Method, device and medium for extracting fundamental voltage component of grid connection point voltage

Abstract

The present disclosure provides a method, device, and medium for extracting the fundamental voltage component of the grid-connected point voltage. The method includes: obtaining a first positive-sequence component and a first negative-sequence component in a rotating coordinate system based on the three-phase voltage of the grid-connected point; decoupling the first positive-sequence component and the first negative-sequence component to estimate a second positive-sequence component and a second negative-sequence component; filtering the second positive-sequence component and the second negative-sequence component to obtain a positive fundamental component and a negative fundamental component; and obtaining a positive-sequence fundamental voltage component based on the positive fundamental component and the negative fundamental component. The fundamental voltage component extraction method according to an embodiment of the present invention is adaptable to three-phase imbalance.

Description

Technical Field

[0001] The present invention generally relates to the field of new energy, and more specifically, to a method, device and medium for extracting a fundamental voltage component of a grid connection point voltage. Background Art

[0002] The inertia response capability of wind turbines in renewable energy power plants relies on the ability to extract the positive sequence fundamental wave of the power grid with high precision and high response speed, thereby accurately calculating the power grid frequency and its rate of change.

[0003] The grid positive sequence fundamental is usually extracted based on the phase-locked loop of the grid voltage signal. The phase-locked loop mainly includes single synchronous phase-locked loop, dual synchronous phase-locked loop, second-order generalized integrator and orthogonal signal phase-locked loop. In addition, the grid positive sequence fundamental can also be extracted based on methods such as fast Fourier transform, Hilbert transform and Kalman filtering.

[0004] The positive-sequence fundamental extraction method based on a phase-locked loop has a good extraction effect under ideal voltage conditions. However, under conditions such as three-phase imbalance, harmonics, and frequency changes, the phase-locked loop method has difficulty balancing the contradiction between accuracy and response time. At the same time, the existence of the phase-locked loop PI controller has a certain impact on the extraction of the positive-sequence fundamental.

[0005] A single synchronous phase-locked loop (SPL) performs poorly in extracting the positive-sequence fundamental under three-phase imbalance and harmonic conditions. While a decoupled dual synchronous phase-locked loop (DPLL) achieves good extraction results under three-phase imbalance, its extraction accuracy is significantly affected by harmonics, and its dynamic response time is affected by the PI control bandwidth. The fast Fourier transform (FFT) can effectively avoid integer harmonic interference, effectively eliminating the impact of asymmetric power grids on positive-sequence fundamental extraction through positive- and negative-sequence decoupling. To mitigate the effects of interharmonics, the FFT requires sufficient data per operation to increase frequency resolution, which results in significant latency. Furthermore, applications generally require the controller sampling frequency to be an exponential power of 2, resulting in a relatively high computational load. The Hilbert transform can maintain the amplitude of each frequency signal, shift the phase by 90 degrees, and then extract the positive-sequence fundamental through phase-locking of orthogonal signals. However, the Hilbert transform is based on the FFT implementation, which is computationally intensive. The Kalman filter method can extract any harmonic of the fundamental wave through the state transfer matrix, but it requires a frequency-locked loop to lock the frequency, and the error feedback method affects the fundamental wave extraction. In addition, if the harmonic content of the power grid is complex, the calculation is large. Summary of the Invention

[0006] An exemplary embodiment of the present invention aims to provide a fundamental voltage component extraction method with adaptability to three-phase imbalance.

[0007] According to one aspect of the present invention, a method for extracting a fundamental voltage component of a grid-connected point voltage is provided. The method comprises: obtaining a first positive-sequence component and a first negative-sequence component in a rotating coordinate system based on the three-phase voltage of the grid-connected point; decoupling the first positive-sequence component and the first negative-sequence component to estimate a second positive-sequence component and a second negative-sequence component; filtering the second positive-sequence component and the second negative-sequence component to obtain a positive fundamental component and a negative fundamental component; and obtaining a positive-sequence fundamental voltage component based on the positive fundamental component and the negative fundamental component.

[0008] According to an embodiment of the present invention, the steps of respectively decoupling the first positive-sequence component and the first negative-sequence component to estimate the second positive-sequence component and the second negative-sequence component may include: cross-feedback decoupling the first negative-sequence component in a positive-sequence rotating coordinate system to obtain the second positive-sequence component; and cross-feedback decoupling the first positive-sequence component in a negative-sequence rotating coordinate system to obtain the second negative-sequence component, wherein the positive-sequence rotating coordinate system and the negative-sequence rotating coordinate system constitute a dual-synchronous rotating coordinate system.

