Weak grid resonance detection method and apparatus

Abstract

The application provides a weak power grid resonance detection method and device. Distortion detection is performed on a grid-connected signal obtained through sampling. A plurality of distortion detection results in a detection time window are statistically processed to determine the waveform distortion degree of the grid-connected signal in the detection time window. Whether the distortion is continuously aggravated is determined based on the statistical value of the distortion results in the detection time window, and whether weak power grid resonance occurs is determined. The weak power grid resonance is accurately detected without affecting the quality of the grid-connected current, and the method is simple and reliable.

Description

Technical Field

[0001] This invention relates to the field of new energy power generation technology, and more specifically, to a method and device for detecting weak grid resonance. Background Technology

[0002] With the increasing penetration and capacity of new energy power generation, and the fact that grid connection points are often located at the end of the power grid, the power grid increasingly exhibits characteristics of a weak grid from the perspective of new energy power generation equipment connection points. Traditional current-controlled grid-connected inverters (CCIs), which regulate grid-connected active and reactive power, are prone to resonance in weak grids. Therefore, it is necessary to identify when resonance occurs and suppress it to improve the robustness of CCIs in weak grids.

[0003] The commonly used resonance detection method is grid impedance identification, which involves injecting a certain characteristic signal into the grid online through the inverter and obtaining the grid response signal. The impedance parameters are then calculated to determine whether inverter grid resonance has occurred. However, this method requires injecting a characteristic signal into the grid, which affects the grid current quality. Summary of the Invention

[0004] In view of this, the present invention provides a method and apparatus for detecting weak grid resonance, which can accurately detect weak grid resonance without affecting the grid current quality. The method is simple and reliable.

[0005] To achieve the above-mentioned objectives, the present invention provides the following specific technical solution:

[0006] In a first aspect, embodiments of the present invention provide a method for detecting resonance in a weak electrical grid, comprising:

[0007] Sampling of grid connection signals;

[0008] Distortion detection is performed on the sampled grid-connected signal;

[0009] Statistical processing is performed on multiple consecutive distortion detection results within the detection time window to obtain statistical values ​​of distortion results within the detection time window;

[0010] Based on the statistical values ​​of distortion results within the detection time window, it is determined whether a weak grid resonance has occurred.

[0011] In some embodiments, the distortion detection of the sampled grid-connected signal includes at least one of the following:

[0012] The difference between the sampled grid-connected signal and the sampled grid-connected signal N signal cycles ago is calculated to obtain the distortion detection result.

[0013] The difference between the absolute value of the sampled grid-connected signal and the absolute value of the sampled grid-connected signal 0.5*N signal cycles ago is calculated to obtain the distortion detection result;

[0014] The difference between the positive half-cycle value of the sampled grid-connected signal and the positive half-cycle value sampled N signal cycles ago is calculated to obtain the distortion detection result.

[0015] The difference between the negative half-cycle value of the sampled grid-connected signal and the negative half-cycle value sampled N signal cycles ago is calculated to obtain the distortion detection result.

[0016] The difference between the positive half-cycle value of the sampled grid-connected signal and the negative half-cycle value sampled N signal cycles ago is calculated to obtain the distortion detection result.

[0017] The difference between the negative half-cycle value of the sampled grid-connected signal and the positive half-cycle value sampled N signal cycles ago is calculated to obtain the distortion detection result.

[0018] In the above terms, N is a positive integer.

[0019] In some embodiments, the statistical processing of multiple consecutive distortion detection results within a detection time window to obtain statistical values ​​of distortion results within the detection time window includes at least one of the following:

[0020] The maximum value of multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of distortion results within the detection time window;

[0021] The minimum value of multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of distortion results within the detection time window;

[0022] Calculate the variance of multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of distortion results within the detection time window;

[0023] Calculate the average value of multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of distortion results within the detection time window;

[0024] The effective periodic value of multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of distortion results within the detection time window;

[0025] The effective periodic value of the AC component in multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of the distortion results within the detection time window;

[0026] The proportion of the periodic effective value of the AC component to the periodic effective value in multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of the distortion results within the detection time window;

[0027] The difference between the maximum and minimum values ​​of multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of the distortion results within the detection time window.

[0028] In some embodiments, determining whether a weak grid resonance has occurred based on the statistical values ​​of the distortion results within the detection time window includes:

[0029] Determine whether the statistical value of the distortion result within the detection time window is within the corresponding threshold range;

[0030] If it is within the corresponding threshold range, it is determined that no weak grid resonance has occurred;

[0031] If it is not within the corresponding threshold range, weak grid resonance is determined to have occurred.

