Short fail-safe capability and fault diagnosis strategies dedicated to a reconfigurable 5-level double-boost PFC

A new 5-level reconfigurable PFC topology with low energy short-failure capability and fast fault-diagnosis is proposed. It includes a 2-stacked low energy 3-level Fly-Cap Boost through two input low frequency rectifiers. 600V-30kHz devices in series pear stack allow one short-fault for transistor and up to two short-faults for diodes. Firstly, authors shows for the first time the low ageing drift and the great stability of the parasite short-failure resistance (R_sc) of failed CoolMos™ transistors and SiC diodes inside well known epoxy molded package (TO220/TO247/TO3P cases). Secondly, two fault-diagnosis strategies are presented: one directly monitors the voltages across the flying capacitors to detect and to localize the faulty switch by means of two sensors; other is based on a harmonic detection (magnitude and phase-shift) at the switching frequency through only one voltage sensor at the input of the PFC. All these strategies are analyzed and simulated with the efficient PD-PWM technique that exhibits a lower THD of the leg-leg input voltage for three-phase application. The design and the most important features are highlighted thanks to a digital control frame and a single-phase mock-up rated to AC115V-DC400V - 4kW-4×31kHz.