Wei Lai

With the rapid deployment of flexible high-voltage direct-current (HVDC) systems, high-power press-pack insulated-gate bipolar transistors (PP-IGBTs) have become critical components. However, field data indicate premature overcurrent failures in PP-IGBTs under modular multilevel converter (MMC) operations. This study systematically investigates the short-term overcurrent failure mechanisms of PP-IGBTs under MMC-specific operational stresses, distinguishing them from conventional short-circuit or avalanche modes. A power cycling test platform emulating MMC submodule conditions was developed to capture the evolution of terminal characteristics. Furthermore, a double-pulse test platform was established to reproduce failure locations under service-relevant stresses. The study reveals a distinctive failure mode characterized by pronounced gate leakage and the eventual loss of normal gate control, leading to functional open-circuit failure—a phenomenon that has been rarely reported in the existing MMC literature. The experimental results indicate a decreasing trend in short-term overcurrent withstand capability with increasing clamping force and reveal a preliminary relationship between peak current and measured emitter-side temperature at failure. These findings provide insights into the failure mechanisms of PP-IGBTs and offer practical guidance for device selection, converter design, and reliability assessment.

Even contact pressure distribution among submodules in a press-pack insulated gate bipolar transistor (PP-IGBT) is an important factor in reliability screening tests before engineering application. However, the current stress-sensitive method for contact pressure measurement is an invasive method where each measurement would change the contact pressure distribution of submodules. It is necessary to study a non-invasive measurement method for contact pressure distribution in PP-IGBT. In this paper, a non-invasive measurement method based on the ultrasonic reflection coefficient is proposed to measure the contact pressure distribution within PP-IGBTs. Firstly, the characteristic of ultrasonic wave propagation at the contact interface of two different materials is analyzed. The influence of designed ultrasonic measuring platform for the contact pressure distribution in PP-IGBTs is explored to verify the new assembly measured part has little effects on the pressure distribution within the device by different clamping force experiment. Secondly, an efficient contact pressure measurement system for PP-IGBTs is designed, and a calibration method of ultrasonic reflection coefficient for contact pressure measurement is proposed. Finally, the accuracy of the proposed ultrasonic measurement method for contact pressure distribution is verified by comparing the measurement results with those of the stress-sensitive film method, which the relative error of contact pressure within PP-IGBTs in three different conditions is less than 10%.

Converter valves based on the modular multilevel converter (MMC) topology are the core of the voltage source converter-based high-voltage direct current transmission system, with press-pack insulated gate bipolar transistor (PP IGBT) modules being the key components. Studying the long-term aging failure mechanism of the PP IGBT under actual MMC operating conditions is of great significance for improving the safe and reliable operation of the transmission system. In this article, an electric–thermal–mechanical coupled multifield model of the PP IGBT device is built to analyze the influence of junction temperature and pressure on stress and strain distribution, identifying the weak points. Then, based on the alternating current (ac) power cycling tested rig, which equivalently reproduces the working conditions of the MMC submodule, the influence of different junction temperatures and pressures on long-term aging failure is studied, revealing the evolution of key characteristic parameters during the aging process. Two main failure modes are identified under ac power cycling tests. One mode is caused by overvoltage short-circuit failure due to the blocking voltage drop, and the other is induced by open-circuit failure due to uncontrolled gate current. Finally, the evolution of microscopic morphology and static characteristic parameters over the entire lifetime during the power cycling test are obtained, emphasizing the differences between ac and direct current (dc) power cycling tests. The results show that there are significant differences in overheating failures between ac and dc power cycling tests, highlighting the critical role of ac conditions in failure analysis and reliability assessment. The study of the long-term failure evolution mechanism of the PP IGBT device under actual MMC working conditions aims to guide operational management, control protection, and device optimization design for the reliability of MMC systems.

With the development of pulse technology, reinforced concrete buildings are exposed to increasingly complex high-power electromagnetic pulse (EMP) environments, posing risks of functional degradation or destruction of indoor electronic equipment and systems. Therefore, it is imperative to assess the internal fields of buildings under EMP irradiation. The challenge lies in the multi-scale characteristics of reinforced concrete buildings, where fine grids are required for the accurate modelling of rebar, thereby consuming substantial computing resources. To address this challenge, this paper proposes a fast calculation method of the time–domain coupling characteristics between buildings and EMPs based on the electromagnetic parameter equivalence of reinforced concrete walls. The method first calculates the equivalent electromagnetic parameters from the S-parameters of the walls, which are then fitted into polynomial rational functions. Then, the auxiliary differential equation finite-difference time–domain (ADE-FDTD) method is used to analyze the time–domain coupling characteristics of reinforced concrete walls and buildings under EMP irradiation. The results show that the proposed method significantly enhances computational efficiency while maintaining high accuracy. Specifically, for a large two-story reinforced concrete building, the method achieves a 3.2-fold increase in computational speed and a 4.3-fold reduction in memory usage compared to conventional commercial software (CST Studio Suite 2022). This approach provides an effective solution for simulating the coupling characteristics between large reinforced concrete buildings and external EMPs.

