Power distribution network residual current protection method and system based on distributed photovoltaic power supply

Abstract

The application relates to the technical field of residual current protection, in particular to a power distribution network residual current protection method and system based on a distributed photovoltaic power supply, which comprises the following steps: acquiring a zero sequence current waveform in a disturbance period and identifying a mutation node, analyzing fluctuation rhythm and trend to construct a response structure, screening a response fragment capable of triggering protection and adjusting a starting point and sequence, completing action trigger rhythm merging, and generating a residual current protection strategy; in the application, a response fragment set with trend consistency and rhythm continuity is constructed through sequence relationship extraction of the mutation node and the fluctuation rhythm, key paragraphs capable of triggering protection are screened in combination with change coordination relationship between sections, the trigger sequence and starting point position are adjusted according to trend continuity, the starting time sequence matching degree is improved, behavior stability is judged through trend continuity, rhythm merging of the response structure is realized, an action strategy with directionality and continuity is output, and the precise control ability of protection response under variable disturbance is enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of residual current protection, in particular to a power distribution network residual current protection method and system based on distributed photovoltaic power supply. BACKGROUND

[0002] The technical field of residual current protection relates to a protection mechanism in a power system for detecting and cutting off residual current generated due to insulation failure or equipment abnormality, the core matters of which include zero sequence current detection principle, residual current action criterion setting, protection device triggering mechanism, etc., which is an important technical means to ensure the safe operation of the power system, prevent electrical fire and electric shock accidents, and is widely used in urban and rural power distribution systems and new energy access scenarios. With photovoltaic power generation as an important component of clean and renewable energy, it plays an increasingly key role in energy structure transformation. However, photovoltaic power generation output has volatility and uncertainty, and its widespread access has put higher requirements on power distribution network operation management and protection, especially in distributed access scenarios, the traditional protection method faces the problem of insufficient adaptability. Among them, the traditional residual current protection method for power distribution network based on distributed photovoltaic power supply refers to the use of zero sequence current detection-based fixed setting strategy to realize residual current fault detection after the photovoltaic system is connected to ensure system safety and stable operation, which generally monitors the three-phase current vector and changes in real time through a zero sequence current transformer, combines with a preset action threshold, and completes fault removal through a relay or electronic switch control unit. The protection logic is constructed according to standards such as IEC61008 or GB6829, and the action judgment generally uses a static setting method, which does not fully consider the changes in working conditions caused by the dynamic characteristics of photovoltaic power generation.

[0003] Since the criterion setting is based on a fixed threshold and depends on the change in current instantaneous amplitude, the evolution trend in the disturbance process is not dynamically modeled, making it difficult to identify the current behavior evolution path in the face of persistent disturbance and overlapping multi-section current fluctuations, lacking the ability to identify and reconstruct the structure of the current change phase, for example, in the case of continuous current disturbance caused by short-time flicker after photovoltaic access, the protection device is difficult to distinguish between normal fluctuations and potential faults according to the fixed criterion, and is prone to response timing misalignment or trigger priority imbalance, resulting in protection action delay or false triggering, which affects the response accuracy and operation reliability of the power distribution network protection system under the conditions of multi-source access and frequent load changes. SUMMARY

[0004] In order to solve the technical problems existing in the prior art, the embodiments of the present application provide a residual current protection method for power distribution network based on distributed photovoltaic power supply, comprising the following steps:

[0005] In order to achieve the above purpose, the present application adopts the following technical scheme: a residual current protection method for power distribution network based on distributed photovoltaic power supply, comprising the following steps:

[0006] S1: Extract the zero sequence current waveform in the disturbance period of the distributed photovoltaic access point, calibrate the starting section, middle section and ending section of the change, identify the evolution mode according to the change trend, inflection point conversion and rhythm difference, and generate a contour mutation marker sequence;

[0007] S2: Based on the contour mutation marker sequence, identify the fluctuation form of the disturbance response, analyze the rhythm, persistence and trend of the initial stage, middle stage and recovery period, construct the response evolution structure, and classify it into a fluctuation structure section group;

[0008] S3: Combine the fluctuation structure section group and the contour mutation marker sequence, establish time sequence association pair by pair, judge the consistency of the trend and the trend, comb the relationship of the response combination, select the response segment of the trigger protection condition threshold, and generate an action trigger section list;

[0009] S4: Based on the action trigger section list, locate the response segment starting point, trace the trend of the previous section, if consistent, move the starting point forward, rearrange the response segment sequence, and adjust the starting priority, and generate an action starting position list;

[0010] S5: Based on the action starting position list, judge the stability of the response segment, sort the action response priority, structure the execution rhythm, and generate a residual current protection scheme for the power distribution network.

[0011] As a further scheme of the application, the contour mutation marker sequence includes a starting change node, a middle fluctuation feature point and an ending trend node, the fluctuation structure section group includes a disturbance form subarea, a curve trend segment and a phased fluctuation feature, the action trigger section list includes a trigger starting position, a trend consistency segment and a response cooperative combination, the action starting position list includes starting sequence information, trend continuation indicators and response segment adjustment relationships, and the residual current protection scheme for the power distribution network includes response priority, action rhythm structure and relay output rules.

[0012] As a further scheme of the application, the definition of the protection condition threshold refers to when the characteristic change of the zero sequence current waveform reaches the minimum judgment standard required to trigger the protection action in the disturbance response.

[0013] As a further scheme of the application, the definition of the trace of the previous section trend refers to the analysis of the fluctuation trend forward after the starting point of the action response segment, and if the current trend is consistent, the process of moving the response starting point forward is called tracing the trend of the previous section.

[0014] As a further scheme of the application, the specific steps of S1 are:

[0015] S101: Obtain the zero sequence current waveform in the distributed photovoltaic power supply access point disturbance period, extract the change amplitude, slope value and first-order difference value in each period, construct a difference index set based on the three parameters, judge the start and end positions of the segment whose change rate exceeds the zero sequence current disturbance threshold in the waveform, and generate a current change interval boundary pair;

[0016] S102: Call the current change interval boundary pair, calculate the first and second derivatives of the current waveform in the interval, determine the trend inflection point according to the derivative sign and extreme value position, number the fluctuation starting point, inflection point and end point in the sampling order, and generate a current fluctuation feature point sequence;

[0017] S103: Based on the current fluctuation feature point sequence, identify the arrangement direction of the wave peak and wave trough and the rhythm ratio of adjacent segments, extract the time index and amplitude change of the trend mutation point, construct a segment connection relationship matrix, and generate a contour mutation marker sequence.

