Self-adaptive active harmonic resistance control method and system based on constructed network

Abstract

The invention discloses a self-adaptive active harmonic resistance control method and system based on a constructed network, and belongs to the technical field of converter control. Port current harmonic components of a d axis and a q axis of a constructed network converter are respectively extracted under a rotating coordinate system; calculating amplitude information of d-axis and q-axis harmonic components of the grid-forming converter under the rotating coordinate system by using the obtained result; then calculating amplitude information of a port current harmonic component of the network construction converter; feeding the obtained result and preset amplitude information into a controller, wherein the output result of the controller is a virtual resistance parameter value; and respectively multiplying the port current harmonic components of the d axis and the q axis of the grid-forming converter by the virtual resistance parameter value, and performing closed-loop control as a part of a voltage loop instruction. According to the resonance suppression strategy provided by the invention, on the premise that only the port current of the converter needs to be collected, the parameters of the virtual resistor are adaptively adjusted, and resonance suppression is realized.

Description

Background Art

[0002] By the end of 2023, the cumulative installed capacity of wind power generation will be 440 million kilowatts, and the cumulative installed capacity of photovoltaic power generation will be 610 million kilowatts, accounting for 36% of the current total installed capacity, and the annual increase is still increasing year by year. At the same time, the large-scale grid connection of new energy means that a large number of power electronic equipment are connected to the grid, which brings a series of problems to the stable operation of the grid.

[0003] At present, the grid-connected control of new energy sources such as wind power and photovoltaic power is mainly based on grid-following converters. Grid-following converters are synchronized with the grid voltage through a phase-locked loop and connected to the grid using current control. They show the characteristics of a "current source" to the outside world. They are widely used because of their simple control structure and mature technology. However, from the perspective of impedance, the impedance characteristics of grid-following converters are resistive-capacitive within a wide frequency band, which easily interacts with the grid to produce LCr resonance.

[0004] Based on this background, the grid-type control method has become the focus of more and more scholars. The grid-type converter achieves synchronization with the power grid through frequency synchronization control, which effectively avoids the instability factors introduced by the phase-locked loop control loop. From the perspective of impedance analysis, although the grid-type converter can ensure that the system phase margin is greater than 0 after interacting with the power grid, the low frequency band below 50Hz may still have the problem of insufficient phase margin and cause oscillation.

[0005] At present, some studies have proposed a virtual impedance strategy, which can effectively change the output impedance characteristics of the grid-connected converter, thereby providing a larger phase margin for the system grid connection. However, this method also changes the impedance characteristics of the grid-connected converter at the fundamental frequency, thereby affecting the steady-state operating point. For grid-connected converters, the technical means of controlling their resistance characteristics at frequencies other than harmonics are already quite mature, but there is still little research on the technology of controlling the resistance characteristics of grid-connected converters at frequencies other than fundamental frequencies. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method and system for controlling a meshed adaptive active harmonic resistor in response to the above-mentioned deficiencies in the prior art, so as to solve the technical problem that the meshed control method has insufficient phase margin in the low frequency band, thereby causing oscillation.

[0007] The present invention adopts the following technical solutions:

[0008] A method for controlling a network-based adaptive active harmonic resistor comprises the following steps:

[0009] The port current harmonic components of the d-axis and q-axis of the grid-type converter are extracted respectively in the rotating coordinate system;

[0010] The amplitude information of the d-axis and q-axis harmonic components of the grid-type converter is calculated in the rotating coordinate system by using the port current harmonic components of the d-axis and q-axis of the grid-type converter;

[0011] The amplitude information of the harmonic components of the d-axis and q-axis harmonic components of the grid-forming converter is used to calculate the amplitude information of the harmonic components of the port current of the grid-forming converter;

[0012] The amplitude information of the harmonic component of the current at the grid converter port and the preset amplitude information are fed into the controller, and the result output by the controller is used as the virtual resistance parameter value R h ;

[0013] Multiply the harmonic components of the port currents on the d-axis and q-axis of the grid-type converter by the virtual resistance parameter value R h , used as voltage loop instruction for closed-loop control.

