最新刊期
卷 47 ， 期 4 ， 2026
- 摘要：To evaluate the long-term operating performance and engineering applicability of domestically developed dry-type DC capacitors in flexible DC transmission projects, a systematic investigation was carried out on 20 all-domestic 2.8 kV~9 mF capacitors that had been in continuous service for 1~2 years at the Longmen converter station of the Kunliulong HVDC Transmission Project. The work was organized by the leading project unit and completed on the capacitor evaluation and reliability verification platform of the National Engineering Research Center of UHV Technology and Novel Electrical Equipment Basis. Electrical characteristics, encapsulation condition, and long-term operating reliability of the capacitors were evaluated through whole-unit testing and post-operation disassembly analysis. The results show that the capacitors remained in stable operating condition after long-term field service, with no obvious capacitance degradation and only minor variation in dielectric loss. Good electrical stability and insulation performance were maintained during operation. DC withstand voltage and endurance tests were further conducted on dissected capacitor elements, and all tested samples met the requirements of NB/T 11388—2023. In the endurance test, the operating duration exceeded the 500 h requirement specified in the standard. Further analysis indicates that the domestically developed capacitors can satisfy current engineering application requirements in terms of material compatibility, self-healing behavior, and structural design. Some samples still showed room for improvement in encapsulation consistency and local stress control. Overall, the investigated capacitors demonstrated good operating stability and reliability after field application, providing useful reference for subsequent design improvement, quality evaluation, and engineering application of domestic dry-type DC capacitors in HVDC systems.关键词：DC dry-type capacitor;domestic production;grid-connected operation;withstand voltage characteristics;engineering application34|0|0更新时间：2026-08-26
- 摘要：DC-link capacitors are a bottleneck restricting the development of VSC-HVDC transmission projects, and there is currently no large-scale appliction of domestically developed capacitors in existing operational projects. Multiple types of domestically produced DC-link capacitors that have undergone gridconnected trial operation at a converter stations are subjected to disassembly analysis and test research, defects are identified, process improvements are implemented, and exploration of test scheme optimization is carried out. The results indicate that the maximum capacitance attenuation rate before and after grid connection is-0.24%, with no significant deterioration in electrical performance. Disassembly and experimental analysis reveals such four typical types of defects as abnormal withstand voltage level of the elements, improper control of potting compound dosage, delamination between the encapsulation shell and the polyurethane, as well as the presence of bubbles within the polyurethane. Accordingly, such corresponding improvement measures as staggered design of the metallized film transition zone, capacitive liquid-level sensing for potting compound monitoring, surface micro-texturing of the encapsulation shell, and precise control of vacuum degassing parameters are proposed. To address the issue that conventional parameters can hardly reflect the aging degree of DC-link capacitors, it is proposed that the capacitance variation curve during the step voltage withstand test can effectively characterize the early aging degree of capacitors. Through the state analysis, process improvements, and test scheme optimization after grid-connected operation, the reliability of the domestically produced DC-link capacitors has been enhanced, proving the feasibility of replacing imported products.关键词：DC-link capacitor;domestically produced;grid-connected trial operation;disassembly analysis;process improvement9|0|0更新时间：2026-08-26
- 摘要：In this paper, the influence of such basic performance parameters of polyurethane (PU) adhesives as dielectric constant, conductivity, and tangent of loss angle on the AC partial discharge performance of DC-link capacitors to the case is analyzed. The influence of temperature on the curing reaction of polyurethane and the effect of residual uncured rubber are also analyzed. The problem of incomplete reaction of functional groups in PU main agent is analyzed. The influence of the vacuum degree of injection on the partial discharge of the capacitor is calculated in combination with the Paschen's law. Such three curing processes of two-component PU adhesives for DC-link capacitors as high-temperature curing, normal temperature curing, and mixed curing and their influence on the performance of PU adhesives are described. The influence mechanism of the changes in the basic performance parameters of PU on the stability of capacitor partial discharge and the influence mechanism of temperature on DC-link capacitors are obtained. It is concluded that the lower the curing temperature of PU, the worse the uniformity of PU curing, and consequently the worse the case partial discharge performance and its stability. It is inferred that the higher the vacuum pressure during potting, the higher the breakdown field strength of micro-voids. The the suggestion that the basic performance parameters of PU should not exhibit abrupt changes is proposed.关键词：polyurethane;DC-link capacitor;partial discharge;Paschen's law;curing reaction13|0|0更新时间：2026-08-26
