A method for defining the aging degree of inductance based on Euclidean distance

Abstract

The present invention discloses a method for defining the aging degree of an inductance value based on Euclidean distance, comprising the following steps: step one, establishing a filter inductance circuit and a mathematical model; step two, obtaining an actual inductance value through an online inductance calculation method; step three, defining the aging degree through the Euclidean distance; and step four, evaluating the inductance value state. The present invention provides a method for defining the aging degree of an inductance value based on Euclidean distance, establishing a filter inductance circuit and a mathematical model through step one, online calculating the actual value of the filter inductance using a state equation of the actual value of the filter inductance and the nameplate value in step two, and then calculating the degree of deviation between the actual value of the filter inductance and the nameplate value through the Euclidean distance introduced in step three. Finally, in step four, defining a filter inductance aging degree and providing a calculation method thereof, thereby objectively reflecting the aging degree of the filter inductance value and providing a new method for evaluating the state of the filter inductance for operation and maintenance personnel.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a method for defining the aging degree of inductance based on Euclidean distance. Background Art

[0002] Due to the high-frequency operation of the switching devices in grid-connected converters, a large number of high-order harmonics are present in the grid-connected current. In this case, the harmonic filtering capability of the filter is particularly important, especially in the widespread application of renewable energy grid-connected converters. However, with the aging of magnetic materials, coil loss, and the influence of environmental factors such as temperature and humidity, the value of the filter inductor may shift from its original nameplate value. For grid-connected converters, the accuracy of the filter inductor value directly affects the control accuracy. Especially considering that the control parameters of current grid-connected converters are not yet fully adaptive, the aging of the filter inductor value will lead to a decrease in control accuracy and even cause control failure. At the same time, with the continuous increase in the installed capacity of renewable energy, the power grid has shown the characteristics of a weak grid. The real-time change of grid impedance also brings about control accuracy issues. However, most current methods focus on identifying the grid impedance and rarely consider the aging of the filter inductor. Therefore, more attention should be paid to studying and solving the aging problem of the filter inductor to ensure the stability and reliability of the renewable energy grid-connected converter system.

[0003] Therefore, the present invention proposes an online calculation method for filter inductance and a method for defining the aging degree of filter inductance value based on Euclidean distance. This method can not only realize the online calculation of filter inductance value, but also calculate the aging degree of filter inductance value through Euclidean distance. The value of filter inductance can be monitored in real time and evaluated according to its aging degree, so that timely measures can be taken to maintain or replace the filter inductance to ensure the stability and reliability of the system. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for defining the aging degree of inductance value based on Euclidean distance. By introducing Euclidean distance and combining it with the actual numerical value of the filter inductance for calculation and comparison, the aging degree of the filter inductance value can be objectively reflected, providing operation and maintenance personnel with a new way to evaluate the status of the filter inductance and take corresponding maintenance measures in a timely manner, thereby ensuring the stability and reliability of the system.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for defining the aging degree of inductance value based on Euclidean distance, comprising the following steps:

[0006] Step 1: Establish filter inductor circuit and mathematical model;

[0007] In the filter inductor circuit, u x1 and u x2They represent the voltage across the filter inductor, L is the actual value of the filter inductor, R is its equivalent resistance, and i x is the current flowing through the filter inductor, x = a, b, c. The filter inductor state equation (1) in the abc coordinate system is converted to the αβ coordinate system as shown in equation (2):

[0008]

[0009]

[0010] Where u α1 、u β1 u x1 Component in αβ coordinates; u α2 、u β2 u x2 Component in αβ coordinates; i α 、i β I x Components in αβ coordinates;

[0011] Step 2: Obtain the actual inductance value through the online inductance calculation method;

[0012] In step 2, by discretizing formula (2), the form of (3) can be obtained:

[0013]

[0014] Where, T s is the switching cycle;

[0015] Assume that the actual nameplate value of the filter inductor L is L m , the change is ΔL, then the actual inductance value is:

[0016] L=L m +ΔL (4)

[0017] According to the nameplate value, the mathematical model of the current at the next moment in the discrete domain can be obtained as follows:

[0018]

[0019] Combining equations (3) and (5), we can obtain:

[0020]

[0021] Arranging the equation (6) yields:

[0022]

[0023] In order to obtain a more accurate actual value of the filter inductance, the equation (7) is averaged to obtain:

[0024]

[0025] Step 3: Define the aging degree by Euclidean distance;

[0026] The n-dimensional space formula of Euclidean distance is:

[0027]

[0028] Where x i and y i They are the i-axis coordinate data of two points in n-dimensional space, i = 1, 2,…, n.

[0029] The Euclidean distance expression in two-dimensional space can be derived from formula (9):

[0030]

[0031] In order to construct the coordinates of two points in two-dimensional space, by retaining the actual filter inductance value and nameplate value at the previous sampling moment as y2 and y1 respectively, and the actual filter inductance value and nameplate value at the current moment as x2 and x1 respectively, the coordinates of the actual filter inductance value and nameplate value can be obtained as (x2, y2) and (x1, y1) respectively. Therefore, when calculating the Euclidean distance, it is equivalent to calculating the distance between the previous sampling moment and the current moment. Therefore, the Euclidean distance after substituting the actual filter inductance value and nameplate value can be expressed as:

[0032]

[0033] Where *(n-1) and *(n) represent the values ​​at the previous sampling moment and the current moment, respectively;

[0034] Step 4: Evaluate the inductance status

[0035] In order to characterize the aging degree of the filter inductor, the aging degree of the inductance value is between 0 and 100%, 0 represents the lowest aging degree, and 100% represents the highest aging degree. Therefore, the expression of the aging degree of the inductance value can be defined as:

[0036]

[0037] Preferably, in step three: Euclidean distance is a more common distance definition, which refers to the real distance between two points in n-dimensional space, or the natural length of a vector. The Euclidean distance in two-dimensional and three-dimensional space is the distance between two points. The Euclidean distance is used to measure the distance between the calculated actual filter inductance value and the nameplate value, and then the degree of inductance aging.

[0038] Preferably, in step four: the expression of the inductance aging degree corresponds the Euclidean distance and the inductance aging degree, and the degree to which the inductance value deviates from the nameplate value can be judged according to the inductance aging degree, thereby objectively reflecting the aging degree of the filter inductance value.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention provides a method for defining the aging degree of inductance value based on Euclidean distance. In step one, a filter inductance circuit and a mathematical model are established. In step two, the actual value of the filter inductance is calculated online using the state equation of the actual value of the filter inductance and the nameplate value. Then, the degree of deviation between the actual value of the filter inductance and the nameplate value is calculated using the Euclidean distance introduced in step three. Finally, in step four, a filter inductance aging degree is defined and a calculation method is given. This objectively reflects the aging degree of the filter inductance value, providing operation and maintenance personnel with a new way to evaluate the status of the filter inductance. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a circuit diagram of the filter inductor of the present invention;

[0042] Figure 2 This is the waveform for calculating the correctness of the inductance value of the present invention;

[0043] Figure 3 This is the aging waveform of the inductor when the nameplate value is 4mH; DETAILED DESCRIPTION

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0045] See also Figure 1-3 The present invention provides a technical solution: a method for defining the aging degree of inductance value based on Euclidean distance, comprising the following steps:

[0046] Step 1: Establish filter inductor circuit and mathematical model;

[0047] Step 2: Obtain the actual inductance value through the online inductance calculation method;

[0048] Step 3: Define the aging degree by Euclidean distance;

[0049] Step 4: Evaluate the inductance value status;

[0050] The method for establishing the filter inductor circuit and mathematical model in step 1 is:

[0051] Figure 1 The figure shows the filter inductor circuit diagram, in which u x1 and u x2 They represent the voltage across the filter inductor, L is the actual value of the filter inductor, R is its equivalent resistance, and i x is the current flowing through the filter inductor, x = a, b, c.

