Power grid-independent equivalent model-based on-line loop closing current estimation method and system for distribution network

Abstract

This invention discloses an online prediction method and system for distribution network loop current that does not rely on a power grid equivalent model. The method includes: calculating the equivalent impedance based on previous loop-closing operation data of two substations A and B on the loop line; determining the equivalent bus impedance from the system central point to substation A, the equivalent bus impedance from the system central point to substation B, and the equivalent impedance of the entire loop line; for the current loop closure, collecting the bus phase voltages of substations A and B before the current loop closure and the load flow of the loop line; calculating the bus voltage difference between substations A and B before the current loop closure; and calculating the power flow through the loop based on a preset function model. This invention enables simple and easy online prediction of distribution network loop current, avoiding protection tripping and distribution network equipment damage caused by excessive loop current, and preventing power outages, delayed operations, or unnecessary adjustments to the main grid mode due to unpredictable loop current.

Description

Technical Field

[0001] This invention belongs to the field of power grid flow calculation, specifically relating to an online prediction method and system for distribution network loop current that does not rely on a power grid equivalent model. Background Technology

[0002] When adjusting the operation mode or transferring loads in distribution network lines, a loop-closing and loop-breaking method is typically used to avoid short-term power outages. Excessive loop current during loop closure can trigger protection trips, causing voltage loss and equipment damage. With the increasing scale of the power grid, the growth of grid load, the integration of local power sources, and unreasonable grid planning and operation modes, the problem of excessive loop current is becoming increasingly prominent, requiring measures for prediction and avoidance. The loop current of a distribution network is related to the load flow and equivalent impedance of the loop. Loop current calculation is generally divided into online and offline methods. Online calculation can select real-time grid cross-sectional loads, and the calculation results are more meaningful for current grid safety and stability analysis and fault handling. However, regardless of the online or offline method, existing calculation methods require simulation modeling of the loop, and the calculation results depend on the accuracy of the grid model and parameters. For distribution networks, line parameters are not measured in real-time. Some overhead and cable lines have various line types, diameters, and lengths, making it difficult to obtain line parameters through theoretical calculations. Furthermore, frequent line changes and upgrades make it even more difficult to update model parameters in real time. Therefore, traditional calculation methods that rely on grid modeling and parameter accuracy are not suitable for calculating the closed-loop current of distribution networks. Summary of the Invention

[0003] The technical problem this invention aims to solve is to provide an online prediction method and system for distribution network loop current that does not rely on a power grid equivalent model, addressing the aforementioned problems in the prior art. This invention can achieve approximately accurate calculation of the loop current through online calculation without relying on a power grid equivalent model and the correctness of model parameters. Based on the calculation results, it can determine whether the distribution network loop operation can be performed, avoiding protection tripping and damage to distribution network equipment due to excessive loop current, or unnecessary adjustments to the main grid mode and power outages and adjustments to the distribution network due to the difficulty in predicting the loop current. This overcomes the current practical problems of difficult distribution network line modeling and maintenance, and difficulty in predicting loop power flow.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A method for online prediction of distribution network closed-loop current that does not rely on a power grid equivalent model includes:

[0006] S1. Calculate the equivalent impedance based on the detection data of previous loop-closing operations of two substations A and B on the loop-closing line, and determine the equivalent impedance of the bus from the system central point to substation A, the equivalent impedance of the bus from the system central point to substation B, and the equivalent impedance of the entire loop-closing line.

[0007] S2, for this loop closure, collect the bus phase voltages and load flow of the looped lines for substations A and B before this loop closure, calculate the bus voltage difference between substations A and B before this loop closure, and calculate the power flow through the loop using the following formula:

[0008]

[0009] In the above formula, The voltage difference between the busbars before substations A and B are closed in a loop. and These represent the load flow of the closed loop lines of substations A and B before the loop closure. and These are the bus phase voltages of substations A and B before the loop closure, respectively. and These are the equivalent bus impedances from the system's central point to substations A and B, respectively. The equivalent impedance of the entire closed loop line. To transcend trends.

