Electro-Thermal Stress Analysis and Lifetime Evaluation of DC-Link Capacitor banks in the Railway Traction Drive System

In the railway traction drive system, the reliability of DC-link capacitor banks faces enormous challenges due to the multi-operation conditions, the complex physical structures, and the safe operation requirements. Considering these issues, this paper proposes a reliability evaluation method of the DC-link capacitors banks to provide a guideline for preventive maintenance in the traction drive system. In the electro-thermal stress analysis, different from the conventional methods, the dynamic power loss profile is obtained by the sliding-window discrete Fourier transform (DFT) and the equivalent series resistance is fitted by the neural network. Afterward, a bidirectional thermal model is established to estimate the thermal stress under the dynamic power losses, considering the impact of thermal capacity, thermal coupling, and air-cooling heat dissipation. In addition, according to stability analysis and the rated temperature limitation, an end-of-lifetime standard that meets the safe operation requirement of the train is firstly proposed, thereby evaluating the lifetime bottleneck of the DClink capacitor banks. The evaluation results can provide a reference to use the lower-cost on-condition maintenance instead of scheduled maintenance in the railway traction drive system. Furthermore, a prototype experiment is performed to verify the effectiveness of the electro-thermal stress model.