Method and device for extracting fundamental positive and negative sequence components

Abstract

The application discloses a method and device for extracting fundamental positive sequence components and negative sequence components. A preset value of collection times is set according to different power grid environments, three-phase electric signals at a current time are collected to perform coordinate system transformation, and a transformation result is stored; when the collection times are equal to the preset value, equations capable of obtaining the fundamental positive sequence components and the negative sequence components of the electric signals are listed according to the transformation result and are solved. Considering various power grid environments, the fundamental positive sequence components and the negative sequence components can be extracted for different regional power grid environments by changing the value of the collection times; the greater the preset value is, the smaller the influence of voltage imbalance and harmonics on the extraction result is, the stronger the anti-interference performance is, errors caused by adverse power grid environments on the extraction result can be reduced, and the fundamental positive sequence components and the negative sequence components can be accurately extracted.

Description

Technical Field

[0001] This application relates to the field of power system technology, and in particular to a method and apparatus for extracting the fundamental positive sequence component and the negative sequence component. Background Technology

[0002] With the development of renewable energy technologies, wind power generation is receiving increasing attention. Wind turbines are typically installed in remote areas at the end of the power grid, resulting in a weak grid connection. In such weakly connected grids, voltage imbalances and harmonics often occur, severely affecting the operation of wind turbines. To ensure the stable operation of the power grid system, it is necessary to accurately detect the positive and negative sequence components of the grid voltage for subsequent operations.

[0003] In existing technologies, three-phase synchronous phase-locked loops can extract the positive-sequence and negative-sequence components of the current fundamental frequency, but the extraction results are not accurate enough in weakly connected power grid environments. Therefore, how to accurately extract the positive-sequence and negative-sequence components of the fundamental frequency under different power grid environments has become an urgent problem to be solved. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a method and apparatus for extracting the fundamental positive-sequence component and the negative-sequence component, so as to accurately extract the fundamental positive-sequence component and the negative-sequence component under different power grid environments.

[0005] This application discloses a method for extracting the fundamental positive-sequence component and the negative-sequence component, the method comprising:

[0006] Set a preset value for the number of data collections based on the power grid environment;

[0007] Collect the three-phase electrical signals at the current moment;

[0008] The three-phase electrical signal is transformed from a three-phase coordinate system to a two-phase coordinate system, and the transformation result is stored.

[0009] When the cumulative number of data collections equals the preset value, an equation is derived based on the transformation result.

[0010] Solving the equation yields the fundamental positive-sequence component and the negative-sequence component of the electrical signal.

[0011] Optionally, setting a preset value for the number of data collections based on the power grid environment includes:

[0012] Set the preset state of the power grid environment;

[0013] Determine whether the current power grid environment meets the preset state of the power grid environment;

[0014] If so, then increase the preset value;

[0015] If not, then lower the preset value; the preset value is an integer not less than 1.

[0016] Optionally, the transformation of the three-phase electrical signal from a three-phase coordinate system to a two-phase coordinate system and the storage of the transformation result include:

[0017] The fundamental wave rotation vector in a two-phase stationary coordinate system is expressed by the fundamental wave rotation vector formula.

[0018] Substituting the relationship between the two-phase stationary coordinate system and the two-phase rotating coordinate system into the fundamental wave rotation vector formula, the formula for the two-phase electrical signal is obtained;

[0019] The two-phase rotation coordinates of the fundamental positive-sequence rotation vector and the two-phase rotation coordinates of the fundamental negative-sequence rotation vector are stored in an array as transformation results.

[0020] Optionally, listing the equations based on the transformation result includes:

[0021] The fitting function is obtained by combining the transformation result with the formula of the two-phase electrical signal;

[0022] The objective function is obtained based on the transformation result and the fitting function;

[0023] The equation is obtained by minimizing the objective function.

[0024] Optionally, solving the equation to obtain the fundamental positive-sequence component and negative-sequence component of the electrical signal includes: solving the equation using the least squares method to obtain the fundamental positive-sequence component and negative-sequence component of the electrical signal.

[0025] Based on the above-mentioned method for extracting the fundamental positive-sequence component and the negative-sequence component, this application also discloses an apparatus for extracting the fundamental positive-sequence component and the negative-sequence component, comprising: a sampling number setting unit, a sampling unit, a coordinate system transformation unit, an equation acquisition unit, and an equation solving unit;

[0026] The data collection number setting unit is used to set a preset value for the number of data collections according to the power grid environment;

[0027] The acquisition unit is used to acquire the three-phase electrical signals at the current moment;

[0028] The coordinate system transformation unit is used to transform the three-phase electrical signal from a three-phase coordinate system to a two-phase coordinate system and store the transformation results;

[0029] The equation acquisition unit is used to list the equation based on the transformation result when the cumulative number of collections equals the preset value.

