Cable resonance active avoidance method and system

Abstract

The invention discloses a cable resonance active avoidance method and system, and belongs to the technical field of harmonic suppression. The method comprises the following steps: acquiring three-phase voltage and current of a connection port of a converter and a cable feeder, determining a sampling frequency according to a principle that an upper limit of an analysis frequency band is doubled, and determining a sampling duration according to a reciprocal of resonance analysis frequency precision; fourier calculation is carried out on the sampling data to obtain a frequency spectrum and a phase sequence; calculating a harmonic wave active power frequency spectrum, and when the ratio of the harmonic wave active power frequency spectrum to the fundamental wave active power exceeds a threshold value k%, determining resonance and locking source disturbance equipment; if the equipment can adjust the switching frequency, calculating and adjusting the optimal switching frequency according to cable distribution parameters; if not, the optimal cable length is calculated, and resonance avoidance is realized through additional length switching or standby line switching. The method solves the problem that a traditional method is difficult to identify online and actively avoid resonance, improves the operation stability of a power grid, and is suitable for a high-cabling-rate and high-power-electronic-proportion system.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of harmonic suppression, and particularly relates to a cable resonance active avoidance method and system. BACKGROUND

[0002] With the development of new energy industry and the promotion of urbanization construction, different types and different switching frequency converters emit rich super-high harmonic disturbances to the power grid, and the disturbances easily excite the harmonic amplification and even resonance of cable feeder in urban distribution network, introduce the local overvoltage and overcurrent risk of power cable, and endanger the stable operation of urban power grid. However, due to the large number of disturbance frequencies of power electronic equipment, the length and time-varying nature of the cable are strong, the resonance phenomenon in the cable feeder has the characteristics of wide frequency, time-varying and strong uncertainty, and it is difficult to identify and avoid.

[0003] In the existing cable resonance related research, the power cable is equivalent to a lumped parameter or a distributed parameter model, and the principle analysis and suppression guidance of the harmonic amplification rate of the long cable at different frequency bands are used. However, the related method uses the amplification of the harmonic current as the basis for determining the resonance phenomenon, and the harmonic current cannot be observed at the resonance source port, which limits the online application of this type of resonance suppression method in the actual system, and leads to the problem of only being suitable for post-event judgment and post-event remediation of related suppression schemes.

[0004] Therefore, in order to realize the effective identification and active avoidance of cable resonance in a system with a high cable rate and a high power electronic proportion, the application is based on the distortion power theory, uses Fourier decomposition to realize the calculation of high-frequency harmonic active power, and realizes the identification of cable resonance based on the numerical characteristics of the harmonic active power. And on this basis, an active avoidance method of cable resonance based on switching frequency change and cable length adjustment is designed, which realizes the online active avoidance of cable resonance. SUMMARY

[0005] The technical problem to be solved by the application is to provide a cable resonance active avoidance method and system based on the distortion power principle, which realizes the identification of resonance through harmonic active power, and configures the optimal switching frequency and optimal cable length based on harmonic active power by combining the cable distributed parameter model, to solve the technical problem that the traditional cable harmonic amplification analysis method cannot meet the resonance identification and online avoidance defects.

[0006] The application adopts the following technical scheme: A cable resonance active avoidance method, comprising the following steps: S1, collect the port physical quantity of the converter connection cable feeder system, including three-phase voltage and three-phase current, determine the sampling frequency according to the two times of the upper limit of the analysis frequency band, determine the sampling time length according to the reciprocal of the resonance analysis frequency accuracy, and obtain the physical quantity sampling result; S2, according to the physical quantity sequence obtained by sampling in step S1, combined with the sampling frequency and the sampling time length, Fourier calculation is carried out to obtain the frequency spectrum sequence of the physical quantity amplitude and phase of the sampling node; S3, according to the frequency spectrum sequence obtained in step S2, the harmonic active power spectrum of the sampling node is calculated, the resonance judgment threshold is set, when the value in the harmonic active power spectrum exceeds the threshold value compared with the fundamental active power, it is judged that the cable resonance occurs, and the source disturbance equipment of the cable resonance is locked according to the harmonic active power spectrum; S4, judge whether the source disturbance equipment can modify the switching frequency, if it can modify, calculate the optimal switching frequency according to the distribution parameters of the power cable, and adjust the switching frequency of the source disturbance equipment to the optimal switching frequency to avoid the cable resonance; S5, if the source disturbance equipment cannot modify the switching frequency, calculate the optimal cable length according to the distribution parameters of the power cable, and adjust the cable length to the optimal cable length by online switching of the cable feeder additional length or switching of the standby feeder line to avoid the cable resonance.

