Method and system for establishing broadband impedance spectrum model of multi-branch cable network

Abstract

The invention discloses a broadband impedance spectrum model establishment method and system for a multi-branch cable network, the multi-branch cable network comprises a plurality of branch cables connected in series, one end of the multi-branch cable network is connected with a load impedance, the characteristic impedance and attenuation coefficient of a single branch cable are collected, and a transfer parameter matrix of the single branch cable is constructed; taking the output end of any branch cable as a signal injection end, and obtaining an equivalent transfer parameter matrix of the multi-branch cable network according to the product of the transfer parameter matrix of the branch cable and the transfer parameter matrixes of the other branch cables; and establishing a broadband impedance spectrum model of the multi-branch cable network by using the load impedance and the equivalent transfer parameter matrix. According to the method, the head end input impedance spectrum and the reflection coefficient spectrum of any wire outlet end in the multi-branch cable network can be obtained, and model support is provided for research and application of the BIS in the multi-branch cable network.

Description

Technical Field

[0001] The present invention belongs to the technical field of cable insulation testing in high voltage and insulation technology, and specifically relates to a method and system for establishing a broadband impedance spectrum model for a multi-branch cable network based on a transmission line distributed parameter model and frequency domain reflectometry (FDR). Background Art

[0002] As electricity consumption in urban areas increases year by year and the size of cities expands, the topology of urban power grids becomes increasingly complex, with lines showing multi-branch and multi-node characteristics. At the same time, cables are more reliable and safer than overhead lines and take up less space. As the main medium for transmitting electricity in urban power grid systems, their share in transmission lines is also increasing.

[0003] Cable impedance characteristics are the main information for evaluating the health status of cable insulation. In the existing technology, broadband impedance spectrum (BIS) technology has developed rapidly with its technical advantages such as non-invasive, non-destructive, efficient and convenient, and has broad application prospects. This type of technology relies on a network analyzer (Vector Network Analyzer, VNA) or an impedance analyzer to input a low-voltage and high-frequency sinusoidal traveling wave signal within a certain frequency band into the cable in a short period of time, and uses the traveling wave frequency domain reflection principle to obtain the cable's BIS / RCS (Reflection Coefficient Spectrum). By analyzing BIS / RCS, the characteristic parameter information of a certain cable line can be effectively extracted, and the cable health status and remaining life assessment can be performed; and BIS / RCS can be used for mathematical algorithm processing to achieve cable fault identification and location.

[0004] However, the existing BIS technology can only construct the broadband impedance spectrum of the head-end input of a single cable line through the traveling wave transmission equation based on the transmission line distributed parameter model. Due to the limitations of the transmission line distributed parameter model and the traveling wave transmission equation, it is impossible to provide a method for establishing the head-end input impedance spectrum model of the cable network with cable branches. However, in an actual power cable network with multiple branches, since the branch units have ring network cabinets, branch boxes, and branch joints, it becomes very difficult to disconnect each section of the cable for segmented measurement in engineering applications, making it difficult to promote and apply BIS related technologies in cable networks with branches. Existing cable insulation diagnosis or fault location technology based on BIS technology focuses on the coaxial mode of the cable and mostly establishes its BIS equivalent circuit model based on the traveling wave propagation law of the transmission line or the transmission parameter matrix. The above two construction methods are limited to a single cable in existing research and applications, and have not been extended to a "Y"-shaped cable network with branches or even a multi-branch cable network with a more complex topology. This means that if you want to perform insulation diagnosis or fault location on a cable network, you can only disconnect the cable line connection units and diagnose each cable separately, which greatly increases the manpower and material costs. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a method and system for establishing a broadband impedance spectrum model of a multi-branch cable network. For a complex cable network with a branch topology, based on a transmission line distributed parameter model and a transfer parameter matrix, a broadband impedance spectrum model for a multi-branch cable network is constructed, and the head-end input impedance spectrum and reflection coefficient spectrum of any outlet end in the multi-branch cable network are obtained, providing model support for the research and application of BIS in a multi-branch cable network.

[0006] The present invention adopts the following technical solution.

[0007] The present invention proposes a method for establishing a broadband impedance spectrum model of a multi-branch cable network, wherein the multi-branch cable network includes a plurality of branch cables connected in series, and one end of the multi-branch cable network is connected to a load impedance, including:

[0008] Collect the characteristic impedance and attenuation coefficient of a single branch cable and construct the transfer parameter matrix of a single branch cable;

[0009] The output end of any branch cable is used as the signal injection end, and the equivalent transfer parameter matrix of the multi-branch cable network is obtained by multiplying the transfer parameter matrix of the branch cable with the transfer parameter matrices of the remaining branch cables;

[0010] A broadband impedance spectrum model of multi-branch cable network is established using load impedance and equivalent transfer parameter matrix.

