GFM control method and system for active harmonic suppression, medium and equipment

Abstract

The invention relates to the technical field of power systems, and provides a GFM control method and system for active harmonic suppression, a medium and equipment. The GFM control method for active harmonic suppression comprises the steps of selecting a harmonic current frequency needing to be suppressed, superposing a GFM harmonic voltage source with a fixed amplitude gain and a fixed phase angle in a voltage outer loop control instruction, and determining an optimal compensation phase according to a voltage vector optimization process and a PCC harmonic voltage amplitude curve in iterative calculation; according to the obtained PCC voltage sampling data and GFM output current data of the GFM access node, a harmonic voltage component under the harmonic current frequency needing to be suppressed is separated, so that virtual harmonic impedance under the harmonic current frequency needing to be suppressed is constructed; under multiple constraints of a GFM stability domain and a modulation voltage limit value, determining an amplitude range of virtual harmonic impedance; and determining the optimal gain of the virtual harmonic impedance in the GFM stable domain. The harmonic current content of a GFM access power grid can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a GFM control method, system, medium and device for active harmonic suppression. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The typical control modes of renewable energy can be divided into two categories: grid-following (GFL) and grid-forming (GFM). GFL converters were used earlier and the technology is more mature. The premise of its stable operation is to obtain accurate grid phase through a phase-locked loop. Therefore, when the GFL converter is connected to a weak grid in a remote area or at the end of a distribution network, the waveform quality cannot be guaranteed due to the difficulty in tracking the grid phase. Compared with GFL, GFM has voltage source rather than current source characteristics. Therefore, GFM has stronger support capabilities and greater harmonic suppression potential in distorted grids.

[0004] At present, the research on GFM mainly focuses on its dynamic characteristics, inertia and damping. In the few studies that use GFM to participate in the improvement of grid harmonics, the method of coordinated control of active and passive means is usually adopted. Impedance regulation technology achieves harmonic current suppression in distorted grids by increasing the harmonic equivalent impedance; parallel admittance can make GFM exhibit similar characteristics to active power filters, thereby absorbing more harmonics in the grid. The inventors found that the control of GFM itself must face the difficult choice between the above two directions. The harmonic components that are not considered need to be improved by additional passive impedance. Current research has not yet found a method that relies solely on GFM active control to achieve stable suppression of grid-connected point harmonics in distorted grids. Summary of the invention

[0005] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a GFM control method, system, medium and equipment for active harmonic suppression, so as to realize the transformation of distorted power grid harmonic suppression from the current situation of GFM control and passive impedance coordinated control to the improvement of grid connection point harmonic problems completely supported by GFM independently.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: A first aspect of the present invention provides a GFM control method for active harmonic suppression.

[0007] A GFM control method for active harmonic suppression, comprising: Select the harmonic current frequency that needs to be suppressed, superimpose a GFM harmonic voltage source with a fixed amplitude gain and a fixed phase angle in the voltage outer loop control instruction, and determine the optimal compensation phase based on the voltage vector optimization process and the PCC harmonic voltage amplitude curve in the iterative calculation; According to the PCC voltage sampling data and GFM output current data of the GFM access node, the harmonic voltage components at the harmonic current frequency that needs to be suppressed are separated to construct the virtual harmonic impedance at the harmonic current frequency that needs to be suppressed; under the multiple constraints of the GFM stable domain and the modulation voltage limit, the amplitude range of the virtual harmonic impedance is determined; keeping the optimal compensation phase unchanged, the optimal gain of the virtual harmonic impedance in the GFM stable domain is determined within the amplitude range of the virtual harmonic impedance.

