A multi-dimensional method and system for assessing damage to DC contactors in charging piles.

Abstract

This invention provides a multi-dimensional method and system for assessing damage to DC contactors in charging piles. The method includes: a host acquiring the current current value, current temperature, and previous temperature during the charging process of the DC contactor, as well as the voltage sequence and / or current sequence during the previous disconnection process, and historical charging and disconnection data; obtaining a disconnection damage score based on the voltage transient characteristics of the voltage sequence and / or the current drop characteristics of the current sequence; obtaining the current drift degree based on the difference between the current current value and the current compensation current value; obtaining the temperature rise rate deviation of the contact resistance based on the deviation between the actual temperature rise rate and the expected temperature rise rate; the actual temperature rise rate is obtained from the current temperature and the previous temperature, and the expected temperature rise rate is obtained based on the compensation current value and a preset temperature rise model; analyzing historical charging and disconnection data to obtain cumulative operating load data; and comprehensively analyzing the above four indicators to assess the damage status of the DC contactor.

Description

Technical Field

[0001] This invention relates to the field of battery safety technology, specifically to a multi-dimensional method and system for assessing damage to DC contactors in charging piles. Background Technology

[0002] As the core actuator for controlling the on / off state of the circuit within a charging pile, the condition of the DC contactor directly affects the safety and stability of the charging process. Especially in high-voltage, high-current DC charging scenarios, the DC contactor generates a strong electric arc at the moment of disconnection, causing the contact material to burn, transfer, and oxidize. Over time, this can lead to serious malfunctions such as increased contact resistance, contact welding, and even insulation failure.

[0003] Currently, the mainstream methods for condition monitoring and damage assessment of DC contactors still rely primarily on single-threshold judgments. However, the degradation of DC contactors is the result of the coupling effects of multiple physical fields, including electricity, heat, and force. A single-dimensional assessment leads to biased results and fails to accurately reflect the true health status of the contactor. Therefore, there is an urgent need for a damage assessment method for DC contactors in charging piles that can integrate multi-dimensional data to improve the operational safety and maintenance efficiency of charging piles. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a multi-dimensional method and system for assessing damage to DC contactors in charging piles.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A multi-dimensional method for assessing damage to DC contactors in charging piles includes the following steps: The host collects the current current value, current temperature and previous temperature of the target DC contactor during the charging process, as well as the voltage sequence and / or current sequence within the preset period during the last disconnection process, and historical charging and disconnection data. A fault damage score is obtained based on voltage transient characteristics and / or current drop characteristics; wherein, voltage transient characteristics are obtained by extracting transient characteristics from the voltage sequence, and current drop characteristics are obtained by extracting drop characteristics from the current sequence. The current drift is obtained based on the difference between the current current value and the current compensation current value; wherein, the current compensation current value is obtained by the current current value and a preset current compensation coefficient; The temperature rise rate deviation of the contact resistance is obtained based on the deviation between the actual temperature rise rate and the expected temperature rise rate; wherein, the actual temperature rise rate is obtained by the current temperature and the previous temperature, and the expected temperature rise rate is obtained based on the compensation current value and the preset temperature rise model. The historical charging and disconnection data are analyzed to obtain the cumulative operating load data; The damage score, current drift, temperature rise rate deviation, and cumulative operating load data are comprehensively analyzed to assess the damage status of the DC contactor.

[0007] As one possible implementation, obtaining the fault damage score based on voltage transient characteristics and / or current drop characteristics includes the following steps: Transient features are extracted from the voltage sequence to obtain voltage transient features; wherein, the voltage transient features include at least one or more of peak voltage, voltage settling time, and voltage oscillation count; the peak voltage represents the maximum voltage value of the voltage sequence; the voltage settling time represents the time from the start of acquisition to the voltage value dropping below a first preset voltage threshold and not exceeding a second preset voltage threshold within a preset time period; the voltage oscillation count represents the number of times the voltage value in the voltage sequence crosses downward and then upward through a third preset voltage threshold; the second preset voltage threshold is greater than the first preset voltage threshold; Extracting the current decrease characteristics from the current sequence yields current decrease features; wherein, the current decrease features include at least one or more of current decrease rate, current decrease time, and current decrease stability; the current decrease rate is the ratio of the current value difference to the time difference in the current sequence, and includes at least one or more of maximum current decrease rate and average current decrease rate; the current decrease time represents the duration from the start of data acquisition to the current value dropping below a first preset current threshold and not exceeding a second preset current threshold within a preset time period; the current decrease stability represents the variance of the current values ​​in the current sequence during the current decrease process; the second preset current threshold is greater than the first preset current threshold, and the current decrease process represents the process from the start of data acquisition to the current value decreasing and fluctuating within the first preset current threshold range within a preset time period in the current sequence; An analysis is performed on one or more of the following indicators: peak voltage, voltage stabilization time, number of voltage oscillations, current drop rate, current drop time, and current drop stability, to obtain a breakage damage score. The higher the value of the peak voltage, voltage stabilization time, number of voltage oscillations, current drop rate, current drop time exceeding a preset threshold, and the higher the value of current drop stability, the higher the breakage damage score.

[0008] As one possible implementation, the current compensation current value is represented as follows:

[0009] in, Indicates the current current value. This indicates the current compensation current value. Indicates the amplitude gain coefficient. Indicates DC bias. and All are preset current compensation coefficients.

[0010] As one possible implementation, obtaining the temperature rise rate offset of the contact resistance based on the offset between the actual temperature rise rate and the expected temperature rise rate includes the following steps: Based on the difference between the current temperature and the previous temperature, and combined with the host's data acquisition frequency, the current actual temperature rise rate is obtained. Based on the current compensation current value and the preset temperature rise model, the current expected temperature rise rate is obtained; wherein the preset temperature rise model represents the relationship between the current value and the temperature rise rate. The temperature rise rate deviation of the contact resistance is obtained based on the degree to which the current actual temperature rise rate deviates from the current expected temperature rise rate.

[0011] As one possible implementation, the temperature rise rate offset is also related to the offset duration; wherein, the longer the offset duration, the greater the temperature rise rate offset; the offset indicates that the temperature rise rate offset exceeds a preset offset threshold.

[0012] As one possible implementation method, the cumulative operating load data includes at least one or more of the following: total number of operations, cumulative on / off current, high current breaking score, and full load operating time. The total number of operations represents the total number of times the DC contactor completes a physical disconnection operation. The cumulative on / off current is obtained by accumulating the product of the compensation current value and the corresponding duration during the charging process; The high current breaking score is obtained by accumulating the level scores of the breaking current value; wherein, the breaking current value is the maximum compensation current value during the breaking process, and the level score represents the score of the corresponding level of the breaking current value according to the preset level. The full-load operating time is obtained by accumulating the duration during which the compensation current value exceeds the preset full-load current threshold during the charging process.

[0013] As one possible implementation, the comprehensive analysis of the breakage damage score, the current drift, the temperature rise rate deviation, and the cumulative operating load data to assess the damage status of the DC contactor includes the following steps: The breakage damage score, the current drift, the temperature rise rate offset, and the cumulative operating load data are normalized. The normalized fault damage score, the current drift, the temperature rise rate offset, and the cumulative operating load data are input into the damage scoring model to obtain the current damage score of the DC contactor. The damage scoring model is obtained by training a pre-trained damage scoring model, which is constructed based on a gradient boosting tree model. The pre-trained damage scoring model includes at least an objective function, which is expressed as follows:

[0014] in, This represents the value of the objective function. This represents the total number of samples in the training set used to train the injury scoring pre-trained model. Indicates the first The true damage score of each sample Indicates the first The model predicts damage scores for each sample. Represents the sample weight coefficient. Indicates the focus parameter. This represents the regularization strength coefficient. This indicates the number of historical evaluations of the same DC contactor. and These represent the DC contactor at two adjacent evaluation times. and The model predicts damage scores. This represents the time interval between two adjacent evaluation moments. This represents the time decay constant.

