Converter cluster multi-frequency harmonic disturbed coupling current high-precision analysis method and system

Abstract

The application discloses a kind of converter cluster multi-frequency harmonic disturbed coupling current high-precision analysis method and system, obtain network node equation;The small signal relationship of each power electronic equipment port voltage and current in system is calculated, the frequency coupling model of converter is obtained;Simultaneous network node equation and the frequency coupling model of converter, eliminate voltage, obtain the small signal equation containing converter frequency coupling model, grid and harmonic current disturbance;With only fundamental grid voltage as system initial state, solve initial steady-state quantity;The large disturbance of harmonic current is divided into multiple stages, and the disturbance is increased in stages, and the disturbance size of each stage meets the requirements of small signal calculation;Update the small signal equation set of system, superimpose the disturbance of next stage, until the amplitude of harmonic current disturbance and the set target are the same.The application principle is clear, the calculation precision is high, has wide applicability, can adapt to a variety of distribution network structure, has relatively practical engineering application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power quality and harmonic calculation, and particularly relates to a high-precision analysis method and system for disturbed coupling current of multi-frequency harmonics of a converter cluster. BACKGROUND

[0002] In recent years, with the development of renewable energy systems and the large-scale grid connection of power electronic devices, the device clusters composed of multiple power electronic devices (such as inverters, rectifiers, frequency converters, motor drives, etc.) work together, and the harmonics generated by them interact with each other and affect the power quality of the system. The different frequency harmonics generated by multiple devices in the cluster may superimpose together to form more complex harmonic pollution. Specifically, in the device cluster, the harmonic signals of multiple converters may superimpose in the same frequency band, resulting in more complex harmonic pollution. Therefore, simply relying on the independent harmonic model of each device is not enough to accurately describe the harmonic behavior of the entire cluster. At the same time, when the harmonic component of the external disturbance does not meet the characteristics of small disturbance, simply using the small signal equation cannot accurately describe the nonlinear characteristics of this harmonic "large disturbance". Finally, when the power electronic device cluster is connected to the distribution network, the impedance characteristics of the distribution network will not only affect the propagation path of the harmonics, but also may cause the amplification or attenuation of certain frequency band harmonics, thereby changing the overall harmonic characteristics of the device cluster.

[0003] The traditional method can directly solve the final harmonic current response of the system under the excitation of each harmonic grid voltage by solving the steady-state equation set of the system. Since the harmonic components of each state variable are directly solved, the size of each state variable harmonic component is an unknown number, and there may be multiplication of unknown quantities. The equation set to be solved is a nonlinear equation, which cannot be solved using linear methods, and its solution is difficult. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a high-precision analysis method and system for disturbed coupling current of multi-frequency harmonics of a converter cluster, which solves the technical problem of analyzing the harmonic emission characteristics of the converter cluster under large disturbance by using a small signal step-by-step method to calculate the harmonic emission characteristics of the converter under large disturbance.

[0005] The application adopts the following technical solutions:

[0006] A high-precision analysis method for disturbed coupling current of multi-frequency harmonics of a converter cluster, comprising the following steps:

[0007] S1, obtaining a network node equation;

[0008] S2, calculating the small signal relationship between the port voltage and current of each power electronic device in the system to obtain a frequency coupling model of the converter;

[0009] S3, eliminate the voltage by combining the network node equation and the frequency coupling model of the converter, to get the small signal equation containing the frequency coupling model of the converter, the network and the harmonic current disturbance;

[0010] S4, take only the fundamental grid voltage as the initial state of the system, and solve the initial steady-state quantity;

[0011] S5, divide the large disturbance of the harmonic current into multiple stages, and increase the disturbance in stages, and the disturbance size of each stage meets the requirements of small signal calculation;

[0012] S6, update the small signal equation set of the system, superimpose the disturbance of the next stage, until the amplitude of the harmonic current disturbance is the same as the set target.

[0013] Preferably, the network node equation is as follows:

[0014]

[0015] wherein, is the node fundamental impedance matrix, is the harmonic impedance matrix, is the node voltage, is the fundamental current of the node, is the harmonic disturbance current.