[0011] Preferably, the characteristic impedance and attenuation coefficient of a single branch cable are collected to construct a transfer parameter matrix of the single branch cable, including:

[0012] Collect the dielectric parameters and dimensional parameters of the cable and construct the distributed parameter equivalent circuit of a single branch cable;

[0013] Based on the distributed parameter equivalent circuit of a single branch cable, the characteristic impedance and attenuation coefficient of a single branch cable are calculated, which respectively satisfy the following relationships:

[0014]

[0015] In the formula, Z 0 is the characteristic impedance, γ is the attenuation coefficient, R, L, C, G represent the distributed resistance, distributed inductance, distributed capacitance, and distributed conductance of the cable respectively, and α and β are the real and imaginary parts of the attenuation coefficient respectively;

[0016] Using characteristic impedance and attenuation coefficient, a transfer parameter matrix is ​​constructed to represent the relationship between the voltage and current signals at the head end and the voltage and current signals at the end of a single branch cable, satisfying the following relationship:

[0017]

[0018] Where U in ,I in are the input voltage and current at the head end of a single branch cable, U out ,I out They are the output voltage and current at the end of a single branch cable, is the constructed transfer parameter matrix, the first transfer parameter and the fourth transfer parameter are cosh(γl), the second transfer parameter Z 0 sinh(γl), the third transfer parameter is sinh(γl) / Z 0 , l represents the cable length.

[0019] Preferably, the transfer parameter matrices of the branch cables are different.

[0020] Preferably, the broadband impedance spectrum model of the multi-branch cable network satisfies the following relationship:

[0021]

[0022] In the formula, Z in is the broadband impedance spectrum of the multi-branch cable network, Z Lis the load impedance of the cable, and A, B, C, and D are respectively the first transfer parameter, the second transfer parameter, the third transfer parameter, and the fourth transfer parameter of the equivalent transfer parameter matrix of the multi-branch cable network.

[0023] Preferably, the equivalent transfer parameter matrix of the multi-branch cable network satisfies the following relationship:

[0024]

[0025] In the formula, are respectively a first transfer parameter, a second transfer parameter, a third transfer parameter and a fourth transfer parameter of an equivalent transfer parameter matrix after the first branch node n1; They are respectively the first transfer parameter, the second transfer parameter, the third transfer parameter and the fourth transfer parameter of the transfer parameter matrix of the zeroth-order branch cable.

[0026] Preferably, the output end of any branch cable is used as the signal injection end, and the equivalent transfer parameter matrix of the multi-branch cable network is obtained by multiplying the transfer parameter matrix of the branch cable with the transfer parameter matrices of the remaining branch cables, including:

[0027] According to the direction of signal transmission from the injection end to the load impedance, the number of branch points between the input end of each branch cable and the signal injection end is used as the grade of the branch cable, and the branch cables of the same grade connected to the same branch point are in a parallel connection relationship;

[0028] Starting from the Nth-order branch cable, the equivalent load impedance of the previous-order branch cable connected at the same branch point is calculated using the transfer parameter matrix and equivalent load impedance of the branch cable of the same order connected in parallel at the same branch point; and so on; finally, the equivalent load impedance of the zeroth-order branch cable is obtained;

[0029] The equivalent transfer parameter matrix after each branch node is obtained by using the equivalent load impedance of each branch cable;

[0030] The equivalent transfer parameter matrix of the multi-branch cable network is obtained by multiplying the transfer parameter matrix of the zeroth-order branch cable and the transfer parameter matrices of the subsequent branch cables at each level.

[0031] Preferably, starting from the Nth-order branch cable, the equivalent load impedance of the previous-order branch cable connected to the same branch point is calculated using the transfer parameter matrix and equivalent load impedance of the branch cables of the current order connected in parallel to the same branch point; and so on; and finally the equivalent load impedance of the zeroth-order branch cable is obtained, including:

[0032] Obtain the transfer parameter matrix and load impedance of all N-th branch cables connected in parallel at the same branch point, first calculate the equivalent input impedance of all N-th branch cables, and then calculate the parallel resistance of each equivalent input impedance as the equivalent load impedance of the N-1-th branch cable connected at the same branch point;

[0033] Obtain the transfer parameter matrix and equivalent load impedance of all N-1th branch cables connected in parallel at the same branch point, first calculate the equivalent input impedance of all N-1th branch cables, and then calculate the parallel resistance of each equivalent input impedance as the equivalent load impedance of the N-2th branch cable connected to the same branch point.