[0014] Preferably, the extraction of the port current harmonic components of the d-axis and q-axis of the grid-type converter is specifically as follows:

[0015] The three-phase current i of the grid-connected converter port ga ,i gb ,i gc Perform Park transform to obtain the d-axis and q-axis components i gd and i gq ;

[0016] The fundamental component of the current is transformed into a DC quantity, and the remaining harmonic components are AC quantities. The results after Park transformation are respectively passed through a second-order low-pass filter to obtain the DC component;

[0017] With d-axis and q-axis components i gd and i gq After subtracting the DC component, the remaining AC component i gdh and i gqh , that is, the harmonic component in the three-phase coordinate system.

[0018] Preferably, the d-axis and q-axis components i gd and i gq Specifically:

[0019]

[0020] Where ω represents the fundamental angular frequency, t is time, i ga is the current of phase a on the grid side, i gb is the phase b current on the grid side, i gc is the c-phase current on the grid side.

[0021] Preferably, the transfer function G of the second-order low-pass filter is LPF (s) is expressed as

[0022]

[0023] Among them, f c is the cut-off frequency, s is the Laplace operator, and ξ is the damping ratio.

[0024] Preferably, the amplitude information of the d-axis and q-axis harmonic components of the grid-type converter in the rotating coordinate system is specifically:

[0025] The harmonic components i of the port currents on the d-axis and q-axis of the grid-connected converter are gdh and i gqh The squares are taken to represent the amplitude information of the d-axis and q-axis harmonic contents of the grid-connected converter.

[0026] Preferably, the amplitude information of the harmonic component of the current at the port of the grid-connected converter is calculated as follows:

[0027] The mean square value of the harmonic components of the d-axis and q-axis is sent to a first-order low-pass filter to filter out the fluctuation component, and the amplitude information of the harmonic component of the current at the port of the grid converter is obtained. Specifically expressed as After low-pass filter G LPF1 The value of (s).

[0028] Preferably, the transfer function G LPF1 (s) is:

[0029]

[0030] Among them, s is the Laplace operator, f c1 is the low-pass filter cutoff frequency.

[0031] Preferably, the controller selects a proportional-integral controller, specifically:

[0032]

[0033] Among them, k p is the proportionality coefficient, k i is the integral coefficient, and s is the Laplace operator.

[0034] Preferably, when the bandwidth of the grid-type converter is greater than the constant A, the impedance characteristic of the grid-type converter in the frequency band less than A is controlled to have an amplitude of R h , resistance characteristics with phase 0.

[0035] In a second aspect, an embodiment of the present invention provides a network-based adaptive active harmonic resistance control system, including:

[0036] An extraction module is used to extract the port current harmonic components of the d-axis and q-axis of the grid-type converter in a rotating coordinate system;

[0037] The first calculation module calculates the amplitude information of the d-axis and q-axis harmonic components of the grid-type converter in the rotating coordinate system using the port current harmonic components of the d-axis and q-axis of the grid-type converter;

[0038] The second calculation module calculates the amplitude information of the harmonic component of the port current of the grid-forming converter by using the amplitude information of the d-axis and q-axis harmonic components of the grid-forming converter;

[0039] The feedback module feeds the amplitude information of the harmonic component of the current at the port of the grid-forming converter and the preset amplitude information into the controller, and uses the result output by the controller as the virtual resistance parameter value;

[0040] The control module multiplies the port current harmonic components of the d-axis and q-axis of the grid-type converter by the virtual resistance parameter value respectively, and performs closed-loop control as a part of the voltage loop instruction.

[0041] 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, wherein the processor implements the steps of the above-mentioned method for controlling a network-based adaptive active harmonic resistor when executing the computer program.

[0042] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, including a computer program, which, when executed by a processor, implements the steps of the above-mentioned mesh-based adaptive active harmonic resistance control method.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] A grid-based adaptive active harmonic resistance control method, in which only the three-phase current of the grid-based converter port is sampled, controls the grid-based converter to present resistance characteristics at frequency points other than the fundamental wave, thereby avoiding oscillation with the inductive power grid. Accurately extracting the harmonic components of the port current can improve the accuracy of the overall control, and the current harmonic amplitude information and the preset harmonic amplitude information are proportionally-integrated to adjust the virtual resistance value adaptively, so that resonance suppression can be achieved under different working conditions. The harmonic current command and the virtual resistance value are multiplied and then controlled as part of the voltage command, so that the grid-based converter can present resistance characteristics at frequency points other than the fundamental wave, avoiding oscillation after interaction with the power grid.

[0045] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0046] In summary, the present invention uses a control method to make the grid-type converter present a resistance characteristic in a frequency band other than the fundamental wave, so as to avoid "LCr" oscillation between the grid-type converter and the power grid.