[0018] As a further scheme of the present application, the specific steps of S2 are:

[0019] S201: Call the contour mutation marker sequence, detect the segment whose fluctuation amplitude exceeds the disturbance response recognition threshold in the zero sequence current, extract the segment set of the initial, middle and recovery periods of the disturbance according to the continuous time and amplitude change, and obtain the disturbance stage fluctuation segment set;

[0020] S202: Based on the disturbance stage fluctuation segment set, extract the duration, fluctuation frequency and rhythm period of the stage segment, calculate the stability coefficient, and judge the continuity state to obtain the stage fluctuation characteristic index group;

[0021] S203: According to the stage fluctuation characteristic index group, calculate the stability difference value between segments, classify the characteristic similar segments according to the trend change direction, establish a structure mapping relationship, and generate a fluctuation structure section group.

[0022] As a further scheme of the present application, the specific steps of S3 are:

[0023] S301: Call the fluctuation structure section group and the contour mutation marker sequence, and establish a match between the structure segment and the mutation point according to the sampling time, judge the time sequence of the starting point of each structure segment and the mutation point, screen out the time arrangement consistent segments, and generate a structure mutation matching pair sequence;

[0024] S302: According to the structure mutation matching pair sequence, compare the direction vectors of the fluctuations before and after the structure segment and the mutation point, judge whether the trend direction is consistent, and mark the consistent combination to obtain a trend consistent combination sequence;

[0025] S303: Based on the trend consistent combination sequence, the amplitude change and duration of the structural segment in the combination are extracted, and compared with the protection condition threshold value, the response segment meeting the trigger condition is screened, and the action trigger segment list is generated.

[0026] As a further scheme of the present application, the specific steps of S4 are:

[0027] S401: Call the action trigger segment list, locate the response segment start position, trace back the current segment current direction, judge whether it is consistent with the current segment trend, if consistent, extend the response segment start point, generate the trend extension start point set;

[0028] S402: According to the trend extension start point set, extract the sampling time of the response segment after extension, sort according to the start point time, judge whether the time sequence is dislocated, and unify the sequence, get the response segment time sequence table;

[0029] S403: Based on the response segment time sequence table, extract the trend direction, duration and amplitude change, calculate the trend continuation score value, adjust the paragraph priority according to the score, generate the action start position list.

[0030] As a further scheme of the present application, the specific steps of S5 are:

[0031] S501: Call the action start position list, extract the start sequence and trend continuity parameter of the response segment, judge the trend direction and fluctuation stability of each segment start position, calculate the trend duration and amplitude change amplitude, establish the corresponding stability score matrix, generate the response segment stability score group;

[0032] S502: According to the response segment stability score group, combine the time connection relationship between action segments, extract the start and end point index difference between adjacent paragraphs, judge whether the connection state is continuous, and rearrange the response order according to the continuity priority, get the response segment priority list;

[0033] S503: Based on the response segment priority list, integrate the action rhythm change cycle and response continuation time length, match the trigger segment position and action rhythm structure, form the time sequence output set with trigger identifier, generate the residual current protection scheme of distribution network.

[0034] The residual current protection system of the distribution network based on the distributed photovoltaic power supply comprises:

[0035] The contour marker extraction module is used to realize S1: extracting the zero sequence current waveform in the disturbance period of the distributed photovoltaic access point, marking the starting segment, intermediate segment and ending segment of the change, identifying the evolution mode according to the trend of three segment change, inflection point conversion and rhythm difference, and generating the contour mutation marker sequence;

[0036] The fluctuation structure categorizing module is configured to implement S2: identifying fluctuation patterns of the disturbance response based on the sequence of profile mutation markers, analyzing the rhythm, duration and trend of the initial stage, middle stage and recovery stage, constructing a response evolution structure, and categorizing into a fluctuation structure section group;

[0037] The response segment screening module is configured to implement S3: combining the fluctuation structure section group and the sequence of profile mutation markers, establishing a time sequence association pair by pair, judging the consistency of the sequence and trend, combing the relationship of the response combination, screening the response segment triggering the protection condition threshold, and generating an action trigger section list;

[0038] The start priority adjustment module is configured to implement S4: based on the action trigger section list, locating the response segment starting point, tracing the trend of the previous segment, moving the starting point forward if consistent, rearranging the response segment sequence, adjusting the start priority, and generating an action start position list;

[0039] The trigger rhythm merging module is configured to implement S5: based on the action start position list, judging the response segment stability, sorting the action response priority, structurally integrating the execution rhythm, and generating a residual current protection scheme for the power distribution network.

[0040] Compared with the prior art, the application has the following advantages and positive effects:

[0041] In the application, the response segment set with trend consistency and rhythm continuity is constructed through the sequence relationship extraction of mutation nodes and fluctuation rhythm, the key paragraphs that can trigger protection are screened in combination with the change coordination relationship between sections, the trigger sequence and starting point position are adjusted according to the trend continuity, the start time sequence matching degree is improved, the behavior stability is judged through the trend continuity, the rhythmized merging of the response structure is realized, the action strategy with directionality and continuity is output, and the precise control ability of the protection response under variable disturbance is enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0043] Figure 1 The figure is a step flowchart of the application;

[0044] Figure 2 The figure is a S1 refinement diagram of the application;

[0045] Figure 3 The figure is a S2 refinement diagram of the application;

[0046] Figure 4 S3 refinement schematic diagram of the present application;

[0047] Figure 5 S4 refinement schematic diagram of the present application;

[0048] Figure 6 S5 refinement schematic diagram of the present application;

[0049] Figure 7 System module diagram of the present application. DETAILED DESCRIPTION

[0050] The technical solutions in the present application will be described below with reference to the drawings.

[0051] In the embodiments of the present application, the words such as "example", "for example" are used to represent as an example, illustration or description. Any embodiment or design scheme described as "example" in the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the word "example" is intended to present the concept in a specific manner. In addition, in the embodiments of the present application, the meaning expressed by "and / or" can be both, or can be one of the two.

[0052] In the embodiments of the present application, "image" and "picture" can be used interchangeably at times. It should be pointed out that when the distinction is not emphasized, the meanings expressed are consistent. "Of", "corresponding" and "relevant" can be used interchangeably at times. It should be pointed out that when the distinction is not emphasized, the meanings expressed are consistent.

[0053] In the embodiments of the present application, sometimes the subscript such as W1 can be written in the form of non-subscript such as W1. When the distinction is not emphasized, the meanings expressed are consistent.

[0054] To make the technical problems, technical solutions and advantages to be solved by the present application clearer, specific embodiments will be described in detail below with reference to the drawings.

