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Non-solid aluminum electrolytic capacitors are one type of reliability-critical components, and they are widely adopted in power electronic converters. The capacitance and equivalent series resistance of these components have significant effects on the performance and reliability of power electronic systems. In this work, by exploring the electrochemical principles of aluminum electrolytic capacitors, the fractional-order (FO) characteristics of the capacitors are revealed, according to which the frequency-dependent parameters of this kind of components are expressed by FO models, while the parameters of the models are estimated by a multi-objective optimization algorithm. Under the same conditions such as the number of arguments supplied and optimization algorithm, the proposed models perform better. Additionally, to show further applications of fractional techniques, a brief example on the output ripple analysis of DC–DC converters is offered, in which one of the proposed FO models of the capacitor is adopted. The effectiveness and superiority of the techniques for predicting the states of the converters are confirmed by comparison with traditional models.

PurposeAluminum electrolytic capacitors (AECs) are a type of indispensable electronic components in modern electronic and electrical products. They are designed and manufactured by a series of product specifications to meet the requirements of a variety of application scenarios. Efficient assessment of the potential environmental impact on AECs with different specification parameters in the product family is essential to implement sustainable product development for the manufacturers.MethodsA cradle-to-gate life cycle assessment (LCA) was performed to evaluate the environmental impact of 38 types of AECs in a product family from the manufacturer’s perspective. In the study, 100,000 AECs with specific rated working voltage (among 16 V, 25 V, and 35 V) and rated capacitance (among 4.7 to 6800 μF) produced by a capacitor manufacturer from Nantong, China, were selected as the functional unit. In the life cycle inventory (LCI) analysis, a parametric LCI model for the product family was established by combining product family parameterization and production process parameterization. The impact assessment method, ReCiPe2016 (midpoint, hierarchist perspective), was used to quantitatively calculate the potential environmental impacts of the AECs.Results and discussionBased on the generated LCIs of the AECs and ReCiPe2016, fossil depletion, climate change, and terrestrial ecotoxicity were identified as the key environmental impact categories in the production stage for the AEC product family. The environmental impacts of fossil consumption, climate change, and terrestrial ecotoxicity per functional unit ranged from 263 to 6777 kg oil equivalent, 884 to 23,760 kg CO2 equivalent, and 573 to 47,340 kg 1,4-DB equivalent, respectively. The environmental impact differences among the product family due to the differences in AECs’ specifications were compared. Aluminum ingots (anode), aluminum ingots (cathode), case, and electricity are the main contributors to the environmental impacts, accounting for over 85% of carbon emissions, over 70% of fossil consumption, and over 62% of terrestrial ecotoxicity. Sensitivity analysis of 12 parameters was investigated.ConclusionsThe results and the conclusions provide a solid foundation for capacitor manufacturers to carry out eco-design development, environmental management, and green marketing. The effect of eco-design optimization and process improvement of the AECs can be quantitatively compared through the established model. Furthermore, the study supports the application and promotion of the AEC eco-label with specific specifications in the AEC industry. The methodology also gives guidance for the LCA studies of product families of other electronic and electrical components.

In recent years, significant technological advances have emerged in renewable power generation systems (RPGS), making them more economical and competitive. On the other hand, for the RPGS to achieve the highest level of performance possible, it is important to ensure the healthy operation of their main building blocks. Power electronic converters (PEC), which are one of the main building blocks of RPGS, have some vulnerable components, such as capacitors, which are responsible for more than a quarter of the failures in these converters. Therefore, it is of paramount importance that the design of fault diagnosis techniques (FDT) assess the capacitor’s state of health so that it is possible to implement predictive and preventive maintenance plans in order to reduce unexpected stoppage of these systems. One of the most commonly used capacitors in power converters is the aluminum electrolytic capacitor (AEC) whose aging manifests itself through an increase in its equivalent series resistance (ESR). Several advanced intelligent techniques have been proposed for assessing AEC health status, many of which require the use of a current sensor in the capacitor branch. However, the introduction of a current sensor in the capacitor branch imposes practical restrictions; in addition, it introduces unwanted resistive and inductive effects. This paper presents an FDT based on the random forest classifier (RFC), which triggers an alert mechanism when the DC-link AEC reaches its ESR threshold value. The great advantage of the proposed solution is that it is non-invasive; therefore, it is not necessary to introduce any sensor inside the converter. The validation of the proposed FDT will be carried out using several computer simulations carried out in Matlab/Simulink.