[0034] Preferably, the equivalent input impedance of the Nth-stage branch cable m is calculated using the following relationship:

[0035]

[0036] In the formula, is the equivalent input impedance of the Nth branch cable m, Z Lm is the load impedance of the Nth branch cable m, are respectively a first transfer parameter, a second transfer parameter, a third transfer parameter and a fourth transfer parameter of a transfer parameter matrix of an N-th level branch cable m;

[0037] Calculate the equivalent input impedance of the Nth branch cable m The parallel resistance value is connected at the same branch point n N-1 The equivalent load impedance of the N-1th branch cable.

[0038] Preferably, when d=0, 1, 2, ..., N-1, the equivalent input impedance of the d-th branch cable m satisfies the following relationship:

[0039]

[0040] In the formula, is the equivalent input impedance of the d-th branch cable m, is the equivalent load impedance of the d-th branch cable m connection, They are respectively the first transfer parameter, the second transfer parameter, the third transfer parameter and the fourth transfer parameter of the transfer parameter matrix of the d-th level branch cable m.

[0041] The present invention proposes a broadband impedance spectrum model establishment system for a multi-branch cable network, comprising:

[0042] Transfer parameter matrix calculation module, equivalent transfer parameter matrix calculation module, broadband impedance spectrum model establishment module;

[0043] The transfer parameter matrix calculation module is used to collect the characteristic impedance and attenuation coefficient of a single branch cable and construct the transfer parameter matrix of a single branch cable;

[0044] An equivalent transfer parameter matrix calculation module is used to use the output end of any branch cable as the signal injection end, and obtain the equivalent transfer parameter matrix of the multi-branch cable network by multiplying the transfer parameter matrix of the branch cable with the transfer parameter matrices of the remaining branch cables;

[0045] The broadband impedance spectrum model building module is used to build a broadband impedance spectrum model of a multi-branch cable network using load impedance and an equivalent transfer parameter matrix.

[0046] Preferably, the transfer parameter matrix calculation module includes: a distributed parameter equivalent circuit unit, a characteristic impedance and attenuation coefficient calculation unit, and a transfer parameter matrix unit;

[0047] Distributed parameter equivalent circuit unit, used to collect the dielectric parameters and size parameters of the cable and construct the distributed parameter equivalent circuit of a single branch cable;

[0048] A characteristic impedance and attenuation coefficient calculation unit, used to calculate the characteristic impedance and attenuation coefficient of a single branch cable based on a distributed parameter equivalent circuit of the single branch cable;

[0049] The transfer parameter matrix unit is used to construct a transfer parameter matrix representing the relationship between the voltage and current signals at the head end and the voltage and current signals at the end of a single branch cable by using characteristic impedance and attenuation coefficient.

[0050] Preferably, the equivalent transfer parameter matrix calculation module includes: a branch cable topology construction unit, an equivalent load impedance calculation unit, and an equivalent transfer parameter matrix unit;

[0051] The branch cable topology construction unit is used to determine the level of the branch cable according to the direction in which the signal is transmitted from the injection end to the load impedance, with the number of branch points between the input end of each branch cable and the injection end of the signal being used as the level of the branch cable, and the branch cables of the same level connected to the same branch point being in a parallel connection relationship;

[0052] The equivalent load impedance calculation unit is used to calculate the equivalent load impedance of the previous branch cable connected to the same branch point starting from the Nth branch cable, using the transfer parameter matrix and equivalent load impedance of the branch cables of the current level connected in parallel to the same branch point; and so on; and finally obtain the equivalent load impedance of the zeroth branch cable;

[0053] The equivalent transfer parameter matrix unit is used to obtain the equivalent transfer parameter matrix after each branch node by using the equivalent load impedance of each level of branch cables; the equivalent transfer parameter matrix of the multi-branch cable network is obtained by multiplying the transfer parameter matrix of the zeroth level branch cable and the transfer parameter matrix of the subsequent levels of branch cables.

[0054] A terminal comprises a processor and a storage medium; the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the steps of the method.

[0055] A computer-readable storage medium stores a computer program, which implements the steps of the method when executed by a processor.

