A cable resonance active evasion method and system

Abstract

The application discloses a kind of cable resonance active avoidance method and system, belong to harmonic suppression technical field.Method includes: the three-phase voltage and current of converter and cable feeder connection port are collected, determine sampling frequency according to upper limit of analysis band twice principle, determine sampling time length according to the reciprocal of resonance analysis frequency accuracy;Fourier calculation is carried out to sampling data, obtain frequency spectrum and phase sequence;The active power spectrum of harmonic is calculated, when its active power ratio with fundamental wave exceeds threshold k%, resonance is judged and source head disturbance equipment is locked;If equipment adjustable switching frequency, calculate optimal switching frequency according to cable distribution parameter and adjust;If it is not adjustable, calculate optimal cable length, and resonance avoidance is realized by additional length switching or standby line switching.The application solves the problem that traditional method is difficult to identify and actively avoid resonance online, improves power grid operation stability, and is suitable for high cable rate, high power electronic proportion system.

Description

Technical Field

[0001] This invention belongs to the field of harmonic suppression technology, specifically relating to a method and system for actively avoiding cable resonance. Background Technology

[0002] With the development of the new energy industry and the advancement of urbanization, converters of different types and switching frequencies emit abundant ultra-high order harmonic disturbances into the power grid. These disturbances can easily trigger harmonic amplification and even resonance problems in cable feeders of urban power distribution networks, introducing local overvoltage and overcurrent risks into power cables and jeopardizing the stable operation of the urban power grid. However, due to the numerous disturbance frequencies of power electronic equipment and the strong time-varying nature of cable length and operating environment, the resonance phenomenon in these cable feeders exhibits characteristics such as wide frequency bands, time-varying nature, and high uncertainty, making its identification and avoidance quite difficult.

[0003] Existing research on cable resonance involves treating power cables as equivalent lumped-parameter or distributed-parameter models, utilizing the harmonic amplification of long cables at different frequency bands for resonance principle analysis and suppression guidance. However, these methods rely on the amplification of harmonic current as the criterion for resonance phenomena. This physical quantity is often unavailable in the line, and no significantly distorted harmonic current can be observed at the resonant source port. This limits the online application of such resonance suppression methods in practical systems, making them suitable only for post-resonance problem assessment and post-event remediation of related suppression schemes.

[0004] Therefore, in order to effectively identify and actively avoid cable resonance in systems with high cable coverage and high power electronics ratios, this invention, based on distortion power theory, uses Fourier decomposition to calculate the active power of high-frequency harmonics and identifies cable resonance based on its numerical characteristics. Furthermore, based on this, an active cable resonance avoidance method based on switching frequency changes and cable length adjustments is designed, achieving online active avoidance of cable resonance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a cable resonance active avoidance method and system to address the shortcomings of the prior art. Based on the principle of distorted power, the method identifies resonance through harmonic active power. At the same time, it combines the cable distributed parameter model to complete the configuration of the optimal switching frequency and the optimal cable length based on harmonic active power. This method is used to solve the technical problem that traditional cable harmonic amplification analysis methods cannot meet the requirements of resonance identification and online avoidance.

[0006] The present invention adopts the following technical solution: A method for actively avoiding cable resonance includes the following steps: S1. Collect the port physical quantities of the converter connection cable feeder system, including three-phase voltage and three-phase current. Determine the sampling frequency according to the principle of twice the upper limit of the analysis frequency band, and determine the sampling duration according to the reciprocal of the accuracy of the resonance analysis frequency to obtain the physical quantity sampling results. S2. Based on the physical quantity sequence obtained in step S1, and combined with the sampling frequency and sampling duration, perform Fourier calculation to obtain the spectrum sequence of the physical quantity amplitude and phase of the sampling node. S3. Based on the spectrum sequence obtained in step S2, calculate the harmonic active power spectrum of the sampling node, set the resonance judgment threshold, and when the ratio of the value in the harmonic active power spectrum to the fundamental active power exceeds the threshold, determine that cable resonance has occurred, and lock the source disturbance device of cable resonance based on the harmonic active power spectrum. S4. Determine whether the source disturbance device can modify the switching frequency. If it can, calculate the optimal switching frequency based on the distribution parameters of the power cable, and adjust the switching frequency of the source disturbance device to the optimal switching frequency to avoid cable resonance. S5. If the source disturbance device cannot modify the switching frequency, the optimal cable length is calculated based on the distribution parameters of the power cable, and the cable length is adjusted to the optimal cable length by online switching of the additional length of the cable feeder or switching of the backup feeder line to avoid cable resonance.

