Method and system for judging service life of high-voltage direct-current contactor

Abstract

The invention relates to the technical field of electronic device state evaluation, in particular to a service life judgment method and system for a high-voltage direct-current contactor. The method comprises the following steps: in each on-off action process of the direct current contactor, synchronously acquiring arc duration, peak current, contact temperature rise and pull-in delay time to form a physical quantity data set of single operation; calculating a thermal damage component according to the contact temperature rise and the arc duration, multiplying the peak current square by the contact resistance obtained by real-time measurement to obtain an electrical damage component, and determining a mechanical damage component based on the pull-in delay time; and calculating the weighted sum of the thermal damage component, the electrical damage component and the mechanical damage component, and recording the weighted sum as a basic damage value. Calculation is carried out based on field real-time data, the actual degradation process under different operation currents, operation frequencies and temperature rise conditions is accurately reflected, and the authenticity of life prediction is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic device state evaluation, and in particular to a life determination method and system for a high-voltage direct-current contactor. BACKGROUND

[0002] The high-voltage direct-current contactor bears the task of frequently breaking and closing high-voltage and large-current, and its contacts are prone to degradation under the multiple actions of arc impact, temperature cycle, and mechanical wear, including contact ablation, resistance increase, metal migration and welding risk, etc. These degradation processes have strong randomness and irreversibility, which makes the actual service life of the contactor often significantly different from its nominal life. If the health status of the contactor cannot be accurately mastered, it may lead to unexpected failure of the equipment in operation, and further cause system failure or even major safety accidents.

[0003] In the prior art, the life of the high-voltage direct-current contactor is mainly evaluated by the following methods: one is to rely on laboratory type test, using standardized accelerated aging test to calculate the life model; the other is to maintain based on fixed period replacement strategy in the device running site. These methods have obvious limitations. The laboratory accelerated test has large difference with the actual working condition, and it is difficult to reflect the real degradation path of the contactor in complex environment; the fixed period replacement strategy cannot make dynamic adjustment according to the actual load of the equipment, which easily leads to two extreme situations: early replacement causes waste of resources, and delayed replacement brings the risk of sudden failure. In addition, the traditional detection method mostly uses a single index (such as resistance, temperature rise or number of actions) for judgment, without considering the comprehensive damage accumulation process under the coupling of multiple physical fields, resulting in low life prediction accuracy. SUMMARY

[0004] Therefore, it is necessary to provide a life determination method and system for a high-voltage direct-current contactor to solve at least one of the above technical problems.

[0005] To achieve the above-mentioned purpose, a life determination method for a high-voltage direct-current contactor comprises the following steps: Step S1: during each on-off action process of the direct-current contactor, the arc duration time, peak current, contact temperature rise and attraction delay time are synchronously collected to form a single operation physical quantity data set; Step S2: the thermal damage component is calculated according to the contact temperature rise and the arc duration time, the electrical damage component is obtained by multiplying the peak current square with the real-time measured contact resistance, and the mechanical damage component is determined based on the attraction delay time; Step S3: calculate the weighted sum of the thermal damage component, the electrical damage component and the mechanical damage component, denoted as a basic damage value; determine a coupling amplification coefficient through the numerical relationship of the three damage components, and multiply the basic damage value by the coupling amplification coefficient to obtain an equivalent damage value; Step S4: accumulate the equivalent damage values of continuous operations as a cumulative damage index, perform ratio operation on the real-time cumulative damage index and a pre-acquired damage threshold, and output a contactor residual life prediction value.

[0006] The application also provides a life determination system for a high-voltage direct-current contactor, which is used to execute the life determination method for a high-voltage direct-current contactor described above, and comprises: A physical quantity acquisition module is configured to synchronously acquire the arc duration, the peak current, the contact temperature rise and the attraction delay time during each on-off action of the direct-current contactor, and form a physical quantity data set of a single operation. A damage component calculation module is configured to calculate a thermal damage component according to the contact temperature rise and the arc duration, multiply the peak current square by the contact resistance measured in real time to obtain an electrical damage component, and determine a mechanical damage component based on the attraction delay time. An equivalent damage quantification module is configured to calculate the weighted sum of the thermal damage component, the electrical damage component and the mechanical damage component, denoted as a basic damage value; determine a coupling amplification coefficient through the numerical relationship of the three damage components, and multiply the basic damage value by the coupling amplification coefficient to obtain an equivalent damage value. A life prediction output module is configured to accumulate the equivalent damage values of continuous operations as a cumulative damage index, perform ratio operation on the real-time cumulative damage index and a pre-acquired damage threshold, and output a contactor residual life prediction value.

[0007] The life determination method for a high-voltage direct-current contactor provided by the application can accurately quantify the thermal damage, the electrical damage and the mechanical damage of the contactor in each operation by synchronously acquiring the arc duration, the peak current, the contact temperature rise and the attraction delay time and the like in each on-off operation of the contactor, so as to form comprehensive single-operation damage data. The method can make the thermal damage evaluation more scientific and reasonable by analyzing the temperature rise change caused by the arc in stages and performing weighted calculation on the temperature rise contributions in the three stages of rapid temperature rise, high-temperature maintenance and slow temperature drop, can accurately reflect the wear degree of the contactor caused by the electrical load by combining the real-time measurement of the peak current and the contact resistance to calculate the electrical damage and considering the resistive loss and the arc energy consumption, and can quantify the influences of mechanical wear and operation state change by comprehensively analyzing the attraction delay time offset and the operation frequency and respectively adopting linear or exponential amplification coefficients.

