Electrical fault early warning method and system for photovoltaic grid-connected distribution box

Abstract

The invention relates to the field of electrical fault early warning, in particular to an electrical fault early warning method and system for a photovoltaic grid-connected distribution box. An electrical parameter time sequence diagram is established in real time, a fault area, a gradual change area and a normal state area are divided, and matching analysis of a current sequence and a historical gradual change sequence is combined, so that progressive degradation characteristics of electrical parameters in a photovoltaic grid-connected distribution box can be effectively identified, and early warning is performed before a fault occurs; equipment downtime or fire risks caused by hidden faults are remarkably reduced, a matching degree and close degree dual threshold judgment mechanism is adopted, sensitivity of different fault types is flexibly adapted through dynamic weight distribution, for example, parameter differences are emphasized on capacitance attenuation, trend changes are emphasized on circuit breaker abrasion, and the reliability of the circuit breaker is improved. Therefore, environmental fluctuation interference of a traditional fixed threshold value method is reduced, and the false alarm rate is greatly reduced. The problem that in the prior art, when a fixed threshold value of an electrical parameter is set, early warning is difficult to carry out through detection of operation and maintenance personnel before a fault occurs in the progressive degradation feature is solved.

Description

Technical Field

[0001] The present invention relates to the field of electrical fault early warning, and in particular to an electrical fault early warning method and system for a photovoltaic grid-connected distribution box. Background Art

[0002] As the core distribution unit of the photovoltaic power generation system, the photovoltaic grid-connected distribution box is responsible for the collection, distribution and protection of electric energy. Its operational reliability directly affects the safety and efficiency of the entire photovoltaic system. However, in actual operation, the internal electrical components of the distribution box (such as circuit breakers, contactors, capacitors, etc.) are prone to gradual deterioration due to factors such as environmental corrosion, mechanical wear, and material aging, eventually leading to insulation failure, poor contact, harmonic distortion and other faults. Such faults are highly hidden and have significant cumulative effects. If timely warnings are not received, they may cause serious consequences such as equipment downtime or even fire.

[0003] Existing technologies set fixed thresholds for electrical parameters (such as current and voltage) and trigger alarms when real-time data exceeds the range. This method can only capture sudden faults and has difficulty identifying characteristics of gradual degradation (such as a slow increase in contact point resistance and a gradual decrease in capacitance). It is also easily affected by environmental fluctuations and has a high false alarm rate. Existing technologies mainly rely on on-site detection of equipment status by operation and maintenance personnel, but due to the low detection frequency and strong subjectivity, it is difficult to detect early signs of degradation in a timely manner. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides an electrical fault warning method and system for photovoltaic grid-connected distribution boxes, which solves the problem that when the existing technology sets fixed thresholds for electrical parameters, it is difficult for operation and maintenance personnel to detect the progressive degradation characteristics before a fault occurs.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for early warning of electrical faults in a photovoltaic grid-connected distribution box, the method specifically comprising the following steps:

[0006] S1. Real-time acquisition of electrical data and fault logs on each line in the photovoltaic grid-connected distribution box, and establishment of an electrical parameter timing diagram in chronological order;

[0007] S2. On the electrical parameter timing diagram, mark the area outside the parameter threshold where the timestamp of the fault log is located as the fault area, mark several consecutive moments before the fault area as the gradual change area, and mark the remaining area as the normal area;

[0008] S3. Mark several consecutive moments before the current moment as the current region, and calculate the electrical energy at any moment according to the electrical parameters in the current region, the fault region, and the gradual change region in chronological order, and establish the current sequence, the fault sequence, and the gradual change sequence respectively;

[0009] S4, determining whether there is a suspicious sequence in the gradient region that is completely consistent with the current sequence;

[0010] If it exists, the fault log corresponding to the gradient area is output and an early warning signal is issued;

[0011] If not, proceed to step S5;

[0012] S5. Selecting several reference sequences of equal length to the current sequence from the gradual sequence, and calculating the degree of agreement and closeness between each reference sequence and the current sequence;

[0013] S6. Determine whether there is a control sequence whose degree of fit and closeness to the current sequence are both smaller than the fit threshold and closeness threshold, respectively;

[0014] If it exists, the fault log corresponding to the control sequence is output and an early warning signal is issued;

[0015] If it does not exist, then end.