[0008] Furthermore, the optimal compensation phase is determined according to the compensation voltage vector optimization process and the PCC harmonic voltage amplitude curve in the iterative calculation; the method includes: Keep the fixed amplitude gain unchanged, so that the phase angle is iterated from 0 degrees to 360 degrees at a certain step size, and record the harmonic voltage amplitude of the PCC point after each phase angle change, and record the phase angle corresponding to the maximum value and the phase angle corresponding to the minimum value of the harmonic voltage at the PCC point during the vector optimization process; The phase angle corresponding to the maximum value of the harmonic voltage at the PCC point is used as the input of the voltage command, and the amplitude gain of the constructed GFM harmonic voltage source is increased, so that the harmonic voltage at the corresponding frequency at the PCC point is finally reduced to zero, and the amplitude gain corresponding to the harmonic voltage at the PCC point being reduced to zero is recorded; The non-GFM devices connected to the PCC point are aggregated and equivalent to a harmonic Norton model. Relying on Kirchhoff's voltage law and superposition theorem, combined with the fixed amplitude gain and the amplitude gain proportional relationship corresponding to the harmonic voltage at the PCC point being reduced to zero, that is, the harmonic voltage amplitude at the PCC point under two gains, the optimal compensation phase of the GFM harmonic voltage source is obtained.

[0009] Furthermore, the amplitude range of the virtual harmonic impedance is determined under the multiple constraints of the GFM stable domain and the modulation voltage limit; the method includes: determining the upper limit of the amplitude of the virtual harmonic impedance under the constraints of the GFM stable domain, and the constraints of the GFM stable domain are expressed by the following formula:

[0010] in, Z vir ( s ) represents the virtual impedance transfer function to be injected, H i ( s ) represents the current inner loop transfer function, C Represents the filter capacitor of the LCL filter, sIndicates the operation symbol of the discrete domain, M(s) indicates that the intermediate variable has no physical meaning, R Represents resistance, L 1 and L 2 represents the inductance parameters of the GFM converter filter. ω represents the grid angular frequency, h Indicates the harmonic order.

[0011] Furthermore, the amplitude range of the virtual harmonic impedance is determined under the multiple constraints of the GFM stability domain and the modulation voltage limit; the method also includes: determining the lower limit of the amplitude of the virtual harmonic impedance under the modulation voltage limit constraint, and the modulation voltage limit constraint is expressed by the following formula:

[0012] in, Z vir ( s ) is the virtual impedance transfer function to be injected, I oh is the GFM output harmonic current amplitude, u m is the current modulation voltage amplitude, M is the modulation voltage limiter, H i ( s ) represents the current inner loop transfer function, ω represents the grid angular frequency, h Indicates the harmonic order.

[0013] Furthermore, the optimal compensation phase is kept unchanged, and the optimal gain of the virtual harmonic impedance in the GFM stable domain is determined within the amplitude range of the virtual harmonic impedance; the method includes: keeping the optimal compensation phase unchanged, within the amplitude range of the virtual harmonic impedance, making the virtual impedance amplitude gain of the harmonic current frequency that needs to be suppressed iteratively increase from zero at a certain step size, and recording the harmonic voltage amplitude of the PCC point after each iteration, when the harmonic voltage amplitude of the PCC point has an inflection point, it is considered that the virtual impedance amplitude gain has achieved the optimal gain that should be obtained in theory, if the inflection point still does not appear after reaching the limit, the iteration is stopped, and it is considered that the virtual impedance amplitude gain has achieved the optimal gain of the virtual harmonic impedance in the stable domain.

[0014] Furthermore, the optimal compensation phase is expressed by the following formula:

[0015] in, θ hc represents the optimal compensation phase, θ gh Distorted Grid hSubharmonic voltage phase angle, Δ θ h is the phase angle error between the GFM voltage command and the actual constructed GFM harmonic voltage source, θ pcch For PCC points h Subharmonic voltage phase angle, θ h1 Indicates the input phase angle at which the hth harmonic voltage of the PCC takes its maximum value, θ oh Indicates GFM h Subharmonic output impedance phase angle.

[0016] Furthermore, the method for selecting the harmonic current frequency to be suppressed includes: determining the frequency and phase information of the harmonic voltage of the power grid according to the historical data of the low-voltage side of the transformer connected to the GFM power grid or the short-time recording analysis result, and selecting the harmonic current frequency to be suppressed.

[0017] A second aspect of the present invention provides a GFM control system for active harmonic suppression.