[0047] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A control block diagram of a grid-type converter according to an embodiment of the present invention;

[0049] Figure 2 The impedance curve diagram of the grid-type converter and the grid according to the embodiment of the present invention;

[0050] Figure 3 The embodiment of the present invention is a grid-type converter and L g =Oscillation diagram after grid impedance interaction of 5mH;

[0051] Figure 4 This is a block diagram of a network-based adaptive active harmonic resistance control according to an embodiment of the present invention;

[0052] Figure 5 The impedance curve of the grid-type converter after active harmonic resistance control;

[0053] Figure 6 This is a waveform diagram of the voltage at the common node after adding an active harmonic resistance link in the embodiment of the present invention;

[0054] Figure 7 This is a diagram for verifying the oscillation suppression effect under different working conditions of the embodiment of the present invention;

[0055] Figure 8 The waveform diagram of node voltage and port current when rated power changes in an embodiment of the present invention;

[0056] Fig. 9 It is a waveform diagram of node voltage and port current when the grid inductance changes according to an embodiment of the present invention;

[0057] Fig.10 A schematic diagram of a computer device provided by an embodiment of the present invention;

[0058] Fig.11 The present invention is a block diagram of an electronic device provided according to an embodiment. DETAILED DESCRIPTION

[0059] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0061] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0062] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to 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: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0063] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0064] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0065] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0066] The present invention provides a method for controlling a mesh-type adaptive active harmonic resistor. The control method enables a mesh-type converter to exhibit resistance characteristics in frequency bands other than the fundamental wave to suppress oscillations between the mesh-type converter and the power grid, and adaptively adjusts the presented resistance amplitude according to actual working conditions. The entire process only requires sampling of the three-phase current of the port of the mesh-type converter, which is used to increase the phase margin at the interaction frequency point between the mesh-type converter and the power grid to avoid oscillations.

[0067] See also Figure 1 The present invention provides a method for controlling a network-based adaptive active harmonic resistor, comprising the following steps:

[0068] S1. Extract the port current harmonic components of the d-axis and q-axis of the grid-type converter in the rotating coordinate system;

[0069] S101, collect the three-phase current i at the port of the grid-forming converter ga ,i gb ,i gc Perform Park transform to obtain the d-axis and q-axis components i gd and i gq ;

[0070] The transformation relationship is:

[0071]

[0072] Where ω represents the fundamental angular frequency, i ga is the current of phase a on the grid side, i gb is the phase b current on the grid side, i gc is the c-phase current on the grid side.

[0073] S102, after Park transformation, the fundamental component of the current is transformed into a DC quantity, and the remaining harmonic components are still AC quantities, and the results after Park transformation are respectively passed through a second-order low-pass filter to obtain a DC component;

[0074] Cut-off frequency f c The frequency is set to 10 Hz, the damping ratio ξ is set to 0.707, and the transfer function of the second-order low-pass filter is G LPF (s) is expressed as

[0075]

[0076] Among them, i gd and i gq After passing through a second-order low-pass filter, the DC component is obtained, which is the fundamental frequency component in the three-phase coordinate system.

[0077] S103, use i gd and i gq After subtracting the DC component, the remaining AC component igdh and i gqh , that is, the harmonic component in the three-phase coordinate system.

[0078] S2, using the port current harmonic components of the d-axis and q-axis of the grid-type converter obtained in step S1 to calculate the amplitude information of the harmonic components of the d-axis and q-axis of the grid-type converter in the rotating coordinate system;

[0079] to i gdh and i gqh The squares represent the amplitude information of the d-axis and q-axis harmonic content respectively.

[0080] S3, using the amplitude information of the d-axis and q-axis harmonic components of the grid-type converter obtained in step S2 to calculate the amplitude information of the harmonic components of the port current of the grid-type converter;

[0081] The mean square value of the harmonic components of the d-axis and q-axis is sent to a first-order low-pass filter to filter out the fluctuation component, and the amplitude information of the harmonic components of the current at the port of the grid converter is obtained. The cut-off frequency f of the first-order low-pass filter is c1 Set to 50Hz, its transfer function is described as:

[0082]

[0083] Amplitude information of harmonic components of current at the ports of grid-connected converters Expressed as After low-pass filter G LPF1 The value of (s).