[0016] Preferably, in step S2, the following steps are specifically included:

[0017] S21. Obtain the timestamp and corresponding electrical parameters of the fault log;

[0018] S22, determining whether the electrical parameter corresponding to the timestamp of the fault log is outside the parameter threshold;

[0019] If yes, the electrical parameter and the corresponding time are marked as fault parameter and fault time respectively, and then the process goes to step S23;

[0020] If not, obtain the electrical parameter and the corresponding time that are closest to the timestamp and outside the parameter threshold, and mark the electrical parameter and the corresponding time as the fault parameter and the fault time respectively;

[0021] S23, marking each non-adjacent fault moment as a different fault area, and marking adjacent fault moments as the same fault area;

[0022] S24, sequentially determining whether adjacent moments on both sides of each fault area contain electrical parameters outside the parameter threshold;

[0023] If yes, mark the adjacent time as the fault time, and then return to step S23;

[0024] If not, proceed to step S25;

[0025] S25: Mark several moments before the fault area as gradual change areas, and mark the remaining areas as normal areas.

[0026] Preferably, in step S3, the following steps are specifically included:

[0027] S31. Calculate the electrical energy at the next moment based on the electrical parameters at any two moments in the electrical parameter sequence diagram. The calculation formula for the electrical energy at any moment is:

[0028]

[0029] In the above formula, Q i represents the electrical energy at the i-th moment, E(t) represents the function of the change of electrical parameters over time, t i-1 and t i Respectively represent the i-th moment;

[0030] S32. Set the standard duration, and modify the duration of the electrical parameters at each adjacent moment to the standard duration, and then update the standard electrical energy at any moment; the calculation formula of the standard electrical energy is:

[0031]

[0032] In the above formula, Q' i represents the electrical energy at the i-th moment after update, Q i represents the electrical energy at the i-th moment before the update, ΔT i Indicates the duration between the i-th moment and the i-1-th moment, ΔT 0 Indicates standard electrical energy;

[0033] S33, generating a current sequence and a gradual change sequence in the current area and the gradual change area according to the updated standard electrical energy;

[0034] The expression of the current sequence is: D={D1,D2,D3,…,D n}

[0035] The expression of the fault sequence is: G={G1,G2,g3,…,G k}

[0036] The expression of the gradual change sequence is: J={J1, J2, J3, ..., J m}

[0037] In the above formula, D and J represent the current sequence and the gradual sequence respectively, D n Indicates the standard electrical energy at the nth moment in the current sequence, J m represents the standard electrical energy at the mth moment in the gradient sequence, G k It represents the standard electrical energy at the kth moment in the fault sequence.

[0038] Preferably, in step S5, the following steps are specifically included:

[0039] S51, taking each moment in the gradual change sequence as a reference point;

[0040] S52. Construct a time frame, and use the reference point as the starting point of the time frame and the length of the current sequence as the length of the time frame;

[0041] S53, arranging the standard electrical energy in each time frame in order to generate a control sequence, and marking the area corresponding to the control sequence on the electrical parameter timing diagram as a control area;

[0042] S54. Establish a reference interval that is less than or equal to one tangent function period, and normalize the reference sequence and the current sequence to the reference interval to generate a standard reference sequence and a standard current sequence, respectively.

[0043] S55, calculating the degree of agreement between the standard control sequence and the standard current sequence;

[0044] S56. Calculate the degree of overlap between the standard control sequence and the standard current sequence.

[0045] Preferably, in step S54, the following steps are specifically included:

[0046] S541. Obtain the maximum and minimum values of the standard electrical energy, and calculate the difference between the two to obtain the electrical energy range;

[0047] S542. Establish a reference interval: The expression of the reference interval is:

[0048] (-β, β)∈(kπ-π / 2, kπ+π / 2), where Z is a positive integer;

[0049] S543. Normalize the control sequence and the current sequence to the reference interval to generate a standard control sequence and a standard current sequence, respectively. The calculation formula for the data in the standard control sequence and the standard current sequence obtained after normalization is:

[0050]

[0051] In the above formula, β i Represents the i-th data in the standard control sequence or the standard current sequence obtained after normalization, α i represents the i-th data in the control sequence or the current sequence, α represents the extreme difference in electrical energy, Indicates the average value of standard electrical energy.

