Lifetime prediction of dc-link capacitors in a single drive has been discussed before, which indicates that the capacitor in a standard drive meets serious reliability challenges and in a slim drive does not. However, in most of the applications, drives are connected in parallel with the power grid. The large amount of harmonic distortion produced by nonlinearity drives may transmit and couple between grid and drives, which changes the stresses of devices as well as the dc-link filters. Therefore, the estimated results in a single drive cannot be extended to multiple drives any more. This article investigates the lifetime of dc-link capacitors in multiple drives system. First, by decoupling the interactions among grid-connected drives, a simplified equivalent circuit model and its analytical model to obtain the dc-link continuous current in multiple drives is proposed, which releases the designers from configuring the large simulation for multiple drives. Then, applying the lifetime prediction method, the lifetime of dc-link capacitors in multiple drives is investigated, in terms of types of drives, numbers of drives, and grid conditions. The results show that the lifetime of the standard drives extends in the multidrive systems and the lifetime of the slim drives decreases in the multidrive systems, which break the previous mind. Finally, based on the proposed analytical model and lifetime estimation method, the capacitor sizing from reliability aspect for multiple slim drives is given. The outcomes of the lifetime investigation could be a guideline for the design of the capacitive dc link in multidrive systems.

中文翻译：

---

基于简化分析建模的多驱动系统直流母线电容器寿命预测

之前已经讨论过单个驱动器中直流链路电容器的寿命预测，这表明标准驱动器中的电容器会遇到严重的可靠性挑战，而超薄驱动器则不会。然而，在大多数应用中，驱动器与电网并联。非线性驱动器产生的大量谐波失真可能会在电网和驱动器之间传输和耦合，从而改变设备以及直流链路滤波器的应力。因此，单个驱动器中的估计结果不能再扩展到多个驱动器。本文研究了多驱动系统中直流母线电容器的寿命。首先，通过解耦并网驱动器之间的交互，提出了一种简化的等效电路模型及其分析模型，以获得多驱动器中的直流链路连续电流，使设计人员无需为多驱动器配置大型仿真。然后，应用寿命预测方法，根据驱动器类型、驱动器数量和电网条件研究多个驱动器中直流母线电容器的寿命。结果表明，标准驱动器的寿命在多驱动器系统中延长，而薄型驱动器在多驱动器系统中的寿命缩短，这打破了之前的想法。最后，基于所提出的分析模型和寿命估计方法，从可靠性方面给出了多个薄型驱动器的电容器选型。