[0009] According to an embodiment of the present invention, the step of obtaining a positive-sequence fundamental voltage component based on a positive fundamental component and a negative fundamental component may include: performing a dq / αβ coordinate inverse transformation on the positive fundamental component to obtain a first αβ voltage component; and performing an αβ / abc coordinate inverse transformation on the first αβ voltage component to obtain a positive-sequence fundamental voltage component.

[0010] According to an embodiment of the present invention, the step of obtaining a first positive-sequence component and a first negative-sequence component in a rotating coordinate system based on the three-phase voltage of the grid-connected point may include: filtering the three-phase voltage of the grid-connected point to obtain a filtered three-phase voltage; and performing coordinate transformation on the filtered three-phase voltage to obtain a first positive-sequence component and a first negative-sequence component in a rotating coordinate system.

[0011] According to an embodiment of the present invention, the filtering performed on the three-phase voltage at the grid connection point may be band-pass filtering or low-pass filtering, and the filtering performed on the second positive sequence component and the second negative sequence component may be low-pass filtering.

[0012] According to another aspect of the present invention, a computer-readable storage medium is provided. The computer-readable storage medium stores instructions or codes. When the instructions or codes are executed by a processor, the above-mentioned fundamental voltage component extraction method is implemented.

[0013] According to another aspect of the present invention, a fundamental voltage component extraction device for a grid connection point voltage is provided, comprising: a positive- and negative-sequence component acquisition unit, configured to obtain a first positive-sequence component and a first negative-sequence component in a rotating coordinate system based on the three-phase voltage of the grid connection point; a decoupling unit, configured to decouple the first positive-sequence component and the first negative-sequence component, respectively, to estimate a second positive-sequence component and a second negative-sequence component; a filtering unit, configured to filter the second positive-sequence component and the second negative-sequence component, respectively, to obtain a positive fundamental component and a negative fundamental component; and a fundamental voltage component acquisition unit, configured to obtain a positive-sequence fundamental voltage component based on the positive fundamental component and the negative fundamental component.

[0014] According to an embodiment of the present invention, the decoupling unit can be further configured to: cross-feedback decouple the first negative-sequence component in the positive-sequence rotating coordinate system, thereby obtaining a second positive-sequence component; cross-feedback decouple the first positive-sequence component in the negative-sequence rotating coordinate system, thereby obtaining a second negative-sequence component, wherein the positive-sequence rotating coordinate system and the negative-sequence rotating coordinate system constitute a dual-synchronous rotating coordinate system.

[0015] According to an embodiment of the present invention, the fundamental voltage component acquisition unit can be further configured to: perform dq / αβ coordinate inverse transformation on the positive fundamental component to obtain the first αβ voltage component, and perform αβ / abc coordinate inverse transformation on the first αβ voltage component to obtain the positive-sequence fundamental voltage component.

[0016] According to an embodiment of the present invention, the positive and negative sequence component acquisition unit can be further configured to: filter the three-phase voltage of the grid-connected point to obtain a filtered three-phase voltage; perform abc / αβ transformation on the filtered three-phase voltage to obtain a second αβ voltage component in an αβ coordinate system; perform positive and negative sequence rotating coordinate conversion on the second αβ voltage component to obtain a first positive sequence component and a first negative sequence component in a rotating coordinate system.

[0017] According to an embodiment of the present invention, the fundamental voltage component extraction device is provided in a converter controller of a wind turbine generator set.

[0018] Additional aspects and / or advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present general inventive concept. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects and features of exemplary embodiments of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings which exemplarily illustrate the embodiments, in which:

[0020] Figures 1 to 3 is a flowchart illustrating a fundamental voltage component extraction method according to an embodiment of the present invention;

[0021] Figure 4 is a diagram showing a positive and negative sequence ω′ speed rotation coordinate system according to an embodiment of the present invention;

[0022] Figure 5 is a block diagram illustrating a decoupling network according to an embodiment of the present invention;

[0023] Figure 6 is a block diagram showing a fundamental voltage component extraction device according to an embodiment of the present invention;

[0024] Figure 7 FIG. 1 is a schematic diagram illustrating a fundamental voltage component extraction device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like parts throughout. The embodiments are described below by referring to the drawings in order to explain the present invention.

