Novel Common Mode Voltage Elimination Methods in Three-Phase Four-Wire Grid-Connected Inverters

This paper presents two current control methods to attenuate the common mode (CM) conducted emissions in three-phase four-wire four-pole inverters connected to an AC distribution bus and operating in grid-following mode. Delta modulation and model predictive control both achieve elimination of the common mode voltage at the output of the three-phase four-pole inverter and meet the requirements of the military standard 461G without a full-size CM choke. The differential mode performance is comparable to that achieved with the benchmark three-dimensional space vector modulation, which does not cancel the CM voltage. A physics-based model of the system was developed to simulate the conducted emissions and DM performance of the two proposed methods. As the CM voltage cancellation methods result in increased switching frequency, wide bandgap devices were used to build a laboratory prototype, on which the simulated results were successfully validated.