[0008] Further, through the coupling analysis of thermal, electrical and mechanical three damage components, the thermal-electric synergistic damage and mechanical-thermal synergistic damage states can be identified, and the coupling amplification coefficient is dynamically adjusted according to different damage states, so that the equivalent damage value can more comprehensively reflect the actual loss of the contactor. In the continuous operation process, the method can give higher weight to the recent high load operation through the accumulation and weighted processing of the equivalent damage value, reasonably reflect the comprehensive influence of history and current operation on the cumulative damage, and respond to abnormal load conditions in time through the acceleration accumulation mode.

[0009] The threshold value is calculated by using the cumulative damage data of failure obtained by the accelerated aging test, and the real-time cumulative damage index is compared with the threshold value through ratio operation, so that the residual life of the contactor can be dynamically quantified, and the accurate prediction of the residual operation times can be realized. Overall, through the multi-dimensional physical quantity acquisition, the phased and typed damage quantification, the dynamic coupling analysis and the real-time accumulation and threshold comparison, the method can comprehensively, accurately and dynamically evaluate the running state and life of the high-voltage direct-current contactor, provide a scientific basis for the maintenance decision and preventive replacement of the equipment, improve the operation reliability of the equipment, reduce the fault risk, at the same time, reduce unnecessary maintenance cost, realize efficient and safe power system management. BRIEF DESCRIPTION OF DRAWINGS

[0010] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-restrictive embodiments made with reference to the accompanying drawings: Figure 1 A step flowchart of a life determination method for a high-voltage direct-current contactor according to the present application; Figure 2 A schematic diagram of a thermal damage component calculation of an embodiment of the present application; Figure 3 A schematic diagram of an electrical damage component calculation flowchart of an embodiment of the present application; Figure 4 A module schematic diagram of a life determination system for a high-voltage direct-current contactor according to the present application. DETAILED DESCRIPTION

[0011] The technical method of the present application will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0012] In addition, the accompanying drawings are included to provide a further understanding of the present application, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application. In the drawings:

[0013] It is to be understood that, although terms such as "first", "second", and so on can be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the exemplary embodiments, a first element can be referred to as a second element, and similarly a second element can be referred to as a first element. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0014] To achieve the above object, there is provided Figures 1 to 4 The present application provides a life determination method for a high-voltage DC contactor, the method comprising the following steps: Step S1: During each on-off action of the DC contactor, the arc duration, peak current, contact temperature rise, and closing delay time are synchronously collected to form a single operation physical quantity data set; Step S2: The thermal damage component is calculated according to the contact temperature rise and arc duration, the electrical damage component is obtained by multiplying the peak current square with the real-time measured contact resistance, and the mechanical damage component is determined based on the closing delay time; Step S3: The weighted sum of the thermal damage component, the electrical damage component, and the mechanical damage component is calculated, which is recorded as a basic damage value; the coupling amplification coefficient is determined through the numerical relationship of the three damage components, and the equivalent damage value is obtained by multiplying the basic damage value by the coupling amplification coefficient; Step S4: The equivalent damage values of continuous operations are accumulated as a cumulative damage index, the real-time cumulative damage index is subjected to a ratio operation with a pre-acquired damage threshold value, and a contactor remaining life prediction value is output.

[0015] Further, the calculation of the thermal damage component according to the contact temperature rise and arc duration in step S2 comprises: The arc duration is divided into three time periods, i.e., a rapid temperature rise stage, a high temperature maintenance stage, and a slow temperature drop stage, according to the temperature rise variation characteristics; In an embodiment, the temperature rise-time curve collected during the on-off process is smoothed, and then the instantaneous change rate of temperature rise is calculated. When the change rate is greater than a preset rising threshold, the interval is divided into a rapid temperature rise stage; when the temperature rise change rate is within a set small fluctuation range, the interval is marked as a high temperature maintenance stage; when the change rate is less than a preset falling threshold, it is identified as a slow temperature drop stage.

[0016] For example, for an arc process lasting 20 ms, if the temperature rise rises from 30°C to 120°C in the first 6 ms, the segment is identified as a rapid temperature rise stage; the temperature rise fluctuates around 120°C for the subsequent 10 ms, which is identified as a high temperature maintenance stage; and the temperature rise drops from 120°C to 70°C for the last 4 ms, which is marked as a slow temperature drop stage.

[0017] It should be noted that the division of the three stages is not fixed in time, but is dynamically identified based on the temperature rise change characteristics, thereby ensuring the adaptability to different arc conditions.

[0018] The average temperature rise values of the rapid temperature rise stage, the high temperature maintenance stage and the slow temperature drop stage are extracted respectively; In an embodiment, after completing the stage division of the arc duration, all temperature rise sampling points in the rapid temperature rise stage, the high temperature maintenance stage and the slow temperature drop stage are counted respectively, and the arithmetic average method is used to calculate the average temperature rise values of each stage. The time boundaries of each stage can be automatically extracted according to the segmentation results obtained in the previous step, and then the temperature rise data in the time period is averaged.

[0019] For example, if 30 temperature rise data points are collected in the rapid temperature rise stage, with temperature rise values between 30°C and 120°C, the average temperature rise of the rapid temperature rise stage can be obtained by averaging the 30 data points. Similarly, the average temperature rises of the high temperature maintenance stage and the slow temperature drop stage can also be obtained by the same method respectively.