[0026] According to the embodiment of the present invention, the coupling component in the positive and negative sequence components is eliminated by decoupling the first positive sequence component and the first negative sequence component, thereby achieving three-phase unbalance adaptability.

[0027] The fundamental voltage component extraction method and apparatus according to embodiments of the present invention can be used to extract the fundamental voltage component at a grid connection point of a new energy station, such as a wind farm, but is not limited thereto. The new energy station can be a wind farm or a photovoltaic station, or a station including a wind turbine and / or a photovoltaic power generation system.

[0028] The fundamental voltage component extraction method and device according to the embodiments of the present invention can meet the requirements of wind farm primary frequency regulation and inertia response for high-precision and high-response-speed fundamental voltage component extraction. Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0029] Figures 1 to 3 is a flowchart illustrating a fundamental voltage component extraction method according to an embodiment of the present invention, Figure 4 is a positive and negative sequence ω′ speed rotation coordinate system according to an embodiment of the present invention, Figure 5 is a block diagram illustrating a decoupling network according to an embodiment of the present invention.

[0030] like Figure 1 As shown, according to an embodiment of the present invention, the fundamental voltage component extraction method may include steps S110, S120, S130 and S140.

[0031] In step S110, based on the three-phase voltage v abc (See below Figure 7) obtain the first positive sequence component v in the rotating coordinate system dq + (v d + 、v q + , see below Figure 5 ) and the first negative sequence component v dq - (v d - 、v q - , see below Figure 5 ). Three-phase voltage v abc It can also be called three-phase grid voltage.

[0032] As an example, the first positive sequence component and the first negative sequence component can be obtained by coordinate conversion. For example, the three-phase voltage v can be converted from a three-phase stationary coordinate system to a two-phase stationary coordinate system. abc Converted to αβ voltage component v αβ (See below Figure 7 ), and then through the transformation from the two-phase stationary coordinate system to the two-phase rotating coordinate system, based on the voltage component v αβ The positive and negative sequence transformation obtains the first positive sequence component v dq + and the first negative sequence component v dq - .

[0033] As an example, the three-phase voltage v can be calculated before coordinate transformation. abc Filtering is performed to remove integer harmonics, super-synchronous harmonics, etc. The filtering here can be omitted. For example, when the grid voltage has few harmonic components, it is not necessary to filter the voltage at the grid connection point, and the voltage at the grid connection point can be directly converted into αβ voltage components v αβ .

[0034] like Figure 2 As shown, based on the three-phase voltage v of the grid connection point abc The step of obtaining a first positive sequence component and a first negative sequence component in a rotating coordinate system may include S1101 , S1102 , and S1103 .

[0035] In step S1101, the three-phase voltage of the grid connection point is filtered to obtain the filtered three-phase voltage v abc_BLF .

[0036] For three-phase voltage v abc The filtering can be low-pass filtering or band-pass filtering. abcWhen the filtering performed is low-pass filtering, the cutoff frequency of the low-pass filtering can be lower than the rated frequency of the grid. The cutoff frequency of the filter can also be set according to the harmonic situation. For example, the cutoff frequency of the low-pass filter can also be higher than the rated frequency of the grid.

[0037] When the three-phase voltage v abc When the filtering performed is band-pass filtering, the cut-off frequency of the band-pass filtering may be lower than the rated frequency of the power grid. For example, the cut-off frequency may be 30-40 Hz.

[0038] As an example, the filtering form for the three-phase voltage may also include high-pass, band-pass, and band-stop filters and combinations thereof.

[0039] In step S1102, the filtered three-phase voltage v abc_BSF Perform coordinate transformation to obtain the first positive sequence component and the first negative sequence component in the rotating coordinate system. For example, the filtered three-phase voltage v abc_BSF Perform abc / αβ transformation to obtain the αβ voltage component v in the αβ coordinate system αβ (For example, in order to distinguish it from the αβ voltage component obtained by inverse dq / αβ coordinate transformation, the αβ voltage component here is referred to as the second αβ voltage component).

[0040] v αβ The calculation process can be shown as formula (1) and (2).