[0055] Please refer to Figure 1 The embodiments of the present application provide a residual current protection method for a power distribution network based on a distributed photovoltaic power supply, which comprises the following steps:

[0056] S1: Obtain the zero sequence current waveform of the distributed photovoltaic power supply access point in the disturbance period, calibrate the starting section, intermediate fluctuation section and ending section of the current sharp change region, identify the morphological evolution mode through the change trend, inflection point conversion trend and change rhythm of adjacent sections, incorporate the structural mutation points into the continuous identification sequence in chronological order and establish the contour node relationship, and generate a contour mutation marker sequence;

[0057] S2: Call the profile mutation marker sequence, identify the fluctuation pattern area covered by the disturbance response in the zero sequence current, analyze the change rhythm, duration characteristics and stability trend shown in the initial, middle and recovery periods of the disturbance, construct the response evolution structure according to the fluctuation continuity and curve trend change, and structure the fluctuation section group by placing the differentiated stages in the structure, and generate the fluctuation structure section group;

[0058] S3: Call the fluctuation structure section group and the profile mutation marker sequence, establish a pair of associations according to the time relationship, arrange and judge the order of each group between the starting point and the mutation point, and check whether there is a consistent trend direction in the structure form, comb the cooperative relationship of change combination in the response mode, screen the response fragments that can trigger the protection condition threshold, and generate the action trigger section list;

[0059] S4: Call the action trigger section list, locate the position where the current starting point of the response section is located, and trace back the current evolution direction of the previous change section. If the previous section has the same evolution trend, move the starting point of the current response section forward, and rearrange the order of multiple response sections. Through the extension judgment of the overall trend of the response section, adjust the priority relationship of the starting priority, and generate the action starting position list;

[0060] S5: Call the starting order in the action starting position list, judge the stability of the starting behavior of the response section, arrange the action response priority according to the paragraph connection position, structure the action execution rhythm in the paragraph, and form the output content with the relay triggering attribute, and generate the residual current protection scheme of the distribution network.

[0061] The profile mutation marker sequence includes the starting change node, the middle fluctuation feature point and the ending trend node. The fluctuation structure section group includes the disturbance form partition, the curve trend fragment and the stage fluctuation feature. The action trigger section list includes the trigger starting position, the trend consistency fragment and the response cooperative combination. The action starting position list includes the starting order information, the trend continuation index and the response section adjustment relationship. The residual current protection scheme of the distribution network includes the response priority level, the action rhythm structure and the relay output rule.

[0062] Please refer to Figure 2 , the specific steps of S1 are:

[0063] S101: Obtain the zero sequence current waveform of the distributed photovoltaic power supply access point in the disturbance period, extract the change amplitude, slope value and first-order difference value in each period, construct a difference index set based on the three parameters, judge the starting and ending positions of the segment whose change rate exceeds the zero sequence current disturbance threshold in the waveform, and generate the current change interval boundary pair.

[0064] Firstly, the three-phase current signals need to be synchronously collected at the access point, the sampling frequency is set to 10 kHz to ensure that the time domain resolution meets the demand of dynamic waveform extraction, the A, B and C three-phase currents obtained by sampling are sequentially superimposed to form a zero sequence current, forming an original waveform data sequence, in the actual sampling scene, set the first collection cycle to 2 seconds, corresponding to 200000 sampling points, when the sampling data is processed by cycle division, 200000 points are divided into 100 complete cycles according to 50Hz power frequency cycle, each cycle contains 2000 sampling points, then in each cycle, the difference between the maximum value and the minimum value of the zero sequence current in the cycle is calculated as the change amplitude of the cycle, for example, the maximum value of the 10th cycle is 3.2A and the minimum value is 1.1A, then the cycle amplitude is 2.1A, continue to solve the difference value of the continuous points in the cycle, extract the first difference sequence, for example, the first sampling point is 1.2A and the second is 1.25A, then the difference is 0.05A, after repeating the execution to obtain the difference sequence, further calculate the change rate between adjacent difference points as the slope, for example, the previous difference is 0.05A and the next difference is 0.15A, the slope is 0.1A / 0.1ms, that is, 1000A / s, combine the change amplitude, the maximum difference and the maximum slope value extracted in each cycle into a cycle feature three-tuple, construct the feature set of all cycles, then set the reference threshold for disturbance judgment, the amplitude threshold is recommended to be set to 1.5A, the difference threshold is set to 0.2A, and the slope threshold is set to 300A / s, the threshold is set based on the experience data that the average fluctuation of zero sequence current is not more than 0.8A, the difference is not more than 0.1A, and the slope is not more than 150A / s in the field measurement, so that the disturbance threshold is set to 2 times the upper limit of the experience, whether any one of the three parameters exceeds the corresponding threshold is judged for each cycle, if yes, it is marked as a disturbance cycle, after traversing the 100 cycles in turn, the disturbance cycle numbers are extracted, for example, the 12th, 13th and 14th cycles all meet the disturbance condition, then a group of boundary pairs is formed as (12, 14), and finally the current change interval boundary pair is obtained.

[0065] S102: Call the current change interval boundary pair, calculate the first and second derivatives of the current waveform in the interval, determine the trend inflection point according to the derivative sign and extreme value position, number the fluctuation starting point, inflection point and termination point in the sampling order, and generate a current fluctuation feature point sequence;

[0066] First, according to the current change interval boundary pair obtained in the preceding step, such as (12, 14), (28, 31), etc., the corresponding complete data segment of each group is extracted from the original current sampling data. Taking (12, 14) as an example, the corresponding sampling points are the 22001th point to the 28000th point. In this data segment, the first-order derivative operation is sequentially performed on the sampling points, that is, the difference between the current values of the consecutive sampling points is divided by the sampling time interval. The sampling interval is 0.1 ms. Therefore, for the 24001th point and the 24000th point, the values are 1.2 A and 1.1 A, respectively, and the first-order derivative is 1 A / ms. Then, the difference processing is performed on the derivative sequence to obtain the second-order derivative, that is, the difference between the consecutive derivative values is divided by 0.1 ms to obtain the change rate. For example, the two derivative values are 1.0 A / ms and 1.4 A / ms, and the corresponding second-order derivative is 4 A / ms². All the first-order and second-order derivative values are recorded as a vector sequence. On this basis, the sign change point is found. If the first-order derivative changes from positive to negative, it indicates that the waveform changes from rising to falling, and the maximum value point is determined. If it changes from negative to positive, it is the minimum value point. The sign change is judged point by point in this way. All the extreme value point number positions are marked in the sampling segment, and the derivative value significantly changed region before and after the extreme value point is found. The fluctuation starting point, inflection point and end point are recorded. For example, the starting point is 24012, the inflection point is 24045, and the end point is 24090. They are sequentially numbered and recorded as a complete fluctuation characteristic segment according to the sampling order. The above processing is repeated for all the fluctuation events in the disturbance section, and finally the current fluctuation characteristic point sequence is formed.

[0067] S103: Based on the current fluctuation characteristic point sequence, the arrangement direction of the wave peak and wave trough and the adjacent segment rhythm proportion are identified, the time index of the trend mutation point and the amplitude change amount are extracted, the segment connection relationship matrix is constructed, and the contour mutation label sequence is generated.