[0084] S4, feeding the amplitude information of the harmonic component of the current at the port of the grid-connected converter obtained in step S3 and the preset amplitude information into the controller, and taking the result output by the controller as the virtual resistance parameter value;

[0085] Will and preset harmonic current amplitude information Feed into the controller, the controller selects the proportional-integral controller, which is expressed as:

[0086]

[0087] Among them, k p is the proportionality coefficient, k i is the integral coefficient, and s is the Laplace operator.

[0088] The output of the controller is used as a virtual resistance value R h , ensuring that the harmonic component of the grid converter port current is controlled near the preset component and that the harmonic component does not exceed the standard.

[0089] S5. Multiply the port current harmonic components of the d-axis and q-axis of the grid-type converter obtained in step S1 by the virtual resistance parameter value obtained in step S4 respectively, and perform closed-loop control as part of the voltage loop instruction to achieve grid-type adaptive active harmonic resistance control.

[0090] will i gdh and i gqh Multiply by R h Then we get the harmonic voltage command v dhref and v qhref , the voltage command is superimposed on the voltage command of the originally running grid-type converter to realize the control of frequency points other than the fundamental wave.

[0091] When the bandwidth of the grid-type converter is greater than the constant A, the impedance characteristic of the grid-type converter in the frequency band less than the constant A is controlled to have an amplitude of R h , resistance characteristics with phase 0.

[0092] It will be appreciated by those skilled in the art that various aspects of the present invention may be implemented as systems, methods or program products. Therefore, various aspects of the present invention may be specifically implemented in the following forms, namely: complete hardware implementation, complete software implementation (including firmware, microcode, etc.), or a combination of hardware and software implementations, which may be collectively referred to herein as "circuits", "modules" or "platforms".

[0093] In another embodiment of the present invention, a mesh-based adaptive active harmonic resistor control system is provided, which can be used to implement the above-mentioned mesh-based adaptive active harmonic resistor control method. Specifically, the mesh-based adaptive active harmonic resistor control system includes an extraction module, a first calculation module, a second calculation module, a feedback module and a control module.

[0094] Among them, the extraction module extracts the port current harmonic components of the d-axis and q-axis of the grid-type converter respectively in the rotating coordinate system;

[0095] The first calculation module calculates the amplitude information of the d-axis and q-axis harmonic components of the grid-type converter in the rotating coordinate system using the port current harmonic components of the d-axis and q-axis of the grid-type converter;

[0096] The second calculation module calculates the amplitude information of the harmonic component of the port current of the grid-forming converter by using the amplitude information of the d-axis and q-axis harmonic components of the grid-forming converter;

[0097] The feedback module feeds the amplitude information of the harmonic component of the current at the port of the grid-forming converter and the preset amplitude information into the controller, and uses the result output by the controller as the virtual resistance parameter value;

[0098] The control module multiplies the port current harmonic components of the d-axis and q-axis of the grid-type converter by the virtual resistance parameter value respectively, and performs closed-loop control as a part of the voltage loop instruction.

[0099] In another embodiment of the present invention, a terminal device is provided, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation based on the network-based adaptive active harmonic resistance control method, including:

[0100] The port current harmonic components of the d-axis and q-axis of the grid-type converter are extracted respectively in the rotating coordinate system; the amplitude information of the d-axis and q-axis harmonic components of the grid-type converter in the rotating coordinate system is calculated using the port current harmonic components of the d-axis and q-axis of the grid-type converter; the amplitude information of the port current harmonic components of the grid-type converter is calculated using the amplitude information of the d-axis and q-axis harmonic components of the grid-type converter; the amplitude information of the port current harmonic components of the grid-type converter and the preset amplitude information are fed into the controller, and the result output by the controller is used as the virtual resistance parameter value; the port current harmonic components of the d-axis and q-axis of the grid-type converter are multiplied by the virtual resistance parameter value respectively, and closed-loop control is performed as part of the voltage loop instruction.

[0101] In another embodiment of the present invention, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a terminal device for storing programs and data. It is understandable that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and the extended storage medium supported by the terminal device, and can be any tangible medium containing or storing a program, which can be used by an instruction execution system, device or device or used in combination with it. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that more specific examples (non-exhaustive list) of the computer-readable storage medium here include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0102] Computer readable storage media also include data signals propagated in baseband or as part of a carrier wave, which carry readable program codes. Such propagated data signals can take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The readable storage medium can also be any readable medium other than a readable storage medium, which can send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, device, or device. The program code contained on the readable storage medium can be transmitted using any appropriate medium, including but not limited to wireless, wired, optical cable, RF, etc., or any suitable combination of the above.

