A method and system for monitoring the insulation of DC charging piles

Abstract

This invention relates to the field of power electronics technology, specifically to a method and system for monitoring the insulation of DC charging piles. The method includes the following steps: real-time monitoring of branch voltage deviation from the busbar; adjusting measurement compensation parameters; correcting the measured value of branch insulation resistance; identifying leakage current drift; locating the leakage branch and triggering relay control; sending alarm information; and generating a charging pile monitoring record. In this invention, the consistency of branch voltage measurement is improved by combining branch voltage deviation trends with voltage compensation parameters. Observational errors are corrected by comparing insulation resistance fluctuations, optimizing measurement accuracy. Current deviation compensation under no-load conditions eliminates sensor zero-point drift interference. Leakage branch identification is achieved by combining current jump amplitude and voltage direction, enhancing location accuracy. Relay control and event information linkage are used to form a closed loop between alarm response and equipment status recording, improving the real-time performance and completeness of system monitoring.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, in particular to a DC charging pile insulation monitoring method and system. BACKGROUND

[0002] The field of power electronics includes electric energy conversion, electric energy control, electrical equipment operation safety, and other aspects, and is one of the core branches of modern electrical engineering and automation systems. The field mainly focuses on efficient transmission, conversion, monitoring and protection of electric energy, and is widely used in electric vehicle charging facilities, photovoltaic power generation systems, energy storage systems, rail transit, and industrial automation scenarios. In a DC power supply system, under the DC floating ground structure, continuous monitoring of the ground insulation performance of the system is an important part of ensuring personal safety and stable operation of the system. The insulation monitoring branch of power electronics focuses on solving problems such as formation of ground leakage path during equipment operation, electrical fault early warning, and monitoring communication linkage. The core technologies include electric bridge measurement, voltage sampling, leakage current sensing, adaptive capacitance compensation, and data remote communication modules, and realize real-time data interaction and remote control through industrial protocols such as RS485.

[0003] Among them, a DC charging pile insulation monitoring method refers to a monitoring method for monitoring the insulation resistance of the DC bus and related branches of the DC charging pile in real time and providing alarm and remote control functions. The specific technical matters include real-time measurement and identification of the insulation resistance of the DC bus and each branch of the charging pile. The method uses a non-balanced bridge circuit or a balanced bridge circuit, and through periodic switching of the bridge resistance inside the module and control of the grounding switch, it realizes sampling of current and voltage signals through a leakage current sensor or a shunt, and triggers a relay output to realize alarm by setting an alarm threshold. Remote start and stop control and remote monitoring parameter setting are realized through a communication interface.

[0004] The traditional DC charging pile insulation monitoring technology relies on static bridge structure or single-cycle sampling in the measurement of voltage and insulation resistance, lacks a judgment mechanism based on the trend of the difference value change within the time series, and cannot dynamically identify and finely adjust the branch deviation. In the leakage current measurement link, the zero drift problem of the sensor signal in the no-load stage is not fully considered, which can easily cause misjudgment or omission. Moreover, there is a lack of branch identification mechanism for the synchronization of multiple parameters such as current and voltage, which limits the accuracy of leakage judgment. In the relay control and information reporting, only the alarm threshold triggering logic is used, and there is a lack of binding ability with specific device number and location information, making it difficult to realize device-level traceability and behavior record. In the complex working conditions of multiple branches, there are often problems such as delay in identifying leakage events or inaccurate matching of alarm information, which affects the system operation efficiency and maintenance response ability. SUMMARY

[0005] In order to solve the technical problems existing in the prior art, the embodiment of the present application provides a direct current charging pile insulation monitoring method and system. The technical solution is as follows:

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme, a direct current charging pile insulation monitoring method, comprising the following steps:

[0007] S1: Real-time monitoring of the voltage value of each branch in the direct current charging pile and the bus voltage value, analysis of the offset direction and offset amplitude of each branch in the continuous running cycle, adjustment of the measurement compensation parameter of the branch combined with the voltage change trend of the branch, acquisition of the branch voltage calibration compensation value;

[0008] S2: Calling the branch voltage calibration compensation value, real-time acquisition of the insulation resistance observation value of the branch and comparison with the set insulation resistance standard threshold, comparison of the fluctuation degree of each branch resistance value measurement value combined with the observation fluctuation degree of the branch in the execution sequence, correction of the observation value of the target branch, generation of the insulation resistance correction value;

[0009] S3: Based on the insulation resistance correction value, according to the multiple groups of leakage current channel sampling values of the charging pile in the no-load running state, extracting the drift direction and offset amplitude in the continuous static sampling of each channel, calculating the current sampling compensation parameter, and acquiring the static drift compensation value;

[0010] S4: Calling the static drift compensation value, real-time monitoring of the corrected current signal, detecting abnormal data, identifying the leakage event, identifying the leakage branch by extracting the current jump amplitude of each branch and the change direction of the voltage to ground, and acquiring the branch positioning determination result.

[0011] As a further scheme of the present application, the branch voltage calibration compensation value includes branch voltage offset amplitude, voltage change direction and measurement compensation parameter, the insulation resistance correction value includes resistance measurement deviation amplitude, resistance value fluctuation trend and comparison correction factor, the static drift compensation value includes offset channel number, offset amplitude parameter and zero current difference coefficient, and the branch positioning determination result is specifically the leakage branch number, current mutation amplitude and voltage change direction.

[0012] As a further scheme of the present application, the step of real-time monitoring of the voltage value of each branch in the direct current charging pile and the bus voltage value, analysis of the offset direction and offset amplitude of each branch in the continuous running cycle, adjustment of the measurement compensation parameter of the branch combined with the voltage change trend of the branch, and acquisition of the branch voltage calibration compensation value is specifically:

[0013] S101: Real-time monitoring of the voltage value of each branch in the direct current charging pile and the bus voltage value, comparing the voltage value of each branch with the bus voltage value, extracting the voltage offset data, and classifying and numbering the offset data sequence of each branch to obtain the branch voltage difference sequence value;

[0014] S102: Based on the branch voltage difference sequence value, analyze the offset direction and offset amplitude of each branch in the continuous operation cycle, evaluate the change of voltage offset in multiple sampling, and obtain the branch voltage offset trend data;

[0015] S103: Call the branch voltage offset trend data, adjust the measurement compensation parameter in the voltage sampling channel according to the voltage offset direction and offset amplitude of each branch, and obtain the branch voltage calibration compensation value.