[0056] The beneficial effects of the present invention are that, compared with the prior art, the present invention can at least implement insulation diagnosis for a cable network containing branches without disconnecting the connection units, provide support for a broadband impedance spectrum model, and construct a broadband impedance spectrum model of cables in complex topological structures containing single branches and multiple branches based on the transfer parameter matrix of the transmission line, and verify its correctness through simulation sweep frequency, thereby providing a model basis for the application of broadband impedance spectrum model technology in complex cable networks containing branches. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a flow chart of a method for establishing a broadband impedance spectrum model of a multi-branch cable network proposed by the present invention;

[0058] Figure 2 The cable in the embodiment of the present invention needs to be equivalent to a distributed parameter circuit model diagram;

[0059] Figure 3 is a schematic diagram of a "Y" type cable network in an embodiment of the present invention;

[0060] Figure 4 It is a "Y" type cable line reduction diagram in an embodiment of the present invention;

[0061] Figure 5 is a simulation line topology diagram in an embodiment of the present invention;

[0062] Figure 6 is a modulus spectrum of the input impedance of the head end of the branched Y-type cable line in an embodiment of the present invention;

[0063] Figure 7 1 is the input impedance phase spectrum of the head end of the branched Y-type cable line in the embodiment of the present invention. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0065] The present invention proposes a method for establishing a broadband impedance spectrum model of a multi-branch cable network. Figure 1 As shown, including:

[0066] Step 1: collect the characteristic impedance and attenuation coefficient of a single branch cable and construct a transfer parameter matrix of the single branch cable.

[0067] The transfer parameter matrix is ​​used to characterize the relationship between the voltage and current signals at the head end and the voltage and current signals at the end end of a single branch cable.

[0068] Specifically, step 1 includes:

[0069] Step 1.1, collect the dielectric parameters and dimensional parameters of the cable, and construct the distributed parameter equivalent circuit of a single branch cable.

[0070] Specifically, it can be known from the transmission line theory that since the length of the transmission line system is much longer than the wavelength of the electromagnetic wave, the dielectric parameters and size parameters of the cable are collected to construct the distributed parameter equivalent circuit of a single cable, such as Figure 2 In the figure, R, L, C, and G represent the distributed resistance, distributed inductance, distributed capacitance, and distributed conductance of the cable, respectively. l represents the length of the cable, and U in with I in are the voltage and current at the beginning of the cable, U out with I out are the voltage and current at the end of the cable respectively.

[0071] Step 1.2, based on the distributed parameter equivalent circuit of a single branch cable, calculate the characteristic impedance and attenuation coefficient of a single cable;

[0072] according to Figure 2 The model and parameters shown are based on the distributed parameter equivalent circuit of a single cable, and the characteristic impedance Z of the cable is calculated. 0 And the attenuation coefficient γ satisfies the following relationship:

[0073]

[0074] Where α and β are the real and imaginary parts of the attenuation coefficient, respectively.

[0075] Step 1.3, using characteristic impedance and attenuation coefficient, construct a transfer parameter matrix representing the relationship between the voltage and current signals at the head end and the voltage and current signals at the end of a single branch cable.

[0076] The transfer parameter matrix satisfies the following relationship:

[0077]

[0078] In the formula, is the constructed transfer parameter matrix, the first transfer parameter and the fourth transfer parameter are cosh(γl), the second transfer parameter Z 0 sinh(γl), the third transfer parameter is sinh(γl) / Z 0 .

[0079] The transfer parameter matrices of each branch cable are different.

[0080] From the signal injection end, the input impedance of the cable satisfies the following relationship:

[0081]

[0082] In the formula, Z L is the load impedance of the cable.

[0083] Step 2: Use the output end of any branch cable as the signal injection end, and obtain the equivalent transfer parameter matrix of the multi-branch cable network by multiplying the transfer parameter matrix of the branch cable with the transfer parameter matrices of the remaining branch cables.

[0084] Specifically, step 2 includes:

[0085] Step 2.1, according to the direction of signal transmission from the injection end to the load impedance, the number of branch points between the input end of each branch cable and the signal injection end is used as the level of the branch cable, and the branch cables of the same level connected to the same branch point are in a parallel connection relationship.

[0086] Specifically, the multi-branch cable network includes multiple branch cables connected in series, one end of the multi-branch cable network is connected to the signal injection end, and the other end of the multi-branch cable network is connected to the load impedance; in a non-limiting preferred embodiment, the outlet end of any branch cable in the multi-branch cable network is connected to the signal injection end, and according to the direction of signal transmission from the injection end to the load impedance, the number of branch points between the input end and the signal injection end of the remaining branch cables is obtained, and the level of each branch cable is defined by the number of branch points.

[0087] In a non-limiting preferred embodiment, a single-branch cable network ("Y-type" cable network) is used as an example, and its topology is as follows: Figure 3 As shown, the outlet terminal O of the first branch cable Cable1 is used as the signal U of the VNA (vector network analyzer). 1in The first branch cable is defined as a zero-level line, the length of the first branch cable is l1, and the input current at the outlet point O of the first branch cable is I 1in , the input impedance is Zin1.