[0020] The average temperature rise value of the high temperature maintenance stage is multiplied by the corresponding time length to obtain the main thermal damage contribution, and the average temperature rise values of the rapid temperature rise stage and the slow temperature drop stage are multiplied by the corresponding time length and a preset stage weight coefficient respectively and then added to obtain the secondary thermal damage contribution; In an embodiment, the contribution of the high temperature maintenance stage to thermal damage can be regarded as the main thermal damage source, so the average temperature rise value of the high temperature maintenance stage is directly multiplied by the time length of the stage to obtain the main thermal damage contribution. At the same time, for the rapid temperature rise stage and the slow temperature drop stage, since the temperature rise fluctuation is large and the thermal damage to the contact material is relatively secondary, the average temperature rise values of the two stages are multiplied by the corresponding time length, and then multiplied by the respective preset stage weight coefficient, and finally the two secondary contributions are added to obtain the secondary thermal damage contribution.

[0021] For example, if the average temperature rise of the high-temperature maintaining stage is 120℃ and the duration is 10ms, the main contribution is 120x10; if the average temperature rise of the fast-rising stage is 75℃, the duration is 6ms, and the weight coefficient is 0.6, the contribution is 75x6x0.6; if the average temperature rise of the slow-falling stage is 70℃, the duration is 4ms, and the weight is 0.5, the contribution is 70x4x0.5. The two secondary contributions are added to obtain the minor thermal damage contribution.

[0022] The main thermal damage contribution and the minor thermal damage contribution are summed to obtain the thermal damage component of a single operation.

[0023] In an embodiment, after the main thermal damage contribution and the minor thermal damage contribution are obtained, the two parts are summed to obtain the thermal damage component of a single on-off operation. The summation process adopts linear superposition, does not introduce any additional nonlinear coefficient, and ensures the interpretability of the calculation model.

[0024] For example, in the aforementioned numerical example, the main thermal damage contribution is 120x10, which is assumed to be 1200; the minor thermal damage contribution (the sum of the fast-rising and slow-falling contributions) is assumed to be 420, and the sum of the two is 1620, which can be used as the thermal damage component of the on-off operation.

[0025] Referring to Figure 2 , the present application provides a thermal damage component calculation schematic diagram, in which the contact temperature rise changes with time and is divided into three time periods: a fast-rising stage, a high-temperature maintaining stage, and a slow-falling stage. Specifically, the temperature rise of the fast-rising stage increases from T1 to T3, and the corresponding time is ; the temperature rise of the high-temperature maintaining stage is maintained around T2, and the corresponding time is ; the temperature rise of the slow-falling stage decreases from T2 to the ambient temperature, and the corresponding time is The calculation of the thermal damage component includes a main thermal damage contribution and a minor thermal damage contribution. The main thermal damage contribution is obtained by multiplying the average temperature rise T2 of the high-temperature maintaining stage by the time length , and the minor thermal damage contribution is obtained by multiplying the average temperature rise T1 of the fast-rising stage and the average temperature rise T3 of the slow-falling stage by the corresponding time length , and then summing the weighted values, and finally adding the main thermal damage contribution and the minor thermal damage contribution to obtain the thermal damage component of a single operation, i.e., T2x .

[0026] For example, when the average temperature rise of the fast-rising stage is 75℃, the duration is 6ms, and the weight coefficient is 0.6, the contribution is 75x6x0.6; if the average temperature rise of the slow-falling stage is 70℃, the duration is 4ms, and the weight is 0.5, the contribution is 70x4x0.5. The two secondary contributions are added to obtain the minor thermal damage contribution. , stage weight w1=0.8, w3=0.6, then the heat damage component of the operation can be calculated by substituting the formula. In the process of calculating the heat damage component, the length of time and the temperature rise value of each stage should be determined according to the actual sampling data, and the stage weight coefficient can be preset according to the material characteristics and empirical data.

[0027] Further, the step S2 of multiplying the peak current square by the real-time measured contact resistance to obtain the electrical damage component includes: Real-time measurement of the contact resistance value before and after the on-off action, and the difference between the resistance value after the action and the resistance value before the action is taken as the resistance increment; In an embodiment, before each on-off action of the DC contactor, the resistance value of the contact before the action can be measured by applying a weak test current and collecting the corresponding voltage drop to obtain the reference contact resistance at the beginning of the operation. After the on-off action is completed, the system applies the same amplitude test current again and collects the new voltage drop to obtain the contact resistance value after the action. After completing the two measurements, the contact resistance value after the action is subtracted from the contact resistance value before the action to obtain the contact resistance increment caused by the operation.

[0028] For example, if the measured contact resistance before the action is 2.5m , and the measured value after the action is 3.0m , then the resistance increment is 0.5m .

[0029] The square of the peak current is multiplied by the resistance increment to obtain the resistive loss power, and the resistive loss power is multiplied by the arc duration to obtain the resistive loss energy; In an embodiment, after obtaining the resistance increment, the resistive loss is calculated by combining the peak current generated by the present on-off action. First, the square of the peak current is multiplied by the resistance increment to obtain the resistive loss power, and then the resistive loss power is multiplied by the arc duration to obtain the resistive loss energy.

[0030] For example, if the peak current is 150A and the resistance increment is , then the resistive loss power is ×0.0005=11.25W; if the arc duration is 20ms, then the resistive loss energy is 11.25×0.02=0.225J.

[0031] The product of the arc voltage and the peak current is measured to obtain the arc power, and the arc duration is multiplied to obtain the arc consumption energy; In an embodiment, the arc power can be obtained by simultaneously measuring the arc voltage and the peak current during the arc generation process. The arc voltage can be detected in real time by the voltage acquisition module during the on-off arc stage, and the peak current can be accurately recorded by the current sensor. When the two measured values are obtained, the arc power can be obtained by multiplication; the arc power is multiplied by the arc duration time to obtain the arc consumption energy generated in this operation.

[0032] For example, if the arc voltage is 45V and the peak current is 150A, the arc power is 45x150=6750W; if the arc duration time is still 20ms, the arc consumption energy is 6750x0.02=135J.

