The Principle and Calculation of AC-side Ground Resistance of Three-phase Converter through DC Insulation Monitoring

The three-phase AC/DC converter (TPC), usually installed with a DC insulation monitoring circuit (DC-IMC), measures the grounding resistance at the DC side through grounding current. However, grounding resistance at the AC side will also affect DC-IMC. In this paper, based on the signal injection-based insulation monitoring, ground resistance of one phase at the AC side was studied for grid connected TPC and off-grid TPC. Moreover, a calculation method of AC-side ground resistance was proposed by analyzing the relationship between operating process and grounding current, and finally theory and method proposed in this paper were verified through experimental data.