[0016] As a further scheme of the application, the branch voltage calibration compensation value is called, the insulation resistance observation value of the branch is obtained in real time and compared with the set insulation resistance standard threshold, the observation fluctuation degree of each branch resistance value is compared, the observation value of the target branch is corrected, and the insulation resistance correction value is generated. The steps are specifically:

[0017] S201: Call the branch voltage calibration compensation value, obtain the insulation resistance observation value of each branch in real time, combine the preset insulation resistance standard threshold, calculate the difference between the observation value and the standard threshold of each branch, analyze the deviation of the current cycle of the branch, and obtain the insulation resistance difference data;

[0018] S202: Based on the insulation resistance difference data, collect the continuous observation value of each branch in the execution sequence, calculate the observation value fluctuation amplitude of each branch, and obtain the branch fluctuation characteristic information;

[0019] S203: Call the branch fluctuation characteristic information, compare the fluctuation degree of each branch resistance value measurement value, extract the branch with the smallest fluctuation amplitude as the correction reference set, construct the observation value correction baseline, offset correct the insulation resistance observation value of the target branch, and obtain the insulation resistance correction value.

[0020] As a further scheme of the application, the specific formula for calculating the observation value fluctuation amplitude of each branch is:

[0021]

[0022] Calculate the branch resistance observation value fluctuation strength;

[0023] Wherein, F i′ represents the resistance observation value fluctuation strength of the branch i', R i′,m′Ri'm(m') represents the insulation resistance observation value of branch i' at the m'th sampling time point, Ri'm represents the average insulation resistance observation value of branch i' in a whole cycle, i′,max Ri'm represents the maximum observation value in a cycle of branch i', i′,min Ri'm represents the minimum observation value in a cycle of branch i', n' represents the total sampling number in a cycle of branch i', i' represents the current analyzed branch number, and m' represents the sampling point number in the branch.

[0024] As a further scheme of the present application, based on the insulation resistance correction value, the drift direction and offset amplitude in continuous static sampling of each channel are extracted according to the multiple leakage current channel sampling values of the charging pile in the no-load running state, the current sampling compensation parameter is calculated, and the static drift compensation value is obtained. The specific steps are as follows:

[0025] S301: Based on the insulation resistance correction value, the continuous static current sampling values of multiple leakage current channels of the charging pile in the no-load running state are collected, the direction change and offset amplitude in each channel sampling sequence are extracted, and the leakage channel offset characteristic information is obtained.

[0026] S302: The leakage channel offset characteristic information is called, the deviation between each channel static sampling value and the preset zero current reference value is recognized, the offset channel is obtained, and the channel drift recognition result is obtained.

[0027] S303: According to the channel drift recognition result, the sampling offset of the offset channel is extracted, the current sampling compensation parameter is calculated in combination with the sampling direction change trend, and the static drift compensation value is generated.

[0028] As a further scheme of the present application, the static drift compensation value is called, the corrected current signal is monitored in real time, abnormal data is detected, a leakage event is identified, a leakage branch is identified by extracting the current jump amplitude and the change direction of the voltage to ground of each branch, and a branch positioning determination result is obtained. The specific steps are as follows:

[0029] S401: The static drift compensation value is called, the corrected current signal is monitored in real time, abnormal data is detected, the jump point signal in the current signal is extracted, and a jump signal recognition result is obtained.

[0030] The specific formula for extracting the jump point signal in the current signal is as follows:

[0031]

[0032] The jump amplitude value is calculated.

[0033] Wherein, represents the corrected jump amplitude value of the k'th point in channel j', I k′the leakage current value representing the k'th sampling point in the channel j', I k′-1 the leakage current value representing the k'th sampling point in the channel j', I avg，j′ the average value of the current values of all sampling points in the current detection period of the channel j', I max,j′ the maximum current value in the current period of the channel j', I min,j′ the minimum current value in the current period of the channel j', k' represents the k'th sampling point number in the current channel for jump identification, j' represents the number of the leakage current detection channel currently being analyzed;

[0034] S402: Based on the jump signal identification result, collect the ground voltage data in the corresponding time period of each branch, classify the voltage fluctuation direction, analyze the time matching of the voltage change direction and the jump current, and obtain the voltage direction linkage characteristic value;

[0035] S403: According to the voltage direction linkage characteristic value, according to the matching degree, identify the leakage branch, and generate a branch positioning judgment result.

[0036] As a further scheme of the present application, the method further comprises:

[0037] S5: Based on the branch positioning judgment result, according to the leakage branch number, sending a closing control command to the relay configured in the leakage branch, and monitoring the closing feedback state signal in real time, combining the time of the leakage event, the number and position of the charging pile, matching the alarm information and sending, obtaining the charging pile monitoring record;

[0038] The charging pile monitoring record specifically refers to the closing control signal, the alarm matching information, and the leakage event processing record.

[0039] As a further scheme of the present application, based on the branch positioning judgment result, according to the leakage branch number, sending a closing control command to the relay configured in the leakage branch, and monitoring the closing feedback state signal in real time, combining the time of the leakage event, the number and position of the charging pile, matching the alarm information and sending, obtaining the charging pile monitoring record, the step specifically comprises:

[0040] S501: Based on the branch positioning judgment result, according to the number of the leakage branch, positioning the target relay control unit, and sending a closing control instruction to the relay, monitoring the closing state feedback signal of the relay in real time, and obtaining the relay closing response information;

[0041] S502: Calling the relay closing response information, combining the time node of the leakage event and the branch number information, extracting the equipment number and physical installation position of the current charging pile, and constructing a leakage event information set;

[0042] S503: According to the leakage event information set, match the alarm information and send to the management personnel, and generate the charging pile monitoring record.

[0043] In another aspect, a direct current charging pile insulation monitoring system is provided, which is applied to the direct current charging pile insulation monitoring method, and the system comprises:

[0044] The voltage offset calibration module monitors the voltage value of each branch in the direct current charging pile and the bus voltage value in real time, extracts the voltage difference value between each branch and the bus, adjusts the measurement compensation parameter according to the voltage offset direction and the change amplitude of each branch in continuous sampling, and obtains the branch voltage calibration compensation value;

[0045] The insulation resistance correction module acquires the insulation resistance observation value of each branch in a period in real time based on the branch voltage calibration compensation value, compares the observation value with the set insulation resistance standard threshold, constructs a correction reference baseline in combination with the fluctuation of each branch, adjusts the offset of the observation value, and generates the insulation resistance correction value;

[0046] The leakage drift compensation module acquires the static current sampling sequence of each channel in an unloaded state based on the insulation resistance correction value, analyzes the offset amplitude and direction of the sampling data, identifies the offset channel and adjusts the compensation parameter, and obtains the static drift compensation value;

[0047] The fault branch identification module obtains the corrected real-time current data based on the static drift compensation value, extracts the jump current amplitude of each branch, synchronously obtains the change direction of the ground voltage in the jump period, identifies the leakage branch according to the linkage characteristics of the current and the voltage change, and obtains the branch positioning determination result;

[0048] The linkage control record module identifies the leakage branch number based on the branch positioning determination result, positions the relay control unit and sends a closing command, acquires the relay feedback signal state, matches the alarm content and sends in combination with the event time, the equipment number and the physical position, establishes the charging pile monitoring record.

