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This paper focuses on the maximum peak shifting phenomenon observed in drain-source voltage proflle during the turn-off transient of Silicon Carbide Metal Oxide Semiconductor Field Effect Transistor (SiC MOSFET). The cause of this phenomenon is identified and discussed. The influence of power loop parasitic resistance and common source inductance on voltage overshoot and ringing is also analyzed. Both large power loop parasitic resistance and common source inductance lead to damping of voltage ringing as well as peak growth. Peak growth becomes a concern under two conditions; prolonged turn-off transient and a high ratio of common source inductance to power loop inductance. Both of these can make the maximum voltage peak grow beyond the safe operation area (SOA) of SiC MOSFET.

The state of charge (SOC) of lithium batteries is an important parameter of battery management systems. We aim at the problem that the noise variance is fixed during the estimation of the battery state by the unscented Kalman filter (UKF), which leads to low estimation accuracy. Lithium battery SOC estimation based on the UKF and whale optimization algorithm (WOA) is proposed. The first WOA is used to identify the parameters of the battery model. WOA–UKF is used to estimate the SOC of the battery, in which the observed noise variance and process noise variance of the UKF are updated through the second WOA, thereby the estimation accuracy is improved. The experimental results verify the effectiveness of the improved method.

SiC MOSFET has gradually obtain more attention in the field of power converter, due to its good performance of high blocking voltage and fast switching speed. However, fast switching transient process makes it more sensitive to parasitic parameters than the silicon counterparts, leading to the more electrical stress. In serious cases, device failure or damage may directly occur. In addition, switching oscillation interacting between the circuit stray inductance and parasitic capacitance will result in more switching losses and undesirable electromagnetic interference noise. In the paper, simple and effective simulating models taken account of all key parameter are established for the analysis of the oscillation frequency and voltage overshoot in turn-off process of SiC MOSFET. Simulation and experiments both show that turn-off oscillation frequency is determined by SiC MOSFET output parasitic capacitance and power loop parasitic inductance. Moreover, turn-off maximum peak voltage will shift regularly with various switching speed.