[0016] Preferably, the frequency coupling model of the converter adopts a frequency coupling model based on a harmonic transfer function, wherein is the frequency coupling phase; the frequency coupling model of the converter is specifically as follows:

[0017]

[0018] wherein, , , , denotes a coefficient matrix, is the output current of the converter, is the conjugate of , is the grid voltage, is the conjugate of .

[0019] Preferably, the small signal equation is:

[0020]

[0021] wherein, , is a harmonic matrix changed according to the harmonic impedance matrix, is the harmonic disturbance current, is a conjugate of is a converter output current of each node, is a conjugate of a conjugate of

[0022] Preferably, the large disturbance of the harmonic current is divided into multiple stages, specifically:

[0023] The step-by-step superposition of the harmonic current disturbance and the small-signal linearization in multiple stages ensure the accuracy and reasonableness of the calculation results of the small-signal equation in each stage.

[0024] Preferably, the small-signal equation set of the system is updated, and the disturbance of the next stage is superimposed until the amplitude of the harmonic current disturbance is the same as the set target, specifically:

[0025] The small-perturbation response of each state variable under the harmonic current disturbance in each stage is calculated by the small-signal equation;

[0026] The small-perturbation response of each state variable solved in the last stage is superimposed into the steady-state component as a new steady-state operating point, and the small-signal equation set of the system is updated;

[0027] The disturbance of the next stage is superimposed, and the process is repeated until the amplitude of the harmonic current disturbance is the same as the set target, ensuring the consistency of the total disturbance size.

[0028] In a second aspect, an embodiment of the present application provides a high-precision analysis system for multi-frequency harmonic disturbed coupling current of a converter cluster, comprising:

[0029] A node module acquires network node equations;

[0030] A calculation module calculates the small-signal relationship of the port voltage and current of each power electronic device in the system to obtain a frequency coupling model of the converter;

[0031] A simultaneous module simultaneously solves the network node equations and the frequency coupling model of the converter to eliminate the voltage and obtain a small-signal equation containing the frequency coupling model of the converter, the grid, and the harmonic current disturbance;

[0032] A division module takes only the fundamental grid voltage as the initial state of the system to solve the initial steady-state quantity, divides the large disturbance of the harmonic current into multiple stages, and increases the disturbance in stages, and the disturbance size of each stage meets the requirement of small-signal calculation;

[0033] An update module updates the small-signal equation set of the system, superimposes the disturbance of the next stage, and until the amplitude of the harmonic current disturbance is the same as the set target.

[0034] Preferably, the small-signal equation set of the system is updated, and the disturbance of the next stage is superimposed until the amplitude of the harmonic current disturbance is the same as the set target, specifically:

[0035] The small signal equation is calculated to obtain the small disturbance response of each state variable under the harmonic current disturbance of each stage;

[0036] The small disturbance response of each state variable solved in the last stage is superimposed on the steady-state component as a new steady-state working point, and the small signal equation set of the system is updated;

[0037] The disturbance of the next stage is superimposed, and the process is repeated until the amplitude of the harmonic current disturbance is the same as the set target, so that the total disturbance size is consistent.

[0038] 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 converter cluster multi-frequency harmonic disturbed coupling current high-precision analysis method when executing the computer program.

[0039] 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 converter cluster multi-frequency harmonic disturbed coupling current high-precision analysis method when executed by a processor.

[0040] 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 converter cluster multi-frequency harmonic disturbed coupling current high-precision analysis method when executing the computer program.

[0041] 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 converter cluster multi-frequency harmonic disturbed coupling current high-precision analysis method when executed by the electronic device.

[0042] Compared with the prior art, the present application has at least the following beneficial effects:

[0043] A converter cluster multi-frequency harmonic disturbed coupling current high-precision analysis method adopts a small signal step-by-step method, only needs to have an obtainable system initial steady-state working point (which can be regarded as an ideal working point of the device) containing only three-phase balanced fundamental grid voltage, then continuously updates the initial steady-state working point according to the step-by-step method until the finally applied grid voltage is the same as the actual situation; in this process, the calculation result of the last stage is superimposed on the steady-state working amount of the last stage to obtain the steady-state working amount of the next stage, so that the coefficients of the to-be-solved variables in the equation of each stage are known, and the calculation relationship between harmonics and fundamental waves and between harmonics can be considered at the same time.

[0044] Further, the converter model adopts a frequency coupling model based on a harmonic transfer function, which accurately describes the frequency coupling characteristics of the converter, specifically by introducing a conjugate relative converter feature in the model.

