figure 7 As shown, if there are multiple independent transferable areas and multiple associated connection points, i.e., two third independent transferable areas C, and if there is a protective device (such as a load switch) separating two of the associated connection points, then the expression for the transferability coefficient is:

[0111]

[0112] In the formula, and These are the transferable power capacities of connection points m1 and m2, respectively. and The power to be transferred from the out-of-service feeder 10 to the downstream of the out-of-service component 1001k from the connection points m1 and m2 is respectively the power to be transferred from the out-of-service feeder 10.

[0113] If there is no protective equipment separation between two associated connection points, the expression for the transfer coefficient is:

[0114]

[0115] For nodes within an independent power transfer area, the expected value of the outage time for each node caused by the outage component 1001k is corrected as follows: LP Process according to formula (9). Wherein,

[0116] i) The transferability coefficient ε can be calculated separately for each independent transfer area. m The expected outage time of each node in each independent power transfer area is corrected separately. LP .

[0117] ii) If the tie lines corresponding to multiple tie points are the same feeder, the maximum transfer power that can be carried should be taken.

[0118] Application Examples

[0119] Distribution network data

[0120] (1) Basic Data

[0121] Distribution network topology such as Figure 8 As shown, only the segments of feeder 10 (numbered in parentheses in the diagram) are considered out of service. The impedance of each segment of all feeders (including feeder 10, first connecting feeder 21, and second connecting feeder 22) is...

[0122] Z = 0.132 + j0.325Ω (ignoring branch admittance), the length of each line segment is 1km, and the maximum allowable current I of each line segment is... l,max All are 610A. The load of each node of the first connecting feeder 21 and the second connecting feeder 22 is 1.75 + j0.875MVA. The load of each node of the out-of-service feeder 10 is shown in Table 1.

[0123] Table 1 Load of each node of the out-of-service feeder 10

[0124] Node number P(MW) Q(MVar) 1 0 0 2 0.5 0.25 3 0.5 0.25 4 1 0.5 5 1 0.5 6 1.5 0.75 7 1.5 0.75 8 1.5 0.75

[0125] (2) Reliability parameters

[0126] The average power outage location and isolation time is 0.1h, the average switching time of tie switch 30 is 0.25h, and other power outage parameters are shown in Table 2.

[0127] Table 2 Equipment Power Outage Parameters

[0128] parameter unit line segment Average downtime rate times / (km·year) 0.056 Average downtime for repair Hour 3.01

[0129] Power flow calculation

[0130] The power flow distribution obtained by the simplified power flow calculation method of this invention is as follows: Figure 9 As shown, the apparent power flowing through the branch start point is next to the arrow, in MVA.

[0131] Contact point transfer rate calculation

[0132] Since only the section of outage feeder 10 is considered out of service, only the transferable power at the connection point on outage feeder 10 is calculated. Each section of the first connection feeder 21 and the second connection feeder 22 is identical; therefore, the rated apparent power of each feeder section is:

[0133]

[0134] For the out-of-service feeder 10, its connecting nodes are nodes 6, 7, and 8. Taking connecting node 6 as an example, connecting node 6 corresponds to the first connecting feeder 21. The power carrying capacity of each feeder segment from the beginning to the end of the first connecting feeder 21 is shown in Table 3. The transferable power of connecting node 6 as a connecting point is the minimum value of "remaining carrying capacity" in Table 1, which is 2.425 MVA.

[0135] Table 3 Power Capacity of First Connecting Feeder 21

[0136]

[0137] Note: Remaining load capacity = Rated power - Apparent power at the beginning.

[0138] Similarly, the transferable power of both connection nodes 7 and 8 as connection points is 0.191 MVA.

[0139] Traditional power supply reliability assessment that does not consider power transfer capacity

[0140] (1) Considering only the outage of a section of feeder 10, the failure mode consequence analysis method is used to obtain the impact of each node after the outage of each line, as shown in Table 4.

[0141] Table 4 Failure Mode and Effects Analysis Table

[0142]

[0143] Note: "Repair" refers to the repair time that node y will experience after branch (x) is out of service;

[0144] "Transfer supply" refers to the time that node y will experience after branch line (x) is out of service, including power outage location, isolation time, and switching time of the contact switch 30.

[0145] "Upstream" refers to the time when node y will sense the power outage location and isolation after branch (x) is shut down, that is, when power is restored from the original upstream power source;

[0146] "Repair" metric = Average downtime rate * Average downtime repair time;

[0147] "Power Transfer" indicator = Average Outage Rate * (Average Outage Location and Isolation Time + Average Interchange Switch Switch Switching Time 30)

[0148] "Upstream" indicator = Average outage rate * Average outage location and isolation time;

[0149] (2) Without considering the constraints of power transfer capacity, the impact of the shutdown of each line segment on the expected power outage time of each node is shown in the table below. The row containing "Total" in the table represents the expected power outage time u of each node. LP .