[0007] Preferably, in step S1, the sampling frequency is twice the upper limit of the analysis frequency band, and the sampling duration is the reciprocal of the resonant analysis frequency accuracy.

[0008] Preferably, in step S2, the Fourier calculation includes calculating the three-phase voltage spectrum and phase, and the three-phase current spectrum and phase.

[0009] Preferably, in step S3, the harmonic active power spectrum is calculated as follows:

[0010] in, This is the three-phase voltage spectrum. For three-phase voltage phase, The three-phase current spectrum, This refers to the phase of the three-phase current.

[0011] Preferably, in step S3, the resonance determination threshold is set to... k %, k This is the preset percentage.

[0012] Preferably, in step S4, calculating the optimal switching frequency includes: Obtain the distributed parameters of the cable, including distributed capacitance, distributed resistance, and distributed inductance per meter; Calculate the characteristic parameters of the cable; Calculate the unit value of the resonant frequency shift based on the cable length and resonant frequency; Adjust the switching frequency so that the switching frequency corresponding to the resonant frequency or an integer multiple thereof is adjusted to the optimal switching frequency.

[0013] Preferably, the optimal switching frequency is ,in, The resonant frequency, The total length of the cable in the resonance participation and propagation path, For distributed inductance, This is the distributed capacitance.

[0014] Preferably, in step S5, calculating the optimal cable length includes: Obtain the cable's distributed parameters; calculate the optimal cable length change based on the resonant frequency and cable characteristic parameters; the adjusted optimal cable length is the current cable length plus or minus the optimal cable length change.

[0015] Preferably, the optimal cable change length is ,in, The resonant frequency, The total length of the cable in the resonance participation and propagation path, For distributed inductance, This is the distributed capacitance.

[0016] Secondly, embodiments of the present invention provide an active cable resonance avoidance system, comprising: The acquisition module collects the port physical quantities of the converter connection cable feeder system, including three-phase voltage and three-phase current. The sampling frequency is determined according to the principle of twice the upper limit of the analysis frequency band, and the sampling duration is determined according to the reciprocal of the accuracy of the resonance analysis frequency to obtain the physical quantity sampling results. The calculation module performs Fourier calculations based on the physical quantity sequence sampled in the acquisition module, combined with the sampling frequency and sampling duration, to obtain the spectrum sequence of the physical quantity amplitude and phase of the sampling node. The determination module calculates the harmonic active power spectrum of the sampling node based on the spectrum sequence obtained from the calculation module, sets a resonance determination threshold, and determines that cable resonance has occurred when the ratio of the value in the harmonic active power spectrum to the fundamental active power exceeds the threshold. The module also locks the source of the cable resonance disturbance device based on the harmonic active power spectrum. The adjustment module determines whether the source disturbance device can modify the switching frequency. If it can, it calculates the optimal switching frequency based on the distribution parameters of the power cable and adjusts the switching frequency of the source disturbance device to the optimal switching frequency to avoid cable resonance. If the source disturbance device cannot modify the switching frequency, the output module calculates the optimal cable length based on the distribution parameters of the power cable, and adjusts the cable length to the optimal cable length by online switching of the additional length of the cable feeder or switching of the backup feeder line to avoid cable resonance.

[0017] Thirdly, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the steps of the above-described cable resonance active avoidance method.

[0018] Fourthly, embodiments of the present invention provide a computer-readable storage medium including a computer program, which, when executed by a processor, implements the steps of the above-described cable resonance active avoidance method.

[0019] Fifthly, a chip includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described cable resonance active avoidance method.

[0020] In a sixth aspect, embodiments of the present invention provide an electronic device including a computer program, which, when executed by the electronic device, implements the steps of the above-described cable resonance active avoidance method.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects: A method for active cable resonance avoidance is proposed, which identifies resonance based on harmonic active power rather than traditional harmonic current, thus solving the problem of difficulty in obtaining harmonic current online. By actively adjusting the switching frequency or cable length, online resonance avoidance is achieved, avoiding the limitations of post-event remediation. The method is applicable to systems with high cable coverage and high power electronics ratio, improving power grid stability and reliability, and reducing the risk of local overvoltage and overcurrent.