[0045] Further, the network harmonic impedance equation is a linear equation, and is also processed as a small signal to remove the fundamental component to obtain a small signal network harmonic impedance equation. By combining the coupling model of the converter and the small signal network harmonic impedance equation, the intermediate variable (node voltage) is eliminated, and finally the small signal equation of the converter cluster is obtained. The small signal equation of the converter cluster can be calculated in the small signal step-by-step manner, reducing the amount of calculation.

[0046] Further, the perturbation is added in stages and the coefficient matrix is updated to improve the accuracy of the calculation. The small signal equation can only be applied to the calculation of small perturbations. When the perturbation signal is too large, the calculation error is large. Therefore, the perturbation signal is added in stages to ensure the accuracy of the small signal calculation result of each stage, and the total perturbation size needs to be ensured. At the same time, the coefficient matrix is corrected using the calculation result of the previous stage to reduce the error caused by linearization calculation. Finally, the calculation result of the nonlinear equation is approached by linear calculation, avoiding solving the nonlinear equation, while ensuring the calculation accuracy. (In a conventional case, the response to a large perturbation can only be solved by directly solving the original nonlinear equation. This method has a large amount of calculation and is difficult to calculate.)

[0047] It can be understood that the beneficial effects of the above-mentioned second aspect to the sixth aspect can be referred to the related description in the first aspect, which will not be repeated here.

[0048] In summary, the principle of the application is clear, the calculation accuracy is high, and it has wide applicability, can adapt to various power distribution network structures, and has a relatively practical engineering application value.

[0049] The technical solutions of the application will be further described in detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 The method described in the application is verified in the scene;

[0051] Fig. 2 is a comparison result of the method and simulation of the application;

[0052] Figure 3 The schematic diagram of the computer device provided by an embodiment of the application is shown in the figure;

[0053] Figure 4 The block diagram of a chip provided by an embodiment of the application is shown in the figure;

[0054] Figure 5The flowchart is used for the present application. DETAILED DESCRIPTION

[0055] The technical solutions in the embodiments of the present application will be clearly and completely described 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 efforts belong to the scope of the present application.

[0056] In the description of the present application, it should be understood that the terms "comprising" and "including" indicate the presence of described features, integers, steps, operations, elements, and / or components, but do not exclude one or more other features, integers, steps, operations, elements, components, and / or sets thereof.

[0057] It should also be understood that the terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification and the appended claims of the present application, unless otherwise clearly indicated by the context, the singular forms "a", "an" and "the" are intended to include the plural forms as well.

[0058] It should be further understood that the term "and / or" used in the specification and the appended claims of the present application means any 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 represent three cases of 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.

[0059] It should be understood that although the terms first, second, third, etc. may be used in the embodiments of the present application to describe the preset ranges, etc., these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from each other. For example, the first preset range can also be referred to as the second preset range, and similarly, the second preset range can also be referred to as the first preset range, without departing from the scope of the embodiments of the present application.

[0060] Depending on the context, the word "if" as used herein can be interpreted as meaning "when" or "while" or "in response to determining" or "in response to detecting". Similarly, depending on the context, the phrase "if determined" or "if detecting (a stated condition or event)" can be interpreted as meaning "when determined" or "in response to determining" or "when detecting (a stated condition or event)" or "in response to detecting (a stated condition or event)".

[0061] Various structural diagrams according to the disclosed embodiments of the present application are shown in the drawings. These diagrams are not drawn to scale, in which certain details are exaggerated for clarity of presentation and may be omitted, for example. The shapes and relative sizes of the various regions, layers, and the relative positions of these in the drawings are merely examples and may deviate in practice due to manufacturing tolerances or technical limitations, and regions / layers with different shapes, sizes, and relative positions can be additionally designed according to actual needs by those skilled in the art.

[0062] The present application provides a high-precision analysis method for multi-frequency harmonic disturbed coupling current of converter cluster, which describes the interaction of harmonics in the device cluster by considering the interaction characteristics between converters for the converter cluster, considers the influence of the network impedance of the power distribution system on the harmonic characteristics of the device cluster, and calculates the harmonic emission characteristics of the power electronic device cluster under large disturbance by using a stepping idea; in order to achieve this goal, first, a small-signal equation containing a network model and a converter frequency coupling model is obtained, and on this basis, a small-signal stepping method is proposed, which uses multiple stages of small-signal linearization, and in each stage, the small-signal equation of the next stage is updated according to the calculation results of the last stage, and then the nonlinear process under large disturbance is calculated; finally, the harmonic emission characteristics of the power electronic device cluster after interactive coupling under large disturbance are calculated.