[0018] A GFM control system for active harmonic suppression, comprising: The phase compensation module is configured to: select the harmonic current frequency to be suppressed, superimpose a GFM harmonic voltage source with a fixed amplitude gain and a fixed phase angle in the voltage outer loop control instruction, and determine the optimal compensation phase according to the voltage vector optimization process and the PCC harmonic voltage amplitude curve in the iterative calculation; The virtual harmonic impedance optimal gain module is configured as follows: according to the acquired PCC voltage sampling data of the GFM access node and the GFM output current data, the harmonic voltage component at the harmonic current frequency that needs to be suppressed is separated to construct the virtual harmonic impedance at the harmonic current frequency that needs to be suppressed; under the multiple constraints of the GFM stable domain and the modulation voltage limit, the amplitude range of the virtual harmonic impedance is determined; keeping the optimal compensation phase unchanged, within the amplitude range of the virtual harmonic impedance, the optimal gain of the virtual harmonic impedance within the GFM stable domain is determined.

[0019] A third aspect of the present invention provides a computer-readable storage medium.

[0020] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the GFM control method for active harmonic suppression as described in the first aspect above.

[0021] A fourth aspect of the present invention provides a computer device.

[0022] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the GFM control method for active harmonic suppression as described in the first aspect above are implemented.

[0023] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a GFM control method, system, medium and equipment for active harmonic suppression, which breaks through the practical difficulty that passive impedance must be added on the basis of GFM control improvement in traditional methods, realizes the core function of GFM to independently improve grid-connected harmonic current, and can realize active support of harmonic current for any distorted power grid scenario, and has strong adaptability and versatility in high-proportion power electronic distribution system scenarios.

[0024] The present invention does not require the addition of any passive components on the low-voltage side of the transformer, nor does it require the addition of new sampling modules. Under the assumption that other disturbance sources connected to the PCC are aggregated into a harmonic Norton model, the optimal compensation voltage phase can be determined by superposition theorem and vector optimization, and then the optimal compensation voltage amplitude can be determined by observing the PCC harmonic voltage inflection point, thereby minimizing the impact of the distorted power grid on the GFM.

[0025] By analyzing the stability domain and modulation capability limit of the GFM control system, the present invention can clarify the frequency domain variation range of the GFM under multiple constraints, and reduce the harmonic frequency impedance to be suppressed to the minimum within this range, so that more harmonics can flow to the GFM under the PCC, so the harmonics flowing from the PCC to the power grid can be effectively reduced. In the current scenario of voltage distortion in the distribution system, the technical gap of GFM's complete independent and active participation in harmonic suppression at the grid connection point is filled. The method is more robust and stable than the traditional method, and is suitable for different types of new energy grid connection scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 is a flow chart of a GFM control method for active harmonic suppression in Embodiment 1 of the present invention; Figure 2 It is a flow chart of a grid harmonic voltage compensation control method based on GFM under the condition of no grid-side sampling in the first embodiment of the present invention; Figure 3 is an equivalent circuit diagram of a harmonic impedance equivalent model of a GFM converter under PCC in Embodiment 1 of the present invention; Figure 4is an equivalent circuit diagram of the GFM grid-connected system after considering the disturbance source in the first embodiment of the present invention; Figure 5 is an equivalent circuit diagram of a GFM grid-connected system after compensation in Embodiment 1 of the present invention; Figure 6 is an equivalent circuit diagram of a GFM grid-connected system after considering virtual impedance in the first embodiment of the present invention; Figure 7 It is a structural diagram of a GFM control system for active harmonic suppression in Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0029] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0031] It should be noted that the flowcharts and block diagrams in the accompanying drawings illustrate the possible implementation architecture, functions and operations of the methods and systems according to various embodiments of the present disclosure. It should be noted that each box in the flowchart or block diagram can represent a module, a program segment, or a part of a code, and the module, program segment, or a part of a code may include one or more executable instructions for implementing the logical functions specified in each embodiment. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, or they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the flowchart and / or block diagram, and the combination of boxes in the flowchart and / or block diagram can be implemented using a dedicated hardware-based system that performs a specified function or operation, or can be implemented using a combination of dedicated hardware and computer instructions.

