An Inverter-Based Flexible Microgrid Grounding Scheme

Due to multiple operation modes and corresponding mode transitions of microgrids (MGs), the MG grounding design is challenging. An MG may lose its grounding provided by the main distribution grid when it transitions to the islanded operation, resulting in potential hazards to both equipment and personnel. Existing transformer-based grounding schemes are bulky and have low control capability, which leads to poor transition performances and may affect the operation and protection of the whole distribution grid in the grid-connected mode. Power inverters have been applied as interfaces of distributed energy resources (DERs), which can potentially serve as groundings for future MGs. In this article, a novel DER inverter-based MG grounding scheme is proposed to realize flexible grounding in MGs. The detailed grounding structure and control methods are discussed. The proposed grounding scheme is verified on a realistic MG model through simulation. The proposed control strategies are demonstrated on a converter-based hardware testbed.