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Accurately predicting the temperature of semiconductor devices is very important in the initial design of the power electronics converter. RC thermal models derived from the well-known methods have some ability to predict the temperature. However, the accuracy is boundary condition specific; hence, these methods cannot be used in the reliability analysis. To make the thermal model more accurate and robust, the factors contributing to discrepancies need to be analyzed carefully. These are power-module-materials’ nonlinear properties, thermal grease layer, and the cooling system (i.e., liquid-cooled cold plate). In this article, the estimation of accurate RC parameters from the FEA thermal model is demonstrated in COMSOL. The electrical model having temperature-dependent power loss model is coupled to a refined thermal model and solved in a circuit simulator, PLECS. The proposed method is applied in two applications: assessing thermal interaction between IGBTs and antiparallel diodes in a half-bridge power module and assessing thermal interaction among the discrete switches in an interleaved bidirectional dc–dc converter. Results show that the impact of material nonlinearity, thermal grease layer, and cooling boundary conditions are significant for accurate prediction of IGBT and diode temperatures. The proposed model is consistent with FEA results and differs by 2%–6.5% compared with the experimental results. [ABSTRACT FROM AUTHOR]

A three-phase, multilevel rectifier using active voltage injection with one MOSFET device is presented. The injector consists of a bidirectional switch that modifies the behavior of a 12-pulse rectifier resulting in either 24-pulse or multilevel pulsewidth-modulated (PWM) operation. The resultant input currents are almost sinusoidal, the line current THD being 2.36% for 24-pulse operation and 1.06% for PWM operation. The MOSFET current is 2.9% of the load current. The circuit operation, idealized waveforms and modulation strategy are explained and experimental results are presented. [ABSTRACT FROM AUTHOR]

A new converter topology for a three-phase multi- pulse rectifier circuit is described. This converter draws almost sinusoidal currents from the ac system with very low harmonic content and typically less than 3% total harmonic distortion. The topology uses only passive components and has a lower component count than other rectifier circuits with similar performance. Two six-pulse rectifier bridges are connected in series, fed by a series connection of transformers, to form a 12-pulse system. An additional low power harmonic injection circuit enhances the performance of the circuit to obtain low harmonic current pollution levels that are comparable with those achieved from a 24-pulse rectifier. The circuit operation is explained and experimental results are presented. [ABSTRACT FROM AUTHOR]