Method and apparatus for determining fault location in power distribution system on basis of dual-criterion protection

Abstract

Provided in the present disclosure are a method and apparatus for determining the fault location in a power distribution system on the basis of dual-criterion protection. The method comprises: acquiring related electrical quantities of a power distribution system; when it is determined, on the basis of a distributed new energy grid-connection point voltage and a startup threshold value, that a fault has occurred, determining a T-connected load line opposite-side virtual voltage on the basis of a post-fault T-connected load line side voltage, a post-fault T-connected load line side current and the related electrical quantities, and determining a first protection criterion on the basis of the T-connected load line opposite-side virtual voltage, a T-connected load line actual-virtual voltage difference value and the related electrical quantities; controlling distributed new energy to inject high-frequency harmonics into a T-connected load line, and determining a second protection criterion on the basis of a T-connected load line high-frequency current; and on the basis of the first protection criterion and the second protection criterion, determining the fault location in the power distribution system. By constructing dual criteria, the present disclosure solves the problem of limited usage scenarios of existing active detection protection schemes for alternating current systems with distributed new energy.

Description

Method and device for determining fault location of power distribution system based on double criterion protection

[0001] The present disclosure claims priority to the Chinese patent application No. 2024106116363, filed on May 16, 2024, and entitled "Method and device for determining fault location of power distribution system based on double criterion protection", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of determining fault location of power distribution system, and in particular, to a method, device, storage medium and electronic equipment for determining fault location of power distribution system based on double criterion protection. BACKGROUND

[0003] With the depletion of fossil energy and the intensification of environmental challenges, the development and utilization of new energy has become a necessary condition to achieve the "double carbon" goal. China is actively cultivating new power distribution systems in which distributed generation (DG) plays a key role. For example, the output characteristics of the mainstream inverter technology in distributed power sources are different from traditional power sources. Influenced by external factors and control strategies, the output characteristics exhibit volatility, intermittency and nonlinearity. Therefore, the power distribution network has undergone a transformation from the traditional single-source radial power grid to the multi-source grid-connected power grid. In addition, as the DG access capacity increases, the power grid structure becomes increasingly complex, and the penetration rate of T-type DG and T-type load in the power distribution network is rising. The traditional power distribution network usually adopts a three-level current protection system as its main defense mechanism. However, the introduction of distributed generation (DG) changes the short-circuit current level and distribution path, resulting in a significant decrease in the sensitivity and reliability of current protection.

[0004] Several enhancement schemes based on adaptive algorithms have been proposed by domestic and foreign scholars. For example, an adaptive current protection setting method considering the real-time output of upstream DG is introduced. However, the setting of adaptive algorithms in high DG access scenarios is complex, and their protection performance needs to be verified. In addition, double-end protection, as a commonly used primary protection in transmission networks, is introduced into DG-containing power distribution networks due to its fast speed and good selectivity. A domestic research team proposed an enhanced double-end protection scheme that utilizes the amplitude of the current at both ends and the equivalent impedance outside the line. Another team introduced an active power distribution network double-end protection scheme based on the amplitude and phase characteristics of the positive sequence fault component of the current at both ends. However, it is important to note that the applicability of the above methods is limited to scenarios where DG is connected to the grid through a bus. For power distribution networks with T-type access lines, a foreign team proposed a virtual multi-end current differential protection scheme based on fault current. However, in the presence of T-type load branches in the region, there is a sensitivity to false tripping in external fault scenarios.

[0005] With the continuous improvement of power electronic equipment level, active detection fault identification method enters the scientific research field. In the case of power grid disturbance, the power electronic equipment is controlled to actively emit characteristic electric quantity for fault detection, and then the protection device forms a criterion according to the difference of the injected fault electric quantity, so as to realize fault discrimination. This kind of technical idea has made great progress in the research of DC system fault detection, positioning and reclosing, however, the current active detection protection scheme for DG AC system is limited to specific scenarios such as island microgrid and centralized photovoltaic power station transmission line, and further exploration and application are needed.

[0006] SUMMARY

[0007] The main purpose of the present disclosure is to provide a method, device, storage medium and electronic equipment for determining the fault position of a power distribution system based on double criterion protection, so as to at least solve the problem that the current active detection protection scheme for DG AC system is limited in use scenarios.

[0008] In order to achieve the above purpose, according to one aspect of the present disclosure, a method for determining the fault position of a power distribution system based on double criterion protection is provided, the method is applied to a controller of a power distribution system, the power distribution system further comprises a distributed new energy and load T connection line connected by electricity, comprising: obtaining relevant electrical quantities of the power distribution system, wherein the relevant electrical quantities include distributed new energy grid-connected point voltage, distributed new energy grid-connected point current, load T connection line side voltage, load T connection line grid-connected point voltage, load T connection line grid-connected point current, load T connection line side current, and equivalent impedance of each section of the load T connection line; determining whether a fault occurs according to the size relationship between the distributed new energy grid-connected point voltage and a start threshold value, and obtaining the post-fault load T connection line side voltage and the post-fault load T connection line side current after a preset time period of the fault occurrence in the case of determining that the fault occurs, wherein the start threshold value is related to the distributed new energy grid-connected point rated voltage; determining the opposite side virtual voltage of the load T connection line according to the post-fault load T connection line side voltage, the post-fault load T connection line side current and the relevant electrical quantities, and determining the first protection criterion according to the opposite side virtual voltage of the load T connection line, the real and virtual voltage difference of the load T connection line and the relevant electrical quantities; controlling the distributed new energy to inject high-frequency harmonics into the load T connection line, obtaining the high-frequency current of the load T connection line, and determining the second protection criterion according to the high-frequency current of the load T connection line; and determining the fault position of the power distribution system according to the first protection criterion and the second protection criterion.

[0009] Optionally, the related electrical quantity of the power distribution system is acquired, and the acquiring of the distributed new energy grid-connected point voltage and the distributed new energy grid-connected point current comprises: determining the distributed new energy grid-connected point voltage and the distributed new energy grid-connected point current according to the load T connection line side voltage, the load T connection line grid-connected point voltage, the load T connection line side current, the load T connection line grid-connected point current, and the equivalent impedance of each section of the load T connection line and the current corresponding to the equivalent impedance of each section of the load T connection line.

[0010] Optionally, the determination of whether the fault occurs according to the size relationship between the distributed new energy grid-connected point voltage and the starting threshold value comprises: determining that the fault occurs and starting protection in the case that min{|u PCC |}≤ρ. PCC |} represents the absolute value of the minimum value of the distributed new energy grid-connected point voltage, and ρ represents the protection starting threshold value.

[0011] Optionally, the first protection criterion is determined according to the load T connection line opposite side virtual voltage, the load T connection line real and virtual voltage difference, and the related electrical quantity, which comprises: determining the load T connection line one side real and virtual voltage difference D M (x) according to the load T connection line one side virtual voltage and the load T connection line one side actual voltage; determining the load T connection line other side real and virtual voltage difference D N (x) according to the load T connection line other side virtual voltage and the load T connection line other side actual voltage; constructing a first function and a second function according to the related electrical quantity, and determining the vertical coordinate value of the intersection point of the first function and the second function as a fault threshold value D set , wherein the first function is a high-frequency voltage function of the load T connection line one side with respect to the fault position, and the second function is a high-frequency voltage function of the load T connection line other side with respect to the fault position; determining the first protection criterion according to D M (x), D N (x) and D set . r1 =D M (x)>D set ∪D N (x)>D set .

[0012] Optionally, the distributed new energy is controlled to inject a high-frequency harmonic wave into the load T connection line, the load T connection line high-frequency current is acquired, and the second protection criterion is determined according to the load T connection line high-frequency current, which comprises: controlling the distributed new energy to inject N times of the high-frequency harmonic wave into the load T connection line, wherein N is an integer greater than 1; and measuring the load T connection line one side high-frequency current after the injection of N times of the high-frequency harmonic wave. and the high frequency current on the other side of the load T connection according to the high frequency current on the one side of the load T connection the high frequency current on the other side of the load T connection and the external fault parameter k determined according to the high frequency harmonic out ; according to the external fault parameter k out and the high frequency harmonic determining a fault current threshold I Kset ; according to the fault current threshold I Kset , the high frequency current on the one side of the load T connection and the high frequency current on the other side of the load T connection determining the second protection criterion as

[0013] Optionally, determining the fault location of the power distribution system according to the first protection criterion and the second protection criterion comprises: determining C r1 ∪C r2 whether equal to 1 or equal to 0; in the case of determining equal to 1, determining the fault as an internal fault, and in the case of determining equal to 0, determining the fault as an external fault.