[0088] The output current of the first branch cable at the first branch node n1 is I 1out , the output voltage is U 1out ; The first branch cable is divided into the second branch cable Cable2 and the third branch cable Cable3 at the branch point n1; the input current of the second branch cable is I 2in , input impedance is Zin2, length is l2, output voltage is U 2out ; The input current of the third branch cable is I 3in , input impedance is Zin3, length is l3, output voltage is U 3out The end of the second branch cable is connected to a load impedance Z2, and the end of the third branch cable is connected to another load impedance Z3. 1in There is only one branch point n1 between the injection ends of the second branch cable and the third branch cable, so both are defined as primary lines. 1in The branch cable with two branch points between the injection ends is defined as a secondary line, and so on. 1in A branch cable with N branch points between the injection ends is defined as an N-level line. Each branch cable in the multi-branch cable network is divided into N+1 levels in sequence, where one end of the N-th level branch cable is connected to the load impedance, and one end of the zero-th level branch cable is connected to the injection end of the signal.

[0089] Step 2.2, starting from the Nth-level branch cable, use the transfer parameter matrix and equivalent load impedance of the branch cables of this level connected in parallel at the same branch point to calculate the equivalent load impedance of the previous-level branch cable connected at the same branch point; and so on; finally, the equivalent load impedance of the zeroth-level branch cable is obtained.

[0090] Specifically, step 2.2 includes:

[0091] Step 2.2.1, obtain the transfer parameter matrix and load impedance of all N-th branch cables connected in parallel at the same branch point, first calculate the equivalent input impedance of all N-th branch cables, and then calculate the parallel resistance of each equivalent input impedance as the equivalent load impedance of the N-1-th branch cable connected to the same branch point.

[0092] Connect in parallel at the same branch point n N-1 One end of all the N-th branch cables is connected to the load impedance respectively. Therefore, when calculating the N-th branch cable, the connected load impedance is directly used. The transfer parameter matrix and the load impedance are used to calculate the equivalent input impedance of the N-th branch cable m according to the following relationship:

[0093]

[0094] In the formula, is the equivalent input impedance of the Nth branch cable m, Z Lm is the load impedance of the Nth branch cable m, They are respectively the first transfer parameter, the second transfer parameter, the third transfer parameter and the fourth transfer parameter of the transfer parameter matrix of the Nth-level branch cable m.

[0095] Calculate the equivalent input impedance of the Nth branch cable m The parallel resistance value is connected at the same branch point n N-1 The equivalent load impedance of the N-1th branch cable.

[0096] Step 2.2.2, obtain the transfer parameter matrix and equivalent load impedance of all N-1th branch cables connected in parallel at the same branch point, first calculate the equivalent input impedance of all N-1th branch cables, and then calculate the parallel resistance of each equivalent input impedance as the equivalent load impedance of the N-2th branch cable connected to the same branch point.

[0097] Similarly, the transfer parameter matrix and equivalent load impedance of all first-level branch cables connected in parallel at the same branch point are obtained, the equivalent input impedance of all first-level branch cables is calculated first, and then the parallel resistance of each equivalent input impedance is calculated as the equivalent load impedance of the zero-level branch cable connected to the same branch point.

[0098] When d=0,1,2,…,N-1, the equivalent input impedance of the d-th branch cable m satisfies the following relationship:

[0099]

[0100] In the formula, is the equivalent input impedance of the d-th branch cable m, is the equivalent load impedance of the d-th branch cable m connection, They are respectively the first transfer parameter, the second transfer parameter, the third transfer parameter and the fourth transfer parameter of the transfer parameter matrix of the d-th level branch cable m.

[0101] Through step 2.2, the present invention converts the equivalent circuit distributed parameter model of the branch cable at this level into a concentrated circuit parameter model based on the transfer parameter matrix of each branch cable, and then embeds it into the transfer parameter matrix of the branch cable at the previous level.

[0102] In a non-limiting preferred embodiment, according to formula (3), Figure 3 As shown, the transfer parameter matrices of the zero-level branch cable Cable 1, the first-level branch cable Cable 2, and the first-level branch cable Cable 3 are obtained respectively, satisfying the following relationship:

[0103]

[0104] In the formula,

[0105] U 1in , U 2in , U 3in They are the input voltages of the zero-level branch cable Cable 1, the first-level branch cable Cable 2, and the first-level branch cable Cable 3 respectively;

[0106] U 1out U 2out U 3out

[0107] , , are the output voltages of the zero-level branch cable Cable 1, the first-level branch cable Cable 2, and the first-level branch cable Cable 3 respectively;

[0108] I 1in ,I 2in ,I 3in They are the input currents of the zero-level branch cable Cable 1, the first-level branch cable Cable 2, and the first-level branch cable Cable 3 respectively;

[0109] I 1out ,I 2out ,I 3out They are the output currents of the zero-level branch cable Cable 1, the first-level branch cable Cable 2, and the first-level branch cable Cable 3 respectively;

[0110] are the first transfer parameter, the second transfer parameter, the third transfer parameter and the fourth transfer parameter of the transfer parameter matrix of the d-th branch cable m, respectively, dmis the attenuation coefficient of the d-th branch cable m, l dm is the length of the d-th branch cable m, is the characteristic impedance of the d-th branch cable m, where d=0,1, m=1,2,3.