[0010] Optionally, the functional expression for determining the equivalent bus impedance from the system central point to substation A in step S1 is:

[0011]

[0012] The functional expression for determining the equivalent bus impedance from the system central point to substation B in step S1 is as follows:

[0013]

[0014] in, and These are the bus phase voltages of substation A before and during loop closure, respectively. and These are the bus currents of substation A before and during loop closure, respectively. Let be the equivalent bus impedance from the system's central point to substation A, P1 and P1′ be the reactive power of substation A before and after loop closure, Q1 and Q1′ be the active power of substation A before and after loop closure, and j be the imaginary unit. and These are the bus phase voltages of substation B before and during loop closure, respectively. and These are the bus currents of substation B before and during loop closure, respectively. Let P2 be the equivalent bus impedance from the system's central point to substation B, and P2 and P2′ be the active power of substation B before and after loop closure, respectively. Q2 and Q2′ be the reactive power of substation B before and after loop closure, respectively.

[0015] Optionally, the functional expression for determining the equivalent impedance of the entire closed loop line in step S1 is:

[0016]

[0017] in, and These are the bus phase voltages of substation A and substation B when the loop is closed, respectively. This represents the change in bus voltage between substation A and substation B when the loop is closed. and Q1′ and Q2′ represent the bus voltage changes of substations A and B respectively when the loop is closed, and Q1′ and Q2′ represent the reactive power of substations A and B respectively when the loop is closed.

[0018] Optionally, after calculating the cross-current flow in step S2, the method further includes determining whether the loop-closing condition is met based on the cross-current flow to decide whether to control substation A on the loop-closing line to perform a loop-closing operation, denoted as S. N The allowable current is I N The functional expression for the loop closure condition is:

[0019]

[0020] In the above formula, Let P1 represent the active power of the load flow of the closed loop line of substation A before loop closure, and Q1 represent the reactive power of the load flow of the closed loop line of substation A before loop closure. j is the imaginary unit. To transcend trends.

[0021] Optionally, after calculating the cross-current flow in step S2, the method further includes determining whether the loop-closing condition is met based on the cross-current flow to decide whether to control substation A on the loop-closing line to perform a loop-closing operation, denoted as S. N The allowable current is I N The functional expression for the loop closure condition is:

[0022]

[0023] In the above formula, Let P1 represent the active power of the load flow of the closed loop line of substation A before loop closure, and Q1 represent the reactive power of the load flow of the closed loop line of substation A before loop closure. j is the imaginary unit. To transcend trends, and These are the bus phase voltages of substations A and B before the loop closure, respectively.

[0024] Optionally, after calculating the cross-current flow in step S2, the method further includes determining whether the loop-closing condition is met based on the cross-current flow to decide whether to control substation B on the loop-closing line to perform a loop-closing operation, and denoting the allowable load of the loop-closing line of substation B as S. N The allowable current is I N The functional expression for the loop closure condition is:

[0025]

[0026] In the above formula, P2 represents the active power flow of the looped lines of substation B before loop closure, Q2 represents the reactive power flow of the looped lines of substation B before loop closure, and j is the imaginary unit. To transcend trends.

[0027] Optionally, after calculating the cross-current flow in step S2, the method further includes determining whether the loop-closing condition is met based on the cross-current flow to decide whether to control substation B on the loop-closing line to perform a loop-closing operation, and denoting the allowable load of the loop-closing line of substation B as S. N The allowable current is I N The functional expression for the loop closure condition is:

[0028]

[0029] In the above formula, P2 represents the active power flow of the looped lines of substation B before loop closure, Q2 represents the reactive power flow of the looped lines of substation B before loop closure, and j is the imaginary unit. To transcend trends, These are the bus phase voltages of substation B before the loop closure.

[0030] Optionally, step S2, which involves collecting the bus voltages of substations A and B before the current loop closure, includes: using two different bus voltage vector measurement devices to collect the phase bus voltages of substations A and B before the loop closure, and the two different bus voltage vector measurement devices are synchronized with a time synchronization host that serves as a clock source in advance, so that the two different bus voltage vector measurement devices collect the bus voltages of substations A and B before the loop closure in a synchronized manner.

[0031] Furthermore, this embodiment also provides an online prediction system for distribution network closed-loop current that does not rely on a power grid equivalent model, including a microprocessor and a memory connected to each other, wherein the microprocessor is programmed or configured to execute the online prediction method for distribution network closed-loop current that does not rely on a power grid equivalent model.

