On the Design and Capacity of a Grounding Configuration for Grid-Connected DGUs

Established standards and industrial codes, for interconnecting distributed generation units (DGUs), address voltage and frequency changes, levels and quality of injected power, islanding conditions, and protection. However, these standards and codes do not clearly address the grounding configurations for grid-connected DGUs. One of the challenges related to the grounding configuration for DGUs is the harmonics generated by power electronic converters employed in DGUs. These harmonics can raise the ground potentials and disrupt the function of ground fault protection. This paper develops and tests a frequency-selective grounding configuration for grid-connected DGUs. The developed grounding configuration offers limiting ground potentials and ground fault currents, while imposing negligible impacts on the function of ground fault protective devices. The frequency-selective grounding configuration is designed and tested for two wind energy conversion systems and a photovoltaic system. Test results show that the developed grounding configuration achieves its objectives with negligible impacts on the grounded DGU and its ground fault protection.