Electrothermal Stress Analysis and Lifetime Evaluation of DC-Link Capacitor Banks in the Railway Traction Drive System

Abstract

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.

Power Device Losses in Two-Level Converters with Direct Current Controllers for Grid Connected Applications

“…The development of electrothermal models is an area of increasing interest in power electronics. This type of models enables the investigation of the loss distribution within the devices comprising a converter and the analysis of the resulting junction temperature excursion [12,20,21], as well as passive components [22]. As a result of the thermomechanical stresses, the power electronic components degrade, resulting in a reduced lifetime [23,24].…”

Adaptation of a Real-Time Deep Learning Approach With an Analog Fault Detection Technique for Reliability Forecasting of Capacitor Banks Used in Mobile Vehicles

“…The utilization of capacitor banks (CBs) as energy storage in power grids, railroad systems, and electric vehicles (EVs) has been increased significantly over the past few years [1].…”

“…In [4]- [5], different models and technologies of power semiconductors and CBs have been introduced, which can be used in power grids for renewable energy generation. The CB is typically a combination of series-parallel electrolytic capacitors [1]. The electrolytic capacitor performance is complicated and is strongly influenced by operating conditions such as frequency, current, voltage, and ambient temperature.…”

“…Cd and Equivalent series resistance (ESR) are the main factors responsible for the degradation of the CB, where the ESR is the limiting factor of the output current of the CB. Much research has focused on the study of electrolyte capacitor degradation [1], [6]- [11]. For instance, Authors in [6] improve the CB aging model considering the temperature, variable load, and constant charge.…”

“…However, a sudden fault may occur in the internal capacitors of the CB. The short/open-circuit faults might occur for several reasons: current surges, electrolytic capacitor swelling, and material oxidation used in the electrolytic capacitor [1]. Other unforeseen faults can sometimes befall (e.g., a heavy shock to the CBs), which might damage the internal structure of the CBs.…”