[0015] A multi-dimensional charging pile DC contactor damage assessment system is used to implement the method described in any one of the above-mentioned methods. The system includes a data acquisition module, a breaking characteristic module, a current drift module, a temperature rise offset module, a cumulative load module, and a comprehensive analysis module. The data acquisition module is used by the host to acquire the current current value, current temperature and previous temperature of the target DC contactor during the charging process, as well as the voltage sequence and / or current sequence within a preset period during the previous disconnection process, and historical charging and disconnection data. The fault feature module is used to obtain a fault damage score based on voltage transient features and / or current drop features; wherein, the voltage transient features are obtained by extracting the transient features of the voltage sequence, and the current drop features are obtained by extracting the drop features of the current sequence; The current drift module is used to obtain the current drift degree based on the difference between the current current value and the current compensation current value; wherein, the current compensation current value is obtained by the current current value and a preset current compensation coefficient; The temperature rise offset module is used to obtain the temperature rise rate offset of the contact resistance based on the offset between the actual temperature rise rate and the expected temperature rise rate; wherein, the actual temperature rise rate is obtained by the current temperature and the previous temperature, and the expected temperature rise rate is obtained based on the compensation current value and the preset temperature rise model. The cumulative load module is used to analyze the historical charging and disconnection data to obtain cumulative operating load data; The comprehensive analysis module is used to comprehensively analyze the breakage damage score, the current drift, the temperature rise rate deviation, and the cumulative operating load data to assess the damage status of the DC contactor.

[0016] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the method described in any one of the preceding methods.

[0017] An apparatus includes a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor, when executing the computer program, implements the method described in any one of the preceding methods.

[0018] This invention, by employing the above technical solutions, achieves significant technical effects: First, by collecting voltage, current, and temperature data at the moment of disconnection, and combining voltage transient characteristics and current drop characteristics, this invention constructs a disconnection damage scoring mechanism. This mechanism can accurately quantify the instantaneous impact damage caused to the contactor by a single disconnection operation, and is particularly sensitive to early degradation characteristics such as arc intensity and contact chatter, overcoming the shortcomings of traditional methods that rely solely on the number of switching operations. Second, this invention introduces a current compensation mechanism to obtain the theoretical current value of the DC contactor, and then obtains the current drift, effectively eliminating measurement errors caused by sensor aging, temperature drift, or bandwidth limitations, ensuring the long-term stability and reliability of current data. Third, based on the comparison between the actual temperature rise rate and the expected temperature rise rate, this invention constructs a temperature rise rate deviation index, which can inversely infer the changing trend of contact resistance through thermal characteristics. When the actual temperature rise deviates significantly from the theoretical expectation, it can promptly detect hidden cumulative damage such as contact oxidation and ablation, achieving indirect monitoring of the contactor's internal health status. Furthermore, the cumulative operating load data obtained from historical data in this invention comprehensively considers multiple deterioration factors such as mechanical wear, electrolytic erosion, and thermal aging, avoiding evaluation biases caused by single indicators. Finally, by comprehensively analyzing the breakage damage score, current drift, temperature rise rate deviation, and cumulative operating load data, the damage status of the DC contactor is assessed. This invention comprehensively evaluates the damage degree of the DC contactor from four dimensions: instantaneous impact, sensor status, internal resistance changes, and long-term load. It can accurately detect and quantify those subtle cumulative damages of the DC contactor, providing a scientific basis for preventative maintenance of charging piles and significantly improving the operational safety and reliability of the charging system. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating an embodiment of the method of the present invention; Figure 2 This is an overall schematic diagram of an embodiment of the system of the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to embodiments. These embodiments are illustrative of the invention and the invention is not limited thereto. Unless otherwise specified, the features in the following embodiments can be combined with each other.

[0022] Terminology Explanation: (1) Host. The host mentioned in this invention refers to the core control unit inside the charging pile, also commonly referred to as the central control unit or host. The host is responsible for the operation management, command issuance, data acquisition and processing, and communication interaction of the entire charging pile. Generally, the host is an embedded processor that integrates a high-precision analog-to-digital converter (ADC), a digital-to-analog converter (DAC), non-volatile memory, and multiple communication interfaces. In this invention, the host undertakes the core algorithm execution function, including issuing segmentation commands, acquiring data, calculating scores, and issuing early warning information.

[0023] (2) Charging Terminal. The charging terminal in this invention refers to the specific interface unit in a charging pile that is physically connected to the electric vehicle and transmits energy; it is also commonly referred to as a charging gun or charging interface. A charging pile may be configured with multiple charging terminals to support simultaneous charging of multiple vehicles. Each charging terminal contains key components such as a DC contactor, current sensor, and temperature sensor, and is independently connected to the host's acquisition and control channels. In this invention, each charging terminal is considered an independent monitoring node, and its operating status data is collected in real time and uploaded to the host.

[0024] (3) DC contactor. The DC contactor mentioned in this invention refers to an electromagnetic switching device installed inside the charging terminal for controlling the on / off state of the DC charging circuit. The DC contactor is the core actuator of the charging pile, responsible for connecting and disconnecting the high-current DC circuit at the start and end of charging. Since DC current does not have a natural zero-crossing point, the DC contactor will generate a strong electric arc when disconnecting, causing the contact material to burn, transfer and oxidize. It is one of the components in the charging pile that is most prone to aging and failure. The damage assessment object of this invention is the DC contactor. By monitoring the voltage transient characteristics, current drop characteristics, temperature rise characteristics and cumulative operating load during its disconnection process, its health status is quantitatively assessed and trend predicted from multiple dimensions.

[0025] (4) Contact Resistance. The contact resistance described in this invention refers to the resistance value formed between the contact interfaces of a DC contactor when the main contacts are closed. Contact resistance is not a constant value, but a dynamic parameter affected by factors such as contact material, contact pressure, surface oxidation level, and arc erosion. The magnitude of the contact resistance directly determines the heat generated by the contactor during current flow and is one of the key indicators reflecting the health status of the contactor. Since it is difficult to directly measure the contact resistance between the contacts of a contactor in operation, this invention adopts an indirect evaluation method: by monitoring the rate of temperature change near the contactor contacts and comparing it with the expected rate of temperature rise calculated based on the compensation current value and a preset temperature rise model, the change in contact resistance is inferred from the degree of deviation between the two.

[0026] Example 1: In one embodiment, a multi-dimensional method for assessing damage to DC contactors in charging piles, such as... Figure 1 As shown, it includes the following steps: S100: The host collects the current current value, current temperature and previous temperature of the target DC contactor during the charging process, as well as the voltage sequence and / or current sequence within the preset period during the last disconnection process, and historical charging and disconnection data. S200: Based on voltage transient characteristics and / or current drop characteristics, a fault damage score is obtained; wherein, voltage transient characteristics are obtained by extracting transient characteristics from the voltage sequence, and current drop characteristics are obtained by extracting drop characteristics from the current sequence; S300: Based on the difference between the current current value and the current compensation current value, the current drift is obtained; wherein, the current compensation current value is obtained by the current current value and a preset current compensation coefficient; S400: Based on the offset between the actual temperature rise rate and the expected temperature rise rate, the temperature rise rate offset of the contact resistance is obtained; wherein, the actual temperature rise rate is obtained by the current temperature and the previous temperature, and the expected temperature rise rate is obtained based on the compensation current value and the preset temperature rise model. S500: Analyze the historical charging and disconnection data to obtain cumulative operating load data; S600: A comprehensive analysis is performed on the break-off damage score, the current drift, the temperature rise rate deviation, and the cumulative operating load data to assess the damage status of the DC contactor. In another embodiment, in S100, the host collects the current current value, current temperature, and previous temperature of the target DC contactor during the charging process, as well as the voltage sequence and / or current sequence within a preset period during the last disconnection process, and historical charging and disconnection data. The aging of the charging pile's DC contactor is not determined by a single factor at a single moment, but is the result of the combined effects of electrical wear, thermal stress, and mechanical stress. Data from a single moment can only reflect the current condition of the contactor, but cannot determine the severity of its internal losses.

