Calculation method and system for comprehensive quality value of electric energy when offshore wind farm is connected to the grid

Abstract

The present application proposes a method and system for calculating the comprehensive quality value of electric energy when an offshore wind farm is connected to the grid. The method includes: adjusting the harmonic current index data according to the pulsation number of the converter of the wind turbine group in the offshore wind farm to obtain the adjusted harmonic current; based on the degree of influence of the acquired index data on the power quality, allocating weights corresponding to the adjusted harmonic current, the total distortion rate of the harmonic voltage, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data; and then calculating the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid. The technical solution proposed in the present application adjusts the harmonic current index data according to the pulsation number of the converter of the wind turbine group, and at the same time allocates weights corresponding to each index data based on the degree of influence of the index data on the power quality, determines the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid, and thus can accurately, simply and intuitively judge the quality of the grid connection.

Description

Technical Field

[0001] The present application relates to the field of comprehensive power quality, and in particular to a method and system for calculating the comprehensive power quality value when an offshore wind farm is connected to the grid. Background Art

[0002] The various indicators of power quality are one of the important parameters that reflect the friendly connection of offshore wind farms to the grid. The indicators that need to be calculated include the harmonic currents injected into the public connection point of the grid by the offshore wind farm, the total distortion rate of harmonic voltage, the voltage fluctuations and voltage flicker caused, and the three-phase imbalance. If the offshore wind farm is in the planning access system stage, it is necessary to carry out detailed analysis and calculation of various indicators, and then compare them with the allowable values ​​required by the national standard for power quality. If it does not exceed the national standard requirements, the access conditions are met. If it does not meet the national standard requirements, it is necessary to carry out additional special research on governance; if the offshore wind farm has been put into operation and connected to the grid, it is necessary to carry out actual measurement work and compare the test results with the allowable values ​​required by the national standard. In this context, the evaluation results of various power quality indicators are combined, and a comprehensive power quality indicator is used to represent the friendliness of the connection to the grid of a single offshore wind farm. It can provide a simple and intuitive evaluation result of the friendliness of the connection to the grid, which is of great significance.

[0003] However, the existing assessment of grid-connected power quality indicators for individual offshore wind farms is to carry out calculation and analysis of indicators such as harmonics, fluctuations, flicker and three-phase imbalance. When assessing the grid-connected power quality of offshore wind farms, it is only checked whether it meets the national standards. If it meets the requirements, it can be connected to the grid. If it does not meet the requirements, treatment measures are studied, resulting in inaccurate and non-intuitive judgments on the grid-connected power quality of offshore wind farms. Summary of the invention

[0004] The present application provides a method and system for calculating the comprehensive quality value of electric energy when an offshore wind farm is connected to the grid, so as to at least solve the technical problem of inaccurate and unintuitive judgment on the quality of electric energy connected to the offshore wind farm.

[0005] The first embodiment of the present application provides a method for calculating the comprehensive quality value of electric energy when an offshore wind farm is connected to the grid, the method comprising:

[0006] Obtain the corresponding harmonic current, total harmonic voltage distortion rate, voltage fluctuation, voltage flicker and three-phase current imbalance index data when the offshore wind farm is connected to the grid;

[0007] Adjusting the harmonic current index data according to the pulsation number of the converter of the wind turbine set in the offshore wind farm to obtain adjusted harmonic current index data;

[0008] Based on the degree of influence of the acquired index data on power quality, weights corresponding to the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data are allocated;

[0009] The comprehensive quality value of electric energy when the offshore wind farm is connected to the grid is calculated based on the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data and the weights corresponding to the index data.

[0010] Preferably, the acquisition of harmonic current, total harmonic voltage distortion rate, voltage fluctuation, voltage flicker and three-phase current imbalance index data corresponding to the offshore wind farm being connected to the grid includes:

[0011] Obtaining the true value of harmonic current, the true value of total harmonic voltage distortion rate, the true value of voltage fluctuation, the true value of voltage flicker and the true value of three-phase current unbalance corresponding to the offshore wind farm when it is connected to the grid, and the harmonic current threshold, the total harmonic voltage distortion rate threshold, the voltage fluctuation threshold, the voltage flicker threshold and the three-phase current unbalance threshold corresponding to the offshore wind farm when it is connected to the grid;

[0012] The ratios of the true value and the corresponding threshold value are respectively obtained, and the ratios of each true value and the corresponding threshold value are used as the indicator data.