[0041]

[0042] v αβ =T αβ v abc_BSF (2)

[0043] In formula (1), T αβ is a Clark transformation matrix. In the Clark transformation process, equal amplitude transformation or equal power transformation can be adopted, as long as the same transformation form is adopted in the transformation and subsequent inverse transformation process. For example, equal amplitude transformation is adopted in the Clark transformation process, and equal amplitude transformation is also adopted in the Clark inverse transformation process.

[0044] After the filtered three-phase voltage is transformed, the αβ voltage component (the second αβ voltage component) can be transformed into a positive and negative sequence rotating coordinate to obtain the first positive sequence component v in the rotating coordinate system. dq + (v d + 、v q + , see below Figure 5 ) and the first negative sequence component v dq- (v d - 、v q - , see below Figure 5 ).

[0045] Specifically, in step S1103, the αβ voltage component (the second αβ voltage component v αβ ) to perform positive and negative sequence rotating coordinate conversion to obtain the first positive sequence component (v dq + ) and the first negative sequence component (v dq - ).

[0046] After obtaining the first positive sequence component and the first negative sequence component, the first positive sequence component and the first negative sequence component may be decoupled to remove their respective coupling components.

[0047] like Figure 1 As shown, in step S120, the first positive sequence component and the first negative sequence component can be decoupled to estimate the second positive sequence component (v d +* 、v q +* , see below Figure 5 ) and the second negative sequence component (v d -* 、v q -* , see below Figure 5 ).

[0048] The first positive sequence component and the first negative sequence component can be decoupled in a rotating coordinate system, thereby estimating the positive and negative sequence components.

[0049] like Figure 3 As shown, the steps of respectively decoupling the first positive sequence component and the first negative sequence component to estimate the second positive sequence component and the second negative sequence component may include S1201 and S1202.

[0050] In step S1201 , the first negative sequence component is cross-feedback decoupled in a positive sequence rotating coordinate system, thereby obtaining a second positive sequence component.

[0051] In step S1202 , the first positive sequence component is cross-feedback decoupled in a negative sequence rotating coordinate system, thereby obtaining a second negative sequence component.

[0052] like Figure 4As shown, dual synchronous reference rotating coordinate systems can be established respectively. These two coordinate systems rotate at the positive-sequence angular velocity ω′ and the negative-sequence angular velocity -ω′, respectively. That is, they include the positive-sequence coordinate axis rotating at the positive-sequence angular velocity ω′ and its phase angle θ′, and the negative-sequence coordinate axis rotating at the negative-sequence angular velocity and its phase angle -θ′, so that the first negative-sequence component is decoupled on the positive-sequence coordinate axis rotating at the positive-sequence angular velocity ω′, and the first positive-sequence component is decoupled on the negative-sequence coordinate axis rotating at the negative-sequence angular velocity -ω′, thereby enabling the system to effectively extract the fundamental wave at the angular velocity ω′ even when the three-phase grid voltage is asymmetric (unbalanced).

[0053] Specifically, the angular velocity of the positive sequence reference coordinate axis can be set to ω′, the phase angle to θ′, θ′=ω′t; the input voltage vector v (ie, v αβ ), the phase angle is θ, ω′ can be set according to the distribution of subsynchronous harmonics in the power grid. The voltage vector v can be decomposed into v +1 and v -1 , satisfying the parallelogram relationship.

[0054] The positive sequence voltage vector is v +1 , the phase angle is ωt, and the negative sequence voltage vector is v -1 , the phase angle is -ωt, where ω is the angular velocity of the grid voltage vector, then the asymmetric input voltage vector in the dual ω′ speed reference coordinate system is expressed as Equation (3) and Equation (4).

[0055]

[0056]

[0057] Among them, T dq+1 is the positive sequence fundamental reference coordinate system transformation matrix, T dq-1 is the negative sequence fundamental reference coordinate system transformation matrix, and It can be expressed as formula (5).

[0058]

[0059] Wherein, θ′=ω′t=2πf0t, and f0 is the set frequency.

[0060] As mentioned above, in the decoupling network of the ω′ and -ω′ reference frames, the voltage vector v (i.e., v αβ ) can be viewed as two components rotating at angular frequencies ω and -ω (v +1 and v -1 ), the universal voltage vector v can be expressed as formula (6):

[0061]

[0062] Among them, θ+ ,θ - can be respectively positive and negative sequence components (v +1 and v -1 ) and can be set to zero, where the angular velocity ω refers to the angular velocity of the grid voltage vector, the voltage vector v (i.e., v αβ ) in dq + and dq - In the reference coordinate system, it can be expressed as Equation (7) and Equation (8):

[0063]

[0064]

[0065] Here, Refers to the grid voltage component v +1 Relative to d + The angle between the axes and the grid voltage component v -1 Relative to d - The angle between the axes.