[0022] Furthermore, the sampling frequency is based on twice the upper limit of the analysis frequency band, ensuring no frequency aliasing in the sampled data and improving data accuracy; the sampling duration is based on the reciprocal of the resonance analysis frequency accuracy, guaranteeing spectral resolution and providing a reliable foundation for subsequent Fourier calculations, thereby improving the accuracy and reliability of resonance identification.

[0023] Furthermore, by comprehensively acquiring the frequency domain characteristics of voltage and current, complete data support is provided for the calculation of harmonic active power; the consideration of three-phase systems enhances the applicability of the method, accurately reflects the harmonic characteristics of the actual power grid, and improves the comprehensiveness and accuracy of resonance identification.

[0024] Furthermore, the calculation method for harmonic active power was clarified. By combining the amplitude and phase difference of voltage and current, the scientific nature and repeatability of the calculation were ensured. This calculation method is based on the distortion power theory and can effectively capture the energy changes at resonance, providing a quantitative basis for resonance determination.

[0025] Furthermore, by setting a percentage threshold (such as k%), a clear standard for judging resonance is provided, avoiding subjective misjudgment. The threshold is based on the ratio of harmonic active power to fundamental active power, reflecting the severity of resonance and making the judgment process more objective and reliable.

[0026] Furthermore, characteristic parameters are calculated based on cable distributed parameters (such as distributed capacitance, resistance, and inductance) to ensure the scientific nature of frequency adjustment; the optimal switching frequency is calculated by the unit value of resonant frequency shift, so that the adjusted frequency can effectively avoid the resonant point, achieving precise avoidance of resonance.

[0027] Furthermore, the magnitude of frequency adjustment is clarified, which facilitates practical application and automation; by adjusting the switching frequency to the optimal value, resonance can be quickly avoided, reducing computational complexity and improving system response speed.

[0028] Furthermore, calculating the optimal change length based on cable distribution parameters and resonant frequency provides another effective means of resonance avoidance; adjusting the cable length by online switching or switching of backup lines enhances the system's flexibility and adaptability.

[0029] Furthermore, specific values ​​for the length adjustment are provided to ensure the accuracy of the avoidance measures; the adjusted cable length can disrupt the resonance condition, effectively prevent harmonic amplification, and improve power grid safety.

[0030] It is understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0031] In summary, this invention identifies resonance by harmonic active power and, combined with adjustments to switching frequency and cable length, achieves online active avoidance of cable resonance, overcoming the shortcomings of traditional methods that rely on harmonic currents and cannot be applied online. The method is scientific, the system is reliable, and it improves power grid stability and security, making it suitable for systems with a high proportion of power electronics.

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0033] Figure 1 Topology diagram of converter connection cable feeder system; Figure 2This refers to the spatial distribution of physical quantities such as harmonic active power and harmonic reactive power when resonance occurs. Figure 3 The relationship between ultra-high harmonic active power at the cable sampling node and cable length; Figure 4 The relationship between ultra-high harmonic active power and disturbance frequency at the cable sampling node; Figure 5 This is a schematic diagram of the method flow of the present invention; Figure 6 A schematic diagram of a computer device provided in an embodiment of the present invention; Figure 7 This is a block diagram of a chip provided according to an embodiment of the present invention.

[0034] Among them, 60. Computer equipment; 61. Processor; 62. Memory; 63. Computer program; 600. Electronic device; 610. Processing unit; 620. Storage unit; 6201. Random access memory unit; 6202. Cache memory unit; 6203. Read-only memory unit; 6204. Program / utility; 6205. Program module; 630. Bus; 640. Display unit; 650. Input / output interface; 660. Network adapter; 700. External device. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0037] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0038] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this invention generally indicates that the preceding and following objects have an "or" relationship.

[0039] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0040] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0041] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0042] This invention provides an active cable resonance avoidance method. It collects physical quantities at the ports of the converter-connected cable feeder system, which can be acquired by the converter in real time, and performs online identification of cable resonance. Simultaneously, the online identification results can guide online adjustment of the converter's switching frequency, online switching of the cable feeder length, and backup line switching; it provides optimal parameter guidance for multiple types of cable resonance avoidance schemes. It can provide the optimal adjustment frequency point for the switching frequency and the optimal change length for the cable feeder.

[0043] Please see Figure 5 The present invention provides an active avoidance method for cable resonance, comprising the following steps: S1. Determine the sampling frequency based on the principle of twice the upper limit of the analysis frequency band. Determine the sampling nodes, i.e. Figure 1 The system's converter equipment is connected to the cable feeder port; the sampled physical quantities are three-phase voltage and three-phase current, and the sampling duration is determined based on the reciprocal of the resonance analysis frequency accuracy. ; Obtain the physical quantity sampling results; The physical quantity sampling results include: Three-phase voltage sequence Three-phase current sequence .

