Metallized film capacitor operation state evaluation method, device and equipment

Abstract

The invention provides a method, a device and equipment for evaluating the running state of a metallized film capacitor, and relates to the technical field of metallized film capacitors. The method comprises the following steps: in an operation process of a to-be-tested metallized film capacitor, collecting a pulse current signal generated by the to-be-tested metallized film capacitor in a set time period; based on the pulse current signal, determining the number of self-healing discharge times of the metalized film capacitor to be tested in a set time period, the discharge time interval between every two adjacent self-healing discharge times, and the discharge capacity of each self-healing discharge; and inputting the self-healing discharge times, the discharge time interval and the discharge capacity into a pre-trained state evaluation model, and determining the operation state of the to-be-tested metallized film capacitor. According to the invention, the operation state of the metallized film capacitor can be accurately evaluated on line.

Description

Technical Field

[0001] This invention relates to the field of metallized film capacitor technology, and in particular to a method, apparatus and equipment for evaluating the operating status of metallized film capacitors. Background Technology

[0002] Modular multilevel converters (MMCs) have been widely used in flexible DC transmission technology. Metallized film capacitors (MFCs) are key components in MMCs, responsible for stabilizing voltage and filtering ripple. Their operating status directly affects the overall safety and reliability of the flexible DC system. Therefore, it is necessary to evaluate the operating status of the metallized film capacitors within the MMC to ensure the safe and reliable operation of the flexible DC system.

[0003] As capacitors operate continuously, their condition deteriorates, and their capacitance decreases accordingly. Most related technologies determine the capacitor's operating condition by measuring its capacitance. Capacitance measurement methods are mainly divided into two categories: offline measurement and online indirect estimation. Offline measurement primarily involves periodically stopping and disassembling the capacitor to directly measure its capacitance, thus assessing its operating condition. Online indirect estimation mainly estimates the capacitance by measuring the ripple current online, also assessing the capacitor's operating condition.

[0004] On the one hand, the difficulty in disassembling metallized film capacitors encapsulated in MMC makes offline testing and evaluation methods unsuitable. On the other hand, online measurement of ripple current to estimate capacitance and assess capacitor operating status is easily affected by topological harmonics and load fluctuations, leading to low accuracy in early assessments of deteriorating operating conditions. Summary of the Invention

[0005] This invention provides a method, apparatus, and device for evaluating the operating status of metallized film capacitors, thereby solving the problem in related technologies that cannot achieve accurate online evaluation of the operating status of metallized film capacitors.

[0006] In a first aspect, embodiments of the present invention provide a method for evaluating the operating status of a metallized film capacitor, comprising: During the operation of the metallized film capacitor under test, the pulse current signal generated by the metallized film capacitor under test within a set time period is collected; Based on the pulse current signal, the number of self-healing discharges of the metallized film capacitor under test within the set time period, the discharge time interval between two adjacent self-healing discharges, and the discharge amount of each self-healing discharge are determined. The self-healing discharge count, the discharge time interval, and the discharge amount are input into a pre-trained state evaluation model to determine the operating state of the metallized film capacitor under test.

[0007] Optionally, there are multiple pulse current signals; each pulse current signal corresponds to one self-healing discharge. The step of determining, based on the pulse current signal, the number of self-healing discharges of the metallized film capacitor under test within the set time period, the discharge time interval between two adjacent self-healing discharges, and the discharge amount of each self-healing discharge includes: The number of self-healing discharges is determined based on the number of pulse current signals. The discharge start time of each pulse current signal is determined, and the discharge time interval between two adjacent self-healing discharges is determined based on the difference between the discharge start times of two adjacent pulse current signals. Integrating each pulse current signal yields the discharge amount for each self-healing discharge.

[0008] Optionally, before inputting the number of self-healing discharges, the discharge time interval, and the discharge amount into a pre-trained state evaluation model to determine the operating state of the metallized film capacitor under test, the method further includes: Metallized film capacitors under different operating conditions were prepared using a degraded platform, and pulse current signals of the metallized film capacitors under different operating conditions were collected. Using the pulse current signals of the metallized film capacitor under different operating conditions, a state evaluation model is trained to obtain a trained state evaluation model.

[0009] Optionally, the degradation platform includes: a DC power supply and a detection module; The positive terminal of the DC power supply is used to connect the positive terminal of the metallized film capacitor externally. The negative terminal of the metallized film capacitor is grounded; The negative terminal of the DC power supply is grounded; The DC power supply is used to continuously apply voltage to the metallized film capacitor until the capacitance value of the metallized film capacitor reaches different set values, thereby obtaining metallized film capacitors in different operating states. The detection module is used to collect pulse current signals of the metallized film capacitor under different operating conditions.