[0068] For the extracted current fluctuation feature point sequence, such as {24012, 24045, 24090}, {24150, 24185, 24230} and the like, further waveform structure analysis is performed on each group of feature points. The middle point in each group of three points is an extreme point, which needs to be judged as a wave peak or a wave trough. If the current value of the 24045 point is 3.1A, the current value of the starting point 24012 is 2.2A, and the current value of the ending point 24090 is 2.5A, then the fluctuation segment is a wave peak. Similarly, after judging the extreme properties of all fluctuation segments, the wave peak-valley arrangement direction is recorded. Then, the time interval between the starting point and the ending point of adjacent fluctuation segments is calculated. If the ending point of fluctuation 1 is 24090, the corresponding time is 2.409 seconds, the starting point of fluctuation 2 is 24150, the corresponding time is 2.415 seconds, and the interval is 0.006 seconds. At the same time, the amplitude change of the two fluctuation segments is calculated, for example, the fluctuation 1 is 3.1A-2.2A=0.9A, the fluctuation 2 is 2.6A-1.8A=0.8A, the amplitude ratio between the two segments is 0.9 / 0.8=1.125, and the set mutation judgment ratio threshold is 1.4. Therefore, this segment does not constitute a mutation. For example, a fluctuation amplitude of 2.0A is compared with the previous segment of 0.8A, and the ratio is 2.5. It is determined as a mutation segment. The mutation ratio threshold is set to 1.75 times the average of the maximum observed amplitude according to the average of the stable running amplitude in the early stage. If the historical average is 0.6A, the mutation threshold is set to 1.05A. For all fluctuation segments, the interval time and amplitude ratio with the previous segment are judged. The segment that meets the ratio threshold is regarded as a mutation segment, and the inflection point number and time are recorded in the mutation mark list. Then, the connection relationship between the segments is established one by one. If the time interval between two segments is less than 0.01 seconds, they are considered to be connected, and a connection matrix is constructed. The profile mutation mark sequence is generated according to the mutation mark and the connection relationship of all fluctuation segments, such as [0, 1, 0, 1, 1, 0], which represents the binary sequence of whether the corresponding segment is a mutation.

[0069] Please refer to Figure 3 , the specific steps of S2 are:

[0070] S201: Call the profile mutation mark sequence, detect the segment of the zero sequence current whose fluctuation amplitude exceeds the disturbance response recognition threshold, extract the segment set of the initial, middle and stable periods of the disturbance according to the continuous time and amplitude change, and obtain the disturbance stage fluctuation segment set;

[0071] The call contour mutation marker sequence is called as an input basis, all fluctuation section numbers and their corresponding time indexes with a mutation marker value of 1 are read, the start and end time of each section and the maximum and minimum values of the zero sequence current waveform in the section are obtained, and the fluctuation amplitude of each section is calculated. For example, the start current is 1.2 A and the end current is 3.0 A in a certain fluctuation section, and the fluctuation amplitude is 1.8 A. Then, a disturbance response recognition threshold is set to determine whether the fluctuation amplitude meets the significant disturbance standard. The threshold is determined based on the mean and maximum values of the fluctuation amplitude in the historical stable operation state. If the historical mean is 0.6 A and the maximum is 1.2 A, the disturbance recognition threshold is determined to be 1.5 A. For each mutation section, it is determined whether the fluctuation amplitude is greater than the threshold. If it is greater, the section is regarded as a disturbance segment and is included in the recognition range. Then, the time intervals of adjacent segments are compared in time sequence. If the time interval is less than the set continuous time threshold (0.1 seconds), it is regarded as a continuous disturbance process of the same stage. If it is greater, the continuity is broken and a new stage segment group is formed. In each stage segment group, the fluctuation amplitude and time length of each section are divided into intervals according to the time sequence. The disturbance initial recognition time threshold is set to 0.3 seconds, and the recovery period time threshold is set to 0.5 seconds. If a certain segment group starts within 0.3 seconds, it is an initial segment. The middle segment is the next 0.4 seconds, and the end 0.5 seconds is a recovery period segment. Further, whether it belongs to the initial stage, whether the current rising trend is established, whether the middle segment is fluctuant, and whether the recovery period is in a downward and convergent trend are judged according to the current value change characteristics in the segment. For example, the current rises from 1.2 A to 3.5 A in the initial segment, and the current decreases from 3.4 A to 2.0 A in the recovery period segment, and the fluctuation amplitude is less than 0.3 A. Therefore, the corresponding stage characteristic conditions are met, and the fluctuation segment set of the disturbance stage is classified and summarized according to the conditions.

[0072] S202: Based on the disturbance stage fluctuation segment set, the duration, fluctuation frequency and rhythm period of the stage segment are extracted, the stability coefficient is calculated, and the continuity state is judged to obtain the stage fluctuation characteristic index group.

[0073] Based on the obtained set of disturbance phase fluctuation segments, the start and end time points of each phase segment are extracted one by one, and the duration is calculated, that is, the termination time minus the start time. For example, the start time of a certain middle segment is 1.05 seconds, and the end time is 1.75 seconds, so the duration is 0.7 seconds. Continue to count the number of local extreme points, that is, the fluctuation frequency, in the segment. The number of extreme points is determined by the forward difference and sign change. If there are 5 extreme points in 0.7 seconds, the fluctuation frequency is 5, and the rhythm period can be defined as the duration divided by the fluctuation frequency, that is, 0.7 seconds / 5=0.14 seconds. After performing the above operation on each segment, the duration, fluctuation frequency and rhythm period of each segment are obtained. Then, the stability coefficient of the segment is calculated according to the mean-variance relationship between the fluctuation frequency and the rhythm period. The stability coefficient is defined as the ratio of the standard deviation to the average value of the rhythm period sequence. If the rhythm periods of multiple segments in a phase are 0.13 seconds, 0.14 seconds and 0.15 seconds respectively, the average value is 0.14 seconds, and the standard deviation is about 0.0082 seconds. The stability coefficient is 0.0082 / 0.14≈0.058. If the coefficient is less than 0.1, it is determined to be a stable segment, otherwise it is an unstable segment. The stability judgment threshold of 0.1 is derived from the fact that the standard deviation of the rhythm period in the field test data is concentrated between 0.005-0.012. According to the above calculation of the stability coefficient value, the continuity state of all segments is judged. The judgment basis is whether the interval between the end time of the current segment and the start time of the next segment is less than 0.05 seconds and the stability states before and after are the same. If it is satisfied, it is classified as continuous state, otherwise it is disconnected. Finally, the characteristic index of each disturbance phase fluctuation segment is constructed, and the phase fluctuation characteristic index group including duration, fluctuation frequency, rhythm period, stability coefficient and continuity state is formed.