[0032] Furthermore, this embodiment also provides a computer-readable storage medium storing a computer program, which is used to be programmed or configured by a microprocessor to execute the online prediction method for distribution network loop current independent of the power grid equivalent model.

[0033] Compared with existing technologies, the present invention has the following advantages: The method of the present invention includes: calculating the equivalent impedance based on the detection data of previous loop-closing operations of two substations A and B on the loop-closing line, determining the equivalent bus impedance from the system central point to substation A, the equivalent bus impedance from the system central point to substation B, and the equivalent impedance of the entire loop-closing line; for the current loop closure, collecting the bus voltage of substations A and B before the current loop closure and the load flow of the loop-closing line, calculating the bus voltage difference between substations A and B before the current loop closure, and calculating the power flow through the loop based on a preset function model. Addressing the current difficulties in modeling and maintaining distribution network lines and the difficulty in predicting loop-closing power flow, the present invention can achieve approximately accurate calculation of the loop-closing current through online calculation without relying on the power grid equivalent model and the correctness of the model parameters. Based on the calculation results, it can determine whether the distribution network loop closure operation can be performed, avoiding protection tripping and distribution network equipment damage due to excessive loop-closing current, or unnecessary adjustments to the main grid mode and distribution network power outages due to the difficulty in predicting the loop-closing current. This invention achieves simple and easy online prediction of distribution network loop current by acquiring and uploading bus voltage vector (phase angle). The approximate calculation results fully meet the requirements for loop judgment, avoiding protection tripping and distribution network equipment damage caused by excessive loop current, and avoiding power outages, delayed operations, or unnecessary adjustments to the main grid mode caused by unpredictable loop current. It avoids many problems existing in traditional methods: difficulty in distribution network modeling, inconvenient model maintenance, difficulty in obtaining model parameters, and excessive calculation errors and loss of reference value due to inadequate model maintenance. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the basic process of the method in an embodiment of the present invention.

[0035] Figure 2 This is a schematic diagram of the loop closure circuit before (a) and during (b) the loop closure in an embodiment of the present invention.

[0036] Figure 3 This is an equivalent diagram of the closed-loop power flow in an embodiment of the present invention.

[0037] Figure 4 This is a schematic diagram illustrating the voltage vector (phase angle) measurement principle in an embodiment of the present invention. Detailed Implementation

[0038] like Figure 1 As shown, the online prediction method for distribution network closed-loop current that does not rely on the power grid equivalent model in this embodiment includes:

[0039] S1. Calculate the equivalent impedance based on the detection data of previous loop-closing operations of two substations A and B on the loop-closing line, and determine the equivalent impedance of the bus from the system central point to substation A, the equivalent impedance of the bus from the system central point to substation B, and the equivalent impedance of the entire loop-closing line.

[0040] S2, for this loop closure, collect the bus phase voltages and load flow of the looped lines for substations A and B before this loop closure, calculate the bus voltage difference between substations A and B before this loop closure, and calculate the power flow through the loop using the following formula:

[0041]

[0042] In the above formula, The voltage difference between the busbars before substations A and B are closed in a loop. and These represent the load flow of the closed loop lines of substations A and B before the loop closure. and These are the bus phase voltages of substations A and B before the loop closure, respectively. and These are the equivalent bus impedances from the system's central point to substations A and B, respectively. The equivalent impedance of the entire closed loop line. To transcend trends.

[0043] Figure 2 This is a schematic diagram of the loop closure circuit before (a) and during (b) loop closure in an embodiment of the present invention. See also Figure 2 In this embodiment, the phase voltage of the 10kV bus at station A before loop closure is: The load flow of the closed loop line is P1+jQ1, and the phase voltage of the 10kV bus at station A at the time of loop closure is... The load flow of the loop line is P1′+jQ1′; the phase voltage of the 10kV bus at station B before loop closure is... The load flow of the closed loop line is P2+jQ2, and the phase voltage of the 10kV bus at station B at the time of loop closure is... The load flow of the closed loop line is P2′+jQ2′; the equivalent impedance of the 10kV bus from the system central point to station A is... The equivalent impedance of the 10kV bus from the system's central point to Station B is: Furthermore, the impedance parameters in the system are all approximately linear and remain constant.