[0010] Optionally, the detection module includes: a coupling capacitor and a current coil; The positive terminal of the coupling capacitor is connected to the positive terminal of the metallized film capacitor, and the negative terminal of the coupling capacitor is grounded. The current coil is sleeved on the negative terminal of the metallized film capacitor and the negative terminal of the coupling capacitor, and is used to collect the pulse current signal of the metallized film capacitor under different operating conditions. The coupling capacitor is used to isolate the low-frequency DC component in the pulse current signal.

[0011] Optionally, the degradation platform further includes: a protective resistor; One end of the protective resistor is connected to the positive terminal of the DC power supply, and the other end of the protective resistor is used to connect to the positive terminal of the metallized film capacitor.

[0012] Optionally, the output voltage of the DC power supply is greater than the rated voltage of the metallized film capacitor.

[0013] Optionally, the coupling capacitor includes at least one capacitor branch, and the capacitor branches are connected in parallel. Each capacitor branch contains at least one sub-capacitor connected in series.

[0014] Secondly, embodiments of the present invention provide an operating status evaluation device for a metallized film capacitor, comprising: The acquisition module is used to acquire the pulse current signal generated by the metallized film capacitor under test within a set time period during the operation of the metallized film capacitor under test. The calculation module is used to determine, based on the pulse current signal, the number of self-healing discharges of the metallized film capacitor under test within the set time period, the discharge time interval between two adjacent self-healing discharges, and the discharge amount of each self-healing discharge. The evaluation module is used to input the number of self-healing discharges, the discharge time interval, and the discharge amount into a pre-trained state evaluation model to determine the operating state of the metallized film capacitor under test.

[0015] Thirdly, embodiments of the present invention provide an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the method described in the first aspect or any possible implementation thereof.

[0016] Compared to existing technologies, this invention, by acquiring pulse current signals of the metallized film capacitor under test during operation, can determine three types of discharge indicators: the number of self-healing discharges, the self-healing discharge time interval, and the discharge quantity. The number of self-healing discharges is strongly correlated with the density of dielectric defects within the metallized film capacitor; the discharge time interval is strongly correlated with the dielectric insulation strength of the metallized film capacitor; and the discharge quantity is strongly correlated with the size of dielectric defects in the metallized film capacitor. The number of self-healing discharges, the discharge time interval, and the discharge quantity directly reflect microscopic discharge events in the internal dielectric of the metallized film capacitor, representing the earliest stage of degradation. Therefore, this invention enables accurate online assessment of the operating status of metallized film capacitors in the early stages of operational degradation. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the implementation of the method for evaluating the operating status of a metallized film capacitor provided in this embodiment of the invention. Figure 2(a) is a time-domain waveform diagram of the pulse current signal of the metallized film capacitor H-1 in a healthy state provided in an embodiment of the present invention; Figure 2(b) is a frequency domain spectrum of the pulse current signal of the metallized film capacitor H-1 in a healthy state provided in an embodiment of the present invention; Figure 3(a) is a time series diagram of the discharge amount of the metallized film capacitor H-1 in a healthy state according to an embodiment of the present invention. Figure 3(b) is a time series diagram of the discharge amount of the self-healing discharge of the metallized film capacitor Mi-2 in a slightly deteriorated state provided in the embodiment of the present invention; Figure 3(c) is a time series diagram of the discharge amount of the metallized film capacitor E-1 at the end of its lifespan provided in the embodiment of the present invention. Figure 3(d) is a time series diagram of the discharge amount of the metallized film capacitor F-1 in the fault state provided by the embodiment of the present invention. Figure 4(a) is a statistical spectrum of the number of discharges and the discharge time interval of the self-healing discharge of the metallized film capacitor H-1 in a healthy state provided in the embodiment of the present invention. Figure 4(b) is a statistical spectrum of the number of discharges and the time interval of self-healing discharge of the metallized film capacitor Mi-2 in a slightly deteriorated state provided in the embodiment of the present invention. Figure 4(c) is a statistical spectrum of the number of discharges and the discharge time interval of the self-healing discharge of the metallized film capacitor E-1 at the end of its life provided in the embodiment of the present invention. Figure 4(d) is a statistical spectrum of the number of discharges and the time interval of self-healing discharge of the metallized film capacitor F-1 in the fault state provided in the embodiment of the present invention. Figure 5(a) is a statistical spectrum of the discharge amount and discharge time interval of the self-healing discharge of the metallized film capacitor H-1 in a healthy state provided by the embodiment of the present invention. Figure 5(b) is a statistical spectrum of the discharge amount and discharge time interval of the self-healing discharge of the metallized film capacitor Mi-2 in a slightly deteriorated state provided in the embodiment of the present invention. Figure 5(c) is a statistical spectrum of the discharge amount and discharge time interval of the metallized film capacitor E-1 at the end of its life provided by the embodiment of the present invention. Figure 5(d) is a statistical spectrum of the discharge amount and discharge time interval of the metallized film capacitor F-1 in the fault state provided in the embodiment of the present invention. Figure 6(a) is a statistical spectrum of the discharge amount and number of discharges of the metallized film capacitor H-1 in a healthy state provided in the embodiment of the present invention. Figure 6(b) is a statistical spectrum of the discharge amount and number of discharges of the slightly deteriorated metallized film capacitor Mi-2 according to the embodiment of the present invention. Figure 6(c) is a statistical spectrum of the discharge amount and number of discharges of the metallized film capacitor E-1 at the end of its life provided in the embodiment of the present invention. Figure 6(d) is a statistical spectrum of the discharge amount and number of discharges of the metallized film capacitor F-1 in the fault state provided in the embodiment of the present invention. Figure 7 This is a schematic diagram of the structure of the degraded platform provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of the operating status evaluation device for metallized film capacitors provided in an embodiment of the present invention; Figure 9 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0018] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] In related technologies, most methods employ offline or online capacitance measurement to assess the operating status of capacitors. However, for metallized film capacitors encapsulated in MMC (Metallic Metallized Film Capacitor), offline testing and evaluation methods are unsuitable due to the difficulty in disassembling them. Furthermore, online measurement of ripple current to estimate capacitance is susceptible to interference from topological harmonics and load fluctuations, resulting in low accuracy in assessing the early stages of capacitor degradation.