[0044] S2. Based on the physical quantity sequences obtained from sampling in step S1, combined with the sampling frequency... Sampling duration Fourier transform is performed to obtain the spectral sequence of the amplitude and phase of the physical quantities at the sampling nodes; The specific spectral sequences of the physical quantity amplitude and phase at the sampling node are as follows: Three-phase voltage spectrum and phase Three-phase current spectrum and phase .

[0045] S3. Based on the spectrum and phase of the three-phase voltage and current of the sampling node obtained in step S2, calculate the harmonic active power spectrum of the sampling node. For the three-phase voltage spectrum of this node and phase Three-phase current spectrum and phase The formula for calculating its harmonic active power spectrum is:

[0046] In this way, the harmonic active power spectrum of the sampling node is obtained.

[0047] Set resonance determination threshold k %, when the value of the harmonic active power spectrum at a certain node With fundamental active power The ratio exceeds k When the value reaches %, it is determined that cable resonance has occurred at that point. Simultaneously, based on the harmonic active power spectrum exceeding... k % of the resonant frequency f r The switching frequency of each power electronic device connected to the sampling node and its integer multiples are numerically matched to lock the source disturbance device of cable resonance.

[0048] S4. Determine whether the switching frequency of the source disturbance equipment can be modified. If so, calculate the optimal switching frequency based on the distributed parameters of the power cable; Calculate the cable's distributed parameters based on the cable model specifications or physical parameters: distributed capacitance per meter. c Distributed resistance r Distributed inductance l ; Calculate characteristic parameters using cable parameters , ,in .

[0049] Obtain the total length of the cable in the resonant participation and propagation path. h The calculated value of the resonant frequency frequency shift unit is: ; By adjusting the switching frequency of the source disturbance device, it is made to resonate with the frequency. The corresponding switching frequency or an integer multiple thereof is adjusted to This is to avoid cable resonance.

[0050] S5. If the solution of adjusting the switching frequency of the source disturbance equipment in step S4 is not feasible, then the optimal cable length is calculated based on the distribution parameters of the power cable, and the current cable length is adjusted to the optimal cable length by online switching of the additional length of the cable feeder or switching to the backup feeder line. The optimal cable length is calculated as follows: Therefore, the optimal cable length after adjustment should be: Cable resonance can be avoided by adjusting the length of the power cable to this value.

[0051] In another embodiment of the present invention, a cable resonance active avoidance system is provided. This system can be used to implement the above-mentioned cable resonance active avoidance method. Specifically, the cable resonance active avoidance system includes an acquisition module, a calculation module, a judgment module, an adjustment module, and an output module.

[0052] The acquisition module collects the port physical quantities of the converter connection cable feeder system, including three-phase voltage and three-phase current. The sampling frequency is determined according to the principle of twice the upper limit of the analysis frequency band, and the sampling duration is determined according to the reciprocal of the accuracy of the resonance analysis frequency to obtain the physical quantity sampling results. The calculation module performs Fourier calculations based on the physical quantity sequence sampled in the acquisition module, combined with the sampling frequency and sampling duration, to obtain the spectrum sequence of the physical quantity amplitude and phase of the sampling node. The determination module calculates the harmonic active power spectrum of the sampling node based on the spectrum sequence obtained from the calculation module, sets a resonance determination threshold, and determines that cable resonance has occurred when the ratio of the value in the harmonic active power spectrum to the fundamental active power exceeds the threshold. The module also locks the source of the cable resonance disturbance device based on the harmonic active power spectrum. The adjustment module determines whether the source disturbance device can modify the switching frequency. If it can, it calculates the optimal switching frequency based on the distribution parameters of the power cable and adjusts the switching frequency of the source disturbance device to the optimal switching frequency to avoid cable resonance. If the source disturbance device cannot modify the switching frequency, the output module calculates the optimal cable length based on the distribution parameters of the power cable, and adjusts the cable length to the optimal cable length by online switching of the additional length of the cable feeder or switching of the backup feeder line to avoid cable resonance.