[0049] The technical scheme provided by the embodiment of the application has at least the following beneficial effects:

[0050] By combining the branch voltage offset trend and the voltage compensation parameter, the consistency of the branch voltage measurement is improved, the measurement error is corrected by using the insulation resistance fluctuation comparison, the measurement accuracy is optimized, the current offset compensation in the unloaded state is used to eliminate the sensor zero drift interference, the leakage branch is identified by combining the current jump amplitude and the voltage direction, the positioning accuracy is enhanced, the relay control and the event information linkage mode are used to form a closed loop of the alarm response and the equipment state record, and the real-time and completeness of the system monitoring are improved. BRIEF DESCRIPTION OF DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0052] Figure 1 The workflow diagram of the present application;

[0053] Figure 2 The system flowchart of the present application. DETAILED DESCRIPTION

[0054] The technical solutions in the present application will be described below in combination with the drawings.

[0055] 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 way. 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.

[0056] 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 "corresponding" can be used interchangeably at times. It should be pointed out that when the distinction is not emphasized, the meanings expressed are consistent.

[0057] 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.

[0058] In order to make the technical problems, technical solutions and advantages to be solved by the present application more clear, the following will be described in detail in combination with the drawings and specific embodiments.

[0059] Please refer to Figure 1 The present application provides a technical solution, a DC charging pile insulation monitoring method, comprising the following steps:

[0060] S1: Real-time monitoring of the voltage value of each branch in the DC charging pile and the bus voltage value, analyzing the offset direction and offset amplitude of each branch in the continuous operation cycle, combining the voltage change trend of the branch, adjusting the measurement compensation parameters of the branch, and obtaining the branch voltage calibration compensation value;

[0061] S2: call branch voltage calibration compensation value, real-time acquisition of branch insulation resistance observation value and comparison with the set insulation resistance standard threshold, combined with the observed fluctuation degree of branch in the execution sequence, compare the fluctuation degree of each branch resistance value measurement, correct the observation value of the target branch, generate insulation resistance correction value;

[0062] S3: based on the insulation resistance correction value, according to the multiple leakage current channel sampling values of the charging pile in the no-load running state, extract the drift direction and offset amplitude in the continuous static sampling of each channel, calculate the current sampling compensation parameter, and obtain the static drift compensation value;

[0063] S4: call static drift compensation value, real-time monitoring of corrected current signal, detection of abnormal data, identification of leakage event, identification of leakage branch by extracting current jump amplitude and voltage change direction of each branch, and obtaining branch positioning determination result;

[0064] S5: based on the branch positioning determination result, according to the leakage branch number, send the closing control command of the relay configured for the leakage branch, and real-time monitor the closing feedback state signal, combined with the time of leakage event, the number and position of charging pile, match the alarm information and send, get the charging pile monitoring record;

[0065] The branch voltage calibration compensation value includes branch voltage offset amplitude, voltage change direction, measurement compensation parameter, the insulation resistance correction value includes resistance measurement deviation amplitude, resistance value fluctuation trend, comparison correction factor, the static drift compensation value includes offset channel number, offset amplitude parameter, zero current difference coefficient, the branch positioning determination result is specifically leakage branch number, current mutation amplitude, voltage change direction, and the charging pile monitoring record is specifically closing control signal, alarm matching information and leakage event processing record.

[0066] Real-time monitoring of voltage value of each branch in DC charging pile and bus voltage value, analyzing the offset direction and offset amplitude of each branch in continuous running cycle, adjusting the measurement compensation parameter of branch, and the steps of obtaining branch voltage calibration compensation value are as follows:

[0067] S101: real-time monitoring of voltage value of each branch in DC charging pile and bus voltage value, comparing voltage value of each branch with bus voltage value, extracting voltage offset data, and classifying and numbering offset data sequence of each branch, obtaining branch voltage difference sequence value;

[0068] In the voltage difference extraction submodule, first, the real-time voltage sampling signals of each branch of the direct current charging pile are compared with the bus voltage, the offset relationship of the branch relative to the bus is constructed, and the difference value is extracted in turn according to the channel number to form an ordered number sequence. The sampling period is 10 ms, and all sampling data are archived according to the time tag for identifying the voltage fluctuation change of the branch in the running period. The voltage offset calculation is based on the sampling data at the same time point, and the result after operation enters the difference buffer area and is continuously identified and numbered. The formula is:

[0069] ΔV i = V i -V b ;

[0070] Where, ΔV i is the voltage offset value of branch i, V i is the voltage sampling value of branch i at the current time, and V b is the voltage sampling value of the bus at the current time.

[0071] Set V i = 422.5V, V b = 420.0V, then substitute and calculate:

[0072] ΔV i = 422.5-420.0 = 2.5V;

[0073] The calculation result shows that the instantaneous offset value of the branch voltage relative to the bus voltage is 2.5V, and the offset value is recorded in the branch numbered CH05. The value is continuously recorded and used as the basis for subsequent offset trend judgment. If the offset value of the branch remains in the same offset direction and the value is stable in adjacent multiple periods, it is classified as an offset trend branch and enters the number sequence grouping. It forms a contrast interval with other branches and prepares for trend calculation.

[0074] S102: Based on the branch voltage difference sequence value, analyze the offset direction and offset amplitude of each branch in the continuous running period, evaluate the change of voltage offset in multiple samples, and obtain the branch voltage offset trend data;

[0075] After the offset trend analysis submodule obtains the difference sequence, it expands the trend analysis according to the sampling time sequence, judges the voltage offset direction and change amplitude, compares the current sampling value with the previous sampling value, records the extreme value and occurrence time to construct the change trajectory within the time span, and analyzes the trend by normalizing the offset amplitude and sampling duration to extract the voltage change rate as the branch voltage stability evaluation parameter. The formula is:

[0076]

[0077] wherein R i is the voltage change rate of branch i, AV max,i is the maximum offset value, AV min,i is the minimum offset value, T i is the duration of the change process.

[0078] Set AV max,i = 3.4V, AV min,i = 1.6V, T i = 0.1s, substitute and calculate:

[0079]

[0080] The calculation result shows that the voltage offset change rate of the branch is high in a short time, and the result can be used to distinguish high-frequency offset branches and stable branches in subsequent compensation judgment logic. The system marks such high change rate branches as potential unstable paths, records their trend as positive growth, and enters the offset trend list.