[0020] To achieve accurate online assessment of the operating status of metallized film capacitors, this invention determines three discharge indicators—the number of self-healing discharges, the self-healing discharge time interval, and the discharge amount—by collecting pulse current signals during the operation of the metallized film capacitor. The number of self-healing discharges, the discharge time interval, and the discharge amount directly reflect microscopic discharge events within the internal dielectric of the metallized film capacitor, representing the earliest stage of degradation. By utilizing these indicators, this invention enables accurate online assessment of the operating status of metallized film capacitors in the early stages of degradation.

[0021] See Figure 1 The document illustrates a flowchart of the implementation of the operating status evaluation method for a metallized film capacitor provided in an embodiment of the present invention, which is described in detail below: Step 101: During the operation of the metallized film capacitor under test, the pulse current signal generated by the metallized film capacitor under test within a set time period is collected.

[0022] In this embodiment of the invention, a current coil can be fitted onto the metallized film capacitor under test to collect the pulse current signal generated by the metallized film capacitor within a set time period. The model and specifications of the current coil can be determined according to the actual situation. For example, in this embodiment of the invention, the model of the current coil is AKV 9330.

[0023] Here, the current coil can be connected to a waveform acquisition device (such as an oscilloscope). The waveform acquisition device is configured to record the current waveform signal acquired by the current coil when the real-time current value exceeds a set current value, thus obtaining a pulse current signal. The set current value can be determined based on actual conditions. Essentially, this pulse current signal is the signal spike in the current signal flowing through the metallized film capacitor, used to reflect the self-healing discharge status of the metallized film capacitor.

[0024] This invention provides a brief description of the self-healing discharge of metallized film capacitors: During operation, the internal dielectric of a metallized film capacitor undergoes insulation breakdown. The nanoscale metal plating around the breakdown point evaporates instantaneously, forming an insulating isolation zone. This microsecond-level metal vaporization process produces two key effects: first, it forms a ring-shaped isolation band to prevent further discharge (i.e., self-healing function); second, it releases plasma to generate a pulse current (i.e., the aforementioned pulse current signal). Self-healing discharge is a unique protection mechanism of metallized film capacitors. Each self-healing discharge is accompanied by a detectable pulse current signal.

[0025] The applicant has discovered through research that the self-healing discharge characteristics of metallized film capacitors vary depending on their operating state. Therefore, embodiments of the present invention evaluate the operating state of metallized film capacitors based on their self-healing discharge characteristics.

[0026] This invention classifies the operating states of metallized film capacitors into: healthy state, slightly deteriorated state, moderately deteriorated state, end-of-life state, and fault state. The capacitance value varies depending on the operating state. In the healthy state, the capacitance of the metallized film capacitor is 100%~98%C0; in the slightly deteriorated state, it is 98%~97%C0; in the moderately deteriorated state, it is 97%~96%C0; in the end-of-life state, it is 96%~95%C0; and in the fault state, it is below 95%C0. Here, C0 represents the initial capacitance value of the metallized film capacitor.