[0052] Preferably, in step S56, the following steps are specifically included:

[0053] S561. Acquire electrical parameters at the time corresponding to the standard control sequence and the standard current sequence to obtain a control parameter sequence and a current parameter sequence respectively;

[0054] S562, respectively calculating the slopes of any two parameters in the reference parameter sequence and the current parameter sequence;

[0055] S563: Calculate the degree of overlap of the curves in the electrical parameter timing diagram corresponding to the comparison parameter sequence and the current parameter sequence according to the slope.

[0056] Preferably, in step S6, the following steps are specifically included:

[0057] S61, setting a coincidence threshold, and determining in sequence whether the coincidence degree between each reference sequence and the current sequence is less than the coincidence threshold;

[0058] If yes, proceed to step S62;

[0059] If not, then end.

[0060] S62: Set a coincidence threshold, and determine in sequence whether the coincidence between each reference sequence and the current sequence is less than the coincidence threshold;

[0061] If so, output the fault log corresponding to the control sequence;

[0062] If not, then end.

[0063] Preferably, in step S54, the calculation formula of the degree of fit is:

[0064]

[0065] In the above formula, S 1 Represents similarity, β i and β' i They represent the i-th data in the standard control sequence and the standard current sequence obtained after normalization.

[0066] Preferably, in step S563, the calculation formula of the overlap degree is:

[0067]

[0068] In the above formula, S 2 Indicates the degree of coincidence, A indicates the parameter factor, B indicates the slope factor, A+B=1, n indicates the number of data in the current parameter sequence, which is also the number of data in the control parameter sequence, D i Indicates the i-th data in the current parameter sequence, D' i Indicates the i-th data in the control parameter sequence, K i Indicates the i-th slope data in the current parameter sequence, K'i Represents the i-th slope data in the control parameter sequence.

[0069] The technical solution also provides an electrical fault warning system for a photovoltaic grid-connected distribution box, comprising a processor and a memory, wherein the memory is used to store a computer program, and when the computer program is executed by the processor, the electrical fault warning method for the photovoltaic grid-connected distribution box is implemented.

[0070] Compared with the prior art, the present invention provides an electrical fault early warning method and system for a photovoltaic grid-connected distribution box, which has the following beneficial effects:

[0071] 1. The present invention establishes a real-time electrical parameter timing diagram and divides it into fault area, gradual change area and normal area. Combined with the matching analysis of the current sequence and the historical gradual change sequence, it can effectively identify the progressive degradation characteristics of electrical parameters in the photovoltaic grid-connected distribution box (such as the slow increase of contact point resistance and the attenuation of capacitance), and provide early warning before the fault occurs, significantly reducing the risk of equipment downtime or fire caused by hidden faults.

[0072] 2. The present invention adopts a dual threshold judgment mechanism of consistency and proximity, and flexibly adapts to the sensitivity of different fault types through dynamic weight allocation (such as parameter factor A and slope factor B). For example, it focuses on parameter differences for capacitor attenuation and trend changes for circuit breaker wear, thereby reducing the environmental fluctuation interference of traditional fixed threshold methods and greatly reducing the false alarm rate.

[0073] 3. The present invention eliminates data dimension differences caused by non-uniform sampling (such as sensor delay) through standardized time adjustment and electrical energy normalization processing, improves the comparability of energy values in different time windows, ensures the accuracy of fault feature extraction, and filters out instantaneous noise interference, thereby enhancing system robustness.

[0074] 4. The present invention combines historical fault logs with correlation analysis of current sequences, outputs corresponding fault logs and parameter change patterns during early warning, provides clear fault type diagnosis basis and maintenance decision support for operation and maintenance personnel, shortens fault investigation time, and improves the maintenance efficiency of photovoltaic distribution systems.

[0075] 5. The present invention constructs a benchmark interval and a tangent function to amplify the difference strategy, sensitively captures subtle numerical deviations between sequences, and combines the slope to calculate the curve overlap, comprehensively evaluates the parameter change trend and morphological matching, realizes multi-dimensional fault feature analysis, and improves the accuracy of progressive degradation identification. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0077] Figure 1 The figure is a flow chart of the electrical fault early warning method for the photovoltaic grid-connected distribution box of the present invention. DETAILED DESCRIPTION

[0078] To make the above-mentioned objectives, features, and advantages of the present invention more clearly understood, the present invention is further described below in detail with reference to the accompanying drawings and specific embodiments. This will enable a full understanding of how this application uses technical means to solve technical problems and achieve technical effects, and to implement the invention accordingly.