[0052] The filter inductance state equation (1) in the abc coordinate system is converted to the αβ coordinate system as shown in equation (2).

[0053]

[0054]

[0055] Where u α1 、u β1 u x1 Component in αβ coordinates; u α2 、u β2 u x2 Component in αβ coordinates; i α 、i β I x Components in αβ coordinates.

[0056] In step 2, the actual inductance value is obtained by the online inductance calculation method, which specifically includes:

[0057] Discretizing formula (2), we can get the form of (3):

[0058]

[0059] Where, T s is the switching cycle.

[0060] Assume that the actual nameplate value of the filter inductor L is L m , the change is ΔL, then the actual inductance value is:

[0061] L=L m +ΔL (4)

[0062] According to the nameplate value, the mathematical model of the current at the next moment in the discrete domain can be obtained as follows:

[0063]

[0064] Combining equations (3) and (5), we can obtain:

[0065]

[0066] By rearranging the equation (6), we can obtain:

[0067]

[0068] In order to obtain a more accurate actual value of the filter inductance, the equation (7) is averaged to obtain:

[0069]

[0070] In step 3, the aging degree is defined by the Euclidean distance, which specifically includes:

[0071] Euclidean distance is a common distance definition, referring to the true distance between two points in n-dimensional space, or the natural length of a vector. Euclidean distance in two-dimensional and three-dimensional space is simply the distance between two points. This invention uses Euclidean distance to measure the distance between the calculated actual filter inductance and the nameplate value, thereby determining the degree of inductor aging.

[0072] The n-dimensional space formula of Euclidean distance is:

[0073]

[0074] Where x i and y i They are the i-axis coordinate data of two points in n-dimensional space, i = 1, 2,…, n.

[0075] The Euclidean distance expression in two-dimensional space can be derived from formula (9):

[0076]

[0077] In order to construct the coordinates of two points in two-dimensional space, the present invention retains the actual filter inductance value and nameplate value at the previous sampling moment as y2 and y1 respectively, and the actual filter inductance value and nameplate value at the current moment as x2 and x1 respectively, so that the coordinates of the actual filter inductance value and nameplate value can be obtained as (x2, y2) and (x1, y1) respectively. Therefore, when calculating the Euclidean distance, it is equivalent to calculating the distance between the previous sampling moment and the current moment. Therefore, the Euclidean distance after substituting the actual filter inductance value and nameplate value can be expressed as:

[0078]

[0079] Where *(n-1) and *(n) represent the values ​​at the previous sampling moment and the current moment, respectively.

[0080] The evaluation of the inductance value in step 4 specifically includes:

[0081] In order to characterize the aging degree of the filter inductor, the aging degree of the inductance value is between 0 and 100%, 0 represents the lowest aging degree, and 100% represents the highest aging degree. Therefore, the expression of the aging degree of the inductance value can be defined as:

[0082]

[0083] Formula (11) corresponds the Euclidean distance to the aging degree of the inductance value. According to the aging degree of the inductance value, the degree to which the inductance value deviates from the nameplate value can be judged, thereby objectively reflecting the aging degree of the filter inductance value, providing operation and maintenance personnel with a new way to evaluate the status of the filter inductance.

[0084] In the present invention: Figure 2 This is the calculation result obtained by the calculation method of the actual value of the filter inductance described in the present invention. It can be seen from the waveform that the proposed algorithm can accurately calculate the actual value of the filter inductance with extremely small error and short dynamic process time.

[0085] In the present invention: Figure 3 When the nameplate value is set to 4mH, according to Figure 2 The degree of inductance aging is calculated based on the actual inductance value. It can be seen from the figure that the larger the actual inductance value is, the lower the degree of aging is, and the greater the deviation of the actual inductance value from the nameplate value is, the higher the degree of aging is, which proves the effectiveness of the method described in the present invention.