[0013] Preferably, the harmonic current index data is adjusted according to the pulsation number of the converter of the wind turbine in the offshore wind farm to obtain the adjusted harmonic current index data, including:

[0014] Determining the types of each multiple harmonic in the harmonic current corresponding to the harmonic current index data according to the pulsation number of the converter of the wind turbine in the offshore wind farm, wherein the types of the multiple harmonics include characteristic multiple harmonics and non-characteristic multiple harmonics;

[0015] Determining the number of each type of multiple harmonics, and determining an adjustment coefficient of each multiple harmonic based on the number of each type of multiple harmonics;

[0016] The harmonic current index data is adjusted based on the adjustment coefficients of the multiple harmonics to obtain adjusted harmonic current index data.

[0017] Preferably, the weights corresponding to the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data are allocated based on the degree of influence of the acquired index data on the power quality, including:

[0018] The weight corresponding to the adjusted harmonic current index data is allocated to 30%;

[0019] The weight corresponding to the harmonic voltage total distortion rate index data is allocated to 20%;

[0020] Allocate the weight corresponding to the voltage fluctuation index data to 30%;

[0021] The weight corresponding to the voltage flicker index data is allocated to 10%;

[0022] The weight corresponding to the three-phase current imbalance index data is allocated to 10%.

[0023] Further, the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid is calculated according to the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data and the weights corresponding to the index data, including:

[0024] Respectively obtain the adjusted harmonic current index data and its corresponding weight product value, the harmonic voltage total distortion rate index data and its corresponding weight product value, the voltage fluctuation and its corresponding weight product value, the voltage flicker and its corresponding weight product value, and the three-phase current unbalance and its corresponding weight product value;

[0025] The product values ​​are added together to obtain the sum of the product values, and the sum of the product values ​​is used as the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid.

[0026] Furthermore, if there is a ratio greater than 1 among the ratio of the true value of the harmonic current to the harmonic current threshold, the ratio of the true value of the total harmonic voltage distortion rate to the total harmonic voltage distortion rate threshold, the ratio of the true value of the voltage fluctuation to the voltage fluctuation threshold, the ratio of the true value of the voltage flicker to the voltage flicker threshold, and the ratio of the true value of the three-phase current imbalance to the three-phase current imbalance threshold, then the comprehensive electric energy quality value of the offshore wind farm when it is connected to the grid is equal to 1.

[0027] Furthermore, the method further comprises:

[0028] Determine the grid connection quality level corresponding to the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid;

[0029] Based on the grid-connected friendliness level corresponding to the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid, the grid-connected friendliness of the offshore wind farm is displayed.

[0030] The second embodiment of the present application provides a system for calculating the comprehensive quality value of electric energy when an offshore wind farm is connected to the grid, comprising:

[0031] An acquisition module is used to obtain the corresponding harmonic current, total harmonic voltage distortion rate, voltage fluctuation, voltage flicker and three-phase current imbalance index data when the offshore wind farm is connected to the grid;

[0032] An adjustment module, used for adjusting the harmonic current index data according to the pulsation number of the converter of the wind turbine set in the offshore wind farm to obtain adjusted harmonic current index data;

[0033] An allocation module, configured to allocate weights corresponding to the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data based on the degree of influence of the acquired index data on the power quality;

[0034] A calculation module is used to calculate the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid based on the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data and the weights corresponding to the various index data.

[0035] Preferably, the acquisition module includes:

[0036] A first acquisition unit is used to acquire the corresponding harmonic current true value, harmonic voltage total distortion rate true value, voltage fluctuation true value, voltage flicker true value and three-phase current unbalance true value when the offshore wind farm is connected to the grid, and the corresponding harmonic current threshold, harmonic voltage total distortion rate threshold, voltage fluctuation threshold, voltage flicker threshold and three-phase current unbalance threshold when the offshore wind farm is connected to the grid;

[0037] The second acquisition unit is used to respectively acquire the ratio of the true value to the corresponding threshold value, and use the ratio of each true value to the corresponding threshold value as the indicator data.