[0032] Embodiment 1 like Figure 1As shown, this embodiment provides a GFM control method for active harmonic suppression. This embodiment uses the method applied to a server as an example for illustration. It is understandable that the method can also be applied to a terminal, and can also be applied to a system including a terminal and a server, and is implemented through the interaction between the terminal and the server. The server can be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network servers, cloud communications, middleware services, domain name services, security services CDN, and big data and artificial intelligence platforms. The terminal can be a smart phone, a tablet computer, a laptop computer, a desktop computer, etc., but is not limited thereto. The terminal and the server can be directly or indirectly connected via wired or wireless communication, which is not limited in this application. In this embodiment, the method includes the following steps: Step 1: Select the harmonic current frequency to be suppressed, superimpose a GFM harmonic voltage source with a fixed amplitude gain and a fixed phase angle in the voltage outer loop control instruction, and determine the optimal compensation phase based on the voltage vector optimization process and the PCC harmonic voltage amplitude curve in the iterative calculation; Step 2: Based on the PCC voltage sampling data and GFM output current data of the GFM access node, the harmonic voltage components at the harmonic current frequency that needs to be suppressed are separated to construct the virtual harmonic impedance at the harmonic current frequency that needs to be suppressed; under the multiple constraints of the GFM stable domain and the modulation voltage limit, the amplitude range of the virtual harmonic impedance is determined; keeping the optimal compensation phase unchanged, within the amplitude range of the virtual harmonic impedance, the optimal gain of the virtual harmonic impedance in the GFM stable domain is determined.

[0033] The present invention provides a GFM control method, system, medium and device for active harmonic suppression. A power grid harmonic voltage compensation control method based on GFM without grid-side sampling is adopted, other devices at the grid connection point are equivalent to the Norton harmonic model, model parameters are determined by harmonic voltage vector optimization and the optimal compensation phase is designed, and then a harmonic virtual impedance for weakening the GFM harmonic internal impedance is constructed. A harmonic virtual impedance setting method taking into account the control stability domain is adopted to determine the optimal compensation voltage amplitude. The two cooperate to effectively reduce the harmonic current content of the GFM grid connection point.

[0034] In some embodiments, Figure 2 As shown, the implementation steps of step 1 (using the power grid harmonic voltage compensation control method based on GFM without grid-side sampling) include: (1) Determine the harmonic current frequency that needs to be suppressed h , get the GFM converter filter inductance parameters L 1 and L2. Resistance parameters R (usually set to 0), so as to establish the harmonic impedance equivalent model of GFM converter under PCC (such as Figure 3 shown) As shown in formula (1): (1) in, θ oh For GFM h Subharmonic output impedance phase angle, Z oh For GFM h The absolute value of the subharmonic output impedance amplitude, ω is the grid angular frequency.

[0035] Among them, the harmonic impedance equivalent model is as follows Figure 3 As shown in the figure, Z gh Refers to the equivalent impedance of the power grid, U gh It refers to the equivalent voltage of the power grid. The harmonic impedance equivalent model can adopt the Thevenin harmonic model, etc.

[0036] (2) Add a fixed amplitude gain to the voltage outer loop control command K h , fixed phase angle θ h Voltage command signal , as shown in formula (2), keeping the amplitude gain fixed, so that the phase angle θ h Iterate from 0 degrees to 360 degrees with a certain step size.

[0037] (2) in, T s is the GFM control period, z is the operator symbol in the discrete domain.

[0038] (3) By comparing the PCC at different phase angles h Subharmonic voltage amplitude, find the input phase angle that makes the hth subharmonic voltage of PCC take the maximum value θ h1 .

[0039] (4) The remaining disturbance sources under PCC are equivalent to a harmonic Norton model. The GFM grid-connected system after considering the disturbance source is equivalent to: Figure 4 As shown (in the figure, Z Lh is the equivalent impedance of the PCC point load, I Lh is the PCC point load equivalent current), θ h1 As Input phase angle of the vector, adjust the amplitude gain K h Until PCC h The subharmonic voltage is reduced to zero, and the amplitude gain is K h1 .

[0040] (5) The optimal harmonic voltage compensation phase is calculated by the superposition theorem and Kirchhoff voltage theorem, as shown in formula (3): (3) in, θ gh Distorted Grid h Subharmonic voltage phase angle, Δ θ h is the phase angle error between the GFM voltage command and the actual constructed voltage source, θ pcch For PCC points h Subharmonic voltage phase angle.