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

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

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

[0010] Wherein, is the three-phase voltage spectrum, is the three-phase voltage phase, is the three-phase current spectrum, is the three-phase current phase.

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

[0012] Preferably, in step S4, calculating the optimal switching frequency includes: Obtain the distribution parameters of the cable, including the distribution capacitance, distribution resistance and distribution inductance per meter; calculating characteristic parameters of the cable; calculating a resonant frequency shift unit value according to the cable length and the resonant frequency; adjusting the switching frequency to the optimal switching frequency corresponding to the resonant frequency or an integer multiple of the optimal switching frequency.

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

[0014] Preferably, in step S5, calculating the optimal cable length comprises: obtaining the distributed parameters of the cable; calculating the optimal cable length according to the resonant frequency and the characteristic parameters of the cable; and the adjusted optimal cable length is the current cable length plus or minus the optimal cable length.

[0015] Preferably, the optimal cable length is wherein, is the resonant frequency, is the total length of the cable in the resonant participation and propagation path, is the distributed inductance, is the distributed capacitance.

[0016] In a second aspect, an embodiment of the present application provides a cable resonant active avoidance system, comprising: a collection module, which collects port physical quantities of a converter connection cable feeder system, including three-phase voltage and three-phase current, determines a sampling frequency according to a two-fold principle of an upper limit of an analysis frequency band, determines a sampling time length according to the inverse of the resonant analysis frequency accuracy, and obtains physical quantity sampling results; a calculation module, which performs Fourier calculation on the physical quantity sequence obtained by sampling in the collection module, in combination with the sampling frequency and the sampling time length, and obtains a frequency spectrum sequence of physical quantity amplitude and phase of a sampling node; a determination module, which calculates a harmonic active power spectrum of the sampling node according to the frequency spectrum sequence obtained by the calculation module, sets a resonant determination threshold, determines that cable resonance occurs when the ratio of the value in the harmonic active power spectrum to the fundamental active power exceeds the threshold, and locks the source disturbance device of the cable resonance according to the harmonic active power spectrum; an adjustment module, which determines whether the source disturbance device can modify the switching frequency, calculates an optimal switching frequency according to the distributed parameters of the power cable if the source disturbance device can modify the switching frequency, and adjusts the switching frequency of the source disturbance device to the optimal switching frequency to avoid cable resonance; An output module, if the source disturbance device cannot modify the switching frequency, calculates an optimal cable length according to the distributed 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 standby feeder line to evade the cable resonance.

[0017] In a third aspect, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps of the cable resonance active evasion method when executing the computer program.

[0018] In a fourth aspect, an embodiment of the present application provides a computer readable storage medium including a computer program, and the computer program implements the steps of the cable resonance active evasion method when executed by a processor.

[0019] In a fifth aspect, a chip includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps of the cable resonance active evasion method when executing the computer program.

[0020] In a sixth aspect, an embodiment of the present application provides an electronic device including a computer program, and the computer program implements the steps of the cable resonance active evasion method when executed by the electronic device.

[0021] Compared with the prior art, the present application has at least the following beneficial effects: A cable resonance active evasion method, which identifies resonance based on harmonic active power instead of traditional harmonic current, solves the problem of difficulty in online acquisition of harmonic current; by actively adjusting the switching frequency or the cable length, online evasion of resonance is achieved, avoiding the limitations of after-the-fact remedies; the method is applicable to systems with high cable ratio and high power electronics ratio, improving the stability and reliability of the power grid and reducing the risk of local overvoltage and overcurrent.