[0053] This invention provides a terminal device comprising a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, graphics processing units (GPUs), tensor processing units (TPUs), digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to achieve a corresponding method flow or corresponding function. The processor described in this embodiment can be used in the operation of a cable resonance active avoidance method, including: The physical quantities at the ports of the converter connection cable feeder system, including three-phase voltage and three-phase current, are collected. The sampling frequency is determined based on twice the upper limit of the analysis frequency band, and the sampling duration is determined based on the reciprocal of the resonance analysis frequency accuracy, yielding the physical quantity sampling results. Based on the sampled physical quantity sequence, combined with the sampling frequency and sampling duration, Fourier transform calculations are performed to obtain the spectrum sequence of the amplitude and phase of the physical quantities at the sampling nodes. Based on the obtained spectrum sequence, the harmonic active power spectrum of the sampling nodes is calculated, and a resonance judgment threshold is set. When the ratio of the value in the harmonic active power spectrum to the fundamental active power exceeds the threshold, a resonance judgment is made. The system identifies cable resonance and pinpoints the source of the resonance disturbance based on the harmonic active power spectrum. It then determines whether the source disturbance device can modify its switching frequency. If it can, the system calculates the optimal switching frequency based on the power cable's distribution parameters and adjusts the switching frequency of the source disturbance device to the optimal frequency to avoid cable resonance. If the source disturbance device cannot modify its switching frequency, the system calculates the optimal cable length based on the power cable's distribution parameters and adjusts the cable length to the optimal length by online switching of the additional cable feeder length or switching of the backup feeder line to avoid cable resonance.

[0054] Please see Figure 6 The terminal device is a computer device. In this embodiment, the computer device 60 includes a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When the processor 61 executes the computer program 63, it implements the cable resonance active avoidance method described in this embodiment. To avoid repetition, these details are not elaborated here. Alternatively, when the processor 61 executes the computer program 63, it implements the functions of each model / unit in the cable resonance active avoidance system of this embodiment. To avoid repetition, these details are not elaborated here.

[0055] Computer device 60 can be a desktop computer, laptop, handheld computer, cloud server, or other computing device. Computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will understand that... Figure 6 This is merely an example of computer device 60 and does not constitute a limitation on computer device 60. It may include more or fewer components than shown, or combine certain components, or different components. For example, computer device may also include input / output devices, network access devices, buses, etc.

[0056] The processor 61 may be a Central Processing Unit (CPU), or other general-purpose processors, graphics processing units (GPUs), tensor processing units (TPUs), digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0057] The memory 62 can be an internal storage unit of the computer device 60, such as a hard disk or RAM of the computer device 60. The memory 62 can also be an external storage device of the computer device 60, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., provided on the computer device 60.

[0058] Furthermore, the memory 62 may include both internal storage units of the computer device 60 and external storage devices. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 can also be used to temporarily store data that has been output or will be output.

[0059] Please see Figure 7 The terminal device is an electronic device 600, which is manifested in the form of a general-purpose computing device. The components of the electronic device may include, but are not limited to: at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different platform components (including storage unit 620 and processing unit 610), a display unit 640, etc.

[0060] The storage unit stores program code, which can be executed by the processing unit 610 to perform the steps described in the method section of this specification according to various exemplary embodiments of the present invention. For example, the processing unit 610 can perform actions such as... Figure 5 The steps are shown in the figure.

[0061] Storage unit 620 may include a readable medium in the form of a volatile storage unit, such as random access memory (RAM) 6201 and / or cache memory 6202, and may further include a read-only memory (ROM) 6203.

[0062] Storage unit 620 may also include a program / utility 6204 having a set (at least one) program module 6205, such program module 6205 including but not limited to: operating system, one or more application programs, other program modules and program data, each or some combination of these examples may include an implementation of a network environment.

[0063] Bus 630 can represent one or more of several types of bus structures, including a memory cell bus or memory cell controller, a peripheral bus, a graphics acceleration port, a processing unit, or a local bus using any of the multiple bus structures.

[0064] Electronic device 600 can also communicate with one or more external devices 700 (e.g., keyboard, pointing device, Bluetooth device, etc.), and with one or more devices that enable a user to interact with electronic device 600, and / or with any device that enables electronic device 600 to communicate with one or more other computing devices (e.g., router, modem). This communication can be performed via input / output interface 650. Furthermore, electronic device 600 can also communicate with one or more networks (e.g., local area network, wide area network, and / or public network, such as the Internet) via network adapter 660. Network adapter 660 can communicate with other modules of electronic device 600 via bus 630. It should be understood that, although not shown in the figures, other hardware and / or software modules can be used in conjunction with electronic device 600, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage platforms.