[0032] In some embodiments, determining whether a weak grid resonance has occurred based on the statistical values ​​of the distortion results within the detection time window includes:

[0033] Determine whether the statistical value of the distortion result within the detection time window is within the corresponding threshold range;

[0034] The number of times and / or duration during which the statistical value of the distortion result exceeds the corresponding threshold range within a preset time window is determined, wherein the preset time window includes multiple detection time windows;

[0035] Based on the number of times and / or duration of distortion result statistics exceeding the corresponding threshold range within a preset time window, it is determined whether weak grid resonance has occurred.

[0036] In some embodiments, determining whether a weak grid resonance has occurred based on the statistical values ​​of the distortion results within the detection time window includes:

[0037] When performing distortion detection on the sampled grid-connected signal, which includes multiple methods, and / or performing statistical processing on multiple consecutive distortion detection results within the detection time window, which includes multiple methods, it is determined whether the statistical value of each distortion result within the detection time window is within the corresponding threshold range, thus obtaining multiple judgment results.

[0038] Perform logical operations on multiple of the aforementioned judgment results;

[0039] Based on the results of the logical operations, determine whether a weak grid resonance has occurred.

[0040] In some embodiments, determining whether a weak grid resonance has occurred based on the statistical values ​​of the distortion results within the detection time window includes:

[0041] When performing distortion detection on the sampled grid-connected signal, which includes multiple methods, and / or performing statistical processing on multiple consecutive distortion detection results within the detection time window, which includes multiple methods, it is determined whether the statistical value of each distortion result within the detection time window is within the corresponding threshold range, thus obtaining multiple judgment results.

[0042] According to the preset grouping rules, the multiple judgment results are grouped.

[0043] Perform logical operations on the judgment results within each group;

[0044] Perform logical operations on the results of the logical operations for each group to obtain the final logical operation result;

[0045] Based on the final logical operation results, determine whether a weak grid resonance has occurred.

[0046] Secondly, embodiments of the present invention provide a weak grid resonance detection device, comprising:

[0047] The sampling unit is used to sample the grid-connected signal;

[0048] The distortion detection unit is used to detect distortion in the sampled grid-connected signal.

[0049] The statistical processing unit is used to perform statistical processing on multiple consecutive distortion detection results within the detection time window to obtain statistical values ​​of the distortion results within the detection time window.

[0050] The resonance judgment unit is used to determine whether a weak power grid resonance has occurred based on the statistical values ​​of the distortion results within the detection time window.

[0051] In some embodiments, the distortion detection unit is configured to perform at least one of the following operations:

[0052] The difference between the sampled grid-connected signal and the sampled grid-connected signal N signal cycles ago is calculated to obtain the distortion detection result.

[0053] The difference between the absolute value of the sampled grid-connected signal and the absolute value of the sampled grid-connected signal 0.5*N signal cycles ago is calculated to obtain the distortion detection result;

[0054] The difference between the positive half-cycle value of the sampled grid-connected signal and the positive half-cycle value sampled N signal cycles ago is calculated to obtain the distortion detection result.

[0055] The difference between the negative half-cycle value of the sampled grid-connected signal and the negative half-cycle value sampled N signal cycles ago is calculated to obtain the distortion detection result.

[0056] The difference between the positive half-cycle value of the sampled grid-connected signal and the negative half-cycle value sampled N signal cycles ago is calculated to obtain the distortion detection result.

[0057] The difference between the negative half-cycle value of the sampled grid-connected signal and the positive half-cycle value sampled N signal cycles ago is calculated to obtain the distortion detection result.

[0058] In the above terms, N is a positive integer.

[0059] In some embodiments, the statistical processing unit is configured to perform at least one of the following operations:

[0060] The maximum value of multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of distortion results within the detection time window;

[0061] The minimum value of multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of distortion results within the detection time window;

[0062] Calculate the variance of multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of distortion results within the detection time window;

[0063] Calculate the average value of multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of distortion results within the detection time window;

[0064] The effective periodic value of multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of distortion results within the detection time window;

[0065] The effective periodic value of the AC component in multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of the distortion results within the detection time window;

[0066] The proportion of the periodic effective value of the AC component to the periodic effective value in multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of the distortion results within the detection time window;

[0067] The difference between the maximum and minimum values ​​of multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of the distortion results within the detection time window.

[0068] In some embodiments, the resonance determination unit is specifically used to determine whether the statistical value of the distortion result within the detection time window is within the corresponding threshold range; if it is within the corresponding threshold range, it is determined that no weak grid resonance has occurred; if it is not within the corresponding threshold range, it is determined that weak grid resonance has occurred.

[0069] In some embodiments, the resonance determination unit is specifically used to determine whether the statistical value of the distortion result within the detection time window is within the corresponding threshold range; to determine the number of times and / or the duration of the statistical value of the distortion result exceeding the corresponding threshold range within a preset time window, wherein the preset time window includes multiple detection time windows; and to determine whether weak grid resonance has occurred based on the number of times and / or the duration of the statistical value of the distortion result exceeding the corresponding threshold range within the preset time window.