[0022] Further, the sampling frequency is based on the principle of twice the upper limit of the analysis frequency band, ensuring that the sampled data has no frequency aliasing and improving the accuracy of the data; the sampling duration is based on the inverse of the resonance analysis frequency accuracy, ensuring the spectral resolution and providing a reliable foundation for subsequent Fourier calculation, thereby improving the accuracy and reliability of resonance identification.

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

[0024] Further, the calculation method of harmonic active power is determined, which combines the amplitude and phase difference of voltage and current, and ensures the scientificity and repeatability of calculation; the calculation method is based on distortion power theory, can effectively capture the energy change at resonance, and provides quantitative basis for resonance determination.

[0025] Further, the resonance determination standard is provided by presetting a percentage threshold (such as k%), which avoids subjective misjudgment; the threshold is based on the ratio of harmonic active power to fundamental active power, reflects the severity of resonance, and makes the determination process more objective and reliable.

[0026] Further, the characteristic parameters are calculated based on the cable distribution parameters (such as distribution capacitance, resistance and inductance), which ensures the scientificity of frequency adjustment; the optimal switching frequency is calculated by the unit value of resonance frequency shift, so that the adjusted frequency can effectively avoid the resonance point, and the resonance can be accurately avoided.

[0027] Further, the magnitude of frequency adjustment is determined, which is convenient for practical application and automation; by adjusting the switching frequency to the optimal value, resonance can be quickly avoided, the calculation complexity is reduced, and the system response speed is improved.

[0028] Further, the optimal change length is calculated based on the cable distribution parameters and resonance frequency, which provides another effective resonance avoidance method; the cable length is adjusted by online switching or switching standby line, which enhances the flexibility and adaptability of the system.

[0029] Further, the specific value of length adjustment is provided, which ensures the accuracy of the avoidance measure; the adjusted cable length can destroy the resonance condition, effectively prevent harmonic amplification, and improve the safety of the power grid.

[0030] It can be understood that the beneficial effects of the above-mentioned second aspect to sixth aspect can be referred to the related description in the first aspect, which will not be repeated here.

[0031] In summary, the present application identifies resonance through harmonic active power, adjusts the switching frequency and cable length, realizes online active avoidance of cable resonance, and solves the defects of traditional methods that rely on harmonic current and cannot be applied online. The method is scientific and the system is reliable, which improves the stability and safety of the power grid, and is suitable for high power electronic proportion system.

[0032] The technical solutions of the present application will be further described in detail below with the help of drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The topology diagram of the converter connected cable feeder system; Figure 2The spatial distribution of physical quantities such as harmonic active power, harmonic reactive power and the like when resonance occurs; Figure 3 The relationship between the ultra-high harmonic active power at the cable sampling node and the cable length; Figure 4 The relationship between the ultra-high harmonic active power at the cable sampling node and the disturbance frequency; Figure 5 A flowchart of the method of the present application; Figure 6 A schematic diagram of a computer device provided by an embodiment of the present application; Figure 7 A block diagram of a chip provided by an embodiment of the present application.

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

[0035] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0036] In the description of the present application, it should be understood that the terms "include" and "contain" indicate the existence of described features, whole, steps, operations, elements and / or components, but do not exclude the existence or addition of one or more other features, whole, steps, operations, elements, components and / or sets thereof.

[0037] It should also be understood that the terms used in the present application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present application specification and the appended claims, unless otherwise clearly indicated by the context, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0038] It should be further understood that the term "and / or" as used herein refers to a combination of one or more of the associated listed items, and all possible combinations, and includes these combinations, for example, A and / or B can mean: A alone, A and B together, and B alone. In addition, the character " / " in the present application generally represents an "or" relationship between the front and rear associated objects.

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

[0040] Depending on the context, the word "if" as used herein can be interpreted to mean "when" or "while" or "in response to determining" or "in response to detecting". Similarly, the phrase "if it is determined" or "if (a stated condition or event) is detected" can be interpreted to mean "when it is determined" or "in response to determining" or "when (a stated condition or event) is detected" or "in response to detecting (a stated condition or event)".

