DC-link capacitors are one kind of reliability-critical component in traction inverters. As such, it is essential to evaluate the degradation characteristics of dc-link capacitors. Accelerated life testing is an effective and standard method to evaluate the capacitors' lifetime and degradation mechanisms. Therefore, an accelerated life testing method for dc-link capacitors in three-phase inverter applications is proposed in this article. In order to reproduce the same encountered stress, exactly reflecting the real condition for the capacitor under test, a three-phase inverter with the capacitor under test and a three-phase balanced inductor load are used as the evaluation circuit. Due to the employment of the inductor load, the power consumption of the inverter can be reduced, while the full-scale current rating can be maintained so that the capacitor under test is subjected to the practical ripple current stress. In order to estimate a capacitor's capacitance with high accuracy, an effective and direct condition monitoring method, which is based on the proposed evaluation circuit, is also proposed in this article. By injecting an ac voltage into the dc link, the ac current and voltage components in the dc-link capacitor are generated. Then, the capacitance mathematical model can be developed by analyzing the injected voltage component and the resultant current component. As the proposed method only requires estimating the parameters from the input voltage and current, there is no need to install additional capacitor current sensors, which are usually difficult to install. Moreover, the amount of monitored and processed data can be reduced. Thus, the proposed method is easy to implement for accelerated life testing in practice. In addition, experiments are carried out to verify the analysis and effectiveness of the proposed solution.

中文翻译：

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逆变器应用金属化薄膜电容器的加速寿命测试方法


直流母线电容器是牵引逆变器中一种对可靠性至关重要的元件。因此，评估直流母线电容器的退化特性至关重要。加速寿命测试是评估电容器寿命和退化机制的有效且标准的方法。因此，本文提出了一种三相逆变器应用中直流母线电容器的加速寿命测试方法。为了再现相同的应力，准确反映被测电容器的真实状况，采用带有被测电容器的三相逆变器和三相平衡电感负载作为评估电路。由于电感负载的使用，可以降低逆变器的功耗，同时可以保持满量程额定电流，使被测电容器承受实际的纹波电流应力。为了高精度地估计电容器的电容，本文还提出了一种基于所提出的评估电路的有效且直接的状态监测方法。通过将交流电压注入直流链路，直流链路电容器中产生交流电流和电压分量。然后，可以通过分析注入的电压分量和产生的电流分量来建立电容数学模型。由于所提出的方法只需要根据输入电压和电流估计参数，因此不需要安装通常难以安装的额外电容器电流传感器。此外，可以减少监视和处理的数据量。因此，所提出的方法在实践中易于实施加速寿命测试。 此外，还进行了实验来验证所提出解决方案的分析和有效性。