高频电力变压器高频绝缘特性与强电-热效应耦合作用机理研究

The insulation system of high-frequency power transformer renders unique characteristics under coupled influence of the strong electro-thermal effects, and the failure mechanism is far more complex than the power-frequency mode. This project focuses on electrical insulation properties of the high-frequency power transformer as to establish a systematic elucidation of the degradation and failure mechanism from both theoretical and experimental aspects. Based on multiple characterization parameters, both macroscopic and microcosmic techniques are utilized to study the influence of strong electro-thermal coupling effects on the high-frequency insulation aging, with a view to revealing the acting mechanism of dielectric loss, partial discharge and space charge under high-frequency and pulsed stresses. Unique features of the discharge defects as well as the evolution process are explored based on experiments superimposing multiple factors, and an equivalent testing methodology between high-frequency and power-frequency insulations involving PD characteristics is to be developed. Molecular dynamics simulation and quantum chemistry computation are applied as to further elucidate and reveal the high-frequency insulation degradation and failure mechanism from the molecular and microscopic levels，which are also correlated to the experimental studies. Based on the proposed degradation mechanism and multifactor characterization under strong electro-thermal coupling effects, aging assessment theory and fault diagnosis methodology for high-frequency insulation are established. The proposed research can provide theoretical and technological basis for the development of the high-frequency power transformer to be equipped in smart grid, which presents academic significance and application prospects.

高频电力变压器绝缘在强电-热耦合效应作用下表现为独有特征，其破坏机理较工频正弦模式更为复杂。本项目重点研究高频电力变压器的电气绝缘特性，从实验和理论两方面系统揭示高频电气绝缘的劣化与破坏机理。引入微观-宏观综合测试手段，基于多种表征参量研究高频/脉冲应力下强电-热耦合效应对绝缘老化特性的影响，揭示介质损耗、局部放电、空间电荷效应对高频绝缘老化的作用机制；基于多因子叠加实验方法，探索绝缘放电类缺陷在高频高压下的独有特征及其发展演化规律，发展一套基于局部放电特征参量的工频-高频绝缘等价测试方法；采用分子动力学与量子化学模拟，从分子层面与微观过程揭示绝缘在高频强场下的劣化与破坏机理，并与实验研究交互印证；基于强电-热耦合效应下的绝缘演化机理与多参量表征，建立高频绝缘的老化评估理论与故障诊断方法。本研究可为发展高频电力变压器这一新型智能电网装备奠定理论和技术基础，具有重要的学术意义和应用价值。

高频电力变压器作为电力电子变压器的重要组成部分，在可再生能源接入、微电网以及交直流电网互联等领域有广阔的应用前景。本项目重点针对强电-热耦合效应下高频电力变压器绝缘性能的关键科学与基础性问题，开展理论探索与创新研究。搭建了高频电-热联合老化实验平台，获得了材料表面形貌、电荷分布、官能团、键位、小分子产物以及放电特性的演化规律，实现了高频绝缘老化过程的多特征量表征；研究了脉冲电压参数（幅值、频率、上升时间、波形）对绝缘老化速率的影响，据此建立了波形参数-绝缘寿命的数学关联模型，可作为不同激励波形下高频绝缘性能的等价评估方法。获得了电压频率、波形以及温度对局放统计参量的影响规律，发现放电幅值和重复率随频率升高先上升后下降，即存在频致拐点现象，这为高频设备绝缘性能测试频率的选择提供了参考；研究了频率和温度对沿面放电起始电压、闪络电压和沿面绝缘寿命的影响，基于放电行为的变化规律实现了沿面放电的阶段划分，揭示了高频沿面放电的发展演化过程，并结合偏斜度、峭度和脉冲指标提出了沿面放电严重程度评估参量。基于分子反应动力学理论，建立了聚酰亚胺、环氧树脂等聚合物的分子结构模型，模拟分析了电、热应力作用下材料裂解的微观动态反应过程，获得了裂解产物种类、数量及其随时间的变化规律以及主要产物的形成路径，从原子层面揭示了高频绝缘的劣化机理。采用实验设计方法，研究了脉冲幅值、频率和温度对绝缘寿命的影响程度以及因素间的交互作用，据此提出了考虑多因素耦合效应的多因子寿命预测模型，提高了寿命预测的准确度；采用峰峰值、有效值和形状因子实现了电压波形参数的量化表征，并提出了高频-工频绝缘的等价实验方法；最后从材料表面物化特性以及放电统计参量等角度，建立了宏观-微观相结合的状态特征参数体系。本项目研究成果为推动高压大容量高频电力变压器的实用化发展提供了理论基础和参考依据。