Method and device for analyzing sensitivity of distribution network current protection

Abstract

The application provides a distribution network current protection sensitivity analysis method and device, the method comprises the following steps: obtaining the first short-circuit current and the system short-circuit capacity when there is no distributed power supply connected to the power system according to the distribution network parameters; determining the fault short-circuit ratio according to the relative relationship between the grid-connected position of the distributed power supply, the current measurement point position and the fault position; calculating the phase of the distributed power supply output current according to the power system phase voltage, the positive and negative sequence short-circuit impedance, the line impedance, the distributed power supply output current size, the line impedance between the bus and the line impedance angle; determining the second short-circuit current when the distributed power supply is connected to the power system according to the first short-circuit current, the fault short-circuit ratio and the phase; and performing current protection sensitivity evaluation according to the current protection setting value and the second short-circuit current. According to the application, the short-circuit current size can be calculated without iterative calculation by a computer, and the current protection sensitivity evaluation can be realized.

Description

Technical Field

[0001] This application relates to power system relay protection technology, and in particular to a method and device for sensitivity analysis of distribution network current protection. Background Technology

[0002] The power industry must vigorously develop renewable energy and build a power system dominated by new energy sources. Distributed generation (DG) has been widely used in distribution networks due to its abundant resources, flexible site selection, and wide application range. After DG is connected to the distribution network, the network changes from a single-ended power supply mode to a multi-ended power supply mode, thus affecting the power flow direction and short-circuit current distribution, and consequently the sensitivity of current protection devices.

[0003] To evaluate the sensitivity of current protection under distributed generation (DG) integration, the key is to calculate the magnitude of the short-circuit current. Considering the nonlinearity of DG control strategies, current methods for calculating short-circuit current in grids with DG primarily rely on numerical iterative solutions, which require computer software. When a fault occurs in a distribution network with a high proportion of DG, the current at the current protection device is related to various factors such as the DG capacity, output current phase, connection location, and fault location, making quantitative assessment of the current protection sensitivity quite difficult. Summary of the Invention

[0004] One objective of this application is to provide a method for analyzing the sensitivity of distribution network current protection, which can intuitively obtain the factors affecting the magnitude of short-circuit current or the sensitivity of current protection in a power grid containing distributed generation, calculate the magnitude of the short-circuit current, and thus evaluate the sensitivity of current protection. Another objective of this application is to provide a device for analyzing the sensitivity of distribution network current protection. A further objective of this application is to provide a computer device. A final objective of this application is to provide a readable medium.

[0005] To achieve the above objectives, this application discloses a method for analyzing the sensitivity of distribution network current protection, including:

[0006] The first short-circuit current and system short-circuit capacity when no distributed power source is connected to the power system are obtained based on the distribution network parameters.

[0007] The fault short-circuit ratio is determined based on the relative relationship between the grid connection location of the distributed generation in the power system and the location of the current measurement point and the fault location.

[0008] When the distributed generation adopts the optimal positive sequence voltage support strategy, the phase of the distributed generation output current is calculated based on the power system phase voltage, positive and negative sequence short-circuit impedance, line impedance, the magnitude of the distributed generation output current, the line impedance between buses, and the line impedance angle.

[0009] The second short-circuit current when the distributed power source is connected to the power system is determined based on the first short-circuit current, the fault short-circuit ratio, and the phase.

[0010] The sensitivity of the current protection is evaluated based on the current protection setting value and the second short-circuit current.

[0011] To achieve the above objectives, this application discloses a distribution network current protection sensitivity analysis device, comprising:

[0012] The current and capacity acquisition unit is used to obtain the first short-circuit current and system short-circuit capacity when no distributed power source is connected to the power system, based on the distribution network parameters.

[0013] The fault short-circuit ratio determination unit is used to determine the fault short-circuit ratio based on the relative relationship between the grid connection location of the distributed generation in the power system, the current measurement point location, and the fault location.

[0014] The phase determination unit is used to calculate the phase of the distributed generation output current based on the power system phase voltage, positive and negative sequence short-circuit impedance, line impedance, the magnitude of the distributed generation output current, the line impedance between buses, and the line impedance angle when the distributed generation adopts the optimal positive sequence voltage support strategy.