Sintered foils are currently being considered as a promising material for anode foils in capacitors due to their high specific capacitance and anti-buckling performance, which meet the requirements for capacitor winding. In this article, sintered foils with added starch were produced using a protective atmosphere sintering process. The effect of starch addition in the range of 0–50 vol% on the specific capacitance and anti-buckling performance of the sintered foils was evaluated. Scanning electron microscope (SEM) analysis confirmed the formation of the pores in the sintered foils due to the addition of starch. These pores play a crucial role in improving the specific capacitance and enhancing the anti-buckling performance of the sintered foils. However, excessive amounts of starch can have a negative impact on the specific capacitance of the sintered foils which initially decreased, then increased, and finally decreased with increasing starch content. On the other hand, the anti-buckling performance increased with increasing starch content. At 30 vol% starch addition, a high specific capacitance of 0.886 μF/cm2 and an anti-buckling performance of more than 120 times were obtained, meeting the requirements for anode foils in aluminum electrolytic capacitors. The specific capacitance of the sintered foils was predicted using the close-packed packing model, which can help establish a powder metallurgy method for preparing anode foil materials with high specific capacitance and anti-buckling performance for aluminum electrolytic capacitors.

Nb was electrodeposited on etched aluminum foils for an Al electrolytic capacitor. After annealing at 500°C in air, the foils were anodized in H3BO4 solution at 530 V to form Nb2O5-Al2O3 composite anodic oxide film as a dielectric layer. The voltage–time variations during the anodization process were monitored. The structure, composition, and electrical properties of the anodized foils were investigated by scanning electron microscopy, transmission electron microscopy, x-ray diffraction and electrochemical impedance spectroscopy. The obtained foils were assembled into aluminum electrolytic capacitors, and the capacitor performance was tested according to the Japanese Nichicon standard. It was found that after electrodeposition and annealing, the slope of the voltage–time curve of the aluminum foil became steeper during the anodization process. The composite anodic oxide film showed a triple-layer structure consisting of Nb2O5/Al-NbOx/Al2O3 layers. The specific capacitance (C and Cox) of the composite anodic film was about 14% greater than that of the aluminum anodic oxide film. However, the leakage current (I) of the composite film was increased and its specific resistance (Rox) and withstanding voltage (Uw) decreased relative to the aluminum anodic oxide film, probably due to the greater number of intrinsic defects. During the load life and shelf life test, the composite anodic oxide film demonstrated capacitor performance similar to that of the aluminum anodic film, and can thus be used as a dielectric layer for capacitors to enhance specific capacitance.

The anode foil is a critical component of aluminium electrolytic capacitors, with its performance directly impacting the overall quality of the capacitors. Currently, sintered anode foil with excellent bending resistance and high specific capacitance is considered an ideal material for capacitor manufacturing; however, research on its optimal sintering parameters remains insufficient. In this study, a three-dimensional temperature field model is developed within the Comsol Multiphysics (6.0) environment, accounting for the temperature dependence of aluminium. By varying laser power and scanning speed, the temperature distribution along the laser scanning trajectory is determined, facilitating the identification of optimal process parameters for laser sintering anode foils in electrolytic capacitors. Subsequent laser sintering experiments validate the accuracy of these parameters. The findings indicate that the peak temperature of the molten pool rises with increased laser power and decreased scanning speed. The optimal process parameters for laser sintering anode foils in electrolytic capacitors are a powder layer thickness of 50 μm, a laser power of 140 W, and a scanning speed of 0.05 m s −1 . The specific capacitance of laser-sintered anode foil, formed at voltages of 375 V and 520 V, ranges from 0.847 to 1.157 μF cm −2 and 0.717 to 0.935 μF cm −2 , respectively, when the particle size is between 3 and 4 μm. A specific capacitance of 0.733 μF cm −2 can be achieved, which meets the performance requirements for aluminium electrolytic capacitors.