[0038] Preferably, the adjustment module includes:

[0039] A first determining unit is used to determine the types of multiple harmonics in the harmonic current corresponding to the harmonic current index data according to the pulsation number of the converter of the wind turbine group in the offshore wind farm, wherein the types of the multiple harmonics include characteristic multiple harmonics and non-characteristic multiple harmonics;

[0040] A second determining unit, configured to determine the number of each type of multiple harmonics, and determine an adjustment coefficient of each multiple harmonic based on the number of each type of multiple harmonics;

[0041] The adjustment unit is used to adjust the harmonic current index data based on the adjustment coefficient of each multiple harmonic to obtain the adjusted harmonic current index data.

[0042] Preferably, the allocation module is used for:

[0043] The weight corresponding to the adjusted harmonic current index data is allocated to 30%;

[0044] The weight corresponding to the harmonic voltage total distortion rate index data is allocated to 20%;

[0045] Allocate the weight corresponding to the voltage fluctuation index data to 30%;

[0046] The weight corresponding to the voltage flicker index data is allocated to 10%;

[0047] The weight corresponding to the three-phase current imbalance index data is allocated to 10%.

[0048] Preferably, the calculation module includes:

[0049] A third acquisition unit is used to respectively acquire the adjusted harmonic current index data and its corresponding weight product value, the harmonic voltage total distortion rate index data and its corresponding weight product value, the voltage fluctuation and its corresponding weight product value, the voltage flicker and its corresponding weight product value, and the three-phase current unbalance and its corresponding weight product value;

[0050] The calculation unit is used to add the product values ​​to obtain the sum of the product values, and use the sum of the product values ​​as the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid.

[0051] Furthermore, if there is a ratio greater than 1 among the ratio of the true value of the harmonic current to the harmonic current threshold, the ratio of the true value of the total harmonic voltage distortion rate to the total harmonic voltage distortion rate threshold, the ratio of the true value of the voltage fluctuation to the voltage fluctuation threshold, the ratio of the true value of the voltage flicker to the voltage flicker threshold, and the ratio of the true value of the three-phase current imbalance to the three-phase current imbalance threshold, then the comprehensive electric energy quality value of the offshore wind farm when it is connected to the grid is equal to 1.

[0052] Furthermore, the system also includes:

[0053] A determination module, used to determine the grid connection quality level corresponding to the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid;

[0054] The display module is used to display the friendliness of the offshore wind farm when it is connected to the grid based on the grid connection friendliness level corresponding to the comprehensive quality value of the electric energy when the offshore wind farm is connected to the grid.

[0055] The technical solution provided by the embodiments of the present application brings at least the following beneficial effects:

[0056] The present application proposes a method and system for calculating the comprehensive quality value of electric energy when an offshore wind farm is connected to the grid. The method includes: obtaining harmonic current, total harmonic voltage distortion rate, voltage fluctuation, voltage flicker and three-phase current imbalance index data corresponding to the offshore wind farm when the offshore wind farm is connected to the grid; adjusting the harmonic current index data according to the pulsation number of the converter of the wind turbine group in the offshore wind farm to obtain adjusted harmonic current index data; allocating weights corresponding to the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data based on the degree of influence of the acquired index data on the power quality; calculating the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid according to the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data and the weights corresponding to the index data. The technical solution proposed in this application adjusts the harmonic current index data according to the pulsation number of the converter of the wind turbine set, and at the same time allocates the weight corresponding to each index data based on the degree of influence of the index data on the power quality, determines the comprehensive power quality value when the offshore wind farm is connected to the grid, and then can accurately, simply and intuitively judge the quality of the grid connection.