[0027] Step 102: Based on the pulse current signal, determine the number of self-healing discharges of the metallized film capacitor under test within a set time period, the discharge time interval between two adjacent self-healing discharges, and the discharge amount of each self-healing discharge.

[0028] The applicant discovered through experiments that the number of self-healing discharges, the discharge time interval, and the discharge amount during the self-healing discharge process of metallized film capacitors change depending on the operating state. The specific experimental process is as follows: Here, metallized film capacitors with a capacitance of 100% C0 are selected as capacitors in healthy condition. Metallized film capacitors with capacitances of 98% C0 and 97.5% C0 are selected as capacitors in slightly deteriorated condition. Metallized film capacitors with a capacitance of 96.5% C0 are selected as capacitors in moderately deteriorated condition. Metallized film capacitors with capacitances of 95.1% C0 and 95% C0 are selected as capacitors in end-of-life condition. Metallized film capacitors with capacitances of 94% C0 and 93.7% C0 are selected as capacitors in failure condition. See Table 1 for details.

[0029] Table 1. Component parameters and condition classification of capacitors

[0030] Referring to Figures 2(a) and 2(b), for a healthy metallized film capacitor H-1, the rise time of its pulse current signal is approximately 2 μs, and the pulse duration is approximately 20 μs. As shown in Figure 2(b), the main components of this pulse current signal are below 400 kHz, with the spectral peak located around 44 kHz. However, as the metallized film capacitor continues to deteriorate, both the pulse current duration and the spectral peak increase significantly and monotonically.

[0031] Secondly, the discharge amount of self-healing discharge of metallized film capacitors under different operating conditions. QThe time series diagrams are shown in Figures 3(a) to 3(d). During the same test period, the metallized film capacitor H-1 in the healthy state had the fewest discharges and the smallest discharge amount. Q The amplitude is 5nC or less. As shown in Figure 3(b), with increasing aging, the number of discharges of the slightly degraded metallized film capacitor Mi-2 increases uniformly, and the amplitude rises slightly, with a maximum value of approximately 10nC. When the metallized film capacitor degrades to the end of its lifespan, as shown in Figure 3(c), the discharge amount of the metallized film capacitor E-1... Q The amplitude increases, with a maximum value between 12 and 15 nC; the metallized film capacitor F-1 under fault conditions, as shown in Figure 3(d), has the densest distribution of discharge points in the initial stage, and the discharge amount is... Q The initial amplitude was relatively high, but the number of discharge points gradually decreased over time, and the discharge amount... Q The amplitude gradually decreases and eventually maintains a stable discharge state.

[0032] Number of self-healing discharges of metallized film capacitors under different operating conditions n With discharge time interval ∆ t The statistical spectra are shown in Figures 4(a) to 4(d). The discharge time interval ∆ of the metallized film capacitor H-1 under healthy conditions. t All intervals are greater than 10 seconds, the spectral lines are relatively sparse, and the number of discharges in each time interval is no more than 3. As the degree of aging increases, when the capacitor value drops to 97.5%C0 (i.e., mildly degraded state Mi-2), as shown in Figure 4(b), the discharge time interval ∆ t The discharge time interval ∆ is significantly shortened, the spectral line distribution range is widened, and the discharge time interval ∆ is significantly shortened. t The discharge time interval extends to 1–139 s, and the spectral lines become denser; when the capacitor capacitance drops to 95.1%C0 (i.e., the end-of-life state E-1), as shown in Figure 4(c), the discharge time interval ∆ t The number of discharges less than 1 second increased significantly, and the spectral peak shifted to the left; when the capacitor capacitance dropped to 94%C0 (i.e., fault state F-1), as shown in Figure 4(d), the discharge time interval ∆ t The number of discharges less than 1 second increased to 21, more than twice the number of discharges in any other time interval.

[0033] Discharge amount of self-healing discharge of metallized film capacitors under different operating conditions Q and discharge time interval ∆ tThe statistical spectra of the metallized film capacitor H-1 in the healthy state are shown in Figures 5(a) to 5(d). As shown in Figure 5(a), the spectral lines in the statistical spectrum of the metallized film capacitor H-1 in the healthy state are sparse and far apart. As shown in Figure 5(b), the spectral lines in the statistical spectrum of the metallized film capacitor Mi-2 in the slightly deteriorated state become denser, and the spectrum begins to show significant peak points. The peak points shift to the left as the degree of aging increases, from 10~100s to less than 10s, and the typical discharge time interval becomes shorter. As shown in Figure 5(c), the spectral lines in the statistical spectrum of the metallized film capacitor E-1 in the end-of-life state are even denser, with discharge points of no more than 0.1s time intervals. At the same time, the difference in discharge time intervals increases, and the coverage of the spectrum time interval along the x-axis becomes larger. The statistical spectrum of the metallized film capacitor F-1 in the fault state is shown in Figure 5(d). Compared with Figure 5(c), the spectrum shifts to the left along the x-axis less, but the difference in the length of the spectral lines corresponding to each discharge time interval becomes larger, and the spectral line differentiation is greater than that of Figure 5(c).