[0033] The electrical damage component of a single operation is obtained by adding the resistive loss energy and the arc consumption energy.

[0034] In an embodiment, after obtaining the resistive loss energy and the arc consumption energy, the two are added in a linear superposition manner to obtain the electrical damage component of a single operation. Since the resistive loss and the arc energy are directly acted on the contact material, the summation of the two can effectively reflect the comprehensive influence of the electrical factors on the contact life.

[0035] For example, if the resistive loss energy is 0.225J and the arc consumption energy is 135J, the electrical damage component of a single operation is 135.225J.

[0036] Referring to Figure 3 , the electrical damage component calculation flowchart provided by the present application first measures the resistance value of the DC contactor contact, and obtains the resistance R1 before operation and the resistance R2 after operation, respectively. Then, the resistance increment is calculated. On this basis, the square of the peak current is multiplied by the resistance increment to obtain the resistive loss power, and further multiplied by the arc duration time to obtain the resistive loss energy. At the same time, the product of the arc voltage and the peak current is measured to obtain the arc power, and then multiplied by the arc duration time to obtain the arc consumption energy. Finally, the resistive loss energy and the arc consumption energy are added to obtain the electrical damage component of a single operation. For example, when the contact resistance of the DC contactor before operation is 0.5mΩ, the contact resistance after operation is 0.55mΩ, the peak current is 1000A, and the arc duration time is 5ms, the electrical damage component of this operation can be obtained by the above calculation method.

[0037] Further, the multiplication of the attraction delay time offset and the operation frequency in step S2 to obtain the mechanical damage component includes: calculating the difference between the current attraction delay time and the standard attraction time of the DC contactor to obtain the attraction delay time offset; In an embodiment, the time between the closing start command and the contact completion of the closing is recorded by high-precision timestamps at each closing action, and the actual closing delay time of the current operation is obtained; the standard closing time of the DC contactor is obtained from the factory calibration data or the field calibration test and stored as a reference value; the actual closing delay time is subtracted from the standard closing time to obtain the closing delay time offset (which can be positive or negative).

[0038] For example, if the standard closing time of a certain type of contactor is 0.010 seconds (10 milliseconds), and the actual closing delay measured this time is 0.012 seconds (12 milliseconds), then the closing delay time offset is 0.002 seconds (2 milliseconds).

[0039] The total number of operations in the preset time window, and the current operation frequency is obtained by dividing the total number of operations by the length of the time window; In an embodiment, a time window length (e.g., 60 seconds, 300 seconds, etc.) for counting the number of operations is set in the system, the total number of closing actions in the time window is counted, and the current operation frequency is obtained by dividing the total number of operations by the length of the time window. The frequency can be updated in real time using a sliding window to reflect the instantaneous workload.

[0040] For example, if 60 seconds is taken as the time window, and 100 closing actions are counted in the window, then the current operation frequency is 100 / 60≈1.67 times / second (Hz).

[0041] When the closing delay time offset is positive, a linear amplification coefficient is used, and when the closing delay time offset is negative, an exponential amplification coefficient is used. The closing delay time offset is multiplied by the corresponding amplification coefficient, and then multiplied by the current operation frequency to obtain the mechanical damage component of a single operation.

[0042] In an embodiment, the amplification coefficient is selected according to the sign of the offset—when the offset is positive (the closing is slower than the standard), a linear amplification coefficient is used; when the offset is negative (the closing is faster than the standard), an exponential amplification coefficient is used; the linear amplification coefficient can be calculated as “1 plus the product of the offset and a preset proportion coefficient” (i.e., coefficient = 1 + offset × preset proportion coefficient), and the exponential amplification coefficient can be calculated as “the absolute value of the offset multiplied by the power of a preset exponential coefficient” (i.e., coefficient = e^|offset| × preset exponential coefficient). Offset Preset exponential coefficient Then the closing delay time offset is multiplied by the corresponding amplification coefficient, and then multiplied by the current operation frequency to obtain the mechanical damage component of a single operation.

[0043] For example, assuming that the preset proportional coefficient is 50 (unit: 1 / s), the preset exponential coefficient is 50 (unit: 1 / s), and the current operating frequency is 1.67 Hz: if the offset is +0.002 s, the linear amplification coefficient is 1+0.002*50=1.1, and the mechanical damage component is 0.002*1.1*1.67≈0.00367 (relative amount); if the offset is -0.001 s, the exponential amplification coefficient is e^(0.001*50)≈e^0.05≈1.0513, and the mechanical damage component is (-0.001)*1.0513*1.67≈-0.00175 (relative amount).

[0044] In another embodiment, to improve the robustness and applicability of the above calculation, a pre-processing and abnormality processing method for the offset and the frequency is further included: the continuously measured closing delay time offset can be subjected to moving average or median filtering to suppress transient pulse interference; the calculation of the operating frequency can be combined with threshold judgment (for example, when the frequency is lower than a certain low threshold, the lowest frequency value is used to avoid division by zero or numerical instability); and the upper and lower limit constraints can be set for the calculation result of the amplification coefficient to avoid unreasonable impact of extreme abnormal values on the cumulative damage.

[0045] For example, if the linear amplification coefficient calculation result exceeds 3.0, it can be truncated to 3.0 to prevent excessive amplification caused by a single abnormal delay.