[0081] S103: Call branch voltage offset trend data, adjust the voltage sampling channel measurement compensation parameter according to the voltage offset direction and offset amplitude of each branch, and obtain the branch voltage calibration compensation value;

[0082] The voltage compensation parameter adjustment submodule extracts the branch change characteristics based on the offset trend data, matches the corresponding adjustment factor by comparing the change direction and the change rate interval, adjusts the parameter as the sampling channel gain or hardware compensation configuration item written into the channel configuration table, and verifies that the number of the corresponding branch of the current channel is consistent with its trend type before operation to avoid cross-branch misadjustment. The parameter adjustment is executed in the form of adjusting factor directly superimposed on the current compensation value, using the formula:

[0083] C i ' = C i + a i ;

[0084] Wherein C i ' is the adjusted branch i compensation value, C i is the original compensation value, a i is the adjustment factor, and the adjustment factor is determined by the interval of the offset trend.

[0085] Set C i = 0.015, a i = -0.01, substitute and calculate:

[0086] C i ' = 0.015 - 0.01 = 0.005;

[0087] The calculation result shows that the current branch needs to reduce the compensation coefficient to lower the voltage input offset in the positive direction offset trend, and the correction value will be directly written into the channel register. Once the operation is completed, it will immediately affect the subsequent voltage sampling value. In the continuous sampling period, verify whether the sampling value change trend converges, such as the offset direction changes or the offset rate slows down, which is considered as compensation effective, otherwise, enter the next round of parameter correction evaluation process.

[0088] The branch voltage calibration compensation value is called, the insulation resistance observation value of the branch is obtained in real time, and is compared with the set insulation resistance standard threshold. The observation fluctuation degree of each branch resistance value is compared, the observation value of the target branch is corrected, and the insulation resistance correction value is generated. The specific steps are as follows:

[0089] S201: Call branch voltage calibration compensation value, obtain insulation resistance observation value of each branch in real time, combine preset insulation resistance standard threshold, calculate difference value of observation value and standard threshold of each branch, analyze deviation of current period of branch, and get insulation resistance difference data;

[0090] The branch voltage calibration compensation value is called, the compensation factor of each branch in the current period is extracted from the compensation data table, and is applied to the branch voltage signal correction path. The compensated branch signal is input into the insulation resistance measurement module to obtain the resistance observation value in real time. During the observation value acquisition process, the insulation resistance observation period is set to 500ms, the sampling interval is 20ms, and a complete observation sequence is formed. In this process, the preset insulation resistance standard threshold is called to compare the real-time observation value of each branch. The threshold is set by the manufacturer. The set value is derived from the DC charging pile system under normal floating ground operation. The ground resistance of each branch is required to be not less than 2MΩ. The set threshold is 2.5MΩ as the lower limit reference value. The system calculates the difference value between the observation value of each branch and the standard threshold, using the following formula:

[0091] D i =R i -R s ;

[0092] Where, D i is the insulation resistance deviation value of branch i, R i is the observed insulation resistance value of branch i, and R s is the standard insulation resistance threshold. Set R i =2.1MΩ, R s =2.5MΩ, and substitute the calculation:

[0093] D i =2.1-2.5=-0.4MΩ;

[0094] The result indicates that the branch insulation resistance is lower than the threshold value 0.4MΩ, the deviation value will be used as the basis for subsequent error correction judgment, and is recorded under the branch number information in the current monitoring period, the deviation value of each branch represents lower than the standard with negative value, and higher than the standard with positive value, finally forming a deviation list in the data set, which will be transmitted to the fluctuation analysis module for change trend identification, and finally output the insulation resistance difference data.

[0095] S202: Based on the insulation resistance difference data, the continuous observation value of each branch in the execution sequence is collected, the observation value fluctuation amplitude of each branch is calculated, and the branch fluctuation characteristic information is obtained;

[0096] The specific formula for calculating the observation value fluctuation amplitude of each branch is:

[0097]

[0098] The branch resistance observation value fluctuation strength is calculated;

[0099] Wherein, F i′ represents the resistance observation value fluctuation strength of branch i', R i′,m′ represents the insulation resistance observation value of branch i' at the m'th sampling time, represents the average insulation resistance observation value of branch i' in the whole period, R i′,max represents the maximum observation value of branch i' in the period, R i′,min represents the minimum observation value of branch i' in the period, n' represents the total sampling number in the period of branch i', i' represents the branch number of the current analysis, and m' represents the sampling point number in the branch.

[0100] Formula:

[0101]

[0102] Formula details and formula calculation derivation process:

[0103] The formula is used to calculate the insulation resistance fluctuation strength value of each branch in a certain observation sequence, and the result is used to describe the stability degree of the branch resistance measurement value in the time sequence, which is used for extracting the branch fluctuation characteristic information;

[0104] Parameter meaning and setting value:

[0105] F i′ is the resistance fluctuation strength value of branch i';

[0106] n' is the total number of samples in the period, and the insulation monitoring module is set to sample once every 10ms, and the period is 200ms, so n'=20;

[0107] R i′,m′Rm′i′ is the resistance observation value of the m'th moment of the branch i', the obtained continuous observation values are set as follows: [1980, 2020, 2010, 2000, 1990, 2005, 2015, 2008, 1985, 1998, 2002, 2007, 2012, 1988, 1995, 1999, 2004, 2010, 2000, 2003], the unit is kΩ, R i′,max = 2020, R i′,min = 1980;

[0108] The mean of the sequence is,

[0109] The parameters are substituted into the formula for calculation:

[0110]

[0111] F i′ = 12.52 + 0.02002 = 12.54002;

[0112] The result 12.54002 indicates that the branch resistance observation data has moderate fluctuations in the period, and this value will be used as the basis for judging the stability of the branch resistance and for the next step of screening the corrected baseline and deviation tolerance judgment.

[0113] S203: Call the branch fluctuation characteristic information, compare the fluctuation degree of each branch resistance value measurement, extract the branch with the smallest fluctuation amplitude as the correction reference set, construct the observation value correction baseline, and correct the offset of the target branch insulation resistance observation value to obtain the insulation resistance correction value;

[0114] Call the branch fluctuation characteristic information, and the system sorts the fluctuation amplitudes of all branches, selects the first 3 branches with the smallest fluctuation amplitudes to form the correction reference set, and performs weighted average processing on the observation values of the set to construct the reference correction baseline. The current observation value of the target branch is corrected by offset correction processing, and the correction formula is as follows:

[0115] R i ' = R i + β · (R r - R i );

[0116] Wherein, R i ' is the corrected target branch resistance value, R i is the original observation value, R r is the reference baseline value, and β is the correction coefficient.

[0117] R i = 2.0 MΩ, R r= 2.4 MΩ, β = 0.5, substitute calculation:

[0118] R i = 2.0 + 0.5 · (2.4 - 2.0) = 2.0 + 0.2 = 2.2 MΩ;

[0119] This result indicates that the target branch resistance observation value is adjusted by 0.2 MΩ, and after the correction action is completed, the system records the correction value together with the original value for subsequent offset trend convergence evaluation. The correction value is also used as a reference basis for judging abnormalities and alarms in the current period. Finally, the insulation resistance correction value is obtained.