[0014] Optionally, after determining the fault location according to the first protection criterion and the second protection criterion, the method further comprises: generating fault alarm information according to the determined fault location, the fault alarm information indicating that the fault location is an external fault or an internal fault.

[0015] According to another aspect of the present disclosure, there is provided an apparatus for determining a fault location of a power distribution system based on double criterion protection, which is applied to a controller of the power distribution system further comprising a distributed new energy and load T connection line connected electrically, comprising: a first acquisition unit configured to acquire relevant electrical quantities of the power distribution system, wherein the relevant electrical quantities comprise a distributed new energy grid-connected point voltage, a distributed new energy grid-connected point current, a load T connection line side voltage, a load T connection line grid-connected point voltage, a load T connection line grid-connected point current, a load T connection line side current, and equivalent impedances of each segment of the load T connection line; a second acquisition unit configured to determine whether a fault occurs according to a size relationship between the distributed new energy grid-connected point voltage and a start threshold value, and in a case where it is determined that a fault occurs, acquire a post-fault load T connection line side voltage and a post-fault load T connection line side current after a preset time period of the fault occurrence, wherein the start threshold value is related to a distributed new energy grid-connected point rated voltage; a first determination unit configured to determine a load T connection line opposite side virtual voltage according to the post-fault load T connection line side voltage, the post-fault load T connection line side current, and the relevant electrical quantities, and determine a first protection criterion according to the load T connection line opposite side virtual voltage, a load T connection line real and virtual voltage difference, and the relevant electrical quantities; a control unit configured to control the distributed new energy to inject a high-frequency harmonic wave into the load T connection line, acquire a load T connection line high-frequency current, and determine a second protection criterion according to the load T connection line high-frequency current; and a second determination unit configured to determine the fault location of the power distribution system according to the first protection criterion and the second protection criterion.

[0016] According to still another aspect of the present disclosure, there is provided a computer-readable storage medium comprising a stored program, wherein the computer-readable storage medium is caused to perform any one of the methods for determining a fault location of a power distribution system based on double criterion protection when the program is run.

[0017] According to yet another aspect of the present disclosure, there is provided an electronic device comprising one or more processors, memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs comprise a program for performing any one of the methods for determining a fault location of a power distribution system based on double criterion protection.

[0018] The technical scheme of the present disclosure is applied to obtain relevant electrical quantities of a power distribution system, wherein the relevant electrical quantities include distributed new energy grid-connected point voltage, distributed new energy grid-connected point current, load T connection line side voltage, load T connection line grid-connected point voltage, load T connection line grid-connected point current, load T connection line side current, and load T connection line section equivalent impedance; whether a fault occurs is determined according to the size relationship between the distributed new energy grid-connected point voltage and a starting threshold value, and in the case where it is determined that a fault occurs, post-fault load T connection line side voltage and post-fault load T connection line side current after a preset time period of the fault occurrence are obtained, wherein the starting threshold value is related to a distributed new energy grid-connected point rated voltage; load T connection line opposite side virtual voltage is determined according to the post-fault load T connection line side voltage, the post-fault load T connection line side current and the relevant electrical quantities, a first protection criterion is determined according to the load T connection line opposite side virtual voltage, a load T connection line real-virtual voltage difference and the relevant electrical quantities; a high-frequency harmonic is injected into the load T connection line by the distributed new energy, a load T connection line high-frequency current is obtained, and a second protection criterion is determined according to the load T connection line high-frequency current; and the fault position of the power distribution system is determined according to the first protection criterion and the second protection criterion. Based on the idea of control and protection cooperation, the double criterion is constructed by combining the differential characteristics of the real-virtual voltage difference and the high-frequency injected current, the problem that the current active detection protection scheme for the DG AC system containing distributed new energy is limited in use scene is solved, and the double criterion is not affected by the fault type, the fault position, the transition resistance size and the like, and has good reliability. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings, which form a part of the present disclosure, are used to provide further understanding of the present disclosure, and the illustrative embodiments of the present disclosure and their descriptions are used to explain the present disclosure, and do not constitute improper limitations on the present disclosure. In the drawings:

[0020] FIG. 1 shows a hardware structure block diagram of a mobile terminal for performing a method of determining a fault position of a power distribution system based on double criterion protection according to an embodiment of the present disclosure;

[0021] FIG. 2 shows a flowchart of a method of determining a fault position of a power distribution system based on double criterion protection according to an embodiment of the present disclosure;

[0022] FIG. 3 shows a power distribution network line diagram containing a T-connected DG and a load according to an embodiment of the present disclosure;

[0023] FIG. 4 shows a step flowchart of a specific method of determining a fault position of a power distribution system based on double criterion protection according to an embodiment of the present disclosure;

[0024] FIG. 5 shows an equivalent circuit diagram of a DG line according to an embodiment of the present disclosure;

[0025] FIG. 6 shows a line fault equivalent circuit diagram between M and a DG point of grid connection provided according to an embodiment of the present disclosure;

[0026] FIG. 7 shows a line fault equivalent circuit diagram between a DG point of grid connection and a T-connected load provided according to an embodiment of the present disclosure;

[0027] FIG. 8 shows a line fault equivalent circuit diagram between a T-connected load and N provided according to an embodiment of the present disclosure;

[0028] FIG. 9 shows a size relationship diagram between D M (x), D N (x), T M (x), T N (x);

[0029] FIG. 10 shows a function diagram of k in and k out about the size of the T-connected load capacity;

[0030] FIG. 11 shows a structural block diagram of an apparatus for determining a fault location of a power distribution system based on a double-criterion protection provided according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0031] It should be noted that the embodiments and features in the present disclosure can be combined with each other without conflict. The present disclosure will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0032] In order to enable persons skilled in the art to better understand the present disclosure scheme, the technical solutions in the embodiments of the present disclosure will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, not all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by persons skilled in the art without creative labor should belong to the scope of protection of the present disclosure.

[0033] It should be noted that the terms "first", "second", and the like in the specification and claims of the present disclosure and the above-described drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present disclosure described herein can be implemented. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0034] For the convenience of description, the following describes some nouns or terms related to the embodiments of the present disclosure:

[0035] Distributed new energy and load T connection line: a common connection method in power systems, used to connect distributed new energy and load to the grid, T connection line is usually composed of transformers, switching devices and protection devices, which can realize the access and shunt of new energy and load, the design of T connection line can realize the parallel connection of new energy and load, so as to realize the power supply to the grid, in this connection mode, new energy can directly supply power to load, or supply power to grid, so as to realize the flexible utilization and distribution of energy. The design of T connection line needs to consider the stability of new energy and the safety of power grid, to ensure that the access of new energy will not cause overload or other adverse effects to the power grid, at the same time, T connection line also needs to consider the demand and change of load, to ensure that distributed new energy can meet the load demand, in general, T connection line is a flexible and reliable connection method, which can effectively integrate distributed new energy and load, realize effective power supply to the grid, and promote the utilization and development of new energy.

[0036] As introduced in the background, the existing active detection protection scheme for DG AC system has a small use scene. To solve the problem that the use scene of the existing active detection protection scheme for DG AC system is limited, the embodiments of the present disclosure provide a method and device for determining fault location of a power distribution system based on double criterion protection, a storage medium and an electronic device.

[0037] The technical solutions in the embodiments of the present disclosure will be described clearly and completely in combination with the drawings in the embodiments of the present disclosure.

