Overcurrent Protection Enabled by Broadband Rogowski Coil Current Sensor for Medium-Voltage SiC MOSFET

Abstract

To guarantee safe switching of the expensive medium-voltage (MV) device with limited durability, the overcurrent protection scheme based on Rogowski coil current sensor (RCCS) is the promising method, featuring fast response and galvanic isolation. However, it is an inherent contradiction to achieve the RCCS with both high noise immunity and high-bandwidth capabilities. In addition, the nonideal dc and low-frequency characteristics of the integrator cause drift and droop errors. In this article, to address the aforementioned challenges, the broadband RCCS is developed and integrated into the overcurrent protection circuit for the MV SiC mosfet. The novel coil is designed based on the transmission line theory to overcome the constraints imposed by parasitic components on bandwidth. The proposed coil achieves an extra-high bandwidth of approximate 300 MHz with high mutual inductance and shielding layers for high noise immunity. Furthermore, the broadband integrator design method with low-frequency attenuation is proposed to eliminate drift and reduce droop errors significantly. Based on the developed RCCS, the proposed overcurrent protection circuit reacts to both the fault under load and hard switching fault rapidly and softly turns off the device within merely 200 ns. Comprehensive experiments demonstrate its exceptional potential in monitoring current and protecting the expensive MV devices.