[0041] (6) The optimal harmonic voltage compensation phase angle θ hc As Input phase angle of the vector, adjust the amplitude gain K h Until PCC h The subharmonic voltage amplitude has an inflection point, at which the amplitude gain is considered to be the optimal compensation voltage amplitude to match the distorted grid voltage.

[0042] The equivalent circuit diagram of the GFM grid-connected system after compensation is as follows: Figure 5 As shown in the figure, U gh The constructed GFM harmonic voltage source is consistent with the harmonic voltage in the grid voltage.

[0043] This embodiment is not limited by the GFM converter model, topology, control strategy and parameters. Without adding any sampling module, the influence of the voltage in the distorted grid on the GFM can be offset only by the harmonic voltage source constructed by the GFM converter itself. The method is simple and practical, and has strong adaptability and versatility in actual engineering.

[0044] In some embodiments, the implementation steps of step 2 (the harmonic virtual impedance setting method taking into account the control stability domain) include: According to the PCC voltage sampling signal, the quasi-resonant controller is used to decompose the component corresponding to the harmonic frequency that needs to be suppressed, multiply it by a certain gain and then add it to the modulated voltage signal to construct a virtual harmonic impedance at this frequency. The effect is to reduce the GFM output harmonic impedance, and the reduction amplitude is positively correlated with the multiplied gain; the equivalent circuit diagram of the GFM grid-connected system considering the virtual impedance is as follows: Figure 6 shown.

[0045] As a further technical limitation, in the GFM harmonic virtual impedance design process, the closed-loop transfer function and modulation voltage limit of the GFM control system are determined to identify the harmonic virtual impedance amplitude range that can be constructed within the stability domain of the GFM control system: The gain that characterizes the amplitude of the constructed virtual harmonic impedance should have upper and lower limits. The upper limit is determined according to the poles of the GFM closed-loop transfer function. A reasonable gain should ensure that there are no right-half-plane poles in the entire closed-loop system. The lower limit is constrained by the modulation voltage limit of the GFM control system, and its upper limit should be the maximum modulation ratio that can be operated.

[0046] On this basis, the optimal compensation phase obtained in the first scheme is kept unchanged, so that the virtual impedance amplitude gain of the corresponding frequency is Z h Iterate and increase the harmonic voltage amplitude at the PCC point after each iteration starting from zero with a certain step length. When an inflection point appears, it is considered Z h The optimal gain that should be obtained in theory is obtained. If no inflection point appears after reaching the limit, the iteration is stopped and it is considered Z h The best gain in the stable region is achieved.

[0047] Specifically, the constraint for determining the upper limit of the modulation voltage limit is: The stable range of the closed-loop pole is determined according to the Nyquist theorem, and the designed harmonic virtual impedance amplitude upper limit is constrained by this stable domain and should satisfy the range shown in equation (4): (4) in, Z vir ( s ) is the virtual impedance transfer function to be injected, H i ( s ) is the current inner loop transfer function, C is the filter capacitor of the LCL filter, s is the operation symbol in the discrete domain, and M(s) is an intermediate variable with no physical meaning.

[0048] Specifically, the constraint for determining the lower limit of the modulation voltage amplitude limit is: ( 5 ) in, I oh is the GFM output harmonic current amplitude, u m is the current modulation voltage amplitude, M The modulation voltage is limited.

[0049] By analyzing the stability domain and modulation capability limit of the GFM control system, the present invention can clarify the frequency domain variation range of the GFM under multiple constraints, and reduce the harmonic frequency impedance to be suppressed to the minimum within this range, so that more harmonics can flow to the GFM under the PCC, so the harmonics flowing from the PCC to the power grid can be effectively reduced. In the current scenario of voltage distortion in the distribution system, the technical gap of GFM's complete independent and active participation in harmonic suppression at the grid connection point is filled. The method is more robust and stable than the traditional method, and is suitable for different types of new energy grid connection scenarios.