The Insulated Gate Bipolar Transistor (IGBT) is a critical component of power electronic equipment, and the health of the IGBT device is of utmost importance to ensure the reliability and stability of the power system. This paper proposes a method for assessing the health status of IGBT device based on characteristics identification. Firstly, a finite element model of the IGBT device is established to analyze the performance of bond-wire and solder layer under the power cycling condition. Secondly, the IGBT device under solder layer failure and bond-wire failure are simulated, and the characteristics parameters of the IGBT device under different aging degree are analyzed. Finally, an adaptive network-based fuzzy inference system (ANFIS) algorithm is used to establish the IGBT device health status assessment model, and power cycling test data is used to verify the accuracy of the health state evaluation model, which reaches more than 94.8%. The results show that the proposed method can effectively evaluate the health status of IGBT device.

In electric locomotive system, the function of traction converter depends heavily on insulated gate bipolar transistor (IGBT) module, and IGBT module is prone to failure. Traditionally, ensuring safety has involved expensive and wasteful “mileage maintenance,” which includes regular replacement of IGBT modules. Therefore, assessing the residual reliability of these modules, taking into account their different service miles, is meaningful. First, the dynamic and static characteristics of IGBT modules under different service mileage are compared and analyzed. Second, the power cycling test for different mileage IGBT modules is carried out to analyze the differences between them. Then, the microscopic analysis of the failure module further confirms the results of the failure analysis. Finally, the fatigue accumulation state of IGBT modules can be deduced from the power cycling test data to predict the remaining life of IGBT modules. This study reveals that the health state is unevaluable using dynamic or static characteristic parameters. It is proved that the power cycling tested results are significantly different for different service-mileage devices. Finally, a remaining lifetime predicted method of power devices is proposed, where the health status is inverted by the power cycling tests.

Due to the effects of electromagnetic stress and thermoelastic effect, mechanical stress waves are generated in power semiconductor devices during turn-off moment. The characteristics of these turn-off stress waves vary when power semiconductor devices are subjected to different temperature environments. Measuring these turn-off stress waves is beneficial for analyzing the influence of temperature on the physical properties of power semiconductor devices. As a traditional contact-based mechanical stress wave detection method, acoustic emission testing (AET) is inevitably influenced by temperature, affecting the sensor’s measurement performance. This study employs non-contact laser Doppler vibrometry (LDV) to measure turn-off stress waves in silicon carbide metal-oxide-semiconductor field-effect transistor (SiC MOSFET) at different temperatures. By comparing the signals measured using AET, it has been demonstrated that the signals measured using LDV more effectively reflect the temperature-dependent variations in turn-off stress waves of SiC MOSFET. This research not only broadens the application scope of condition monitoring technology based on mechanical stress wave parameters for power semiconductor devices but also demonstrates the unique advantages of LDV in condition monitoring of power semiconductor devices in different temperature environments.

The conventional TO-247-3 packages with single-sided cooling limit the thermal and electrical performances of discrete SiC MOSFET devices. In this paper, a double-sided cooling press-pack (PP) packaging approach for the discrete SiC MOSFET device is proposed to optimize its thermal and electrical performances. First, a double-sided cooling PP structure for the discrete SiC MOSFET devices is designed with a copper foam gate pin and an embedded fixture. Then, based on finite element simulations, the steady-state thermal and electrical performances of the discrete SiC MOSFET device with the double-sided cooling PP package are analyzed, and the parasitic inductance of the designed SiC MOSFET device is extracted by the ANSYS Q3D software. Finally, a prototype of the double-sided cooling PP SiC MOSFET device is fabricated, and test platforms are established to verify its performance. The research findings demonstrate that the designed double-sided cooling PP SiC MOSFET device can reduce thermal resistance and switching loss by 47.4 % and 42.3%, respectively.