[0038] The method embodiments provided in the embodiments of the present disclosure can be executed in a mobile terminal, a computer terminal or a similar computing device. Taking the case of running on a mobile terminal, Fig. 1 is a hardware structure block diagram of a mobile terminal of a method for determining fault location of a power distribution system based on double criterion protection according to an embodiment of the present disclosure. As shown in Fig. 1, the mobile terminal can include one or more (only one is shown in Fig. 1) processors 102 (the processor 102 can include but is not limited to a processing device such as a microprocessor MCU or a programmable logic device FPGA) and a memory 104 for storing data, wherein the mobile terminal can further include a transmission device 106 for communication function and an input and output device 108. Those skilled in the art can understand that the structure shown in Fig. 1 is only schematic, which does not limit the structure of the mobile terminal. For example, the mobile terminal can include more or fewer components than those shown in Fig. 1, or have a different configuration from that shown in Fig. 1.

[0039] The memory 104 can be used to store computer programs, such as software programs of application software and modules, such as a computer program corresponding to the method for determining a fault location of a power distribution system based on double-criterion protection according to an embodiment of the present application. The processor 102 can execute various functional applications and data processing, i.e., implement the above method, by running the computer program stored in the memory 104. The memory 104 can include a high-speed random access memory, and can further include a non-volatile memory, such as one or more magnetic storage devices, flash memories, or other non-volatile solid-state memories. In some examples, the memory 104 can further include memories remotely arranged with respect to the processor 102, which can be connected to the mobile terminal through a network. Examples of the network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof. The transmission device 106 is used to receive or send data via a network. The specific examples of the network can include a wireless network provided by a communication provider of the mobile terminal. In one example, the transmission device 106 includes a network adapter (NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 106 can be a radio frequency (RF) module, which is used to communicate with the Internet in a wireless manner.

[0040] In the present embodiment, a method for determining a fault location of a power distribution system based on double-criterion protection is provided, which is run on a mobile terminal, a computer terminal, or a similar computing device. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0041] FIG. 2 is a flowchart of a method for determining a fault location of a power distribution system based on double-criterion protection according to an embodiment of the present disclosure. As shown in FIG. 2, the above method is applied to a controller of a power distribution system, which further includes a distributed new energy and load T connection line electrically connected. The method includes the following steps:

[0042] In step S201, relevant electrical quantities of the power distribution system are obtained, wherein the relevant electrical quantities include a distributed new energy grid-connected point voltage, a distributed new energy grid-connected point current, a load T connection line side voltage, a load T connection line grid-connected point voltage, a load T connection line grid-connected point current, a load T connection line side current, and equivalent impedances of each segment of the load T connection line.

[0043] The power distribution system including the distributed new energy DG and the load T connection line is shown in FIG. 3.

[0044] Step S202, according to the size relationship between the distributed new energy grid-connected point voltage and the starting threshold value, determine whether the fault occurs, in the case of determining the fault occurs, get the fault after load T line side voltage and fault after load T line side current after the preset time period, wherein the starting threshold value is related to the distributed new energy grid-connected point rated voltage;

[0045] Among them, the preset time period can be selected as 2ms, 5ms, 10ms, in order to take into account the protection of the speed and accuracy, the preset time period is generally taken as 5ms.

[0046] Specifically, in the case of determining that the minimum absolute value of the distributed new energy grid-connected point voltage is less than the starting threshold value, it is considered that the fault occurs, and the protection is started, and the fault after load T line side voltage and the fault after load T line side current are obtained after 5ms of the fault, wherein in order to ensure the sensitivity of the protection, the starting threshold value is generally taken as 90% of the rated voltage of the grid-connected point.

[0047] Step S203, according to the fault after load T line side voltage, the fault after load T line side current and the related electrical quantity, determine the virtual voltage of the load T line opposite side, according to the virtual voltage of the load T line opposite side, the difference value of the actual voltage and the virtual voltage of the load T line, and the related electrical quantity, determine the first protection criterion;

[0048] Specifically, according to the difference value of the actual voltage and the virtual voltage of the load T line, the difference value of the actual voltage and the virtual voltage of the load T line is determined, and then the high frequency voltage function of the load T line on one side about the fault position is constructed according to the related parameters of the distribution system The high frequency voltage function of the load T line on the other side about the fault position Find the y-axis value of the intersection point of the two functions as the fault threshold value, and then get the first protection criterion according to the fault threshold value.

[0049] Step S204, control the distributed new energy to inject high frequency harmonic into the load T line, get the high frequency current of the load T line, and determine the second protection criterion according to the high frequency current of the load T line;

[0050] For example, control the distributed new energy to inject 10 times high frequency harmonic (500Hz) into the load T line, measure the high frequency current flowing through MN on both sides And According to the And the Calculate k in And k out , wherein The high frequency current flowing to the line load, denotes a high-frequency harmonic, and k is an integer out the minimum value in the formula is k set , further denoted as

[0051] Step S205, determining the fault location of the power distribution system according to the first protection criterion and the second protection criterion.

[0052] Specifically, whether it is an internal fault or an external fault can be determined according to the first protection criterion and the second protection criterion.

[0053] Through the embodiment, relevant electrical quantities of the power distribution system are obtained, wherein the relevant electrical quantities include a distributed new energy grid-connected point voltage, a distributed new energy grid-connected point current, a load T connection line side voltage, a load T connection line grid-connected point voltage, a load T connection line grid-connected point current, a load T connection line side current, and equivalent impedances of each section of the load T connection line; whether a fault occurs is determined according to a size relationship between the distributed new energy grid-connected point voltage and a starting threshold value, wherein the starting threshold value is related to a distributed new energy grid-connected point rated voltage; in a case where it is determined that a fault occurs, a post-fault load T connection line side voltage and a post-fault load T connection line side current after a preset time period of the fault occurrence are obtained; a load T connection line opposite side virtual voltage is determined according to the post-fault load T connection line side voltage, the post-fault load T connection line side current, and the relevant electrical quantities; a first protection criterion is determined according to the load T connection line opposite side virtual voltage, a load T connection line real and virtual voltage difference, and the relevant electrical quantities; a high-frequency harmonic is injected into the load T connection line by the distributed new energy, a load T connection line high-frequency current is obtained, and a second protection criterion is determined according to the load T connection line high-frequency current; and the fault location of the power distribution system is determined according to the first protection criterion and the second protection criterion. Based on the idea of coordinated control and protection, the double criteria are constructed by combining the differential characteristics of the real and virtual voltage difference and the high-frequency injected current, thereby solving the problem that the current active detection and protection scheme for the DG AC system has a relatively limited use scene, and the scheme is not affected by the fault type, the fault location, the size of the transition resistance, and the like, and has good reliability.

[0054] In the specific implementation process, the step S201 obtains the relevant electrical quantities of the power distribution system, wherein the distributed new energy grid-connected point voltage and the distributed new energy grid-connected point current are obtained by determining the distributed new energy grid-connected point voltage and the distributed new energy grid-connected point current according to the load T connection line side voltage, the load T connection line grid-connected point voltage, the load T connection line side current, the load T connection line grid-connected point current, the equivalent impedances of each section of the load T connection line, and the currents corresponding to the equivalent impedances of each section of the load T connection line.

[0055] The method determines the first protection criterion according to the formula The first protection criterion is calculated and wherein, denotes the DG point of common coupling voltage, denotes the DG point of common coupling current, is the line M side voltage, is the line N side voltage, is the load point of common coupling voltage, denotes the M side bus current flowing to the line, denotes the N side line current flowing to the bus, Z A , Z B , Z C respectively denote the equivalent impedance of each section of the line, is the current flowing through Z B .

[0056] Specifically, whether a fault occurs is determined according to the size relationship between the distributed new energy point of common coupling voltage and the starting threshold value, including: in the case of min{|u PCC |}≤ρ, it is determined that a fault occurs, and the protection is started, wherein min{|u PCC |} denotes the absolute value of the minimum value of the distributed new energy point of common coupling voltage, and p denotes the protection starting threshold value.

[0057] The method monitors the voltage of the DG point of common coupling in the line in real time, and when min{|u PCC |}≤ρ, the protection is started, wherein in order to ensure the sensitivity of the protection, the starting threshold value is generally taken as 90% of the rated voltage of the point of common coupling.

