周期性脉冲电场下电力电子装备绝缘空间电荷特性研究

Periodic pulsed electric field is a common problem faced by the insulation of power electronic equipment in HVDC project, which leads to the early failure of insulation materials. Insulation breakdown under pulsed electric field is closely related to space charge behavior. However, the characteristics of space charges under pulsed electric field remain unclear, which requires deep research. It helps to explain the mechanism of insulation breakdown. In this project, measurement technology of space charges under periodic pulsed electric field is developed to accurately measure the charge distribution before and after the rising and falling edges of square wave pulses; characteristics of charge behavior at the rising and falling edge are obtained by comparing before and after impulse; with the variation of the slope of rising and falling edges, repetition frequency, duty cycle, polarities and amplitude ratio of DC and pulse voltage, the charge behavior at the rising and falling edges and the accumulation and attenuation characteristics along the high and low levels are researched under different waveform parameters; the breakdown time of insulation materials under pulsed electric field with different waveform parameters is studied and the influence of charge characteristics on the insulation breakdown is discussed. The purpose of this research is to demonstrate the space charge behavior characteristics and its influence mechanism on insulation breakdown under periodic nanosecond or microsecond pulsed electric field, and to provide theoretical basis for the optimization of insulation materials of power electronic equipment and the improvement of reliability of HVDC transmission, which has important scientific significance and application value.

承受周期性脉冲电场是高压直流输电工程电力电子装备绝缘面临的共性问题，易引发绝缘早期失效。脉冲电场下绝缘击穿与空间电荷行为密切相关，然而脉冲电场下空间电荷特性尚不明确，亟需开展深入研究。本项目通过优化周期性电场空间电荷测试技术，精确测试方波脉冲上升沿、下降沿之前和之后的电荷分布；对比脉冲前后电荷分布的变化，获得上升沿、下降沿时刻电荷行为特征；通过调整上升沿和下降沿斜率、重复频率、占空比、直流与脉冲电压的极性组合和幅值比例等波形参数，研究上升沿、下降沿时刻电荷运动行为和高电平、低电平阶段电荷积累和衰减特性随波形参数的变化规律；开展不同波形参数脉冲电场下绝缘击穿寿命研究，探讨电荷特性对绝缘击穿的影响规律。通过本项目的研究阐明周期性纳秒或微秒脉冲电场下电力电子装备绝缘空间电荷行为特性及对绝缘击穿的影响机制，为绝缘材料优化改进、高压直流输电可靠性提升提供理论依据，具有重要的科学意义和应用价值。

承受周期性脉冲电场是高压直流输电工程电力电子装备绝缘面临的共性问题，易引发绝缘早期失效。脉冲电场下绝缘击穿与空间电荷行为密切相关，然而脉冲电场下空间电荷行为特性尚不明确，亟需开展研究，以揭示周期性脉冲电场下绝缘劣化内在机制。本项目研发了触发时间控制电路，实现纳秒和微秒脉冲电场下电荷测试时间的精确匹配；研制了极化脉冲电压和电荷测试用脉冲电压的叠加耦合电路，确保两类脉冲电压不发生相互干扰；在此基础上，构建脉冲电场下空间电荷测试平台。实验探知脉冲边沿时刻的电荷激发分子振动现象，发现分子振动强度具有随上升沿时间缩短而增强的趋势，研究了电荷积累、电场强度和缺陷状态对电致振动强度的影响规律；通过上升沿和下降沿之前和之后电荷分布的对比，发现在上升沿和下降沿的电压突变时刻存在电荷的快速运动行为，表现为电荷的注入和迁移；脉冲陡度对电荷动态行为有重要影响。提出了电荷受力分析理论，阐释脉冲电场下电荷激发分子振动和电荷动态行为机制；通过电荷所受电场力与材料应力之间的平衡关系分析，归纳出脉冲边沿时刻由于电场突变导致电荷受力平衡被打破是电致振动和电荷动态行为的关键诱因；借鉴弹簧振子理论，构建电致振动的数学模型，计算电致振动强度随脉冲陡度的变化曲线，同实验获得规律相符，验证了所提理论的正确性。从电致机械应力和电荷动态行为两个方面，阐明了脉冲电场下电荷特性对绝缘劣化和击穿的影响机制；通过电荷动态行为释放能量和电致机械应力的耦合作用分析，推导电荷积聚缺陷位置的疲劳损伤，总结出脉冲电场下绝缘劣化机制及影响因素。通过本项目的研究，明晰了高压电力电子装备绝缘加速失效的内在机理，剖析出关键影响因素，为提升耐脉冲电场冲击能力的材料调控提供指导建议，有利于提升高压电力电子装备绝缘可靠性，对于电力电子变压器、变频电机以及高电压大功率器件封装绝缘优化设计具有重要的科学意义和应用价值。