Rogowski Switch-Current Sensor Self-Calibration on Enhanced Gate Driver for 10 kV SiC MOSFETs

In medium-voltage (MV) applications high-density, high-efficiency converters are necessity. Novel switching-cycle capacitor voltage control (SCCVC) for the modular multilevel converters (MMC) in combination with latest generation of SiC MOSFET devices will enable converters to meet those specifications. To enable SCCVC high-bandwidth Rogowski switch-current sensor (RSCS) is integrated on the gate driver (GD) to serve as peak-current-mode control sensor. Issues of RSCS OpAmp integrator non-idealities have to be resolved in order to achieve high accuracy. Due to often temperature swings and reduced lifetime, mechanical potentiometer is not preferred solution. As an alternative, this paper proposes digital potentiometer (DPOT) as a part of closed-loop self-calibration for RSCS on enhanced GD. Proposed method has high resolution of 98.6μV to eliminate input offset voltages, fast self-calibration finished in maximum 12.45ms, with maximum error of ±2.5A of RSCS current sensor. Experimental results at 6kV, 80A, 10kHz, switching as fast as 100V/ns show great accuracy of RSCS sensor, with minimum drifting.