[0058] More specifically, the first protection criterion is determined according to the virtual voltage on the opposite side of the load T connected line, the actual-virtual voltage difference of the load T connected line, and related electrical quantities, including: the actual-virtual voltage difference D M (x) of the load T connected line on one side is determined according to the virtual voltage on the one side of the load T connected line and the actual voltage on the one side of the load T connected line, and the actual-virtual voltage difference D N (x) of the load T connected line on the other side is determined according to the virtual voltage on the other side of the load T connected line and the actual voltage on the other side of the load T connected line; a first function and a second function are constructed according to the related electrical quantities, and the ordinate value of the intersection point of the first function and the second function is determined as the fault threshold value D set , wherein the first function is the high-frequency voltage function of the load T connected line on one side with respect to the fault position, and the second function is the high-frequency voltage function of the load T connected line on the other side with respect to the fault position; the first protection criterion is determined according to D M (x), D N (x) and D set , and the first protection criterion is C r1 =D M (x)>D set ∪DN (x) > D set .

[0059] The method is respectively according to MN two sides of the virtual voltage Wherein the letter in the subscript bracket indicates which side the virtual voltage is seen from the network end, that is Indicates that the virtual voltage of the opposite side M is calculated by looking into the line from the N side and substituting the electrical quantities of the side looking in. And respectively substitute into formula And Calculate the real and virtual voltage difference, wherein MN side actual voltage measured in step three, D M (x), D N (x) is the function of the real and virtual voltage difference of M and N sides about the location x of the fault in the line, x∈[0,1].

[0060] Further, the distributed new energy is controlled to inject high frequency harmonics into the load T connection line to obtain high frequency current of the load T connection line, and a second protection criterion is determined according to the high frequency current of the load T connection line, comprising: controlling the distributed new energy to inject N times high frequency harmonics into the load T connection line, wherein N is an integer greater than 1; after injecting N times high frequency harmonics, measuring high frequency current And high frequency current of the other side of the load T connection line According to the high frequency current of the one side of the load T connection line And high frequency harmonics, an external fault parameter k out is determined; according to the external fault parameter k out And high frequency harmonics, a fault current threshold I Kset is determined; according to the fault current threshold I Kset , the high frequency current of the one side of the load T connection line And high frequency current of the other side of the load T connection line The second protection criterion is determined as

[0061] The method controls the DG to inject 10 times frequency high frequency harmonics (500Hz) into the line, measures the high frequency current And According to the Under the fault in the area and the Under the fault outside the area, k in And k out Under different load conditions are respectively calculated, wherein for the high frequency current flowing to the line load, denotes the high frequency harmonic, and k out denotes the minimum value in k set , further denoted as

[0062] Further, the fault location of the power distribution system is determined according to the first protection criterion and the second protection criterion, including: determining C r1 ∪C r2 whether it is equal to 1 or equal to 0; in the case of determining that it is equal to 1, determining that the fault is an intra-zone fault, and in the case of determining that it is equal to 0, determining that the fault is an extra-zone fault.

[0063] Specifically, according to the protection criterion , it is judged whether the fault is in the zone or outside the zone, and a protection judgment signal is sent to the protection action unit.

[0064] Specifically, after the fault location is determined according to the first protection criterion and the second protection criterion, the method further includes: generating fault alarm information according to the determined fault location, the fault alarm information indicating that the fault location is an extra-zone fault or an intra-zone fault.

[0065] The method generates fault alarm information indicating the fault location, which can indicate the fault location to the relevant personnel more quickly, so as to solve the fault problem of the power distribution system more quickly.

[0066] In order to enable those skilled in the art to more clearly understand the technical solutions of the present disclosure, the implementation process of the method for determining the fault location of the power distribution system based on the double-criterion protection of the present disclosure will be described in detail below in combination with specific embodiments.

[0067] The present embodiment relates to a specific method for determining the fault location of a power distribution system based on double-criterion protection, as shown in FIG. 4, which specifically includes the following steps:

[0068] Step one: store system-related electrical quantities and calculate the DG output power before the fault;

[0069] The line with DG access is shown in FIG. 3, and the DG output power before the fault is calculated according to the formula , and , and wherein, denotes the DG grid-connected point voltage, denotes the DG grid-connected point current, is the line M side voltage, is the line N side voltage, is the load grid-connected point voltage, denotes the current flowing to the line from the M side busbar, Z represents the current flowing from the N-side line to the bus. A Z B Z C These represent the equivalent impedances of each segment of the line. For flow through Z B The current is shown in Figure 5.

[0070] Furthermore, based on the relationship between the active power output of the DG and the grid connection point voltage and output current, the active power output of the DG can be calculated. In steady state, this power is equal to the reference value P. REF Thus obtaining P REF value.

[0071] Step 2: Monitor the voltage at the DG grid connection point and determine if the protection system will activate.

[0072] Voltage at the DG grid connection point in the line Real-time monitoring, when min{|u PCC When |}≤ρ, the protection is activated. To ensure the sensitivity of the protection, the activation threshold is generally taken as 90% of the rated voltage at the grid connection point.

[0073] Step 3: Fault occurs, protection is activated, and time-delay measurement is performed;

[0074] When a fault occurs on the target line, the start-up criterion from step two is used to detect the fault, and the protection is activated with a delay of t. set Then, read the voltage across line MN. With current in The reference direction is from the busbar to the line, while The reference direction is from the line to the busbar, where, in order to balance the speed and accuracy of the protection, the delay t set The typical value is 5ms.

[0075] Step 4: Derive the virtual voltage and the difference between the real and virtual voltages on the opposite side of the circuit;

[0076] According to respectively Derivation of the calculation of the virtual voltage across MN The letter in parentheses indicates which side the virtual voltage is viewed from the network end, i.e. This means that, looking into the line from side N, the virtual voltage on the opposite side M is calculated by substituting the electrical quantities seen from that side. Then, these are substituted into the formula. and Calculate the real-to-virtual voltage difference, where These are the actual voltages on the MN side measured in step three, and D. M (x), DN (x) is the function of the real and virtual voltage difference on the M, N side with respect to the position x of the fault in the line, x ∈ [0, 1].

[0077] Step five: determine the threshold according to the function of the line parameters;

[0078] According to and the function, and find the intersection point of the two functions The y-axis value of the intersection point is denoted as D set , wherein DG fault output current, Z MN is the overall line impedance of MN.

[0079] Step six: inject high-frequency harmonics to construct a high-frequency differential criterion;

[0080] Control the DG to inject 10 times frequency high-frequency harmonics (500 Hz) into the line, and measure the high-frequency current flowing through the two sides of MN and According to the under the fault in the area and the under the fault outside the area, respectively calculate k in under different load conditions out , wherein is the high-frequency current flowing to the load of the line, indicates the high-frequency harmonics, and the minimum value of k out is k set , and further denoted as

[0081] Step seven, protection criterion judgment;

[0082] Substitute the protection criterion to judge whether the fault is in the area or outside the area, and send the protection judgment signal to the protection action unit.

[0083] Embodiments of the present disclosure also include:

[0084] As shown in FIG. 6, when a short-circuit fault occurs in the line between M and the DG grid connection point, as shown in step four, the real and virtual voltage difference can be calculated by to derive the virtual voltage of MN and through the formula and Calculate the real and virtual voltage difference value, and it can be known from the analysis of FIG. 6 that When the fault occurs, the voltage at the DG grid connection point decreases, the q-axis component of the current flowing through the DG is increased, Since Z A , Z B , and Z C are all greater than 0, it is further known that

[0085] Similarly, when the fault occurs in the line between the DG grid-connected point and the T-connected load, as shown in FIG. 7, there are When the fault occurs in the line between the T-connected load and N, as shown in FIG. 8, there are In summary of the above analysis, it is known that x [0, 1], As described in step five, the function T M (x) is constructed. N After the functions D M (x), D N (x), T M (x), and T N (x) are constructed, the size relationship between D M (x), D N (x), T M (x), and T N (x) is shown in FIG. 9. When the fault occurs outside the area or there is no fault, the theoretical values of D M (x) and D N (x) are 0, and it is easy to know that the threshold value can be set to distinguish the faults inside and outside the area, and the threshold value can be selected by the functions T M (x) and T N (x).

