Modulation of a Bidirectional DC-AC Converter for an AC Grid Interface in Bipolar DC Microgrids

MSc defense of Kyle McNeil

This thesis explores the integration of DC and AC grids through power electronic converters in LVDC distribution systems. Different three-phase DC-AC converter topologies are assessed for connecting a bipolar DC microgrid to the LV AC grid, focusing on addressing the challenge of ground leakage current due to converter common-mode voltage. Converter modulation methods are investigated to reduce common-mode issues and achieve balanced DC bus voltage. Simulations evaluate the performance of these methods, and a novel approach is proposed to simultaneously mitigate ground leakage current, achieve voltage balancing, and eliminate low-frequency DC voltage ripple. An experimental prototype of a three-phase DC-AC converter is built to validate the modulation techniques, offering insights and recommendations for future research.