Grid-connected harmonic suppression method and system based on converter compensation vector iterative control

Abstract

The present invention belongs to the technical field of power quality management and provides a grid-connected harmonic suppression method and system based on converter compensation vector iterative control, comprising: generating a converter harmonic compensation voltage based on phase angle transformation of a grid-connected converter; performing compensation vector iterative control on the generated harmonic compensation voltage to obtain an optimal phase angle of the compensation voltage; increasing the harmonic compensation voltage amplitude and judging the direction of the harmonic current based on the obtained optimal phase angle of the compensation voltage; suppressing the grid-connected harmonic current based on the harmonic compensation voltage amplitude when the harmonic current direction changes, thereby completing the grid-connected harmonic suppression based on converter compensation vector iterative control.

Description

Technical Field

[0001] The present invention belongs to the technical field of power quality management, and in particular relates to a method and system for suppressing grid-connected harmonics based on iterative control of a converter compensation vector. 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] Renewable energy, driven by its green, clean, and resource-rich nature, has maintained rapid growth in recent years, with newly installed capacity reaching record highs. Unlike traditional fossil fuels, renewable energy sources are connected to the power system via low-inertia, fast-response converters. Furthermore, renewable energy power stations are mostly located in remote areas, and long-distance transmission has led to the power system gradually adopting the characteristics of a weak grid. In this weak grid environment, grid-side voltage distortion is becoming increasingly severe, and the penetration of nonlinear loads is gradually increasing. This degrades the quality of the connected current, resulting in poor grid immunity and posing a potential threat to the grid's stable operation and power quality.

[0004] Most new energy grid-connected converters employ grid-following control. To enable grid-following converters to actively suppress harmonic currents, harmonic current control compensation methods are often employed. Using Fourier transforms and detection methods based on instantaneous active and reactive power theory, harmonic current commands are ensured to have the same amplitude and phase as the nonlinear load harmonic currents, enabling the converter to absorb the load harmonic currents. Compared to the current source characteristics of grid-following converters, grid-connecting converters simulate the rotor dynamics of synchronous generators to regulate voltage amplitude and frequency, exhibiting voltage source characteristics. Due to the voltage source control mode of grid-connecting converters, the compensated components are equivalent to harmonic voltage sources rather than harmonic current sources, making it difficult to offset the harmonic currents of nonlinear loads. However, compensating harmonic voltage sources can offset the harmonics generated by grid-side background harmonics in the converter.

[0005] Therefore, it is urgent to study how to effectively reduce the harmonic current generated by the grid-side distorted voltage on the grid converter to improve the current quality at the grid connection point. Summary of the Invention

[0006] To solve the above problems, the present invention proposes a grid-connected harmonic suppression method and system based on converter compensation vector iterative control. By performing vector iteration on the amplitude and phase of the converter compensation voltage, the harmonics emitted by the grid-connected converter under the distorted power grid are reduced, and the grid-connected current waveform can be improved in a short time. At the same time, real-time response is provided when the grid conditions change, and the phase and amplitude of the compensation voltage are automatically adjusted, which significantly suppresses the harmonic content of the grid connection point and effectively reduces the impact of the grid background harmonics on the grid current harmonics.

[0007] According to some embodiments, a first solution of the present invention provides a method for suppressing grid-connected harmonics based on iterative control of a converter compensation vector, which adopts the following technical solutions:

[0008] A grid-connected harmonic suppression method based on converter compensation vector iterative control, comprising:

[0009] Generate converter harmonic compensation voltage based on phase angle transformation of grid-type converter;

[0010] Perform compensation vector iterative control on the generated harmonic compensation voltage to obtain the optimal phase angle of the compensation voltage;

[0011] According to the obtained optimal phase angle of the compensation voltage, the amplitude of the harmonic compensation voltage is increased and the direction of the harmonic current is determined;

[0012] The grid-connected harmonic current is suppressed according to the harmonic compensation voltage amplitude when the harmonic current direction changes, thereby completing the grid-connected harmonic suppression based on the iterative control of the converter compensation vector.