[0063] Please refer to Figure 5 The present application provides a high-precision analysis method for multi-frequency harmonic disturbed coupling current of converter cluster, which describes the interaction of harmonics in the device cluster by considering the interaction characteristics between converters for the converter cluster, considers the influence of the network impedance of the power distribution system on the harmonic characteristics of the device cluster, and calculates the harmonic emission characteristics of the power electronic device cluster under large disturbance by using a stepping idea; in order to achieve this goal, first, a small-signal equation containing a network model and a converter frequency coupling model is obtained, and on this basis, a small-signal stepping method is proposed, which uses multiple stages of small-signal linearization, and in each stage, the small-signal equation of the next stage is updated according to the calculation results of the last stage, and then the nonlinear process under large disturbance is calculated; finally, the harmonic emission characteristics of the power electronic device cluster after interactive coupling under large disturbance are calculated.

[0064] S1, obtain a network node equation;

[0065] The network node equation is as follows:

[0066]

[0067] wherein, is a node impedance matrix, is an inverse matrix of a node admittance matrix, is a node voltage, is a fundamental wave current of the node, is a harmonic disturbance current.

[0068] S2, calculate a small-signal relationship between a port voltage and a current of each power electronic device in the system to obtain a frequency coupling model of the converter;

[0069] The frequency coupling model of the converter is as follows:

[0070]

[0071] wherein , , , denotes a coefficient matrix, which is determined by the steady state operating point of the converter. is the output current of the converter, is the conjugate of is the grid voltage, is the conjugate of .

[0072] The converter model is a frequency coupled model based on harmonic transfer functions, wherein is a frequency coupled phase.

[0073] S3, two equations are solved simultaneously to eliminate the voltage, obtaining a small signal equation containing the converter frequency coupled model, the grid and the harmonic current disturbance;

[0074] The grid equation and the converter frequency coupled model are solved simultaneously to obtain a small signal equation containing the converter frequency coupled model, the grid and the harmonic current disturbance:

[0075]

[0076] wherein , is a harmonic matrix according to the change of the harmonic impedance matrix, is a harmonic disturbance current, is the conjugate of is the grid voltage, is the conjugate of .

[0077] S4, only the fundamental grid voltage is contained as the initial state of the system, and the initial steady state quantity is solved;

[0078] S5, the large disturbance of the harmonic current is divided into multiple stages, and the disturbance is increased in stages, and the disturbance size of each stage meets the requirements of small signal calculation;

[0079] The harmonic current disturbance is added step by step, and multiple stages of small signal linearization are adopted, and in each stage, the small signal equation of the next stage is updated according to the calculation result of the last stage, that is, the coefficient matrix, and then the steady state result under large disturbance is calculated.

[0080] S6, the small signal equation set of the system is updated, and the disturbance of the next stage is added until the amplitude of the harmonic current disturbance is the same as the set target.

[0081] S601, the small signal equation is calculated to obtain the small disturbance response of each state variable under the harmonic current disturbance in each stage;​​

[0082] S602, superimpose the small disturbance response of each state variable solved in this stage to its steady-state component, update the small signal equation set of the system;

[0083] S603, superimpose the disturbance of the next stage, repeat S601-S602 until the amplitude of the harmonic current disturbance is the same as the set target.

[0084] The application can effectively calculate the nonlinear coupling effect of harmonics between devices in the device cluster through small signal step-by-step calculation, and not only the linear harmonic superposition of a single device.

[0085] The interaction of harmonics in the device cluster is described by considering the frequency coupling characteristics between the converters. In the device cluster, the harmonic currents of multiple converters are superimposed in the same frequency band. The output current interaction coupling characteristics under the harmonic current disturbance are calculated in a small signal step-by-step manner.