[0120] Based on the insulation resistance correction value, according to the multiple leakage current channel sampling values of the charging pile in the no-load running state, the drift direction and offset amplitude in the continuous static sampling of each channel are extracted, the current sampling compensation parameters are calculated, and the static drift compensation value is obtained. The steps are as follows:

[0121] S301: Based on the insulation resistance correction value, collect the continuous static current sampling values of multiple leakage current channels of the charging pile in the no-load running state, extract the direction change and offset amplitude in the sampling sequence of each channel, and obtain the leakage channel offset feature information;

[0122] Based on the insulation resistance correction value, when the charging pile is in the no-load running state, the static sampling channel of each channel is called, and the data of all leakage current sensors is collected continuously for multiple periods. The single-period sampling time is set to 200 ms, the period number is 10, and the sampling data corresponding to each channel is stored in an independent cache area. The cache structure is indexed by time to establish a sequence. In the extraction process, the sampling value sequence of each period is taken out from each channel, the static section current change trajectory is constructed, the change direction between the adjacent two points in the sequence is judged, each group of sampling points is subtracted and the positive and negative values are recorded. The positive value represents the positive offset direction, and the negative value represents the negative offset direction. The number of points with consistent direction is counted as the direction change trend judgment basis. At the same time, the difference between the maximum value and the minimum value in each channel sequence is taken as the offset amplitude, and the following formula is used for offset amplitude calculation:

[0123] F j = I max,j - I min,j ;

[0124] Where F j is the static offset amplitude of the jth channel, I max,j is the maximum current value in the sampling sequence of the channel, and I min,j is the minimum current value.

[0125] Set the sampling value sequence of the 5th channel to be: 0.02 A, 0.03 A, 0.025 A, 0.04 A, 0.035 A, then:

[0126] F5 = 0.04 - 0.02 = 0.02A;

[0127] The offset direction trend value and the offset amplitude value are packaged and written into the channel state cache, and the channel number is marked, and finally a multi-dimensional feature information record set containing the channel number, the offset direction trend, and the maximum amplitude value is formed, and the leakage channel offset feature information is output.

[0128] S302: Call the leakage channel offset feature information, and identify the offset channel according to the deviation between each channel static sampling value and the preset zero current reference value, to obtain a channel drift identification result;

[0129] The leakage channel offset feature information is called, and the difference between the maximum offset value in the sampling sequence of each channel and the preset zero current reference value is judged. The preset zero current reference value is derived from the static output average value of the sensor under no-load condition. The system sets the static zero point reference as 0.005A, and the channel judgment threshold is set as ±0.01A. The system calculates the difference value between the offset amplitude value of each channel and the zero point reference, and compares it with the offset judgment threshold. The following formula is used:

[0130] D j = |F j -I0|;

[0131] Wherein, D j is the offset judgment value of channel j, F j is the offset amplitude of the channel, and I0 is the preset static zero current reference value.

[0132] Assuming that the offset amplitude of channel 4 is 0.018A and the reference value is 0.005A, then:

[0133] D4 = |0.018 - 0.005| = 0.013A;

[0134] The result exceeds the offset judgment threshold 0.01A, and the system determines that channel 4 is a channel with static offset. The determination result is recorded and the channel number and determination time label are added. At the same time, all channel numbers meeting the conditions are included in the offset channel set as the input for subsequent compensation processing, and finally the channel drift identification result is obtained.

[0135] S303: According to the channel drift identification result, the sampling offset of the offset channel is extracted, the sampling direction change trend is combined, the current sampling compensation parameter is calculated, and the static drift compensation value is generated;

[0136] According to the channel drift identification result, the system extracts the sampling offset value and the corresponding sampling direction change trend of the identified offset channel, which is used as a compensation adjustment reference parameter. In the compensation parameter calculation, the direction factor sj If the channel trend is a positive offset, then s j =-1, negative offset then s j =+1, the current compensation value is calculated using the following formula:

[0137] C j =s j ·γ·F j ;

[0138] Among them, C j s is the static compensation value for channel j. j F is the direction factor, γ is the scaling factor, and its set value is 0.8. j This represents the offset magnitude.

[0139] Assuming channel CH02 has a negative offset of 0.015A, then s2 = +1. Substituting this into the calculation:

[0140] C2=1·0.8·0.015=0.012A;

[0141] After calculation, it is found that the compensation value of 0.012A should be subtracted during the sampling process. The system writes this value into the channel compensation parameter table and binds it to the current channel address and parameter effective time. It is automatically loaded in the next sampling cycle, records all compensation parameters and outputs the static drift compensation value.

[0142] The specific steps for identifying leakage branches and obtaining branch location results are as follows: This involves calling the static drift compensation value, monitoring the corrected current signal in real time, detecting abnormal data, identifying leakage events, and extracting the current jump amplitude and the direction of voltage change to ground for each branch.

[0143] S401: Call the static drift compensation value, detect abnormal data by real-time monitoring of the corrected current signal, extract the jump point signal in the current signal, and obtain the jump signal identification result.

[0144] The specific formula for extracting the transition point signal from the current signal is as follows:

[0145]

[0146] Calculate the jump amplitude value;

[0147] in, I represents the corrected jump amplitude value at the k′-th point in channel j′. k′ I represents the leakage current value at the k′-th sampling point in channel j′. k′-1 I represents the leakage current value at the (k′-1)th sampling point in channel j′, Δt represents the sampling time interval between two adjacent sampling points. avg,j′I represents the average value of all sampling point current values of channel j' in the current detection cycle, max,j′ I represents the maximum current value of channel j' in the current cycle, min,j′ I represents the minimum current value of channel j' in the current cycle, k' represents the k'th sampling point number in the current channel for jump identification, and j' represents the number of the current leakage current detection channel being analyzed;

[0148] Formula:

[0149]

[0150] Formula details and formula calculation derivation process:

[0151] The formula is used to calculate the corrected jump amplitude value, identify the mutation point in the leakage current signal and evaluate the jump strength, and the result is used to generate the jump signal identification result;

[0152] Parameter meaning and setting value:

[0153] I k′ I represents the current value of the k'th sampling point in channel j', and the sampling period is set to 1ms, and the value is 0.085A;

[0154] I k′-1 I represents the current value of the previous sampling point in channel j', and is set to 0.020A;

[0155] Δt is the time interval between adjacent sampling points, and is set to 1ms, i.e. 0.001s;

[0156] I avg,j′ I represents the average current value of channel j' after collecting 200 samples in the current 200ms window, and is set to 0.030A;

[0157] I max,j′ I represents the maximum current value of the channel in the same cycle, and is set to 0.087A;

[0158] I min,j′ I represents the minimum current value of the channel in the same cycle, and is set to 0.018A;

[0159] Substitute the parameters into the formula for calculation:

[0160]

[0161] The result 116.81 indicates that the jump strength of the current sampling point is significantly higher than the background change rate threshold, and the offset degree of the mutation value in the overall sampling window is large. This value will be used in the subsequent judgment logic to judge the jump signal strength grade and as a direct basis for generating the jump signal identification result.