[0046] Further, the use of the linear amplification coefficient when the closing delay time offset is positive and the use of the exponential amplification coefficient when the closing delay time offset is negative include: When the closing delay time offset is positive, the linear amplification coefficient is 1 plus the product of the offset and the preset proportional coefficient; In an embodiment, it is confirmed that the currently measured closing delay time offset is positive, indicating that the closing action of the DC contactor is slower than the standard closing time, and the mechanical state may have a slight wear or recession trend. In this case, the system calculates the linear amplification coefficient according to the formula , wherein represents the closing delay time offset, represents the preset proportional coefficient, which is used to adjust the amplification degree of the offset on the damage amount. Through this design, the larger the offset is, the higher the amplification coefficient is, so that the device is more sensitive to the case of abnormal increase in closing time.

[0047] For example, if the current offset is 2 ms and the proportional coefficient is 0.1, the linear amplification coefficient is 1+2*0.1=1.2, which is brought into the subsequent mechanical damage component calculation to truly reflect the accelerated wear trend of the device when the operating frequency is increased.

[0048] When the inductance delay time offset is negative, the exponential amplification coefficient is the natural constant multiplied by the preset exponential coefficient with the absolute value of the offset.

[0049] In an embodiment, it is detected that the inductance delay time offset is negative, i.e. the current inductance action is faster than the standard inductance time. This situation is usually caused by problems such as increased spring counterforce, excessive magnetization of the core, abnormal lubrication of the mechanism, or enhanced impact collision, etc. To avoid ignoring such risks, the system amplifies the offset in an exponential manner. The system calculates the exponential amplification coefficient according to wherein is the natural constant, is the absolute value of the inductance delay time offset, is the preset exponential coefficient for controlling the amplification rate.

[0050] For example, if the current offset is -1ms and the exponential coefficient is 0.5, the amplification coefficient is , which can significantly enhance the impact of abnormal increase in inductance speed, so that the subsequent damage model can accurately identify potential impact failures.

[0051] Further, the determination of the coupling amplification coefficient in step S3 through the numerical relationship of the three damage components includes: When the thermal damage component and the electrical damage component simultaneously exceed their respective historical average values, it is identified as a thermal-electrical synergistic damage state; In this embodiment, the controller compares the current thermal damage component with the historical average thermal damage, and simultaneously compares the current electrical damage component with the historical average electrical damage. When both current damage components exceed their corresponding long-term average levels, it is identified as a thermal-electrical synergistic damage state. This judgment logic indicates that significant abnormalities have occurred in the current working period under both thermal stress and electrical stress. The system captures the synergistic aggravation phenomenon of the device under the combined stress of high temperature and current fluctuation through this way.

[0052] For example, if the historical average thermal damage is 0.4, the historical average electrical damage is 0.5, and the current period obtains thermal damage of 0.7 and electrical damage of 0.8, respectively, which are significantly higher than the average values, then the system will mark this period as a "thermal-electrical synergistic damage state".

[0053] The product of the mechanical damage component and the thermal damage component is calculated, and when the product exceeds a preset synergistic threshold, it is determined as a mechanical-thermal synergistic damage state; ​In another embodiment, the mechanical damage component and the thermal damage component of the current cycle are obtained, and the product of the two is directly calculated as the synergy index, and then the product is compared with the preset synergy threshold. When the index value is greater than the synergy threshold, the system determines that the current cycle is in a mechanical-thermal synergy damage state. By multiplying, the coupling recognition of the mechanical wear accumulation and the phenomenon of lubrication degradation and friction aggravation caused by temperature rise is realized, so that the model can capture the rapid damage growth under the combined action of mechanical and thermal.

[0054] For example, if the mechanical damage component is 0.6, the thermal damage component is 0.7, and the product of the two is 0.42, and the preset synergy threshold is 0.4, the system determines that the mechanical-thermal synergy damage state occurs.

[0055] When no synergy damage state is detected, the coupling amplification coefficient is set to a first value; when only the thermo-electric synergy damage state is detected, the coupling amplification coefficient is set to a second value; when only the mechanical-thermal synergy damage state is detected, the coupling amplification coefficient is set to a third value; and when both synergy damage states are detected, the coupling amplification coefficient is set to a fourth value.

[0056] In yet another embodiment, the controller first confirms the determination results of the above two types of synergy states, and then selects the corresponding coupling amplification coefficient according to the preset strategy.

[0057] If no synergy damage state is detected, it means that the current working condition of the equipment is relatively stable, and the system sets the coupling amplification coefficient to a first value (for example, 1.0).

[0058] If only the thermo-electric synergy damage state is detected, the system sets the coupling amplification coefficient to a second value (for example, 1.2) for moderately increasing the damage weight caused by the combined action of thermo-electricity.

[0059] If only the mechanical-thermal synergy damage state is detected, the system sets the coupling amplification coefficient to a third value (for example, 1.3) to reflect the stronger accelerated damage effect caused by the superposition of mechanical and thermal.

[0060] When both synergy damage states are detected, the system sets the coupling amplification coefficient to a fourth value (for example, 1.5) to make the comprehensive damage model more accurately respond to the serious wear caused by the superposition of multiple source stresses.

[0061] For example, if the thermal damage of the current cycle significantly exceeds the average value, the electrical damage also exceeds the average value, and the product of the mechanical damage and the thermal damage also exceeds the synergy threshold, the system determines that both types of synergy damage exist, and therefore sets the coupling amplification coefficient to the fourth value 1.5.

[0062] Especially important is to establish a window self-adaptive adjustment mechanism for continuous triggering of the thermo-electric synergy damage state: Real-time record the operation sequence number of each time triggering the thermal-electric synergic damage state and count the continuous triggering times; When the continuous triggering times reach five, start the window length adjustment, reduce the historical data sliding window to two-thirds of the original value, and recalculate the historical average values of the thermal damage component and the electric damage component based on the reduced window; Continue the thermal-electric synergic damage state judgment using the updated historical average values, thereby realizing the sensitive identification of the accelerated degradation trend of the equipment.