[0015] A short-circuit current determination unit is used to determine a second short-circuit current when a distributed power source is connected to the power system based on the first short-circuit current, the fault short-circuit ratio, and the phase.

[0016] The sensitivity evaluation unit is used to evaluate the sensitivity of the current protection based on the current protection setting value and the second short-circuit current.

[0017] To achieve the above objectives, this application discloses a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor.

[0018] The processor implements the method when executing the program.

[0019] To achieve the above objectives, this application discloses a computer-readable medium having a computer program stored thereon, which, when executed by a processor, implements the method.

[0020] By utilizing the distribution network current protection sensitivity analysis method and device provided in this application, the factors affecting the magnitude of short-circuit current or the sensitivity of current protection in a power grid containing distributed power sources can be intuitively obtained through the fault short-circuit ratio index. This application utilizes the short-circuit current calculation method related to the fault short-circuit ratio when distributed power sources are connected to the power system, which can determine the magnitude of short-circuit current without the need for iterative calculation using a computer, thereby realizing the evaluation of the sensitivity of current protection. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart of the distribution network current protection sensitivity analysis method according to an embodiment of this application;

[0023] Figure 2 This is a flowchart illustrating a method for obtaining the first short-circuit current and system short-circuit capacity based on distribution network parameters when no distributed power source is connected to the power system, according to an embodiment of this application.

[0024] Figure 3 This is a flowchart illustrating the method for calculating the phase B short-circuit current and phase C short-circuit current based on the phase voltage and short-circuit loop impedance of the power system according to an embodiment of this application.

[0025] Figure 4 This is a schematic diagram of a distribution network line containing distributed power sources, as described in an embodiment of this application.

[0026] Figure 5 This is a schematic diagram of a composite sequence network according to an embodiment of this application;

[0027] Figure 6 This is a schematic diagram of the distribution network current protection sensitivity analysis device according to an embodiment of this application;

[0028] Figure 7 This is a schematic diagram of the current and capacity acquisition unit 601 according to an embodiment of this application;

[0029] Figure 8 This is a schematic diagram of the BC phase short-circuit current determination module 702 according to an embodiment of this application;

[0030] Figure 9 This is a schematic diagram of the phase determination unit 603 according to an embodiment of this application;

[0031] Figure 10 This is a schematic diagram of the short-circuit current determination unit 604 according to an embodiment of this application;

[0032] Figure 11 This is a diagram of a power distribution network structure including distributed power sources, as described in an embodiment of this application. Detailed Implementation

[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] It should be noted that the log processing method and system disclosed in this application can be used in the financial field, or in any field other than the financial field. The application field of the log processing method and system disclosed in this application is not limited.

[0035] Figure 1 This is a flowchart of the distribution network current protection sensitivity analysis method according to an embodiment of this application, as shown below. Figure 1 As shown, the sensitivity analysis method for distribution network current protection includes:

[0036] S101: Obtain the first short-circuit current and system short-circuit capacity when no distributed generation (IIDG Inverter-Inter-faced Distributed Generator) is connected to the power system based on the distribution network parameters;

[0037] It should be noted that distribution network parameters may include power system phase voltages and short-circuit loop impedances, etc.

[0038] Specifically, when no distributed power source is connected to the power system, the first short-circuit current includes the three-phase short-circuit current, the B-phase short-circuit current, and the C-phase short-circuit current.

[0039] S102: Determine the fault short-circuit ratio based on the relative relationship between the grid connection location of the distributed generation in the power system and the location of the current measurement point and the fault location;

[0040] Specifically, considering the distribution of current measurement points, fault locations, and distributed power source grid connection locations, three types of fault short-circuit ratios are defined, and calculation methods are given. Given the system short-circuit capacity and the rated capacity of the distributed power source at the corresponding location, the three types of fault short-circuit ratios can be calculated using the calculation methods.

[0041] S103: When the distributed generation adopts the positive sequence voltage optimal voltage support strategy, the phase of the distributed generation output current is calculated based on the power system phase voltage, positive and negative sequence short-circuit impedance, line impedance, distributed generation output current, line impedance between buses and line impedance angle.

[0042] When a distributed generation adopts the optimal voltage support strategy, the phase of the output current of the distributed generation is only related to the line impedance angle and the phase of the grid-connected positive sequence voltage.

