|
|
|
| Insulation Degradation Properties of BOPP Films for Dry-Type DC Capacitors under Long-Term Electrical-Thermal-Force Action |
| Li Zhuohan1, Chen Xiangrong1, Song Jiale1, Xu Shuang2, Li Xiaojun2 |
1. College of Electrical Engineering Zhejiang University Hangzhou 310027 China;
2. Ningbo Jiangbei Gofront Herong Electric Co. Ltd Ningbo 315033 China |
|
|
|
Abstract Dry-type DC capacitors using biaxially oriented polypropylene (BOPP) films as dielectric media serve as core components in flexible DC converter valves, playing critical roles in maintaining voltage stability and filtering harmonics. However, under actual operating conditions, prolonged exposure to combined electrical-thermal-mechanical stresses leads to performance degradation and even insulation breakdown of the polypropylene film, seriously threatening the stability and reliability of the conversion valves. To investigate the degradation law of the insulation properties of BOPP films under long-term electro-thermal-mechanical multi-physical field aging, this study independently constructed a multi-physical field aging test platform. BOPP films with a thickness of 5.8 μm, produced by Ningbo Great Southeast Wanxiang Science & Technology Co.Ltd, were selected and subjected to aging treatments under varying electric fields, temperatures, and mechanical tensile force for durations of 7, 15, and 30 days. differential scanning calorimetry (DSC), gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), and DC breakdown tests were conducted to analyze the effects of electric field gradient, temperature gradient, mechanical tension gradient, and aging time on the degradation law of the insulation properties of BOPP films.
The results show that BOPP films undergo recrystallization under thermal field and the aging temperature shows a positive correlation with crystallinity and lamellar thickness, while showing a negative correlation with molecular weight and DC breakdown strength. With the increase of aging electric field, the crystallinity of the film increases, the molecular weight and the DC breakdown strength decrease. The effect of mechanical tension on the breakdown strength of BOPP films exhibits a threshold effect. Specifically, when the mechanical tension is lower than the threshold level, the polypropylene molecular chains orient and arrange along the direction of tension, leading to increased crystallinity and molecular weight, thus enhancing DC breakdown strength. However, excessively high tension will cause damage to the molecular chain structure of the films, resulting in reduced molecular weight and decreased breakdown strength. With the extension of aging time, the crystallinity and lamellar thickness of the film increase, while the molecular weight and breakdown strength decrease. Among all samples, the 150-80-10-30 sample exhibits the lowest DC breakdown strength of 466.09 kV/mm, which is 27.9% and 11.5% lower than that of the Ref sample and 150-80-10-7 sample, respectively.
Finally, based on the above test results, a degradation model for the breakdown strength of BOPP films considering the long-term action of electro-thermal-mechanical multi-physical fields was proposed. Due to the large number of parameters to be solved, a two-stage parameter estimation algorithm was employed for iterative optimization. Firstly, the Levenberg-Marquardt algorithm was adopted for preliminary fitting to obtain reasonable initial values of core parameters. Next, the algorithm was extended to the complete model: inheriting the initial parameter values from the previous step, adding tension, coupling terms, and time terms, and using the particle swarm optimization (PSO) algorithm for global optimization to obtain the optimal model parameter values. The model results indicate that the calculated results are in good agreement with the experimental results, with deviations all within 5%. This degradation model can provide a reference for predicting the breakdown strength of BOPP films under different aging electric fields, temperatures, mechanical tensions and aging times.
|
|
Received: 04 July 2025
|
|
|
|
|
|
[1] 饶宏, 黄伟煌, 郭知非, 等. 柔性直流输电技术在大电网中的应用与实践[J]. 高电压技术, 2022, 48(9): 3347-3355.
Rao Hong, Huang Weihuang, Guo Zhifei, et al.Practical experience of VSC-HVDC transmission in large grid[J]. High Voltage Engineering, 2022, 48(9): 3347-3355.
[2] 刘欣, 袁易, 王利桐, 等. 柔性直流输电系统三端口混合参数建模及其稳定性分析[J]. 电工技术学报, 2024, 39(16): 4968-4984.