- 摘要：VSC-HVDC-link capacitors are key energy storage components in sub-modules of modular multilevel converters (MMC), and their equivalent series inductance (ESL) directly affects the system's switching overvoltage and reliability. In this paper, the planar single-cell core arrangement structure is taken as the study object and a integrated inductance simulation model using COMSOL Multiphysics is set up. The influence of such five key parameters as element diameter (number of parallel elements), copper plate thickness, film width, electrode configuration, and length-to-height ratio on the overall ESL is systematically investigated. The study results show that the electrode system is the absolutely dominant factor in the overall ESL, contributing 97.1%~98.3%, while the contribution of the components themselves is less than 3%. The element diameter has a relatively minor effect (with increase of 6.6%). When the copper plate thickness is increased from 0.4mm to 2.0 mm, the ELS is decreased by only 0.19%, indicating that the effect of the copper plate thickness is not significant. The ELS is decreased by 44.5 when the film width is reduced from 150 mm to 60 mm. The copper strip with braided wire configurations exhibits an ESL 1.20~1.63 times higher than that of the solid copper plates. Moreover, increasing the aspect ratio ( L/H) from 0.62 to 2.57 yields, an ESL reduction of about 75.7%. The short circuit discharge method is used to experimentally validate five typical samples. The maximum relative error between simulations and measurement does not exceed 5.0%, which verifies the effectiveness of the model and provides a systematic quantitative basis for the optimal design of low inductance DC-link capacitors关键词：VSC-HVDC transmission;DC-link capacitors;equivalent series inductance(ESL);systemlevel simulation;parametric scanning;COMSOL simulation10|0|0更新时间：2026-08-26
- 摘要：Temperature rise performance is crucial for capacitors, as the level of temperature rise directly affects their service life. In order to reduce the temperature rise of DC-link capacitor for VSC-HVDC converter valves (referred to as VSC HVDC capacitor), the influencing factors and their regularities affecting the temperature rise of such capacitors are investigated. It is found through analysis of experimental data that numerous factors influence capacitor temperature rise, covering almost every aspect of the capacitors. To reduce the temperature rise of VSC HVDC capacitors, improvements and optimizations shall be carried out in multiple aspects. In terms of materials, it is recommended to select PP dielectric with low loss, choose copper with low resistivity for the conductors, and, on the premise of ensuring the insulation performance between the electrode and the case, select polyurethane with as high thermal conductivity as possible. In terms of design, it is recommended that the width of the low-sheet-resistance zone of the metallized film account for 20% to 30% of the total film width. The individual winding core shall not be excessively large, with its diameter being preferably controlled within the range of 68 to 78 mm. The current density of the copper strip is suggested to be no more than 1.5 A/mm2. In terms of processing, the cleanliness of the winding workshop shall be at least Class 10 000, the spraying pressure shall be controlled between 0.3 MPa and 0.4 MPa. The constant-temperature automated welding is recommended for soldering, and vacuum impregnation with a vacuum level below 100 Pa is preferred for the filling process. In terms of testing, the tests shall be conducted under conditions as close as possible to actual operating conditions, so as to eliminate interfering factors that may affect the temperature rise test results and to obtain the most accurate possible test results.关键词：VSC HVDC capacitors;temperature rise;life time;current density;material;process;design;testing4|0|0更新时间：2026-08-26