[0043] S104: Determine the second short-circuit current when the distributed power source is connected to the power system based on the first short-circuit current, the fault short-circuit ratio and the phase;

[0044] S105: Evaluate the sensitivity of the current protection based on the current protection setting value and the second short-circuit current.

[0045] Depend on Figure 1 The method shown in this application allows for a direct understanding of the factors influencing the magnitude of short-circuit current or the sensitivity of current protection in a power grid containing distributed generation sources, through the fault short-circuit ratio index. This application utilizes a short-circuit current calculation method related to the fault short-circuit ratio when distributed generation sources are connected to the power system, which eliminates the need for iterative calculations using a computer to determine the magnitude of the short-circuit current, thereby enabling the evaluation of the sensitivity of current protection.

[0046] In one embodiment, such as Figure 2 As shown, the first short-circuit current and system short-circuit capacity are obtained from the distribution network parameters when there is no distributed generation connected to the power system, including:

[0047] S201: Calculate the three-phase short-circuit current I based on the phase voltage and short-circuit loop impedance of the power system. k 0 (3) ;

[0048] Three-phase short-circuit current I when no distributed power source is connected k 0 (3) The calculation formula is:

[0049]

[0050] Where Es is the system phase voltage, Z ∑ This is the short-circuit loop impedance.

[0051] S202: Calculate the short-circuit current of phase B and phase C based on the phase voltage and short-circuit loop impedance of the power system;

[0052] In one embodiment, such as Figure 3 As shown, S202 includes the following steps:

[0053] S301: Calculate the positive sequence current based on the phase voltage and short-circuit loop impedance of the power system.

[0054]

[0055] Among them, Z ∑(1) It is the positive sequence short-circuit impedance, Z ∑(2) It is a negative sequence short-circuit impedance.

[0056] S302: Calculate the first phase B short-circuit current and the first phase C short-circuit current based on the positive sequence current.

[0057] Short-circuit current Ik of phases BC when no distributed power source is connected B0 (2) I k C0 (2) The calculation formulas are as follows:

[0058]

[0059]

[0060] Where j is the imaginary unit, multiplying a complex number by j is equivalent to rotating the complex number counterclockwise by 90°.

[0061] S203: Calculate the short-circuit capacity of the system based on the three-phase short-circuit current and the normal operating voltage at the short-circuit point.

[0062] Specifically, the system short-circuit capacity S ac The calculation formula is as follows:

[0063]

[0064] U N This is the normal operating voltage at the short circuit point, typically taken as the average rated voltage.

[0065] In one embodiment, S102 specifically includes: determining the fault short-circuit ratio based on the system short-circuit capacity, the rated capacity of the distributed power source corresponding to the relative relationship, the rated output current of the distributed power source corresponding to the relative relationship, the first three-phase short-circuit current, and the positive sequence current.

[0066] Based on the short-circuit ratio (SCR), considering the distribution of current measurement point location, fault location, and distributed power source grid connection location, three types of fault short-circuit ratios are defined: the first fault short-circuit ratio (SCR11), the second fault short-circuit ratio (SCR12), and the third fault short-circuit ratio (SCR2). Specifically:

[0067] If the grid connection point is before the current measurement point and the fault location, the fault ratio is the first fault short-circuit ratio SCR11:

[0068]

[0069] Among them, P N.11 I represents the rated capacity of the distributed power source at the grid connection location corresponding to the first fault short-circuit ratio. PV.N.11 This refers to the rated output current of the distributed power source at its corresponding grid connection location.

[0070] If the grid connection location is before the fault location and after the current measurement point location, the fault ratio is the second fault short-circuit ratio SCR12:

[0071]

[0072] Among them, P N.12 I represents the rated capacity of the distributed power source at the grid connection location corresponding to the second fault short-circuit ratio. PV.N.12 This refers to the rated output current of the distributed power source at its corresponding grid connection location.

[0073] If the grid connection location is after the current measurement point and the fault location, the fault ratio is the third fault short-circuit ratio SCR2:

[0074]

[0075] Among them, P N.2 I represents the rated capacity of the distributed power source at the grid-connected location corresponding to the third fault short-circuit ratio. PV.N.2 This refers to the rated output current of the distributed power source at its corresponding grid connection location.