[0044] Assume the voltage of the central node in the system before and during loop closure. If it remains unchanged, then:

[0045]

[0046]

[0047] In the above formula, Let (1) and (2) be the equivalent currents from the system central point to the 10kV busbar at station A before and during loop closure, respectively. Subtracting (2) from equation (1), we get:

[0048]

[0049] According to equation (4), the equivalent bus impedance from the central point of the system to substation A can be obtained. Therefore, the functional expression for determining the equivalent bus impedance from the system central point to substation A in step S1 of this embodiment is shown in equation (4).

[0050] Similarly, the functional expression for determining the equivalent bus impedance from the system central point to substation B in step S1 can be obtained as follows:

[0051]

[0052] in, and These are the bus phase voltages of substation A before and during loop closure, respectively. and These are the bus currents of substation A before and during loop closure, respectively. Let be the equivalent bus impedance from the system's central point to substation A, P1 and P1′ be the reactive power of substation A before and after loop closure, Q1 and Q1′ be the active power of substation A before and after loop closure, and j be the imaginary unit. and These are the bus phase voltages of substation B before and during loop closure, respectively. and These are the bus currents of substation B before and during loop closure, respectively. Let P2 be the equivalent bus impedance from the system's central point to substation B, and P2 and P2′ be the active power of substation B before and after loop closure, respectively. Q2 and Q2′ be the reactive power of substation B before and after loop closure, respectively.

[0053] Figure 3 This is the equivalent diagram of the closed-loop power flow in this embodiment. Figure 3 Ignoring the impact of voltage changes before and after loop closure on the load current, according to the superposition theorem, the current during loop closure can be equivalent to the load current. and through current Superimposed.

[0054] Similarly, without considering the power loss of the closed loop circuit itself, Figure 1 The line power flow during loop closure can be considered as two parts: load power flow P1′+P2′+j(Q1′+Q2′)≈P1+P2+j(Q1+Q2) and crossing power flow -(P2′+jQ2′).

[0055] The following ideal assumptions are made for the closed loop line: 1) The line load is uniformly distributed; 2) The line impedance is equal everywhere.

[0056] Let the equivalent impedance of the entire closed loop be... The voltage drop caused by the load power flow for:

[0057]

[0058] In the above formula, the horizontal line above the symbol indicates conjugate, for example... The conjugate of U1′ is represented by this, and so on.

[0059] Pressure drop caused by crossing the tide for:

[0060]

[0061] Then we have:

[0062]

[0063] Therefore, the functional expression for determining the equivalent impedance of the entire closed loop line in step S1 of this embodiment is shown in equation (8), where, and These are the bus phase voltages of substation A and substation B when the loop is closed, respectively. This represents the change in bus voltage between substation A and substation B when the loop is closed. and Q1′ and Q2′ represent the bus voltage changes of substations A and B respectively during loop closure, and Q1′ and Q2′ represent the reactive power of substations A and B respectively during loop closure. Based on the power flow of the loop line during loop closure and the collected 10kV bus phase voltages, the equivalent impedance of the entire loop line can be calculated using equation (8). The parameters used in Equations (4), (5), and (8) are only the line power flow and the 10kV bus voltage. The line current vector is not used, which can avoid the error caused by the asynchronous sampling of voltage and current vector data. The equivalent impedance of the system obtained by the previous loop closing data can be used for the next loop closing power flow calculation to determine whether the next loop closing power flow is within the allowable range and whether the loop closing conditions are met.

[0064] The system's equivalent impedance can be calculated by collecting data before and during the previous loop closure. Figure 2 The loop closing operation shown indicates that the load flow of the loop-closing line at station A before loop closing is... The load flow of the B-site loop line is Ignoring the power loss of the closed loop itself, the load flow is as follows: Without considering the power loss of the closed loop line itself, the line power flow during the closed loop can be regarded as two parts: load power flow P1′+P2′+j(Q1′+Q2′)≈P1+P2+j(Q1+Q2) and cross-flow power flow -(P2′+jQ2′).

[0065] Assume that the power flow at other points in the system remains unchanged compared to before the loop closure. Let the power flow across the loop be... The bus voltage difference before loop closure When the loop is closed, it can be viewed as being balanced by the voltage drop of four parts, crossing the current. Equivalent impedance from the system central point to the 10kV bus The pressure drop caused by the current, crossing the tidal current Equivalent impedance of closed loop line The pressure drop caused by the load flow Equivalent impedance of closed loop line The pressure drop caused by the above is given by equation (1).