[0162] S402: Based on the jump signal recognition result, the ground voltage data of each branch in the corresponding time period is collected, the voltage fluctuation direction is classified, the voltage change direction and the time matching of the jump current are analyzed, and the voltage direction linkage characteristic value is obtained;

[0163] Based on the jump signal recognition result, the system needs to construct a target time window before and after the jump event occurrence time point, generally set the expansion time before and after as ±10ms, extract the ground voltage sampling value sequence of each branch in the window, and calculate the direction change through adjacent sampling point pair comparison, if the current point voltage is higher than the previous sampling point, it is judged as positive direction, otherwise as negative direction, the consistency of the direction is counted in the continuous sequence, the number of direction reversal is ≤1, it is marked as unidirectional fluctuation, the number of direction alternating change is ≥2, it is marked as disordered fluctuation, and the time difference between the jump current event occurrence point and the voltage change occurrence point of each branch is calculated, and the linkage characteristic value is extracted by using the following formula:

[0164] L j =T v,j -T i ;

[0165] Wherein, L j is the voltage and current jump time difference of branch j, T v,j is the voltage fluctuation start time of branch j, and T i is the jump current event occurrence time.

[0166] Suppose the jump time is 1005ms, and the voltage fluctuation start time of branch CH02 is 1002ms, then:

[0167] L2=1002-1005=-3ms;

[0168] The time difference is less than the preset linkage window (±5ms), it is judged that there is a linkage relationship, all branches that meet the linkage judgment condition are written into the voltage linkage table, the directionality (positive or negative) is marked, the linkage time difference is marked, and the linkage characteristic score is normalized, and the voltage direction linkage characteristic value is finally generated.

[0169] S403: According to the voltage direction linkage characteristic value, according to the matching degree, the electric leakage branch is identified, and the branch positioning judgment result is generated;

[0170] According to the voltage direction linkage characteristic value, the system normalizes the linkage characteristic score of each branch and judges the direction consistency with the jump current direction, sets the direction consistency score as 1 point, the smaller the absolute value of the linkage time difference, the higher the score, constructs a matching degree score model, sets the total score of the matching degree as 10 points, of which the direction consistency accounts for 20%, and the time difference reverse normalization accounts for 80%, and the following calculation formula is used:

[0171]

[0172] wherein M j is the matching score of branch j, D j is the direction consistency determination value, value 1 is consistent in direction, value 0 is inconsistent in direction, L j is the voltage time difference, θ is the maximum acceptable linkage time difference, set to 10 ms.

[0173] Assuming that the direction of branch CH03 is consistent, the time difference is 4 ms, then:

[0174]

[0175] After the score of each branch is calculated, the branches are sorted, the branch with the highest score is regarded as the leakage branch corresponding to the current jump event, the result is recorded and written into the positioning judgment table with the branch number and determination time, and the branch positioning determination result is finally output.

[0176] Based on the branch positioning determination result, a closing control command is sent to the relay configured for the leakage branch according to the leakage branch number, and a closing feedback state signal is monitored in real time, combined with the time of the leakage event, the number and position of the charging pile, matching alarm information is sent, and the steps of obtaining the charging pile monitoring record are as follows:

[0177] S501: Based on the branch positioning determination result, the target relay control unit is positioned according to the number of the leakage branch, and a closing control instruction is sent to the relay, the closing state feedback signal of the relay is monitored in real time, and the relay closing response information is obtained;

[0178] Based on the branch positioning determination result, the target branch number of the current leakage is obtained, the corresponding relationship between each number and the relay control unit is extracted in the relay configuration file, the target branch number and the relay number are matched and positioned, the relay number information is called to access the control channel, the control parameters are set and the closing command is issued, the control signal sending time node is recorded, the relay response time monitoring period is set to 300 ms, the relay state feedback signal is detected through the internal state reading module whether it is switched from the open state to the closed state within the period, whether the relay completes the closing operation is judged, and the formula is used:

[0179] R j = T s -T r ;

[0180] wherein R j is the relay closing response delay, T s is the control instruction sending time, T r is the closing state feedback signal receiving time, and T s= 12.500 s, T r = 12.762 s, the set value is substituted into the calculation:

[0181] R j = 12.762-12.500 = 0.262 s;

[0182] The calculation result shows that the relay completes the closing response, and the response time delay is within the allowable range. According to the judgment result, the relay state change and closing delay time are recorded, and the relay closing response information is obtained.

[0183] S502: Call the relay closing response information, combine the time node and branch number information of the occurrence of the leakage event, extract the device number and physical installation position of the current charging pile, and construct a leakage event information set;

[0184] Call the relay closing response information, search and extract the charging pile configuration file through the branch number information, establish the binding relationship between the relay number and the corresponding branch, extract the control module number corresponding to the branch, further read the unique device number and installation positioning data of the charging pile body, according to the number address mapping table recorded during on-site installation, determine the actual geographic position coordinate information and charging pile number at the moment of the occurrence of the leakage event according to the physical position of the current branch, extract the leakage judgment timestamp recorded in the system, joint encapsulation of the above number, position information and time node data, construct a complete leakage information structure body in chronological order, the fields in the structure body include leakage branch number, relay number, closing response state, control module number, device number, physical position coordinate and judgment time value, form a leakage event information set.

[0185] S503: According to the leakage event information set, match the alarm information and send it to the management personnel, and generate the charging pile monitoring record;

[0186] According to the constructed leakage event information set, the preset matching rule set is called from the alarm strategy library. The rule set establishes a matching index table according to the branch number, device number and timestamp three parameters. The matching rule adopts field matching method. If three fields are completely matched, it is marked as alarm hit item. If the matching is successful, the alarm information content containing the current alarm level, event code, suggested treatment scheme and other contents is generated. The alarm information structure is sent to the remote alarm system management end. At the same time, the alarm content and time of this time are recorded in the local system log, and a unique alarm serial number is generated. The binding relationship between the serial number and the current leakage event information set is established. The completion state and communication result of this round of alarm are recorded. Finally, the charging pile monitoring record is obtained.

[0187] Please refer to Figure 2The application discloses a DC charging pile insulation monitoring system, and relates to the field of DC charging pile insulation monitoring.