[0150] Table 5. Power supply reliability assessment results without considering power transfer constraints (unit: h)

[0151]

[0152] Adjustments to the available supply factor and expected outage time

[0153] As shown in Table 4, after the outages of branches (1), (2), (3), (4), (5), and (7), there are instances of load transfer to downstream nodes. Taking the outage of branch (1) as an example, its fourth independent transferable area D includes associated nodes 2, 3, 4, 5, 6, 7, and 8, and its associated connection points include 6, 7, and 8. Figure 10 As shown.

[0154] (1) Calculation of power supply required

[0155] After branch (1) is shut down, the protection device with the smallest downstream number is located in branch (2), so the power to be transferred is the apparent power of branch (2) of 8.729 MVA.

[0156] (2) Calculation of available power

[0157] There is a protective device (load switch) separating connection points 7 from 6 and 8; there is no protective device between connection points 6 and 8, and the transferable power of connection points 6 and 8 is only the maximum value, i.e., the transferable power of connection point 6. Therefore, the transferability coefficient is...

[0158]

[0159] The coefficients that can be transferred to other nodes are shown in Table 6.

[0160] Table 6 Available Supply Coefficient

[0161]

[0162] (3) Adjustment of expected power outage time

[0163] Based on the power supply reliability assessment results and the transferability coefficient without considering the transfer capability, the corrected results are shown in Table 7. The row containing "Total" in the table represents the expected outage time u for each node considering the transfer capability. LP .

[0164] Table 7. Power supply reliability assessment results considering transfer constraints (retain 4 decimal places, unit: h)

[0165]

[0166]

[0167] On the other hand, the present invention proposes an electronic device, characterized in that it includes: at least one processor; a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform any one of the medium-voltage power distribution network power supply reliability assessment methods.

[0168] On the other hand, the present invention proposes a medium, which is a computer storage medium storing a computer program, wherein the computer program, when executed by a processor, implements any one of the methods for evaluating the reliability of power supply in a medium-voltage distribution network.

[0169] Computer storage media may be simply referred to as media. Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Dual Data SDRAM (DDRSDRAM), Enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), Rambus Direct RAM (RDRAM), Direct Memory Bus Dynamic RAM (DRDRAM), and Memory Bus Dynamic RAM (RDRAM). The various embodiments described in this specification are presented in a progressive manner, and similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, for embodiments of apparatus, devices, and non-volatile computer storage media, since they are substantially similar to the method embodiments, the description is relatively simple, and relevant parts can be referred to the description of the method embodiments.

[0170] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for assessing the reliability of power supply in a medium-voltage distribution network, characterized in that, include: Based on coding rules, the protection devices of the distribution network are numbered using a topology search algorithm, wherein the coding rule is that the upstream protection device number is less than the downstream protection device number; Generating the normal power flow distribution during normal operation of a medium-voltage distribution network based on power flow calculation methods; Traverse all connection points within the evaluation area. For each connection point, calculate the transfer power that the connection point can carry based on the normal power flow distribution, and record the protection device number between each connection point and the power supply point of the line where the connection point is located to obtain the associated protection device number. Enumerate the out-of-service components within the assessment area. If there are associated contact points and associated nodes in the downstream impact range of the out-of-service components, construct a set of protection devices related to the associated contact points based on the associated protection device numbers. If there are protection devices in the protection device set located in the downstream impact range of the out-of-service components, set the power of the feeder segment where the protection device with the smallest number is located as the power that the out-of-service feeder needs to transfer.

2. The method for assessing the reliability of medium-voltage power distribution networks according to claim 1, characterized in that, The normal power flow distribution during normal operation of a medium-voltage distribution network is generated based on power flow calculation methods, specifically including: Starting from the concentrated load at the end of the medium-voltage line, the power at the end and the power at the beginning of each feeder segment are calculated sequentially towards the power source. By iterating through other loads and distributed power sources, the power at the end and the power at the beginning of each feeder segment are calculated. The normal power flow distribution is generated by summing up all end-point power and all beginning-point power.