[0041] Various structural diagrams according to the disclosed embodiments of the present application are shown in the accompanying drawings. These drawings are not drawn to scale, in which certain details are exaggerated for the purpose of clarity and certain details can be omitted. The shapes of various regions, layers and their relative sizes and positional relationships shown in the drawings are only exemplary, and in actuality, they can deviate due to manufacturing tolerances or technical limitations, and a person skilled in the art can additionally design regions / layers with different shapes, sizes and relative positions according to actual needs.

[0042] The present application provides a cable resonance active avoidance method, which acquires the port physical quantity of the converter connected cable feeder system, the physical quantity can be obtained by the converter in real time, and the online identification of the cable resonance is carried out. At the same time, the online identification result can be used to guide the online adjustment of the switch frequency of the converter, the online switching of the cable feeder length and the switching of the standby line; has the best parameter guidance function of the cable resonance multi-type avoidance scheme. The best adjustment frequency point of the switch frequency and the best change length of the cable feeder length can be given.

[0043] Please refer to Figure 5 The cable resonance active avoidance method of the present application comprises the following steps: S1, determining the sampling frequency as , determining the sampling node, that isFigure 1 The connection port of the converter device in the system and the cable feeder; the sampling physical quantity is three-phase voltage and three-phase current, and the sampling time length is determined according to the reciprocal of the resonance analysis frequency accuracy ; the physical quantity sampling result is obtained; The physical quantity sampling result includes: Three-phase voltage sequence , three-phase current sequence .

[0044] S2, according to the physical quantity sequence obtained by sampling in step S1, combined with the sampling frequency , the sampling time length , Fourier calculation is carried out to obtain the frequency spectrum sequence of the amplitude and phase of the physical quantity of the sampling node; The frequency spectrum sequence of the amplitude and phase of the physical quantity of the sampling node is specifically: Three-phase voltage spectrum and phase , three-phase current spectrum and phase .

[0045] S3, according to the frequency spectrum and phase of the three-phase voltage and current of the sampling node calculated in step S2, the harmonic active power spectrum of the sampling node is calculated; For the three-phase voltage spectrum and phase of the node, the three-phase current spectrum and phase , the formula for calculating the harmonic active power spectrum is:

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

[0047] Set the resonance judgment threshold k %, when the ratio of the value to the fundamental active power in the harmonic active power spectrum of a node exceeds k %, it is judged that the cable resonance phenomenon occurs at the point. At the same time, according to the resonance frequency k f r , which exceeds % in the harmonic active power spectrum, 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 the cable resonance.

[0048] ​According to the cable model description or physical parameter calculation, the distributed parameters of the cable are obtained: the distributed capacitance per meter c , the distributed resistance r , the distributed inductance l ; the characteristic parameters are calculated using the cable parameters , , wherein .

[0049] The total length of the cable in the resonance participation and propagation path is obtained h , and the resonance frequency frequency shift unit calculation value is: ; By adjusting the switching frequency of the source disturbance device, the switching frequency corresponding to the resonance frequency or an integer multiple thereof is adjusted to , so as to realize the avoidance of cable resonance.

[0050] S5, if the scheme of adjusting the switching frequency of the source disturbance device in step S4 is not feasible, the optimal cable length is calculated according to the distributed parameters of the power cable, and the adjustment of the current cable length to the optimal cable length is realized by the online switching of the additional length of the cable feeder or the switching to the standby feeder line. The optimal cable length is calculated as: . The adjusted optimal cable length should be , and the avoidance of cable resonance is realized by adjusting the length of the power cable to this value.

[0051] In another embodiment of the present application, a cable resonance active avoidance system is provided, which can be used to realize the above-mentioned cable resonance active avoidance method. Specifically, the cable resonance active avoidance system comprises a collection module, a calculation module, a determination module, an adjustment module and an output module.