[0070] In some embodiments, the resonance judgment unit is specifically used to determine whether the statistical value of each distortion result within the detection time window is within the corresponding threshold range when the distortion detection of the sampled grid-connected signal includes multiple operations and / or the statistical processing of multiple consecutive distortion detection results within the detection time window includes multiple operations, thereby obtaining multiple judgment results; to perform logical operations on the multiple judgment results; and to determine whether weak grid resonance has occurred based on the logical operation results.

[0071] In some embodiments, the resonance judgment unit is specifically configured to, when performing distortion detection on the sampled grid-connected signal including multiple operations and / or performing statistical processing on multiple consecutive distortion detection results within the detection time window including multiple operations, determine whether the statistical value of each distortion result within the detection time window is within the corresponding threshold range, thereby obtaining multiple judgment results; group the multiple judgment results according to a preset grouping rule; perform logical operations on the judgment results within each group; perform logical operations on the logical operation results of each group to obtain the final logical operation result; and determine whether weak grid resonance has occurred based on the final logical operation result.

[0072] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0073] This invention discloses a method and apparatus for detecting weak grid resonance. It performs distortion detection on the sampled grid-connected signal, and determines the degree of waveform distortion of the grid-connected signal within the detection time window by statistically processing multiple consecutive distortion detection results within the detection time window. Based on the statistical value of the distortion results within the detection time window, it determines whether the distortion continues to worsen and whether weak grid resonance has occurred. The method accurately detects weak grid resonance without affecting the grid current quality, and is simple and reliable. Attached Figure Description

[0074] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0075] Figure 1 This is a schematic flowchart of a weak grid resonance detection method disclosed in an embodiment of the present invention;

[0076] Figure 2 This is a schematic diagram of the structure of a weak grid resonance detection device disclosed in an embodiment of the present invention. Detailed Implementation

[0077] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0078] This invention provides a method and apparatus for detecting weak grid resonance, applied to an electronic device. This electronic device can be deployed at the grid connection point or in other locations. It samples the grid connection signal, performs distortion detection on the sampled grid connection signal, and determines the degree of waveform distortion of the grid connection signal within the detection time window by statistically processing multiple consecutive distortion detection results within the detection time window. Based on the statistical value of the distortion results within the detection time window, it determines whether the distortion continues to worsen and whether weak grid resonance has occurred. The method accurately detects weak grid resonance without affecting the grid current quality, and is simple and reliable.

[0079] Please see Figure 1 This embodiment discloses a method for detecting resonance in a weak power grid, which specifically includes the following steps:

[0080] S101: Sample the grid-connected signal;

[0081] The grid connection signal can be the grid connection current signal, the grid connection voltage signal, or the product of the grid connection current signal and the grid connection voltage signal, i.e., the instantaneous grid connection power signal.

[0082] Specifically, the grid-connected signal is sampled according to a pre-set sampling frequency.

[0083] S102: Perform distortion detection on the sampled grid-connected signal;

[0084] Specifically, by comparing the difference between the sampled grid-connected signal and the signal before and after sampling, it can be determined whether the grid-connected signal has been distorted. There are multiple ways to perform the difference comparison between the sampled grid-connected signal and the signal before and after sampling, such as full-cycle waveform distortion detection, positive half-cycle waveform distortion detection, negative half-cycle waveform distortion detection, etc.

[0085] S103: Perform statistical processing on multiple consecutive distortion detection results within the detection time window to obtain statistical values ​​of distortion results within the detection time window;

[0086] It is understandable that distortion detection of the sampled grid-connected signal yields the distortion detection result of the instantaneous waveform. The occurrence of distortion in the instantaneous waveform does not necessarily indicate weak grid resonance. Therefore, in order to improve the reliability of the resonance detection result, this embodiment performs statistical processing on multiple consecutive distortion detection results within the detection time window to determine whether the degree of distortion continues to increase.

[0087] The detection time window can include multiple signal cycles.

[0088] There are various ways to perform statistical processing on multiple consecutive distortion detection results within a detection time window, such as calculating the maximum value, minimum value, average value, variance, etc.

[0089] S104: Determine whether a weak grid resonance has occurred based on the statistical values ​​of the distortion results within the detection time window.

[0090] Understandably, by statistically processing multiple consecutive distortion detection results within the detection time window, the statistical value of the distortion results within the detection time window can be used to determine whether the degree of distortion continues to increase. If the degree of distortion continues to increase, it indicates that a weak power grid resonance has occurred. If the degree of distortion is stable, it indicates that a weak power grid resonance has not occurred.