[0079] Those skilled in the art will appreciate that all or part of the steps in the following embodiments can be accomplished by instructing related hardware through a program. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0080] Table 1 below shows the corresponding relationship between several common progressive degradation characteristics and electrical parameter changes in photovoltaic grid-connected distribution boxes:

[0081]

[0082]

[0083] To address the problem in the prior art where fixed thresholds for electrical parameters are set, but it is difficult for operation and maintenance personnel to provide an early warning before a fault occurs due to progressive degradation characteristics, the present invention provides an electrical fault early warning method for a photovoltaic grid-connected distribution box. This method provides an early warning before a fault occurs due to progressive degradation characteristics, thereby enabling early preparation and reducing maintenance time for circuits within the photovoltaic grid-connected distribution box. The method specifically comprises the following steps:

[0084] S1. Real-time acquisition of electrical data and fault logs on each line in the photovoltaic grid-connected distribution box, and establishment of an electrical parameter timing diagram in chronological order. Deploy current sensors, voltage sensors, and temperature sensors on each line of the photovoltaic grid-connected distribution box to collect electrical parameters (such as DC side current, AC side voltage, bus temperature, etc.) in real time. The sensors transmit data to the central monitoring system through standard communication protocols (such as Modbus, CAN bus). The intelligent control unit of the distribution box (such as PLC or dedicated controller) monitors parameters such as circuit breaker status, insulation resistance, and harmonic distortion rate in real time. When an abnormal event (such as overcurrent, overvoltage, insulation failure) is detected, the fault timestamp, type, and corresponding electrical parameter value are automatically recorded to form a fault log. The real-time electrical data and the fault log are synchronized and integrated through the data acquisition module (such as SCADA system) to ensure that the timestamps are aligned to form an electrical parameter timing diagram, which is presented in the form of a line graph.

[0085] S2. On the electrical parameter timing diagram, the area where the timestamp of the fault log is located and is outside the parameter threshold is marked as the fault area, several consecutive moments before the fault area are marked as the gradual change area, and the remaining area is marked as the normal area. The following details the acquisition process of the fault area, the gradual change area, and the normal area. The fault area does not include data that does not generate a fault log and is outside the parameter threshold. Since this part of data does not correspond to the fault log, it is not placed in the fault area to avoid interference. In step S2, the following steps are specifically included:

[0086] S21. Obtain the timestamp and corresponding electrical parameters of the fault log, extract the specific time point (timestamp) when the fault occurred and the corresponding electrical parameter value from the fault log, establish an association between the fault event and the real-time monitoring data, and ensure the accuracy of subsequent analysis. For example, when the system detects a sudden increase in current at a certain moment, record the time point and current value as the starting point of the fault analysis.

[0087] S22, determining whether the electrical parameter corresponding to the timestamp of the fault log is outside the parameter threshold;

[0088] If yes, the electrical parameter and the corresponding time are marked as fault parameter and fault time respectively, and then the process goes to step S23;

[0089] If not, obtain the electrical parameter and the corresponding time that are closest to the timestamp and outside the parameter threshold, and mark the electrical parameter and the corresponding time as the fault parameter and the fault time respectively;

[0090] S23, marking each non-adjacent fault moment as a different fault area, and marking adjacent fault moments as the same fault area;

[0091] S24, sequentially determining whether adjacent moments on both sides of each fault area contain electrical parameters outside the parameter threshold;

[0092] If so, the adjacent time is marked as the fault time, and then the process returns to step S23 to check whether the electrical parameters at adjacent times on both sides of the fault area also exceed the parameter threshold to determine the complete time range affected by the fault;

[0093] If not, proceed to step S25;

[0094] S25, marking several moments before the fault area as a gradual change area, in which the parameters before the fault occur slowly deviate, and marking the remaining area as a normal area;

[0095] S3. Mark several consecutive moments before the current moment as the current area, and calculate the electrical energy at any moment according to the electrical parameters in the current area, fault area, and gradual change area in chronological order, and establish the current sequence, fault sequence, and gradual change sequence respectively. That is, each electrical parameter obtained by the sensor corresponds to a time, and then the electrical energy is calculated. The electrical energy is arranged in chronological order, and the electrical parameters in the current area, fault area, and gradual change area can be used to establish the current sequence, fault sequence, and gradual change sequence respectively. The specific steps include the following:

[0096] S31. Calculate the electrical energy at the next moment based on the electrical parameters at any two moments in the electrical parameter sequence diagram. The calculation formula for the electrical energy at any moment is:

[0097]

[0098] In the above formula, Q i represents the electrical energy at the i-th moment, E(t) represents the function of the change of electrical parameters over time, t i-1 and t i They represent the i-th moment respectively, and the changes in continuous electrical parameters (such as current and voltage) within the time window are converted into energy indicators to reflect the dynamic changes in the equipment's operating status. For example, the increase in resistance caused by aging of the contact points will cause increased energy loss. The integration result can reflect such gradual changes. Through integration and normalization operations, instantaneous interference (such as sensor noise) is filtered out, and the essential characteristics reflecting the health status of the equipment (such as energy loss trend) are extracted.

[0099] S32. Set the standard duration, and modify the duration of the electrical parameters at each adjacent moment to the standard duration, and then update the standard electrical energy at any moment; the calculation formula of the standard electrical energy is:

[0100]

[0101] In the above formula, Q' i represents the electrical energy at the i-th moment after update, Q i represents the electrical energy at the i-th moment before the update, ΔT i Indicates the duration between the i-th moment and the i-1-th moment, ΔT 0 Represents standard electrical energy. Actual data collection may have non-uniform sampling (such as network delay or sensor response difference). After standardization, the energy values ​​in different time windows are comparable.

[0102] S33, generating a current sequence and a gradual change sequence in the current area and the gradual change area according to the updated standard electrical energy;

[0103] The expression of the current sequence is: D={D1,D2,D3,…,D n}

[0104] The expression of the fault sequence is: G={G1,G2,G3,…,G k}

[0105] The expression of the gradual change sequence is: J={J1, J2, J3, ..., J m}

[0106] In the above formula, D and J represent the current sequence and the gradual sequence respectively, D n Indicates the standard electrical energy at the nth moment in the current sequence, J m represents the standard electrical energy at the mth moment in the gradient sequence, G k It represents the standard electrical energy at the kth moment in the fault sequence. The generation and analysis of the gradual change sequence can capture the parameter gradual change process before the fault (such as the slow decay of the capacitor capacity), providing data support for early warning.

[0107] S4, determining whether there is a suspicious sequence in the gradient region that is completely consistent with the current sequence;

[0108] If it exists, the fault log corresponding to the gradual change area is output and a warning signal is issued. The fault log output is the fault log closest to the end of the gradual change area.

[0109] If not, proceed to step S5;

[0110] Each gradient region may correspond to one or more historical fault events. When the system finds that the current sequence (i.e., the parameter changes before the current moment) completely matches the suspicious sequence in a certain historical gradient region, it indicates that the current state may be similar to the state before the historical fault occurred. Therefore, the corresponding fault log is output, which not only realizes early warning of faults, but also provides data support for operation and maintenance decisions, significantly improving the reliability and maintenance efficiency of photovoltaic distribution boxes.

[0111] S5. Select several reference sequences of the same length as the current sequence from the gradual degradation sequence, and calculate the degree of fit and closeness of each reference sequence with the current sequence. By calculating the degree of fit and closeness, it is possible to intuitively determine whether there is a reference sequence that meets the requirements of the degree of fit threshold and closeness threshold with the current sequence, and thus identify whether the current sequence exhibits the electrical parameter change pattern of the progressive degradation feature that appears before a fault occurs. Specifically, the steps include:

[0112] S51, using each moment in the gradual change sequence as a reference point, and selecting a specific moment in the gradual change sequence as a reference point for generating a starting position of a control sequence;

[0113] S52. Construct a time frame, and use the reference point as the starting point of the time frame and the length of the current sequence as the length of the time frame. Ensure that the reference sequence and the current sequence have the same time span to facilitate subsequent calculation and comparison. The starting point of the time frame is located on the gradual sequence, but the focus may be located at any position depending on the length of the time frame. It is only necessary to ensure the length of the time window.

[0114] S53 , arranging the standard electrical energy in each time frame in chronological order to generate a comparison sequence, marking the area corresponding to the comparison sequence on the electrical parameter timing diagram as the comparison area, and converting the original energy value into a comparable sequence form.