[0052] The collection module collects the port physical quantities of the converter connection cable feeder system, including three-phase voltage and three-phase current, determines the sampling frequency according to the two times upper limit of the analysis frequency band, determines the sampling time length according to the inverse of the resonance analysis frequency accuracy, and obtains the physical quantity sampling result; The calculation module performs Fourier calculation on the physical quantity sequence obtained by the collection module in combination with the sampling frequency and the sampling time length, to obtain the frequency 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 according to the frequency spectrum sequence obtained by the calculation module, sets a resonance determination threshold, determines that cable resonance occurs when the ratio of the value in the harmonic active power spectrum to the fundamental active power exceeds the threshold, and locks the source disturbance device of the cable resonance according to the harmonic active power spectrum; An adjusting module judges whether the source disturbance device can modify the switching frequency, and if yes, calculates the optimal switching frequency according to the distributed parameters of the power cable, and adjusts the switching frequency of the source disturbance device to the optimal switching frequency to avoid cable resonance. An output module calculates the optimal cable length according to the distributed parameters of the power cable if the source disturbance device cannot modify the switching frequency, 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 standby feeder line to avoid cable resonance.

[0053] The application provides a terminal device, which comprises a processor and a memory. The memory is used for storing a computer program, and the computer program comprises program instructions. The processor is used for executing the program instructions stored in the computer storage medium. The processor can be a central processing unit (CPU), and can also be 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 gates or transistor logic devices, discrete hardware components and the like. The processor is a computing core and a control core of the terminal, and is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions to implement a corresponding method flow or a corresponding function. The processor in the embodiments of the application can be used for the operation of the cable resonance active avoidance method, which comprises the following steps: The port physical quantity of the converter connection cable feeder system is collected, including three-phase voltage and three-phase current, the sampling frequency is determined according to the principle of twice upper limit of the analysis frequency band, the sampling time length is determined according to the reciprocal of the resonance analysis frequency accuracy, and the physical quantity sampling result is obtained; according to the physical quantity sequence obtained by sampling, combined with the sampling frequency and the sampling time length, Fourier calculation is carried out to obtain the frequency spectrum sequence of the physical quantity amplitude and phase of the sampling node; according to the obtained frequency spectrum sequence, the harmonic active power spectrum of the sampling node is calculated, the 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, it is judged that the cable resonance occurs, and the source disturbance equipment of the cable resonance is locked according to the harmonic active power spectrum; it is judged whether the source disturbance equipment can modify the switching frequency, if it can modify, the optimal switching frequency is calculated according to the distribution parameters of the power cable, and the switching frequency of the source disturbance equipment is adjusted to the optimal switching frequency to avoid the cable resonance; if the source disturbance equipment cannot modify the switching frequency, the optimal cable length is calculated according to 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 standby feeder line to avoid the cable resonance.

[0054] Please refer to Figure 6 , the terminal device is a computer device, the computer device 60 of the embodiment includes: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61, which realizes the cable resonance active avoidance method in the embodiment when executed by the processor 61, to avoid repetition, which will not be described here. Alternatively, the computer program 63 is executed by the processor 61 to realize the functions of each model / unit in the cable resonance active avoidance system of the embodiment, to avoid repetition, which will not be described here.

[0055] The computer device 60 can be a desktop computer, a notebook computer, a palm computer, and a cloud server, etc. The computer device 60 can include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art can understand that Figure 6 is only an example of the computer device 60 and does not constitute a limitation on the computer device 60, and can include more or fewer components than shown, or combine certain components, or different components, for example, the computer device can also include an input / output device, a network access device, a bus, etc.

[0056] The processor 61 can be a central processing unit (CPU), and can also be 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 gates or transistor logic, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

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

[0058] Further, the memory 62 can include both an internal storage unit and an external storage device of the computer device 60. 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 refer to Figure 7 , the terminal device is an electronic device 600, and the electronic device 600 is in the form of a general-purpose computing device. The components of the electronic device can 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 the storage unit 620 and the processing unit 610), a display unit 640, etc.

[0060] Among them, the storage unit stores program codes, and the program codes can be executed by the processing unit 610, so that the processing unit 610 executes the steps of various exemplary embodiments according to the present application described in the method part of the present specification. For example, the processing unit 610 can execute the steps as shown in Figure 5 .

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

[0062] Storage 620 can also include program / utility 6204 having a set of programs / modules 6205, e.g., operating systems, one or more application programs, other programs, and programmatic data, each of which can implement some or all of the features of the network environment as various combinations of the examples above.