[0027] The ADC module inside the host is directly connected to both ends of the main contacts of the DC contactor. Each DC contactor independently occupies one differential input channel of the ADC chip, which collects the voltage and current data of the DC contactor. Each DC contactor is equipped with a high-precision negative temperature coefficient (NTC) thermistor or resistance temperature detector (RTD). Its signal is acquired in real time through the host's ADC. The temperature data is the real-time temperature near the contact resistance of the DC contactor, obtained through the NTC thermistor or RTD temperature sensor. Therefore, to effectively assess the damage to the DC contactors of the charging pile, it is necessary to comprehensively consider the operating data of the charging pile during charging and disconnection processes. The host's data acquisition includes the following steps: S110: The host collects historical charging and disconnection data during the charging process of the target DC contactor.

[0028] While a single measurement may be affected by occasional factors, analyzing historical data can help determine whether a fault is sudden or gradual. This trend provides a more accurate reflection of the condition than a single measurement. For example, a contactor has a finite lifespan; each disconnection consumes a portion of its electrical lifespan. By using historical data, the electrical wear from each disconnection can be accumulated, allowing for the calculation of how much of its lifespan has already been consumed.

[0029] Historical charging and disconnection data mainly includes records of physical disconnection operations completed by the DC contactor, current values ​​during the charging process, and corresponding charging times. This historical data can be used to assess the current lifespan of the DC contactor and, consequently, its damage status. The historical charging and disconnection data is stored in the host computer, which can access it when needed.

[0030] S120: The host collects the voltage and current sequences of the DC contactor during the preset period in the previous disconnection process.

[0031] The moment of disconnection is the most vulnerable moment for the contactor; therefore, assessing the contactor's damage requires analyzing data from the disconnection process. When the host receives a maintenance command for a specific / target charging terminal, it issues a disconnection command, requiring the corresponding DC contactor to disconnect. Simultaneously with issuing the disconnection command, the host begins collecting timestamped voltage and current values ​​across the DC contactor of the target charging terminal within a preset period (e.g., 2ms), thus acquiring the voltage and current sequences.

[0032] S130: The host collects the current current value, current temperature and previous temperature of the DC contactor during the charging process of the charging pile. In other words, the assessment of damage to the DC contactor is carried out during the charging process. During the charging process, the damage status of the DC contactor is periodically assessed and updated according to the cycle set by the system.

[0033] It is well known to those skilled in the art that the data collected above are all data from the same DC contactor.

[0034] In another embodiment, in S200, a breaking damage score is obtained based on voltage transient characteristics and / or current drop characteristics, including the following steps: S210: Extract transient features from the voltage sequence to obtain voltage transient features. The host performs point-by-point analysis on the acquired voltage sequence based on timestamps to extract voltage transient features from the voltage sequence. The voltage transient features include peak voltage, voltage settling time, and number of voltage oscillations, as detailed below: (1) Peak voltage. Peak voltage is the maximum voltage value in the voltage sequence. If the peak voltage is higher than the preset threshold, it indicates that the voltage transient exceeds the limit.

[0035] (2) Voltage settling time. Voltage settling time refers to the time from the issuance of the interrupt command / the start of data acquisition. This continues until the voltage value in the voltage sequence first drops below a first preset voltage threshold (e.g., 50mV) and does not exceed a second preset voltage threshold (e.g., 55mV) within a preset time period (e.g., 10μs). The duration of this process ( If the voltage stabilization time exceeds the preset stabilization time, it indicates a slow disconnection process and potential arcing. The second preset voltage threshold is greater than the first preset voltage threshold. The second preset voltage threshold can be a certain percentage increase based on the first preset voltage threshold, such as 10%.

[0036] (3) Number of voltage oscillations. When the DC contactor disconnects and the current is cut off, a reverse electromotive force is generated due to the inductance in the circuit. This causes the voltage between the contacts of the DC contactor to rise rapidly and exceed the power supply voltage, forming a voltage spike, i.e., overshoot. This spike usually fluctuates up and down and gradually stabilizes in the form of damped oscillations. This fluctuation is an important early characteristic of contactor damage. A third preset voltage threshold (e.g., 50mV) can be set as the basis for judging whether oscillation has occurred. When the voltage value drops from above the third preset voltage threshold to below the third preset voltage threshold and then rises back above the third preset voltage threshold, it is counted as one complete oscillation. Therefore, the number of voltage oscillations refers to the number of times the voltage value in the voltage sequence after the contactor disconnects crosses the third preset voltage threshold. The more voltage oscillations, the stronger and longer the arc, and the more severe the contactor damage.

[0037] S220: Extract the current-decreasing features from the current sequence to obtain current-decreasing features, which include current-decreasing rate, current-decreasing time, and current-decreasing stability, as detailed below: (1) Current drop rate. The current drop rate is the ratio of the difference in current values ​​to the difference in timestamps in the current sequence. The current drop rate includes the maximum current drop rate and the average current drop rate. If the maximum current drop rate is greater than the preset threshold, it indicates that the current drops too quickly, which leads to the contactor breaking too quickly and thus the concentration of arc energy. If the average current drop rate deviates significantly from the statistical average of similar contactors (e.g., exceeding 30% of the average), it is also considered abnormal.

[0038] (2) Current fall time. Similar to the definition of voltage stabilization time, current fall time refers to the duration from the issuance of the interrupt command until the current value in the current sequence drops below the first preset current threshold and does not exceed the second preset current threshold within a preset time period. The second preset current threshold is greater than the first preset current threshold. If the current fall time is too low (e.g., below 50 μs), it indicates that the current fall time is too short; if the current fall time is too high (e.g., above 500 μs), it indicates that the current fall time is too long.

[0039] (3) Current drop stability. Current drop stability refers to the variance or standard deviation of the current value during the current drop process, indicating the degree of fluctuation of the current during the drop process. The current drop process refers to the process in the current sequence from the start of data acquisition until the current value drops and stabilizes within the first preset current threshold range (close to zero). If the current drop stability is greater than the preset current stability threshold, it indicates that there is obvious oscillation in the current drop process. The current oscillation may be caused by DC contactor contact jitter or arc instability.

[0040] It is important to note that the current drop characteristic is based on the collected raw current data, rather than the analysis of the compensation current value, because only in this way can the accurate current anomaly be obtained.

[0041] S230: Analyze one or more of the following indicators: peak voltage, voltage settling time, number of voltage oscillations, current drop rate, current drop time, and current drop stability, to obtain a breakage damage score.

[0042] Based on these voltage transient and current drop characteristics, the host computer assigns a damage score to this disconnection operation. The damage score is a negative score; a higher value indicates a greater anomaly in the disconnection. The disconnection damage score can be obtained by analyzing one of the following indicators: peak voltage, voltage settling time, number of voltage oscillations, current drop rate, current drop time, and current drop stability. Alternatively, multiple indicators can be analyzed to obtain the disconnection damage score. The principle is: compare the peak voltage, voltage settling time, number of voltage oscillations, current drop rate, and current drop time with corresponding preset thresholds. The greater the deviation of an indicator from the preset threshold and the greater the value of the current drop stability, the higher the disconnection damage score.

[0043] In this embodiment, based on the break-down damage scoring rule, the peak voltage, voltage stabilization time, number of voltage oscillations, current drop rate, current drop time, and current drop stability are analyzed simultaneously to obtain the break-down damage score. As shown in Table 1, this embodiment provides an example of the aforementioned damage scoring rule.

[0044] Table 1 Example of Injury Scoring Rules

[0045] The damage score employs a weighted cumulative model, quantifying each of the aforementioned abnormal features into a score, which is then summed to obtain the damage score for this segmentation operation. The damage score range is set from 0 to 100, with 0 indicating perfect segmentation and no abnormal features, and 100 indicating severe abnormal segmentation, approaching or reaching the fault threshold. The damage score is stored in real-time in the host's non-volatile memory (such as EEPROM or flash memory) to ensure that the data is not lost due to power failure.