[0066] Assuming the 10kV bus voltage phase angle of substation A (hereinafter referred to as Station A) is leading, the power flow of the closed loop at Station A will increase, while the power flow of the closed loop at substation B (hereinafter referred to as Station B) will decrease, or even reverse. Even if the power flow of the closed loop at Station B is reversed, the magnitude of the closed loop power flow will not exceed that of the closed loop at Station A. Therefore, the closing and unclosing conditions can be determined by calculating the power flow of the closed loop at the station with the leading phase angle (if the power flow of the closed loop at both stations is the same as the grid connection power flow, the conclusion is the opposite, i.e., the closing and unclosing conditions can be determined by calculating the power flow of the closed loop at the station with the lagging phase angle).

[0067] Assuming the 10kV bus voltage phase angle of station A is leading, the power flow of the looping line at station A will increase during loop closure, while the power flow of the looping line at station B will decrease, or even reverse. Even if the power flow of the looping line at station B reverses, the magnitude of the loop power flow will not exceed that of the looping line at station A. Therefore, the loop closure / reopening condition can be determined by calculating the power flow of the looping line at the station with the leading phase angle (if the power flow of the looping lines at both stations is the grid connection power flow, the conclusion is the opposite, i.e., the loop closure / reopening condition can be determined by calculating the power flow of the looping line at the station with the lagging phase angle). As an optional implementation, in this embodiment, after calculating the cross-current power flow in step S2, it further includes determining whether the loop closure condition is met based on the cross-current power flow to decide whether to control the two substations A and B on the looping line to perform loop closure operation. In this embodiment, after calculating the cross-current power flow in step S2, it further includes determining whether the loop closure condition is met based on the cross-current power flow to decide whether to control the substation A on the looping line to perform loop closure operation. Let the allowable load of the looping line of substation A be S. N The allowable current is I N The functional expression for the loop closure condition is:

[0068] or

[0069] In the above formula, Let P1 represent the active power of the load flow of the closed loop line of substation A before loop closure, and Q1 represent the reactive power of the load flow of the closed loop line of substation A before loop closure. j is the imaginary unit. To transcend trends, and These are the bus phase voltages of substations A and B before the loop closure, respectively.

[0070] In this embodiment, after calculating the cross-current flow in step S2, the method further includes determining whether the loop-closing condition is met based on the cross-current flow to decide whether to control substation B on the loop-closing line to perform a loop-closing operation. The allowable load of the loop-closing line of substation B is denoted as S. N The allowable current is I N The functional expression for the loop closure condition is:

[0071] or

[0072] In the above formula, P2 represents the active power flow of the looped lines of substation B before loop closure, Q2 represents the reactive power flow of the looped lines of substation B before loop closure, and j is the imaginary unit. To transcend trends, These are the bus phase voltages of substation B before the loop closure. It should be noted that the above derivation process and formulas are independent of the magnitude and actual direction of the power flow in the loop connection between stations A and B; that is, the subscripts "1" and "2" in the formulas can be interchanged.

[0073] Figure 4 This is a schematic diagram illustrating the voltage vector (phase angle) measurement principle in this embodiment. See also... Figure 4 In this embodiment, step S2 involves collecting the bus voltages of substations A and B before the current loop closure, which includes using two different bus voltage vector measurement devices. Figure 4 The two devices, denoted as Machine A and Machine B respectively, collect the bus phase voltages of substations A and B before loop closure. These two different bus voltage vector measurement devices are pre-synchronized with a time synchronization host (Machine C), which serves as the clock source, to ensure that the time of their respective bus voltage measurements of substations A and B before loop closure is synchronized. When performing loop closure calculations for the tie line between the two substations, Machine A and Machine B are responsible for collecting the 10kV bus phase voltages and communicating with the time synchronization host (Machine C). The time synchronization host (Machine C) provides the voltage phase angle reference value and uploads the collected data to the loop closure current calculation module. The real-time power flow of the loop line required by the loop closure current calculation module is forwarded by the dispatching master station system. The loop closure current calculation module is considered the execution entity of the online prediction method for distribution network loop closure current that does not rely on the power grid equivalent model in this embodiment, and can generally be implemented using computer equipment. The bus voltage vector measurement device is installed on the secondary side of the 10kV bus (TV) in the substation to measure and upload the bus voltage phase vector. Under certain sampling accuracy conditions, it achieves synchronous measurement and uploading of the 10kV bus voltage vector. Voltage phase angle measurement requires comparing the bus voltage phase before and after loop closure with the reference voltage phase. The phase angle measurement error should not exceed ±0.5°, and the bus voltage amplitude measurement error must meet relevant specifications. The voltage vector measurement device uses wireless communication to upload the voltage vector.