- 摘要：Based on the principle that the amount of heat absorbed or released by a capacitor due to temperature rise or fall is identical under different atmospheric pressures, this paper establishes that the heat dissipation coefficient of the capacitor case and the steady-state time remains constant across varying altitudes. Accordingly, a verification experiment is designed to measure the heating and cooling processes of the capacitor at different altitudes. According to the experimental data, the heat dissipation coefficient of the capacitor to the surrounding air during the temperature rise process is obtained at altitude of 5 000 m, which is decreased by 28% compared to that at normal pressure. The heat dissipation coefficient during the temperature drop process is decreased by 25% compared to that at normal pressure. The conclusion through derivation in this paper that the difference in temperature rise of the hottest point of the capacitor and the temperature rise of the container is equal under normal pressure and high altitude, is obtained. The experimental data confirm that the above conclusion is valid. At the atmospheric pressure corresponding to an altitude of 5 000 m, both the capacitor case temperature rises and the hot-spot temperature rise is increased by 2.8 K. The experimental results also indicate that the lower the ambient pressure, the longer the tiem required for the capacitor to reach thermal stability.关键词：high altitude;DC-link capacitor;coefficient of heat dissipation;temperature stability time;Thermal resistance3|0|0更新时间：2026-08-26
- 摘要：As a critical quality indicator for metallized film capacitors, how to effectively realize the self-healing performance evaluation of capacitor components through various test methods and screen qualified capacitor components to the greatest extent is the most concerned problem of capacitor manufacturers. In this paper, the effective analysis of the self-healtign number is achieved in combination with the actual production demand and also through electrical measurement method. The quantitative self-healing characteristic parameters are proposed from different dimensions, and the quantitative assessment analysis is performed. The quantitative indicators of different dimensions are determined as the quality evaluation basis of the full inspection strategy of capacitor components.关键词：self healing characteristics;effectiveness analysis;quantitative assessment5|0|0更新时间：2026-08-26
- 摘要：In this paper, the experimental verification on circular components fabricated from metallized films of the sme specifications from manufactuers X and manufacturer Y under identical process is performed, finding that the components prepared with materials from the former Manufactirer are more prone to the“film burst”phenomenon. Ultimately, it is confirmed that the“film burst”phenomenon has a certain correlation with the film drawing and coating processes. The“film burst”phenomenon is actually the edge surface breakdown occurring in the retained margin on the outlayer of the metallized film of the circular component. The mechanism of this edge surface breakdown in the retained margin is analyzed. First, the severe electric field distortion at the edge of the middle reserved edge plate leads to discharge at low voltages, which increases the risk of surface breakdown. Then, both the roughness of the surface of the base film of the middle reserved edge and the degree of surface contamination will also directly affect the surface breakdown field strength of the middle reserved edge. To address the“film burst”phenomenon, such improvement measures as increasing the width of the middle reserved edge, optimizing the evaporation process, adjusting the polarity and intensity of the corona surface, and optimizing the shielding oil brushing process as well as reducing the non-uniformity of the shielding oil brushing are proposed so to reduce the probability of surface flashover and improve the quality of the metallized film further. The former manufacturer has effectively suppressed the occurrence of surface flashover at the middle reserved edge of components by optimizing the process for films of a certain specification and thickness.关键词：metallized films;coating processes;circular components;central reserved area;film burst;surface breakdown26|0|0更新时间：2026-08-26
- 摘要：High-voltage oil-immersed capacitors are widely used in important applications such as reactive power compensation and filtering. They withstand high voltages during operation, and the surface micromorphology of the polypropylene film has a significant influence on the internal electric field distribution of the capacitor element. This paper focuses on the influence of surface roughness, which has been neglected in previous electric field calculations. Considering the coexistence of metal foils, insulating oil, and roughened polypropylene films within a capacitor element, a calculation model for the internal electric field distribution is established. The influence of film surface roughness on the internal electric field distribution is studied. The protrusions and depressions on the surface of the roughened film can cause electric field distortion and lead to localized field concentration. As the oil gap increases, the relative electric field intensity at the characteristic points in the film and oil at depressions gradually decreases. The rougher the surface, the greater the electric field distortion. The influence of film thickness on the relative electric field intensity is relatively small. Under AC electric field, the higher the relative dielectric constant of oil, the larger the non-uniform degree of electric field. Under DC electric field, the lower the oil conductivity, the higher the relative field intensity in the film and oil at protrusions, and the lower the relative field intensity in the film and oil at depressions. Based on the results of this study, subsequent optimization of capacitor element design methods can be conducted.关键词：Oil-Immersed capacitor;capacitor elements;polypropylene film;film roughness;electric field characteristics18|0|0更新时间：2026-08-26