[0030] The equation solving unit is used to solve the equation to obtain the fundamental positive-sequence component and negative-sequence component of the electrical signal.

[0031] Optionally, the data collection count setting unit includes:

[0032] The preset state setting subunit is used to set the preset state of the power grid environment;

[0033] The judgment subunit is used to determine whether the current power grid environment meets the preset state of the power grid environment;

[0034] The up-adjustment subunit is used to increase the preset value;

[0035] The down-adjustment subunit is used to down-adjust the preset value; the preset value is an integer not less than 1.

[0036] Optionally, the coordinate system transformation unit includes:

[0037] The fundamental wave rotation vector representation sub-unit is used to represent the fundamental wave rotation vector in a two-phase stationary coordinate system using the fundamental wave rotation vector formula.

[0038] The two-phase formula acquisition sub-unit is used to substitute the relationship between the two-phase stationary coordinate system and the two-phase rotating coordinate system into the fundamental wave rotating vector formula to obtain the formula for the two-phase electrical signal.

[0039] The storage sub-unit is used to store the two-phase rotation coordinate values ​​of the fundamental positive-sequence rotation vector and the two-phase rotation coordinate values ​​of the fundamental negative-sequence rotation vector as transformation results in an array.

[0040] Optionally, the equation acquisition unit includes:

[0041] The fitting function obtains the sub-unit, which is used to combine the transformation result with the formula of the two-phase electrical signal to obtain the fitting function;

[0042] The objective function acquisition sub-unit is used to obtain the objective function based on the transformation result and the fitting function;

[0043] The minimum value unit is used to minimize the objective function, thus obtaining the equation.

[0044] Optionally, the equation solving unit is used to: solve the equation using the least squares method to obtain the fundamental positive-sequence component and the negative-sequence component of the electrical signal.

[0045] This application discloses a method and apparatus for extracting the fundamental positive-sequence and negative-sequence components. A preset value for the number of acquisitions is set according to different power grid environments. The three-phase electrical signal at the current moment is acquired for coordinate system transformation, and the transformation results are stored. When the number of acquisitions equals the preset value, equations for obtaining the fundamental positive-sequence and negative-sequence components of the electrical signal are derived from the transformation results and solved. Considering various power grid environments, by changing the value of the number of acquisitions, the fundamental positive-sequence and negative-sequence components can be extracted for different regional power grid environments. The larger the preset value, the less the extraction results are affected by voltage imbalance and harmonics, and the stronger the anti-interference ability, reducing the errors caused by adverse power grid environments and accurately extracting the fundamental positive-sequence and negative-sequence components. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0047] Figure 1 This is a flowchart illustrating a method for extracting the fundamental positive-sequence component and the negative-sequence component disclosed in an embodiment of this application;

[0048] Figure 2 This is a flowchart illustrating another method for extracting the fundamental positive-sequence component and the negative-sequence component disclosed in an embodiment of this application;

[0049] Figure 3 This is a schematic diagram of the structure of a device for extracting the fundamental positive-sequence component and the negative-sequence component, as disclosed in an embodiment of this application. Detailed Implementation

[0050] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] Example 1: This application discloses a method for extracting the fundamental positive sequence component and the negative sequence component.

[0052] For details, please refer to Figure 1 The method for extracting the fundamental positive-sequence component and the negative-sequence component disclosed in this embodiment includes the following steps:

[0053] Step 101: Set the preset value for the number of data collections based on the power grid environment.

[0054] In the method described in this embodiment, a preset state of the power grid environment is first set. As an optional method, the preset state of the power grid environment can be that the power grid voltage is unbalanced and has harmonics exceeding a preset level. It is then determined whether the current power grid environment meets the preset state. If it does, the preset value is increased; otherwise, the preset value is decreased. The preset value is an integer not less than 1.

[0055] As an optional method, when the current power grid environment meets the preset state, the corresponding preset value is adjusted upwards based on the magnitude of the harmonic content in the current power grid environment. For example, if the preset harmonic content in the preset state is 3%, then when the harmonic content in the current power grid environment is 4%, the preset value is set to 8; when the harmonic content in the current power grid environment is 7%, the preset value is set to 10. Conversely, when the current power grid environment does not meet the preset state, the corresponding preset value is adjusted downwards based on the magnitude of the harmonic content in the current power grid environment. For example, if the preset harmonic content in the preset state is 3%, then when the harmonic content in the current power grid environment is 1%, the preset value is set to 2; when the harmonic content in the current power grid environment is 0.5%, the preset value is set to 1. The above examples are only for ease of understanding and do not specifically limit the methods for setting the preset state and preset values ​​of the power grid environment.