[0074] In summary, the method in this embodiment acquires and uploads the phase voltage of the 10kV bus where the loop-closing line is located using a bus voltage vector measurement device (distribution network PMU). Based on the historical bus voltage vectors before and after loop closure and the power flow of the loop-closing line, it calculates the equivalent impedance of the system and the loop-closing distribution network line in reverse. Using the calculated equivalent impedance and real-time voltage and load data, the loop-closing current under the current load condition is estimated to determine whether the loop-closing conditions are met. This embodiment's method, through the acquisition and uploading of the bus voltage vector (phase angle), easily achieves online prediction of the distribution network loop-closing current. The approximate calculation results fully meet the requirements for loop-closing judgment, avoiding protection tripping and distribution network equipment damage due to excessive loop-closing current, and avoiding power outages, delayed operations, or unnecessary adjustments to the main grid mode due to unpredictable loop-closing current. This embodiment's method avoids many problems existing in traditional methods: difficulty in distribution network modeling, inconvenient model maintenance, difficulty in obtaining model parameters, and excessive calculation errors and loss of reference value due to inadequate model maintenance.

[0075] Furthermore, this embodiment also provides an online prediction system for distribution network closed-loop current that does not rely on a power grid equivalent model, including a microprocessor and a memory interconnected thereto. The microprocessor is programmed or configured to execute the aforementioned online prediction method for distribution network closed-loop current that does not rely on a power grid equivalent model.

[0076] Furthermore, this embodiment also provides a computer-readable storage medium storing a computer program that is programmed or configured by a microprocessor to execute the aforementioned method for online prediction of distribution network loop current independent of the power grid equivalent model.

[0077] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-readable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the process. Figure 1 One or more processes and / or boxes Figure 1The computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0078] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for online prediction of distribution network closed-loop current that does not rely on a power grid equivalent model, characterized in that, include: S1. Based on the detection data from previous loop-closing operations of substations A and B on the loop line, calculate the equivalent impedance to determine the equivalent bus impedance from the system central point to substation A, the equivalent bus impedance from the system central point to substation B, and the equivalent impedance of the entire loop line. The functional expression for determining the equivalent bus impedance from the system central point to substation A is as follows: ， The functional expression for determining the equivalent bus impedance from the system's central point to substation B is: ， in, and These are the bus phase voltages of substation A before and during loop closure, respectively. and These are the bus currents of substation A before and during loop closure, respectively. Let be the equivalent bus impedance from the system's central point to substation A. and These are the active power of substation A before and during loop closure, respectively. and These are the reactive power of substation A before and during loop closure, respectively, where j is the imaginary unit; and These are the bus phase voltages of substation B before and during loop closure, respectively. and These are the bus currents of substation B before and during loop closure, respectively. Let be the equivalent bus impedance from the system's central point to substation B. and These are the active power of substation B before and during loop closure, respectively. and These represent the reactive power of substation B before and during loop closure, respectively; the horizontal line on the symbol indicates conjugate; the functional expression for determining the equivalent impedance of the entire loop line is: ， in, and These are the bus phase voltages of substation A and substation B when the loop is closed, respectively. This represents the change in bus voltage between substation A and substation B when the loop is closed. and These represent the changes in bus voltage at substations A and B, respectively, during loop closure. and These are the reactive power values ​​of substations A and B respectively during the loop closure; S2, for this loop closure, collect the bus phase voltages and load flow of the looped lines for substations A and B before this loop closure, calculate the bus voltage difference between substations A and B before this loop closure, and calculate the power flow through the loop using the following formula: ， In the above formula, This represents the bus voltage difference before substations A and B are closed in a loop. and These represent the load flow of the closed loop lines of substations A and B before the loop closure. and These are the bus phase voltages of substations A and B before the loop closure, respectively. and These are the equivalent bus impedances from the system's central point to substations A and B, respectively. The equivalent impedance of the entire closed loop line. To transcend trends.