[0091] As can be seen, the weak grid resonance detection method disclosed in this embodiment performs distortion detection on the sampled grid-connected signal, and determines the degree of waveform distortion of the grid-connected signal within the detection time window by statistically processing multiple consecutive distortion detection results within the detection time window. Based on the statistical value of the distortion results within the detection time window, it is determined whether the distortion continues to worsen and whether weak grid resonance has occurred. The method accurately detects weak grid resonance without affecting the grid current quality, and is simple and reliable.

[0092] S102 can be implemented in multiple ways. For example, S102 can be implemented in at least one of the following ways:

[0093] A1: Calculate the difference between the sampled grid-connected signal and the grid-connected signal sampled N signal cycles ago to obtain the distortion detection result.

[0094] A2: Calculate the difference between the absolute value of the sampled grid-connected signal and the absolute value of the sampled grid-connected signal 0.5*N signal cycles ago to obtain the distortion detection result.

[0095] A3: Calculate the difference between the positive half-cycle value of the sampled grid-connected signal and the positive half-cycle value sampled N signal cycles ago to obtain the distortion detection result.

[0096] A4: Calculate the difference between the negative half-cycle value of the sampled grid-connected signal and the negative half-cycle value sampled N signal cycles ago to obtain the distortion detection result.

[0097] A5: Calculate the difference between the positive half-cycle value of the sampled grid-connected signal and the negative half-cycle value sampled N signal cycles ago to obtain the distortion detection result.

[0098] A6: Calculate the difference between the negative half-cycle value of the sampled grid-connected signal and the positive half-cycle value sampled N signal cycles ago to obtain the distortion detection result.

[0099] In the above terms, N is a positive integer. The frequency and period of the grid-connected signal can be obtained through a phase-locked loop or zero-crossing detection, which is the signal period mentioned above.

[0100] Taking the sampling of the grid-connected signal M times (M is a positive integer) in one signal cycle as an example, the grid-connected signal obtained by sampling in one signal cycle can be represented by an M-dimensional array: (S1, S2, ..., S... M ). Using S i,j S represents the grid-connected signal obtained by the j-th sample in the i-th signal period. (i-N),j Let S represent the grid-connected signal sampled N signal periods ago. Then, in mode A1, the distortion detection result is (S...). i,j -S (i-N),j ).

[0101] It is understandable that when a signal is distorted, it may be a full-cycle waveform distortion, or it may be a waveform distortion of only the positive or negative half-cycle. This embodiment avoids missing the signal distortion by using multiple distortion detection methods, thereby improving the accuracy of distortion detection.

[0102] S103 can be implemented in multiple ways. For example, S103 can be implemented in at least one of the following ways:

[0103] B1: Calculate the maximum value of multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of distortion results within the detection time window;

[0104] B2: Calculate the minimum value of multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of distortion results within the detection time window;

[0105] B3: Calculate the variance of multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of distortion results within the detection time window;

[0106] B4: Calculate the average value of multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of distortion results within the detection time window;

[0107] B5: Calculate the periodic effective value of multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of distortion results within the detection time window;

[0108] B6: Calculate the periodic effective value of the AC component in multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of the distortion results within the detection time window;

[0109] B7: Calculate the proportion of the periodic effective value of the AC component to the periodic effective value in multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of the distortion results within the detection time window;

[0110] B8: Calculate the difference between the maximum and minimum values ​​of multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of distortion results within the detection time window.

[0111] Among them, the effective value of the period refers to the root mean square value of the period quantity within one period, and the period quantity here is the distortion detection result.

[0112] This embodiment uses statistical processing methods for various distortion results to extract the resonance characteristics of weak power grids from multiple dimensions, thereby improving the accuracy of resonance detection.

[0113] Based on the selection of the above-mentioned distortion detection method and the selection of the statistical processing method for the distortion result statistics, S104 in the above embodiment can also be implemented in multiple ways:

[0114] Method 1

[0115] Determine whether the statistical value of the distortion results within the detection time window is within the corresponding threshold range;

[0116] If it is within the corresponding threshold range, it is determined that no weak grid resonance has occurred;

[0117] If it is not within the corresponding threshold range, weak grid resonance is determined to have occurred.

[0118] It should be noted that the combination of distortion detection method and statistical processing method of distortion result statistics corresponds to a threshold range. For example, the combination of distortion detection method A1 and statistical processing method of distortion result statistics B1 corresponds to the threshold range C1. Taking the distortion detection method including A1 to A6 (6 implementation methods) and the statistical processing method of distortion result statistics including B1 to B8 (8 implementation methods) as an example, there are a total of 48 combinations of distortion detection method and statistical processing method of distortion result statistics, and each combination corresponds to a threshold range.

[0119] If the entire weak grid resonance detection method includes a distortion detection method and a statistical processing method for the distortion result statistics, then it is only necessary to determine whether the distortion result statistics are within the corresponding threshold range. If they are within the corresponding threshold range, it is determined that no weak grid resonance has occurred; if they are not within the corresponding threshold range, it is determined that weak grid resonance has occurred.