[0050] Embodiment 2 like Figure 7 As shown, this embodiment provides a GFM control system for active harmonic suppression, including: The phase compensation module is configured to: select the harmonic current frequency to be suppressed, superimpose a GFM harmonic voltage source with a fixed amplitude gain and a fixed phase angle in the voltage outer loop control instruction, and determine the optimal compensation phase according to the voltage vector optimization process and the PCC harmonic voltage amplitude curve in the iterative calculation; The virtual harmonic impedance optimal gain module is configured as follows: according to the acquired PCC voltage sampling data of the GFM access node and the GFM output current data, the harmonic voltage component at the harmonic current frequency that needs to be suppressed is separated to construct the virtual harmonic impedance at the harmonic current frequency that needs to be suppressed; under the multiple constraints of the GFM stable domain and the modulation voltage limit, the amplitude range of the virtual harmonic impedance is determined; keeping the optimal compensation phase unchanged, within the amplitude range of the virtual harmonic impedance, the optimal gain of the virtual harmonic impedance within the GFM stable domain is determined.

[0051] In some embodiments, the phase compensation module is specifically configured as follows: Keep the fixed amplitude gain unchanged, so that the phase angle is iterated from 0 degrees to 360 degrees at a certain step size, and record the harmonic voltage amplitude of the PCC point after each phase angle change, and record the phase angle corresponding to the maximum value and the phase angle corresponding to the minimum value of the harmonic voltage at the PCC point during the vector optimization process; The phase angle corresponding to the maximum value of the harmonic voltage at the PCC point is used as the input of the voltage command, and the amplitude gain of the constructed GFM harmonic voltage source is increased, so that the harmonic voltage at the corresponding frequency at the PCC point is finally reduced to zero, and the amplitude gain corresponding to the harmonic voltage at the PCC point being reduced to zero is recorded; The non-GFM devices connected to the PCC point are aggregated and equivalent to a harmonic Norton model. Relying on Kirchhoff's voltage law and superposition theorem, combined with the fixed amplitude gain and the amplitude gain proportional relationship corresponding to the harmonic voltage at the PCC point being reduced to zero, that is, the harmonic voltage amplitude at the PCC point under two gains, the optimal compensation phase of the GFM harmonic voltage source is obtained.

[0052] In some embodiments, the virtual harmonic impedance optimal gain module is specifically configured to determine the upper limit of the amplitude of the virtual harmonic impedance under the constraint of the GFM stable domain, and the constraint of the GFM stable domain is expressed by the following formula:

[0053] in, Z vir ( s ) represents the virtual impedance transfer function to be injected, H i ( s ) represents the current inner loop transfer function, C Represents the filter capacitor of the LCL filter, s Indicates the operation symbol of the discrete domain, M(s) indicates that the intermediate variable has no physical meaning, R Represents resistance, L 1 and L 2 represents the inductance parameters of the GFM converter filter. ω represents the grid angular frequency, h Indicates the harmonic order.

[0054] In some embodiments, the virtual harmonic impedance optimal gain module is further configured to: determine the lower limit of the amplitude of the virtual harmonic impedance under the modulation voltage limit constraint, and the modulation voltage limit constraint is expressed by the following formula:

[0055] in, Z vir ( s ) is the virtual impedance transfer function to be injected, I oh is the GFM output harmonic current amplitude, u m is the current modulation voltage amplitude, M is the modulation voltage limiter, H i ( s ) represents the current inner loop transfer function, ω represents the grid angular frequency, h Indicates the harmonic order.

[0056] In some embodiments, the virtual harmonic impedance optimal gain module is specifically configured to: keep the optimal compensation phase unchanged, and within the amplitude range of the virtual harmonic impedance, iteratively increase the virtual impedance amplitude gain of the harmonic current frequency that needs to be suppressed from zero at a certain step size, and record the harmonic voltage amplitude of the PCC point after each iteration. When the harmonic voltage amplitude of the PCC point has an inflection point, it is considered that the virtual impedance amplitude gain has achieved the optimal gain that should be obtained in theory. If no inflection point appears after reaching the limit, the iteration is stopped, and it is considered that the virtual impedance amplitude gain has achieved the optimal gain of the virtual harmonic impedance in the stable domain.