- 摘要：Film capacitors are core equipment in fields such as VSC-HVDC transmission and renewable energy grid integration, undertaking such critical functionsas voltage stabilization support, DC filtering and reactive power compensation. At present, high-end DC dry-type capacitors and high-performance polypropylene (PP) dielectric films in core application scenarios still rely predominantly on imports. Foreign enterprises have established systemic technological barriers in material formulation, film processing, and equipment manufacturing, which constrain the development of a self-controllable supply chain for power equipment in China. High-temperature energy storage performance is one of the main gaps between the domestic polypropylene (PP) films and advanced foreign products. At elevated temperatures, the intensified thermal motion of PP molecular chain segments and the significantly enhanced transport of thermally activated charge carriers lead to increased conduction loss and reduced breakdown strength. In this paper, the recent progress of such three modification strategies as nanocomposite modification, all-organic composite modification and surface modification is systematically reviewed. Emphasis is placed on the systematic analysis of the entire process of carrier generation, migration, and recombination, aiming to reveal the hightemperature modulation mechanisms of various modification strategies and their corresponding structureperformance correlations with energy storage properties. Considering the national demand for localization, this paper identifies the prevailing scientific bottlenecks and technical hurdles, providing a scientific foundation for addressing the high-temperature performance deficiences of PP films and for supporting the independent and controllable development of the power equipment industry.关键词：polypropylene;high-temperature energy storage performance;carrier transport;conduction loss;film capacitor17|0|0更新时间：2026-08-26
- 摘要：In response to the dependence on imported polypropylene pellets for roughened films in oil-immersed high-voltage capacitors, in this study the roughened films derived from such three pellet categories as purely imported, composite, and purely domestic from two manufacturers are taken as the study object. A comprehensive array of comparative tests, covering physicochemical properties, electrical behavior, and multi-dimensional characteristics of the finished capacitors, is performed. The roughness, crystallinity, mechanical properties and thermal shrinkage of the films are tested and analyzed. The 50-point electrode method, component tests and model capacitor tests are adopted to assess the electrical characteristics and, at the same time, tests including dielectric loss, thermal stability and accelerated aging are performed on finished products. The results show that the pure domestic pellets have deeper roughened grooves, larger dispersion of electrical properties, lower breakdown field strength, noncompliance of dielectric loss at high temperature and insufficient service life under accelerated aging. In contrast, the films made of composite pellets are close to those made of imported pellets in terms of microscopic morphology, physical and chemical properties, electrical stability and aging resistance, with all indicators meeting relevant standards. It is verified by the study that the composite pellet roughened films can replace imported materials for practical application. For pure domestic pellet films, it is necessary to optimize raw materials and film-making processes as well as reduce the design field strength to improve operational reliability. The study results can provide a reference for the popularization and application of domestic polypropylene roughened films in high-voltage capacitors.关键词：oil-immersed high-voltage capacitor;polypropylene roughened film;domestic pellet;composite pellet;electrical property;accelerated aging6|0|0更新时间：2026-08-26