[0120] If the entire weak grid resonance detection method includes multiple distortion detection methods and / or multiple distortion result statistical value statistical processing methods, there will be distortion result statistical values ​​in multiple dimensions. It is necessary to determine whether the distortion result statistical value in each dimension is within the corresponding threshold range, and use the following method three for subsequent resonance judgment.

[0121] Method 2

[0122] Determine whether the statistical value of the distortion results within the detection time window is within the corresponding threshold range;

[0123] Determine the number of times and / or the duration of the distortion result statistics exceeding the corresponding threshold range within a preset time window. The preset time window includes multiple detection time windows.

[0124] Based on the number of times and / or duration of distortion result statistics exceeding the corresponding threshold range within a preset time window, it is determined whether weak grid resonance has occurred.

[0125] It is understandable that if the statistical value of the distortion result within the detection time window is within the corresponding threshold range, it only indicates that the signal distortion continues to worsen within the detection time window. To avoid errors in the weak grid resonance detection results caused by other interference factors such as setting the detection time window too small, this embodiment determines whether weak grid resonance has occurred based on the number of times and / or the duration of the statistical value of the distortion result exceeding the corresponding threshold range within the preset time window. Specifically, if the number of times the statistical value of the distortion result exceeds the corresponding threshold range within the preset time window is greater than a first set value and / or the duration is greater than a second set value, weak grid resonance is determined to have occurred; otherwise, weak grid resonance is determined not to have occurred.

[0126] Method 3

[0127] When performing distortion detection on the sampled grid-connected signal, including multiple distortions and / or performing statistical processing on multiple consecutive distortion detection results within the detection time window, multiple dimensions of distortion result statistical values ​​will be obtained. Each distortion result statistical value within the detection time window will be judged to determine whether it is within the corresponding threshold range, resulting in multiple judgment results.

[0128] Perform logical operations on multiple judgment results;

[0129] Based on the results of the logical operations, determine whether a weak grid resonance has occurred.

[0130] Among them, logical operations can be either logical AND operations or logical OR operations.

[0131] If the logical operation result is true, it is determined that no weak grid resonance has occurred; if the logical operation result is false, it is determined that grid resonance has occurred. This embodiment, having obtained statistical values ​​of distortion results in multiple dimensions, performs logical operations on the judgment results of whether the statistical values ​​of distortion results in each dimension are within the corresponding threshold range. This achieves the combined detection results of weak grid resonance characteristics from multiple dimensions, accurately determining whether weak grid resonance has occurred.

[0132] Method 4

[0133] When performing distortion detection on the sampled grid-connected signal, including multiple distortions and / or performing statistical processing on multiple consecutive distortion detection results within the detection time window, multiple dimensions of distortion result statistical values ​​will be obtained. Each distortion result statistical value within the detection time window will be judged to determine whether it is within the corresponding threshold range, resulting in multiple judgment results.

[0134] Group the multiple judgment results according to the preset grouping rules;

[0135] Perform logical operations on the judgment results within each group;

[0136] Perform logical operations on the results of the logical operations for each group to obtain the final logical operation result;

[0137] Based on the final logical operation results, determine whether a weak grid resonance has occurred.

[0138] In this embodiment, when the number of statistical values ​​of the obtained distortion results is large, that is, the dimension of the weak grid resonance characteristics is high, multiple judgment results are grouped according to preset grouping rules, and logical operations such as logical AND and logical OR operations are performed on the judgment results within the group. Logical operations are then performed on the logical operation results of each group to obtain the final logical operation result, thereby realizing accurate analysis of the resonance characteristics of high-latitude weak grids and improving the accuracy of weak grid resonance detection.

[0139] Furthermore, multiple distortion result statistics corresponding to the same distortion detection method can be grouped together, or multiple distortion result statistics corresponding to the same distortion result statistical method can be grouped together.

[0140] It is understandable that some of the various methods of distortion detection are related, and some of the methods of distortion result statistics are also related. Distortion detection methods can be grouped according to their correlation, and the multiple distortion result statistics corresponding to the same distortion detection method can be grouped together. Similarly, distortion result statistics methods can be grouped according to their correlation, and the multiple distortion result statistics corresponding to the same distortion result statistics method can be grouped together.

[0141] The above are just a few possible grouping examples, and the present invention is not limited thereto.

[0142] Based on the weak grid resonance detection method disclosed in the above embodiments, this embodiment correspondingly discloses a weak grid resonance detection device. Please refer to [link / reference needed]. Figure 2 The device includes:

[0143] Sampling unit 201 is used to sample grid-connected signals;

[0144] The distortion detection unit 202 is used to perform distortion detection on the sampled grid-connected signal;

[0145] The statistical processing unit 203 is used to perform statistical processing on multiple consecutive distortion detection results within the detection time window to obtain statistical values ​​of distortion results within the detection time window.