[0063] Further, the thermal-electric synergic damage state when the thermal damage component and the electric damage component simultaneously exceed their respective historical average values includes: Establish a historical data sliding window for the thermal damage component and the electric damage component, wherein the historical data sliding window is set to a preset multiple of the number of the most recent continuous operations; In the present embodiment, the controller sets the length of the historical data sliding window to a preset multiple of the number of the most recent continuous operations, for example, twice the number of the most recent 20 operations, that is, the window covers the thermal damage and electric damage data of the most recent 40 operations. After each new operation is completed, the controller adds the latest thermal damage component and electric damage component to the sliding window, while removing the earliest data, thereby realizing dynamic updating and rolling storage of the data.

[0064] For example, if the sliding window length is set to 40 operations, and the current cumulative number of operations is 41, the system will remove the data of the first operation from the window, and only keep the data of the second to the 41st operation, which is used for subsequent average value calculation.

[0065] Calculate the arithmetic mean of the thermal damage components and the electric damage components in the historical data sliding window as the respective historical average values; In an embodiment, sum all the thermal damage components in the sliding window and divide by the window length to obtain the thermal damage historical average value, and similarly sum the electric damage components and divide by the window length to obtain the electric damage historical average value. The average values reflect the typical levels of thermal stress and electric stress under the recent operation period of the equipment, and can be used as a reference for determining abnormal states.

[0066] For example, if the sum of the thermal damage components of the most recent 40 operations in the sliding window is 18, then the thermal damage historical average value is 18 / 40=0.45; similarly, if the sum of the electric damage components is 20, then the electric damage historical average value is 20 / 40=0.5.

[0067] When the thermal damage component of a single operation exceeds its historical average value and the electric damage component of the single operation also exceeds its historical average value, it is determined that the current operation triggers the thermal-electric synergic damage state.

[0068] In an embodiment, the controller extracts the thermal damage component and the electrical damage component for each operation respectively, compares them with the historical average values respectively, and determines that the operation is in the thermal-electrical synergistic damage state when the thermal damage component is greater than the thermal damage historical average value and the electrical damage component is greater than the electrical damage historical average value.

[0069] For example, if the thermal damage component of the current operation is 0.6 and the electrical damage component is 0.7, and the historical average values are 0.45 and 0.5 respectively, the system determines that the current operation triggers the thermal-electrical synergistic damage state, and records the state for subsequent calculation of the coupling amplification coefficient.

[0070] Further, the step S4 of accumulating the equivalent damage values of the continuous operations as the cumulative damage index comprises: calculating the ratio of the average value of the equivalent damage values of the last ten operations to the average value of the equivalent damage values of the previous ten operations, and starting the accelerated cumulative mode when the ratio is greater than 1.3; In an embodiment, the controller obtains the equivalent damage values of the previous ten operations and the equivalent damage values of the earlier ten operations before the current period respectively, calculates the ratio of the average values of the two groups, and starts the accelerated cumulative mode when the ratio is greater than the preset threshold value 1.3.

[0071] For example, assuming that the average value of the equivalent damage values of the previous ten operations is 0.4 and the average value of the equivalent damage values of the last ten operations is 0.55, the ratio is 0.55 / 0.4=1.375, which is greater than 1.3, and the controller switches to the accelerated cumulative mode.

[0072] In the normal cumulative mode, the equivalent damage values are added with equal weights, and in the accelerated cumulative mode, the equivalent damage values of the last ten operations are multiplied by a weight coefficient of 1.2, and the equivalent damage values of the previous operations are multiplied by a weight coefficient of 0.9; In an embodiment, when in the normal cumulative mode, the controller adds the equivalent damage values of each operation to the cumulative damage index with equal weights, and when in the accelerated cumulative mode, the equivalent damage values of the last ten operations are multiplied by a weight coefficient of 1.2 and the equivalent damage values of the previous operations are multiplied by a weight coefficient of 0.9, so that the cumulative damage caused by the recent abnormal load accounts for a larger proportion.

[0073] For example, if the equivalent damage values of the last ten operations are 0.5, 0.6, 0.55, etc., multiplied by 1.2, they become 0.6, 0.72, 0.66 respectively, and the equivalent damage values of the previous ten operations are 0.4, 0.45, etc., multiplied by 0.9, they become 0.36, 0.405, and then added in time sequence to obtain a new cumulative damage index.

[0074] The weighted equivalent damage value is accumulated in time sequence to obtain the cumulative damage index at the current time.

[0075] In an embodiment, the controller sequentially accumulates the weighted equivalent damage value of each operation in time sequence of operation occurrence to form a continuous cumulative damage index sequence, which can reflect the current cumulative wear level of the equipment in real time and serve as the basis for life prediction and maintenance decision.

[0076] For example, assuming that the weighted equivalent damage values of the first three operations are 0.36, 0.405, and 0.6, respectively, the cumulative damage indexes are 0.36, 0.765 (0.36+0.405), and 1.365 (0.765+0.6), respectively, and so on until the latest operation.

[0077] Further, the ratio operation between the real-time cumulative damage index and the pre-acquired damage threshold in step S4 includes: Obtain the failure cumulative damage data of at least five samples through the accelerated aging test of the same type of DC contactor, and calculate the arithmetic mean and standard deviation thereof; In an embodiment, at least five samples of the same type of DC contactor are selected, and the accelerated aging operation is performed on each sample, and the cumulative damage value of each sample when reaching the failure state is recorded. Subsequently, the controller or data processing module statistically analyzes the failure cumulative damage data of all samples, calculates the arithmetic mean as a representative of the overall failure level, and calculates the standard deviation to reflect the difference between the samples.