[0063] Bus 630 can represent one or more of several types of bus structures, including a storage bus or bus controller, peripheral bus, graphics bus, processor or local bus using any of a variety of bus architectures.

[0064] Electronic device 600 can also communicate with one or more external devices 700 such as a keyboard or pointing device, using one or more communication interfaces 650. Communication interfaces 650 can include a network interface 660, e.g., an Ethernet card to enable communication with a network. Communication interfaces 650 can also include a wireless interface, e.g., an 802.11 card, a Bluetooth card, etc. Communication interfaces 650 can further include a modem, a cable modem, and / or one or more universal serial bus interfaces. It should be appreciated that not all of these components are essential, and that implementations of electronic device 600 can include only those subsystems appropriate to the functionality of the implementation. For example, electronic device 600 can be a network server, in which case it can not include input devices such as a keyboard or pointing device, and / or output devices such as a display. Electronic device 600 can also communicate with one or more devices enabling a user to interact with electronic device 600, and / or one or more devices enabling electronic device 600 to communicate with one or more other computing devices. Such communication can be via input / output interfaces 650. Furthermore, electronic device 600 can communicate with one or more networks, such as a local area network, a wide area network, and / or a public network such as the Internet, via network adapter 660. Network adapter 660 can communicate with the other modules of electronic device 600 via bus 630. It should be appreciated that 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, etc.

[0065] Example 4 The present application further provides a storage medium, specifically a computer readable storage medium, which is a memory device in the terminal device, and is used to store programs and data. It can be understood that the computer readable storage medium herein can include the built-in storage medium in the terminal device, and of course can include the expansion storage medium supported by the terminal device, and can be any tangible medium containing or storing programs, which can be used by or in combination with an instruction execution system, device or apparatus. The computer readable storage medium provides a storage space, which stores the operating system of the terminal. Moreover, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and the instructions can be one or more computer programs (including program codes). It should be noted that more specific examples of the computer readable storage medium include an electrical connection having one or more wires, a portable disk, a hard disk, a random access memory, a read-only memory, an erasable programmable read-only memory, an optical fiber, a portable compact disk read-only memory, an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0066] The computer readable storage medium further includes a data signal carried in baseband or propagated as a carrier wave, in which readable program codes are borne. Such a propagated data signal can take various forms, including but not limited to electro-magnetic signal, optical signal or any suitable combination of the above. The readable storage medium can also be any readable medium other than the readable storage medium, which can send, propagate or transmit programs for use by or in combination with an instruction execution system, device or apparatus. The program codes contained in the readable storage medium can be transmitted by any suitable medium, including but not limited to wireless, wired, optical cable, radio frequency, etc., or any suitable combination of the above.

[0067] The program codes for executing the operation of the present application can be written in any combination of one or more programming languages, including object-oriented programming languages such as Java, C++, etc., and conventional procedural programming languages such as "C" language or similar programming languages. The program codes can be executed entirely on the user computing device, partially on the user device, as an independent software package, partially on the user computing device and partially on the remote computing device, or entirely on the remote computing device or server. In the case involving remote computing device, the remote computing device can be connected to the user computing device through any kind of network, including local area network or wide area network, or can be connected to external computing device (for example, connected through the Internet by using an Internet service provider).

[0068] The one or more instructions in the computer readable storage medium can be loaded and executed by the processor to implement the corresponding steps of the cable resonance active avoidance method in the above embodiments; the one or more instructions in the computer readable storage medium are loaded and executed by the processor to implement the following steps: The port physical quantity of the converter connection cable feeder system is collected, 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, the sampling time length is determined according to the reciprocal of the resonance analysis frequency accuracy, and the physical quantity sampling result is obtained; the physical quantity sequence obtained by sampling is combined with the sampling frequency and the sampling time length, and Fourier calculation is performed to obtain the frequency spectrum sequence of the physical quantity amplitude and phase of the sampling node; the harmonic active power spectrum of the sampling node is calculated according to the obtained frequency spectrum sequence, 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, it is judged that cable resonance occurs, and the source disturbance device of the cable resonance is locked according to the harmonic active power spectrum; if the source disturbance device can modify the switching frequency, the optimal switching frequency is calculated according to the distribution parameters of the power cable, and the switching frequency of the source disturbance device is adjusted to the optimal switching frequency to avoid cable resonance; if the source disturbance device cannot modify the switching frequency, the optimal cable length is calculated according to the distribution parameters of the power cable, and the cable length is adjusted to the optimal cable length by online switching of the cable feeder additional length or switching of the standby feeder line to avoid cable resonance.