[0013] As a further technical limitation, in the process of generating the converter harmonic compensation voltage based on the phase angle transformation of the meshed converter, considering that the voltage loop of the meshed converter is controlled in the dq coordinate system, the phase angle constructed by the meshed converter is used to perform phase angle transformation on the harmonic compensation voltage to generate the harmonic compensation voltage component in the dq coordinate system, and the generated harmonic compensation voltage component is superimposed on the input of the voltage loop of the meshed converter to obtain the converter harmonic compensation voltage.

[0014] As a further technical limitation, in the process of iterative control of the compensation vector, the compensation voltage phase angle is optimized based on the harmonic compensation voltage with a fixed amplitude and a fixed step length phase angle, and the compensation voltage phase angle is iteratively corrected to seek the direction of maximum drop in the harmonic voltage at the grid connection point, and the obtained maximum drop direction is used as the optimal phase angle, that is, the compensation voltage phase angle.

[0015] Furthermore, when the grid-side harmonic compensation voltage is not added, the grid-connected point harmonic voltage for ;in, 、 、 They are load current, grid current and grid voltage respectively; 、 They are the equivalent output impedance of the grid impedance and the equivalent output impedance of the converter; after adding the grid-side harmonic compensation voltage, the grid-connected point harmonic voltage for ;in, is the grid-side harmonic compensation voltage; the optimal phase angle of the compensation voltage is when the grid-connected point harmonic voltage is most sensitive to the change in the compensation voltage amplitude, that is, the grid-connected point harmonic voltage drops the fastest, and the optimal phase angle of the compensation voltage is for ;in, is the amount of change in compensation voltage.

[0016] It should be noted that in the process where the harmonic voltage at the grid connection point decreases at the fastest rate, the phase angle of the compensation voltage is iterated from 0 rad to 360 rad with a fixed step length, and the harmonic voltage amplitude at the grid connection point before and after the compensation voltage is added at each iterative phase angle is recorded. The optimal phase angle is the iterative phase angle corresponding to the maximum change in the harmonic voltage amplitude at the grid connection point.

[0017] As a further technical limitation, during the iterative control of the compensation vector, the harmonic voltage at the grid connection point is greater than the harmonic voltage output by the converter, and the direction of the harmonic current is from the grid connection point to the converter; during the increase in the amplitude of the harmonic compensation voltage, the converter outputs a reverse harmonic current, that is, the current direction of the converter output is the same as the grid harmonic current, and the harmonic voltage at the grid connection point approaches the harmonic voltage of the grid. When the harmonic voltage at the grid connection point is consistent with the harmonic voltage of the grid, the direction of the harmonic current changes, the increase in the amplitude of the harmonic compensation voltage stops, and the suppression of the grid harmonic current is completed.

[0018] As a further technical limitation, the grid-connected harmonic suppression method based on converter compensation vector iterative control also includes multi-order compensation voltage vector iterative control, in which the multi-order compensation voltage vector iterative control is performed step by step from low order to high order until the suppression of the grid-connected harmonic current is completed.

[0019] It should be noted that the compensation voltages for harmonics of different orders are all iteratively searched for the optimal phase angle by fixing the compensation voltage amplitude and changing the compensation phase, and then gradually increasing the compensation voltage amplitude until the harmonic current reverses, thereby achieving the effect of suppressing the corresponding harmonic current. Adding harmonic compensation voltage will affect the magnitude of the modulation voltage. If the compensation amplitude is too large, it may cause the modulation voltage to exceed the range, affecting the normal operation of the switching tube and reducing the working efficiency of the system. Multi-order harmonics such as 5th, 7th, and 11th are carried out gradually. After the 5th harmonic compensation voltage is added, the modulation voltage amplitude will increase accordingly. Therefore, when determining the 7th harmonic compensation voltage amplitude, it is necessary to consider the limitation of the modulation voltage amplitude after adding the 5th harmonic compensation voltage. The limit is , is the DC side voltage amplitude.

[0020] According to some embodiments, a second solution of the present invention provides a grid-connected harmonic suppression system based on iterative control of a converter compensation vector, which adopts the following technical solutions:

[0021] A grid-connected harmonic suppression system based on converter compensation vector iterative control, comprising:

[0022] an acquisition module configured to generate a converter harmonic compensation voltage based on a phase angle transformation of a grid-type converter;

[0023] an optimization module configured to perform compensation vector iterative control on the generated harmonic compensation voltage to obtain an optimal phase angle of the compensation voltage;

[0024] a judgment module configured to increase the harmonic compensation voltage amplitude and judge the harmonic current direction according to the obtained optimal phase angle of the compensation voltage;

[0025] The suppression module is configured to suppress the grid-connected harmonic current according to the amplitude of the harmonic compensation voltage when the direction of the harmonic current changes, thereby completing the grid-connected harmonic suppression based on the iterative control of the converter compensation vector.