[0074] S203: According to the phase fluctuation characteristic index group, the stability difference value between segments is calculated, the same type of segments are classified according to the trend change direction, the structure mapping relationship is established, and the fluctuation structure segment group is generated.

[0075] According to the stage fluctuation characteristic index group obtained in the foregoing, the stability coefficients between all segments are calculated for difference values two by two, the difference value is calculated in the following manner: the stability coefficient of the latter segment is subtracted from the stability coefficient of the former segment to take an absolute value, for example, the stability coefficient of segment A is 0.06, and the stability coefficient of segment B is 0.13, then the difference value is 0.07, a stability difference judgment threshold is further set, for example, 0.08 is used as a boundary for distinction, if the difference value is less than the threshold, the segments are judged as similar segments, otherwise, the segments are different segments, the threshold is set according to the tolerance of stability change, usually, the difference between adjacent segments does not exceed 0.06 under stable operation, therefore, 0.08 is set as an upper limit state, the stability difference values between all segments are obtained through the foregoing process, and a difference matrix is formed, similar segments in the difference matrix are merged, and whether the trend change directions are consistent is judged, the judgment basis is whether the change direction of the rhythm period sequence is kept increasing, decreasing or approximately constant, for example, the rhythm period of segment 1 is 0.13 seconds, the rhythm period of segment 2 is 0.14 seconds, and the rhythm period of segment 3 is 0.16 seconds, then it can be judged that the trend is increasing, segments with the same stability level and consistent trend direction are classified as similar feature segments, a structure mapping relationship is established according to the classification result, the connection relationship between similar segments and sequence characteristics are recorded in a mapping matrix, each unit in the matrix represents the corresponding relationship between the segment number and the class number to which the segment belongs, for example, segment 3 is mapped to structure class 2, and segment 4 is mapped to structure class 2, and finally, a fluctuation structure segment group under similar mapping structure is output.

[0076] Please refer to Figure 4 , the specific steps of S3 are as follows:

[0077] S301: Call the fluctuation structure segment group and the contour mutation marker sequence, and establish a match between each structure segment and the mutation point according to the sampling time to generate a structure mutation match pair sequence by judging the time sequence of the start point of each structure segment and the mutation point and screening out segments with consistent time arrangement.

[0078] First, read the start time and end time of each structure segment in the structure section group, for example, structure segment A starts at 2.305 seconds and ends at 2.605 seconds, while extracting all sampling point time indexes marked as mutations from the mutation marker sequence, for example, the time of mutation point P is 2.310 seconds, compare the mutation point time with the structure segment start time one by one, find the mutation point in the mutation point sequence that is most adjacent to the time of each structure segment, extract the time difference between the mutation point and the structure segment and record it, if the absolute value of the time difference is less than 0.02 seconds and the mutation point time is not later than the start time of the structure segment, it is considered as a matching pair with consistent time arrangement, for example, the mutation point time is 2.302 seconds and the structure segment start time is 2.305 seconds, the time difference between the two is 0.003 seconds, which meets the time matching condition, and is recorded as a matching pair (structure segment A, mutation point P), continue to traverse all structure segments and mutation points, and perform the above time difference judgment operation, exclude those mutation points that are later than the start time of the structure segment or the time difference is greater than the matching threshold, for example, the start time of structure segment B is 2.420 seconds, and the corresponding mutation point time is 2.430 seconds, which does not meet the time sequence requirement and is not included in the matching, the setting of the matching threshold is based on the actual photovoltaic response delay characteristics, usually the instantaneous disturbance response lag time is about 10ms to 20ms, therefore, the time difference tolerance is set to 20ms, finally, all matching pairs that meet the time sequence and reasonable time interval are collected to form a structure mutation matching pair sequence.

[0079] S302: According to the structure mutation matching pair sequence, compare the direction vectors of the fluctuations before and after the structure segment and the mutation point, judge whether the trend direction is consistent, and mark the combinations with consistent trend to obtain a trend consistent combination sequence;

[0080] According to the above structure mutation matching pair sequence, the starting and ending current values in the structure section are extracted to form a fluctuation direction vector. For example, the structure section A has a current value of 1.8 A at the starting point of 2.305 seconds and a current value of 2.9 A at the ending point of 2.605 seconds, and the direction vector is positive rising. The trend direction of the fluctuation section near the mutation point is extracted. The method is to take 20 sampling points (i.e. 2 ms) before and after the mutation point P, respectively, and calculate the difference between the starting and ending current values. For example, the previous section is 1.75 A, and the latter section is 2.10 A. The mutation direction is rising. If the structure section fluctuation direction and the mutation point direction are consistent, that is, both are rising or both are falling, it is marked as consistent trend. If the structure section is a downward trend and the mutation point is an upward direction, it is marked as inconsistent trend. All matching pairs perform this direction judgment. The judgment standard is compared by comparing the current size relationship between the starting point and the ending point. If the ending point value minus the starting point value is greater than 0.2 A, it is defined as an upward trend. If it is less than -0.2 A, it is defined as a downward trend. If the amplitude change is between ± 0.2 A, it is judged as stable or no trend. The threshold is set based on the minimum effective fluctuation obtained from the sampling noise and the actual level of disturbance reaction. Then the matching pairs with consistent trend are marked as 1, and the inconsistent or invalid trend is marked as 0. Finally, the trend consistent combination sequence is generated, for example [1, 0, 1, 1, 0] indicates that there are five groups of matching directions, and the first, third and fourth groups are consistent. Output the identification sequence as the result.

[0081] S303: Based on the trend consistent combination sequence, the amplitude change and duration of the structure section in the combination are extracted and compared with the protection condition threshold value to screen the response segment that meets the trigger condition and generate an action trigger section list.

[0082] Based on the trend consistent combination sequence, read all the structural segments marked as 1, extract the amplitude change and duration respectively, the amplitude change is the terminal current value minus the starting current value of the structural segment, for example, the starting current of a certain structural segment is 2.1A, and the terminal current is 3.5A, then the amplitude change is 1.4A, the duration is the terminal time minus the starting time, if the starting time is 2.400 seconds and the terminal time is 2.650 seconds, then the duration is 0.25 seconds, then compare the two values with the preset protection condition threshold value, the amplitude threshold value is recommended to be set to 1.2A, and the duration threshold value is set to 0.2 seconds, if the amplitude change ≥1.2A and the duration ≥0.2 seconds, it is determined that the structural segment meets the action trigger condition, and its number is included in the action trigger list, the setting of the protection threshold value refers to the short-time fluctuation amplitude range in the normal working state, which is usually between 0.5A and 1.0A, therefore the amplitude threshold value is set slightly higher than the upper limit level, and the duration is set to be not less than 200ms according to the protection action response time, finally the amplitude and time double condition judgment is carried out on the structural segments with consistent trend in turn, and the numbers of all structural segments meeting the trigger condition are recorded, for example, the structural segment numbers 7, 9 and 12 correspond to amplitudes 1.5A, 1.3A and 1.7A respectively, and the duration is more than 0.25 seconds, then the numbers constitute the action trigger section list.