[0086] When the DG is controlled to inject high-frequency harmonics into the line, k in and k out can be obtained according to step six when the faults inside and outside the area, respectively, and there are wherein each parameter Z HM can be determined, and the high-frequency equivalent impedance Z HL of the load is the only variable. As Z HL increases, the curves of k in and k out are shown in FIG. 10. It can be seen that as Z HL increases, k in and k out both decrease, but there is still a clear gap between the curves of k in and k out , and a suitable threshold value can be set to distinguish them.

[0087] Embodiments of the disclosure aim to solve the problem of deterioration of the adaptability of traditional single-end and double-end protection to the distribution network of the distributed new energy (DG) and the T-connected load. Based on the idea of control and protection collaboration, a double-criterion fusion mode is adopted to fully exert the advantages of the controllable characteristics of the DG. The protection criterion proposed is not affected by the line fault type, fault location, transition resistance size, and T-connected load capacity size. The protection scheme proposed has no protection dead zone and has higher reliability.

[0088] The embodiment of the disclosure further provides a device for determining a fault position of a power distribution system based on double criterion protection. It should be noted that the device for determining a fault position of a power distribution system based on double criterion protection can be used to execute the method for determining a fault position of a power distribution system based on double criterion protection provided by the embodiment of the disclosure. The device is used to realize the above-mentioned embodiment and preferred embodiment, and details are not repeated. As used below, the term "module" can be a combination of software and / or hardware that realizes a predetermined function. Although the device described in the following embodiment is preferably realized in software, hardware, or a combination of software and hardware is also possible and is conceived.

[0089] The device for determining a fault position of a power distribution system based on double criterion protection provided by the embodiment of the disclosure is described below.

[0090] FIG. 11 is a schematic diagram of a device for determining a fault position of a power distribution system based on double criterion protection according to the embodiment of the disclosure. As shown in FIG. 11, the above-mentioned device is applied to a controller of a power distribution system, and the power distribution system further includes a distributed new energy and load T connection line connected by electricity. The device includes a first acquisition unit 1101, a second acquisition unit 1102, a first determination unit 1103, a control unit 1104, and a second determination unit 1105.

[0091] The first acquisition unit 1101 is configured to acquire relevant electrical quantities of the power distribution system, wherein the relevant electrical quantities include a distributed new energy grid-connected point voltage, a distributed new energy grid-connected point current, a load T connection line side voltage, a load T connection line grid-connected point voltage, a load T connection line grid-connected point current, a load T connection line side current, and equivalent impedances of each segment of the load T connection line.

[0092] The second acquisition unit 1102 is configured to determine whether a fault occurs according to a size relationship between the distributed new energy grid-connected point voltage and a starting threshold value. In the case where it is determined that a fault occurs, the second acquisition unit 1102 is configured to acquire a post-fault load T connection line side voltage and a post-fault load T connection line side current after a preset time period of the fault occurrence, wherein the starting threshold value is related to a distributed new energy grid-connected point rated voltage.

[0093] The preset time period can be selected as 2 ms, 5 ms, or 10 ms. In order to balance the speed and accuracy of protection, the preset time period is generally 5 ms.

[0094] Specifically, if the absolute value of the minimum voltage at the grid connection point of the distributed new energy is less than the starting threshold, a fault is considered to have occurred, and the protection is activated. After the fault is determined, the voltage and current of the load T-connected to the line after the fault are obtained 5ms later. In order to ensure the sensitivity of the protection, the starting threshold is generally taken as 90% of the rated voltage at the grid connection point.

[0095] The first determining unit 1103 is used to determine the virtual voltage on the opposite side of the load T-connected line based on the voltage on the load T-connected line side after the fault, the current on the load T-connected line side after the fault, and the relevant electrical quantities, and to determine the first protection criterion based on the virtual voltage on the opposite side of the load T-connected line, the difference between the real and virtual voltages of the load T-connected line, and the relevant electrical quantities.

[0096] Specifically, the difference between the actual and virtual voltages on both sides of the load T-connection line is used to determine the actual-virtual voltage difference of the load T-connection line. Then, based on the relevant parameters of the power distribution system, a high-frequency voltage function with respect to the fault location is constructed on one side of the load T-connection line. High-frequency voltage function on the other side of the load-T-connected line with respect to the fault location Find the y-axis value of the intersection of these two functions as the fault threshold, and then obtain the first protection criterion based on the fault threshold.

[0097] Control unit 1104 is used to control the distributed new energy to inject high-frequency harmonics into the load T-connection line, obtain the high-frequency current of the load T-connection line, and determine the second protection criterion based on the high-frequency current of the load T-connection line.

[0098] For example, controlling the injection of a 10-fold high-frequency harmonic (500Hz) into the load T-connection line by distributed renewable energy sources, and measuring the high-frequency current flowing through both sides of MN. and According to the fault in the area With faults outside the zone Calculate k under different load conditions. in With k out ,in For high-frequency current flowing to the line load, To represent high-frequency harmonics, denoted by k out The minimum value in is k set Further record

[0099] The second determining unit 1105 is used to determine the fault location of the power distribution system based on the first protection criterion and the second protection criterion.

[0100] Specifically, the first protection criterion and the second protection criterion can be used to determine whether the fault is within the zone or outside the zone.

[0101] In this embodiment, the first acquisition unit is configured to acquire relevant electrical quantities of the power distribution system, wherein the relevant electrical quantities include a distributed new energy grid-connected point voltage, a distributed new energy grid-connected point current, a load T connection line side voltage, a load T connection line grid-connected point voltage, a load T connection line grid-connected point current, a load T connection line side current, and equivalent impedances of each section of the load T connection line; the second acquisition unit is configured to determine whether a fault occurs according to a size relationship between the distributed new energy grid-connected point voltage and a starting threshold value, and to acquire a post-fault load T connection line side voltage and a post-fault load T connection line side current after a preset time period of the fault occurrence in a case where it is determined that the fault occurs, wherein the starting threshold value is related to a distributed new energy grid-connected point rated voltage; the first determination unit is configured to determine a load T connection line opposite side virtual voltage according to the post-fault load T connection line side voltage, the post-fault load T connection line side current, and the relevant electrical quantities, and to determine a first protection criterion according to the load T connection line opposite side virtual voltage, a load T connection line real-imaginary voltage difference, and the relevant electrical quantities; the control unit is configured to control the distributed new energy to inject a high-frequency harmonic wave into the load T connection line, to acquire a load T connection line high-frequency current, and to determine a second protection criterion according to the load T connection line high-frequency current; and the second determination unit is configured to determine a fault position of the power distribution system according to the first protection criterion and the second protection criterion. Based on the idea of control-protection cooperation, a double criterion is constructed in combination with the differential characteristics of the real-imaginary voltage difference and the high-frequency injected current, thereby solving the problem that the current active detection protection scheme for the distributed new energy DG alternating current system has a relatively limited use scene, and the double criterion is not affected by the fault type, the fault position, the size of the transition resistance, and the like, and has good reliability.

[0102] As an optional solution, the first acquisition unit includes a first determination module configured to determine the distributed new energy grid-connected point voltage and the distributed new energy grid-connected point current according to the load T connection line side voltage, the load T connection line grid-connected point voltage, the load T connection line side current, the load T connection line grid-connected point current, the equivalent impedances of each section of the load T connection line, and currents corresponding to the equivalent impedances of each section of the load T connection line.

[0103] Specifically, the distributed new energy grid-connected point voltage and the distributed new energy grid-connected point current are determined according to the formula The distributed new energy grid-connected point voltage and the distributed new energy grid-connected point current are determined according to the formula and wherein, DG grid-connected point voltage is represented by VDG, DG grid-connected point current is represented by IDG, the line M side voltage is represented by VM, the line N side voltage is represented by VN, the load grid-connected point voltage is represented by VL, the current flowing from the M side bus to the line is represented by IM, and Z represents the current flowing from the N-side line to the bus. A Z B Z C These represent the equivalent impedances of each segment of the line. For flow through Z B The current.