[0057] Furthermore, the optimal compensation phase is expressed by the following formula:

[0058] in, θ hc represents the optimal compensation phase, θ gh Distorted Grid h Subharmonic voltage phase angle, Δ θ h is the phase angle error between the GFM voltage command and the actual constructed GFM harmonic voltage source, θ pcch For PCC points h Subharmonic voltage phase angle, θ h1 Indicates the input phase angle at which the hth harmonic voltage of the PCC takes its maximum value, θ oh Indicates GFM h Subharmonic output impedance phase angle.

[0059] In some embodiments, the phase compensation module is further configured to: select the harmonic current frequency that needs to be suppressed, the method includes: determining the frequency and phase information of the grid harmonic voltage based on the historical data of the low-voltage side of the transformer connected to the GFM grid or the short-time recording analysis results, and selecting the harmonic current frequency to be suppressed.

[0060] The present invention can effectively reduce the harmonic current content of the GFM connected to the power grid without adding new sampling or passive impedance, and has good economy and engineering promotion value.

[0061] Embodiment 3 This embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the steps of the GFM control method for active harmonic suppression as described in the first embodiment are implemented.

[0062] Embodiment 4 This embodiment provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps in the GFM control method for active harmonic suppression as described in the first embodiment are implemented.

[0063] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of hardware embodiments, software embodiments, or embodiments combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) containing computer-usable program code.

[0064] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks 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 produce 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.

[0065] 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 comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0066] 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.

[0067] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A GFM control method for active harmonic suppression, characterized in that: include: Select the harmonic current frequency that needs to be suppressed, superimpose a GFM harmonic voltage source with a fixed amplitude gain and a fixed phase angle in the voltage outer loop control instruction, and determine the optimal compensation phase based on the voltage vector optimization process and the PCC harmonic voltage amplitude curve in the iterative calculation; According to the PCC voltage sampling data and GFM output current data of the GFM access node, the harmonic voltage components at the harmonic current frequency that needs to be suppressed are separated to construct the virtual harmonic impedance at the harmonic current frequency that needs to be suppressed; under the multiple constraints of the GFM stable domain and the modulation voltage limit, the amplitude range of the virtual harmonic impedance is determined; keeping the optimal compensation phase unchanged, the optimal gain of the virtual harmonic impedance in the GFM stable domain is determined within the amplitude range of the virtual harmonic impedance.

2. The GFM control method for active harmonic suppression according to claim 1, characterized in that: The method of determining the optimal compensation phase according to the compensation voltage vector optimization process and the PCC harmonic voltage amplitude curve in the iterative calculation includes: Keep the fixed amplitude gain unchanged, so that the phase angle is iterated from 0 degrees to 360 degrees at a certain step size, and record the harmonic voltage amplitude of the PCC point after each phase angle change, and record the phase angle corresponding to the maximum value and the phase angle corresponding to the minimum value of the harmonic voltage at the PCC point during the vector optimization process; The phase angle corresponding to the maximum value of the harmonic voltage at the PCC point is used as the input of the voltage command, and the amplitude gain of the constructed GFM harmonic voltage source is increased, so that the harmonic voltage at the corresponding frequency at the PCC point is finally reduced to zero, and the amplitude gain corresponding to the harmonic voltage at the PCC point being reduced to zero is recorded; The non-GFM devices connected to the PCC point are aggregated and equivalent to a harmonic Norton model. Relying on Kirchhoff's voltage law and superposition theorem, combined with the fixed amplitude gain and the amplitude gain proportional relationship corresponding to the harmonic voltage at the PCC point being reduced to zero, that is, the harmonic voltage amplitude at the PCC point under two gains, the optimal compensation phase of the GFM harmonic voltage source is obtained.