[0046] In another embodiment, in S300, the current drift is obtained based on the difference between the current current value and the current compensation current value, including the following steps: S310: With the target DC contactor uncharged, inject a test current into the target DC contactor and collect the corresponding measured current data. Analyze the test current and measured current to obtain the current compensation coefficient. In practice, due to bandwidth limitations, temperature drift, aging, etc., the current signal measured by the current sensor will have a significant amplitude and phase shift relative to the injected ideal test current signal, and will also be superimposed with noise and DC bias. Therefore, it is necessary to identify this deviation, including the following steps: S311: Inject test current into the target DC contactor when the target DC contactor is not charged.

[0047] Every so often, when the target charging terminal is not busy or the charging current has dropped to a very low level—for example, when the current has dropped below 0.5 amps but has not completely disconnected under the flexible release resource occupancy mechanism, or when the terminal is idle—the host injects a very weak, periodically changing test current signal into the power module via a digital-to-analog converter (DAC). This signal is, for example, a sine wave signal with a peak-to-peak value of 0.1 amps and a frequency of 100 Hz. This signal is applied to the control input of the power module and is represented as follows: ,in, Indicates time The current value of the test current signal injected at that time. This indicates the peak current value of the injected current signal, typically 0.1A. This indicates the frequency of the injected current signal, for example, 100Hz. This represents the initial phase, which is usually set to zero for ease of analysis. This injected ideal current signal acts as an excitation on the power supply module, causing the actual current flowing through the current sensor to include this tiny periodic component.

[0048] S312: While injecting the test current, the host acquires the corresponding measured current data. While injecting the test current, the ADC inside the host will operate at a high frequency. (For example, 10KHz) The weak current signal is collected by the sampling current sensor to obtain a discrete time series, that is, the measured current series, which includes the current value, phase and timestamp.

[0049] S313: If the deviation of the current value or phase deviation between the current signal in the measured current sequence and the corresponding current test signal exceeds a preset threshold, the current compensation coefficient is obtained based on the measured current sequence and the test current signal. For example, when the amplitude of the measured current signal (the current value in the current sequence) deviates from the ideal amplitude (the current value of the current test signal) by more than 2%, or the phase lag exceeds 5 degrees, the host will calculate the current compensation coefficient.

[0050] Measuring current values ​​in a current sequence The relationship between the current value and the test current signal can be expressed as follows:

[0051] in, This represents the amplitude gain coefficient. The ideal value is 1 (no change in amplitude). A value greater than 1 indicates that the amplitude is amplified, and a value less than 1 indicates that the amplitude is attenuated. This represents the phase shift, with an ideal value of zero. This indicates DC bias, with an ideal value of zero. This indicates measurement noise.

[0052] The current compensation coefficient and amplitude gain coefficient can be solved using methods such as the least squares method. Phase shift and DC bias The main unit periodically inspects the DC contactors and updates the current compensation coefficient in a timely manner.

[0053] S320: Adjust the current value using the current compensation coefficient to obtain the current compensation current value.

[0054] The current compensation coefficient is calculated periodically, allowing for timely correction of the current signal. In this embodiment, the real-time current signal measurement can be decomposed into components in phase and quadrature with the ideal reference signal, and then corrected separately. However, since the waveform of the real-time current signal is unknown and not a single frequency, and in DC charging scenarios, current changes are relatively slow with the main energy concentrated in the low-frequency band, the impact of phase shift on the instantaneous value is much smaller than that of amplitude deviation. Therefore, in this embodiment, only the amplitude (current value) is compensated; the phase shift is only used as a monitoring indicator of the current sensor's health status and is not used for real-time correction. Thus, for any given moment, the original current value / current value... The compensated current value is the current compensated current value. , is represented as: .

[0055] S330: Calculate the degree to which the actual current value measured by the current sensor (current current value) deviates from the theoretical current value (current compensated current value) and limit it to between 0 and 100 to obtain the current drift degree. The current drift degree is expressed as: Current drift degree = .

[0056] In another embodiment, in S400, the temperature rise rate deviation of the contact resistance is obtained based on the deviation between the actual temperature rise rate and the expected temperature rise rate. During long-term use, the contact resistance of a DC contactor gradually increases due to arc erosion, mechanical wear, oxidation, etc. This increased contact resistance leads to a higher heat generation at the contact points when the same current flows through. As the temperature rises, the contact resistance increases. By comparing the actual rate of temperature rise with the expected rate of temperature rise, the change in contact resistance can be inferred, thus serving as one indicator for assessing damage to the DC contactor. If the actual temperature rises faster than theoretically calculated, it indicates that the contact resistance may have increased. The following steps are then included: S410: Based on the difference between the current temperature and the previous temperature, and combined with the host's data acquisition frequency, the current actual temperature rise rate is obtained. The current actual temperature rise rate is expressed as: Current actual temperature rise rate = (Current temperature - Previous temperature). Data acquisition frequency.

[0057] S420: Based on the current compensation current value and the preset temperature rise model, the current expected temperature rise rate is obtained.

[0058] For a healthy DC contactor, the temperature rise rate of the DC contactor under different currents can be obtained through a series of tests at the time of manufacture or in the early stage of operation. That is, the temperature rise curve / temperature rise model. The temperature rise curve reflects the steady-state temperature under different currents, the temperature rise rate under different currents, and the heat dissipation rate under different temperature differences. The test also includes a zero-current state, which is to record the equilibrium state between the contactor temperature and the ambient temperature.

[0059] To predict the rate of temperature rise in contact resistance, it is necessary to acquire the real-time charging compensation current and temperature of the DC contactor. The real-time charging compensation current is the compensated current value across the DC contactor during charging, collected by a current sensor. Based on this real-time charging compensation current and a pre-obtained temperature rise curve, the current expected rate of temperature rise is calculated. This expected rate of temperature rise indicates how quickly the temperature should continue to rise from the current temperature.

[0060] S430: Based on the degree to which the current actual temperature rise rate deviates from the current expected temperature rise rate, the temperature rise rate deviation of the contact resistance, i.e., the contact resistance anomaly confidence level, is obtained. The temperature rise rate deviation is expressed as: Temperature rise rate deviation = min(|(current actual temperature rise rate - current expected temperature rise rate) / current expected temperature rise rate| 100,100), where, This represents the function that takes the minimum value.

[0061] If the temperature rise rate deviation is within 5, it indicates that the contact resistance of the DC contactor is normal and there is no deviation. If the temperature rise rate deviation is greater than 5, it indicates that there is a deviation in the contact resistance. Specifically, if (current actual temperature rise rate - current expected temperature rise rate) / current expected temperature rise rate is greater than 5, it indicates that the contact resistance may increase. If (current actual temperature rise rate - current expected temperature rise rate) / current expected temperature rise rate is less than 5, it indicates that the contact resistance may decrease (this situation is relatively rare) or the heat dissipation conditions have improved.

[0062] In another embodiment, when evaluating the difference in the temperature rise rate of contact resistance, it is necessary not only to consider the magnitude of a single deviation (temperature rise rate offset greater than a preset deviation threshold), but also to pay attention to the duration of the deviation, assigning a weight to the temperature rise rate offset based on the duration. If the deviation only occurs briefly (e.g., a few seconds), it may be a momentary disturbance, and the weight is 0; if the deviation lasts for a period of time (e.g., a few minutes), it indicates that the deviation has a certain degree of credibility, but further observation is needed, and the weight can be set to around 0.4; if it lasts for a long time (e.g., more than tens of minutes), it can be basically determined that there is a problem, and the weight can be set to around 0.7; if it occurs repeatedly (multiple charging processes) and lasts for a long time, it can be confirmed that the problem has become entrenched, and the weight can be set to 1.