[0104] In one alternative approach, the second acquisition unit includes a startup module for determining min{|u PCC When |}≤ρ, the fault is determined to have occurred, and protection is activated, where min{|u PCC |} represents the absolute value of the minimum voltage at the grid connection point of distributed renewable energy, and ρ represents the protection start threshold.

[0105] Specifically, the voltage at the DG grid connection point in the line. Real-time monitoring, when min{|u PCC When |}≤ρ, the protection is activated. To ensure the sensitivity of the protection, the activation threshold is generally taken as 90% of the rated voltage at the grid connection point.

[0106] In one optional scheme, the first determining unit includes a second determining module, a third determining module, and a fourth determining module; the second determining module is used to determine the voltage difference D between the virtual and real voltages on the load T-connected line side based on the virtual voltage on the load T-connected line side and the actual voltage on the load T-connected line side. M (x) Determine the voltage difference D between the virtual and real voltages on the other side of the load T-connected line based on the virtual voltage and the actual voltage on the other side of the load T-connected line. N (x); The third determining module is used to construct a first function and a second function based on the relevant electrical quantities, and determine the ordinate value of the intersection point of the first function and the second function as the fault threshold D. set Wherein, the first function is a high-frequency voltage function on one side of the load T-connected line with respect to the fault location, and the second function is a high-frequency voltage function on the other side of the load T-connected line with respect to the fault location; the fourth determining module is used to determine based on D M (x), D N (x) and D set The first protection criterion is determined, and the first protection criterion is C. r1 =D M (x)>D set ∪D N (x)>D set .

[0107] Specifically, according to Derivation of the calculation of the virtual voltage across MN The letter in parentheses indicates which side the virtual voltage is viewed from the network end, i.e. This means that, looking into the line from side N, the virtual voltage on the opposite side M is calculated by substituting the electrical quantities seen from that side. Then, these are substituted into the formula. and Calculate the real-to-virtual voltage difference, where These are the actual voltages on the MN side measured in step three, and D. M (x), D N (x) are functions of the real and virtual voltage differences on the M and N sides, respectively, with respect to the fault location x in the line, x∈[0,1].

[0108] In one optional scheme, the control unit includes a control module, a measurement module, a fifth determination module, a sixth determination module, and a seventh determination module; the control module is used to control the distributed renewable energy source to inject N times the high-frequency harmonics into the load T-connection line, where N is an integer greater than 1; the measurement module is used to measure the high-frequency current on one side of the load T-connection line after injecting N times the high-frequency harmonics. High-frequency current on the other side of the load T-connected line The fifth determining module is used to determine the high-frequency current on one side of the load T-connected line. The high-frequency current on the other side of the load T-connection line The external fault parameter k is determined by the high-frequency harmonics. out The sixth determining module is used to determine the external fault parameter k. out With high frequency harmonics Determine the fault current threshold I Kset The seventh determining module is used to determine the fault current threshold I based on the fault current threshold I. Kset The high-frequency current on one side of the load T-connected line And the high-frequency current on the other side of the load T-connected line The second protection criterion is determined as follows:

[0109] Specifically, the DG is controlled to inject a 10th harmonic (500Hz) high-frequency wave into the line, and the high-frequency current flowing through both sides of MN is measured. and According to the fault in the area With faults outside the zone Calculate k under different load conditions. in With k out ,in For high-frequency current flowing to the line load, To represent high-frequency harmonics, denoted by k out The minimum value in is k set Further record

[0110] An optional solution, the second determining unit includes an eighth determining module and a ninth determining module, the eighth determining module is used for determining C r1 ∪C r2 Whether equal to 1 or equal to 0; the ninth determining module is used for determining that the fault is an in-zone fault in the case of determining equal to 1, and determining that the fault is an out-zone fault in the case of determining equal to 0.

[0111] Specifically, according to the protection criterion The fault is judged in-zone or out-zone, and the protection judgment signal is sent to the protection action unit.

[0112] An optional solution, the device further includes a generating unit, used for generating fault alarm information according to the determined fault position after determining the fault position according to the first protection criterion and the second protection criterion, the fault alarm information indicates that the fault position is an out-zone fault or an in-zone fault.

[0113] Specifically, the fault alarm information indicating the fault position can indicate the relevant personnel the fault position faster, so as to solve the fault problem of the power distribution system faster.

[0114] The device for determining the fault position of the power distribution system based on the double-criterion protection includes a processor and a memory, the first acquisition unit, the second acquisition unit, the first determining unit, the control unit, the second determining unit and the like are stored in the memory as program units, and the corresponding functions are realized by the processor executing the program units stored in the memory. The above-mentioned modules are located in the same processor; or, the above-mentioned modules are located in different processors in any combination.

[0115] The processor contains a core, and the core calls the corresponding program unit in the memory. The core can be set to one or more, and the scene of the active detection protection scheme for the DG AC system is limited by adjusting the core parameters.

[0116] The memory can include a non-permanent memory in a computer readable medium, a random access memory (RAM) and / or a non-volatile memory such as a read-only memory (ROM) or a flash memory (flash RAM), and the memory includes at least one memory chip.

[0117] The embodiment of the application provides a computer readable storage medium, the computer readable storage medium includes a stored program, wherein, when the program runs, the device where the computer readable storage medium is located executes the method for determining the fault position of the power distribution system based on the double-criterion protection.

[0118] Specifically, the method for determining a fault position of a power distribution system based on double criteria protection comprises the following steps:

[0119] In step S201, relevant electrical quantities of the power distribution system are acquired, wherein the relevant electrical quantities comprise a distributed new energy grid-connected point voltage, a distributed new energy grid-connected point current, a load T connection line side voltage, a load T connection line grid-connected point voltage, a load T connection line grid-connected point current, a load T connection line side current, and equivalent impedances of each section of the load T connection line.

[0120] In step S202, whether a fault occurs is determined according to a size relationship between the distributed new energy grid-connected point voltage and a starting threshold value, and in a case where it is determined that a fault occurs, a post-fault load T connection line side voltage and a post-fault load T connection line side current after a preset time period of the fault occurrence are acquired, wherein the starting threshold value is related to a distributed new energy grid-connected point rated voltage.

[0121] In step S203, a load T connection line opposite side virtual voltage is determined according to the post-fault load T connection line side voltage, the post-fault load T connection line side current, and the relevant electrical quantities, and a first protection criterion is determined according to the load T connection line opposite side virtual voltage, a load T connection line real and virtual voltage difference, and the relevant electrical quantities.

[0122] In step S204, the distributed new energy is controlled to inject a high-frequency harmonic wave into the load T connection line, a load T connection line high-frequency current is acquired, and a second protection criterion is determined according to the load T connection line high-frequency current.

[0123] In step S205, a fault position of the power distribution system is determined according to the first protection criterion and the second protection criterion.

[0124] An embodiment of the present application provides a processor used for running a program, wherein the program performs the method for determining a fault position of a power distribution system based on double criteria protection when running.

[0125] Specifically, the method for determining a fault position of a power distribution system based on double criteria protection comprises the following steps:

[0126] In step S201, relevant electrical quantities of the power distribution system are acquired, wherein the relevant electrical quantities comprise a distributed new energy grid-connected point voltage, a distributed new energy grid-connected point current, a load T connection line side voltage, a load T connection line grid-connected point voltage, a load T connection line grid-connected point current, a load T connection line side current, and equivalent impedances of each section of the load T connection line.

[0127] In step S202, whether a fault occurs is determined according to a size relationship between the distributed new energy grid-connected point voltage and a starting threshold value, and in a case where it is determined that a fault occurs, a post-fault load T connection line side voltage and a post-fault load T connection line side current after a preset time period of the fault occurrence are acquired, wherein the starting threshold value is related to a distributed new energy grid-connected point rated voltage.

[0128] Step S203, determining a load T connection line opposite side virtual voltage according to the load T connection line side voltage after the fault, the load T connection line side current after the fault and the related electrical quantity, and determining a first protection criterion according to the load T connection line opposite side virtual voltage, the load T connection line real and virtual voltage difference and the related electrical quantity;

[0129] Step S204, controlling the distributed new energy to inject high frequency harmonic wave to the load T connection line, obtaining the load T connection line high frequency current, and determining a second protection criterion according to the load T connection line high frequency current;

[0130] Step S205, determining the fault position of the power distribution system according to the first protection criterion and the second protection criterion.

