Thermal coupling between adjacent insulated gate bipolar transistor (IGBT) or diode chips is the result of nonuniform temperature distribution in a multichip IGBT module. This affects the junction temperatures and hence the total power loss predicted for the module. The study first investigates the impact of thermal coupling effect on the junction temperatures through a finite element method, and then develops a thermal coupling impedance model to represent such effects. The effect is shown to reduce with the distance exponentially. The model result agrees well with the test. The validated model is then used to predict the junction temperature swings during operational power cycling in a doubly fed induction generator wind turbine, showing the difference between the rotor and grid side converters. The model presented and the results obtained may be important for reliability evaluation and condition monitoring in the wind turbine power converters as well as in other multichip-paralleled power electronic systems.

Press-pack insulated-gate bipolar transistor (PP-IGBT) device is used in high-power modular multilevel converter high-voltage direct current (MMC-HVDC) system due to the advantages of high reliability and short-circuit failure. Considering safeties and stable operations, it is necessary to model and analyze the fatigue failure evolution of PP-IGBT device that improves the reliability of MMC-HVDC system. This paper proposes a method to analyze from fretting wear failure to short-circuit failure in PP-IGBT device. First, a multiphysics coupling model of a single-chip 3.3-kV/50-A PP-IGBT device is presented to analyze the fretting wear failure, and the weak layer and the fatigue effect are obtained by power cycling simulation. Second, considering the Al-Si diffusion reaction mechanism on the interface of IGBT chip, the short-circuit failure is investigated by the finite-element method model of PP-IGBT device with Al-Si osmotic hole, and the changing trend of characteristic parameters is estimated during short-circuit failure process. Finally, the steady state, power cycling, and short-circuit tests are used to verify the multiphysics coupling model, fretting wear failure, and short-circuit failure. The experiment indicates that the fatigue failure evolution of PP-IGBT device occurs from fretting wear failure to short-circuit failure, and it suggests that the proposed method can be applied to optimize design and condition monitoring of PP-IGBT device.

The transient overvoltage and oscillation phenomena, which are caused by its high switching speed in a solid-state DC circuit breaker based on the silicon carbide (SiC) metal–oxide–semiconductor field-effect transistor (MOSFET), are a crucial problem. This paper presents a simple and reliable method to manage such problem. An equivalent circuit model for SiC MOSFET is primarily established. The influence of stray inductance in energy absorption loop on the turn-off characteristics of the DC circuit breaker is then analyzed. Subsequently, possible typical overvoltage suppression methods, such as using a resistor–capacitor snubber circuit and increasing gate resistance and parallel capacitance between the gate and source, are simulated and analyzed. Thereafter, a peak voltage suppression method that does not sacrifice the fast switching capability of SiC MOSFET is proposed based on the different amounts of energy absorbed by metal oxide varistors (MOVs) with varying voltage levels. A basic principle for selecting a snubber MOV is proposed based on the voltage ratio of a snubber and an energy-absorbing MOV. Finally, the feasibility of the proposed method is verified via a small-scale principle prototype.

An intelligent control of photovoltaics is necessary to ensure fast response and high efficiency under different weather conditions. This is often arduous to accomplish using traditional linear controllers, as photovoltaic systems are nonlinear and contain several uncertainties. Based on the analysis of the existing literature of Maximum Power Point Tracking (MPPT) techniques, a high performance neuro-fuzzy indirect wavelet-based adaptive MPPT control is developed in this work. The proposed controller combines the reasoning capability of fuzzy logic, the learning capability of neural networks and the localization properties of wavelets. In the proposed system, the Hermite Wavelet-embedded Neural Fuzzy (HWNF)-based gradient estimator is adopted to estimate the gradient term and makes the controller indirect. The performance of the proposed controller is compared with different conventional and intelligent MPPT control techniques. MATLAB results show the superiority over other existing techniques in terms of fast response, power quality and efficiency.

Crosstalk in a phase-leg configuration significantly limit the high switching speed performance of silicon carbide (SiC) MOSFET due to their lower threshold voltage and higher allowable negative gate voltage as compared with traditional silicon (Si). To fulfill the potential fast switching speed quality of SiC MOSFET, an assist gate driver (AGD) circuit for crosstalk suppression based on negative-biased turn-off voltage was proposed, which contains an auxiliary capacitor and two passive transistors without additional control signals. First, a recommended gate driver by several SiC device manufacturers was introduced to analyze the mechanism of crosstalk. Then, the operation principle of the proposed AGD circuit was elaborated, and the parameter design criteria of the main elements were given. Finally, a simulation using LTspice and an experiment based on Wolfspeed 1200V SiC MOSFET tests were used to verify the effectiveness of the proposed gate driver. Simulation and experimental results show that the AGD circuit has a superior characteristic of crosstalk suppression under varying operating conditions. Thus, the proposed circuit could meet the fastidious requirement of fast-speed SiC MOSFET under high DC voltage condition with less complexity.

Press pack packaging technology has been widely used in insulated gate bipolar transistors for highvoltage and high-power density applications. The effects of unbalanced internal pressure, which occurs frequently within large-scale press-pack modules, remain unclear, and thermal parameters within modules cannot be directly measured due to the pressure-type package structure. Current and temperature distribution within 3300 V/1500 A modules are investigated to determine module reliability characteristics and derive future lifetime models using multi-physics models. Unbalanced clamping force causes extremely uneven temperature stress and electrical stress in spatial distribution. It indicates that partial chips must withstand high stresses that cause the initial fatigue of largescale press-pack modules. Junction temperature difference reaches up to 53.6 °C among chips at chip surface roughness of 1.27 μm. This condition shows that aging of modules will accelerate at the onset of partial chips degradation. Finite element modeling and equivalent test are utilized to verify the multi-physics model by using single-chip devices in parallel.