[0083] Please refer to Figure 5 , the specific steps of S4 are:

[0084] S401: Call the action trigger section list, locate the response segment starting position, trace back the current of the previous change segment, judge whether it is consistent with the trend of the current segment, if it is consistent, extend the response segment starting point forward, and generate a trend extension starting point set;

[0085] The calling action trigger section list is taken as input, and the starting sample time of each structure section in the list is extracted, for example, the starting time of structure section A is 3.120 seconds. First, the index position of the time point in the original sample sequence is located, and then the previous identified change section is searched from the position. In the change section set, the latest section with a termination time earlier than 3.120 seconds and a time difference with the current structure section less than 0.3 seconds is searched as the previous change section. The end current value and the starting current value of the current structure section are extracted, and it is judged whether the direction change is consistent. If the starting current of the current section is 2.1A and the end current is 3.0A, it is an upward trend, and the end current of the previous section is 1.9A and the starting current is 1.1A, then the previous section is also an upward trend, and the direction is consistent. The judgment standard for consistency is that the difference between the starting current and the end current is greater than 0.5A and the direction is the same. When the direction is consistent, the starting point of the previous section is replaced with the original structure section starting point to form a new extended starting point. If the direction is not consistent or the difference is less than 0.5A, no extension is performed. The minimum amplitude threshold for direction judgment is 0.5A, which is the distinguishable range of real trend identification under noise. The tracing and judging process is repeated for all structure sections. The starting time of the structure section successfully extended forward is recorded as the extended starting point, and the trend extension starting point set is formed. For example, the original starting point of structure section A is 3.120 seconds, and the extended starting point is 3.010 seconds. The complete trend extension starting point set is finally output.

[0086] S402: According to the trend extension starting point set, the sample time of the extended response section is extracted, sorted by starting time, and the time sequence is judged whether it is dislocated and the order is unified to obtain the response section time sequence table;

[0087] According to the trend extension starting point set, the sampling time corresponding to each extension starting point is extracted, for example, the extension starting points are 2.980 seconds, 3.010 seconds, 3.005 seconds, and 2.990 seconds, and these sampling times are arranged in ascending order in turn. The sorting operation is completed by performing ascending arrangement on the starting point time. The time sequence after sorting is 2.980 seconds, 2.990 seconds, 3.005 seconds, and 3.010 seconds. Then, it is judged whether there is a dislocation between each time point. The judgment standard is whether the time difference between the current time and the original structural segment starting time exceeds 0.5 seconds. If there is a situation that the extension starting point time is earlier than the ending time of another structural segment, it is marked as sequence disorder. For example, the original structural segment B ending time is 3.000 seconds, and the extension starting point time is 2.980 seconds. It is considered that the extension point is too early to cause the sequence disorder between segments. The time difference of all adjacent segments is compared. If the time sequence of a pair is that the extension starting point B is 3.010 seconds and the extension starting point A is 3.005 seconds, the sorting sequence should be adjusted to arrange 3.005 seconds before 3.010 seconds. After uniform sorting, a time sequence table without dislocation is formed. The table records the extension starting point and the structural segment number sequence to which it belongs in chronological order, for example, [{segment number 3, starting point 2.980 seconds}, {segment number 1, starting point 2.990 seconds}, {segment number 4, starting point 3.005 seconds}, {segment number 2, starting point 3.010 seconds}]. Finally, the response segment time sequence table is obtained.

[0088] S403: Based on the response segment time sequence table, the trend direction, duration, and amplitude change are extracted, the trend continuation score value is calculated, the paragraph priority is adjusted according to the score, and the action starting position list is generated.

[0089] Based on the response time sequence table, the trend direction, duration and amplitude change of each paragraph are read in turn. The trend direction is determined by the relationship between the start and end current values in the paragraph, for example, the start point is 2.0A and the end point is 3.2A, which is an upward direction. The duration is the end time minus the start time, for example, 3.150 seconds-2.980 seconds=0.170 seconds. The amplitude change is the end current minus the start current, that is, 3.2A-2.0A=1.2A. Then the trend continuation score value is calculated. The score value is set as the sum of the trend consistency weight, the amplitude weight, and the duration weight. If the trend consistency is consistent with the previous paragraph, it is recorded as 1 point. The amplitude weight is converted in proportion. The amplitude is counted as 1 point for every 1.0A, and less than 1.0A is counted in proportion. For example, the amplitude is 0.8A, which is counted as 0.8 points. The duration is counted as 1 point for every 0.2 seconds, otherwise it is counted in proportion. For example, the duration is 0.17 seconds, which is counted as 0.85 points. If a structure segment has consistent trend, amplitude of 1.2A and duration of 0.25 seconds, the score is 1+1.2+1=3.2 points. After calculating the score value of all segments, the paragraphs are sorted in descending order of score to form a priority sequence. For example, the scores are 3.2, 2.7, 2.5, and 2.0, and the corresponding paragraph numbers are A, B, C, and D. The final output of the sorted action start position list is [A, B, C, D].

[0090] Please refer to Figure 6 The specific steps of S5 are as follows:

[0091] S501: Call the action start position list, extract the start order and trend continuity parameters of the response segment, judge the trend direction and fluctuation stability of the start position of each segment, calculate the trend duration and amplitude change amplitude, establish the corresponding stability score matrix, and generate the response segment stability score group;

[0092] The call action starts the position list as the input source, reads the starting order number of each response segment in the list and its corresponding trend continuity parameter, for example, the paragraph starting time of the segment numbered 1 is 3.010 seconds, the trend direction is upward, the starting current is 1.9A, and the ending current is 3.0A, extracts the current change direction corresponding to the starting position of the response segment, judges it as an upward trend through the comparison of the starting and ending current values, if the direction change is greater than 0.8A, it is determined as a strong trend, if it is between 0.5A and 0.8A, it is a medium trend, and less than 0.5A is a weak trend, which is obtained according to the experience setting of the current disturbance threshold and combined with the field fluctuation data, then the stability of each fluctuation segment is judged, the fluctuation amplitude change and the number of local extreme values in the sampling current sequence are extracted, if the number of extreme points in the segment is less than 5 and the amplitude change is within ±0.2A, it is considered to be stable, otherwise it is considered to be unstable, the trend strength and stability judgment results are combined, the trend duration of each segment is calculated, for example, the starting time is 3.010 seconds, the ending time is 3.250 seconds, and the duration is 0.24 seconds, the amplitude change value is calculated, which is the ending current minus the starting current, which is 1.1A, according to the trend strength score (strong trend = 1, medium trend = 0.7, weak trend = 0.4) and stability score (stable = 1, unstable = 0.5), the four-dimensional score matrix is formed by multiplying the duration (unit: second) and the amplitude change value (unit: ampere) respectively, for example, segment 1 is strong trend + stable, the duration is 0.24 seconds, and the amplitude is 1.1A, the score is [1×0.24, 1×1.1, 0.24, 1.1] = [0.24, 1.1, 0.24, 1.1], all response segment scores form a score matrix, each row corresponds to a response segment, and each column corresponds to a trend score item, a stability score item, a duration, and an amplitude, and finally the matrix is output as a response segment stability score group.