[0078] For example, if the failure cumulative damage values of the five samples are 2.1, 2.3, 2.0, 2.4, and 2.2, respectively, the arithmetic mean is (2.1+2.3+2.0+2.4+2.2) / 5=2.2, and the standard deviation is about 0.15.

[0079] The arithmetic mean minus 1.5 times the standard deviation is taken as the damage threshold; In an embodiment, the controller sets the damage threshold by subtracting 1.5 times the standard deviation from the arithmetic mean according to the statistical results, so as to ensure that the threshold is slightly lower than the typical failure level, thereby warning the remaining life in advance.

[0080] For example, the arithmetic mean is 2.2 and the standard deviation is 0.15, so the damage threshold = 2.2 1.5×0.15=1.975.

[0081] The cumulative damage index at the current time is divided by the damage threshold to obtain the damage progress ratio, and the complement of the damage progress ratio is taken as the remaining life ratio; In an embodiment, the real-time cumulative damage index is divided by the preset damage threshold to obtain a damage progress ratio consumed by the current operation, and 1 is subtracted from the ratio to obtain a residual life ratio, reflecting the remaining operation capacity that the device can still withstand.

[0082] For example, if the current cumulative damage index is 0.8 and the damage threshold is 1.975, the damage progress ratio is 0.8 / 1.975≈0.405, and the residual life ratio is 1-0.405≈0.595.

[0083] The residual life ratio is multiplied by the total number of designed operations of the contactor to obtain an expected residual number of operations, and the expected residual number of operations is output as a residual life prediction value of the contactor.

[0084] For example, if the total number of designed operations of the contactor is 50,000 times and the residual life ratio is 0.595, the expected residual number of operations=50,000×0.595≈29,750 times.

[0085] The application also provides a life determination system 100 for a high-voltage direct-current contactor, which is used to execute the life determination method for the high-voltage direct-current contactor, and the life determination system 100 for the high-voltage direct-current contactor comprises: A physical quantity acquisition module 101 is configured to synchronously acquire an arc duration, a peak current, a contact temperature rise and a closing delay time during each on-off action of the direct-current contactor, and form a physical quantity data set of a single operation. A damage component calculation module 102 is configured to calculate a thermal damage component according to the contact temperature rise and the arc duration, multiply the peak current square by the real-time measured contact resistance to obtain an electrical damage component, and determine a mechanical damage component based on the closing delay time. An equivalent damage quantification module 103 is configured to calculate a weighted sum of the thermal damage component, the electrical damage component and the mechanical damage component, and record the sum as a basic damage value; determine a coupling amplification coefficient through a numerical relationship of the three damage components, and multiply the basic damage value by the coupling amplification coefficient to obtain an equivalent damage value. A life prediction output module 104 is configured to accumulate the equivalent damage values of continuous operations as a cumulative damage index, perform a division operation on the real-time cumulative damage index and a pre-acquired damage threshold, and output a residual life prediction value of the contactor.

[0086] Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the application file are intended to be included in the application.

[0087] ​The foregoing is considered as illustrative only of the principles of the application. Numerous modifications and changes will readily occur to those skilled in the art, and it is intended to embrace all such modifications and changes that fall within the scope of the application. Accordingly, the application is not to be restricted in scope to the specific embodiments disclosed herein but is to be accorded the full scope that the principles and novel features request appropriately granted.

Claims

1. A method for determining the lifespan of a high-voltage DC contactor, characterized in that, Includes the following steps: Step S1: During each switching operation of the DC contactor, the arc duration, peak current, contact temperature rise, and engagement delay time are collected synchronously to form a set of physical quantity data for a single operation. Step S2: Calculate the thermal damage component based on the contact temperature rise and arc duration, multiply the square of the peak current by the contact resistance measured in real time to obtain the electrical damage component, and determine the mechanical damage component based on the pull-in delay time. Step S3: Calculate the weighted sum of the thermal damage component, electrical damage component, and mechanical damage component, and record it as the basic damage value; The coupling amplification factor is determined by the numerical relationship between the three damage components, and the equivalent damage value is obtained by multiplying the basic damage value by the coupling amplification factor. Step S4: The equivalent damage value of continuous operation is used as the cumulative damage index. The ratio of the real-time cumulative damage index to the pre-acquired damage threshold is calculated, and the remaining life prediction value of the contactor is output.

2. The life determination method for high-voltage DC contactors according to claim 1, characterized in that, Step S2, which calculates the thermal damage component based on the contact temperature rise and arc duration, includes: The duration of the electric arc is divided into three periods according to the characteristics of temperature rise: rapid heating stage, high temperature maintenance stage, and slow cooling stage. The average temperature rise values ​​of the rapid heating phase, the high temperature maintenance phase, and the slow cooling phase were extracted separately. The average temperature rise during the high-temperature maintenance phase is multiplied by the corresponding time length to obtain the main thermal damage contribution. The average temperature rise during the rapid heating phase and the slow cooling phase are multiplied by the corresponding time length and the preset phase weighting coefficient, respectively, and then added together to obtain the secondary thermal damage contribution. The thermal damage component for a single operation is obtained by summing the contributions of primary and secondary thermal damage.