Liu Xin, Yuan Yi, Wang Litong, et al.Three-port hybrid parameter modeling and stability analysis of MMC-HVDC system[J]. Transactions of China Electrotechnical Society, 2024, 39(16): 4968-4984.
[3] He Jinghan, Nie Ming, Li Meng, et al.Dynamic state estimation based protection for flexible DC grid[J]. IEEE Transactions on Industrial Electronics, 2023, 70(3): 3069-3079.
[4] 张午宇, 齐磊, 张翔宇, 等. 计及金属化薄膜电容器与IGBT模块退化过程相关性的柔直换流阀组件可靠性评估方法[J]. 电工技术学报, 2024, 39(14): 4508-4518.
Zhang Wuyu, Qi Lei, Zhang Xiangyu, et al.Reliability evaluation method for VSC-HVDC valve submodules considering the correlation between the degradation process of metallized polypropylene film capacitors and IGBT modules[J]. Transactions of China Electrotechnical Society, 2024, 39(14): 4508-4518.
[5] 冉昭玉, 刘雨杭, 孟礼, 等. 换流阀高压直流电容聚丙烯材料选型关键参数与方法[J]. 高电压技术, 2024, 50(6): 2354-2362.
Ran Zhaoyu, Liu Yuhang, Meng Li, et al.Key parameters and methods of polypropylene material selection for HVDC capacitors in converter valves[J]. High Voltage Engineering, 2024, 50(6): 2354-2362.
[6] Li Zhiyuan, Zhou Yihan, Wang Xuguang, et al.Failure mechanism of metallized film capacitors under DC field superimposed AC harmonic: from equipment to material[J]. High Voltage, 2024, 9(5): 1081-1089.
[7] 张天栋, 马海鑫, 刘刚, 等. 金属化薄膜电容器介电薄膜材料的研究现状[J]. 绝缘材料, 2024, 57(11): 18-33.
Zhang Tiandong, Ma Haixin, Liu Gang, et al.Research status of dielectric film materials for metallized film capacitors[J]. Insulating Materials, 2024, 57(11): 18-33.
[8] 吴云杰, 张金保, 赖伟, 等. 基于金属化薄膜电容器状态在线监测的剩余寿命评估方法[J]. 电工技术学报, 2024, 39(22): 7239-7255.
Wu Yunjie, Zhang Jinbao, Lai Wei, et al.Remaining lifetime assessment method based on on-line condition monitoring of metallized film capacitors[J]. Tran-sactions of China Electrotechnical Society, 2024, 39(22): 7239-7255.
[9] 杜伯学, 冉昭玉, 刘浩梁, 等. 干式直流电容器聚丙烯薄膜绝缘性能及其改进方法研究进展[J]. 电工技术学报, 2023, 38(5): 1363-1374.
Du Boxue, Ran Zhaoyu, Liu Haoliang, et al.Research progress of dielectric properties and improvement methods of polypropylene film for dry-type capacitor[J]. Transactions of China Electrotechnical Society, 2023, 38(5): 1363-1374.
[10] 张云霄, 张佳瑞, 蔡英健, 等. 多物理场下薄膜电容器用聚丙烯材料劣化及诊断方法研究进展[J]. 电工技术学报, 2025, 40(15): 4905-4926.
Zhang Yunxiao, Zhang Jiarui, Cai Yingjian, et al.Research progress on degradation and diagnostic methods of polypropylene materials for film capacitors under multiple physical fields[J]. Transactions of China Electrotechnical Society, 2025, 40(15): 4905-4926.
[11] Teixeira M, Del Hoyo I, Wandrowelsti F, et al.Evaluation of thermal degradation in isotactic polypropylene films used in power capacitors[J]. Journal of Thermal Analysis and Calorimetry, 2017, 130(2): 997-1002.
[12] Azmi A, Lau K Y, Ahmad N A, et al.Dielectric properties of thermally aged polypropylene nanocomposites[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2022, 29(2): 543-550.
