GaN Four-leg Inverter Implementing Novel Common Mode Elimination using a Hardware-in-the-loop System-Level Controller

This paper presents a novel wide bandgap four-leg inverter with common mode (CM) voltage elimination implemented using a Typhoon HIL 402 as the system-level controller. The four-leg inverter is built using GaN devices to minimize the switching losses and is controlled through pulse density modulation. The CM elimination method satisfies the MIL-STD-1399 requirements including maintaining balanced voltages during unbalanced load conditions. The MIL-STD-461G conducted emission (CE) limits for current and voltage (CE101 and CE102 respectively) are also met without the use of a CM choke. Both simulation and experimental results are presented to demonstrate the efficacy of the novel control method. The control approach is detailed, and comprehensive experimental results are provided for motor drive applications at 230V under varying load conditions including the effects of deadtime on the proposed CM elimination approach and in meeting the standard requirements. Modulation strategies including sine-triangle pulse-width modulation (SPWM) and space vector pulse-width modulation (SVPWM) are also implemented in both simulation and experimentally to compare with the ΣΔM. In addition, switching power losses and dc-bus utilization comparisons with a Si inverter are included. Based on the dc-bus utilization results, an approach to increase the dc-bus utilization of the proposed CM elimination approach is presented.