[0066] As shown in equations (7) and (8), dq + The amplitude of the AC component on the axis depends on the dq - The DC component on the axis, and vice versa dq - The amplitude of the AC component on the axis depends on the dq + The DC component on the axis, after determining the coupling term between the two coordinate systems, can be eliminated by using the corresponding decoupling network -1 Voltage vector in dq + The coupled signal (or coupled component) generated on the axis, and v +1 Voltage vector in dq - The coupled signal generated on the axis.

[0067] That is to say, except for v in the above formula (7), +1 The coupling terms other than v are removed, and the above equation (8) is replaced by -1 The coupling terms other than are removed.

[0068] The following describes the process of obtaining or estimating the fundamental components in the positive-sequence and negative-sequence reference coordinate systems using a cross-feedback decoupling network as an example.

[0069] like Figure 5 As shown, according to an embodiment of the present invention, the coupling term can be removed by the decoupling network 501. For example, regarding the first positive sequence component (v d + 、v q +), the decoupling network 501 can remove the coupling term of the first positive sequence component by the following decoupling term obtained through mathematical operations such as multiplication, addition, subtraction, sine / cosine, etc.:

[0070] First decoupling term:

[0071] Thus, the second positive sequence component can be obtained and Regarding the first negative sequence component (v d - 、v q - ), the decoupling network 501 can receive the input ωt and remove the coupling term of the first negative sequence component through the following decoupling terms obtained through mathematical operations such as multiplication, addition, subtraction, sine / cosine, etc.:

[0072] Second decoupling term:

[0073] Thus, the second negative sequence component can be obtained The decoupling network 501 can be implemented by software and / or hardware. According to an embodiment of the present invention, the coupling term can be completely eliminated during decoupling, but this is only an example. The decoupling network can also be used to partially eliminate or weaken the coupling term. -1 Voltage vector in dq + The coupled signal generated on the axis, and v +1 Voltage vector in dq - The coupled signal generated on the axis.

[0074] like Figure 1 As shown, in step S130, the second positive sequence component and the second negative sequence component are filtered respectively to obtain a positive fundamental wave component and a negative fundamental wave component.

[0075] Specifically, after decoupling, the second positive sequence component can be and the second negative sequence component Perform filtering (e.g., low-pass filtering), and the transfer function is shown in the following equation (9):

[0076]

[0077] Cutoff frequency ω f Can be pre-set, ω0 is the rated angular velocity of the power grid, and the filtering results in dq + Positive fundamental component in the coordinate system and negative fundamental component

[0078] In the numbers of the formulas and drawings, the superscript "+" involving the dq coordinate refers to "+1" or "1", and the superscript "-" involving the dq coordinate refers to "-1".

[0079] like Figure 7 As shown, the negative fundamental component here can be cross-fed back to the decoupling network of the first positive sequence component to generate a first decoupling term corresponding to the coupling term. As an example, the negative fundamental component Can correspond to v -1 Voltage vector.

[0080] Finally, in step S140, a positive-sequence fundamental voltage is obtained according to the positive fundamental component and the negative fundamental component. Specifically, the step of obtaining the positive-sequence fundamental voltage according to the positive fundamental component and the negative fundamental component may include: transforming the positive fundamental component to obtain the positive-sequence fundamental voltage component.

[0081] Specifically, the step of transforming the positive fundamental wave component to obtain the positive sequence fundamental wave voltage component may include: performing a dq / αβ coordinate inverse transformation on the positive fundamental wave component, wherein the inverse transformation angular velocity is set to ω′, to obtain the αβ voltage component (the first αβ voltage component Then, the first αβ voltage component is subjected to an αβ / abc coordinate inverse transformation to obtain the positive sequence fundamental voltage component The dq / αβ coordinate inverse transformation here is just an example and is not particularly limited.

[0082] Specifically, the positive fundamental wave component and the negative fundamental wave component can be transformed into the αβ coordinate system according to the same angular velocity and phase angle. The transformation method can be shown in the following equations (10) and (11).

