Hardware Implementation of a SiC Three-Phase Four-Leg VSI with Sigma-Delta Modulation to Comply with the Military Standards 1399 and 461

This paper demonstrates sigma-delta pulse density modulation without common mode voltage in a four-leg voltage source inverter built with SiC MOSFETs and controlled by an FPGA. The converter does not produce common mode voltage in the switching frequency range, thus meeting the conducted EMI limits in MIL-STD-461G without the need of a large common mode choke. Using pulse density modulation ensures that switching updates occur simultaneously for all phases. Further, the output voltage power quality meets the requirements in MIL-STD-1399 section 300 part I for type 1 voltage. The practical implementation of the control system on an FPGA is presented and compliance with the two military standards is demonstrated on a laboratory prototype.