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A negative input-resistance compensator is designed to stabilize a power electronic brushless dc motor drive with constant power-load characteristics. The strategy is to feed a portion of the changes in the dc-link voltage into the current control loop to modify the system input impedance in the midfrequency range and thereby to damp the input filter. The design process of the compensator and the selection of parameters are described. The impact of the compensator is examined on the motor-controller performance, and finally, the effectiveness of the controller is verified by simulation and experimental testing.Index Terms-Brushless dc motor drive, negative inputimpedance instability.

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Circuit level analytical models for hardswitching, soft-switching and dv/dt-induced false turn on of SiC MOSFETs and their experimental validation are described. The models include the high frequency parasitic components in the circuit and enable fast, accurate simulation of the switching behaviour using only datasheet parameters. To increase the accuracy of models, nonlinearities in the junction capacitances of the devices are incorporated by fitting their nonlinear curves to a simple equation. The numerical solutions of the analytical models provide more accurate prediction than a LTspice simulation with a threefold reduction in the simulation time. The analytical models are evaluated at 25°C and 125°C. The effect of snubber capacitors on the soft-switching waveforms is explained analytically and validated experimentally, which enables the techniques to be used to evaluate future soft-switching solutions. Finally, the dv/dt-induced false turn on conditions are predicted analytically and validated experimentally. It was observed that consideration of nonlinearities in the junction capacitances ensures accurate prediction of false turn on, and that the small shoot through current due to false turn on can increase the switching loss by 8% for an off state gate bias of -2V.

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