[0063] Finally, the temperature rise rate offset is multiplied by the weight to obtain the updated temperature rise rate offset.

[0064] In S500, the historical charging and disconnection data recorded by the host are analyzed to obtain cumulative operating load data. The degradation of a DC contactor is not only related to the severity of a single operation, but also closely related to the overall workload it bears. By accumulating and recording various operating load data of the DC contactor, the overall working pressure it bears can be quantified, providing a long-term cumulative basis for health status assessment.

[0065] In another embodiment, the cumulative operating load data includes the total number of operations, the cumulative on / off current, the high current breaking score, and the full load operating time.

[0066] (1) Total number of operations. The total number of operations represents the total number of times the DC contactor completes a physical disconnection operation. In evaluating the load of a DC contactor, the disconnection operation is the main focus, because the electric arc generated during the disconnection process is the main cause of contact wear. A complete disconnection operation refers to the DC contactor changing from the connected state to the disconnected state. Whenever the host sends a disconnection command to a DC contactor and successfully detects that the contactor has disconnected, the counter corresponding to the total number of operations for that contactor is incremented by 1. The total number of operations is the most intuitive indicator of wear. Generally speaking, contactors have a design life, such as an electrical life of 10,000 operations. When the total number of operations approaches the design life, even if the current performance is normal, it means that it has entered the end of its life.

[0067] (2) Cumulative On / Off Current. When current passes through the contacts, it generates heat and electrodynamic force, which can lead to fatigue, transfer, and wear of the contact materials over a long period. Even if the current for each operation is small, if the total amount of charge passed is large, the wear can still be considerable. The cumulative on / off current represents the total amount of charge passing through the contactor (in ampere-hours), which is the sum of the real-time current (compensation current) and time during normal charging, reflecting the total degree of electrical wear of the contactor contacts.

[0068] (3) Cumulative score for high current interruption. The interruption current value is the maximum value of the current after compensation during each interruption process. The larger the interruption current value, the greater the arc energy generated and the more severe the erosion of the contacts. For example, the damage to the contacts from a single 500A high current interruption may exceed that from 100 100A low current interruptions. Therefore, it is necessary to calculate the score for high current interruption.

[0069] The breaking current value is classified into levels based on a preset current threshold and a corresponding level score is specified. Specifically, the current value at the moment of breaking is classified. For example: 100A~300A is a light high current with a level score of 1 point; 300A~500A is a medium high current with a level score of 2 points; and above 500A is a heavy high current with a level score of 3 points.

[0070] The cumulative score for high current breaking capacity is the sum of the scores for each breaking operation. In this way, the cumulative score for high current breaking capacity can be used to determine how many times each contactor has withstood breaking under severe operating conditions.

[0071] (4) Full-load operating time. Full-load operating time refers to the cumulative duration for which a DC contactor carries a large current. The full load does not refer to the rated maximum value, but rather to the current level / full-load threshold that significantly affects contact temperature rise, such as 80% of the rated current or a fixed value (e.g., 200A). When the actual current value (compensation current value) exceeds this threshold, the contactor is considered to be in full-load operating condition. The actual current can be detected once per second. If the actual current value is greater than the full-load threshold, this second is counted as part of the full-load operating time. All seconds that meet the condition are added together to obtain the total full-load operating time. When a contactor carries a large current for a long time, the contact temperature will rise significantly, accelerating material aging and oxidation. The longer the full-load operating time, the more severe the thermal aging.

[0072] These cumulative operating load data are periodically (e.g., every 100 operations or every hour) saved to the host's non-volatile memory to prevent data loss. These past operating records reflect the overall working stress experienced by the contactor and are also an important basis for assessing its long-term wear.

[0073] In S600, the breaking damage score, current drift, temperature rise rate deviation, and cumulative operating load data are comprehensively analyzed to assess the damage status of the DC contactor. After obtaining the breaking damage score characterizing the instantaneous impact damage of the DC contactor, the current drift characterizing the sensor and measurement system status, the temperature rise rate deviation characterizing the thermal characteristics of the contact resistance, and the operating load score characterizing the long-term cumulative effect, the host computer performs efficient fusion analysis on these four indicators that characterize the contactor's damage / health status from different dimensions according to a pre-set, configurable rule set to assess the overall damage status of the contactor and trigger corresponding early warnings and handling suggestions based on the damage status.

[0074] In another embodiment, the rule set compares the breakage damage score, current drift, contact resistance anomaly confidence level, and cumulative operating load data with corresponding thresholds to comprehensively determine the contactor's damage status under different conditions. For example, different damage conditions can be defined as follows: (1) Damage condition: No wear indicates that the DC contactor is in the best condition. All indicators show that its performance is good and all performance indicators are within the optimal range. It can be used with confidence and no intervention is required.

[0075] The judgment criteria are that all of the following conditions must be met simultaneously: average damage score of the last 10 times <20, current drift <3 (i.e., very small sensor drift), contact resistance abnormality confidence <10, total number of operations <0.5 design life (i.e., the total number of operations is less than half of the design life), and number of high current interruptions <10% of the total life cycle.

[0076] (2) Damage condition: Slight wear indicates that the DC contactor has begun to show some early signs of deterioration, but the degree is very slight and does not affect normal use. However, it is recommended to increase the monitoring frequency appropriately.

[0077] The judgment criteria are any of the following: the average damage score of the most recent 10 operations is between 20 and 50, the current drift is between 3 and 8, the contact resistance anomaly confidence level is between 10 and 30, 0.5 design life < total number of operations < 0.7 design life, and the number of high current interruptions is between 10% and 30% of the total life cycle.

[0078] (3) Damage condition: Moderate wear indicates that the DC contactor has shown obvious signs of deterioration. Although it can still work, problems may occur at any time. It is recommended to include it in the maintenance plan and arrange for an inspection soon.

[0079] The judgment criteria are any of the following: the average damage score of the last 10 times is between 50 and 100, the current drift is between 8 and 15, the contact resistance anomaly confidence level is between 30 and 80, 0.7 design life < total number of operations < 0.9 design life, and the number of high current interruptions is between 30% and 80% of the total life cycle.

[0080] (4) Damage condition: Severe wear. This requires attention, indicating that the DC contactor is in a severely deteriorated state and the risk of continued use is very high. It is recommended to arrange an immediate inspection, prepare to replace the spare parts, and, if necessary, stop using the charging terminal.

[0081] The judgment criteria are any of the following: average damage score of the last 10 times > 100 points, current drift > 15, contact resistance abnormality confidence level > 80, total number of operations > 0.9 design life, and number of high current interruptions > 80% of the total life cycle.

[0082] In another embodiment, the damage score of the DC contactor can be obtained by weighted averaging of the breaking damage score, current drift, temperature rise rate deviation, and cumulative operating load data. Based on the damage score, the damage status of the DC contactor can be assessed more comprehensively and accurately, including the following steps: S610: Normalize the breaking damage score, current drift, temperature rise rate deviation, and cumulative operating load data. Since the breaking damage score, current drift, and temperature rise rate deviation are all limited to between 0 and 100, it is only necessary to normalize the cumulative operating load data (total number of operations, cumulative on / off current, high current breaking score, and full load operating time), and then take a weighted average to obtain a value between 0 and 100 to comprehensively represent the cumulative operating load level. This includes the following steps: S611: Normalize the total number of operations, cumulative on / off current, high current breaking score, and full-load running time.

[0083] (1) Total number of operations normalization Total number of operations Normalized representation: Score of total normalized operations , means as follows:

[0084] in, The rated life of a DC contactor is typically provided by the manufacturer. The mechanical life of a DC contactor generally follows a bathtub curve wear pattern. In the early stages of its life, each disconnection operation results in a small increase in wear, but towards the end of its life, each disconnection operation can lead to near-failure wear. This means the damage is non-linearly accelerated. Therefore, normalizing the total number of operations using a logarithmic function reflects this non-linear characteristic, where early operations have a smaller impact, while later operations have a larger impact.

