This study presents an open-circuit fault diagnosis method based on residual changing rate instead of the specific switching signals injection for single insulated gate bipolar transistor in the single-phase pulse-width modulation (PWM) converter. Firstly, the mixed logical dynamic model of the single-phase PWM converter is established to obtain the residual of grid-side current. Then, the characteristics of residual changing rate are obtained through the combination of theoretical analysis and simulation results. Furthermore, the diagnostic variables based on the residual changing rate are defined by the isolation of switching signals. Also compared with the threshold, fault detection and location can be accomplished. The proposed diagnosis method does not need extra sensors and injection of special switching signals, which can reduce the diagnosis complexity and does not affect operating state of the system. Furthermore, the diagnostic method has fast diagnosis speed and robustness against false alarms under different operation conditions. Experimental results have illustrated the validity and feasibility of the proposed diagnostic method.
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.
Islanding detection is an essential function for safety and reliability in grid-connected Distributed Generation Systems (DGS). Passive and active islanding detection methods have been analyzed in literature considering DGS with only one inverter connected to the utility. With the big scale application of photovoltaic (PV) power systems, islanding detection technology of multi-inverter DGS has been paid more attention. This paper analyzes the performance of diverse islanding detection methods in multiple inverters grid-connected PV systems. Non-Detection Zones (NDZ) of multi-inverter systems in a load parameter space are used as analytical tool. The paper provides guidance for the islanding detection design in multiple grid-connected inverters.
The aging fracture of bonding wire is one of the main reasons for failure of insulated gate bipolar transistor (IGBT). This paper proposes an online monitoring method for IGBT bonding wire aging that does not interfere with the normal operation of the IGBT module. A quantitative analysis of aging degree was first performed, and the results of multivariate and univariate monitoring were compared. Based on the relationship between the monitoring parameters and the aging of the IGBT bonding wire, gradual damage of the IGBT bond wire was implemented to simulate aging failure and obtain the aging data. Moreover, the change of junction temperature was considered to regulate monitoring parameters. Then, the aging degree was evaluated by an artificial neural network (ANN) algorithm. The experimental results showed the effectiveness of the proposed method.
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