[0065] Example 4 This invention also provides a storage medium, specifically a computer-readable storage medium, which is a memory device in a terminal device for storing programs and data. It is understood that the computer-readable storage medium here can include both built-in storage media in the terminal device and extended storage media supported by the terminal device; it can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for loading and execution by a processor, which can be one or more computer programs (including program code). More specific examples of the computer-readable storage medium include: an electrical connection with one or more wires, a portable disk, a hard disk, random access memory, read-only memory, erasable programmable read-only memory, optical fiber, portable compact disk read-only memory, optical storage device, magnetic storage device, or any suitable combination thereof.

[0066] Computer-readable storage media also include data signals propagated in baseband or as part of a carrier wave, carrying readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A readable storage medium can also be any readable medium other than a readable storage medium that can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the readable storage medium can be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, radio frequency, etc., or any suitable combination thereof.

[0067] Program code for performing the operations of this invention can be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java and C++, and conventional procedural programming languages ​​such as C or similar languages. The program code can execute entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0068] One or more instructions stored in a computer-readable storage medium can be loaded and executed by a processor to implement the corresponding steps of the active cable resonance avoidance method in the above embodiments; one or more instructions in the computer-readable storage medium are loaded and executed by the processor in the following steps: The physical quantities at the ports of the converter connection cable feeder system, including three-phase voltage and three-phase current, are collected. The sampling frequency is determined based on twice the upper limit of the analysis frequency band, and the sampling duration is determined based on the reciprocal of the resonance analysis frequency accuracy, yielding the physical quantity sampling results. Based on the sampled physical quantity sequence, combined with the sampling frequency and sampling duration, Fourier transform calculations are performed to obtain the spectrum sequence of the amplitude and phase of the physical quantities at the sampling nodes. Based on the obtained spectrum sequence, the harmonic active power spectrum of the sampling nodes is calculated, and a resonance judgment threshold is set. When the ratio of the value in the harmonic active power spectrum to the fundamental active power exceeds the threshold, a resonance judgment is made. The system identifies cable resonance and pinpoints the source of the resonance disturbance based on the harmonic active power spectrum. It then determines whether the source disturbance device can modify its switching frequency. If it can, the system calculates the optimal switching frequency based on the power cable's distribution parameters and adjusts the switching frequency of the source disturbance device to the optimal frequency to avoid cable resonance. If the source disturbance device cannot modify its switching frequency, the system calculates the optimal cable length based on the power cable's distribution parameters and adjusts the cable length to the optimal length by online switching of the additional cable feeder length or switching of the backup feeder line to avoid cable resonance.

[0069] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0070] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0071] (1) Cable resonance phenomenon For converter connection cable feeder systems, please refer to Figure 1 Based on the cable's distributed parameters, the line impedance of the cable at the sampling node can be calculated as follows:

[0072] in, and These are all characteristic parameters of the cable. h This refers to the cable length. Simultaneously, the inductive reactance at the converter port is considered... L The grid port can be regarded as a harmonic current short-circuit port, and its harmonic voltage amplitude is 0.

[0073] Therefore, when there is an amplitude at the converter port... U , frequency is f r During disturbances, the harmonic voltage on the left side of the cable U 1. Harmonic current I 1. Right-side harmonic current I 2 are respectively: (1) (2) (3) When the harmonic disturbance frequency is fixed, changing the cable length h will reveal a periodic resonant amplification phenomenon in the harmonic current amplitude on the right side.

[0074] It is worth noting that harmonic current amplification does not occur at the left port of the cable, but the harmonic voltage disturbance of the converter is the power source and drive source of harmonic amplification.

[0075] Based on this, the location w (the location of the left resonant source) in a cable of length h is given. w The value is 0, and the position of the far end of the right resonance is... w Count as h Harmonic voltage U w Harmonic current I w Harmonic active power P w Harmonic reactive power Q w The expression: (4) (5) (6) (7) Plot the above four expressions as a function of the cable position w, as follows: Figure 2 As shown in the figure, the harmonic current, harmonic voltage, and harmonic reactive power all exhibit periodic fluctuations with changes in position within the cable, and none of these parameters at the sampling nodes provide effective information for resonance identification. However, due to the harmonic current amplification phenomenon along the entire cable, the harmonic active power consumed in the cable increases, and since this harmonic active power necessarily originates from harmonic sources, the occurrence of resonance can be identified by the harmonic active power values ​​at the sampling nodes.