[0034] Discharge amount of self-healing discharge of metallized film capacitors under different operating conditions Q and number of discharges n The statistical spectrum is shown in Figures 6(a) to 6(d). As shown in Figure 6(a), the maximum discharge of capacitor H-1 in the healthy state within 1 hour does not exceed 7nC, and the number of discharges below 1nC is the most, reaching 8 times; as shown in Figure 6(b), the maximum discharge of metallized film capacitor Mi-2 in the slightly deteriorated state increases to 10nC, and the number of discharges between 1 and 2nC is the most, reaching 20 times; as shown in Figure 6(c), the maximum discharge of metallized film capacitor E-1 in the end-of-life state increases sharply, even exceeding 15nC, and the number of discharges between 0 and 4nC increases significantly, and the number of discharges below 1nC increases to 34 times; as shown in Figure 6(d), the maximum discharge of metallized film capacitor F-1 in the fault state is 14nC, and the number of discharges below 1nC is the most, reaching 51 times.

[0035] Based on the above data analysis, it can be seen that as the operating state of the metallized film capacitor changes, the discharge amount, discharge time interval, and discharge number of its self-healing discharge also change significantly. Therefore, this embodiment of the invention utilizes the discharge amount, discharge time interval, and discharge number of the self-healing discharge to evaluate the operating state of the metallized film capacitor.

[0036] The applicant's research has revealed that the discharge amount of self-healing discharge reflects the destructive energy of a single discharge. The magnitude of the discharge amount reflects the size of dielectric defects inside the metallized film capacitor. As the air gap / cracks inside the metallized film capacitor expand (i.e., the defect size increases), the energy released by a single self-healing discharge increases.

[0037] The discharge time interval reflects the continuity of self-healing discharge. The magnitude of the discharge time interval reflects the strength of the dielectric insulation inside the metallized film capacitor. When the dielectric insulation strength inside the metallized film capacitor decreases, it is more easily broken down, resulting in more frequent self-healing discharge and a shorter discharge time interval.

[0038] The number of discharges reflects the density of dielectric defects inside a metallized film capacitor. As the operating condition of a metallized film capacitor deteriorates, the number of self-healing points in the internal metallized film increases, the discharge channel density rises, and consequently, the number of discharges increases.

[0039] The discharge amount, discharge time interval, and discharge number of self-healing discharges can directly reflect the microscopic discharge situation of the internal dielectric of a metallized film capacitor. Therefore, this embodiment of the invention evaluates the operating status of a metallized film capacitor by determining the discharge amount, discharge time interval, and discharge number of self-healing discharges of the metallized film capacitor under test within a set time period.

[0040] Here, there are multiple pulse current signals within the set time period. Each pulse current signal corresponds to one self-healing discharge. The duration of the set time period can be determined according to the actual situation; for example, the set time period can be 1 hour.

[0041] In some embodiments, the number of self-healing discharges can be determined based on the number of pulse current signals. Here, each pulse current signal corresponds to one self-healing discharge. The number of pulse current signals is the number of self-healing discharges.

[0042] In some embodiments, the discharge start time of each pulse current signal can be determined separately, and the discharge time interval between two adjacent self-healing discharges can be determined based on the difference between the discharge start times of two adjacent pulse current signals.

[0043] Here, the rising edge time of each pulse current signal can be sampled and recorded, and the time difference between the rising edges of two adjacent pulse current signals can be determined as the discharge time interval between two adjacent self-healing discharges. In essence, the rising edge time of the pulse current signal is recorded as the discharge start time.

[0044] In some embodiments, each pulse current signal can be integrated to obtain the discharge amount of each self-healing discharge.

[0045] Step 103: Input the number of self-healing discharges, the discharge time interval, and the discharge amount into the pre-trained state evaluation model to determine the operating state of the metallized film capacitor under test.

[0046] Here, the state assessment model can be a neural network model. By training this state assessment model, it can learn the mapping relationship between the number of self-healing discharges, the discharge time interval, and the discharge amount of the metallized film capacitor, and the operating state of the metallized film capacitor, thus obtaining a well-trained state assessment model.