[0093] S502: According to the response segment stability score group, the starting and ending point index difference between adjacent paragraphs is extracted according to the time connection relationship between the action segments, the continuity of the connection state is judged, and the response order is rearranged according to the continuity priority to obtain a response segment priority list.

[0094] According to the scoring results of each response segment in the response segment stability score group, combined with the time connection relationship between the action segments, first read the response segment time sequence and obtain the start and end sample indexes of each segment, for example, the start index of segment A is 30100, the end index is 30500, the start index of segment B is 30505, and the end index is 30900. Calculate the index difference between the start and end points between adjacent segments. If the index difference is less than 10 sampling points (corresponding to less than 1 ms in time under 10 kHz sampling), it is considered to be time continuous, and if it is greater than 10, it is discontinuous. Continuous state is recorded as 1, and discontinuous is recorded as 0. Compare all segments two by two to obtain a connection state list, for example, [1, 1, 0, 1] indicates that there is discontinuity between the 2nd and 3rd segments. Adjust the priority of each segment according to whether it is in a continuous segment. If the segment is in a continuous region, and the sum of the stability score and the trend score in the front and back score matrix is higher than 1.5 (i.e. the combined score is strong), the response order priority is improved. For example, segment A originally ranked 3rd, after meeting the continuity and score requirements, it is promoted to 1st. Rearrange the order of all response segments, with high priority first, to generate a new response segment priority list. The list records the segment number, its corresponding start time, priority number and connection state, for example, [{segment 1, 3.010s, priority 1, continuous 1}, {segment 2, 3.250s, priority 2, continuous 1}, {segment 3, 3.600s, priority 3, continuous 0}].

[0095] S503: Based on the response segment priority list, integrate the action rhythm change period and the response continuation time, match the trigger segment position and the action rhythm structure, form a time sequence output set with trigger identification, and generate a residual current protection scheme for the power distribution network;

[0096] Based on the response segment priority list, the action rhythm change period and the response duration time of each segment are extracted, the rhythm period is calculated as the difference between the start times of adjacent response segments, for example, the start time of segment 1 is 3.010 seconds, the start time of segment 2 is 3.250 seconds, the period is 0.240 seconds, and the period from segment 2 to segment 3 is 0.350 seconds, the response duration time is the difference between the end time and the start time of the current segment, for example, segment 1 is 3.250-3.010=0.240 seconds, the rhythm period and the duration time of each paragraph are recorded, and the action start position and the rhythm information are compared, if the rhythm period changes less than 0.1 second and the duration time is more than 0.2 second, it is determined that the paragraph structure meets the action rhythm rule, the position is taken as the action trigger effective position, if the period of a certain segment changes more than 0.3 seconds or the duration time is less than 0.1 seconds, it does not meet the rhythm matching condition, the segment numbers of the segments meeting the condition are assigned with trigger identifier 1, and the segments not meeting the condition are 0, finally, the trigger identifier, the start time, the rhythm period and the duration time are integrated to form a time sequence output set, for example, [{segment 1, trigger 1, start 3.010s, period 0.240s, duration 0.240s}, {segment 2, trigger 1, start 3.250s, period 0.350s, duration 0.220s}, {segment 3, trigger 0, start 3.600s, period 0.350s, duration 0.100s}], finally, the set is output as the residual current protection scheme of the distribution network.

[0097] Please refer to Figure 7 , a residual current protection system for a distribution network based on a distributed photovoltaic power supply, comprising:

[0098] The contour marker extraction module is used to realize S1: extracting the zero sequence current waveform in the disturbance period of the distributed photovoltaic access point, marking the start segment, the middle segment and the end segment of the change, identifying the evolution mode according to the change trend, the inflection point conversion and the rhythm difference, and generating a contour mutation marker sequence;

[0099] The fluctuation structure classification module is used to realize S2: identifying the fluctuation form of the disturbance response based on the contour mutation marker sequence, analyzing the rhythm, the duration and the trend in the initial period, the middle period and the recovery period, constructing the response evolution structure, and classifying the response evolution structure into a fluctuation structure segment group;

[0100] The response segment screening module is used to realize S3: combining the fluctuation structure segment group and the contour mutation marker sequence, establishing time sequence association pair by pair, judging the consistency of the sequence and the trend, analyzing the relationship of the response combination, screening the response segment triggering the protection condition threshold, and generating an action trigger segment list;

[0101] The start priority adjustment module is used to realize S4: based on the action trigger segment list, locating the response segment start point, tracing the trend of the previous segment, if the trend is consistent, moving the start point forward, rearranging the response segment sequence, adjusting the start priority, and generating an action start position list;

[0102] The trigger rhythm merging module is used to realize S5: judging response section stability, sequencing action response priority, structuring integrated execution rhythm, and generating a residual current protection scheme of the power distribution network based on the action start position list.

[0103] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A residual current protection method for a power distribution network based on distributed photovoltaic power sources, characterized in that, The method comprises the following steps: S1: extracting the zero sequence current waveform in the disturbance period of the distributed photovoltaic access point, calibrating the starting section, middle section and ending section of the change, identifying the evolution mode according to the change trend, inflection point transition and rhythm difference of the three sections, and generating a contour mutation marker sequence; S2: based on the contour mutation marker sequence, identifying the fluctuation mode of the disturbance response, analyzing the rhythm, persistence and trend of the initial stage, middle stage and recovery stage, constructing the response evolution structure, and classifying it into a fluctuation structure section group; S3: combining the fluctuation structure section group and the contour mutation marker sequence, establishing time sequence association pair by pair, judging the consistency of the trend and the trend, combing the relationship of the response combination, screening the response segment of the trigger protection condition threshold, and generating an action trigger section list; S4: based on the action trigger section list, positioning the response segment starting point, tracing the trend of the previous section, if consistent, moving the starting point forward, rearranging the response segment order, and adjusting the starting priority, and generating an action starting position list; S5: based on the action starting position list, judging the stability of the response segment, sorting the action response priority, structuring the execution rhythm, and generating a distribution network residual current protection scheme.