[0115] S54: Establish a reference interval that is less than or equal to one tangent function cycle, and normalize the reference sequence and the current sequence to the reference interval to generate a standard reference sequence and a standard current sequence, respectively, to eliminate dimensional differences, that is, to map energy values of different magnitudes to a unified interval to prevent the numerical range from affecting the similarity calculation. Specifically, the steps include the following:

[0116] S541. Obtain the maximum and minimum values of the standard electrical energy, and calculate the difference between the two to obtain the electrical energy range;

[0117] S542. Establish a reference interval: The expression of the reference interval is:

[0118] (-β, β)∈(kπ-π / 2, kπ+π / 2), where Z is a positive integer;

[0119] S543. Normalize the control sequence and the current sequence to the reference interval to generate a standard control sequence and a standard current sequence, respectively. The calculation formula for the data in the standard control sequence and the standard current sequence obtained after normalization is:

[0120]

[0121] In the above formula, β iRepresents the i-th data in the standard control sequence or the standard current sequence obtained after normalization, α i represents the i-th data in the control sequence or the current sequence, α represents the extreme difference in electrical energy, Indicates the average value of standard electrical energy.

[0122] S55. Calculate the degree of coincidence between the standard control sequence and the standard current sequence; the calculation formula for the degree of coincidence is:

[0123]

[0124] In the above formula, S 1 Represents similarity, β i and β' i They represent the i-th data in the standard control sequence and the standard current sequence obtained after normalization, respectively. There are n data in total. The difference is amplified by the tangent function to sensitively capture the numerical deviation between sequences.

[0125] S56: Calculate the degree of overlap between the standard control sequence and the standard current sequence. The calculation of the degree of overlap specifically includes the following steps:

[0126] S561. Acquire electrical parameters at the time corresponding to the standard control sequence and the standard current sequence to obtain a control parameter sequence and a current parameter sequence respectively;

[0127] S562, respectively calculating the slopes of any two parameters in the reference parameter sequence and the current parameter sequence;

[0128] S563. Calculate the degree of overlap of the curves in the electrical parameter timing diagram corresponding to the reference parameter sequence and the current parameter sequence based on the slope. The calculation formula for the degree of overlap is:

[0129]

[0130] In the above formula, S 2 Indicates the degree of coincidence, A indicates the parameter factor, B indicates the slope factor, A+B=1, n indicates the number of data in the current parameter sequence, which is also the number of data in the control parameter sequence, D i Indicates the i-th data in the current parameter sequence, D' i Indicates the i-th data in the control parameter sequence, K i Indicates the i-th slope data in the current parameter sequence, K' iIt represents the i-th slope data in the control parameter sequence, and combines the parameter value difference with the trend slope difference to comprehensively reflect the overall morphological matching degree of the sequence. By adjusting the dynamic weight distribution of A and B (such as A = 0.7, B = 0.3), it can flexibly adapt to the sensitivity of different fault types to parameter values or trends. For example, for capacitor attenuation fault (sensitive to parameter values), set A = 0.8, B = 0.2; for circuit breaker wear (sensitive to trend), set A = 0.3, B = 0.7.

[0131] S6. Determine whether there is a control sequence whose degree of fit and closeness to the current sequence are both smaller than the fit threshold and closeness threshold, respectively;

[0132] If it exists, the fault log corresponding to the control sequence is output and an early warning signal is issued;

[0133] If it does not exist, then end.

[0134] In step S6, the following steps are specifically included:

[0135] S61, setting a coincidence threshold, and determining in sequence whether the coincidence degree between each reference sequence and the current sequence is less than the coincidence threshold;

[0136] If yes, proceed to step S62;

[0137] If not, then end.

[0138] S62: Set a coincidence threshold, and determine in sequence whether the coincidence between each reference sequence and the current sequence is less than the coincidence threshold;

[0139] If so, output the fault log corresponding to the control sequence;

[0140] If not, then end.

[0141] Assume that the historical gradual change sequence shows that the current energy rises slowly before a fault, which is specifically manifested as follows:

[0142] Normalized sequence: J = [0.2, 0.5, 0.8, 1.0] (reference interval [-1, 1]);

[0143] Current sequence: D = [0.3, 0.6, 0.7, 1.1].

