Power management for self-powered SiC based AC smart-breaker for nano-grid applications

This work targets a novel self-powered Smart Circuit Breaker (SCB) for monitoring and controlling power in emerging small-scale AC nano-grids. The SCB concept is intended as a direct replacement of standard(120 Vac, 15 Arms) household circuit breakers, which imposes several challenging constraints. The SCB must therefore generate its own internal supply from the small AC voltage drop across the main switch when the breaker is closed. The SCB is composed of the following key blocks: 1) back-to-back 900 V Silicon Carbide (SiC) MOSFETs as the main power switches, 2) a low-voltage energy harvesting circuit, 3) a high-voltage step-down converter, and 4) low-power digital controller and wireless communication circuits. In order to stabilize the internal supply voltage under a wide range of AC load currents, a novel approach of dynamic on-resistance control is implemented, through adaptive gate-drive and MOSFET segmentation. The fabricated SCB prototype dissipates only 7.4 W for a 13 Arms AC load, corresponding to an efficiency of 99.5%.