[0103] Program code for performing the operations of the present invention may 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" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a separate software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the case of a remote computing device, the remote computing device may be connected to the user computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computing device (e.g., through the Internet using an Internet service provider).

[0104] One or more instructions stored in a computer-readable storage medium may be loaded and executed by a processor to implement the corresponding steps of the control method based on a meshed adaptive active harmonic resistor in the above embodiment; one or more instructions in the computer-readable storage medium may be loaded and executed by a processor as follows:

[0105] The port current harmonic components of the d-axis and q-axis of the grid-type converter are extracted respectively in the rotating coordinate system; the amplitude information of the d-axis and q-axis harmonic components of the grid-type converter in the rotating coordinate system is calculated using the port current harmonic components of the d-axis and q-axis of the grid-type converter; the amplitude information of the port current harmonic components of the grid-type converter is calculated using the amplitude information of the d-axis and q-axis harmonic components of the grid-type converter; the amplitude information of the port current harmonic components of the grid-type converter and the preset amplitude information are fed into the controller, and the result output by the controller is used as the virtual resistance parameter value; the port current harmonic components of the d-axis and q-axis of the grid-type converter are multiplied by the virtual resistance parameter value respectively, and closed-loop control is performed as part of the voltage loop instruction.

[0106] See also Fig.10 , the terminal device is a computer device, and 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. When the computer program 63 is executed by the processor 61, the method for calculating the composition of fluid in the reservoir transformation wellbore in the embodiment is realized. To avoid repetition, it is not described one by one here. Alternatively, when the computer program 63 is executed by the processor 61, the functions of each model / unit in the calculation system for the composition of fluid in the reservoir transformation wellbore in the embodiment are realized. To avoid repetition, it is not described one by one here.

[0107] The computer device 60 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will appreciate that Fig.10 This is only an example of the computer device 60 and does not constitute a limitation of the computer device 60. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0108] The processor 61 may be a central processing unit (CPU), or other general-purpose processors, central processing units, graphics processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, data processing logic based on quantum computing, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc.

[0109] The memory 62 may be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 may 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.

[0110] Furthermore, the memory 62 may 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 may also be used to temporarily store data that has been output or is to be output.

[0111] Any reference to memory, database or other media used in the embodiments provided in the present application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0112] The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a distributed database based on blockchain, etc., but is not limited thereto. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but is not limited thereto.

[0113] See also Fig.11 The terminal device 600 is an electronic device, and the electronic device is in the form of a general computing device. The components of the electronic device may include but are not limited to: at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different platform components (including the storage unit 620 and the processing unit 610), a display unit 640, etc.

[0114] The storage unit stores program codes, which can be executed by the processing unit 610, so that the processing unit 610 performs the steps according to various exemplary embodiments of the present invention described in the above method section of this specification. For example, the processing unit 610 can perform the following steps: Figure 1 Follow the steps shown in .

[0115] The storage unit 620 may include a readable medium in the form of a volatile storage unit, such as a random access memory unit (RAM) 6201 and / or a cache memory unit 6202 , and may further include a read-only memory unit (ROM) 6203 .

[0116] The storage unit 620 may also include a program / utility 6204 having a set (at least one) of program modules 6205, such program modules 6205 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment.

[0117] Bus 630 may represent one or more of several types of bus structures, including a memory unit bus or memory unit controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.

[0118] The electronic device 600 may also communicate with one or more external devices 700 (e.g., keyboards, pointing devices, Bluetooth devices, etc.), may also communicate with one or more devices that enable a user to interact with the electronic device 600, and / or communicate with any device that enables the electronic device 600 to communicate with one or more other computing devices (e.g., routers, modems, etc.). Such communication may be performed via an input / output (I / O) interface 650. Furthermore, the electronic device 600 may also communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network, such as the Internet) via a network adapter 660. The network adapter 660 may communicate with other modules of the electronic device 600 via a bus 630. It should be understood that, although not shown in the figure, other hardware and / or software modules may be used in conjunction with the 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.

[0119] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0120] The present invention only samples the grid-side current information of the converter to control the impedance characteristics of the grid-type converter, presenting resistance characteristics at frequency bands other than the fundamental wave, thereby avoiding possible oscillations with the grid, as follows:

[0121] First, extract the harmonic component i of the grid-side current of the grid-type converter in the dq coordinate system gdh and i gqh ;

[0122] Then the grid-side current harmonic component i gdh and i gqh Multiply by the virtual resistance value R h , as the instruction of the harmonic part of the voltage loop for closed loop control.