[0057] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0059] Figure 1 A flow chart of a method for calculating the comprehensive quality value of electric energy when an offshore wind farm is connected to the grid according to an embodiment of the present application;

[0060] Figure 2 A first structural diagram of a system for calculating the comprehensive quality value of electric energy when an offshore wind farm is connected to the grid according to an embodiment of the present application;

[0061] Figure 3 A structural diagram of an acquisition module in a calculation system for comprehensive quality value of electric energy when an offshore wind farm is connected to the grid according to an embodiment of the present application;

[0062] Figure 4 A structural diagram of an adjustment module in a calculation system for a comprehensive quality value of electric energy when an offshore wind farm is connected to the grid according to an embodiment of the present application;

[0063] Figure 5 A structural diagram of a calculation module in a calculation system for a comprehensive quality value of electric energy when an offshore wind farm is connected to the grid according to an embodiment of the present application;

[0064] Figure 6 This is a second structural diagram of a system for calculating the comprehensive quality value of electric energy when an offshore wind farm is connected to the grid according to an embodiment of the present application. DETAILED DESCRIPTION

[0065] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0066] The present application proposes a method and system for calculating the comprehensive quality value of electric energy when an offshore wind farm is connected to the grid. The method comprises: obtaining harmonic current, total harmonic voltage distortion rate, voltage fluctuation, voltage flicker and three-phase current imbalance index data corresponding to the offshore wind farm when the offshore wind farm is connected to the grid; adjusting the harmonic current index data according to the pulsation number of the converter of the wind turbine group in the offshore wind farm to obtain adjusted harmonic current index data; allocating weights corresponding to the adjusted harmonic current, total harmonic voltage distortion rate, voltage fluctuation, voltage flicker and three-phase current imbalance index data based on the degree of influence of the acquired index data on the electric energy quality; calculating the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid according to the adjusted harmonic current, total harmonic voltage distortion rate, voltage fluctuation, voltage flicker and three-phase current imbalance index data and the weights corresponding to the index data. The technical solution proposed in this application adjusts the harmonic current index data according to the pulsation number of the converter of the wind turbine set, and at the same time allocates the weight corresponding to each index data based on the degree of influence of the index data on the power quality, determines the comprehensive power quality value when the offshore wind farm is connected to the grid, and then can accurately, simply and intuitively judge the quality of the grid connection.

[0067] The following describes a method and system for calculating the comprehensive quality value of electric energy when an offshore wind farm is connected to the grid in an embodiment of the present application with reference to the accompanying drawings.

[0068] Embodiment 1

[0069] Figure 1 The flowchart of a method for calculating the comprehensive quality value of electric energy when an offshore wind farm is connected to the grid according to one embodiment of the present application is as follows: Figure 1 As shown, the method includes:

[0070] Step 1: Obtain the corresponding harmonic current, total harmonic voltage distortion rate, voltage fluctuation, voltage flicker and three-phase current imbalance index data when the offshore wind farm is connected to the grid;

[0071] It should be noted that the step 1 specifically includes:

[0072] Obtaining the true value of harmonic current, the true value of total harmonic voltage distortion rate, the true value of voltage fluctuation, the true value of voltage flicker and the true value of three-phase current unbalance corresponding to the offshore wind farm when it is connected to the grid, and the harmonic current threshold, the total harmonic voltage distortion rate threshold, the voltage fluctuation threshold, the voltage flicker threshold and the three-phase current unbalance threshold corresponding to the offshore wind farm when it is connected to the grid;

[0073] The ratios of the true value and the corresponding threshold value are respectively obtained, and the ratios of each true value and the corresponding threshold value are used as the indicator data.

[0074] It should be noted that if there is a ratio greater than 1 among the ratio of the true value of the harmonic current to the harmonic current threshold, the ratio of the true value of the total harmonic voltage distortion rate to the total harmonic voltage distortion rate threshold, the ratio of the true value of the voltage fluctuation to the voltage fluctuation threshold, the ratio of the true value of the voltage flicker to the voltage flicker threshold, and the ratio of the true value of the three-phase current imbalance to the three-phase current imbalance threshold, then the comprehensive quality value of the electric energy when the offshore wind farm is connected to the grid is equal to 1.

[0075] Step 2: adjusting the harmonic current index data according to the pulsation number of the converter of the wind turbine generator set in the offshore wind farm to obtain adjusted harmonic current index data;

[0076] In the embodiment of the present disclosure, step 2 specifically includes:

[0077] Determining the types of each multiple harmonic in the harmonic current corresponding to the harmonic current index data according to the pulsation number of the converter of the wind turbine in the offshore wind farm, wherein the types of the multiple harmonics include characteristic multiple harmonics and non-characteristic multiple harmonics;

[0078] Determining the number of each type of multiple harmonics, and determining an adjustment coefficient of each multiple harmonic based on the number of each type of multiple harmonics;

[0079] The harmonic current index data is adjusted based on the adjustment coefficients of the multiple harmonics to obtain adjusted harmonic current index data.