[0144] Step S55 calculates the degree of fit:

[0145] S 1 =|tan(0.2-0.3)|+|tan(0.5-0.6)|+|tan(0.8-0.7)|+|tan(1.0-1.1)|=0.10+0.11+0.10+0.10=0.41

[0146] Step S56 calculates the closeness: (assuming A=0.6, B=0.4):

[0147] Parameter difference items:

[0148] Slope difference term:

[0149] S 2 =0.6×0.25+0.4×0.15=0.21

[0150] If the threshold S is set 1 <0.5, and S 2 <0.3, the current sequence matches successfully and triggers an early warning.

[0151] The technical solution also provides an electrical fault warning system for a photovoltaic grid-connected distribution box, including a processor and a memory. The memory is used to store a computer program. When the computer program is executed by the processor, an electrical fault warning method for the photovoltaic grid-connected distribution box is implemented.

[0152] It should be noted that the systems provided in the above embodiments are merely illustrated by the division of the above functional modules when implementing their functions. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In addition, the systems and method embodiments provided in the above embodiments are based on the same concept. The specific implementation process is detailed in the method embodiment and will not be repeated here.

[0153] The above embodiments provide a detailed introduction to the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for early warning of electrical faults in a photovoltaic grid-connected distribution box, characterized in that: The method specifically comprises the following steps: S1. Real-time acquisition of electrical data and fault logs on each line in the photovoltaic grid-connected distribution box, and establishment of an electrical parameter timing diagram in chronological order; S2. On the electrical parameter timing diagram, mark the area outside the parameter threshold where the timestamp of the fault log is located as the fault area, mark several consecutive moments before the fault area as the gradual change area, and mark the remaining area as the normal area; S3. Mark several consecutive moments before the current moment as the current region, and calculate the electrical energy at any moment according to the electrical parameters in the current region, the fault region, and the gradual change region in chronological order, and establish the current sequence, the fault sequence, and the gradual change sequence respectively; S4, determining whether there is a suspicious sequence in the gradient region that is completely consistent with the current sequence; If it exists, the fault log corresponding to the gradient area is output and an early warning signal is issued; If not, proceed to step S5; S5. Selecting several reference sequences of equal length to the current sequence from the gradual sequence, and calculating the degree of agreement and closeness between each reference sequence and the current sequence; S6. Determine whether there is a control sequence whose degree of fit and closeness to the current sequence are both smaller than the fit threshold and closeness threshold, respectively; If it exists, the fault log corresponding to the control sequence is output and an early warning signal is issued; If it does not exist, then end.

2. The electrical fault early warning method according to claim 1, characterized in that: In step S2, the following steps are specifically included: S21. Obtain the timestamp and corresponding electrical parameters of the fault log; S22, determining whether the electrical parameter corresponding to the timestamp of the fault log is outside the parameter threshold; If yes, the electrical parameter and the corresponding time are marked as fault parameter and fault time respectively, and then the process goes to step S23; If not, obtain the electrical parameter and the corresponding time that are closest to the timestamp and outside the parameter threshold, and mark the electrical parameter and the corresponding time as the fault parameter and the fault time respectively; S23, marking each non-adjacent fault moment as a different fault area, and marking adjacent fault moments as the same fault area; S24, sequentially determining whether adjacent moments on both sides of each fault area contain electrical parameters outside the parameter threshold; If yes, mark the adjacent time as the fault time, and then return to step S23; If not, proceed to step S25; S25: Mark several moments before the fault area as gradual change areas, and mark the remaining areas as normal areas.

3. The electrical fault early warning method according to claim 1, characterized in that: In step S3, the following steps are specifically included: S31. Calculate the electrical energy at the next moment based on the electrical parameters at any two moments in the electrical parameter sequence diagram. The calculation formula for the electrical energy at any moment is: In the above formula, Q i represents the electrical energy at the i-th moment, E(t) represents the function of the change of electrical parameters over time, t i-1 and t i Respectively represent the i-th moment; S32. Set the standard duration, and modify the duration of the electrical parameters at each adjacent moment to the standard duration, and then update the standard electrical energy at any moment; the calculation formula of the standard electrical energy is: In the above formula, Q' i represents the electrical energy at the i-th moment after update, Q i represents the electrical energy at the i-th moment before the update, ΔT i Indicates the duration between the i-th moment and the i-1-th moment, ΔT 0 Indicates standard electrical energy; S33, generating a current sequence and a gradual change sequence in the current area and the gradual change area according to the updated standard electrical energy; The expression of the current sequence is: D={D1,D2,D3,…,D n } The expression of the fault sequence is: G={G1,G2,G3,…,G k } The expression of the gradual change sequence is: J={J1, J2, J3, ..., J m } In the above formula, D and J represent the current sequence and the gradual sequence respectively, D n Indicates the standard electrical energy at the nth moment in the current sequence, J m represents the standard electrical energy at the mth moment in the gradient sequence, G k It represents the standard electrical energy at the kth moment in the fault sequence.