[0188] The voltage offset calibration module monitors the voltage value of each branch in the DC charging pile and the bus voltage value in real time, extracts the voltage difference between each branch and the bus, adjusts the measurement compensation parameter according to the voltage offset direction and change amplitude of each branch in continuous sampling, and obtains the branch voltage calibration compensation value.

[0189] The insulation resistance correction module collects the insulation resistance observation value of each branch in a period based on the branch voltage calibration compensation value, compares the observation value with the set insulation resistance standard threshold, combines the fluctuation of each branch, constructs a correction reference baseline, adjusts the observation value, and generates the insulation resistance correction value.

[0190] The leakage drift compensation module collects the static current sampling sequence of each channel in an unloaded state based on the insulation resistance correction value, analyzes the offset amplitude and direction of the sampling data, identifies the offset channel and adjusts the compensation parameter, and obtains the static drift compensation value.

[0191] The fault branch identification module obtains the corrected real-time current data based on the static drift compensation value, extracts the jump current amplitude of each branch, synchronously obtains the ground voltage change direction in the jump period, identifies the leakage branch according to the linkage characteristics of the current and voltage change, and obtains the branch positioning determination result.

[0192] The linkage control recording module identifies the leakage branch number based on the branch positioning determination result, locates the relay control unit and sends a closing command, collects the relay feedback signal state, matches the alarm content in combination with the event time, device number and physical position, sends the alarm content, and establishes the charging pile monitoring record.

[0193] The above-described embodiments can be implemented in part or in whole through software, hardware (e.g., circuitry), firmware, or any combination thereof. When implemented in software, the above-described embodiments can be implemented in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When loaded and executed by a computer, the computer instructions or computer programs can generate the flow or function according to the embodiments of the present application in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable apparatus. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium, such as from one website site, computer, server, or data center to another website site, computer, server, or data center through a wired (e.g., infrared, wireless, microwave, etc.) manner. The computer-readable storage medium can be any available medium accessible by a computer or a data storage device such as a server, data center, etc. containing a set of one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium. The semiconductor medium can be a solid-state disk.

[0194] It should be understood that the term "and / or" used herein is merely an association relationship between the associated objects, which means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone, where A and B can be singular or plural. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after it, but it can also represent an "and / or" relationship, which can be understood in the context before and after it.

[0195] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one of the following" or the like means any combination of the items, including any combination of single or multiple items. For example, at least one of a, b, or c can mean a, b, c, a-b, a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0196] It should be understood that in various embodiments of the present application, the size of the sequence number of the above-described processes does not mean the order of execution, and the execution order of the processes should be determined by their functions and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0197] Those skilled in the art can clearly understand that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0198] Those skilled in the art can clearly understand that, for the convenience and brevity of the description, the specific working processes of the devices, apparatuses and units described above can refer to the corresponding processes in the foregoing method embodiments, which will not be repeated here.

[0199] In several embodiments provided by the present application, it should be understood that the disclosed devices, apparatuses and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0200] The units described as separate components can or can not be physically separated, and the components shown as units can or can not be physical units, that is, they can be located in one place, or can be distributed on multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0201] In addition, each functional unit in each embodiment of the present application can be integrated into a processing unit, or each unit can exist physically independently, or two or more units can be integrated into one unit.

[0202] If the functions are realized in the form of software function units and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application or the parts of the present application that essentially contribute to the prior art or the parts of the technical solutions can be embodied in the form of software products. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in the various embodiments of the present application. The aforementioned storage medium includes a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0203] The above is only a specific implementation 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 changes or replacements within the technical scope disclosed by the present application, which should be covered within 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 direct current charging pile insulation monitoring method, characterized in that, The method comprises: S1: real-time monitoring of the voltage value of each branch in the direct-current charging pile and the bus voltage value, analysis of the offset direction and offset amplitude of each branch in the continuous operation cycle, adjustment of the measurement compensation parameter of the branch in combination with the voltage change trend of the branch, acquisition of the branch voltage calibration compensation value; S2: calling the branch voltage calibration compensation value, real-time acquisition of the insulation resistance observation value of the branch and comparison with the set insulation resistance standard threshold, comparison of the fluctuation degree of the resistance value measurement value of each branch, correction of the observation value of the target branch, generation of the insulation resistance correction value; S3: based on the insulation resistance correction value, according to the multiple groups of leakage current channel sampling values of the charging pile in the no-load running state, extracting the drift direction and offset amplitude in the continuous static sampling of each channel, calculating the current sampling compensation parameter, and acquiring the static drift compensation value; S4: calling the static drift compensation value, real-time monitoring of the corrected current signal, detecting abnormal data, identifying a leakage event, identifying a leakage branch by extracting the current jump amplitude and the change direction of the voltage to ground of each branch, and acquiring a branch positioning determination result; The step of calling the static drift compensation value, real-time monitoring of the corrected current signal, detecting abnormal data, identifying a leakage event, identifying a leakage branch by extracting the current jump amplitude and the change direction of the voltage to ground of each branch, and acquiring a branch positioning determination result is specifically: S401: calling the static drift compensation value, detecting abnormal data by real-time monitoring of the corrected current signal, extracting the jump point signal in the current signal, and acquiring a jump signal identification result; The specific formula for extracting the jump point signal in the current signal is: ； Calculate the jump amplitude value; wherein, representing a channel in the middle of the point after the jump amplitude value is corrected, representing a channel in the middle of the leakage current value of the sampling point, representing a channel in the middle of the leakage current value of the sampling point, representing the sampling time interval between adjacent two sampling points, representing a channel average value of all sampling point current values in the current detection period, representing a channel maximum current value in the current period, representing a channel minimum current value in the current period, indicates the sampling point number for jump identification in the current channel, indicates the leakage current detection channel number currently being analyzed; S402: based on the jump signal identification result, collecting the voltage to ground data of each branch in the corresponding time period, classifying the voltage fluctuation direction, analyzing the time matching of the voltage change direction and the jump current, and obtaining a voltage direction linkage characteristic value; The linkage characteristic value is extracted using the following formula: ； wherein, is the voltage and current jump time difference for the branch is the voltage fluctuation first occurrence time for the branch is the jump current event occurrence time;​​ S403: according to the voltage direction linkage characteristic value, according to the matching degree, identifying a leakage branch, and generating a branch positioning determination result; The matching degree is obtained using the following calculation formula: ； Wherein, is the matching degree score of the branch , is the direction consistency determination value, value 1 is consistent in direction, value 0 is inconsistent in direction, is the voltage time difference, is the maximum acceptable linkage time difference, set to 10 ms.

