Design of Rogowski Switch-Current Sensor With Offset Compensation for Three-Phase SiC Inverter

Abstract

This article proposes a Rogowski switch-current sensor (RSCS) with the offset compensation for the current control of the three-phase SiC inverter. The RSCS is built into the four-layer print circuit board (PCB) gate drive board. The coil parameters are analyzed with the Ansys software (Maxwell and Q3D) and then compared with the measurement results. The analog signal processing circuits are implemented with the operational amplifier (op amp) to reconstruct the switch current and the phase current. Unfortunately, the RSCS suffers from the op amp offset voltage and bias current integration, which varies according to the duty cycle and switching frequency. This article proposes an offset compensation software (S/W) to address this issue. Moreover, an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> discharge factor is proposed to make up for the discharging phenomenon of the capacitor in the integrator feedback path. A three-phase SiC inverter prototype is built and tested with the three-phase inductor load to verify the feasibility of the method. Experimental results at 10–30 kHz, 600 V, 150 A show the proposed method to have less than 2% sensing error.