4. The electrical fault early warning method according to claim 1, characterized in that: In step S5, the following steps are specifically included: S51, taking each moment in the gradual change sequence as a reference point; S52. Construct a time frame, and use the reference point as the starting point of the time frame and the length of the current sequence as the length of the time frame; S53, arranging the standard electrical energy in each time frame in order to generate a control sequence, and marking the area corresponding to the control sequence on the electrical parameter timing diagram as a control area; S54. Establish a reference interval that is less than or equal to one tangent function period, and normalize the reference sequence and the current sequence to the reference interval to generate a standard reference sequence and a standard current sequence, respectively. S55, calculating the degree of agreement between the standard control sequence and the standard current sequence; S56. Calculate the degree of overlap between the standard control sequence and the standard current sequence.

5. The electrical fault early warning method according to claim 4, characterized in that: In step S54, the following steps are specifically included: S541. Obtain the maximum and minimum values of the standard electrical energy, and calculate the difference between the two to obtain the electrical energy range; S542. Establish a reference interval: The expression of the reference interval is: (-β, β)∈(kπ-π / 2, kπ+π / 2), where Z is a positive integer; S543. Normalize the control sequence and the current sequence to the reference interval to generate a standard control sequence and a standard current sequence, respectively. The calculation formula for the data in the standard control sequence and the standard current sequence obtained after normalization is: In the above formula, β i Represents the i-th data in the standard control sequence or the standard current sequence obtained after normalization, α i represents the i-th data in the control sequence or the current sequence, α represents the extreme difference in electrical energy, Indicates the average value of standard electrical energy.

6. The electrical fault early warning method according to claim 1, characterized in that: In step S56, the following steps are specifically included: S561. Acquire electrical parameters at the time corresponding to the standard control sequence and the standard current sequence to obtain a control parameter sequence and a current parameter sequence respectively; S562, respectively calculating the slopes of any two parameters in the reference parameter sequence and the current parameter sequence; S563: Calculate the degree of overlap of the curves in the electrical parameter timing diagram corresponding to the comparison parameter sequence and the current parameter sequence according to the slope.

7. The electrical fault early warning method according to claim 1, characterized in that: In step S6, the following steps are specifically included: S61, setting a coincidence threshold, and determining in sequence whether the coincidence degree between each reference sequence and the current sequence is less than the coincidence threshold; If yes, proceed to step S62; If not, then end. S62: Set a coincidence threshold, and determine in sequence whether the coincidence between each reference sequence and the current sequence is less than the coincidence threshold; If so, output the fault log corresponding to the control sequence; If not, then end.

8. The electrical fault early warning method according to claim 4, characterized in that: In step S54, the calculation formula of the degree of fit is: In the above formula, S 1 Represents similarity, β i and β' i They represent the i-th data in the standard control sequence and the standard current sequence obtained after normalization.

9. The electrical fault early warning method according to claim 6, characterized in that: In step S563, the calculation formula of the overlap degree is: In the above formula, S 2 Indicates the degree of coincidence, A indicates the parameter factor, B indicates the slope factor, A+B=1, n indicates the number of data in the current parameter sequence, which is also the number of data in the control parameter sequence, D i Indicates the i-th data in the current parameter sequence, D' i Indicates the i-th data in the control parameter sequence, K i Indicates the i-th slope data in the current parameter sequence, K' i Represents the i-th slope data in the control parameter sequence.

10. A system for implementing the electrical fault early warning method of the photovoltaic grid-connected distribution box according to any one of claims 1 to 9, characterized in that: The device comprises a processor and a memory, wherein the memory is used to store a computer program, and when the computer program is executed by the processor, the electrical fault early warning method for the photovoltaic grid-connected distribution box according to any one of claims 1 to 9 is implemented.

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