Grounding Strategies in the Hybrid Microgrid

A hybrid microgrid (MG) combines both AC and DC MGs using a bidirectional interlinking converter (IC). In a hybrid MG, grounding both the AC and DC MGs is done using isolated converters or low-frequency transformers. However, low-frequency transformers complicate the converter design, and high-frequency transformers reduce efficiency. Consequently, non-isolated ICs are often preferred in hybrid MGs. The grounding of non-isolated hybrid MGs is a complex issue that requires ongoing research and attention. Comprehensive knowledge of the available AC and DC MG grounding strategies and their effects is essential for designing, operating, and protecting the hybrid MGs. This paper develops a holistic grounding strategy for hybrid MGs, which incorporates AC and DC sections as well as ICs between AC and DC buses. Line-to-ground (LG) fault detection and protection, service continuity, common mode voltage, leakage current levels, system reliability, transient LG fault current magnitude, personnel/equipment safety, and insulation requirements are thoroughly examined by comparing different grounding strategies.