[0026] According to some embodiments, a third solution of the present invention provides a computer-readable storage medium, which adopts the following technical solution:

[0027] A computer-readable storage medium stores a program thereon, which, when executed by a processor, implements the steps of the grid-connected harmonic suppression method based on iterative control of a converter compensation vector as described in the first embodiment of the present invention.

[0028] According to some embodiments, a fourth solution of the present invention provides an electronic device, which adopts the following technical solution:

[0029] An electronic device includes a memory, a processor, and a program stored in the memory and running on the processor. When the processor executes the program, it implements the steps of the grid-connected harmonic suppression method based on converter compensation vector iterative control as described in the first embodiment of the present invention.

[0030] According to some embodiments, a fifth solution of the present invention provides a computer program product, which adopts the following technical solution:

[0031] A computer program product includes software code, wherein the program in the software code executes the steps of the grid-connected harmonic suppression method based on converter compensation vector iterative control as described in the first embodiment of the present invention.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention reduces the harmonics emitted by the grid-connected converter under the distorted power grid by performing vector iteration on the amplitude and phase of the converter compensation voltage, and can improve the grid-connected current waveform in a short time. At the same time, it provides real-time response when the grid conditions change, automatically adjusts the phase and amplitude of the compensation voltage, significantly suppresses the harmonic content of the grid connection point, and effectively reduces the impact of the grid background harmonics on the grid current harmonics. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings constituting a part of the specification of this embodiment are used to provide a further understanding of this embodiment. The schematic embodiments and descriptions of this embodiment are used to explain this embodiment and do not constitute an improper limitation on this embodiment.

[0035] Figure 1 Flowchart of a method for suppressing grid-connected harmonics based on iterative control of a converter compensation vector in Embodiment 1 of the present invention;

[0036] Figure 2 Schematic diagram of detailed steps of a method for suppressing grid-connected harmonics based on iterative control of a converter compensation vector in Embodiment 1 of the present invention;

[0037] Figure 3 Schematic diagram of the topological structure of the grid-type converter in the first embodiment of the present invention;

[0038] Figure 4 This is a control block diagram of the iterative control of the converter compensation vector in the first embodiment of the present invention;

[0039] Figure 5 This is a structural block diagram of a grid-connected harmonic suppression system based on iterative control of a converter compensation vector in a second embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0042] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0043] In the absence of conflict, the embodiments of the present invention and the features thereof may be combined with each other.

[0044] Example 1

[0045] The first embodiment of the present invention introduces a method for suppressing grid-connected harmonics based on iterative control of a converter compensation vector.

[0046] like Figure 1 A grid-connected harmonic suppression method based on converter compensation vector iterative control is shown, comprising:

[0047] Generate converter harmonic compensation voltage based on phase angle transformation of grid-type converter;

[0048] Perform compensation vector iterative control on the generated harmonic compensation voltage to obtain the optimal phase angle of the compensation voltage;

[0049] According to the obtained optimal phase angle of the compensation voltage, the amplitude of the harmonic compensation voltage is increased and the direction of the harmonic current is determined;

[0050] The grid-connected harmonic current is suppressed according to the harmonic compensation voltage amplitude when the harmonic current direction changes, thereby completing the grid-connected harmonic suppression based on the iterative control of the converter compensation vector.

[0051] This embodiment provides real-time response when grid conditions change, automatically adjusts the phase and amplitude of the compensation voltage, and has a good suppression effect on the grid-connected harmonic current generated by the background harmonics of the grid, thereby improving the versatility of the suppression method and providing reliable technical support for large-scale new energy access. Figure 2 Expand the introduction of detailed steps for grid-connected harmonic suppression:

[0052] Constructing a fifth-order compensation voltage, that is, introducing a fifth-order compensation voltage into the reference voltage input of the voltage loop to reduce the harmonic components emitted by the grid converter under the distorted grid;

[0053] Identify the optimal phase angle of the compensation voltage. This involves performing vector iterative control using a compensation voltage instruction with a fixed amplitude and variable step-length phase angle to find the compensation voltage phase angle that causes the harmonic voltage at the grid connection point to drop fastest, thereby determining the optimal compensation voltage phase angle.

