With the increasing penetration of renewable power, its reliability and cost-effective production are becoming more important. A filter is inserted between the grid-connected inverter and the power grid to reduce the PWM switching harmonics, which may become a fragile part seen from the power electronics converter perspective. As the grid-connected inverter is typically designed with additional reactive power capability, this paper tries to investigate the additional stresses of the filter capacitor introduced by the reactive power injection. According to an electro-thermal stress evaluation, the time-to-failure distribution of a single LCL filter capacitor is investigated in detail. Moreover, the increasing equivalent series resistance along with the operational period is taken into account. Aiming towards a system-level reliability analysis, a Weibull distribution based reliability of an individual capacitor can be linked to the reliability of a capacitor bank by using a reliability block diagram. A case study of a 2 MW wind power converter shows that the lifetime is significantly reduced from the individual capacitor to the capacitor bank. Besides, over-excited reactive power injection further reduces the lifetime of the LCL filter capacitors.

中文翻译：

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无功功率对并网逆变器中LCL滤波器电容器寿命的影响

随着可再生能源渗透的增加，其可靠性和具有成本效益的生产变得越来越重要。在并网逆变器和电网之间插入一个滤波器，以减少PWM开关谐波，从电力电子转换器的角度来看，这可能成为易碎的部分。由于并网逆变器通常设计为具有附加的无功功率能力，因此本文试图研究由无功功率注入引起的滤波电容器的附加应力。根据电热应力评估，详细研究了单个LCL滤波电容器的失效时间分布。此外，考虑到等效串联电阻随着工作时间的增加而增加。旨在进行系统级的可靠性分析，通过使用可靠性框图，可以将基于威布尔分布的单个电容器的可靠性与电容器组的可靠性联系起来。对一个2兆瓦风力发电机的案例研究表明，从单个电容器到电容器组的寿命都大大缩短了。此外，过高的无功功率注入会进一步缩短LCL滤波电容器的寿命。