3. The GFM control method for active harmonic suppression according to claim 1, characterized in that: The method includes determining the amplitude range of the virtual harmonic impedance under the multiple constraints of the GFM stable domain and the modulation voltage limit. The method includes: determining the upper limit of the amplitude of the virtual harmonic impedance under the constraints of the GFM stable domain, and the constraints of the GFM stable domain are expressed by the following formula: in, Z vir ( s ) represents the virtual impedance transfer function to be injected, H i ( s ) represents the current inner loop transfer function, C Represents the filter capacitor of the LCL filter, s Indicates the operation symbol of the discrete domain, M(s) indicates that the intermediate variable has no physical meaning, R Represents resistance, L 1 and L 2 represents the inductance parameters of the GFM converter filter. ω represents the grid angular frequency, h Indicates the harmonic order.

4. The GFM control method for active harmonic suppression according to claim 1, characterized in that: The method further comprises: determining the amplitude range of the virtual harmonic impedance under the multiple constraints of the GFM stability domain and the modulation voltage limit; and determining the lower limit of the amplitude of the virtual harmonic impedance under the modulation voltage limit constraint, wherein the modulation voltage limit constraint is expressed by the following formula: in, Z vir ( s ) is the virtual impedance transfer function to be injected, I oh is the GFM output harmonic current amplitude, u m is the current modulation voltage amplitude, M is the modulation voltage limiter, H i ( s ) represents the current inner loop transfer function, ω represents the grid angular frequency, h Indicates the harmonic order.

5. The GFM control method for active harmonic suppression according to claim 1, characterized in that: The optimal compensation phase is kept unchanged, and the optimal gain of the virtual harmonic impedance in the GFM stable domain is determined within the amplitude range of the virtual harmonic impedance; the method includes: keeping the optimal compensation phase unchanged, and within the amplitude range of the virtual harmonic impedance, iteratively increasing the virtual impedance amplitude gain of the harmonic current frequency that needs to be suppressed from zero at a certain step size, and recording the harmonic voltage amplitude of the PCC point after each iteration. When the harmonic voltage amplitude of the PCC point has an inflection point, it is considered that the virtual impedance amplitude gain has achieved the optimal gain that should be obtained in theory. If the inflection point still does not appear after reaching the limit, the iteration is stopped, and it is considered that the virtual impedance amplitude gain has achieved the optimal gain of the virtual harmonic impedance in the stable domain.

6. The GFM control method for active harmonic suppression according to claim 1, characterized in that: The optimal compensation phase is expressed by the following formula: in, θ hc represents the optimal compensation phase, θ gh Distorted Grid h Subharmonic voltage phase angle, Δ θ h is the phase angle error between the GFM voltage command and the actual constructed GFM harmonic voltage source, θ pcch For PCC points h Subharmonic voltage phase angle, θ h1 Indicates the input phase angle at which the hth harmonic voltage of the PCC takes its maximum value, θ oh Indicates GFM h Subharmonic output impedance phase angle.

7. The GFM control method for active harmonic suppression according to claim 1, characterized in that: The method for selecting the harmonic current frequency to be suppressed includes: determining the frequency and phase information of the harmonic voltage of the power grid according to the historical data of the low-voltage side of the transformer connected to the GFM power grid or the short-time recording analysis result, and selecting the harmonic current frequency to be suppressed.

8. A GFM control system for active harmonic suppression, characterized in that: include: The phase compensation module is configured to: select the harmonic current frequency to be suppressed, superimpose a GFM harmonic voltage source with a fixed amplitude gain and a fixed phase angle in the voltage outer loop control instruction, and determine the optimal compensation phase according to the voltage vector optimization process and the PCC harmonic voltage amplitude curve in the iterative calculation; The virtual harmonic impedance optimal gain module is configured as follows: according to the acquired PCC voltage sampling data of the GFM access node and the GFM output current data, the harmonic voltage component at the harmonic current frequency that needs to be suppressed is separated to construct the virtual harmonic impedance at the harmonic current frequency that needs to be suppressed; under the multiple constraints of the GFM stable domain and the modulation voltage limit, the amplitude range of the virtual harmonic impedance is determined; keeping the optimal compensation phase unchanged, within the amplitude range of the virtual harmonic impedance, the optimal gain of the virtual harmonic impedance within the GFM stable domain is determined.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the GFM control method for active harmonic suppression according to any one of claims 1 to 7 are implemented.

10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the GFM control method for active harmonic suppression according to any one of claims 1 to 7 are implemented.

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