[0085] (2) Cumulative on / off current normalization Cumulative on / off current (Unit: Ampere-hour) This mainly reflects the electro-erosion effect of the electric arc on the contacts. During the initial stage of electro-erosion, wear is rapid (burrs on the contact surface are smoothed out), the wear is gradual and stable in the middle stage, and accelerates again in the final stage when little contact material remains. This is a typical S-shaped (growth curve) process. The cumulative on / off current is then... Normalized representation: Normalized cumulative on / off power score , means as follows:

[0086] in, The midpoint of the S-curve is usually set as half of the critical erosion value or obtained from historical data. The critical erosion value is derived from experiments or historical data. This represents the kurtosis coefficient of the growth curve, which controls the transition speed from a low score to a high score. It can be calculated based on the cumulative on / off current from slight degradation to severe degradation in historical data. The value is derived by working backwards from the span. When the cumulative switching current exceeds the critical erosion threshold, the remaining material in the DC contactor contacts is consumed at a rapid rate, causing a rapid increase in contact resistance. much smaller At that time, the cumulative on / off power consumption score is returned. Approaching 0; much greater than At that time, the cumulative on / off power consumption score is returned. Approaching 100.

[0087] (3) High current breaking score normalization The damage to contacts caused by high-current interruption is explosive. The thermal and mechanical stress generated by a single ultra-high-current interruption is equivalent to the total damage from hundreds or thousands of low-current interruptions. Therefore, the damage increases exponentially with the increase of the interruption current level. Thus, a normalized high-current interruption score is needed. : Scoring of large current breaking , means as follows:

[0088] This represents an exponential coefficient greater than 1, which determines the degree of acceleration in the scoring process. The larger the value, the heavier the penalty for breaking a single large current. The exponent coefficient can be calibrated based on the condition that "a contactor is considered to have exhausted its lifespan if it breaks once under the limiting current". This indicates the cumulative scoring threshold, which can be set according to the contactor's rated breaking capacity. The scoring is based on the breaking capacity of the contactor when a large current is interrupted. When this threshold is exceeded, the DC contactor will end its life due to high current interruption. For example, if the contactor interrupts once under the ultimate current, its damage score should be close to or reach 100.

[0089] (4) Full load operating time normalization Full-load operation leads to heat accumulation, accelerating the oxidation and aging of contact materials. This damage accumulates approximately linearly over a certain period. However, when other damage already exists in the DC contactor (such as increased contact resistance), the thermal effect of full-load operation is amplified. Therefore, the full-load operation time... Normalized representation: Normalized full-load operation score , means as follows

[0090] in, This indicates the maximum continuous operating time during which the temperature rise of a DC contactor can stabilize and not exceed the allowable limit under rated current. This time is typically provided by the manufacturer. Beyond this time, thermal damage enters a new nonlinear phase. Normalized Full-Load Operation Rating Different normalization processes are applied with a 60-point threshold. (When running at full load...) Less than or equal to the maximum continuous running time When the DC contactor has not yet entered the accelerated aging zone, it indicates that the full-load operating time is... Greater than the maximum continuous running time When this occurs, it indicates that the DC contactor has entered the overload region, and the damage accelerates linearly with a steeper slope. When the excess reaches a certain point... At that time, the full-load operation score reached 100.

[0091] At this point, the four heterogeneous data points—total number of operations, cumulative on / off current, high current breaking score, and full load operating time—have been normalized to a range of 0 to 100. The next step is to merge these four normalized data points into another operating load score, which is also between 0 and 100.

[0092] S612: The weighted average of the normalized total number of operations, cumulative on / off current, high current breaking score, and full-load operating time is used to obtain the operating load score. The operating load score is between 0 and 100 and is used to reflect the cumulative operating load level of the DC contactor. 0 points indicates the lowest load and 100 points indicates that the load has reached its limit.

[0093] A fixed weight can be used to calculate the weighted average of the normalized total number of operations score, normalized cumulative on / off charge score, normalized high current breaking score, and normalized full load operation score to obtain the operating load score. Alternatively, dynamic weights can be used based on the overall damage status of the contactor, assigning different weights to the same index under different damage states, for example, by introducing a lightweight machine learning model for dynamic fusion.

[0094] S620: A weighted average is applied to the breaking damage score, current drift, temperature rise rate deviation, and operating load score to obtain the damage score of the DC contactor. The higher the damage score, the more severe the damage to the DC contactor.

[0095] In one embodiment, a weighted average is applied to the breakage damage score, current drift, temperature rise rate offset, and operating load score using fixed weights. However, a simple linear weighted average, with its fixed weights, cannot capture the complex coupling and nonlinear relationships between the various dimensions of the indicators.

[0096] In another embodiment, a lightweight machine learning model is introduced to dynamically fuse the data, thereby assigning different weights to different indicators based on changes in contactor damage. The machine learning model can use gradient boosting trees (such as XGBoost, LightGBM, CatBoost, etc.) or random forests as pre-trained models for operational load scoring. These models are well-suited for handling nonlinear relationships and feature interactions.

[0097] In this embodiment, a gradient boosting tree is used as the model. The gradient boosting tree model can automatically learn the complex mapping relationship between different dimensional indicators in historical data, as well as between them and the final damage score, to provide segmented damage scores under different conditions. Current drift Temperature rise rate deviation and operational load scoring By assigning dynamic weights and obtaining the current damage score of the DC contactor, a more accurate and robust evaluation result than traditional methods is obtained, including the following steps: S621: Construct a training dataset based on normalized break-through damage score, current drift, temperature rise rate offset, and operating load score. The host records the normalized segmental damage scores obtained at different times. Current drift Temperature rise rate deviation and operational load scoring The evaluation values ​​of these four core dimensions form the original feature vector.

[0098] The failure of DC contactors is usually the result of long-term coupled stresses from multiple physical fields such as electricity, heat, and force, rather than a linear accumulation of a single indicator. Therefore, it is necessary to expand the original four evaluation values, construct higher-order interactive features, quantify the coupling effects between indicators, and inject these domain-specific common sense concepts into the pre-trained model to guide the model in learning those higher-order patterns that are crucial to the final damage assessment. The interactive features used in this embodiment are: The co-deterioration index represents the physical relationship between the fracture damage score and the temperature rise rate deviation. The co-deterioration index is expressed as: This indicates that when a sudden abnormal temperature rise occurs simultaneously with a segmental abnormality, it foreshadows severe deterioration / damage to the contact points of the DC contactor. For example, a single high breaking capacity damage can exacerbate contact material ablation and molten pool splashing, leading to an irreversible increase in contact resistance. This increased contact resistance generates more Joule heat during subsequent current flow, manifesting as a higher rate of temperature rise deviation. A high synergistic deterioration index means the contactor is experiencing a vicious cycle of breaking capacity damage → increased contact resistance → intensified temperature rise, and the contact structure may have already suffered severe deterioration or damage, with the degree of damage far exceeding the linear sum of the two indices.

[0099] The risk amplification factor represents the physical relationship between current drift and operating load score. The risk amplification factor is expressed as: The risk amplification factor indicates that severe current sensor drift and high operating loads exacerbate the risk of current misjudgment, measuring the amplified risk of sensor drift under high loads. The operating load score reflects the total electrical stress borne by the contactor, and its calculation is highly dependent on the accuracy of the current data. A high current drift means that the sensor measurement has deviated from the true value. If the operating load score is also high at this time, it indicates that the evaluation method is assessing a "very fatigued" contactor based on "incorrect" current data, leading to a severe underestimation of cumulative electrical wear and causing it to unknowingly exceed the failure threshold. A high risk amplification factor indicates extremely low confidence in the evaluation results and a sharply increased risk of failure.