[0146] The resonance judgment unit 204 is used to determine whether a weak grid resonance has occurred based on the statistical value of the distortion results within the detection time window.

[0147] In some embodiments, the distortion detection unit 202 is configured to perform at least one of the following operations:

[0148] The difference between the sampled grid-connected signal and the sampled grid-connected signal N signal cycles ago is calculated to obtain the distortion detection result.

[0149] The difference between the absolute value of the sampled grid-connected signal and the absolute value of the sampled grid-connected signal 0.5*N signal cycles ago is calculated to obtain the distortion detection result;

[0150] The difference between the positive half-cycle value of the sampled grid-connected signal and the positive half-cycle value sampled N signal cycles ago is calculated to obtain the distortion detection result.

[0151] The difference between the negative half-cycle value of the sampled grid-connected signal and the negative half-cycle value sampled N signal cycles ago is calculated to obtain the distortion detection result.

[0152] The difference between the positive half-cycle value of the sampled grid-connected signal and the negative half-cycle value sampled N signal cycles ago is calculated to obtain the distortion detection result.

[0153] The difference between the negative half-cycle value of the sampled grid-connected signal and the positive half-cycle value sampled N signal cycles ago is calculated to obtain the distortion detection result.

[0154] In the above terms, N is a positive integer.

[0155] In some embodiments, the statistical processing unit 203 is configured to perform at least one of the following operations:

[0156] The maximum value of multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of distortion results within the detection time window;

[0157] The minimum value of multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of distortion results within the detection time window;

[0158] Calculate the variance of multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of distortion results within the detection time window;

[0159] Calculate the average value of multiple consecutive distortion detection results within the detection time window, and use it as the statistical value of distortion results within the detection time window;

[0160] The effective periodic value of multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of distortion results within the detection time window;

[0161] The effective periodic value of the AC component in multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of the distortion results within the detection time window;

[0162] The proportion of the periodic effective value of the AC component to the periodic effective value in multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of the distortion results within the detection time window;

[0163] The difference between the maximum and minimum values ​​of multiple consecutive distortion detection results within the detection time window is calculated and used as the statistical value of the distortion results within the detection time window.

[0164] In some embodiments, the resonance determination unit 204 is specifically used to determine whether the statistical value of the distortion result within the detection time window is within the corresponding threshold range; if it is within the corresponding threshold range, it is determined that no weak grid resonance has occurred; if it is not within the corresponding threshold range, it is determined that weak grid resonance has occurred.

[0165] In some embodiments, the resonance determination unit 204 is specifically used to determine whether the statistical value of the distortion result within the detection time window is within the corresponding threshold range; determine the number of times and / or the duration of the statistical value of the distortion result exceeding the corresponding threshold range within a preset time window, the preset time window including multiple detection time windows; and determine whether weak grid resonance occurs based on the number of times and / or the duration of the statistical value of the distortion result exceeding the corresponding threshold range within the preset time window.

[0166] In some embodiments, the resonance judgment unit 204 is specifically used to determine whether the statistical value of each distortion result in the detection time window is within the corresponding threshold range when the distortion detection of the sampled grid-connected signal includes multiple operations and / or the statistical processing of multiple consecutive distortion detection results within the detection time window includes multiple operations, thereby obtaining multiple judgment results; to perform logical operations on the multiple judgment results; and to determine whether weak grid resonance occurs based on the logical operation results.

[0167] In some embodiments, the resonance judgment unit 204 is specifically configured to, when performing distortion detection on the sampled grid-connected signal including multiple operations and / or performing statistical processing on multiple consecutive distortion detection results within the detection time window including multiple operations, determine whether the statistical value of each distortion result within the detection time window is within the corresponding threshold range, thereby obtaining multiple judgment results; group the multiple judgment results according to a preset grouping rule; perform logical operations on the judgment results within each group; perform logical operations on the logical operation results of each group to obtain the final logical operation result; and determine whether weak grid resonance has occurred based on the final logical operation result.

[0168] This embodiment discloses a weak grid resonance detection device that performs distortion detection on the sampled grid-connected signal. By statistically processing multiple consecutive distortion detection results within the detection time window, the degree of waveform distortion of the grid-connected signal within the detection time window is determined. Based on the statistical value of the distortion results within the detection time window, it is determined whether the distortion continues to worsen and whether weak grid resonance has occurred. The device accurately detects weak grid resonance without affecting the grid current quality. The method is simple and reliable.

[0169] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0170] 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.

[0171] 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.

[0172] The above embodiments can be combined arbitrarily. The descriptions of the disclosed embodiments and the features recorded in the embodiments of this specification can be substituted or combined with each other, so that those skilled in the art can implement or use this application.