[13] Zhang Yunxiao, Zhang Jiarui, Liu Yuhao, et al.Research insight into the change of aggregation structure of BOPP films and its influence on electrical properties under accelerated thermal aging[J]. Journal of Applied Polymer Science, 2024, 141(43): e56137.
[14] 程璐, 李志元, 王镜然, 等. 高压直流电场与谐波耦合作用下金属化膜电容器失效研究[J]. 中国电机工程学报, 2023, 43(22): 8955-8965.
Cheng Lu, Li Zhiyuan, Wang Jingran, et al.Mechanism study on the failure of metalized film capacitor under HVDC field superimposed harmonics[J]. Proceedings of the CSEE, 2023, 43(22): 8955-8965.
[15] 许然然. 柔性直流换流阀直流支撑电容器用聚丙烯薄膜绝缘失效及其抑制方法研究[D]. 天津: 天津大学, 2020.
Xu Ranran.Failure mechanism and suppression method of dielectric insulation of DC-link capacitor in flexible DC converter valve[D]. Tianjin: Tianjin University, 2020.
[16] 刘尚书, 吴致远, 仝殿杰, 等. 多物理场作用下的金属化膜自愈特性试验[J]. 高电压技术, 2024, 50(12): 5424-5434.
Liu Shangshu, Wu Zhiyuan, Tong Dianjie, et al.Experiment of self-healing properties of metallized films under multiple physical fields[J]. High Voltage Engineering, 2024, 50(12): 5424-5434.
[17] Wu Kangning, Sui Haoran, Ren Yongruo, et al.Evidently retarded degradation in breakdown strength of polypropylene eco-friendly cable insulation from trace self-grown γ-crystals during thermal aging[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2025, 32(2): 815-822.
[18] 周士贻, 门业堃, 刘博, 等. XLPE电缆绝缘片晶周期性结构演变及其对电性能的影响[J]. 中国电机工程学报, 2024, 44(3): 1205-1213.
Zhou Shiyi, Men Yekun, Liu Bo, et al.Lamellar periodic structure evolution of XLPE cable insulation and its influence on electrical properties[J]. Proceedings of the CSEE, 2024, 44(3): 1205-1213.
[19] 王霞, 孙晓彤, 刘全宇, 等. 基于空间电荷效应的绝缘老化寿命模型的研究进展[J]. 高电压技术, 2016, 42(3): 861-867.
Wang Xia, Sun Xiaotong, Liu Quanyu, et al.Research development of aging models of insulation materials based on space charge effect[J]. High Voltage Engineering, 2016, 42(3): 861-867.
[20] 胡一卓, 董明, 谢佳成, 等. 聚合物绝缘材料多因子老化的研究现状与发展[J]. 电网技术, 2020, 44(4): 1276-1289.
Hu Yizhuo, Dong Ming, Xie Jiacheng, et al.Status and progress in multi-factor ageing research for polymer insulation materials[J]. Power System Technology, 2020, 44(4): 1276-1289.
[21] Ohki Y, Hirai N.Tools for condition monitoring of polymeric electrical insulating materials[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2024, 31(6): 3294-3302.
[22] 刘任, 李琳. 基于模拟退火与Levenberg-Marquardt混合算法的Energetic磁滞模型参数提取[J]. 中国电机工程学报, 2019, 39(3): 875-884.
Liu Ren, Li Lin.Parameter extraction for energetic hysteresis model based on the hybrid algorithm of simulated annealing and Levenberg-Marquardt[J]. Proceedings of the CSEE, 2019, 39(3): 875-884.
[23] 贠祥, 张鑫, 王超, 等. 基于联合参数辨识的粒子群优化扩展粒子滤波的锂电池荷电状态估计[J]. 电工技术学报, 2024, 39(2): 595-606.
Yun Xiang, Zhang Xin, Wang Chao, et al.State of charge estimation of Li-ion battery using particle swarm optimization extended Kalman particle filter based on joint parameter identification[J]. Transactions of China Electrotechnical Society, 2024, 39(2): 595-606. |
|
|
|
2026, Vol. 41 