2. The method for online prediction of distribution network closed-loop current without relying on the power grid equivalent model according to claim 1, characterized in that, After calculating the cross-current flow in step S2, the process also includes determining whether the loop-closing condition is met based on the cross-current flow to decide whether to control substation A on the loop-closing line to perform a loop-closing operation. Let the allowable load of the loop-closing line of substation A be denoted as... The functional expression for the loop closure condition is: ， In the above formula, This refers to the load flow of the loop-connected line at substation A before loop closure. P 1 represents the active power flow of the loop-connected lines of substation A before loop closure. Q 1 represents the reactive power of the load flow of the loop line of substation A before loop closure. j The imaginary unit, To transcend trends.

3. The method for online prediction of distribution network closed-loop current without relying on the power grid equivalent model according to claim 1, characterized in that, After calculating the cross-current flow in step S2, the process also includes determining whether the loop-closing condition is met based on the cross-current flow to decide whether to control substation A on the loop-closing line to perform a loop-closing operation. The allowable current of substation A is denoted as... The functional expression for the loop closure condition is: ， In the above formula, This refers to the load flow of the loop-connected line at substation A before loop closure. P 1 represents the active power flow of the loop-connected lines of substation A before loop closure. Q 1 represents the reactive power of the load flow of the loop line of substation A before loop closure. j The imaginary unit, To transcend trends, and These are the bus phase voltages of substations A and B before the loop closure, respectively.

4. The method for online prediction of distribution network closed-loop current without relying on the power grid equivalent model according to claim 1, characterized in that, After calculating the cross-current flow in step S2, the process also includes determining whether the loop-closing condition is met based on the cross-current flow to decide whether to control substation B on the loop-closing line to perform a loop-closing operation. Let the allowable load of the loop-closing line of substation B be... The functional expression for the loop closure condition is: ， In the above formula, This refers to the load flow of the B loop line before the loop is closed. P 2 represents the active power flow of the loop line of substation B before loop closure. Q 2 represents the reactive power of the load flow of the loop line of substation B before loop closure. j The imaginary unit, To transcend trends.

5. The method for online prediction of distribution network closed-loop current without relying on the power grid equivalent model according to claim 1, characterized in that, After calculating the cross-current flow in step S2, the process also includes determining whether the loop-closing condition is met based on the cross-current flow to decide whether to control substation B on the loop-closing line to perform a loop-closing operation. The allowable current of substation B is denoted as... The functional expression for the loop closure condition is: ， In the above formula, This refers to the load flow of the B loop line before the loop is closed. P 2 represents the active power flow of the loop line of substation B before loop closure. Q 2 represents the reactive power of the load flow of the loop line of substation B before loop closure. j The imaginary unit, To transcend trends, These are the bus phase voltages of substation B before the loop closure.

6. The method for online prediction of distribution network closed-loop current without relying on the power grid equivalent model according to claim 1, characterized in that, Step S2 involves acquiring the bus voltages of substations A and B before the current loop closure, which includes: using two different bus voltage vector measurement devices to acquire the phase bus voltages of substations A and B before the loop closure, and the two different bus voltage vector measurement devices are synchronized with a time synchronization host that serves as a clock source in advance, so that the time of the bus voltage acquisitions of substations A and B before the loop closure is synchronized by the two different bus voltage vector measurement devices.

7. An online prediction system for closed-loop current of a distribution network that does not rely on an equivalent power grid model, comprising a microprocessor and a memory interconnected, characterized in that, The microprocessor is programmed or configured to execute the online prediction method for distribution network closed-loop current that does not rely on a power grid equivalent model, as described in any one of claims 1 to 6.

8. A computer-readable storage medium storing a computer program, characterized in that, The computer program is used to be programmed or configured by a microprocessor to execute the online prediction method for distribution network loop current that does not rely on a power grid equivalent model, as described in any one of claims 1 to 6.

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