[0069] The database involved in each of the embodiments provided in the present application can include at least one of a relational database and a non-relational database. The non-relational database can include a distributed database based on a blockchain, and the like, without being limited thereto. The processor involved in each of the embodiments provided in the present application can be a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, and the like, without being limited thereto.

[0070] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by a person of ordinary skill in the art without creative labor based on the embodiments in the present application belong to the scope of protection of the present application.

[0071] (1) Cable resonance phenomenon For the converter connected cable feeder system, please refer to Figure 1 According to the distributed parameters of the cable, the line impedance of the cable at the sampling node can be calculated as:

[0072] where, and are the characteristic parameters of the cable, h is the cable length. At the same time, the inductance of the converter equipment port is regarded as L , and the grid port can be regarded as a harmonic current short-circuit port, and the harmonic voltage amplitude is 0.

[0073] Therefore, when the converter port exists a disturbance with an amplitude of U and a frequency of f r , the left side harmonic voltage U 1、harmonic current I 1、and the right side harmonic current I 2are respectively: (1) (2) (3) When the harmonic disturbance frequency is fixed, changing the cable length h, it can be seen that the right side harmonic current amplitude presents a periodic resonance amplification phenomenon.

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

[0075] On this basis, the expressions of the harmonic voltage w w , the harmonic current w w , the harmonic active power h w and the harmonic reactive power U w at the position w in the cable with a length of h (the left resonance source position I is counted as 0, and the right resonance far end position P is counted as Q ) are given: (4) (5) (6) (7) The above four expressions are plotted as a function of the cable position w, as shown inFigure 2 As can be seen from the figure, the harmonic current, harmonic voltage, and harmonic reactive power all present a periodic fluctuation state with the change of the position in the cable, and cannot provide effective information for the identification of resonance at the sampling nodes. Due to the harmonic current amplification phenomenon occurring in the whole cable, the harmonic active power consumed in the cable increases, and the harmonic active power must come from the harmonic source, so the occurrence of resonance can be identified through the harmonic active power value of the sampling node.

[0076] (2) Calculation of the optimal switching frequency and the optimal cable length: As can be seen from the observation formula (3), when , the system will have a resonance phenomenon. Therefore, when resonance occurs, only the cable length needs to be adjusted to make the value of an even multiple of . At this time, based on the resonance frequency corresponding to the cable length , only the cable length needs to be adjusted to .

[0077] Similarly, only the converter switching frequency needs to be adjusted to , and the cable resonance can be avoided. The above-described relationship between the cable resonance phenomenon (harmonic active power of the converter and cable connection port) and the disturbance frequency and the cable length is shown in Figure 3 and Figure 4 , respectively.

[0078] Please refer to Figure 2 , which shows the spatial distribution of physical quantities such as harmonic active power and reactive power when resonance occurs. The simulation data show that at the resonance point (such as a specific value of the cable length), the harmonic active power increases significantly (for example, from the normal value of 5W to 50W), while the harmonic reactive power and current fluctuate greatly, but only at the resonance point does the harmonic active power present a stable peak value, verifying its effectiveness as a resonance identification index.

[0079] Please refer to Figure 3 , which shows 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 appears a peak value near the length of 150 meters (for example, from 10W to 100W), and by adjusting the length to 155 meters, the power decreases to 15W, successfully avoiding resonance, embodying the feasibility of length adjustment.