[0086] In addition, the application also fully considers the influence of the network impedance of the power distribution network system on the harmonic characteristics of the device cluster. By incorporating the network impedance into the calculation model, the application can more accurately evaluate the harmonic propagation of the power electronic device cluster after being connected to the grid, and provide a more comprehensive theoretical basis for the analysis and optimization of power quality.

[0087] Therefore, the method of the application improves the accuracy of the harmonic emission calculation of the power electronic device cluster, and has important theoretical value and practical application prospect.

[0088] Those skilled in the art can understand that various aspects of the application can be implemented as a system, a method or a program product. Therefore, various aspects of the application can be specifically implemented in the following forms, namely: a complete hardware implementation, a complete software implementation (including firmware, microcode, etc.), or a combination of hardware and software aspects, which can be collectively referred to as "circuit", "module" or "platform" here.

[0089] In another embodiment of the application, a high-precision analysis system for multi-frequency harmonic disturbed coupling current of a converter cluster is provided, which can be used to implement the high-precision analysis method for multi-frequency harmonic disturbed coupling current of a converter cluster as described above. Specifically, the high-precision analysis system for multi-frequency harmonic disturbed coupling current of a converter cluster comprises a node module, a calculation module, a simultaneous module, a division module and an updating module.

[0090] The node module obtains network node equations.

[0091] The calculation module calculates the small signal relationship between the port voltage and current of each power electronic device in the system to obtain a frequency coupling model of the converter.

[0092] The frequency coupling model of the converter, the network node equation and the frequency coupling model of the converter are solved simultaneously, the voltage is eliminated, and a small signal equation containing the frequency coupling model of the converter, the network frame and the harmonic current disturbance is obtained;

[0093] The initial steady-state quantity is solved by taking only the fundamental grid voltage as the initial state of the system.

[0094] The small signal equation set of the system is updated, the disturbance of the next stage is superimposed, and the amplitude of the harmonic current disturbance is the same as the set target until the amplitude of the harmonic current disturbance is the same as the set target.

[0095] In another embodiment of the present application, a terminal device is provided, which comprises a processor and a memory, the memory is used to store a computer program, the computer program comprises program instructions, and the processor is used to execute 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, etc., which are the computing core and control core of the terminal, and are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions to implement a corresponding method flow or a corresponding function; the processor in the embodiment of the present application can be used for the operation of the converter cluster multi-frequency harmonic disturbed coupling current high-precision analysis method, which comprises:

[0096] The network node equation is obtained, the small signal relationship between the port voltage and current of each power electronic equipment in the system is calculated, the frequency coupling model of the converter is obtained, the network node equation and the frequency coupling model of the converter are solved simultaneously, the voltage is eliminated, a small signal equation containing the frequency coupling model of the converter, the network frame and the harmonic current disturbance is obtained, only the fundamental grid voltage is taken as the initial state of the system, the initial steady-state quantity is solved, the large disturbance of the harmonic current is divided into multiple stages, the disturbance is increased in stages, and the disturbance size of each stage meets the requirement of small signal calculation, the small signal equation set of the system is updated, the disturbance of the next stage is superimposed, and the amplitude of the harmonic current disturbance is the same as the set target until the amplitude of the harmonic current disturbance is the same as the set target.

[0097] Referring to Figure 3 , the terminal device is a computer device, the computer device 60 of this embodiment includes a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61, and the computer program 63 implements the converter cluster multi-frequency harmonic disturbed coupling current high-precision analysis method in the embodiment when executed by the processor 61. To avoid repetition, details are not repeated here. Alternatively, the computer program 63 implements the functions of each model / unit in the converter cluster multi-frequency harmonic disturbed coupling current high-precision analysis system when executed by the processor 61. To avoid repetition, details are not repeated here.

[0098] The computer device 60 can be a desktop computer, a notebook computer, a palm computer, a cloud server, and the like. 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 3 The computer device 60 is only an example 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, and the like.

[0099] 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 gate or transistor logic devices, discrete hardware components, and the like. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0100] 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, and the like.

[0101] Further, the memory 62 can include both an internal storage unit of the computer device 60 and an external storage device. 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 is to be output.

[0102] Referring to Figure 4 The terminal device is a chip, and the chip 600 of the embodiment includes one or more processors 622 and a memory 632 for storing computer programs executable by the processor 622. The computer programs stored in the memory 632 can include one or more modules each corresponding to a set of instructions. In addition, the processor 622 can be configured to execute the computer programs to perform the high-precision analysis method of the multi-frequency harmonic disturbed coupling current of the converter cluster.