[0100] The Shortest Board Effect Index, taking the maximum value among the four core dimensions, reflects the idea that the "weakest link" determines the overall health. The Shortest Board Effect Index is expressed as: Failure of DC contactors is often triggered by the index that reaches its limit first. For example, a contactor's breaking damage score may be close to 100 (approaching welding), but its operating load score may only be 60. In this case, the overall damage status should be dominated by the breaking damage score. The weakest link index allows pre-trained models to directly focus on the most severe abnormal dimension, avoiding the average effect of other normal dimensions from masking the core risk.

[0101] Assign a true damage score to each sample data point, with a value ranging from 0 to 100. Obtaining the true damage score, which serves as a label for model training, is crucial to this method and can be calibrated through one or more of the following methods: Laboratory offline calibration: In a laboratory environment, accelerated aging tests (such as frequent high-current interruption) are performed on contactors of the same model, and their static contact resistance is measured directly using a high-precision instrument (such as a micro-ohmmeter) at regular intervals. The measured contact resistance values ​​are then recorded. According to the preset mapping relationship (for example, the initial resistance is...), The failure resistance threshold is ,but The data is converted into damage scores from 0 to 100, and the initial model is trained using these labeled data.

[0102] Alternatively, on-site fault marking: During the actual operation of the charging pile, when the DC contactor needs to be repaired or replaced due to serious damage (such as contact welding or disconnection failure), the host records the historical characteristic data of the contactor in the period before the failure and marks its final damage score as 100 (or a failure threshold close to 100). These on-site fault data are used for model retraining or fine-tuning.

[0103] The original feature vectors, interaction features, and corresponding true damage scores are used together as the training dataset for the pre-trained model.

[0104] S622: Constructing a pre-trained damage scoring model based on the gradient boosting tree model. In this embodiment, the existing gradient boosting tree model is improved based on the physical characteristics and business constraints of the charging pile DC contactor to adapt to the needs of DC contactor damage assessment.

[0105] First, since the vast majority of data used for model training is collected under conditions where the DC contactor is not significantly damaged (as significant damage can be detected manually and does not require evaluation using the method of this invention), this invention employs a weighted focus loss function suitable for regression tasks. The weighted focus loss function is expressed as follows:

[0106] in, This represents the loss value of the weighted focus loss function. Indicates the first The true damage score of each sample Indicates the first The model predicts damage scores for each sample. and The values ​​range from 0 to 100. This represents the absolute error of the prediction, reflecting the deviation between the predicted value and the actual value. This represents the prediction confidence level. The smaller the error, the closer the value is to 1; the larger the error, the closer the value is to 0. Represents the sample weight coefficient. This indicates that the damage score is indeed higher than [the target score]. When that time, a higher weight is assigned to the sample, where, This represents the weighting amplification factor, used to increase the attention given to highly damaged samples; the preferred range is 5 to 10. This indicates an indicator function that executes when the condition is true ( The value is 1 when the condition is met, and 0 otherwise. This indicates a custom high damage threshold; for example, a damage score greater than 70 is defined as high damage. This represents the focus parameter, used to control the weight decay rate of difficult samples, with a preferred range of 1.5 to 3.0.

[0107] The weighted focus loss function has a dual adjustment mechanism: a sample weighting mechanism, through... This item makes the true damage score Exceeding the threshold Key samples are given higher weights, forcing the model to learn the feature patterns of these samples. This, along with a focus mechanism, is achieved through... This approach allows the model to focus more on difficult samples with large prediction errors (i.e., damage states that are difficult to predict accurately), while assigning lower weights to simple samples that have been predicted accurately, thereby concentrating the model's learning ability on the boundary regions that most need optimization.

[0108] Secondly, considering the temporal cumulative and irreversible nature of damage evolution in DC contactors, this invention introduces a temporal smoothing regularization term into the objective function to penalize drastic changes in predicted values ​​between adjacent time slices. The temporal smoothing regularization term is expressed as follows:

[0109] in, Represents a regular value. and These represent the same DC contactor at two adjacent evaluation times. and The model predicts damage scores. This represents the regularization strength coefficient, used to control the weight of the temporal smoothing constraint in the entire objective function. This indicates the number of historical evaluations for the same DC contactor. This represents the time interval between two adjacent evaluation moments, and the unit can be seconds, minutes, or hours, depending on the evaluation frequency. Represents the time decay constant, and represents the memory length of the damaged state, in units of 1 / 2π. Maintain consistency. Time decay constant. It reflects the memory length of the contactor's damage state. When hour, This indicates a short time interval, and the predicted values ​​should be highly smooth. hour, This indicates a longer time interval, suggesting that the damage may have undergone a qualitative change, and the smoothing constraint is correspondingly weakened. The time decay constant can be set according to the aging characteristics of the DC contactor. The value of is important for rapidly deteriorating scenarios such as frequent high-current interruptions. Take the smaller value, such as 1 hour; for a slow aging mode like typical home charging, Then take the larger value, such as 24 hours or longer.

[0110] Combining the weighted focus loss function with the temporal smoothing regularization term yields the complete objective function for training the gradient boosting tree model. The objective function is then... Represented as: ,in, This represents the total number of samples in the training set. By minimizing this objective function, the model fits the training data while ensuring the temporal continuity and physical plausibility of the prediction results.

[0111] S623: Train the pre-trained injury scoring model using the training dataset to obtain the injury scoring model. Divide the training dataset into a training set (e.g., the first 70% of the data) and a validation set (e.g., the last 30% of the data) in chronological order. Note that the division must be in chronological order to prevent future data leaks.

[0112] The pre-trained model for injury scoring is trained using the training set, and the model with the smallest objective function value on the validation set is selected as the final model, i.e., the injury scoring model. The hyperparameters of the model (such as the number of decision trees, the maximum depth of the trees, the learning rate, L1 / L2 regularization coefficients, etc.) are tuned using the validation set. The optimal combination of hyperparameters that minimizes the error on the validation set can be found through methods such as grid search or Bayesian optimization to prevent the model from overfitting.

[0113] To maintain the long-term accuracy of damage assessment, the model needs to have the ability to learn continuously. The host can be retrained periodically, for example weekly or monthly, using fresh historical data accumulated during this period (including newly occurring fault data) to adapt to the slow changes in contactor aging patterns. Alternatively, a variant or complementary mechanism of a gradient boosting tree model that supports incremental learning can be used to fine-tune the existing model when new, high-confidence fault samples are generated, without having to train from scratch each time.

[0114] This embodiment cleverly applies the gradient boosting tree model to the fusion process of multi-dimensional damage scoring, realizing a leap from linear weighting to nonlinear intelligent fusion, which greatly improves the accuracy and predictability of DC contactor damage assessment and provides strong technical support for the intelligent operation and maintenance of charging piles.

[0115] S624: Input the current breaking damage score, current drift, temperature rise rate deviation, and operating load score into the damage scoring model to obtain the current damage score. The damage score can be directly used to comprehensively assess the damage status of the DC contactor, displaying the score on the interface and providing corresponding countermeasures. When the damage score of the DC contactor reaches a level requiring attention or higher, the host will immediately issue a warning message, for example, via the MQTT protocol or an HTTP POST request to a remote server. The warning message will include the contactor's unique identifier, the current health status level, and specific recommendations, such as suggesting preventative checks or replacing the contactor.

[0116] The damage assessment method provided by this invention enables the host to analyze the internal condition of the DC contactor from multiple angles in real time. It can not only detect cumulative damage that is not visible on the surface, but also predict the risks that they may bring in advance, thereby ensuring the safe and stable operation of the entire charging pile system without affecting other charging services.