[0054] Determine the compensation voltage amplitude, that is, based on the optimal compensation voltage phase angle, gradually increase the harmonic compensation voltage amplitude, determine the harmonic flow direction by analyzing the harmonic relationship between the modulation voltage and the grid connection point voltage, and lock the compensation voltage amplitude when the harmonic flow direction changes;

[0055] Multi-order compensation voltage vector iterative control, that is, after determining the phase angle and amplitude of the 5th compensation voltage, a similar vector iterative control strategy is used to construct the 7th, 11th, and 13th harmonic compensation voltages in sequence, thereby achieving simultaneous suppression of multi-order grid-connected harmonic currents.

[0056] In this embodiment, the fifth harmonic voltage is used as Figure 3 The phase angle of the grid-type converter shown in the figure is transformed. Considering that the grid-type converter voltage loop is controlled in the dq coordinate system, the phase angle of the grid-type converter is used to transform the harmonic compensation voltage, generating a harmonic compensation voltage component in the dq coordinate system. The generated harmonic compensation voltage component is added to the input of the grid-type converter voltage loop to obtain the converter harmonic compensation voltage. The resulting harmonic compensation voltage is then added to the input of the voltage outer loop to increase the reference voltage by the corresponding harmonic content. By adding a compensation voltage corresponding to the grid background harmonics, the impact of the grid background harmonics on the grid-connected current is offset, the current quality at the grid connection point is optimized, and the grid-type converter's active harmonic suppression capability is enhanced.

[0057] This embodiment combines Figure 4 Perform iterative control of the converter compensation vector. Specifically: first, optimize the constructed compensation voltage phase angle through a compensation voltage instruction with a fixed amplitude and variable step length phase angle, iteratively correct the compensation voltage phase angle, seek the direction of maximum harmonic voltage drop at the grid connection point, and lock the optimal phase angle as the compensation voltage phase angle.

[0058] It should be noted that, in this embodiment, ,in, is the harmonic order, is the fundamental angular frequency.

[0059] In this embodiment, when the grid-side harmonic compensation voltage is not added, the grid-connected point harmonic voltage for ;in, 、 、 They are load current, grid current and grid voltage respectively; 、 They are the equivalent output impedance of the grid impedance and the equivalent output impedance of the converter; after adding the grid-side harmonic compensation voltage, the grid-connected point harmonic voltage for ;in, The optimal compensation voltage phase angle is sought to make the harmonic voltage at the grid connection point most sensitive to the change in the compensation voltage amplitude, that is, the harmonic voltage at the grid connection point decreases at the fastest rate and the optimal compensation voltage phase angle is obtained. for ;in, is the amount of change in compensation voltage.

[0060] It should be noted that in the process where the harmonic voltage at the grid connection point decreases at the fastest rate, the phase angle of the compensation voltage is iterated from 0 rad to 360 rad with a fixed step length, and the harmonic voltage amplitude at the grid connection point before and after the compensation voltage is added at each iterative phase angle is recorded. The optimal phase angle is the iterative phase angle corresponding to the maximum change in the harmonic voltage amplitude at the grid connection point.

[0061] Since the voltage reference command output by the power controller only contains the amplitude and phase information of the fundamental voltage, the grid-connected point harmonic voltage is higher than the converter output harmonic voltage. At this time, the harmonic current flows from the grid-connected point to the converter. The relationship between the grid-connected point harmonic voltage and the harmonic voltage in the converter modulation signal is: ;in, u PCC ( s ) is the grid connection point voltage, u o ( s ) is the converter output voltage, u mod ( s ) is the modulation signal, i o ( s ) is the converter output current.

[0062] As the compensation voltage amplitude gradually increases, the converter outputs harmonic current in the reverse direction. At this time, the relationship between the harmonic voltage at the grid connection point and the harmonic voltage in the converter modulation signal is: .