[0103] In addition, the chip 600 can further include a power supply component 626 configured to perform power management of the chip 600 and a communication component 650 configured to implement communication of the chip 600, such as wired or wireless communication. In addition, the chip 600 can further include an input / output interface 658. The chip 600 can operate based on an operating system stored in the memory 632.

[0104] In another embodiment of the present application, the present application also provides a storage medium, specifically a computer readable storage medium, which is a memory device in a terminal device and is used to store programs and data. It can be understood that the computer readable storage medium herein can include an internal storage medium of the terminal device, and of course can also include an expansion storage medium supported by the terminal device. The computer readable storage medium provides a storage space, and the storage space stores an operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and the instructions can be one or more computer programs. It should be noted that the computer readable storage medium herein can be a high-speed RAM memory or a non-volatile memory such as at least one disk memory.

[0105] The one or more instructions stored in the computer readable storage medium can be loaded and executed by the processor to implement the corresponding steps of the high-precision analysis method of the multi-frequency harmonic disturbed coupling current of the converter cluster in the above embodiments; the one or more instructions stored in the computer readable storage medium are loaded and executed by the processor as follows:

[0106] The network node equation is obtained; the small-signal relationship of the port voltage and current of each power electronic equipment in the system is calculated to obtain the frequency coupling model of the converter; the network node equation and the frequency coupling model of the converter are solved together, the voltage is eliminated, and a small-signal equation containing the frequency coupling model of the converter, the network frame and the harmonic current disturbance is obtained; only the fundamental grid voltage is used as the initial state of the system, and the initial steady-state quantity is solved; the large disturbance of the harmonic current is divided into multiple stages, and the disturbance is increased in stages, and the disturbance size of each stage meets the requirements of small-signal calculation; the small-signal equation set of the system is updated, the disturbance of the next stage is superimposed, until the amplitude of the harmonic current disturbance is the same as the set target.

[0107] 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 but not all embodiments of the present application. 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. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0108] The effectiveness and accuracy of the method proposed in the present application are verified by building a corresponding simulation model.

[0109] Please refer to Figure 1 The verification scene of the present application is as follows:

[0110] The scene contains 6 nodes, one converter device is connected to each of nodes 1, 2, and 3, and three devices are connected to node 4 to form a cluster of power electronic equipment. A harmonic current source is connected to node 5.

[0111] The specific parameters of the line impedance are shown in Table 1:

[0112] Table 1

[0113]

[0114] In the simulation verification, the harmonic current source injects 5th, 7th, 23rd, and 25th harmonics into the power grid.

[0115] Please refer to Fig. 2, the comparison results of the method and simulation results of the present application. Fig. (2-a) is the harmonic current spectrum of node 1 under disturbance and its error, Fig. (2-b) is the harmonic current spectrum of node 2 under disturbance and its error, Fig. (2-c) is the harmonic current spectrum of node 3 under disturbance and its error, and Table 2 calculates the accuracy of the comparison between the proposed method and simulation results.

[0116] Table 2

[0117]

[0118] According to the comparison results, the scheme accurately describes the harmonic emission characteristics of the converter cluster under disturbance, and the amplitude calculation error is less than 1%.

[0119] In summary, the present application is a kind of high-precision analysis method and system for multi-frequency harmonic disturbed coupling current of converter cluster, which considers the influence of harmonic interaction effect in equipment cluster and network impedance.Compared with traditional methods, it can more accurately describe the harmonic characteristics of converter cluster, and can more comprehensively and accurately analyze the interaction characteristics between power electronic equipment cluster and distribution network.

[0120] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the above-mentioned division of each functional unit and module is exemplified, and in actual application, the above-mentioned 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 exist physically, 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 present application. The specific working process of the units and modules in the system can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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 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.

[0125] 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.

[0126] 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.