[0111] In a non-limiting preferred embodiment, according to formula (4), Figure 3 As shown, the first-level branch cable Cable2 and the first-level branch cable Cable3 are equivalent to the lumped parameter circuit model, and the input impedance Z of the first-level branch cable Cable2 is obtained when the first branch node n1 is used as the signal injection end. in2 , the input impedance Z of the first branch cable Cable 3 in3 They satisfy the following relationships respectively:

[0112]

[0113] In the formula, Z L12 , Z L13 They are the load impedances of the first-level branch cable Cable 2 and the first-level branch cable Cable 3 respectively.

[0114] Figure 3 The first-level branch cable Cable 2 and the first-level branch cable Cable 3 are connected in parallel to obtain the equivalent load impedance Z of the zero-level branch cable Cable 1. n1 ,like Figure 4 shown.

[0115] Step 2.3, using the equivalent load impedance of each level of branch cables, obtain the equivalent transfer parameter matrix after each branch node.

[0116] By calculating the parallel resistance of the input impedance of the first-level branch cable Cable 2 and the input impedance of the first-level branch cable Cable 3, it is deduced that the equivalent transfer parameter matrix after the first branch node n1 satisfies the following relationship:

[0117]

[0118] In the formula, They are respectively the first transfer parameter, the second transfer parameter, the third transfer parameter and the fourth transfer parameter of the equivalent transfer parameter matrix after the first branch node n1.

[0119] In a non-limiting preferred embodiment, Figure 3 As shown, the equivalent transfer parameter matrix after the first branch node n1 satisfies the following relationship:

[0120]

[0121] Step 2.4, the equivalent transfer parameter matrix of the multi-branch cable network is obtained by multiplying the transfer parameter matrix of the zeroth-order branch cable by the transfer parameter matrices of the subsequent branch cables at each level.

[0122] It can be seen from the above formula that the equivalent transfer parameter matrix of the Y-type multi-branch cable network is the product of the equivalent transfer parameter matrix after the first branch node n1 and the transfer parameter matrix of the zero-level branch cable; and the equivalent transfer parameter matrix after the first branch node n1 is the product of the equivalent transfer parameter matrix after the second branch node n2 and the transfer parameter matrix of the first-level branch cable; and so on, the equivalent transfer parameter matrix of the multi-branch cable network is obtained by multiplying the transfer parameter matrix of the zero-level branch cable and the transfer parameter matrix of the subsequent branches at all levels; therefore, the equivalent transfer parameter matrix of the multi-branch cable network satisfies the following relationship:

[0123]

[0124] Wherein, A, B, C, and D are respectively the first transfer parameter, the second transfer parameter, the third transfer parameter, and the fourth transfer parameter of the equivalent transfer parameter matrix of the multi-branch cable network.

[0125] Step 3: Using the load impedance and equivalent transfer parameter matrix, a broadband impedance spectrum model of the multi-branch cable network is established.

[0126] The broadband impedance spectrum model of the multi-branch cable network satisfies the following relationship:

[0127]

[0128] The following simulation case is given to demonstrate the effectiveness of the broadband impedance spectrum modeling method for the constructed multi-branch cable system. The ZC-YJV-26 / 35kV-2×400 power cable is taken as the research object, and the relevant parameters are shown in Table 1. A Y-type cable line is built. The line topology is as follows Figure 5 As shown. Use PSCAD software to build Figure 5 The simulated line is shown in the figure, and the Harmonic Impedance module is used to simulate the network analyzer to perform a frequency sweep test on the line. Then, in the MATLAB mathematical calculation software, the patented multi-branch cable system broadband impedance spectrum model is used to calculate the input impedance of the head end of the cable system.

[0129] Table 1 Structural parameters of ZC-YJV-26 / 35kV-2×400 power cable

[0130] structure Outer diameter(mm) Copper conductor 23.1 Extruded conductor shield 24.7 XLPE insulation 43.9 Extruded insulation shield 45.2 Copper tape shielding 45.5

[0131] Figure 6 and Figure 7They are the simulated line frequency sweep results and the model solution results of the first-end input impedance amplitude spectrum. It can be seen that the proposed model results are almost completely consistent with the simulated line frequency sweep results, which proves the correctness of the proposed model establishment method.