[0080] For example, the adjustment coefficients of the harmonic current index data of the 2nd to 25th order are determined. If there are higher-order harmonic current index data, they can be reflected in the total harmonic voltage distortion rate. The adjustment coefficients of each harmonic current need to be determined according to the type of the main equipment of the converter of the offshore wind turbine. For the double-fed converter and the full-power converter, if the converter is an n-pulse converter, first calculate the integer number k of the characteristic harmonics contained in the 25th harmonic current; for example: if n=6, then k=4; n=12, then k=2; secondly, allocate 50% of the adjustment coefficient to the harmonic current of the characteristic order, and allocate 50% of the adjustment coefficient to the harmonic current of the non-characteristic order; thirdly, each harmonic current of the characteristic order is evenly divided into 50% of the adjustment coefficient, and each harmonic current of the non-characteristic order is also evenly divided into 50% of the adjustment coefficient. For example: if n=6, k=4, the total 8 harmonic currents of kn±1 are evenly allocated an adjustment factor of 50%, among which the 5th / 7th / 11th / 13th / 17th / 19th / 23rd / 25th harmonic currents are each allocated an adjustment factor of 50% / 8=6.25%, and the remaining harmonic currents are allocated an adjustment factor of 50% / 16=3.125%.

[0081] Step 3: Based on the degree of influence of the acquired index data on power quality, weights corresponding to the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data are allocated;

[0082] In the embodiment of the present disclosure, step 3 specifically includes:

[0083] The weight corresponding to the adjusted harmonic current index data is allocated to 30%;

[0084] The weight corresponding to the harmonic voltage total distortion rate index data is allocated to 20%;

[0085] Allocate the weight corresponding to the voltage fluctuation index data to 30%;

[0086] The weight corresponding to the voltage flicker index data is allocated to 10%;

[0087] The weight corresponding to the three-phase current imbalance index data is allocated to 10%.

[0088] For example, at present, the power quality indicators that need to be calculated for offshore wind farms to be connected to the grid include five categories, namely harmonic current, total harmonic voltage distortion rate, voltage fluctuation, voltage flicker and three-phase current imbalance. When allocating the weights of each indicator data, it is necessary to determine according to the power quality problems caused by offshore wind power, and it is necessary to focus on harmonic and voltage fluctuation indicators. Therefore, the weights of the indicator data are allocated as follows: 30% weight is allocated to harmonic current, 20% weight is allocated to total harmonic voltage distortion rate, 30% weight is allocated to voltage fluctuation, and 10% weight is allocated to voltage flicker and three-phase current imbalance respectively. Among them, the weight allocation method of each harmonic current described in the first point is to allocate the total harmonic current index as 100%. When determining the grid connection quality index, after the harmonic current index data is calculated in the first point, it is recalculated according to the weight of 30%.

[0089] Step 4: Calculate the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid based on the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data and the weights corresponding to the index data.

[0090] In the embodiment of the present disclosure, step 4 specifically includes:

[0091] Respectively obtain the adjusted harmonic current index data and its corresponding weight product value, the harmonic voltage total distortion rate index data and its corresponding weight product value, the voltage fluctuation and its corresponding weight product value, the voltage flicker and its corresponding weight product value, and the three-phase current unbalance and its corresponding weight product value;

[0092] The product values ​​are added together to obtain the sum of the product values, and the sum of the product values ​​is used as the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid.

[0093] For example, the comprehensive quality value of electric energy = harmonic current*30%+total harmonic voltage distortion rate*20%+voltage fluctuation*30%+voltage flicker*10%+three-phase current unbalance*10%.

[0094] Furthermore, the method provided in this embodiment may also include:

[0095] Determine the grid connection quality level corresponding to the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid;

[0096] Based on the grid-connected friendliness level corresponding to the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid, the grid-connected friendliness of the offshore wind farm is displayed.