[0076] In one embodiment, in S103, when the distributed power source adopts the optimal voltage support strategy for positive sequence voltage, the phase of the output current of the distributed power source is only related to the line impedance angle and the phase of the grid-connected positive sequence voltage. The phase θ of the output current of the distributed power source can be calculated based on the phase of the grid-connected bus voltage and the line impedance angle.

[0077] θ=θ u(1) -θ z (9)

[0078] Where θ is the phase of the output current of the distributed power source, θu(1) is the phase of the corresponding distributed power source grid-connected bus voltage, and θz is the line impedance angle.

[0079] The above analysis shows that the key to determining the phase of the distributed generation output current is to determine the phase of the grid-connected bus voltage (positive sequence voltage at the grid connection point) of the distributed generation. Suppose there are n distributed generation grid connection points. Equations are set up for the positive sequence voltage of each distributed generation grid connection point in the composite sequence network. Separating the real and imaginary parts of the equations, we obtain 2n equations. The unknowns are the amplitude and phase of the positive sequence voltage at the grid connection point, totaling 2n. Solving these equations yields the phase of the positive sequence voltage at the grid connection point, and thus the phase of the distributed generation output current.

[0080] Figure 4 This is a schematic diagram of a distribution network line containing distributed power sources. Figure 5 This is a schematic diagram of a composite sequence network. (Example:) Figure 4As shown in Figure 5, taking the fault at point f as an example, the equations for the positive sequence voltages at the grid connection points N, T, and P of the distributed power source are as follows. Solving the equations will yield the phase of the positive sequence voltage at the grid connection point:

[0081]

[0082]

[0083]

[0084] Where, the positive sequence impedance equals the negative sequence impedance, Z Σ(1) Z represents the positive sequence impedance. X-Y Z represents the impedance of the line connecting busbar X and busbar Y. S The internal impedance of the power source in the power system. They are respectively Figure 5 The output current of the three distributed power sources shown.

[0085] Using the above method, the phase of the distributed power source output current can be solved by establishing equations based on the positive sequence voltage of the distributed power source grid-connected bus in the composite sequence network.

[0086] In one embodiment, the second short-circuit current includes: a second three-phase short-circuit current I. k (3) The second phase B short-circuit current I kB (2) and the second phase C short-circuit current I kC (2) S104 specifically includes:

[0087] The second three-phase short-circuit current I is determined based on the first three-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, and the phase. k (3) ;

[0088] Specifically, the second and third phase short-circuit currents I k (3) The expression is as follows:

[0089]

[0090] The second phase B short-circuit current I is determined based on the first phase B short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, the third fault short-circuit ratio, and the phase. kB (2) ;

[0091] Specifically, the second phase B short-circuit current I kB (2) The expression is as follows:

[0092]

[0093] The second phase C short-circuit current I is determined based on the first phase C short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, the third fault short-circuit ratio, and the phase. kC (2) ;

[0094] Specifically, the short-circuit current I of the second C phase kC (2) The expression is as follows:

[0095]

[0096] in, θ 11 θ 12 θ2 and θ2 are the phase differences between the output current of the distributed power source at the grid connection location before and after the fault location, the grid connection location before and after the fault location, the grid connection location before the fault location, and the fault location, respectively, and the phase difference between the current flowing through the fault line when no distributed power source is connected. k1 is the per-unit value of the distributed power source output current (based on the rated current of the distributed power source). The rotation factor e jθ =cosθ+jsinθ, meaning: any complex number multiplied by e jθ Multiplying a complex number by j is equivalent to rotating the complex number counterclockwise by an angle θ, where j is the imaginary unit. Multiplying a complex number by j is equivalent to rotating the complex number counterclockwise by 90°.

[0097] For a line with known line parameters, fault type, fault location, distributed power source access location and capacity, based on the short-circuit current of the grid without distributed power source determined by S101, the magnitude of the fault short-circuit ratio determined by S101, and the phase of the distributed power source output current determined by S101, the short-circuit current of the grid with distributed power source can be calculated according to the above formulas (13), (14) and (15).