[0063] Since the output harmonic current and the grid-connected harmonic current flow direction change synchronously, during this process, the grid-connected point harmonic voltage gradually approaches the grid harmonic voltage. By collecting and analyzing the harmonic relationship between the modulation voltage, output current and grid-connected voltage, the moment of harmonic flow change is determined. According to their harmonic relationship, the variable HFD that represents the harmonic flow direction is defined as .

[0064] According to the iterative results of the harmonic compensation voltage phase angle vector, the harmonic compensation voltage amplitude is gradually increased. When the inflection point of the harmonic relationship change is found, the vector iteration process is terminated, the amplitude at the inflection point is obtained and locked as the harmonic compensation voltage amplitude; the final determination of the harmonic voltage compensation amplitude needs to be completed in successive iterations, that is, ;in, u add0 is the base value for starting iteration, Δ u addh is the iteration step length, K T is the number of iterations, U n is the rated voltage amplitude.

[0065] The addition of compensation voltage will affect the magnitude of modulation voltage. If the compensation amplitude is too large, the modulation voltage may exceed the range, affecting the normal operation of the switch tube and reducing the working efficiency of the system. Therefore, the selection of harmonic compensation voltage amplitude also needs to consider the limitation of modulation voltage to ensure that the compensation voltage does not cause the modulation voltage to exceed the safe range, that is, the compensation voltage should meet ;in, U dc is the DC side output voltage amplitude, U modh For the modulation voltage h Subharmonic components.

[0066] In this embodiment, a fifth-order harmonic compensation voltage command with a fixed amplitude and variable step phase is used for vector iterative control to suppress the fifth harmonic. During this process, the optimal compensation phase is determined by seeking the direction in which the compensation voltage causes the harmonic voltage at the grid connection point to decrease at the fastest rate. The compensation voltage amplitude is then gradually increased until the fifth-order harmonic current reverses, achieving the desired effect of suppressing the grid-connected fifth-order harmonic current. The iterative process is then terminated.

[0067] Since lower-order harmonics contain more content than higher-order harmonics, the vector iterative control strategy starts from lower-order harmonic compensation. At the same time, the harmonic compensation voltage amplitude is limited by the global modulation voltage. Therefore, the higher-order harmonic compensation voltage amplitude needs to be adjusted based on the lower-order compensation.

[0068] A similar vector iterative control strategy is employed for the seventh-order compensation voltage. This same vector iterative control strategy employs a fixed-amplitude, variable-step-phase compensation voltage command to ensure timely adjustment of the compensation signal to system changes. However, due to improvements to the fifth-order harmonic control strategy, the modulation voltage amplitude may increase. Therefore, although the vector iterative control strategy of the 7th compensation voltage remains unchanged, after the lower-order harmonic compensation voltage is added, the range of the amplitude setting of the higher-order harmonic compensation voltage is reduced, and the theoretical optimal value may not be reached, resulting in the high-order harmonic suppression effect being weaker than that of separate compensation. However, the adjustment of its related parameters needs to take into account the impact of the construction of the 5th compensation voltage to avoid mutual interference of parameters in the system, ensure the simultaneous suppression of multi-order harmonics, and perform step-by-step compensation (5th → 7th → 11th → 13th) according to the size of the harmonic content of the grid-connected point current. A certain order harmonic compensation voltage is added to monitor the modulation voltage amplitude, and the adjustment space of the next order harmonic compensation voltage amplitude is updated to ensure that the addition of subsequent order harmonic compensation voltages will not cause the modulation voltage amplitude to exceed the limit; the same applies to other harmonics.

[0069] This embodiment reduces the harmonics emitted by the grid-connected converter in a distorted grid by performing vector iteration on the amplitude and phase of the converter compensation voltage, thereby improving the grid-connected current waveform in a short period of time. At the same time, it provides real-time response when grid conditions change, automatically adjusts the phase and amplitude of the compensation voltage, significantly suppresses the harmonic content at the grid connection point, and effectively reduces the impact of grid background harmonics on grid current harmonics.

[0070] Example 2

[0071] The second embodiment of the present invention introduces a grid-connected harmonic suppression system based on converter compensation vector iterative control.