[0097] It should be noted that the power quality and network quality levels include: first level, second level and third level, among which the first level indicates that the power quality and network quality are relatively good, represented by green; the second level indicates that the power quality and network quality are moderate, represented by yellow; the third level indicates that the power quality indicators exceed the standard, represented by red.

[0098] Furthermore, the range of the comprehensive power quality value corresponding to the first level is greater than or equal to zero and less than or equal to seventy percent; the range of the comprehensive power quality value corresponding to the second level is greater than seventy percent and less than one hundred percent; the range of the comprehensive power quality value corresponding to the third level is greater than or equal to one hundred percent.

[0099] In summary, the method for calculating the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid proposed in this embodiment adjusts the harmonic current index data according to the pulsation number of the converter of the wind turbine group, and at the same time allocates the weight corresponding to each index data based on the degree of influence of the index data on the power quality, and determines the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid, thereby accurately, simply and intuitively judging the quality of the grid connection.

[0100] Embodiment 2

[0101] Figure 2 A core damage frequency calculation system based on a nuclear power plant production task is provided according to an embodiment of the present application, such as Figure 2 As shown, including:

[0102] The acquisition module 100 is used to obtain the corresponding harmonic current, total harmonic voltage distortion rate, voltage fluctuation, voltage flicker and three-phase current imbalance index data when the offshore wind farm is connected to the grid;

[0103] An adjustment module 200, configured to adjust the harmonic current index data according to the pulsation number of the converter of the wind turbine in the offshore wind farm to obtain adjusted harmonic current index data;

[0104] An allocation module 300, configured to allocate weights corresponding to the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data based on the degree of influence of the acquired index data on the power quality;

[0105] The calculation module 400 is used to calculate the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid based on the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data and the weights corresponding to the index data.

[0106] In the embodiments of the present disclosure, Figure 3 As shown, the acquisition module 100 includes:

[0107] The first acquisition unit 101 is used to acquire the corresponding harmonic current true value, harmonic voltage total distortion rate true value, voltage fluctuation true value, voltage flicker true value and three-phase current unbalance true value when the offshore wind farm is connected to the grid, and the corresponding harmonic current threshold, harmonic voltage total distortion rate threshold, voltage fluctuation threshold, voltage flicker threshold and three-phase current unbalance threshold when the offshore wind farm is connected to the grid;

[0108] The second acquisition unit 102 is used to respectively acquire the ratio of the true value to the corresponding threshold value, and use the ratio of each true value to the corresponding threshold value as the indicator data.

[0109] In the embodiments of the present disclosure, Figure 4 As shown, the adjustment module 200 includes:

[0110] A first determining unit 201 is used to determine the types of multiple harmonics in the harmonic current corresponding to the harmonic current index data according to the pulsation number of the converter of the wind turbine group in the offshore wind farm, wherein the types of multiple harmonics include characteristic multiple harmonics and non-characteristic multiple harmonics;

[0111] A second determining unit 202, configured to determine the number of multiple harmonics of each type, and determine an adjustment coefficient of each multiple harmonic based on the number of multiple harmonics of each type;

[0112] The adjustment unit 203 is used to adjust the harmonic current index data based on the adjustment coefficient of each multiple harmonic to obtain adjusted harmonic current index data.

[0113] In the embodiment of the present disclosure, the allocation module 300 is used to:

[0114] The weight corresponding to the adjusted harmonic current index data is allocated to 30%;

[0115] The weight corresponding to the harmonic voltage total distortion rate index data is allocated to 20%;

[0116] Allocate the weight corresponding to the voltage fluctuation index data to 30%;

[0117] The weight corresponding to the voltage flicker index data is allocated to 10%;

[0118] The weight corresponding to the three-phase current imbalance index data is allocated to 10%.

[0119] In the embodiments of the present disclosure, Figure 5 As shown, the calculation module 400 includes:

[0120] The third acquisition unit 401 is used to respectively acquire the adjusted harmonic current index data and its corresponding weight product value, the harmonic voltage total distortion rate index data and its corresponding weight product value, the voltage fluctuation and its corresponding weight product value, the voltage flicker and its corresponding weight product value, and the three-phase current unbalance and its corresponding weight product value;

[0121] The calculation unit 402 is used to add the product values ​​to obtain the sum of the product values, and use the sum of the product values ​​as the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid.