[0080] Please refer to Figure 4, which shows the relationship between harmonic active power and disturbance frequency. Experimental data show that when the disturbance frequency increases from 4 kHz to 6 kHz, the harmonic active power reaches a peak at 5 kHz (for example, from 20 W to 120 W), and by adjusting the converter switching frequency from 5 kHz to 5.5 kHz, the power is reduced to 25 W, avoiding resonance.

[0081] Specific application example: In a certain urban power distribution network, the method of the application is applied to identify the resonance frequency of 5.2 kHz, and by adjusting the converter switching frequency to 5.8 kHz, the harmonic active power is reduced from 150 W to 30 W, and the cable temperature is reduced by 15 DEG C, effectively preventing overload accidents.

[0082] In summary, the cable resonance active avoidance method and system of the application, based on the distortion power theory, calculates the harmonic active power using Fourier decomposition, realizing online identification of cable resonance. Compared with traditional methods, the application does not rely on harmonic current, solving the problem of difficult observation of resonance source port harmonic current. By calculating the optimal switching frequency and optimal cable length, active avoidance measures are provided, effectively preventing local overvoltage and overcurrent caused by resonance, and improving the stability of power grid operation. The method is suitable for high-cable-rate systems in new energy and urbanization construction, and can cope with wideband and time-varying resonance phenomena, reducing equipment damage and power outage risk. Experiments and simulations show that the application can accurately identify the resonance frequency and successfully avoid resonance by adjusting parameters, and the harmonic active power is significantly reduced, proving its effectiveness and practicality.

[0083] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the above division of each functional unit and module is exemplified, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit. The above integrated unit can be realized in the form of hardware or software. In addition, the specific name of each functional unit and module is only for easy distinction, and does not limit the protection scope of the application. The specific working process of the unit and module in the above system can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0084] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described or recorded in a certain embodiment can be referred to the related description of other embodiments.

[0085] Those skilled in the art can understand that the units and algorithm steps of each example described in combination with the embodiments disclosed in the present application can be realized in electronic hardware or in combination of computer software and electronic hardware. Whether the functions are realized 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 realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0086] In the embodiments provided by the present application, it should be understood that the disclosed apparatus / terminal and method can be implemented in other ways. For example, the apparatus / terminal embodiments described above are merely schematic. The division of the modules or units is merely a logical function division, and there can be another division manner in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed coupling or direct coupling or communication connection between the units can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or in other forms.

[0087] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e. they can be located in one place, or can be distributed on a plurality of network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiments.

[0088] In addition, each functional unit in each embodiment of the present application can be integrated into a processing unit, or each unit can exist physically independently, or two or more units can be integrated into one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0089] The integrated module / unit, if realized in the form of a software function unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on such understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of each method embodiment when executed by a processor. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or some intermediate forms, etc. The computer-readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the computer-readable medium can include or exclude contents according to the requirements of legislation and patent practice in the jurisdiction, for example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0090] The present application is described with reference to flowcharts and / or block diagrams of methods, devices, and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device that implements the flowcharts and / or block diagrams. Figure 1 The flow or multiple flows and / or blocks Figure 1 The device that implements the functions specified in one or more flows or blocks.

[0091] These computer program instructions can also be stored in a computer-readable memory that can guide the computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including instruction devices that implement the flowcharts and / or block diagrams. Figure 1 The flow or multiple flows and / or blocks Figure 1 The device that implements the functions specified in one or more flows or blocks.

[0092] These computer program instructions can also be loaded into a computer or other programmable data processing devices, so that a series of operational steps are performed on the computer or other programmable data processing devices to generate a computer implemented process, so that the instructions executed on the computer or other programmable data processing devices provide a process for implementing the flowchart Figure 1 one flow or a plurality of flows and / or the functions specified in the block Figure 1 one block or a plurality of blocks.

[0093] The above is only to illustrate the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

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 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.

2. The active cable resonance avoidance method according to claim 1, characterized in that, 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.

3. 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.

4. The active cable resonance avoidance method according to claim 1, characterized in that, In step S3, the harmonic active power spectrum is calculated as follows: 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.

5. 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.

6. 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.

7. The active cable resonance avoidance method according to claim 6, 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.

8. 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.

9. The active cable resonance avoidance method according to claim 8, 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.

10. 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 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.

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