[0072] like Figure 5 A grid-connected harmonic suppression system based on converter compensation vector iterative control is shown, comprising:

[0073] an acquisition module configured to generate a converter harmonic compensation voltage based on a phase angle transformation of a grid-type converter;

[0074] an optimization module configured to perform compensation vector iterative control on the generated harmonic compensation voltage to obtain an optimal phase angle of the compensation voltage;

[0075] a judgment module configured to increase the harmonic compensation voltage amplitude and judge the harmonic current direction according to the obtained optimal phase angle of the compensation voltage;

[0076] The suppression module is configured to suppress the grid-connected harmonic current according to the amplitude of the harmonic compensation voltage when the direction of the harmonic current changes, thereby completing the grid-connected harmonic suppression based on the iterative control of the converter compensation vector.

[0077] The detailed steps are the same as those of the grid-connected harmonic suppression method based on iterative control of the converter compensation vector provided in Example 1, and are not repeated here.

[0078] Example 3

[0079] A third embodiment of the present invention provides a computer-readable storage medium.

[0080] A computer-readable storage medium stores a program thereon, which, when executed by a processor, implements the steps of the grid-connected harmonic suppression method based on converter compensation vector iterative control as described in the first embodiment of the present invention.

[0081] The detailed steps are the same as those of the grid-connected harmonic suppression method based on iterative control of the converter compensation vector provided in Example 1, and are not repeated here.

[0082] Example 4

[0083] A fourth embodiment of the present invention provides an electronic device.

[0084] An electronic device includes a memory, a processor, and a program stored in the memory and running on the processor. When the processor executes the program, it implements the steps of the grid-connected harmonic suppression method based on converter compensation vector iterative control as described in Example 1 of the present invention.

[0085] The detailed steps are the same as those of the grid-connected harmonic suppression method based on iterative control of the converter compensation vector provided in Example 1, and are not repeated here.

[0086] Example 5

[0087] A fifth embodiment of the present invention provides a computer program product.

[0088] A computer program product includes software code, wherein the program in the software code executes the steps of the grid-connected harmonic suppression method based on converter compensation vector iterative control as described in the first embodiment of the present invention.

[0089] The detailed steps are the same as those of the grid-connected harmonic suppression method based on iterative control of the converter compensation vector provided in Example 1, and are not repeated here.

[0090] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. 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 drives, CD-ROMs, optical storage devices, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention may be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0091] 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 flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. 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.

[0092] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work 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 The function specified in one or more boxes.

[0093] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0094] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0095] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

[0096] The above description is merely a preferred embodiment of this embodiment and is not intended to limit this embodiment. Those skilled in the art will readily appreciate that this embodiment may be modified and varied in various ways. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this embodiment shall be within the scope of protection of this embodiment.

Claims

1. A method for suppressing grid-connected harmonics based on iterative control of converter compensation vector, characterized in that: include: Generate converter harmonic compensation voltage based on phase angle transformation of grid-type converter; Perform compensation vector iterative control on the generated harmonic compensation voltage to obtain the optimal phase angle of the compensation voltage; According to the obtained optimal phase angle of the compensation voltage, the amplitude of the harmonic compensation voltage is increased and the direction of the harmonic current is determined; The grid-connected harmonic current is suppressed by the harmonic compensation voltage amplitude when the harmonic current direction changes, completing the grid-connected harmonic suppression based on the iterative control of the converter compensation vector; Among them, the optimal phase angle of the compensation voltage is when the harmonic voltage at the grid connection point is most sensitive to the change in the compensation voltage amplitude, that is, the harmonic voltage at the grid connection point drops the fastest, and the optimal phase angle of the compensation voltage is for: ； in, is the change in compensation voltage; is the harmonic voltage at the grid connection point; The harmonic relationship between the modulation voltage, output current and grid-connected voltage is collected and analyzed to determine the moment when the harmonic flow direction changes. Based on their harmonic relationship, the variable HFD that characterizes the harmonic flow direction is defined as: ； in, is the grid connection point voltage, is the modulation signal, is the converter output current, is the harmonic order, is the fundamental angular frequency.