[0083]

[0084]

[0085] Thus, the first αβ voltage component can be obtained It is a set of orthogonal signals, and then the positive sequence fundamental voltage component is obtained by inverse transformation through formula (12):

[0086]

[0087] Each operation of the above steps can be written as a software program or instruction. Therefore, the fundamental voltage extraction method according to the exemplary embodiment of the present invention can be implemented via software. The computer-readable storage medium of the exemplary embodiment of the present invention can store a computer program or instruction. When the computer program is executed by the processor, the fundamental voltage component extraction method as described in the above exemplary embodiment is implemented.

[0088] Figure 6is a block diagram showing a fundamental voltage component extraction device according to an embodiment of the present invention, Figure 7 FIG. 1 is a schematic diagram illustrating a fundamental voltage component extraction device according to an embodiment of the present invention.

[0089] The fundamental voltage component extraction device of the grid connection point voltage according to an embodiment of the present invention may include a positive and negative sequence component acquisition unit 410 , a decoupling unit 420 , a filtering unit 430 and a fundamental voltage component acquisition unit 440 .

[0090] The positive and negative sequence component acquisition unit 410 can obtain the first positive sequence component v in the rotating coordinate system based on the three-phase voltage of the grid connection point. dq + (v d + 、v q + ) and the first negative sequence component v dq - (v d - 、v q - ).

[0091] Specifically, the positive and negative sequence component acquisition unit 410 can filter the three-phase voltage of the grid connection point to obtain the filtered three-phase voltage, and perform abc / αβ transformation on the filtered three-phase voltage to obtain the αβ voltage component v in the αβ coordinate system. αβ (second αβ voltage component), the second αβ voltage component is transformed into a positive-negative sequence rotating coordinate to obtain the first positive sequence component v in the rotating coordinate system dq + and the first negative sequence component v dq - .

[0092] The filtering here can be band-pass filtering or low-pass filtering, and the specific cutoff frequency can be as described above, which will not be repeated here.

[0093] The decoupling unit 420 (DC) can respectively dq + and the first negative sequence component v dq - Decoupling is performed to estimate the second positive sequence component and the second negative sequence component

[0094] The filtering unit 430 can respectively and the second negative sequence component Filter to obtain the positive fundamental component and negative fundamental component The filtering unit 430 may include a plurality of low-pass filters, and the cutoff frequencies of the low-pass filters may be predetermined.

[0095] Here, the negative fundamental component is cross-fed back to the positive-sequence decoupling section of decoupling unit 420, causing it to generate a first decoupling term corresponding to the coupling term in the first positive-sequence component, thereby canceling the coupling term in the first positive-sequence component. Similarly, the positive fundamental component is cross-fed back to the negative-sequence decoupling section of decoupling unit 420, causing it to generate a second decoupling term corresponding to the coupling term in the first negative-sequence component.

[0096] The fundamental voltage component acquisition unit 440 may obtain a positive-sequence fundamental voltage component according to the positive fundamental component and the negative fundamental component.

[0097] For example, the fundamental voltage component acquisition unit 440 may transform the positive fundamental component to obtain a positive-sequence fundamental voltage component.

[0098] The fundamental voltage component acquisition unit 440 may perform a dq / αβ coordinate inverse transformation on the positive sequence fundamental voltage component to obtain a first αβ voltage component, and perform an αβ / abc coordinate inverse transformation on the first αβ voltage component to obtain a positive sequence fundamental voltage component.

[0099] The decoupling unit 420 can perform cross-feedback decoupling of the positive and negative sequence components in the corresponding rotating coordinate system to eliminate coupling signals generated by the positive and negative sequence components on the corresponding rotating coordinate axes, thereby obtaining a second positive sequence component and a second negative sequence component.

[0100] Specifically, the decoupling unit 420 can perform cross-feedback decoupling of the first negative-sequence component in the positive-sequence rotating coordinate system to eliminate the coupling signal generated by the first positive-sequence component on the negative-sequence rotating coordinate axis, thereby obtaining the second positive-sequence component.

[0101] The decoupling unit 420 can perform cross-feedback decoupling of the first positive sequence component in the negative sequence rotating coordinate system to eliminate the coupling signal generated by the first negative sequence component on the positive sequence rotating coordinate axis, thereby obtaining the second negative sequence component.

[0102] As described above, the positive sequence rotating coordinate system and the negative sequence rotating coordinate system constitute a dual synchronous rotating coordinate system, and the rotation angular velocities are the same in magnitude but opposite in direction.