[0056] Step 102: Collect the three-phase electrical signals at the current moment.

[0057] In the method described in this embodiment, the electrical signal can be either voltage or current, as needed. As an optional method, when it is necessary to extract the fundamental positive-sequence component and the negative-sequence component of the voltage, the three-phase voltage at the current moment is collected; when it is necessary to extract the fundamental positive-sequence component and the negative-sequence component of the current, the three-phase current at the current moment is collected.

[0058] Step 103: Transform the three-phase electrical signal from a three-phase coordinate system to a two-phase coordinate system and store the transformation result.

[0059] In the method described in this embodiment, the fundamental wave rotation vector expression in the two-phase stationary coordinate system (αβ coordinate system) is:

[0060]

[0061] in, Representing the fundamental wave rotation vector in the αβ coordinate system, it can be either the power supply phase signal or the load phase signal. It is composed of the fundamental wave positive sequence rotation vector. and fundamental negative sequence rotation vector synthesis.

[0062] In the method described in this embodiment, the relationship between the αβ coordinate system and the two-phase rotating coordinate system (dq coordinate system) is as follows:

[0063]

[0064]

[0065] Where ω is the synchronous speed. and The two-phase rotating coordinate values ​​of the fundamental positive sequence rotating vector are represented by the values ​​of the fundamental positive sequence rotating vector on the d-axis and q-axis in the dq coordinate system, respectively. and The two-phase rotating coordinate values ​​of the fundamental negative sequence rotating vector are denoted as d-axis and q-axis values ​​in the dq coordinate system, respectively.

[0066] As an alternative method, substituting formulas (2) and (3) into formula (1) yields the formula for the two-phase electrical signal:

[0067]

[0068] Among them, E α and E β yes The values ​​on the α-axis and β-axis in the αβ coordinate system. For ease of calculation, as an optional method, formula (4) can be rewritten as follows:

[0069]

[0070] As an optional method, given that ωt is known, the two-phase rotation coordinate values ​​of the fundamental positive-sequence rotation vector and the fundamental negative-sequence rotation vector are stored in an array. Optionally, the actual operation can be as follows:

[0071] make

[0072] Step 104: When the cumulative number of collections equals the preset value, list the equations based on the transformation results.

[0073] In the method described in this embodiment, as an optional method, it is determined whether the cumulative number of collections is equal to a preset value. If so, an equation is listed based on the transformation result; otherwise, the process returns to step 102.

[0074] In the method described in this embodiment, as an optional method, let the transformation result y = E stored in the array. α +jE β , Then, combining this with formula (5), we obtain the fitting function:

[0075]

[0076] The above For the conjugate of x, the It is the conjugate of y.

[0077] As an optional method, if the number of data collections is n, then based on the stored n sets of data (x1, y1), (x2, y2), ..., (x n ,y n The objective function is obtained as follows:

[0078]

[0079] To minimize equation (7) (with partial derivatives equal to 0), we need to solve the system of equations:

[0080]

[0081] Equation (8) is derived to obtain the following equation:

[0082]

[0083] Step 105: Solve the equation to obtain the fundamental positive-sequence component and negative-sequence component of the electrical signal.

[0084] In the method described in this embodiment, as an optional method, the fundamental positive sequence component a of the electrical signal can be obtained by solving formula (9) using the least squares method. 11 a 12 and negative order component a 21 a 22 .

[0085] The method described in this embodiment can set a preset state of the power grid environment according to actual operation, and then compare the difference between the current power grid environment and the preset state (e.g., harmonic content) to set a preset value for the number of acquisitions. The three-phase electrical signals acquired at each moment are subjected to coordinate system transformation and the transformation results are stored. When the number of acquisitions is equal to the preset value, equations for obtaining the fundamental positive-sequence and negative-sequence components of the electrical signal are listed and solved. Considering various power grid environments, the fundamental positive-sequence and negative-sequence components are extracted for different regions by changing the value of the number of acquisitions, thereby reducing the errors caused by voltage imbalance and harmonics on the extraction results, and accurately extracting the fundamental positive-sequence and negative-sequence components.