- 摘要：The performance of biaxially oriented polypropylene film for capacitor applications is closely related to the crystalline structure of the resin. Six types of polypropylene resins specifically designed for film capacitors, sourced from both domestic and international manufacturers, are selected. Sheet samples are prepared by hot compression molding. The crystal form, degree of crystallinity, crystalline and amorphous layer thicknesses, melting temperature, and crystallization temperature are characterized by wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC). In addition, the tensile properties of the samples are measured. The results show that four imported resins exhibit β-phase crystals. HPT has the highest β-phase content up to 25.7%, along with the highest crystallinity and the largest lamellar thickness. HC330BF possesses the highest crystallization temperature and relatively high crystallinity. HPT and HC 330BF show rather high crystallization ability and can be applied in capacitor film production. While, SF263 shows significantly lower crystallinity, tensile strength and break elongation than other types, which is not recommended for the production of capacitor film. Neither FC03 nor FC03R resins contain β -phase crystals. FC03 shows higher crystallinity and smaller amorphous region than FC03R, which is attributed to the low isotacticity. Moreover, the molecular weight and molecular weight distribution of FC03 and FC03R also influence crystallinity and crystal size. The domestic FC03 and FC03R resins exhibit higher tensile strength and elongation at break than the imported ones.关键词：capacitor film;polypropylene resin;crystalline structure;crystallization behavior;β-phase4|0|0更新时间：2026-08-26
- 摘要：Electrical-grade ultra-high pure polypropylene resin is the base material used for manufacturing metallized films for dry-type DC capacitors and roughened films for oil-impregnated capacitors. Due to difficulty of downstream film-forming processing, high stability requirements and special nature of the end-use applications, the resin is subejct to extremely stringent requirements on key physical property indicators such as ash content, isotactic index, molecular weight distribution and extractables. Polypropylene products produced by conventional catalyst systems generally have an ash content of ≥200 ppm, far exceeding the upper limit of 30 ppm requirement for ultra-pure polypropylene. At the same time, due to the different application scenarios, the isotactic index varies considerably, making precise control difficult to achieve. Therefore, the imported products are generally produced using the“ slurry polymerization+washing and de-ashing“process rute (abbreviated as the“two-step method”). Domestic products, on the other hand, are produced directly by polymerization on ST-Ⅱdouble-loop polypropylene process units, using highly active main catalysts, without the need for additional“washingand de-ashing”or“active removal”steps (abbreviated as the“one-step method”). Due to the different process routes, there are certain differences in technical and economic indicators such as product structure, oligomer content, processing window, as well as unit operating costs, material consumption, and energy consumption.关键词：high activity;ash content;isotactic index;molecular weight distribution;oligomer5|0|0更新时间：2026-08-26
- 摘要：Dry-type DC-link capacitors are core components in VSC-HVDC transmission systems. The winding quality of capacitor elements directly determines the electrical performance and long-term operational reliability of the products. In view of the winding process adaptability issues arising from the mechanical strength discrepancies between metallized polypropylene films made from domestic and imported resins, a two-dimensional axisymmetric finite element model of the cylindrical capacitor element winding process is established using the ANSYS platform. The regional layering technique is adopted to optimize the trade-off between computational efficiency and simulation fidelity. The stress behavior, deformation patterns, and interlaminar pressure distributions of the two film types are systematically compared under three constant winding tension levels—8 N, 10 N, and 13 N. In this study, the film prepared from domestic granule (Sinopec Zhongyuan Petrochemical FC03R) is denoted as Resin A, and the film prepared from imported granule (Borealis HC300BF) is denoted as Resin B. The study results show that the longitudinal elastic modulus of Resin A is 19.3%lower than that of Resin B. As a consequence, the maximum equivalent stress in the base layer of Resin A is 1.72% lower, and the maximum radial deformation is 1.18% lower than those of Resin B. In addition, the inter-layer pressure exhibits significant layered characteristics, with notable differences observed in the pressure distribution of the outer layers.Resin A has a smaller strength reserve, leading to a higher risk of film rupture and a narrower winding process window compared to resin B. The simulation findings are further validated through accelerated aging tests under different winding tensions, revealing that a moderate winding tension enables domestically produced film elements to achieve optimal capacitance stability. The research results provide quantitative theoretical support for the optimization of winding process parameters for domestic resin films.关键词：resin;biaxially oriented polypropylene film;DC-link capacitor;winding process;finite element simulation;mechanical response4|0|0更新时间：2026-08-26
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