[0047] In some embodiments, metallized film capacitors in different operating states can be prepared using a degradation platform, and pulse current signals of the metallized film capacitors in different operating states can be collected; then, the state evaluation model can be trained using the pulse current signals of the metallized film capacitors in different operating states to obtain the trained state evaluation model.

[0048] Compared to existing technologies, this invention, by acquiring pulse current signals of the metallized film capacitor under test during operation, can determine three types of discharge indicators: the number of self-healing discharges, the self-healing discharge time interval, and the discharge quantity. The number of self-healing discharges is strongly correlated with the density of dielectric defects within the metallized film capacitor; the discharge time interval is strongly correlated with the dielectric insulation strength of the metallized film capacitor; and the discharge quantity is strongly correlated with the size of dielectric defects in the metallized film capacitor. The number of self-healing discharges, the discharge time interval, and the discharge quantity directly reflect microscopic discharge events in the internal dielectric of the metallized film capacitor, representing the earliest stage of degradation. Therefore, this invention enables accurate online assessment of the operating status of metallized film capacitors in the early stages of operational degradation.

[0049] The following section introduces the degradation platform used to prepare metallized film capacitors in different operating states.

[0050] In some embodiments, see Figure 7 The degraded platform includes: DC power supply and detection module.

[0051] The positive terminal of the DC power supply is used to connect the positive terminal of the external metallized film capacitor; the negative terminal of the metallized film capacitor is grounded; the negative terminal of the DC power supply is grounded; the DC power supply is used to continuously apply voltage to the metallized film capacitor until the capacitance value of the metallized film capacitor reaches different set values, thus obtaining metallized film capacitors in different operating states; the detection module is used to collect the pulse current signal of the metallized film capacitor in different operating states.

[0052] Here, the DC power supply is used to continuously apply voltage to the metallized film capacitor, which can accelerate the aging of the dielectric of the metallized film capacitor, simulate long-term operating stress, and rapidly degrade the operating condition of the metallized film capacitor. In order to make the DC power supply effectively degrade the metallized film capacitor, in some embodiments, the output voltage of the DC power supply can be set to be greater than the rated voltage of the metallized film capacitor.

[0053] To ensure that the DC power supply can effectively degrade the metallized film capacitor while avoiding excessive voltage that could burn out the capacitor, the output voltage of the DC power supply can, for example, be 1.5 times the rated voltage of the metallized film capacitor.

[0054] In some embodiments, see Figure 7 The detection module includes a coupling capacitor and a current coil. The positive terminal of the coupling capacitor is connected to the positive terminal of the metallized film capacitor, and the negative terminal is grounded. The current coil is fitted over the negative terminals of both the metallized film capacitor and the coupling capacitor, and is used to acquire the pulse current signal of the metallized film capacitor under different operating conditions. The coupling capacitor is used to isolate the low-frequency DC component in the pulse current signal.

[0055] This invention utilizes the characteristic of coupling capacitors to isolate low-frequency DC components. The coupling capacitor is connected in parallel across the metallized film capacitor, and the current coil is placed between the negative terminals of the metallized film capacitor and the negative terminal of the coupling capacitor to isolate the low-frequency DC components in the pulse current signal and ensure the accuracy of the pulse current signal.

[0056] In some embodiments, the coupling capacitor includes: at least one capacitor branch, wherein each capacitor branch is connected in parallel; and each capacitor branch includes at least one sub-capacitor connected in series.

[0057] The reason for using a series-parallel combination to construct the coupling capacitors is twofold. Firstly, the operating voltage within the MMC submodule is relatively high; a series structure prevents single-capacitor breakdown and eliminates background partial discharge noise caused by concentrated electric fields at the electrode edges of a single capacitor. Secondly, the equivalent resistance of the series-connected capacitors is too high, which can easily lead to attenuation of the pulse current signal. Therefore, the capacitors are connected in parallel to reduce the equivalent series resistance, ensuring that the microsecond-level pulse current passes through without attenuation. For example, see... Figure 7 The coupling capacitor can be constructed using two series and two parallel capacitors.

[0058] In addition, the detection module also includes a coil power supply module, a signal acquisition system, and a data storage device. The coil power supply module supplies power to the aforementioned current coil. The signal acquisition system receives the current waveform signal acquired by the current coil, identifies signal spikes (i.e., pulse current signals) from the current waveform signal, and sends the pulse current signals to the data storage device for storage.

[0059] In some embodiments, the degraded platform further includes: a protection resistor; One end of the protective resistor is connected to the positive terminal of the DC power supply, and the other end of the protective resistor is used to connect to the positive terminal of the metallized film capacitor.