[0086] Example 2: This application discloses another method for extracting the fundamental positive-sequence component and the negative-sequence component. Please refer to [link to relevant documentation]. Figure 2 This embodiment introduces a method for extracting the positive and negative sequence components of the voltage fundamental wave.

[0087] Step 201: Set the preset value for the number of data collections based on the power grid environment.

[0088] In the method described in this embodiment, as an optional approach, a preset value of n is set.

[0089] Step 202: Collect the three-phase voltage at the current moment.

[0090] Step 203: Transform the three-phase voltage from the three-phase coordinate system to the two-phase coordinate system to obtain the two-phase voltage.

[0091] Step 204: Store the obtained two-phase voltages and the sinωt and cosωt generated during the transformation into arrays in sequence.

[0092] In the method described in this embodiment, as an optional method, the array can be a1, a2, a3, etc.

[0093] Step 205: Determine whether the cumulative number of collections is equal to the preset value. If yes, proceed to step 206; otherwise, return to step 202.

[0094] Step 206: Obtain the equation based on the data stored in the array.

[0095] In the method described in this embodiment, as an optional method, based on a1, a2, a3...a n The data stored in the middle is used to derive the equation.

[0096] Step 207: Solve the equation to obtain the fundamental positive-sequence component and negative-sequence component of the voltage.

[0097] This embodiment describes a method for extracting the fundamental positive and negative sequence components of voltage. It involves collecting three-phase voltages with the same number of preset values, transforming them, storing the transformation results, and listing equations to solve for the fundamental positive and negative sequence components of the voltage. This method can extract the fundamental positive and negative sequence components of voltage for different regional power grid environments, reducing errors caused by adverse power grid environments and accurately extracting the fundamental positive and negative sequence components.

[0098] Correspondingly, when it is necessary to extract the positive and negative sequence components of the fundamental current, the three-phase voltage used in the above steps can be replaced with three-phase current.

[0099] Based on the method for extracting the fundamental positive-sequence and negative-sequence components disclosed in the above embodiments, this embodiment correspondingly discloses an apparatus for extracting the fundamental positive-sequence and negative-sequence components. Please refer to... Figure 3 The device for extracting the fundamental positive sequence component and the negative sequence component includes: a sampling number setting unit 301, a sampling unit 302, a coordinate system transformation unit 303, an equation acquisition unit 304, and an equation solving unit 305.

[0100] The data collection number setting unit 301 is used to set a preset value for the number of data collections according to the power grid environment;

[0101] The acquisition unit 302 is used to acquire the three-phase electrical signal at the current moment;

[0102] The coordinate system transformation unit 303 is used to transform the three-phase electrical signal from a three-phase coordinate system to a two-phase coordinate system and store the transformation result;

[0103] The equation acquisition unit 304 is used to list the equation based on the transformation result when the cumulative number of collections equals the preset value.

[0104] The equation solving unit 305 is used to solve the equation to obtain the fundamental positive-sequence component and negative-sequence component of the electrical signal.

[0105] Optionally, the data collection count setting unit 301 includes:

[0106] The preset state setting subunit is used to set the preset state of the power grid environment;

[0107] The judgment subunit is used to determine whether the current power grid environment meets the preset state of the power grid environment;

[0108] The up-adjustment subunit is used to increase the preset value;

[0109] The down-adjustment subunit is used to down-adjust the preset value; the preset value is an integer not less than 1.

[0110] Optionally, the coordinate system transformation unit 303 includes:

[0111] The fundamental wave rotation vector representation sub-unit is used to represent the fundamental wave rotation vector in a two-phase stationary coordinate system using the fundamental wave rotation vector formula.

[0112] The two-phase formula acquisition sub-unit is used to substitute the relationship between the two-phase stationary coordinate system and the two-phase rotating coordinate system into the fundamental wave rotating vector formula to obtain the formula for the two-phase electrical signal.

[0113] The storage sub-unit is used to store the two-phase rotation coordinate values ​​of the fundamental positive-sequence rotation vector and the two-phase rotation coordinate values ​​of the fundamental negative-sequence rotation vector as transformation results in an array.

[0114] Optionally, the equation acquisition unit 304 includes:

[0115] The fitting function obtains the sub-unit, which is used to combine the transformation result with the formula of the two-phase electrical signal to obtain the fitting function;

[0116] The objective function acquisition sub-unit is used to obtain the objective function based on the transformation result and the fitting function;

[0117] The minimum value unit is used to minimize the objective function, thus obtaining the equation.