[0098] In S105, the sensitivity of the current protection is expressed by the sensitivity coefficient K. sen The sensitivity coefficient is measured by the ratio of the short-circuit current at the end of the line when a two-phase short circuit occurs to the protection setting value.

[0099]

[0100] Among them, I set It is the setting value of the current protection.

[0101] Therefore, the sensitivity of the current protection can be evaluated based on the traditional current protection setting and the magnitude of the short-circuit current under distributed power supply access calculated by S104.

[0102] Based on the same inventive concept, this application also provides a distribution network current protection sensitivity analysis device, which can be used to implement the method described in the above embodiments, as shown in the following embodiments. Since the principle of the distribution network current protection sensitivity analysis device in solving the problem is similar to that of the distribution network current protection sensitivity analysis method, the implementation of the distribution network current protection sensitivity analysis device can refer to the implementation of the distribution network current protection sensitivity analysis method, and repeated details will not be elaborated further. As used below, the terms "unit" or "module" can refer to a combination of software and / or hardware that performs a predetermined function. Although the system described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0103] Figure 6 This is a schematic diagram of the distribution network current protection sensitivity analysis device according to an embodiment of this application, as shown below. Figure 6 As shown, the distribution network current protection sensitivity analysis device includes: a current and capacity acquisition unit 601, a fault short-circuit ratio determination unit 602, a phase determination unit 603, a short-circuit current determination unit 604, and a sensitivity evaluation unit 605.

[0104] The current and capacity acquisition unit 601 is used to obtain the first short-circuit current and system short-circuit capacity when no distributed power source is connected to the power system, based on the distribution network parameters.

[0105] The fault short-circuit ratio determination unit 602 is used to determine the fault short-circuit ratio based on the relative relationship between the grid connection location of the distributed power source and the current measurement point location and the fault location in the power system.

[0106] The phase determination unit 603 is used to calculate the phase of the distributed power source output current based on the power system phase voltage, positive and negative sequence short-circuit impedance, line impedance, the magnitude of the distributed power source output current, the line impedance between buses, and the line impedance angle when the distributed power source adopts the optimal positive sequence voltage support strategy.

[0107] The short-circuit current determination unit 604 is used to determine the second short-circuit current when the distributed power source is connected to the power system based on the first short-circuit current, the fault short-circuit ratio and the phase.

[0108] The sensitivity evaluation unit 605 is used to evaluate the sensitivity of the current protection based on the current protection setting value and the second short-circuit current.

[0109] In one embodiment, such as Figure 7 As shown, the power distribution network parameters include the power system phase voltage and short-circuit loop impedance; the first short-circuit current includes the first three-phase short-circuit current, the first B-phase short-circuit current, and the first C-phase short-circuit current; the current and capacity acquisition unit 601 includes:

[0110] The first three-phase short-circuit current calculation module 701 is used to calculate the first three-phase short-circuit current based on the phase voltage and short-circuit loop impedance of the power system.

[0111] The BC phase short-circuit current determination module 702 is used to calculate the first B phase short-circuit current and the first C phase short-circuit current based on the phase voltage and short-circuit loop impedance of the power system.

[0112] The system short-circuit capacity determination module 703 is used to calculate the system short-circuit capacity based on the first three-phase short-circuit current and the normal operating voltage at the short-circuit point.

[0113] In one embodiment, such as Figure 8 As shown, the BC phase short-circuit current determination module 702 includes:

[0114] The positive sequence current determination submodule 801 is used to calculate the positive sequence current based on the phase voltage and short-circuit loop impedance of the power system.

[0115] The BC phase short-circuit current calculation module 802 is used to calculate the first B phase short-circuit current and the first C phase short-circuit current based on the positive sequence current.

[0116] In one embodiment, the fault short-circuit ratio determination unit 602 is specifically used to: determine the fault short-circuit ratio based on the system short-circuit capacity, the rated capacity of the distributed power source corresponding to the relative relationship, the rated output current of the distributed power source corresponding to the relative relationship, the first three-phase short-circuit current, and the positive sequence current.

[0117] In one embodiment, the fault short-circuit ratio includes:

[0118] The first fault short-circuit ratio, wherein the grid connection location is before the current measurement point location and the fault location;

[0119] The second fault short-circuit ratio, the grid connection position is before the fault position and after the current measurement point position;

[0120] The third fault short-circuit ratio, the grid connection position is after the current measurement point and the fault location.