[0060] Here, the protective resistor is used for current limiting protection to prevent short-circuit current from damaging the equipment.

[0061] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0062] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above.

[0063] Figure 8 A schematic diagram of the operating status evaluation device for a metallized film capacitor provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below: like Figure 8 As shown, the operating status evaluation device 8 for metallized film capacitors includes: a data acquisition module 81, a calculation module 82, and an evaluation module 83.

[0064] The acquisition module 81 is used to acquire the pulse current signal generated by the metallized film capacitor under test within a set time period during the operation of the metallized film capacitor under test. The calculation module 82 is used to determine, based on the pulse current signal, the number of self-healing discharges of the metallized film capacitor under test within a set time period, the discharge time interval between two adjacent self-healing discharges, and the discharge amount of each self-healing discharge. Evaluation module 83 is used to input the number of self-healing discharges, the discharge time interval, and the discharge amount into a pre-trained state evaluation model to determine the operating state of the metallized film capacitor under test.

[0065] In one possible implementation, there are multiple pulse current signals; each pulse current signal corresponds to one self-healing discharge. Calculation module 82 is specifically used for: The number of self-healing discharge cycles is determined based on the number of pulse current signals. The discharge start time of each pulse current signal is determined, and the discharge time interval between two adjacent self-healing discharges is determined based on the difference between the discharge start times of two adjacent pulse current signals. Integrating each pulse current signal yields the discharge amount for each self-healing discharge.

[0066] In one possible implementation, the evaluation module 83 is also used for: Metallized film capacitors under different operating conditions were prepared using a degraded platform, and pulse current signals of the metallized film capacitors under different operating conditions were collected. By using the pulse current signals of metallized film capacitors under different operating conditions, a state evaluation model is trained, resulting in a trained state evaluation model.

[0067] In one possible implementation, the degradation platform includes: a DC power supply and a detection module; The positive terminal of the DC power supply is used as the positive terminal of an external metallized film capacitor; The negative terminal of the metallized film capacitor is grounded; The negative terminal of the DC power supply is grounded; A DC power supply is used to continuously apply voltage to the metallized film capacitor until the capacitance value of the metallized film capacitor reaches different set values, thereby obtaining metallized film capacitors in different operating states. The detection module is used to collect pulse current signals of metallized film capacitors under different operating conditions.

[0068] In one possible implementation, the detection module includes: a coupling capacitor and a current coil; The positive terminal of the coupling capacitor is connected to the positive terminal of the metallized film capacitor, and the negative terminal of the coupling capacitor is grounded. A current coil is fitted onto the negative terminal of the metallized film capacitor and the negative terminal of the coupling capacitor to collect the pulse current signal of the metallized film capacitor under different operating conditions. Coupling capacitors are used to isolate the low-frequency DC component in pulse current signals.

[0069] In one possible implementation, the degraded platform also includes: a protection resistor; One end of the protective resistor is connected to the positive terminal of the DC power supply, and the other end of the protective resistor is used to connect to the positive terminal of the metallized film capacitor.

[0070] In one possible implementation, the output voltage of the DC power supply is greater than the rated voltage of the metallized film capacitor.

[0071] In one possible implementation, the coupling capacitor includes at least one capacitor branch, and the capacitor branches are connected in parallel. Each capacitor branch contains at least one sub-capacitor connected in series.

[0072] This device embodiment can be used to implement the above method embodiment, and its technical principle and implementation effect are the same as those of the above method embodiment, so they will not be repeated here.

[0073] Figure 9 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. For example... Figure 9 As shown, the electronic device 9 of this embodiment includes a processor 90 and a memory 91. The memory 91 stores a computer program 92. When the processor 90 executes the computer program 92, it implements the steps in the various method embodiments described above. Alternatively, when the processor 90 executes the computer program 92, it implements the functions of each module / unit in the various device embodiments described above.

[0074] For example, computer program 92 may be divided into one or more modules / units, which are stored in memory 91 and executed by processor 90 to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of computer program 92 in electronic device 9.

[0075] Electronic device 9 may include, but is not limited to, processor 90 and memory 91. Those skilled in the art will understand that... Figure 9 This is merely an example of electronic device 9 and does not constitute a limitation on electronic device 9. It may include more or fewer components than shown, or combine certain components, or different components. For example, electronic device 9 may also include input / output devices, network access devices, buses, etc.

[0076] For the sake of simplicity and clarity, only the above-described functional modules / units are used as examples. In practical applications, the functions described above can be assigned to different functional modules / units as needed. These modules / units can be implemented in hardware, software, or a combination of both.