[0103] Cross-feedback decoupling is merely an example, and the decoupling method is not particularly limited. For example, when partially eliminating coupling terms, other decoupling methods may be used.

[0104] According to various embodiments of the present disclosure, a device (e.g., a module or its functions) or a method may be implemented by a program or instruction stored in a computer-readable storage medium. When the instruction is executed by a processor, the processor may perform a function corresponding to the instruction or perform a method corresponding to the instruction.

[0105] At least a portion of a module or unit can be implemented (e.g., executed) by a processor. At least a portion of a programming module can include modules, programs, routines, instruction sets, and processes for performing at least one function. In one example, instructions or software include machine code (such as machine code generated by a compiler) that is directly executed by one or more processors or computers. In another example, instructions or software include higher-level code that is executed by one or more processors or computers using an interpreter. Instructions or software can be written in any programming language based on the block diagrams and flow charts shown in the accompanying drawings and the corresponding description in the specification.

[0106] Computer-readable storage media include magnetic media such as floppy disks and magnetic tapes, optical media (including compact disc (CD) ROMs and DVD ROMs), magneto-optical media such as flexible optical disks, and hardware devices such as ROMs, RAMs, and flash memories designed to store and execute program commands. Program commands include language codes executable by a computer using an interpreter and machine language codes generated by a compiler. The aforementioned hardware devices may be implemented by one or more software modules for performing the operations of various embodiments of the present disclosure.

[0107] The modules or programming modules of the present disclosure may include at least one of the aforementioned components with some components omitted or other components added. The operations of the modules, programming modules or other components may be performed sequentially, in parallel, in a loop or in a trial manner. In addition, some operations may be performed in a different order, may be omitted or expanded with other operations.

[0108] The computer-readable storage medium and / or the fundamental voltage component extraction device of the exemplary embodiments of the present invention may be a part of a computing device, a controller, or a control system, and may be provided in a converter controller of a wind turbine generator.

[0109] For example, according to an exemplary embodiment of the present invention, a computing device may be provided, which may include: a processor (not shown) and a memory (not shown, which may be a computer-readable storage medium), wherein the memory stores a computer program (code or instruction), and when the computer program is executed by the processor, the fundamental voltage component extraction method as described in the above exemplary embodiment is implemented.

[0110] The fundamental voltage component extraction method and fundamental voltage component extraction device according to the embodiments of the present invention decouple positive and negative signals and eliminate the influence of asymmetry on the power grid.

[0111] The fundamental voltage component extraction method and the fundamental voltage component extraction device according to the embodiments of the present invention can filter out harmonic components of the three-phase voltage through a filter with a relatively large cutoff frequency.

[0112] The fundamental voltage component extraction method and fundamental voltage component extraction device according to the embodiments of the present invention do not require a phase-locked loop, thereby improving the response time of positive-sequence fundamental wave extraction and avoiding disturbances caused by the phase-locked loop.

[0113] The fundamental voltage component extraction method and the fundamental voltage component extraction device according to the embodiments of the present invention have high precision and high response time for extracting the positive sequence fundamental of a power grid.

[0114] Although some exemplary embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that modifications may be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents; for example, the technical features of different embodiments may be combined.

Claims

1. A method for extracting the fundamental voltage component of the grid connection point voltage, characterized in that: include: Obtaining a first positive sequence component and a first negative sequence component in a rotating coordinate system based on the three-phase voltage of the grid connection point; Decoupling the first positive sequence component and the first negative sequence component respectively to estimate a second positive sequence component and a second negative sequence component; Filtering the second positive sequence component and the second negative sequence component respectively to obtain a positive fundamental wave component and a negative fundamental wave component; The positive sequence fundamental voltage component is obtained according to the positive fundamental component and the negative fundamental component. The step of obtaining a first positive sequence component and a first negative sequence component in a rotating coordinate system based on the three-phase voltage of the grid connection point includes: performing abc / αβ coordinate transformation on the three-phase voltage to obtain an αβ voltage component, and then performing an αβ / dq positive-negative sequence rotating coordinate transformation on the αβ voltage component based on a first phase angle to obtain the first positive sequence component and the first negative sequence component. The step of obtaining a positive-sequence fundamental voltage component according to the positive fundamental component and the negative fundamental component includes: performing a dq / αβ coordinate inverse transformation on the positive fundamental component based on the first phase angle to obtain a first αβ voltage component, performing an αβ / abc coordinate inverse transformation on the first αβ voltage component to obtain a positive-sequence fundamental voltage component, The first phase angle used in the positive-negative sequence rotation coordinate transformation and the first phase angle used in the inverse coordinate transformation are calculated based on the same set angular frequency, and the set angular frequency is the product of 2π and the set frequency.