[0173] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. 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 the invention. Therefore, the invention 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 detecting resonance in a weak power grid, characterized in that, The method comprises: sampling the grid-connected signal; performing distortion detection on the sampled grid-connected signal, the distortion detection comprising: performing a difference comparison on the sampled grid-connected signal, and determining whether the grid-connected signal is distorted; performing statistical processing on a plurality of continuous distortion detection results in a detection time window to obtain a distortion result statistical value in the detection time window; determining whether a weak grid resonance occurs according to the distortion result statistical value in the detection time window; wherein determining whether a weak grid resonance occurs according to the distortion result statistical value in the detection time window comprises: determining whether the distortion result statistical value in the detection time window is within a corresponding threshold range; determining a number of times and / or a duration that the distortion result statistical value is outside the corresponding threshold range within a preset time window, the preset time window comprising a plurality of detection time windows; determining whether a weak grid resonance occurs according to the number of times and / or the duration that the distortion result statistical value is outside the corresponding threshold range within the preset time window.

2. The method of claim 1, wherein, The distortion detection on the sampled grid-connected signal comprises at least one of: calculating a difference value between the sampled grid-connected signal and a grid-connected signal sampled N signal periods ago to obtain a distortion detection result; calculating a difference value between an absolute value of the sampled grid-connected signal and an absolute value of a grid-connected signal sampled 0.5*N signal periods ago to obtain a distortion detection result; calculating a difference value between a positive half-cycle value of the sampled grid-connected signal and a positive half-cycle value of a grid-connected signal sampled N signal periods ago to obtain a distortion detection result; calculating a difference value between a negative half-cycle value of the sampled grid-connected signal and a negative half-cycle value of a grid-connected signal sampled N signal periods ago to obtain a distortion detection result; calculating a difference value between a positive half-cycle value of the sampled grid-connected signal and a negative half-cycle value of a grid-connected signal sampled N signal periods ago to obtain a distortion detection result; calculating a difference value between a negative half-cycle value of the sampled grid-connected signal and a positive half-cycle value of a grid-connected signal sampled N signal periods ago to obtain a distortion detection result; wherein N in each of the above is a positive integer.

3. The method of claim 2, wherein, The statistical processing on the plurality of continuous distortion detection results in the detection time window to obtain the distortion result statistical value in the detection time window comprises at least one of: calculating a maximum value of the plurality of continuous distortion detection results in the detection time window as the distortion result statistical value in the detection time window; calculating a minimum value of the plurality of continuous distortion detection results in the detection time window as the distortion result statistical value in the detection time window; calculating a variance of the plurality of continuous distortion detection results in the detection time window as the distortion result statistical value in the detection time window; calculating an average value of the plurality of continuous distortion detection results in the detection time window as the distortion result statistical value in the detection time window; calculating a cycle effective value of the plurality of continuous distortion detection results in the detection time window as the distortion result statistical value in the detection time window; Calculate the cycle effective value of the alternating component in the continuous plurality of distortion detection results in the detection time window as the distortion result statistical value in the detection time window; Calculate the proportion of the cycle effective value of the alternating component in the continuous plurality of distortion detection results in the detection time window to the cycle effective value as the distortion result statistical value in the detection time window; Calculate the difference between the maximum value and the minimum value of the continuous plurality of distortion detection results in the detection time window as the distortion result statistical value in the detection time window.

4. The method according to claim 1 or 3, characterized in that, According to the distortion result statistical value in the detection time window, determine whether the weak power grid resonance occurs, further comprising: Determine whether the distortion result statistical value in the detection time window is within the corresponding threshold range; If within the corresponding threshold range, determine that the weak power grid resonance does not occur; If not within the corresponding threshold range, determine that the weak power grid resonance occurs.

5. The method of claim 3, wherein, According to the distortion result statistical value in the detection time window, determine whether the weak power grid resonance occurs, further comprising: In the case that the distortion detection on the sampled grid-connected signal includes multiple items and / or the statistical processing on the continuous plurality of distortion detection results in the detection time window includes multiple items, respectively determine whether each kind of distortion result statistical value in the detection time window is within the corresponding threshold range, to obtain multiple determination results; Logical operation is performed on the multiple determination results; According to the logical operation result, determine whether the weak power grid resonance occurs.

6. The method of claim 3, wherein, According to the distortion result statistical value in the detection time window, determine whether the weak power grid resonance occurs, further comprising: In the case that the distortion detection on the sampled grid-connected signal includes multiple items and / or the statistical processing on the continuous plurality of distortion detection results in the detection time window includes multiple items, respectively determine whether each kind of distortion result statistical value in the detection time window is within the corresponding threshold range, to obtain multiple determination results; According to a preset grouping rule, group the multiple determination results; Logical operation is respectively performed on the determination results in each group; Logical operation is performed on the logical operation results of each group to obtain a final logical operation result; According to the final logical operation result, determine whether the weak power grid resonance occurs.