[0121] In one embodiment, such as Figure 9 As shown, the phase determination unit 603 includes:

[0122] The first phase calculation module 901 is used to calculate the phase of the distributed power generation grid-connected bus voltage based on the power system phase voltage, positive and negative sequence short-circuit impedance, line impedance, distributed power generation output current and line impedance between buses.

[0123] The second phase calculation module 902 is used to calculate the phase of the output current of the distributed power source based on the phase of the grid-connected bus voltage of the distributed power source and the line impedance angle.

[0124] In one embodiment, such as Figure 10 As shown, the short-circuit current determination unit 604 includes:

[0125] Three-phase short-circuit current determination module 1001 is used to determine the second three-phase short-circuit current based on the first three-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio and the phase.

[0126] The B-phase short-circuit current determination module 1002 is used to determine the second B-phase short-circuit current based on the first B-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, the third fault short-circuit ratio, and the phase.

[0127] The C-phase short-circuit current determination module 1003 is used to determine the second C-phase short-circuit current based on the first C-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, the third fault short-circuit ratio, and the phase.

[0128] In one embodiment, the sensitivity evaluation unit 605 is specifically used to: determine the sensitivity coefficient based on the second short-circuit current and the current protection setting value.

[0129] The following specific embodiments illustrate the sensitivity analysis method for distribution network current protection of this application. The voltage level of the distribution network is 10kV, the internal impedance is Zs=j7Ω, the line parameters are (0.27+j0.391)Ω / km, and the lengths of each line segment are as follows: Figure 11 As shown; the capacities of distributed power sources 1-4 are 4MVA, 2MVA, 1MVA, and 2MVA, respectively; the sensitivity of protection 2 and protection 3 is evaluated, and the setting values ​​of instantaneous overcurrent protection and time-limited overcurrent protection of protection 2 and protection 3 are shown in Table 1.

[0130] Table 1 Current protection setting values

[0131]

[0132]

[0133] When a three-phase short circuit and a two-phase short circuit (BC) occur at the end of the lines protected by Protection 2 and Protection 3, the current flowing through the protection is calculated according to the method of this application, and the sensitivity coefficient of the current protection stage II is calculated. The results calculated using the fault short-circuit ratio in this application are compared with the results of computer iteration, as shown in Table 2. Ignoring manual calculation errors, the method of evaluating the sensitivity of current protection using the fault short-circuit ratio index has an accuracy of almost 100%.

[0134] Table 2 compares the results of manual and iterative calculations using the fault-short-circuit ratio index.

[0135]

[0136] This application draws on the successful application of the short-circuit ratio in power systems. Starting from the relative relationship between the grid connection location of distributed generation sources and the location of current measurement points and fault locations, it proposes a method for evaluating the sensitivity of distribution network current protection based on the fault short-circuit ratio index. This method has the following advantages: The fault short-circuit ratio index allows for a direct understanding of the factors influencing the magnitude of short-circuit current or the sensitivity of current protection in a power grid containing distributed generation sources. These factors include the relative relationship between the grid connection location of distributed generation sources and the location of current measurement points and fault locations, the capacity of the distributed generation sources, and the phase of the output current. Furthermore, by utilizing the short-circuit current calculation method related to the fault short-circuit ratio when distributed generation sources are connected to the power system, the magnitude of the short-circuit current can be determined without iterative calculations using a computer, thus enabling the evaluation of the sensitivity of current protection.

[0137] For ease of description, the above devices are described separately by function as various units. Of course, in implementing this application, the functions of each unit can be implemented in one or more software and / or hardware.

[0138] 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, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0139] These 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 function 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 function specified in one or more boxes.

[0140] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0141] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0142] 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-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0143] This application can be described in the general context of computer-executable instructions, such as program modules, that are executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform a specific task or implement a specific abstract data type. This application can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.