[0131] The embodiment of the application provides a kind of equipment, equipment includes processor, memory and the program stored in memory and can be run on processor, when processor executes program, at least the following steps are realized:

[0132] Step S201, obtains the related electrical quantity of power distribution system, wherein, related electrical quantity includes distributed new energy grid-connected point voltage, distributed new energy grid-connected point current, load T connection line side voltage, load T connection line grid-connected point voltage, load T connection line grid-connected point current, load T connection line side current, load T connection line each section equivalent impedance;

[0133] Step S202, determines whether fault occurs according to the size relationship of distributed new energy grid-connected point voltage and start threshold value, in the case where it is determined that fault occurs, obtains the load T connection line side voltage after the fault and the load T connection line side current after the fault in the preset time period after the fault occurs, wherein, start threshold value is related to distributed new energy grid-connected point rated voltage;

[0134] Step S203, determining a load T connection line opposite side virtual voltage according to the load T connection line side voltage after the fault, the load T connection line side current after the fault and the related electrical quantity, and determining a first protection criterion according to the load T connection line opposite side virtual voltage, the load T connection line real and virtual voltage difference and the related electrical quantity;

[0135] Step S204, controlling the distributed new energy to inject high frequency harmonic wave to the load T connection line, obtaining the load T connection line high frequency current, and determining a second protection criterion according to the load T connection line high frequency current;

[0136] Step S205, determining the fault position of the power distribution system according to the first protection criterion and the second protection criterion.

[0137] The device in the present application can be a server, a PC, a PAD, a mobile phone, etc.

[0138] The present disclosure also provides a computer program product adapted to execute a program that initially has at least the following method steps when executed on a data processing device:

[0139] In step S201, relevant electrical quantities of the power distribution system are acquired, wherein the relevant electrical quantities include distributed new energy grid-connected point voltage, distributed new energy grid-connected point current, load T connection line side voltage, load T connection line grid-connected point voltage, load T connection line grid-connected point current, load T connection line side current, and equivalent impedance of each section of the load T connection line.

[0140] In step S202, whether a fault occurs is determined according to the size relationship between the distributed new energy grid-connected point voltage and a start threshold value, and in the case where it is determined that a fault occurs, post-fault load T connection line side voltage and post-fault load T connection line side current after a preset time period after the fault occurs are acquired, wherein the start threshold value is related to a distributed new energy grid-connected point rated voltage.

[0141] In step S203, a load T connection line opposite side virtual voltage is determined according to the post-fault load T connection line side voltage, the post-fault load T connection line side current, and the relevant electrical quantities, and a first protection criterion is determined according to the load T connection line opposite side virtual voltage, a load T connection line real and virtual voltage difference, and the relevant electrical quantities.

[0142] In step S204, a distributed new energy source injects high-frequency harmonics into the load T connection line, acquires a load T connection line high-frequency current, and determines a second protection criterion according to the load T connection line high-frequency current.

[0143] In step S205, the fault position of the power distribution system is determined according to the first protection criterion and the second protection criterion.

[0144] Obviously, those skilled in the art should understand that the above-mentioned modules or steps of the present application can be realized by general computing devices, which can be concentrated on a single computing device or distributed on a network composed of multiple computing devices, and they can be realized by program codes executable by computing devices, so that they can be stored in storage devices and executed by computing devices, and in some cases, the steps shown or described can be executed in different order, or they can be manufactured into individual integrated circuit modules, or multiple modules or steps can be manufactured into a single integrated circuit module. Thus, the present application is not limited to any specific combination of hardware and software.

[0145] Those skilled in the art will appreciate that embodiments of the disclosure can be supplied as a method, a system, or a computer program product. Accordingly, the disclosure can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the disclosure can take the form of a computer program product on one or more computer readable storage media (including, but not limited to, disk memory, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0146] The disclosure is described in reference to the flowchart and / or block diagrams of the method, apparatus (system) and computer program product according to embodiments of the disclosure. It should be understood that each flow and / or block in the flowchart and / or block diagrams, and a combination of flows and / or blocks in the flowchart and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, a special purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions, which are executed via the processor of the computer or other programmable data processing apparatus, generate means for implementing the functions specified in one or more flows in the flowchart and / or one or more blocks in the block diagram.

[0147] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including instruction means, which implement the functions specified in one or more flows in the flowchart and / or one or more blocks in the block diagram.

[0148] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operational steps are performed on the computer or other programmable data processing apparatus to generate a computer implemented process, so that the instructions executed on the computer or other programmable data processing apparatus provide steps for implementing the functions specified in one or more flows in the flowchart and / or one or more blocks in the block diagram.

[0149] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0150] The memory can include non-persistent memory in the computer readable medium, random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash memory. The memory is an example of computer readable media.

[0151] Computer-readable media includes permanent and non-permanent, movable and non-movable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette, magnetic tape disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible by a computing device. According to the definition herein, computer-readable media does not include transitory media such as modulated data signals and carriers.

[0152] It should also be noted that the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusion, so that processes, methods, articles or devices including a series of elements not only include those elements, but also include other elements not explicitly listed, or inherent to such processes, methods, articles or devices. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0153] From the above description, it can be seen that the above-mentioned embodiments of the present disclosure achieve the following technical effects:

[0154] 1) A method for determining the fault location of a power distribution system based on double criteria protection according to the present disclosure, the method is applied to a controller of the power distribution system, the power distribution system further comprises a distributed new energy and load T connection line connected electrically, comprising: obtaining relevant electrical quantities of the power distribution system, wherein the relevant electrical quantities include distributed new energy grid-connected point voltage, distributed new energy grid-connected point current, load T connection line side voltage, load T connection line grid-connected point voltage, load T connection line grid-connected point current, load T connection line side current, and equivalent impedance of each section of the load T connection line; determining whether a fault occurs according to the size relationship between the distributed new energy grid-connected point voltage and the starting threshold value, and in the case of determining that a fault occurs, obtaining the post-fault load T connection line side voltage and the post-fault load T connection line side current after a preset time period of the fault occurrence, wherein the starting threshold value is related to the rated voltage of the distributed new energy grid-connected point; determining the virtual voltage on the opposite side of the load T connection line according to the post-fault load T connection line side voltage, the post-fault load T connection line side current, and the relevant electrical quantities, and determining the first protection criterion according to the virtual voltage on the opposite side of the load T connection line, the difference between the real and virtual voltages of the load T connection line, and the relevant electrical quantities; controlling the distributed new energy to inject high-frequency harmonics into the load T connection line, obtaining the high-frequency current of the load T connection line, and determining the second protection criterion according to the high-frequency current of the load T connection line; and determining the fault location of the power distribution system according to the first protection criterion and the second protection criterion. Based on the idea of control and protection cooperation, the double criteria are constructed by combining the differential characteristics of the real and virtual voltage difference and the high-frequency injected current, which solves the problem that the current active detection protection scheme for the distributed new energy DG AC system has a relatively limited use scene, and is not affected by the fault type, fault location, transition resistance size, etc., and has good reliability.

[0155] 2) The application discloses a device for determining the fault position of a power distribution system based on double criteria protection, which is applied to a controller of the power distribution system, and the power distribution system further comprises a distributed new energy and load T connection line connected in an electric manner, and comprises a first acquisition unit, a second acquisition unit, a first determination unit, a control unit and a second determination unit. The first acquisition unit is used for acquiring relevant electrical quantities of the power distribution system, wherein the relevant electrical quantities comprise a distributed new energy grid-connected point voltage, a distributed new energy grid-connected point current, a load T connection line side voltage, a load T connection line grid-connected point voltage, a load T connection line grid-connected point current, a load T connection line side current and equivalent impedances of each section of the load T connection line. The second acquisition unit is used for determining whether a fault occurs according to the size relationship between the distributed new energy grid-connected point voltage and a starting threshold value, and acquiring a post-fault load T connection line side voltage and a post-fault load T connection line side current after a preset time period of the fault occurrence in the case of determining that the fault occurs, wherein the starting threshold value is related to a distributed new energy grid-connected point rated voltage. The first determination unit is used for determining a load T connection line opposite side virtual voltage according to the post-fault load T connection line side voltage, the post-fault load T connection line side current and the relevant electrical quantities, and determining a first protection criterion according to the load T connection line opposite side virtual voltage, a load T connection line real and virtual voltage difference and the relevant electrical quantities. The control unit is used for controlling the distributed new energy to inject a high-frequency harmonic wave into the load T connection line, acquiring a load T connection line high-frequency current, and determining a second protection criterion according to the load T connection line high-frequency current. The second determination unit is used for determining the fault position of the power distribution system according to the first protection criterion and the second protection criterion. Based on the idea of control and protection cooperation, the double criteria are constructed in combination with the differential characteristics of the real and virtual voltage difference and the high-frequency injected current, the problem that the current active detection protection scheme for the distributed new energy DG AC system is limited in use scene is solved, and the double criteria are not influenced by the fault type, the fault position, the size of the transition resistance and the like, and have good reliability.