[0077] In the above embodiments, the descriptions of each embodiment have their own emphasis. Parts not detailed or described in a particular embodiment can be referred to in the relevant descriptions of other embodiments. Unless otherwise specified or in conflict with logic, the terminology and / or descriptions between different embodiments are consistent and can be referenced interchangeably. Technical features in different embodiments can be combined to form new embodiments based on their inherent logical relationships.

[0078] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for evaluating the operating status of a metallized film capacitor, characterized in that, include: During the operation of the metallized film capacitor under test, the pulse current signal generated by the metallized film capacitor under test within a set time period is collected; Based on the pulse current signal, the number of self-healing discharges of the metallized film capacitor under test within the set time period, the discharge time interval between two adjacent self-healing discharges, and the discharge amount of each self-healing discharge are determined. The self-healing discharge count, the discharge time interval, and the discharge amount are input into a pre-trained state evaluation model to determine the operating state of the metallized film capacitor under test.

2. The method for evaluating the operating status of a metallized film capacitor according to claim 1, characterized in that, There are multiple pulse current signals; each pulse current signal corresponds to one self-healing discharge. The step of determining, based on the pulse current signal, the number of self-healing discharges of the metallized film capacitor under test within the set time period, the discharge time interval between two adjacent self-healing discharges, and the discharge amount of each self-healing discharge includes: The number of self-healing discharges is determined based on the number of pulse current signals. The discharge start time of each pulse current signal is determined, and the discharge time interval between two adjacent self-healing discharges is determined based on the difference between the discharge start times of two adjacent pulse current signals. Integrating each pulse current signal yields the discharge amount for each self-healing discharge.

3. The method for evaluating the operating status of a metallized film capacitor according to claim 1 or 2, characterized in that, Before inputting the number of self-healing discharges, the discharge time interval, and the discharge amount into the pre-trained state evaluation model to determine the operating state of the metallized film capacitor under test, the method further includes: Metallized film capacitors under different operating conditions were prepared using a degraded platform, and pulse current signals of the metallized film capacitors under different operating conditions were collected. Using the pulse current signals of the metallized film capacitor under different operating conditions, a state evaluation model is trained to obtain a trained state evaluation model.

4. The method for evaluating the operating status of a metallized film capacitor according to claim 3, characterized in that, The degradation platform includes: a DC power supply and a detection module; The positive terminal of the DC power supply is used to connect the positive terminal of the metallized film capacitor externally. The negative terminal of the metallized film capacitor is grounded; The negative terminal of the DC power supply is grounded; The DC power supply is used to continuously apply voltage to the metallized film capacitor until the capacitance value of the metallized film capacitor reaches different set values, thereby obtaining metallized film capacitors in different operating states. The detection module is used to collect pulse current signals of the metallized film capacitor under different operating conditions.

5. The method for evaluating the operating status of a metallized film capacitor according to claim 4, characterized in that, The detection module includes: a coupling capacitor and a current coil; The positive terminal of the coupling capacitor is connected to the positive terminal of the metallized film capacitor, and the negative terminal of the coupling capacitor is grounded. The current coil is sleeved on the negative terminal of the metallized film capacitor and the negative terminal of the coupling capacitor, and is used to collect the pulse current signal of the metallized film capacitor under different operating conditions. The coupling capacitor is used to isolate the low-frequency DC component in the pulse current signal.

6. The method for evaluating the operating status of a metallized film capacitor according to claim 4, characterized in that, The degradation platform also includes: a protective resistor; One end of the protective resistor is connected to the positive terminal of the DC power supply, and the other end of the protective resistor is used to connect to the positive terminal of the metallized film capacitor.

7. The method for evaluating the operating status of a metallized film capacitor according to claim 4, characterized in that, The output voltage of the DC power supply is greater than the rated voltage of the metallized film capacitor.

8. The method for evaluating the operating status of a metallized film capacitor according to claim 5, characterized in that, The coupling capacitor includes at least one capacitor branch, and the capacitor branches are connected in parallel. Each capacitor branch contains at least one sub-capacitor connected in series.

9. A device for evaluating the operating status of a metallized film capacitor, characterized in that, include: The acquisition module is used to acquire the pulse current signal generated by the metallized film capacitor under test within a set time period during the operation of the metallized film capacitor under test. The calculation module is used to determine, based on the pulse current signal, the number of self-healing discharges of the metallized film capacitor under test within the set time period, the discharge time interval between two adjacent self-healing discharges, and the discharge amount of each self-healing discharge. The evaluation module is used to input the number of self-healing discharges, the discharge time interval, and the discharge amount into a pre-trained state evaluation model to determine the operating state of the metallized film capacitor under test.

10. An electronic device, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the method as described in any one of claims 1 to 8.

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