2. The method for residual current protection of a power distribution network based on distributed photovoltaic power sources according to claim 1, characterized in that, The contour mutation marker sequence includes the starting change node, the middle fluctuation feature point and the ending trend node, the fluctuation structure section group includes the disturbance form partition, the curve trend segment and the stage fluctuation feature, the action trigger section list includes the trigger starting position, the trend consistency segment and the response cooperative combination, the action starting position list includes the starting order information, the trend continuation index and the response segment adjustment relationship, and the distribution network residual current protection scheme includes the response priority level, the action rhythm structure and the relay output rule.

3. The method of residual current protection for a power distribution network based on distributed photovoltaic power sources according to claim 1, characterized in that, The definition of the protection condition threshold refers to when the characteristic change of the zero sequence current waveform in the disturbance response reaches the minimum judgment standard required for triggering the protection action.

4. The method of residual current protection for a power distribution network based on distributed photovoltaic power sources according to claim 1, characterized in that, The definition of tracing the trend of the previous section refers to the process of moving the response starting point forward after the action response segment starting point.

5. The method of residual current protection for a power distribution network based on distributed photovoltaic power sources according to claim 1, characterized in that, The specific steps of S1 are: S101: obtaining the zero sequence current waveform in the disturbance period of the distributed photovoltaic power supply access point, extracting the change amplitude, slope value and first-order difference value in each period, constructing a difference index set based on the three parameters, judging the starting and ending positions of the segment whose change rate exceeds the zero sequence current disturbance threshold in the waveform, and generating a current change interval boundary pair; S102: calling the current change interval boundary pair, calculating the first and second derivatives of the current waveform in the interval, determining the trend inflection point according to the derivative sign and extreme value position, numbering the fluctuation starting point, inflection point and termination point in the sampling order, and generating a current fluctuation feature point sequence; S103: based on the current fluctuation feature point sequence, identifying the arrangement direction of the wave peak and wave trough and the rhythm proportion of the adjacent section, extracting the time index and amplitude change of the trend mutation point, constructing a segment connection relationship matrix, and generating a contour mutation marker sequence.

6. The method of residual current protection for a power distribution network based on distributed photovoltaic power sources according to claim 1, characterized in that, The specific steps of S2 are: S201: Call the profile mutation marker sequence, detect the segment of the fluctuation amplitude exceeding the disturbance response identification threshold in the zero sequence current, extract the initial, middle and recovery period segment set according to the continuous time and amplitude change, and obtain the disturbance stage fluctuation segment set; S202: Based on the disturbance stage fluctuation segment set, the duration, fluctuation frequency and rhythm period of the stage segment are extracted, the stability coefficient is calculated, and the continuity state is judged to obtain the stage fluctuation characteristic index group; S203: According to the stage fluctuation characteristic index group, the stability difference value between segments is calculated, the characteristic similar segments are classified according to the trend change direction, the structure mapping relationship is established, and the fluctuation structure section group is generated.

7. The method of residual current protection for a power distribution network based on distributed photovoltaic power sources according to claim 1, characterized in that, The specific steps of S3 are: S301: Call the fluctuation structure section group and the profile mutation marker sequence, and establish a match between the structure segment and the mutation point according to the sampling time, judge the time sequence of the starting point of each structure segment and the mutation point, screen out the time sequence consistent segments, and generate a structure mutation matching pair sequence; S302: According to the structure mutation matching pair sequence, compare the direction vectors of the fluctuations before and after the structure segment and the mutation point, judge whether the trend direction is consistent, and mark the combination with consistent trend to obtain a trend consistent combination sequence; S303: Based on the trend consistent combination sequence, the amplitude change and duration of the structure segment in the combination are extracted, and compared with the protection condition threshold to screen the response segment that meets the trigger condition, and generate an action trigger section list.

8. The method of residual current protection for a power distribution network based on distributed photovoltaic power sources according to claim 1, characterized in that, The specific steps of S4 are: S401: Call the action trigger section list, locate the response segment starting point position, trace back the current segment current direction, judge whether it is consistent with the current segment trend, if consistent, extend the response segment starting point, generate a trend extension starting point set; S402: According to the trend extension starting point set, extract the sampling time of the response segment after extension, sort according to the starting point time, judge whether the time sequence is dislocated, and unify the sequence to obtain a response segment time sequence table; S403: Based on the response segment time sequence table, extract the trend direction, duration and amplitude change, calculate the trend continuation score value, adjust the response segment priority according to the score, and generate an action start position list.

9. The method of residual current protection for a power distribution network based on distributed photovoltaic power sources according to claim 1, characterized in that, The specific steps of S5 are: S501: Call the action start position list, extract the start sequence and trend continuity parameters of the response segment, judge the trend direction and fluctuation stability of each starting position, calculate the trend duration and amplitude change amplitude, establish a corresponding stability score matrix, and generate a response segment stability score group; S502: According to the response segment stability score group, combined with the time connection relationship between the action segments, extract the starting and ending point index difference value between adjacent paragraphs, judge whether the connection state is continuous, and rearrange the response order according to the continuity priority to obtain a response segment priority list; S503: Based on the response segment priority list, integrate the action rhythm change period and the response continuation time, match the trigger segment position and the action rhythm structure, form a time sequence output set with trigger identifier, and generate a residual current protection scheme for the power distribution network.

10. A residual current protection system for a power distribution network based on distributed photovoltaic power sources, characterized in that, The system is used for implementing the distributed photovoltaic power supply based power distribution network residual current protection method according to any one of claims 1-9, and the system comprises: The profile marker extraction module is used for implementing S1: extracting a zero sequence current waveform in a disturbance period of a distributed photovoltaic access point, calibrating a starting section, an intermediate section and an ending section of variation, identifying an evolution mode according to three variation trend, inflection point conversion and rhythm difference, and generating a profile mutation marker sequence; The fluctuation structure classification module is used for implementing S2: identifying a fluctuation form of a disturbance response based on the profile mutation marker sequence, analyzing rhythm, persistence and trend in an initial stage, a middle stage and a back stable stage, constructing a response evolution structure, and classifying into a fluctuation structure section group; The response segment screening module is used for implementing S3: combining the fluctuation structure section group and the profile mutation marker sequence, establishing a time sequence association pair by pair, judging consistency of sequence and trend, combing a relationship of a response combination, screening a response segment triggering a protection condition threshold, and generating an action trigger section list; The start priority adjustment module is used for implementing S4: positioning a response section starting point based on the action trigger section list, tracing a previous section trend, moving the starting point forward if the previous section trend is consistent, rearranging a response section sequence, adjusting a start priority, and generating an action start position list; The trigger rhythm merging module is used for implementing S5: judging a response section stability based on the action start position list, sorting an action response priority, structurally integrating an execution rhythm, and generating a power distribution network residual current protection scheme.

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