[0122] Furthermore, if there is a ratio greater than 1 among the ratio of the true value of the harmonic current to the harmonic current threshold, the ratio of the true value of the total harmonic voltage distortion rate to the total harmonic voltage distortion rate threshold, the ratio of the true value of the voltage fluctuation to the voltage fluctuation threshold, the ratio of the true value of the voltage flicker to the voltage flicker threshold, and the ratio of the true value of the three-phase current imbalance to the three-phase current imbalance threshold, then the comprehensive electric energy quality value of the offshore wind farm when it is connected to the grid is equal to 1.

[0123] Further, such as Figure 6 As shown, the system also includes:

[0124] A determination module 500 is used to determine a grid connection quality level corresponding to the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid;

[0125] The display module 600 is used to display the friendliness of the offshore wind farm when it is connected to the grid based on the grid-connected friendliness level corresponding to the comprehensive quality value of the electric energy when the offshore wind farm is connected to the grid.

[0126] In summary, the calculation system of the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid proposed in this embodiment, this calculation system adjusts the harmonic current index data according to the pulsation number of the converter of the wind turbine, and at the same time allocates the weight corresponding to each index data based on the degree of influence of the index data on the power quality, determines the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid, and then can accurately, simply and intuitively judge the quality of the grid connection.

[0127] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0128] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0129] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for calculating the comprehensive quality value of electric energy when an offshore wind farm is connected to the grid, characterized in that: The method comprises: Obtain the corresponding harmonic current, total harmonic voltage distortion rate, voltage fluctuation, voltage flicker and three-phase current imbalance index data when the offshore wind farm is connected to the grid; Adjusting the harmonic current index data according to the pulsation number of the converter of the wind turbine generator set in the offshore wind farm to obtain adjusted harmonic current index data; Based on the degree of influence of the acquired index data on power quality, weights corresponding to the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data are allocated; Calculate the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid according to the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data and the weights corresponding to the index data; The step of adjusting the harmonic current index data according to the pulsation number of the converter of the wind turbine generator set in the offshore wind farm to obtain the adjusted harmonic current index data includes: Determining the types of each multiple harmonic in the harmonic current corresponding to the harmonic current index data according to the pulsation number of the converter of the wind turbine in the offshore wind farm, wherein the types of the multiple harmonics include characteristic multiple harmonics and non-characteristic multiple harmonics; Determining the number of each type of multiple harmonics, and determining an adjustment coefficient of each multiple harmonic based on the number of each type of multiple harmonics; Adjusting the harmonic current index data based on the adjustment coefficients of each multiple harmonic to obtain adjusted harmonic current index data; Specifically, it includes: first, calculating the integer order of characteristic harmonics contained in the harmonic current; second, allocating 50% adjustment coefficient to the harmonic current of characteristic order, and allocating 50% adjustment coefficient to the harmonic current of non-characteristic order; third, all harmonic currents of characteristic order are equally divided into 50% adjustment coefficient, and all harmonic currents of non-characteristic order are also equally divided into 50% adjustment coefficient.

2. The method according to claim 1, characterized in that The acquisition of the corresponding harmonic current, harmonic voltage total distortion rate, voltage fluctuation, voltage flicker and three-phase current imbalance index data when the offshore wind farm is connected to the grid includes: Obtaining the true value of harmonic current, the true value of total harmonic voltage distortion rate, the true value of voltage fluctuation, the true value of voltage flicker and the true value of three-phase current unbalance corresponding to the offshore wind farm when it is connected to the grid, and the harmonic current threshold, the total harmonic voltage distortion rate threshold, the voltage fluctuation threshold, the voltage flicker threshold and the three-phase current unbalance threshold corresponding to the offshore wind farm when it is connected to the grid; The ratios of the true value and the corresponding threshold value are respectively obtained, and the ratios of each true value and the corresponding threshold value are used as the indicator data.

3. The method according to claim 1, characterized in that The method allocates weights corresponding to the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data based on the degree of influence of the acquired index data on the power quality, including: The weight corresponding to the adjusted harmonic current index data is allocated to 30%; The weight corresponding to the harmonic voltage total distortion rate index data is allocated to 20%; Allocate the weight corresponding to the voltage fluctuation index data to 30%; The weight corresponding to the voltage flicker index data is allocated to 10%; The weight corresponding to the three-phase current imbalance index data is allocated to 10%.