[0117] Example 2: A multi-dimensional damage assessment system for DC contactors in charging piles, such as Figure 2 As shown, the system for implementing any of the above embodiments includes a data acquisition module 100, a breaking feature module 200, a current drift module 300, a temperature rise offset module 400, an accumulated load module 500, and a comprehensive analysis module 600. The data acquisition module 100 is used by the host to acquire the current current value, current temperature and previous temperature of the target DC contactor during the charging process, as well as the voltage sequence and / or current sequence within a preset period during the previous disconnection process, and historical charging and disconnection data. The fault feature module 200 is used to obtain a fault damage score based on voltage transient features and / or current drop features; wherein, the voltage transient features are obtained by extracting the transient features of the voltage sequence, and the current drop features are obtained by extracting the drop features of the current sequence. The current drift mode 300 is used to obtain the current drift degree based on the difference between the current current value and the current compensation current value; wherein, the current compensation current value is obtained by the current current value and a preset current compensation coefficient; The temperature rise offset module 400 is used to obtain the temperature rise rate offset of the contact resistance based on the offset between the actual temperature rise rate and the expected temperature rise rate; wherein, the actual temperature rise rate is obtained by the current temperature and the previous temperature, and the expected temperature rise rate is obtained based on the compensation current value and the preset temperature rise model. The cumulative load module 500 is used to analyze the historical charging and disconnection data to obtain cumulative operating load data. The comprehensive analysis module 600 is used to comprehensively analyze the breakage damage score, the current drift, the temperature rise rate deviation, and the cumulative operating load data to assess the damage status of the DC contactor.

[0118] Various changes and modifications made without departing from the spirit and scope of this invention, and all equivalent technical solutions, also fall within the scope of this invention.

[0119] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0120] It should be noted that the phrase "an embodiment" or "embodiment" mentioned in the specification means that a specific feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Therefore, the phrase "an embodiment" or "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

Claims

1. A multi-dimensional method for assessing damage to DC contactors in charging piles, characterized in that, Includes the following steps: The host collects the current current value, current temperature and previous temperature of the target DC contactor during the charging process, as well as the voltage sequence and / or current sequence within the preset period during the last disconnection process, and historical charging and disconnection data. A fault damage score is obtained based on voltage transient characteristics and / or current drop characteristics; wherein, voltage transient characteristics are obtained by extracting transient characteristics from the voltage sequence, and current drop characteristics are obtained by extracting drop characteristics from the current sequence. The current drift is obtained based on the difference between the current current value and the current compensation current value; wherein, the current compensation current value is obtained by the current current value and a preset current compensation coefficient; The temperature rise rate deviation of the contact resistance is obtained based on the deviation between the actual temperature rise rate and the expected temperature rise rate; wherein, the actual temperature rise rate is obtained by the current temperature and the previous temperature, and the expected temperature rise rate is obtained based on the compensation current value and the preset temperature rise model. The historical charging and disconnection data are analyzed to obtain the cumulative operating load data; The damage score, current drift, temperature rise rate deviation, and cumulative operating load data are comprehensively analyzed to assess the damage status of the DC contactor.

2. The method according to claim 1, characterized in that, The method for obtaining a fault damage score based on voltage transient characteristics and / or current drop characteristics includes the following steps: Transient features are extracted from the voltage sequence to obtain voltage transient features; wherein, the voltage transient features include at least one or more of the following: peak voltage, voltage settling time, and number of voltage oscillations; Extract the current-decreasing features from the current sequence to obtain current-decreasing features; wherein, the current-decreasing features include at least one or more of the following: current-decreasing rate, current-decreasing time, and current-decreasing stability. An analysis is performed on one or more of the following indicators: peak voltage, voltage stabilization time, number of voltage oscillations, current drop rate, current drop time, and current drop stability, to obtain a breakage damage score. The higher the peak voltage, voltage stabilization time, number of voltage oscillations, current drop rate, and current drop time exceed a preset threshold, and the higher the current drop stability, the higher the breakage damage score.

3. The method according to claim 1, characterized in that, The current compensation current value is expressed as follows: in, Indicates the current current value. This indicates the current compensation current value. Indicates the amplitude gain coefficient. Indicates DC bias. and All are preset current compensation coefficients.

4. The method according to claim 1, characterized in that, The method for obtaining the temperature rise rate offset of the contact resistance based on the offset between the actual temperature rise rate and the expected temperature rise rate includes the following steps: Based on the difference between the current temperature and the previous temperature, and combined with the host's data acquisition frequency, the current actual temperature rise rate is obtained. Based on the current compensation current value and the preset temperature rise model, the current expected temperature rise rate is obtained; wherein the preset temperature rise model represents the relationship between the current value and the temperature rise rate. The temperature rise rate deviation of the contact resistance is obtained based on the degree to which the current actual temperature rise rate deviates from the current expected temperature rise rate.

5. The method according to claim 4, characterized in that, The temperature rise rate offset is also related to the offset duration; wherein, the longer the offset duration, the greater the temperature rise rate offset; the offset indicates that the temperature rise rate offset exceeds a preset offset threshold.

6. The method according to claim 1, characterized in that, The cumulative operating load data includes at least one or more of the following: total number of operations, cumulative on / off current, high current breaking score, and full load operating time. The total number of operations represents the total number of times the DC contactor completes a physical disconnection operation. The cumulative on / off current is obtained by accumulating the product of the compensation current value and the corresponding duration during the charging process; The high current breaking score is obtained by accumulating the level scores of the breaking current value; wherein, the breaking current value is the maximum compensation current value during the breaking process, and the level score represents the score of the corresponding level of the breaking current value according to the preset level. The full-load operating time is obtained by accumulating the duration during which the compensation current value exceeds the preset full-load current threshold during the charging process.

7. The method according to claim 1, characterized in that, The comprehensive analysis of the breakage damage score, current drift, temperature rise rate deviation, and cumulative operating load data to assess the damage status of the DC contactor includes the following steps: The breakage damage score, the current drift, the temperature rise rate offset, and the cumulative operating load data are normalized. The normalized fault damage score, the current drift, the temperature rise rate offset, and the cumulative operating load data are input into the damage scoring model to obtain the current damage score of the DC contactor. The damage scoring model is obtained by training a pre-trained damage scoring model, which is constructed based on a gradient boosting tree model. The pre-trained damage scoring model includes at least an objective function, which is expressed as follows: in, This represents the value of the objective function. This represents the total number of samples in the training set used to train the injury scoring pre-trained model. Indicates the first The true damage score of each sample Indicates the first The model predicts damage scores for each sample. Represents the sample weight coefficient. Indicates the focus parameter. This represents the regularization strength coefficient. This indicates the number of historical evaluations of the same DC contactor. and These represent the DC contactor at two adjacent evaluation times. and The model predicts damage scores. This represents the time interval between two adjacent evaluation moments. This represents the time decay constant.

8. A multi-dimensional charging pile DC contactor damage assessment system, used to implement the method as described in any one of claims 1 to 7, characterized in that, The system includes a data acquisition module, a breaking characteristic module, a current drift module, a temperature rise offset module, an accumulated load module, and a comprehensive analysis module; The data acquisition module is used by the host to acquire the current current value, current temperature and previous temperature of the target DC contactor during the charging process, as well as the voltage sequence and current sequence within the preset period during the previous disconnection process, and historical charging and disconnection data. The fault feature module is used to obtain a fault damage score based on voltage transient features and / or current drop features; wherein, the voltage transient features are obtained by extracting the transient features of the voltage sequence, and the current drop features are obtained by extracting the drop features of the current sequence; The current drift module is used to obtain the current drift degree based on the difference between the current current value and the current compensation current value; wherein, the current compensation current value is obtained by the current current value and a preset current compensation coefficient; The temperature rise offset module is used to obtain the temperature rise rate offset of the contact resistance based on the offset between the actual temperature rise rate and the expected temperature rise rate; wherein, the actual temperature rise rate is obtained by the current temperature and the previous temperature, and the expected temperature rise rate is obtained based on the compensation current value and the preset temperature rise model. The cumulative load module is used to analyze the historical charging and disconnection data to obtain cumulative operating load data; The comprehensive analysis module is used to comprehensively analyze the breakage damage score, the current drift, the temperature rise rate deviation, and the cumulative operating load data to assess the damage status of the DC contactor.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1 to 7.

10. A multi-dimensional charging pile DC contactor damage assessment device, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in any one of claims 1 to 7.

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