[0076] (2) Calculation of optimal switching frequency and optimal cable length: Observing equation (3), we can see that when When resonance occurs, the system will exhibit resonance. Therefore, when resonance occurs, simply adjust the cable length. ,make Values ​​that are multiples of an even number At this point, the cable length corresponds to the resonant frequency. Based on this, you only need to adjust the cable length to .

[0077] Similarly, simply adjust the converter switching frequency to... This can avoid cable resonance. The relationship between the cable resonance phenomenon (harmonic active power at the converter-cable connection port) described above and the disturbance frequency and cable length are as follows: Figure 3 and Figure 4 As shown.

[0078] Please see Figure 2 The simulation data shows the spatial distribution of physical quantities such as harmonic active power and reactive power when resonance occurs. Simulation data shows that at the resonance point (such as a specific value of cable length), the harmonic active power increases significantly (e.g., from the normal value of 5W to 50W), while the harmonic reactive power and current fluctuate greatly. However, the harmonic active power only shows a stable peak value at the resonance point, which verifies its effectiveness as a resonance identification indicator.

[0079] Please see Figure 3 This study demonstrates the relationship between the ultra-high harmonic active power at the cable sampling node and the cable length. In the simulation, when the cable length increases from 100 meters to 200 meters, the harmonic active power peaks near the 150-meter mark (e.g., a sudden increase from 10W to 100W). By adjusting the length to 155 meters, the power drops to 15W, successfully avoiding resonance and demonstrating the feasibility of length adjustment.

[0080] Please see Figure 4This study demonstrates the relationship between harmonic active power and disturbance frequency. Experimental data shows that when the disturbance frequency increases from 4kHz to 6kHz, the harmonic active power reaches its peak at 5kHz (e.g., from 20W to 120W). By adjusting the converter switching frequency from 5kHz to 5.5kHz, the power is reduced to 25W, thus avoiding resonance.

[0081] Specific application example: In a city power distribution network, the method of this invention was applied to identify a resonant frequency of 5.2kHz. By adjusting the converter switching frequency to 5.8kHz, the harmonic active power was reduced from 150W to 30W, and the cable temperature dropped by 15℃, effectively preventing overload accidents.

[0082] In summary, this invention provides an active cable resonance avoidance method and system. Based on distorted power theory, it utilizes Fourier decomposition to calculate harmonic active power, achieving online identification of cable resonance. Compared to traditional methods, this invention does not rely on harmonic current, solving the problem of difficult observation of harmonic current at the resonant source port. By calculating the optimal switching frequency and optimal cable length, it provides active avoidance measures, effectively preventing local overvoltage and overcurrent caused by resonance and improving the stability of power grid operation. This method is applicable to high cable coverage systems in new energy and urbanization construction, capable of handling broadband and time-varying resonance phenomena, reducing equipment damage and power outage risks. Experiments and simulations show that this invention can accurately identify the resonant frequency and successfully avoid resonance by adjusting parameters, significantly reducing harmonic active power, proving its effectiveness and practicality.

[0083] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0084] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0085] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0086] In the embodiments provided by this invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0087] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0088] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0089] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random-access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0090] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus, and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0091] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0092] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0093] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for actively avoiding cable resonance, characterized in that, Includes the following steps: S1. Collect the port physical quantities of the converter connection cable feeder system, including three-phase voltage and three-phase current. Determine the sampling frequency according to the principle of twice the upper limit of the analysis frequency band, and determine the sampling duration according to the reciprocal of the accuracy of the resonance analysis frequency to obtain the physical quantity sampling results. S2. Based on the physical quantity sequence obtained in step S1, and combined with the sampling frequency and sampling duration, perform Fourier calculation to obtain the spectrum sequence of the physical quantity amplitude and phase of the sampling node. S3. Based on the spectrum sequence obtained in step S2, calculate the harmonic active power spectrum of the sampling node, set a resonance determination threshold, and determine that cable resonance has occurred when the ratio of the value in the harmonic active power spectrum to the fundamental active power exceeds the threshold. Then, based on the harmonic active power spectrum, pinpoint the source of the cable resonance disturbance device. The harmonic active power spectrum is calculated as follows: in, This is the three-phase voltage spectrum. For the three-phase voltage phase, The three-phase current spectrum, The phase of the three-phase current; Set resonance determination threshold k %, when the value of the harmonic active power spectrum at a certain node With fundamental active power The ratio exceeds k When the value reaches %, it is determined that cable resonance has occurred at that point, based on the harmonic active power spectrum exceeding %. k % of the resonant frequency f r The switching frequency of each power electronic device connected to the sampling node and its integer multiples are numerically matched to lock the source disturbance device of cable resonance; S4. Determine whether the source disturbance device can modify the switching frequency. If it can, calculate the optimal switching frequency based on the distribution parameters of the power cable, and adjust the switching frequency of the source disturbance device to the optimal switching frequency to avoid cable resonance. S5. If the source disturbance device cannot modify the switching frequency, the optimal cable length is calculated based on the distribution parameters of the power cable, and the cable length is adjusted to the optimal cable length by online switching of the additional length of the cable feeder or switching of the backup feeder line to avoid cable resonance.