2. The DC charging pile insulation monitoring method according to claim 1, characterized in that, The branch voltage calibration compensation value includes branch voltage offset amplitude, voltage change direction, and measurement compensation parameter, the insulation resistance correction value includes resistance measurement deviation amplitude, resistance value fluctuation trend, and comparison correction factor, the static drift compensation value includes offset channel number, offset amplitude parameter, and zero current difference coefficient, and the branch positioning determination result is specifically a leakage branch number, a current jump amplitude, and a voltage change direction. 3.The DC charging pile insulation monitoring method according to claim 1, characterized in that, The step of real-time monitoring of the voltage value of each branch in the direct-current charging pile and the bus voltage value, analysis of the offset direction and offset amplitude of each branch in the continuous operation cycle, adjustment of the measurement compensation parameter of the branch in combination with the voltage change trend of the branch, and acquisition of the branch voltage calibration compensation value is specifically: S101: Real-time monitoring of the voltage value of each branch in the direct current charging pile and the bus voltage value, comparing the voltage value of each branch with the bus voltage value, extracting the voltage offset data, and classifying and numbering the offset data sequence of each branch to obtain the branch voltage difference sequence value; S102: Based on the branch voltage difference sequence value, analyze the offset direction and offset amplitude of each branch in the continuous operation cycle, evaluate the change of voltage offset in multiple sampling, and obtain the branch voltage offset trend data; S103: Call the branch voltage offset trend data, adjust the measurement compensation parameter in the voltage sampling channel according to the voltage offset direction and offset amplitude of each branch, and obtain the branch voltage calibration compensation value.

4. The DC charging pile insulation monitoring method according to claim 3, characterized in that, Call the branch voltage calibration compensation value, compare the insulation resistance observation value of the branch with the set insulation resistance standard threshold value in real time, compare the fluctuation degree of each branch resistance value measurement value, correct the observation value of the target branch, and generate the insulation resistance correction value. The steps are specifically: S201: Call the branch voltage calibration compensation value, real-time acquisition of the insulation resistance observation value of each branch, combined with the preset insulation resistance standard threshold value, by calculating the difference between the observation value and the standard threshold value of each branch, analyzing the deviation of the current cycle of the branch, and obtaining the insulation resistance difference data; S202: Based on the insulation resistance difference data, collect the continuous observation value of each branch in the execution sequence, calculate the observation value fluctuation amplitude of each branch, and obtain the branch fluctuation characteristic information; S203: Call the branch fluctuation characteristic information, compare the fluctuation degree of each branch resistance value measurement value, extract the branch with the smallest fluctuation amplitude as the correction reference set, construct the observation value correction baseline, offset correct the insulation resistance observation value of the target branch, and obtain the insulation resistance correction value.

5. The DC charging pile insulation monitoring method according to claim 4, characterized in that, The specific formula for calculating the observation value fluctuation amplitude of each branch is: ； Calculate the branch resistance observation value fluctuation strength; in, Indicates a branch The intensity of the fluctuation in the observed resistance value, Indicates a branch In the The insulation resistance observation value at each sampling time. Indicates a branch Average insulation resistance observed over the entire cycle, Indicates a branch Maximum observation within the period, Indicates a branch Minimum observation within the period, Indicates a branch Total number of samples within the period Indicates the branch number currently being analyzed. This indicates the sampling point number within the branch. 6.The DC charging pile insulation monitoring method according to claim 4, characterized in that, Based on the insulation resistance correction value, according to the multiple leakage current channel sampling values of the charging pile in the no-load running state, extract the drift direction and offset amplitude in the continuous static sampling of each channel, calculate the current sampling compensation parameter, and obtain the static drift compensation value. The steps are specifically: S301: Based on the insulation resistance correction value, collect the continuous static current sampling values of multiple leakage current channels of the charging pile in the no-load running state, extract the direction change and offset amplitude in the sampling sequence of each channel, and obtain the leakage channel offset characteristic information; S302: Call the leakage channel offset characteristic information, according to the deviation between each channel static sampling value and the preset zero current reference value, identify the offset channel, and obtain the channel drift identification result; S303: According to the channel drift identification result, extract the sampling offset of the offset channel, combine the sampling direction change trend, calculate the current sampling compensation parameter, and generate the static drift compensation value.

7. The DC charging pile insulation monitoring method according to claim 1, characterized in that, The method further comprises: S5: based on the branch positioning determination result, according to the leakage branch number, sending a closing control command to the relay configured in the leakage branch, and monitoring the closing feedback state signal in real time, combining the time of the leakage event, the number and position of the charging pile, matching the alarm information and sending, obtaining the charging pile monitoring record; The charging pile monitoring record specifically refers to the closing control signal, alarm matching information and leakage event processing record. 8.The DC charging pile insulation monitoring method according to claim 7, characterized in that, Based on the branch positioning determination result, according to the leakage branch number, sending a closing control command to the relay configured in the leakage branch, and monitoring the closing feedback state signal in real time, combining the time of the leakage event, the number and position of the charging pile, matching the alarm information and sending, obtaining the charging pile monitoring record, the steps are specifically: S501: based on the branch positioning determination result, according to the number of the leakage branch, positioning the target relay control unit, and sending a closing control instruction to the relay, monitoring the closing state feedback signal of the relay in real time, and obtaining the relay closing response information; S502: calling the relay closing response information, combining the time node of the leakage event and the branch number information, extracting the equipment number and physical installation position of the current charging pile, and constructing the leakage event information set; S503: according to the leakage event information set, matching the alarm information and sending to the management personnel, and generating the charging pile monitoring record.

9. A direct current charging pile insulation monitoring system, characterized in that, The system is used to realize the DC charging pile insulation monitoring method of any one of claims 1-8, and the system comprises: The voltage offset calibration module monitors the voltage value of each branch in the DC charging pile and the bus voltage value in real time, extracts the voltage difference value between each branch and the bus, adjusts the measurement compensation parameter according to the voltage offset direction and change amplitude of each branch in continuous sampling, and obtains the branch voltage calibration compensation value; The insulation resistance correction module based on the branch voltage calibration compensation value, real-time acquisition of each branch cycle insulation resistance observation value, by comparing with the set insulation resistance standard threshold, combined with the fluctuation of each branch, construct the correction reference baseline, offset adjustment to the observation value, generate insulation resistance correction value; The leakage drift compensation module based on the insulation resistance correction value, acquires the static current sampling sequence of each channel in the no-load state, analyzes the offset amplitude and direction of the sampling data, identifies the offset channel and adjusts the compensation parameter, and obtains the static drift compensation value; The fault branch identification module based on the static drift compensation value, obtains the corrected real-time current data, extracts the jump current amplitude of each branch, and synchronously obtains the ground voltage change direction in the jump period, according to the linkage characteristics of current and voltage change, identifies the leakage branch, and obtains the branch positioning determination result; The linkage control record module based on the branch positioning determination result, identifies the leakage branch number, positions the relay control unit and sends a closing command, acquires the relay feedback signal state, combines the event time, equipment number, physical position, matches the alarm content and sends, and establishes the charging pile monitoring record.

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