[0132] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0133] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0134] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0135] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for establishing a broadband impedance spectrum model of a multi-branch cable network, wherein the multi-branch cable network comprises a plurality of branch cables connected in series, and one end of the multi-branch cable network is connected to a load impedance, characterized in that: include: Collect the characteristic impedance and attenuation coefficient of a single branch cable and construct the transfer parameter matrix of a single branch cable; The output end of any branch cable is used as the signal injection end, and the equivalent transfer parameter matrix of the multi-branch cable network is obtained by multiplying the transfer parameter matrix of the branch cable with the transfer parameter matrices of the remaining branch cables; A broadband impedance spectrum model of multi-branch cable network is established using load impedance and equivalent transfer parameter matrix.

2. The method for establishing a broadband impedance spectrum model of a multi-branch cable network according to claim 1, characterized in that: Collect the characteristic impedance and attenuation coefficient of a single branch cable and construct the transfer parameter matrix of a single branch cable, including: Collect the dielectric parameters and dimensional parameters of the cable and construct the distributed parameter equivalent circuit of a single branch cable; Based on the distributed parameter equivalent circuit of a single branch cable, the characteristic impedance and attenuation coefficient of a single branch cable are calculated, which respectively satisfy the following relationships: In the formula, Z 0 is the characteristic impedance, γ is the attenuation coefficient, R, L, C, G represent the distributed resistance, distributed inductance, distributed capacitance, and distributed conductance of the cable respectively, and α and β are the real and imaginary parts of the attenuation coefficient respectively; Using characteristic impedance and attenuation coefficient, a transfer parameter matrix is ​​constructed to represent the relationship between the voltage and current signals at the head end and the voltage and current signals at the end of a single branch cable, satisfying the following relationship: Where U in ,I in are the input voltage and current at the head end of a single branch cable, U out ,I out They are the output voltage and current at the end of a single branch cable, is the constructed transfer parameter matrix, the first transfer parameter and the fourth transfer parameter are cosh(γl), the second transfer parameter Z 0 sinh(γl), the third transfer parameter is sinh(γl) / Z 0 , l represents the cable length.

3. The method for establishing a broadband impedance spectrum model of a multi-branch cable network according to claim 2, characterized in that: The transfer parameter matrices of each branch cable are different.

4. The method for establishing a broadband impedance spectrum model of a multi-branch cable network according to claim 1, characterized in that: The broadband impedance spectrum model of the multi-branch cable network satisfies the following relationship: In the formula, Z in is the broadband impedance spectrum of the multi-branch cable network, Z L is the load impedance of the cable, and A, B, C, and D are respectively the first transfer parameter, the second transfer parameter, the third transfer parameter, and the fourth transfer parameter of the equivalent transfer parameter matrix of the multi-branch cable network.

5. The method for establishing a broadband impedance spectrum model of a multi-branch cable network according to claim 4, characterized in that: The equivalent transfer parameter matrix of the multi-branch cable network satisfies the following relationship: In the formula, are respectively a first transfer parameter, a second transfer parameter, a third transfer parameter and a fourth transfer parameter of an equivalent transfer parameter matrix after the first branch node n1; They are respectively the first transfer parameter, the second transfer parameter, the third transfer parameter and the fourth transfer parameter of the transfer parameter matrix of the zeroth-order branch cable.

6. The method for establishing a broadband impedance spectrum model of a multi-branch cable network according to claim 1, characterized in that: The output end of any branch cable is used as the signal injection end, and the equivalent transfer parameter matrix of the multi-branch cable network is obtained by multiplying the transfer parameter matrix of the branch cable with the transfer parameter matrices of the remaining branch cables, including: According to the direction of signal transmission from the injection end to the load impedance, the number of branch points between the input end of each branch cable and the signal injection end is used as the grade of the branch cable, and the branch cables of the same grade connected to the same branch point are in a parallel connection relationship; Starting from the Nth-order branch cable, the equivalent load impedance of the previous-order branch cable connected at the same branch point is calculated using the transfer parameter matrix and equivalent load impedance of the branch cable of the same order connected in parallel at the same branch point; and so on; finally, the equivalent load impedance of the zeroth-order branch cable is obtained; The equivalent transfer parameter matrix after each branch node is obtained by using the equivalent load impedance of each branch cable; The equivalent transfer parameter matrix of the multi-branch cable network is obtained by multiplying the transfer parameter matrix of the zeroth-order branch cable and the transfer parameter matrices of the subsequent branch cables at each level.