[0123] According to the change of working conditions, the virtual resistance value R is adaptively adjusted h , so that it always suppresses oscillation, as follows:

[0124] First, use the extracted i gdh and i gqh , we can get the amplitude information of harmonic components, namely:

[0125] Then the amplitude information characterizing the harmonic components and the preset amplitude information are fed into the proportional-integral controller, and the output is used as the virtual resistance value R h , to achieve adaptive changes under different working conditions.

[0126] See also Figure 2 , is the impedance curve of the grid-type converter and the grid. It can be seen that after the grid-type converter interacts with the grid in the range of 1 to 50 Hz, the phase margin will be seriously insufficient, thus causing oscillation. g =5mH grid impedance interaction after the oscillation situation is as follows Figure 3 (a) is shown; the results of FFT analysis are shown in Figure 3 (b) shows that the main harmonic frequencies it contains are Figure 2 The interaction frequencies in the are consistent, all around 5 Hz.

[0127] See also Figure 4 , Figure 5 and Figure 6 , Figure 4 This is the block diagram of the network-based adaptive active harmonic resistance control; Figure 5 The impedance curve of the grid-type converter after active harmonic resistance control is shown in Figure 1. It can be seen that the impedance curve of the grid-type converter after active harmonic resistance control is shown in Figure 1. It shows resistance characteristics at all frequencies except the fundamental wave. Figure 6 is the voltage waveform of the common node after adding the active harmonic resistance link, and L g=5mH grid impedance interaction, the active harmonic resistance link is put into operation at t=2s. Figure 6 (a) It can be seen that after a short period of adjustment, the system enters steady-state operation. The voltage details during steady-state operation are shown in the figure below. Figure 6 As shown in (b), it can be seen that the suppression effect is quite good.

[0128] See also Figure 7 , which verifies the oscillation suppression effect under different working conditions. g When they are 10mH and 15mH respectively, the control effects of active harmonic resistance are as follows Figure 7 As shown in (a) and (b), it can be seen that as the grid inductance increases, the oscillation frequency gradually decreases, which is consistent with Figure 3 At this time, the active harmonic resistance control strategy can still suppress the resonance, which further illustrates the effectiveness and universality of this strategy.

[0129] The output power of the grid-connected converter is set to 10 kW, and the power command is switched to 20 kW and 15 kW at t=12s and t=14s respectively, and the adaptive adjustment function of the virtual resistance value is verified. Figure 8 The node voltage waveform and port current waveform when the rated power changes. It can be seen that under these three working conditions, the system can operate stably and the virtual resistance value is continuously adjusted adaptively.

[0130] The grid inductance is set to 15mH, and the grid inductance is changed to 7.5mH and 5mH at t=2s and t=4s respectively, and the adaptive adjustment function of the virtual resistance value is verified. Fig. 9 Figure 2 shows the node voltage waveform and port current waveform when the grid inductance changes. It can be seen that under these three working conditions, the system can operate stably and the virtual resistance value is continuously adjusted adaptively.

[0131] In summary, the present invention is a method and system for controlling a grid-type adaptive active harmonic resistance, which controls the grid-type converter to present resistance characteristics at frequencies other than the fundamental wave, thereby avoiding oscillations that may occur after the grid-type converter interacts with the power grid. In the case where only the current at the port of the grid-type converter is sampled during the entire process, proportional-integral control is performed according to the actual harmonic amplitude and the preset harmonic amplitude, and the virtual resistance value is adaptively adjusted to better suppress oscillations; the obtained harmonic voltage command is used as part of the voltage loop control to control the harmonic component, so that the grid-type converter presents resistance characteristics at frequencies other than the fundamental wave at the port, preventing oscillations that may occur when interacting with the power grid.