7. A weak grid resonance detection apparatus, characterized by, Comprise: A sampling unit for sampling a grid-connected signal; A distortion detection unit for performing distortion detection on the sampled grid-connected signal, the distortion detection comprising: comparing the sampled grid-connected signal before and after, to determine whether the grid-connected signal has distortion; A statistical processing unit for statistically processing the continuous plurality of distortion detection results in the detection time window to obtain the distortion result statistical value in the detection time window; A resonance judgment unit for determining whether the weak power grid resonance occurs according to the distortion result statistical value in the detection time window; The resonance judgment unit is specifically configured to judge whether the distortion result statistical value in the detection time window is within the corresponding threshold range; determine the number of times and / or duration that the distortion result statistical value is out of the corresponding threshold range within a preset time window, the preset time window including a plurality of detection time windows; and determine whether the weak power grid resonance occurs according to the number of times and / or duration that the distortion result statistical value is out of the corresponding threshold range within the preset time window.

8. The apparatus of claim 7, wherein, The distortion detection unit is configured to perform at least one of the following operations: calculating the difference between the grid-connected signal sampled and the grid-connected signal sampled N signal periods ago to obtain a distortion detection result; calculating the difference between the absolute value of the grid-connected signal sampled and the absolute value of the grid-connected signal sampled 0.5*N signal periods ago to obtain a distortion detection result; calculating the difference between the positive half-cycle value of the grid-connected signal sampled and the positive half-cycle value of the grid-connected signal sampled N signal periods ago to obtain a distortion detection result; calculating the difference between the negative half-cycle value of the grid-connected signal sampled and the negative half-cycle value of the grid-connected signal sampled N signal periods ago to obtain a distortion detection result; calculating the difference between the positive half-cycle value of the grid-connected signal sampled and the negative half-cycle value of the grid-connected signal sampled N signal periods ago to obtain a distortion detection result; calculating the difference between the negative half-cycle value of the grid-connected signal sampled and the positive half-cycle value of the grid-connected signal sampled N signal periods ago to obtain a distortion detection result; wherein N in each of the above is a positive integer.

9. The apparatus of claim 8, wherein, The statistical processing unit is configured to perform at least one of the following operations: calculating the maximum value of the continuous plurality of distortion detection results in the detection time window as the distortion result statistical value in the detection time window; calculating the minimum value of the continuous plurality of distortion detection results in the detection time window as the distortion result statistical value in the detection time window; calculating the variance of the continuous plurality of distortion detection results in the detection time window as the distortion result statistical value in the detection time window; calculating the average value of the continuous plurality of distortion detection results in the detection time window as the distortion result statistical value in the detection time window; calculating the cycle effective value of the continuous plurality of distortion detection results in the detection time window as the distortion result statistical value in the detection time window; calculating the cycle effective value of the alternating current component in the continuous plurality of distortion detection results in the detection time window as the distortion result statistical value in the detection time window; calculating the proportion of the cycle effective value of the alternating current component in the continuous plurality of distortion detection results in the detection time window to the cycle effective value as the distortion result statistical value in the detection time window; calculating the difference between the maximum value and the minimum value of the continuous plurality of distortion detection results in the detection time window as the distortion result statistical value in the detection time window.

10. The apparatus of claim 7 or 9, wherein, The resonance judgment unit is further specifically configured to determine whether the distortion result statistical value in the detection time window is within the corresponding threshold range; if yes, it is determined that the weak power grid resonance does not occur; if no, it is determined that the weak power grid resonance occurs.

11. The apparatus of claim 9, wherein, The resonance judgment unit is further specifically configured to, in the case that the distortion detection on the sampled grid-connected signal includes multiple items and / or the statistical processing on the continuous multiple distortion detection results in the detection time window includes multiple items, respectively determine whether each distortion result statistical value in the detection time window is within the corresponding threshold range, to obtain multiple judgment results; and perform logical operation on the multiple judgment results. According to the logical operation result, it is determined whether the weak power grid resonance occurs.

12. The apparatus of claim 9, wherein, The resonance judgment unit is further specifically configured to, in the case that the distortion detection on the sampled grid-connected signal includes multiple items and / or the statistical processing on the continuous multiple distortion detection results in the detection time window includes multiple items, respectively determine whether each distortion result statistical value in the detection time window is within the corresponding threshold range, to obtain multiple judgment results; according to a preset grouping rule, the multiple judgment results are grouped; and logical operation is performed on the judgment results in each group respectively. Logical operation is performed on the logical operation results of each group to obtain a final logical operation result. According to the final logical operation result, it is determined whether the weak power grid resonance occurs.

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