7. The method for establishing a broadband impedance spectrum model of a multi-branch cable network according to claim 6, characterized in that: Starting from the Nth branch cable, the equivalent load impedance of the previous branch cable connected at the same branch point is calculated using the transfer parameter matrix and equivalent load impedance of the branch cables of the same level connected in parallel at the same branch point; And so on; Finally, the equivalent load impedance of the zero-order branch cable is obtained, including: Obtain the transfer parameter matrix and load impedance of all N-th branch cables connected in parallel at the same branch point, first calculate the equivalent input impedance of all N-th branch cables, and then calculate the parallel resistance of each equivalent input impedance as the equivalent load impedance of the N-1-th branch cable connected at the same branch point; Obtain the transfer parameter matrix and equivalent load impedance of all N-1th branch cables connected in parallel at the same branch point, first calculate the equivalent input impedance of all N-1th branch cables, and then calculate the parallel resistance of each equivalent input impedance as the equivalent load impedance of the N-2th branch cable connected to the same branch point.

8. The method for establishing a broadband impedance spectrum model of a multi-branch cable network according to claim 7, characterized in that: The equivalent input impedance of the Nth branch cable m is calculated using the following relationship: In the formula, is the equivalent input impedance of the Nth branch cable m, Z Lm is the load impedance of the Nth branch cable m, are respectively a first transfer parameter, a second transfer parameter, a third transfer parameter and a fourth transfer parameter of a transfer parameter matrix of an N-th level branch cable m; Calculate the equivalent input impedance of the Nth branch cable m The parallel resistance is connected at the same branch point n N-1 The equivalent load impedance of the N-1th branch cable.

9. The method for establishing a broadband impedance spectrum model of a multi-branch cable network according to claim 8, characterized in that: When d=0,1,2,…,N-1, the equivalent input impedance of the d-th branch cable m satisfies the following relationship: In the formula, is the equivalent input impedance of the d-th branch cable m, is the equivalent load impedance of the d-th branch cable m connection, They are respectively the first transfer parameter, the second transfer parameter, the third transfer parameter and the fourth transfer parameter of the transfer parameter matrix of the d-th level branch cable m.

10. A broadband impedance spectrum modeling system for a multi-branch cable network, characterized in that: include: The transfer parameter matrix calculation module is used to collect the characteristic impedance and attenuation coefficient of a single branch cable and construct the transfer parameter matrix of a single branch cable; An equivalent transfer parameter matrix calculation module is used to use the output end of any branch cable as the signal injection end, and obtain the equivalent transfer parameter matrix of the multi-branch cable network by multiplying the transfer parameter matrix of the branch cable with the transfer parameter matrices of the remaining branch cables; The broadband impedance spectrum model building module is used to build a broadband impedance spectrum model of a multi-branch cable network using load impedance and an equivalent transfer parameter matrix.

11. The broadband impedance spectrum modeling system for a multi-branch cable network according to claim 10, characterized in that: The transfer parameter matrix calculation module includes: a distributed parameter equivalent circuit unit, a characteristic impedance and attenuation coefficient calculation unit, and a transfer parameter matrix unit; Distributed parameter equivalent circuit unit, used to collect the dielectric parameters and size parameters of the cable and construct the distributed parameter equivalent circuit of a single branch cable; A characteristic impedance and attenuation coefficient calculation unit, used to calculate the characteristic impedance and attenuation coefficient of a single branch cable based on a distributed parameter equivalent circuit of the single branch cable; The transfer parameter matrix unit is used to construct a transfer parameter matrix representing the relationship between the voltage and current signals at the head end and the voltage and current signals at the end of a single branch cable by using characteristic impedance and attenuation coefficient.

12. The broadband impedance spectrum modeling system for a multi-branch cable network according to claim 10, characterized in that: The equivalent transfer parameter matrix calculation module includes: a branch cable topology construction unit, an equivalent load impedance calculation unit, and an equivalent transfer parameter matrix unit; The branch cable topology construction unit is used to determine the level of the branch cable according to the direction in which the signal is transmitted from the injection end to the load impedance, with the number of branch points between the input end of each branch cable and the injection end of the signal being used as the level of the branch cable, and the branch cables of the same level connected to the same branch point being in a parallel connection relationship; The equivalent load impedance calculation unit is used to calculate the equivalent load impedance of the previous branch cable connected to the same branch point starting from the Nth branch cable, using the transfer parameter matrix and equivalent load impedance of the branch cables of the current level connected in parallel to the same branch point; and so on; and finally obtain the equivalent load impedance of the zeroth branch cable; The equivalent transfer parameter matrix unit is used to obtain the equivalent transfer parameter matrix after each branch node by using the equivalent load impedance of each level of branch cables; the equivalent transfer parameter matrix of the multi-branch cable network is obtained by multiplying the transfer parameter matrix of the zeroth level branch cable and the transfer parameter matrix of the subsequent levels of branch cables.

13. A terminal comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 9.

14. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 9 are implemented.

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