[0086] In summary, the Euclidean distance-based inductance aging degree definition method establishes a filter inductance circuit and a mathematical model in step one, calculates the actual filter inductance value online using the state equation of the actual filter inductance value and the nameplate value in step two, and then calculates the degree of deviation between the actual filter inductance value and the nameplate value using the Euclidean distance introduced in step three. Finally, in step four, a filter inductance aging degree is defined and its calculation method is given, thereby objectively reflecting the aging degree of the filter inductance value and providing an entirely new way for operation and maintenance personnel to evaluate the status of the filter inductance.

[0087] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0088] The electrical components mentioned in this article are all connected to an external main controller and 220V AC power, and the main controller can be a conventional known device that performs control such as a computer.

[0089] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for defining the aging degree of inductance based on Euclidean distance, characterized in that: The steps include: Step 1: Establish filter inductor circuit and mathematical model; In the filter inductor circuit, u x1 and u x2 They represent the voltage across the filter inductor, L is the actual value of the filter inductor, R is its equivalent resistance, and i x is the current flowing through the filter inductor, x = a, b, c. The filter inductor state equation (1) in the abc coordinate system is converted to the αβ coordinate system as shown in equation (2): Where u α1 、u β1 u x1 Component in αβ coordinates; u α2 、u β2 u x2 Component in αβ coordinates; i α 、i β I x Components in αβ coordinates; Step 2: Obtain the actual inductance value through the online inductance calculation method; In step 2, by discretizing formula (2), the form of (3) can be obtained: Where, T s is the switching cycle; Assume that the actual nameplate value of the filter inductor L is L m , the change is ΔL, then the actual inductance value is: L=L m +ΔL (4) According to the nameplate value, the mathematical model of the current at the next moment in the discrete domain can be obtained as follows: Combining equations (3) and (5), we can get: i α By rearranging the equation (6), we can obtain: In order to obtain a more accurate actual value of the filter inductance, the equation (7) is averaged to obtain: Step 3: Define the aging degree by Euclidean distance; The n-dimensional space formula of Euclidean distance is: Where x i and y i are the i-axis coordinate data of two points in n-dimensional space, i = 1, 2, ..., n; The Euclidean distance expression in two-dimensional space is derived from formula (9): In order to construct the coordinates of two points in two-dimensional space, by retaining the actual filter inductance value and nameplate value at the previous sampling moment as y2 and y1 respectively, and the actual filter inductance value and nameplate value at the current moment as x2 and x1 respectively, the coordinates of the actual filter inductance value and nameplate value are obtained as (x2, y2) and (x1, y1) respectively. Therefore, when calculating the Euclidean distance, it is equivalent to calculating the distance between the previous sampling moment and the current moment. Therefore, the Euclidean distance after substituting the actual filter inductance value and nameplate value is expressed as: Where *(n-1) and *(n) represent the values ​​at the previous sampling moment and the current moment, respectively; Step 4: Evaluate the inductance status In order to characterize the aging degree of the filter inductor, the aging degree of the inductance value is between 0 and 100%, 0 represents the lowest aging degree, and 100% represents the highest aging degree. Therefore, the expression of the aging degree of the inductance value is defined as:

2. The method for defining the aging degree of inductance value based on Euclidean distance according to claim 1, characterized in that: In step three, Euclidean distance is a common distance definition, which refers to the true distance between two points in n-dimensional space, or the natural length of a vector. In two-dimensional and three-dimensional space, the Euclidean distance is the distance between two points. The Euclidean distance is used to measure the distance between the calculated actual filter inductance value and the nameplate value, thereby reflecting the degree of inductance aging.

3. The method for defining the aging degree of inductance value based on Euclidean distance according to claim 1, characterized in that: In the step 4, the expression for the degree of inductance aging corresponds the Euclidean distance to the degree of inductance aging, and the degree to which the inductance value deviates from the nameplate value is determined according to the degree of inductance aging, thereby objectively reflecting the degree of aging of the filter inductance value.

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