[0132] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0133] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0134] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the present invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0135] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0136] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0137] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0138] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0139] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, 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 generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0140] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0141] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0142] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for controlling a network-based adaptive active harmonic resistor, characterized in that: The following steps are involved: The port current harmonic components of the d-axis and q-axis of the grid-type converter are extracted respectively in the rotating coordinate system; The amplitude information of the d-axis and q-axis harmonic components of the grid-type converter is calculated in the rotating coordinate system by using the port current harmonic components of the d-axis and q-axis of the grid-type converter; The amplitude information of the harmonic components of the d-axis and q-axis harmonic components of the grid-forming converter is used to calculate the amplitude information of the harmonic components of the port current of the grid-forming converter; The amplitude information of the harmonic component of the current at the grid converter port and the preset amplitude information are fed into the controller, and the result output by the controller is used as the virtual resistance parameter value R h ; Multiply the harmonic components of the port currents on the d-axis and q-axis of the grid-type converter by the virtual resistance parameter value R h , used as voltage loop instruction for closed-loop control.

2. The method for controlling a network-based adaptive active harmonic resistor according to claim 1 is characterized in that: The specific extraction of the port current harmonic components of the d-axis and q-axis of the grid-type converter is: The three-phase current i of the grid-connected converter port ga ,i gb ,i gc Perform Park transform to obtain the d-axis and q-axis components i gd and i gq ; The fundamental component of the current is transformed into a DC quantity, and the remaining harmonic components are AC quantities. The results after Park transformation are respectively passed through a second-order low-pass filter to obtain the DC component; With d-axis and q-axis components i gd and i gq After subtracting the DC component, the remaining AC component i gdh and i gqh , that is, the harmonic component in the three-phase coordinate system.

3. The method for controlling a network-based adaptive active harmonic resistor according to claim 2 is characterized in that: The d-axis and q-axis components i gd and i gq Specifically: Where ω represents the fundamental angular frequency, t is time, i ga is the current of phase a on the grid side, i gb is the phase b current on the grid side, i gc is the c-phase current on the grid side.

4. The method for controlling a network-based adaptive active harmonic resistor according to claim 2 is characterized in that: The transfer function G of the second-order low-pass filter LPF (s) is expressed as Among them, f c is the cut-off frequency, s is the Laplace operator, and ξ is the damping ratio.

5. The method for controlling a network-based adaptive active harmonic resistor according to claim 1, characterized in that: The amplitude information of the d-axis and q-axis harmonic components of the grid-type converter in the rotating coordinate system is specifically: The harmonic components i of the port currents on the d-axis and q-axis of the grid-connected converter are gdh and i gqh The squares are taken to represent the amplitude information of the d-axis and q-axis harmonic contents of the grid-connected converter.

6. The method for controlling a network-based adaptive active harmonic resistor according to claim 1, characterized in that: The specific information for calculating the amplitude of the harmonic component of the current at the port of the grid-connected converter is: The mean square value of the harmonic components of the d-axis and q-axis is sent to a first-order low-pass filter to filter out the fluctuation component, and the amplitude information of the harmonic component of the current at the port of the grid converter is obtained. Specifically expressed as After low-pass filter G LPF1 The value of (s).

7. The method for controlling a network-based adaptive active harmonic resistor according to claim 6 is characterized in that: Transfer function G LPF1 (s) is: Among them, s is the Laplace operator, f c1 is the low-pass filter cutoff frequency.

8. The method for controlling a network-based adaptive active harmonic resistor according to claim 1, characterized in that: The controller selects the proportional-integral controller, specifically: Among them, k p is the proportionality coefficient, k i is the integral coefficient, and s is the Laplace operator.

9. The method for controlling a network-based adaptive active harmonic resistor according to claim 1, characterized in that: When the bandwidth of the grid-type converter is greater than the constant A, the impedance characteristic of the grid-type converter in the frequency band less than A is controlled to have an amplitude of R h , resistance characteristics with phase 0.

10. A network-based adaptive active harmonic resistance control system, characterized in that: include: An extraction module is used to extract the port current harmonic components of the d-axis and q-axis of the grid-type converter in a rotating coordinate system; The first calculation module calculates the amplitude information of the d-axis and q-axis harmonic components of the grid-type converter in the rotating coordinate system using the port current harmonic components of the d-axis and q-axis of the grid-type converter; The second calculation module calculates the amplitude information of the harmonic component of the port current of the grid-forming converter by using the amplitude information of the d-axis and q-axis harmonic components of the grid-forming converter; The feedback module feeds the amplitude information of the harmonic component of the current at the port of the grid-forming converter and the preset amplitude information into the controller, and uses the result output by the controller as the virtual resistance parameter value; The control module multiplies the port current harmonic components of the d-axis and q-axis of the grid-type converter by the virtual resistance parameter value respectively, and performs closed-loop control as a part of the voltage loop instruction.

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