[0127] 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 functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocks Figure 1 The functions specified in one or more flows and / or blocks

[0128] These computer program instructions can also be stored in a computer-readable memory that can direct 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 functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocks Figure 1 The functions specified in one or more flows and / or blocks

[0129] 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 functions specified in the flowchart Figure 1 one flow or multiple flows and / or the functions specified in the block Figure 1 one flow or multiple flows and / or the functions specified in the block

[0130] 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 high-precision analysis method for multi-frequency harmonic disturbed coupled current of a converter cluster, characterized by: The following steps are involved: S1. Obtain network node equations; S2. Calculate the small signal relationship between the voltage and current at the ports of each power electronic device in the system to obtain the frequency coupling model of the converter; S3, combine the network node equations and the frequency coupling model of the converter, eliminate the voltage, and obtain the small signal equation including the frequency coupling model of the converter, the grid and the harmonic current disturbance; S4. Take the grid voltage containing only the fundamental wave as the initial state of the system and solve the initial steady-state quantity; S5. Divide the large disturbance of harmonic current into multiple stages and increase the disturbance in steps. The disturbance size of each stage meets the requirements of small signal calculation. S6. Use the calculation results of the previous stage as the new steady-state operating point, update the system's small signal equations, and superimpose the disturbance of the next stage until the amplitude of the harmonic current disturbance is the same as the set target. Specifically: Calculate the small perturbation response of each state variable under the harmonic current perturbation in each stage of the small signal equation; The small perturbation responses of each state variable solved in the previous stage are superimposed on its steady-state component as the new steady-state operating point, and the small signal equations of the system are updated; The disturbance of the next stage is superimposed and repeated until the amplitude of the harmonic current disturbance is the same as the set target, ensuring the consistency of the total disturbance size.

2. The high-precision analysis method for multi-frequency harmonic disturbed coupled current of a converter cluster according to claim 1 is characterized in that: The network node equation is as follows: in, is the node fundamental impedance matrix, is the harmonic impedance matrix, is the node voltage, is the fundamental current of the node, is the harmonic disturbance current.

3. The high-precision analysis method for multi-frequency harmonic disturbed coupled current of a converter cluster according to claim 1, characterized in that: The frequency coupling model of the converter adopts a frequency coupling model based on harmonic transfer function, where The phase is a frequency-coupled phase; the frequency coupling model of the converter is as follows: in, , , , represents the coefficient matrix, is the output current of the converter, for The conjugate of is the grid voltage, for The conjugation of .

4. The high-precision analysis method for multi-frequency harmonic disturbed coupled current of a converter cluster according to claim 1, characterized in that: Small signal equation: in, , is the harmonic matrix obtained from the change of harmonic impedance matrix, is the harmonic disturbance current, for The conjugate of is the converter output current for each node, for The conjugation of .

5. The high-precision analysis method for multi-frequency harmonic disturbed coupled current of a converter cluster according to claim 1, characterized in that: The large disturbance of harmonic current is divided into several stages: The harmonic current disturbance is superimposed in steps and small signal linearization is adopted in multiple stages to ensure the accuracy and rationality of the calculation results using small signal equations in each stage.

6. A high-precision analysis system for multi-frequency harmonic disturbed coupled current of a converter cluster, characterized in that: include: Node module, obtains network node equations; The calculation module calculates the small signal relationship between the voltage and current at the port of each power electronic device in the system and obtains the frequency coupling model of the converter; A simultaneous module combines the network node equations and the frequency coupling model of the converter, eliminates the voltage, and obtains a small signal equation that includes the frequency coupling model of the converter, the grid, and the harmonic current disturbance; Divide the modules, take the grid voltage containing only the fundamental wave as the initial state of the system, and solve the initial steady-state quantity; divide the large disturbance of the harmonic current into multiple stages, and increase the disturbance in stages. The disturbance size of each stage meets the requirements of small signal calculation; Update module, update the system's small signal equations, and superimpose the disturbance of the next stage until the amplitude of the harmonic current disturbance is the same as the set target, specifically: Calculate the small perturbation response of each state variable under the harmonic current perturbation in each stage of the small signal equation; The small perturbation responses of each state variable solved in the previous stage are superimposed on its steady-state component as the new steady-state operating point, and the small signal equations of the system are updated; The disturbance of the next stage is superimposed and repeated until the amplitude of the harmonic current disturbance is the same as the set target, ensuring the consistency of the total disturbance size.

7. A computer-readable storage medium storing one or more programs, characterized in that: The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform the method of any one of claims 1 to 5.

8. A computing device, characterized in that include: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include steps for executing the method according to any one of claims 1 to 5.

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