[0156] The above merely describes the preferred embodiments of the application, but should not be used to limit the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A method for determining the location of a fault in an electrical distribution system based on dual criterion protection, characterized in that, The method is applied to a controller of a power distribution system, the power distribution system further comprising a distributed new energy and load T connection line connected electrically, comprising: acquiring relevant electrical quantities of the power distribution system, wherein the relevant electrical quantities comprise a distributed new energy grid-connected point voltage, a distributed new energy grid-connected point current, a load T connection line side voltage, a load T connection line grid-connected point voltage, a load T connection line grid-connected point current, a load T connection line side current, and equivalent impedances of each section of the load T connection line; determining whether a fault occurs according to a size relationship between the distributed new energy grid-connected point voltage and a starting threshold value, and acquiring a post-fault load T connection line side voltage and a post-fault load T connection line side current after a preset time period of the fault occurring in a case where it is determined that the fault occurs, wherein the starting threshold value is related to a distributed new energy grid-connected point rated voltage; determining a load T connection line opposite side virtual voltage according to the post-fault load T connection line side voltage, the post-fault load T connection line side current, and the relevant electrical quantities, and determining a first protection criterion according to the load T connection line opposite side virtual voltage, a load T connection line real and virtual voltage difference, and the relevant electrical quantities; controlling the distributed new energy to inject a high-frequency harmonic wave into the load T connection line, acquiring a load T connection line high-frequency current, and determining a second protection criterion according to the load T connection line high-frequency current; determining a fault position of the power distribution system according to the first protection criterion and the second protection criterion.

2. The method of claim 1, wherein, acquiring relevant electrical quantities of the power distribution system, wherein the relevant electrical quantities comprise a distributed new energy grid-connected point voltage and a distributed new energy grid-connected point current, and the acquiring comprises: determining the distributed new energy grid-connected point voltage and the distributed new energy grid-connected point current according to the load T connection line side voltage, the load T connection line grid-connected point voltage, the load T connection line side current, the load T connection line grid-connected point current, equivalent impedances of each section of the load T connection line, and currents corresponding to the equivalent impedances of each section of the load T connection line.

3. The method of claim 1, wherein, determining whether a fault occurs according to a size relationship between the distributed new energy grid-connected point voltage and a starting threshold value, and the determining comprises: In the case of determining min{|u PCC |}≤ρ, it is determined that the fault occurs, and protection is started, wherein min{|u PCC |} represents the absolute value of the minimum value of the voltage of the distributed new energy grid-connected point, and ρ represents a protection starting threshold value.

4. The method of claim 1, wherein, determining a load T connection line opposite side virtual voltage according to the post-fault load T connection line side voltage, the post-fault load T connection line side current, and the relevant electrical quantities, and the determining a first protection criterion according to the load T connection line opposite side virtual voltage, a load T connection line real and virtual voltage difference, and the relevant electrical quantities comprises: According to the load T side virtual voltage, the load T side actual voltage, the load T side real and virtual voltage difference D is determined M (x), according to the load T side virtual voltage, the load T side actual voltage, the load T side real and virtual voltage difference D is determined N (x); According to the related electrical quantity, a first function and a second function are constructed, and a longitudinal coordinate value of an intersection point of the first function and the second function is determined as a fault threshold D set wherein the first function is a high-frequency voltage function of one side of a load T connection line with respect to a fault position, and the second function is a high-frequency voltage function of the other side of the load T connection line with respect to the fault position. According to D M (x), D N (x) and D set The first protection criterion is determined, which is C r1 = D M (x) > D set ∪ D N (x) > D set .

5. The method of claim 4, wherein, controlling the distributed new energy to inject a high-frequency harmonic wave into the load T connection line, acquiring a load T connection line high-frequency current, and determining a second protection criterion according to the load T connection line high-frequency current, and the controlling and the determining comprise: controlling the distributed new energy to inject N times of the high-frequency harmonic wave into the load T connection line, wherein N is an integer greater than 1; After injecting N times the high frequency harmonic, the high frequency current on the load T connection side is measured and the high frequency current on the other side of the load T connection According to the load T connection line side high frequency current The high-frequency current on the other side of the load T connection and said high frequency harmonic determines an external fault parameter k out ; According to the external fault parameter k out With high frequency harmonics Determining a fault current threshold I Kset ; According to the fault current threshold I Kset , the load T side high-frequency current and the high frequency current on the other side of the load T connection determining the second protection criterion as 6. The method of claim 5, wherein, determining a fault position of the power distribution system according to the first protection criterion and the second protection criterion, and the determining comprises: determining C r1 ∪C r2 whether equal to 1 or to 0; in a case where it is determined that the fault position is equal to 1, determining that the fault is an in-zone fault, and in a case where it is determined that the fault position is equal to 0, determining that the fault is an out-of-zone fault.

7. The method of claim 1, wherein, after determining the fault position according to the first protection criterion and the second protection criterion, the method further comprises: generating a fault alarm information according to the determined fault position, and the fault alarm information indicates that the fault position is an out-of-zone fault or an in-zone fault.

8. A device for determining the location of a fault in a power distribution system based on dual-criteria protection, characterized in that, The device is applied to a controller of a power distribution system, and the power distribution system further comprises a distributed new energy and load T connection line connected electrically, comprising: A first acquisition unit is configured to acquire relevant electrical quantities of the power distribution system, wherein the relevant electrical quantities comprise a distributed new energy grid-connected point voltage, a distributed new energy grid-connected point current, a load T connection line side voltage, a load T connection line grid-connected point voltage, a load T connection line grid-connected point current, a load T connection line side current, and equivalent impedances of each section of the load T connection line. A second acquisition unit is configured to determine whether a fault occurs according to a size relationship between the distributed new energy grid-connected point voltage and a start threshold value, and acquire a post-fault load T connection line side voltage and a post-fault load T connection line side current after a preset time period of the fault occurrence in a case where it is determined that the fault occurs, wherein the start threshold value is related to a distributed new energy grid-connected point rated voltage. A first determination unit is configured to determine a load T connection line opposite side virtual voltage according to the post-fault load T connection line side voltage, the post-fault load T connection line side current, and the relevant electrical quantities, and determine a first protection criterion according to the load T connection line opposite side virtual voltage, a load T connection line real and virtual voltage difference, and the relevant electrical quantities. A control unit is configured to control the distributed new energy to inject a high-frequency harmonic wave into the load T connection line, acquire a load T connection line high-frequency current, and determine a second protection criterion according to the load T connection line high-frequency current. A second determination unit is configured to determine a fault position of the power distribution system according to the first protection criterion and the second protection criterion.

9. A computer-readable storage medium, characterized in that, The computer readable storage medium comprises a stored program, wherein when the program runs, the computer readable storage medium controls a device where the computer readable storage medium is located to execute the method for determining a fault position of a power distribution system based on double-criteria protection according to any one of claims 1 to 7.

10. An electronic device, comprising: Comprise: One or more processors, memories, and one or more programs, wherein the one or more programs are stored in the memories and configured to be executed by the one or more processors, and the one or more programs comprise programs for executing the method for determining a fault position of a power distribution system based on double-criteria protection according to any one of claims 1 to 7.

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