4. The method according to claim 3, characterized in that The calculating of the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid according to the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data and the weights corresponding to the index data includes: Respectively obtain the adjusted harmonic current index data and its corresponding weight product value, the harmonic voltage total distortion rate index data and its corresponding weight product value, the voltage fluctuation and its corresponding weight product value, the voltage flicker and its corresponding weight product value, and the three-phase current unbalance and its corresponding weight product value; The product values ​​are added together to obtain the sum of the product values, and the sum of the product values ​​is used as the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid.

5. The method according to claim 2, characterized in that If there is a ratio greater than 1 among the ratio of the true value of the harmonic current to the harmonic current threshold, the ratio of the true value of the total harmonic voltage distortion rate to the total harmonic voltage distortion rate threshold, the ratio of the true value of the voltage fluctuation to the voltage fluctuation threshold, the ratio of the true value of the voltage flicker to the voltage flicker threshold, and the ratio of the true value of the three-phase current imbalance to the three-phase current imbalance threshold, then the comprehensive quality value of the electric energy when the offshore wind farm is connected to the grid is equal to 1.

6. The method according to claim 4 or 5, characterized in that The method further comprises: Determine the grid connection quality level corresponding to the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid; Based on the grid-connected friendliness level corresponding to the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid, the grid-connected friendliness of the offshore wind farm is displayed.

7. A system for calculating the comprehensive quality value of electric energy when an offshore wind farm is connected to the grid, characterized in that: include: An acquisition module is used to obtain the corresponding harmonic current, total harmonic voltage distortion rate, voltage fluctuation, voltage flicker and three-phase current imbalance index data when the offshore wind farm is connected to the grid; An adjustment module, used for adjusting the harmonic current index data according to the pulsation number of the converter of the wind turbine set in the offshore wind farm to obtain adjusted harmonic current index data; An allocation module, configured to allocate weights corresponding to the adjusted harmonic current, the total harmonic voltage distortion rate, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data based on the degree of influence of the acquired index data on the power quality; A calculation module, used to calculate the comprehensive quality value of electric energy when the offshore wind farm is connected to the grid according to the adjusted harmonic current, the total distortion rate of the harmonic voltage, the voltage fluctuation, the voltage flicker and the three-phase current imbalance index data and the weights corresponding to the index data; The adjustment module comprises: A first determining unit is used to determine the types of multiple harmonics in the harmonic current corresponding to the harmonic current index data according to the pulsation number of the converter of the wind turbine group in the offshore wind farm, wherein the types of the multiple harmonics include characteristic multiple harmonics and non-characteristic multiple harmonics; A second determining unit, configured to determine the number of each type of multiple harmonics, and determine an adjustment coefficient of each multiple harmonic based on the number of each type of multiple harmonics; An adjustment unit, configured to adjust the harmonic current index data based on the adjustment coefficient of each multiple harmonic to obtain adjusted harmonic current index data; Specifically, it includes: first, calculating the integer order of characteristic harmonics contained in the harmonic current; second, allocating 50% adjustment coefficient to the harmonic current of characteristic order, and allocating 50% adjustment coefficient to the harmonic current of non-characteristic order; third, all harmonic currents of characteristic order are equally divided into 50% adjustment coefficient, and all harmonic currents of non-characteristic order are also equally divided into 50% adjustment coefficient.

8. The computing system of claim 7, wherein: The acquisition module comprises: A first acquisition unit is used to acquire the corresponding harmonic current true value, harmonic voltage total distortion rate true value, voltage fluctuation true value, voltage flicker true value and three-phase current unbalance true value when the offshore wind farm is connected to the grid, and the corresponding harmonic current threshold, harmonic voltage total distortion rate threshold, voltage fluctuation threshold, voltage flicker threshold and three-phase current unbalance threshold when the offshore wind farm is connected to the grid; The second acquisition unit is used to respectively acquire the ratio of the true value to the corresponding threshold value, and use the ratio of each true value to the corresponding threshold value as the indicator data.

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