2. The active cable resonance avoidance method according to claim 1, characterized in that, In step S2, the Fourier calculation includes calculating the three-phase voltage spectrum and phase, and the three-phase current spectrum and phase.

3. The active cable resonance avoidance method according to claim 1, characterized in that, In step S3, the resonance determination threshold is set to k %, k This is the preset percentage.

4. The active cable resonance avoidance method according to claim 1, characterized in that, In step S4, calculating the optimal switching frequency includes: Obtain the distributed parameters of the cable, including distributed capacitance, distributed resistance, and distributed inductance per meter; Calculate the characteristic parameters of the cable; Calculate the unit value of the resonant frequency shift based on the cable length and resonant frequency; Adjust the switching frequency so that the switching frequency corresponding to the resonant frequency or an integer multiple thereof is adjusted to the optimal switching frequency.

5. The active cable resonance avoidance method according to claim 4, characterized in that, The optimal switching frequency is: ,in, The resonant frequency, The total length of the cable in the resonance participation and propagation path, For distributed inductance, This is the distributed capacitance.

6. The active cable resonance avoidance method according to claim 1, characterized in that, In step S5, calculating the optimal cable length includes: Obtain the cable's distributed parameters; calculate the optimal cable length change based on the resonant frequency and cable characteristic parameters; the adjusted optimal cable length is the current cable length plus or minus the optimal cable length change.

7. The active cable resonance avoidance method according to claim 6, characterized in that, The optimal cable length change is ,in, The resonant frequency, The total length of the cable in the resonance participation and propagation path, For distributed inductance, This is the distributed capacitance.

8. A cable resonance active avoidance system, characterized in that, include: The acquisition module collects the port physical quantities of the converter connection cable feeder system, including three-phase voltage and three-phase current. The sampling frequency is determined according to the principle of twice the upper limit of the analysis frequency band, and the sampling duration is determined according to the reciprocal of the accuracy of the resonance analysis frequency to obtain the physical quantity sampling results. The calculation module performs Fourier calculations based on the physical quantity sequence sampled in the acquisition module, combined with the sampling frequency and sampling duration, to obtain the spectrum sequence of the physical quantity amplitude and phase of the sampling node. The determination module calculates the harmonic active power spectrum of the sampling node based on the spectrum sequence obtained from the calculation module, sets a resonance determination threshold, and determines that cable resonance has occurred when the ratio of the value in the harmonic active power spectrum to the fundamental active power exceeds the threshold. The module then identifies the source of the cable resonance disturbance device based on the harmonic active power spectrum. The harmonic active power spectrum is calculated as follows: in, This is the three-phase voltage spectrum. For the three-phase voltage phase, The three-phase current spectrum, The phase of the three-phase current; Set resonance determination threshold k %, when the value of the harmonic active power spectrum at a certain node With fundamental active power The ratio exceeds k When the value reaches %, it is determined that cable resonance has occurred at that point, based on the harmonic active power spectrum exceeding %. k % of the resonant frequency f r The switching frequency of each power electronic device connected to the sampling node and its integer multiples are numerically matched to lock the source disturbance device of cable resonance; The adjustment module determines whether the source disturbance device can modify the switching frequency. If it can, it calculates the optimal switching frequency based on the distribution parameters of the power cable and adjusts the switching frequency of the source disturbance device to the optimal switching frequency to avoid cable resonance. If the source disturbance device cannot modify the switching frequency, the output module calculates the optimal cable length based on the distribution parameters of the power cable, and adjusts the cable length to the optimal cable length by online switching of the additional length of the cable feeder or switching of the backup feeder line to avoid cable resonance.

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