The service life of aluminium electrolytic capacitors is becoming a critical design factor in power supplies. Despite rising power density demands, electrolytic capacitors and switching devices are the two most common parts of the power supply that age (deteriorate) under normal and diverse working conditions. This study presents a fault diagnostics framework integrated with long-term frequency for a switched-mode power supply aluminium electrolytic capacitor (SMPS-AEC). Long-term frequency condition monitoring (CM) was achieved using the advanced HIOKI LCR meter at 8 MHz. The data acquired during the experimental study can help to achieve the needed paradigm from various measured characteristics of the SMPS/power converter component to detect anomalies between the capacitors selected for analysis. The CM procedure in this study was bound by the electrical parameters—capacitance (Cs), equivalent series resistance (ESR), dissipation factor (DF), and impedance (Z)—-acting as degradation techniques during physical and chemical changes of the capacitors. Furthermore, the proposed methodology was carried out using statistical feature extraction and filter-based correlation for feature selection, followed by training, testing and validation using the selected supervised learning algorithms. The resulting assessment revealed that with increased data capacity, an improved performance was achieved across the chosen algorithms out of which the k-nearest neighbors (KNN) had the best average accuracy (98.40%) and lowest computational cost (0.31 s) across all the electrical parameters. Further assessment was carried out using the fault visualization aided by principal component analysis (PCA) to validate and decide on the best electrical parameters for the CM technique.

The remote prognostic, diagnosis, and maintenance of electrolytic capacitors are research topics of interest due to their presence in numerous electronic devices and their increased susceptibility to degradation over time. The authors’ focus in this article is on the proposal of a new diagram for monitoring the parameters of the capacitors that compose the filter bank of a DC–DC buck converter by connecting them in parallel. Each capacitor is modeled by an equivalent series R–C circuit composed of an equivalent capacitance and an equivalent series resistance (ESR). The method used allows successive investigation of the three capacitors that compose the bank by triggering discharge/charge sequences, acquiring the voltages at the capacitor terminals, and estimating the time constants of each capacitor using a parameter observer. During the estimation of the parameters of a capacitor, the converter uses the other two capacitors maintained in operation. The monitoring cycle of all capacitors of the bank lasts less than 40 ms, not significantly affecting the operation of the converter. The study undertaken is correlated with the thermal map of the board on which the converter is made. The dispersion of the measured values of the equivalent capacitances is below 0.25%, and of the ESR below 2.6%. The major advantage of the method is that the monitoring is performed online and in real time.

DC bus electrolytic capacitors influential on the life of Switched reluctance motor (SRM) due to their chemical properties. For the drive system without electrolytic capacitor SRM, the power decoupling type without electrolytic capacitor scheme is studied. The parallel bidirectional Buck/Boost compensation circuit is a power decoupling circuit, a feed-forward control strategy for output voltage fluctuations of the electrolytic capacitor PFC circuit. The inverter side uses the voltage hysteresis control to stabilize the DC bus voltage. During the two-phase adjacent commutation period, the measured DC bus voltage is compared with two predetermined high and low voltages, make the DC bus voltage fluctuate within a certain range. The effectiveness of the control strategy is verified by electrical tools. The grid-side power factor is 0.958, and the grid current harmonics meet the EN61000-3-2 standard.

This research article aims to improve the specific capacitance of DC-etched Al foil for Al electrolytic capacitors by forming an Al2O3-TiO2 composite anodic oxide film. DC-etched Al foils for aluminum electrolytic capacitors were immersed in a TiO2 precursor sol, followed by calcination and anodizing to manufacture a TiO2-Al2O3 composite anodic oxide film. TiO2 precursor sol–gel particles after calcination were analyzed by XRD. During anodization, the anode potential with time was measured by a digital meter. A scanning electron microscope, electrochemical impedance measurements, and a general digital LCR meter were adopted to explore the microstructure and property of the anodic oxide films. The specific capacitance for the TiO2-Al2O3 composite anodic oxide film and a pure Al anodic one is 3.013 μF/cm2 and 2.435 μF/cm2 at C60V, respectively. The thickness is 87.26 nm for the former and 177.65 nm for the latter. The results show that the TiO2-Al2O3 composite anodic oxide film is about 51% thinner than the single Al anodic film, accounting for a large improvement in specific capacitance. The formation efficiency of the pretreated sample is much higher than that of the blank sample, owing to the pre-deposited TiO2 layer and thermal Al oxide layer. However, the composite anodic oxide film’s specific resistance was reduced and its dielectric loss was also aggravated, resulting from the doping-introduced structural defects.