2. The method for extracting the fundamental voltage component of the grid connection point voltage according to claim 1, characterized in that: The steps of respectively decoupling the first positive sequence component and the first negative sequence component to estimate the second positive sequence component and the second negative sequence component include: Decoupling the first negative sequence component by cross-feedback in the positive sequence rotating coordinate system, thereby obtaining the second positive sequence component; The first positive sequence component is decoupled by cross-feedback in the negative sequence rotating coordinate system to obtain the second negative sequence component. The positive-sequence rotating coordinate system and the negative-sequence rotating coordinate system constitute a dual-synchronous rotating coordinate system.

3. The method for extracting the fundamental voltage component of the grid connection point voltage according to any one of claims 1 to 2, characterized in that: The step of obtaining a first positive sequence component and a first negative sequence component in a rotating coordinate system based on the three-phase voltage of the grid connection point further includes: Before coordinate conversion, the three-phase voltage at the grid connection point is filtered to obtain a filtered three-phase voltage.

4. The method for extracting the fundamental voltage component of the grid connection point voltage according to claim 3, characterized in that: The filtering performed on the three-phase voltage of the grid connection point is band-pass filtering or low-pass filtering, and the filtering performed on the second positive sequence component and the second negative sequence component is low-pass filtering.

5. A computer-readable storage medium, characterized in that The computer-readable storage medium stores instructions or codes, which, when executed by a processor, implement the fundamental voltage component extraction method according to any one of claims 1 to 4.

6. A device for extracting the fundamental voltage component of the grid connection point voltage, characterized in that: include: a positive-negative sequence component acquisition unit configured to obtain a first positive-sequence component and a first negative-sequence component in a rotating coordinate system based on the three-phase voltage of the grid connection point; a decoupling unit configured to decouple the first positive sequence component and the first negative sequence component respectively to estimate a second positive sequence component and a second negative sequence component; A filtering unit is configured to filter the second positive sequence component and the second negative sequence component respectively to obtain a positive fundamental component and a negative fundamental component; The fundamental voltage component acquisition unit is configured to obtain a positive sequence fundamental voltage component according to the positive fundamental component and the negative fundamental component. The positive-negative sequence component acquisition unit is further configured to perform an abc / αβ coordinate transformation on the three-phase voltage to obtain an αβ voltage component, and then perform an αβ / dq positive-negative sequence rotation coordinate transformation on the αβ voltage component based on a first phase angle to obtain the first positive-sequence component and the first negative-sequence component. The fundamental voltage component acquisition unit is further configured to: perform a dq / αβ coordinate inverse transformation on the positive fundamental component based on the first phase angle to obtain a first αβ voltage component, and perform an αβ / abc coordinate inverse transformation on the first αβ voltage component to obtain a positive sequence fundamental voltage component. The first phase angle used in the positive-negative sequence rotation coordinate transformation and the first phase angle used in the inverse coordinate transformation are calculated based on the same set angular frequency, and the set angular frequency is the product of 2π and the set frequency.

7. The fundamental voltage component extraction device of the grid connection point voltage according to claim 6, characterized in that: The decoupling unit is further configured to: Decoupling the first negative sequence component by cross-feedback in the positive sequence rotating coordinate system, thereby obtaining the second positive sequence component; The first positive sequence component is decoupled by cross-feedback in the negative sequence rotating coordinate system to obtain the second negative sequence component. The positive-sequence rotating coordinate system and the negative-sequence rotating coordinate system constitute a dual-synchronous rotating coordinate system.

8. The fundamental voltage component extraction device of the grid connection point voltage according to claim 6, characterized in that: The positive and negative sequence component acquisition unit is further configured to: The three-phase voltage at the grid connection point is filtered before coordinate conversion to obtain filtered three-phase voltage.

9. The device for extracting the fundamental voltage component of the grid connection point voltage according to any one of claims 6 to 8, characterized in that: The fundamental voltage component extraction device is arranged in a converter controller of a wind turbine generator set.

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