3. The life determination method for high-voltage DC contactors according to claim 2, characterized in that, In step S2, the electrical damage component is obtained by multiplying the square of the peak current by the contact resistance measured in real time. This component includes: The contact resistance value is measured in real time before and after the switching action, and the difference between the resistance value after the action and the resistance value before the action is used as the resistance increment. Multiplying the square of the peak current by the resistance increment yields the resistive power loss, and multiplying the resistive power loss by the arc duration yields the resistive energy loss. The arc power is obtained by measuring the product of the arc voltage and the peak current, and then multiplied by the arc duration to obtain the arc energy consumption. The electrical damage component of a single operation is obtained by adding the resistive energy loss to the arc energy consumption.

4. The life determination method for high-voltage DC contactors according to claim 3, characterized in that, In step S2, the mechanical damage component obtained by multiplying the pull-in delay time offset by the operating frequency includes: Calculate the difference between the current pull-in delay time and the standard pull-in time of the DC contactor to obtain the pull-in delay time offset; The total number of on / off operations within a preset time window is divided by the length of the time window to obtain the current operation frequency. When the pull-in delay time offset is positive, a linear amplification factor is used; when the pull-in delay time offset is negative, an exponential amplification factor is used. The pull-in delay time offset is multiplied by the corresponding amplification factor and then multiplied by the current operating frequency to obtain the mechanical damage component of a single operation.

5. The life determination method for high-voltage DC contactors according to claim 4, characterized in that, The use of a linear amplification factor when the pull-in delay time offset is positive and an exponential amplification factor when the pull-in delay time offset is negative includes: When the pull-in delay time offset is positive, a linear amplification factor of 1 is used, plus the product of the offset and the preset scaling factor. When the pull-in delay time offset is negative, the absolute value of the offset is multiplied by the preset exponential coefficient to the power of the natural constant using the exponential amplification factor.

6. The life determination method for high-voltage DC contactors according to claim 5, characterized in that, Step S3 involves determining the coupling amplification factor based on the numerical relationship between the three damage components, including: When both thermal damage and electrical damage components exceed their respective historical average values, it is identified as a thermo-electric synergistic damage state. Calculate the product of the mechanical damage component and the thermal damage component. When the product exceeds a preset synergistic threshold, it is determined to be a mechanical-thermal synergistic damage state. When no synergistic damage state is detected, the coupling amplification factor is set to the first value; when only thermoelectric synergistic damage state is detected, the coupling amplification factor is set to the second value; when only mechanical-thermal synergistic damage state is detected, the coupling amplification factor is set to the third value; and when both synergistic damage states are detected simultaneously, the coupling amplification factor is set to the fourth value.

7. The life determination method for high-voltage DC contactors according to claim 6, characterized in that, The condition where both thermal damage and electrical damage components exceed their respective historical averages is considered a thermoelectric synergistic damage state, including: Establish a sliding window for historical data of thermal damage components and electrical damage components, wherein the historical data sliding window is set to a preset multiple of the most recent consecutive operation count; The arithmetic mean of the thermal damage component and the electrical damage component within the sliding window of historical data are calculated separately as their respective historical averages. When the thermal damage component of a single operation exceeds its historical average and the electrical damage component of a single operation also exceeds its historical average, the current operation is determined to have triggered a thermo-electric synergistic damage state.

8. The life determination method for high-voltage DC contactors according to claim 7, characterized in that, The equivalent damage value of the cumulative continuous operations in step S4, used as a cumulative damage index, includes: Calculate the ratio of the average equivalent damage value of the most recent ten operations to the average equivalent damage value of the previous ten operations. When the ratio is greater than 1.3, activate the accelerated accumulation mode. In normal accumulation mode, the equivalent damage value is accumulated with equal weight. In accelerated accumulation mode, the equivalent damage value of the most recent ten operations is multiplied by a weighting factor of 1.2, and the equivalent damage value of previous operations is multiplied by a weighting factor of 0.

9. The weighted equivalent damage values ​​are accumulated in chronological order to obtain the cumulative damage index at the current moment.

9. The life determination method for high-voltage DC contactors according to claim 8, characterized in that, Step S4 involves calculating the ratio between the real-time cumulative damage index and the pre-acquired damage threshold, including: Accelerated aging tests were conducted on at least five samples of the same model of DC contactor to obtain cumulative damage data for failure, and the arithmetic mean and standard deviation were calculated. The damage threshold is calculated by subtracting 1.5 times the standard deviation from the arithmetic mean. Divide the current cumulative damage index by the damage threshold to obtain the damage progress ratio, and take the complement of the damage progress ratio as the remaining lifespan ratio. Multiply the remaining lifespan percentage by the total number of designed operations of the contactor to obtain the expected number of remaining operations, and output the expected number of remaining operations as the predicted value of the contactor's remaining lifespan.

10. A life determination system for high-voltage DC contactors, characterized in that, For performing the life determination method for a high-voltage DC contactor as described in claim 1, the life determination system for the high-voltage DC contactor includes: The physical quantity acquisition module is used to synchronously acquire the arc duration, peak current, contact temperature rise and closing delay time during each switching operation of the DC contactor, forming a set of physical quantity data for a single operation. The damage component calculation module is used to calculate the thermal damage component based on the contact temperature rise and arc duration, multiply the square of the peak current by the contact resistance measured in real time to obtain the electrical damage component, and determine the mechanical damage component based on the pull-in delay time. The equivalent damage quantification module is used to calculate the weighted sum of thermal damage components, electrical damage components, and mechanical damage components, which is recorded as the base damage value. The coupling amplification factor is determined by the numerical relationship of the three damage components, and the equivalent damage value is obtained by multiplying the base damage value by the coupling amplification factor. The life prediction output module is used to accumulate the equivalent damage value of continuous operation as the cumulative damage index. It calculates the ratio between the real-time cumulative damage index and the pre-acquired damage threshold, and outputs the predicted value of the remaining life of the contactor.

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