[0118] Optionally, the equation solving unit 305 is used to: solve the equation using the least squares method to obtain the fundamental positive-sequence component and the negative-sequence component of the electrical signal.

[0119] The embodiments in this specification are described in a progressive manner. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant details can be found in the method section.

[0120] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0121] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0122] The features described in the embodiments of this specification can be substituted for or combined with each other, so that those skilled in the art can implement or use this application.

[0123] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for extracting the fundamental positive-sequence component and the negative-sequence component, characterized in that, include: Set a preset value for the number of data collections based on the power grid environment; Collect the three-phase electrical signals at the current moment; The three-phase electrical signal is transformed from a three-phase coordinate system to a two-phase coordinate system, and the transformation result is stored. When the cumulative number of data collections equals the preset value, an equation is derived based on the transformation result. Solving the equation yields the fundamental positive-sequence component and the negative-sequence component of the electrical signal; The transformation of the three-phase electrical signal from a three-phase coordinate system to a two-phase coordinate system, and the storage of the transformation results, includes: The fundamental wave rotation vector in a two-phase stationary coordinate system is expressed by the fundamental wave rotation vector formula. Substituting the relationship between the two-phase stationary coordinate system and the two-phase rotating coordinate system into the fundamental wave rotation vector formula, the formula for the two-phase electrical signal is obtained; The two-phase rotation coordinate values ​​of the fundamental positive sequence rotation vector and the two-phase rotation coordinate values ​​of the fundamental negative sequence rotation vector are stored in an array as transformation results; The step of listing equations based on the transformation result includes: The fitting function is obtained by combining the transformation result with the formula of the two-phase electrical signal; The objective function is obtained based on the transformation result and the fitting function; The equation is obtained by minimizing the objective function.

2. The method according to claim 1, characterized in that, The preset value for setting the number of data collections based on the power grid environment includes: Set the preset state of the power grid environment; Determine whether the current power grid environment meets the preset state of the power grid environment; If so, then increase the preset value; If not, then lower the preset value; the preset value is an integer not less than 1.

3. The method according to claim 1, characterized in that, The process of solving the equation to obtain the fundamental positive-sequence component and negative-sequence component of the electrical signal includes: solving the equation using the least squares method to obtain the fundamental positive-sequence component and negative-sequence component of the electrical signal.

4. An apparatus for extracting the fundamental positive-sequence component and the negative-sequence component, characterized in that, include: The unit includes a data acquisition frequency setting unit, a data acquisition unit, a coordinate system transformation unit, an equation acquisition unit, and an equation solving unit. The data collection number setting unit is used to set a preset value for the number of data collections according to the power grid environment; The acquisition unit is used to acquire the three-phase electrical signals at the current moment; The coordinate system transformation unit is used to transform the three-phase electrical signal from a three-phase coordinate system to a two-phase coordinate system and store the transformation results; The equation acquisition unit is used to list the equation based on the transformation result when the cumulative number of collections equals the preset value. The equation solving unit is used to solve the equation to obtain the fundamental positive-sequence component and negative-sequence component of the electrical signal; The coordinate system transformation unit includes: The fundamental wave rotation vector representation sub-unit is used to represent the fundamental wave rotation vector in a two-phase stationary coordinate system using the fundamental wave rotation vector formula. The two-phase formula acquisition sub-unit is used to substitute the relationship between the two-phase stationary coordinate system and the two-phase rotating coordinate system into the fundamental wave rotating vector formula to obtain the formula for the two-phase electrical signal. The storage sub-unit is used to store the two-phase rotation coordinate values ​​of the fundamental positive sequence rotation vector and the two-phase rotation coordinate values ​​of the fundamental negative sequence rotation vector as transformation results in the array; The equation acquisition unit includes: The fitting function obtains the sub-unit, which is used to combine the transformation result with the formula of the two-phase electrical signal to obtain the fitting function; The objective function acquisition sub-unit is used to obtain the objective function based on the transformation result and the fitting function; The minimum value unit is used to minimize the objective function, thus obtaining the equation.

5. The apparatus according to claim 4, characterized in that, The data collection count setting unit includes: The preset state setting subunit is used to set the preset state of the power grid environment; The judgment subunit is used to determine whether the current power grid environment meets the preset state of the power grid environment; The up-adjustment subunit is used to increase the preset value; The down-adjustment subunit is used to down-adjust the preset value; the preset value is an integer not less than 1.

6. The apparatus according to claim 4, characterized in that, The equation solving unit is used to: solve the equation using the least squares method to obtain the fundamental positive-sequence component and the negative-sequence component of the electrical signal.

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