2. A method for suppressing grid-connected harmonics based on iterative control of converter compensation vectors as claimed in claim 1, characterized in that: In the process of generating the converter harmonic compensation voltage based on the phase angle transformation of the mesh converter, considering that the voltage loop of the mesh converter is controlled in the dq coordinate system, the phase angle constructed by the mesh converter is used to transform the harmonic compensation voltage to generate the harmonic compensation voltage component in the dq coordinate system. The generated harmonic compensation voltage component is superimposed on the input of the voltage loop of the mesh converter to obtain the converter harmonic compensation voltage.

3. A method for suppressing grid-connected harmonics based on iterative control of converter compensation vectors as claimed in claim 1, characterized in that: During the iterative control of the compensation vector, the compensation voltage phase angle is optimized based on the harmonic compensation voltage with fixed amplitude and variable step length phase angle, and the compensation voltage phase angle is iteratively corrected to seek the direction in which the harmonic voltage at the grid connection point drops to the maximum. The obtained direction of the maximum drop is used as the optimal phase angle, i.e., the compensation voltage phase angle.

4. A method for suppressing grid-connected harmonics based on iterative control of converter compensation vectors as claimed in claim 3, characterized in that: When the grid-side harmonic compensation voltage is not added, the grid-connected point harmonic voltage for ;in, 、 、 They are load current, grid current and grid voltage respectively; 、 They are the equivalent output impedance of the grid impedance and the equivalent output impedance of the converter; after adding the grid-side harmonic compensation voltage, the grid-connected point harmonic voltage for ;in, It is the grid-side harmonic compensation voltage.

5. A method for suppressing grid-connected harmonics based on iterative control of converter compensation vectors as claimed in claim 1, characterized in that: During the compensation vector iterative control process, the grid-connected point harmonic voltage is greater than the converter output harmonic voltage, and the direction of the harmonic current is from the grid-connected point to the converter. During the increase in the harmonic compensation voltage amplitude, the converter outputs a reverse harmonic current, that is, the current direction of the converter output is in the same direction as the grid-connected harmonic current, and the grid-connected point harmonic voltage approaches the grid harmonic voltage. When the grid-connected point harmonic voltage is consistent with the grid harmonic voltage, the harmonic current direction changes, the increase in the harmonic compensation voltage amplitude stops, and the grid-connected harmonic current is suppressed.

6. A method for suppressing grid-connected harmonics based on iterative control of converter compensation vectors as claimed in claim 1, characterized in that: It also includes multi-order compensation voltage vector iterative control, in which the multi-order compensation voltage vector iterative control is performed step by step from low order to high order until the suppression of the grid-connected harmonic current is completed.

7. A grid-connected harmonic suppression system based on converter compensation vector iterative control, characterized in that: include: an acquisition module configured to generate a converter harmonic compensation voltage based on a phase angle transformation of a grid-type converter; an optimization module configured to perform compensation vector iterative control on the generated harmonic compensation voltage to obtain an optimal phase angle of the compensation voltage; a judgment module configured to increase the harmonic compensation voltage amplitude and judge the harmonic current direction according to the obtained optimal compensation voltage phase angle; a suppression module configured to suppress the grid-connected harmonic current according to the amplitude of the harmonic compensation voltage when the direction of the harmonic current changes, thereby completing the grid-connected harmonic suppression based on the iterative control of the converter compensation vector; The optimal phase angle of the compensation voltage is when the harmonic voltage at the grid connection point is most sensitive to the change in the compensation voltage amplitude, that is, the harmonic voltage at the grid connection point drops the fastest. for: ； in, is the change in compensation voltage; is the harmonic voltage at the grid connection point; The harmonic relationship between the modulation voltage, output current and grid-connected voltage is collected and analyzed to determine the moment when the harmonic flow direction changes. Based on their harmonic relationship, the variable HFD that characterizes the harmonic flow direction is defined as: ； in, is the grid connection point voltage, is the modulation signal, is the converter output current, is the harmonic order, is the fundamental angular frequency.

8. 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 grid-connected harmonic suppression method based on converter compensation vector iterative control according to any one of claims 1 to 6 are implemented.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the program, the steps of the grid-connected harmonic suppression method based on converter compensation vector iterative control are implemented as described in any one of claims 1 to 6.

10. A computer program product comprising software code, characterized in that The program in the software code executes the steps of the grid-connected harmonic suppression method based on converter compensation vector iterative control according to any one of claims 1 to 6.

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