3. The method for assessing the reliability of medium-voltage power distribution networks according to claim 2, characterized in that, Starting with the concentrated load at the end of the medium-voltage line, the power at the end and the power at the beginning of each feeder segment are calculated sequentially towards the power source. Specifically, this includes: The power loss of the admittance branch at the end of the feeder section is calculated as follows: In the formula, U0 is the power loss of the admittance branch at the end of the feeder segment; G is the conductance of the admittance branch of the feeder segment; U2 is the voltage at the end of the feeder segment, =U2 = U0 N U N B is the effective value of the rated voltage; B is the susceptance of the feeder section admittance branch. The complex power of the concentrated load at the end of the feeder segment is superimposed with the power loss of the admittance branch at the end of the feeder segment to obtain the end power: In the formula, For end power; The complex power of the concentrated load at the end of the feeder section; The power loss of the admittance branch at the end of the feeder section; In the formula, P2 and Q2 are the active and reactive power of the centralized load at the end or the distributed power source, respectively; Based on the loss of the feeder segment impedance and the power at the end, the preliminary starting power of the feeder segment is calculated: In the formula, Z is the branch impedance of the feeder section; U1 = U2 = U N U2 is the voltage at the end of the feeder segment; S2′ is the terminal power; The model; Calculate the loss at the admittance of the feeder segment: The starting power is calculated based on the loss of the feeder segment's starting admittance and the initial starting power of the feeder segment:

4. The method for assessing the reliability of medium-voltage power distribution networks according to claim 2, characterized in that, The expression for the power transfer capacity of the connection point is: In the formula, S l,max Rated apparent power; S l B represents the apparent power of the load carried by feeder segment l during normal network operation. tie,i U is the set of feeder segment numbers between connection point i and power point; N I represents the effective value of the rated voltage of the feeder section. l,max is the maximum allowable current for the feeder segment, and l is the feeder segment number.

5. The method for assessing the reliability of medium-voltage distribution network power supply according to any one of claims 1 to 4, characterized in that, Also includes: Based on the power required to be transferred from the outage feeder and the power transfer capacity of the tie point, a transferability coefficient is calculated, and the expected outage time of the associated node is corrected based on the transferability coefficient, specifically including: Obtain the number of independent transferable areas and the number of associated contact points downstream of the out-of-service component. The independent transferable area refers to the power supply area downstream of the component that has associated contact points but is no longer connected to each other after the component is out of service. The power transfer coefficient is calculated based on the number of independent transferable areas and the number of associated connection points, the power required to be transferred by the out-of-service feeder, and the power transfer capacity of the connection point. For the associated nodes within the independent power transfer area, the expected power outage time of the associated nodes is adjusted based on the power transfer coefficient.

6. The method for assessing the reliability of medium-voltage distribution network power supply according to claim 5, characterized in that, If both the number of independent transferable areas and the number of associated contact points are one, then the expression for the transferability coefficient is: In the formula, S tie,m The connection point can carry transferred power; S k,m Power needs to be transferred to the out-of-service feeder; The expression for the expected power outage time of the associated node is: you LP =(1-e m )l k t k +e m l k t df,m ; In the formula, λ k t represents the average downtime rate of component k; k The average downtime repair time for component k is the time required to restore service. t df,m It is the sum of the location and isolation time of the shutdown of the shutdown component k and the switching time of the associated contact point m.

7. The method for assessing the reliability of medium-voltage power distribution networks according to claim 5, characterized in that, If the number of independent transferable areas is one, the number of associated contact points is multiple, and if there is a protective device separation between two of the associated contact points, then the expression for the transferability coefficient is: In the formula: and These are the transferable power capacities of connection points m1 and m2, respectively. If there is no protective device separation between the two associated contact points, then the expression for the transferability coefficient is:

8. The method for assessing the reliability of medium-voltage distribution network power supply according to claim 5, characterized in that, If both the number of independently transferable areas and the number of associated contact points are multiple, and if there is a protective device segmentation between two of the associated contact points, then the expression for the transferability coefficient is: In the formula, and These are the transferable power capacities of connection points m1 and m2, respectively. and The power that the out-of-service feeder needs to transfer from the connection points m1 and m2 downstream of the out-of-service component k is respectively the power that the out-of-service feeder needs to transfer from the connection points m1 and m2. If there is no protective device separation between the two associated contact points, then the expression for the transferability coefficient is:

9. An electronic device, characterized in that, include: At least one processor; A memory that is communicatively connected to the at least one processor; The memory stores instructions that can be executed by the at least one processor, which are executed by the at least one processor to enable the at least one processor to perform the medium-voltage power distribution network power supply reliability assessment method according to any one of claims 1 to 8.

10. A medium, characterized in that, The system contains a computer program that, when executed by a processor, implements the medium-voltage power distribution network reliability assessment method as described in any one of claims 1 to 8.

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