[0144] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0145] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for analyzing the sensitivity of distribution network current protection, characterized in that, include: The first short-circuit current and system short-circuit capacity when no distributed power source is connected to the power system are obtained based on the distribution network parameters. The fault short-circuit ratio is determined based on the relative relationship between the grid connection location of the distributed generation and the current measurement point location and the fault location in the power system. The fault short-circuit ratio includes: a first fault short-circuit ratio, a second fault short-circuit ratio, and a third fault short-circuit ratio. The first fault short-circuit ratio corresponds to the grid connection location being before the current measurement point location and the fault location. The second fault short-circuit ratio corresponds to the grid connection location being before the fault location and after the current measurement point location. The third fault short-circuit ratio corresponds to the grid connection location being after the current measurement point location and the fault location. The first fault short-circuit ratio is determined based on the system short-circuit capacity and the rated capacity of the distributed power source at the grid-connected location corresponding to the first fault short-circuit ratio; the second fault short-circuit ratio is determined based on the system short-circuit capacity and the rated capacity of the distributed power source at the grid-connected location corresponding to the second fault short-circuit ratio; the third fault short-circuit ratio is determined based on the system short-circuit capacity and the rated capacity of the distributed power source at the grid-connected location corresponding to the third fault short-circuit ratio. When the distributed generation adopts the optimal positive sequence voltage support strategy, the phase of the distributed generation output current is calculated based on the power system phase voltage, positive and negative sequence short-circuit impedance, line impedance, the magnitude of the distributed generation output current, the line impedance between buses, and the line impedance angle. The second short-circuit current when the distributed power source is connected to the power system is determined based on the first short-circuit current, the fault short-circuit ratio, and the phase. The sensitivity of the current protection is evaluated based on the current protection setting value and the second short-circuit current.

2. The method for analyzing the sensitivity of distribution network current protection according to claim 1, characterized in that, The distribution network parameters include the power system phase voltage and short-circuit loop impedance; the first short-circuit current includes the first three-phase short-circuit current, the first B-phase short-circuit current, and the first C-phase short-circuit current; obtaining the first short-circuit current and system short-circuit capacity when there is no distributed power source connected to the power system based on the distribution network parameters includes: Calculate the first three-phase short-circuit current based on the phase voltage and short-circuit loop impedance of the power system; Calculate the first phase B short-circuit current and the first phase C short-circuit current based on the phase voltage and short-circuit loop impedance of the power system. The system short-circuit capacity is calculated based on the first three-phase short-circuit current and the normal operating voltage at the short-circuit point.

3. The method for analyzing the sensitivity of distribution network current protection according to claim 2, characterized in that, The calculation of the first phase B short-circuit current and the first phase C short-circuit current based on the phase voltage and short-circuit loop impedance of the power system includes: Calculate the positive sequence current based on the phase voltage and short-circuit loop impedance of the power system. Calculate the first phase B short-circuit current and the first phase C short-circuit current based on the positive sequence current.

4. The method for analyzing the sensitivity of distribution network current protection according to claim 3, characterized in that, The determination of the fault short-circuit ratio based on the relative relationship between the grid connection location of the distributed generation in the power system, the location of the current measurement point, and the fault location includes: The fault short-circuit ratio is determined based on the system short-circuit capacity, the rated capacity of the distributed power source corresponding to the relative relationship, the rated output current of the distributed power source corresponding to the relative relationship, the first three-phase short-circuit current, and the positive sequence current.

5. The method for analyzing the sensitivity of distribution network current protection according to claim 4, characterized in that, When distributed generation adopts the optimal positive-sequence voltage support strategy, the phase of the distributed generation output current is calculated based on the power system phase voltage, positive and negative sequence short-circuit impedance, line impedance, the magnitude of the distributed generation output current, the line impedance between buses, and the line impedance angle. This includes: The phase of the distributed generation grid-connected bus voltage is calculated based on the phase voltage of the power system, the positive and negative sequence short-circuit impedance, the line impedance, the output current of the distributed generation, and the line impedance between the buses. The phase of the distributed power source output current is calculated based on the phase of the distributed power source grid-connected bus voltage and the line impedance angle.

6. The method for analyzing the sensitivity of distribution network current protection according to claim 4, characterized in that, The current protection sensitivity assessment based on the current protection setting value and the second short-circuit current includes: The sensitivity coefficient is determined based on the second short-circuit current and the current protection setting value.

7. A distribution network current protection sensitivity analysis device, characterized in that, include: The current and capacity acquisition unit is used to obtain the first short-circuit current and system short-circuit capacity when no distributed power source is connected to the power system, based on the distribution network parameters. The fault short-circuit ratio determination unit is used to determine the fault short-circuit ratio based on the relative relationship between the grid connection location of the distributed power source and the current measurement point location and the fault location in the power system; wherein, the fault short-circuit ratio includes: a first fault short-circuit ratio, a second fault short-circuit ratio, and a third fault short-circuit ratio; the first fault short-circuit ratio corresponds to the grid connection location being before the current measurement point location and the fault location; the second fault short-circuit ratio corresponds to the grid connection location being before the fault location and after the current measurement point location; the third fault short-circuit ratio corresponds to the grid connection location being after the current measurement point location and the fault location. The first fault short-circuit ratio is determined based on the system short-circuit capacity and the rated capacity of the distributed power source at the grid-connected location corresponding to the first fault short-circuit ratio; the second fault short-circuit ratio is determined based on the system short-circuit capacity and the rated capacity of the distributed power source at the grid-connected location corresponding to the second fault short-circuit ratio; the third fault short-circuit ratio is determined based on the system short-circuit capacity and the rated capacity of the distributed power source at the grid-connected location corresponding to the third fault short-circuit ratio. The phase determination unit is used to calculate the phase of the distributed generation output current based on the power system phase voltage, positive and negative sequence short-circuit impedance, line impedance, the magnitude of the distributed generation output current, the line impedance between buses, and the line impedance angle when the distributed generation adopts the optimal positive sequence voltage support strategy. A short-circuit current determination unit is used to determine a second short-circuit current when a distributed power source is connected to the power system based on the first short-circuit current, the fault short-circuit ratio, and the phase. The sensitivity evaluation unit is used to evaluate the sensitivity of the current protection based on the current protection setting value and the second short-circuit current.

8. The distribution network current protection sensitivity analysis device according to claim 7, characterized in that, The power distribution network parameters include the power system phase voltage and short-circuit loop impedance, and the first short-circuit current includes the first three-phase short-circuit current, the first B-phase short-circuit current and the first C-phase short-circuit current. The current and capacity acquisition unit includes: The first three-phase short-circuit current calculation module is used to calculate the first three-phase short-circuit current based on the phase voltage and short-circuit loop impedance of the power system. The BC phase short-circuit current determination module is used to calculate the first B phase short-circuit current and the first C phase short-circuit current based on the phase voltage and short-circuit loop impedance of the power system. The system short-circuit capacity determination module is used to calculate the system short-circuit capacity based on the first three-phase short-circuit current and the normal operating voltage at the short-circuit point.

9. The distribution network current protection sensitivity analysis device according to claim 8, characterized in that, The BC phase short-circuit current determination module includes: The positive sequence current determination submodule is used to calculate the positive sequence current based on the phase voltage and short-circuit loop impedance of the power system. The BC phase short-circuit current calculation module is used to calculate the first B phase short-circuit current and the first C phase short-circuit current based on the positive sequence current.

10. The distribution network current protection sensitivity analysis device according to claim 9, characterized in that, The fault short-circuit ratio determination unit is specifically used for: The fault short-circuit ratio is determined based on the system short-circuit capacity, the rated capacity of the distributed power source corresponding to the relative relationship, the rated output current of the distributed power source corresponding to the relative relationship, the first three-phase short-circuit current, and the positive sequence current.

11. The distribution network current protection sensitivity analysis device according to claim 10, characterized in that, The phase determination unit includes: The first phase calculation module is used to calculate the phase of the distributed generation grid-connected bus voltage based on the power system phase voltage, positive and negative sequence short-circuit impedance, line impedance, distributed generation output current and line impedance between buses; The second phase calculation module is used to calculate the phase of the output current of the distributed power source based on the phase of the grid-connected bus voltage of the distributed power source and the line impedance angle.

12. The distribution network current protection sensitivity analysis device according to claim 10, characterized in that, The sensitivity evaluation unit is specifically used to determine the sensitivity coefficient based on the second short-circuit current and the current protection setting value.

13. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the method as described in any one of claims 1-6.

14. A computer-readable medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in any one of claims 1-6.

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