DC Microgrid Grounding Impact on Power Electronic Interfaces in Fault Condition

This paper deals with assessment of grounding systems impacts on power electronic interfaces. To this end, transient overvoltage and overcurrent are analyzed in different fault situations considering various grounding conditions from the power electronic switches point of view. A new model for a neutral point clamped power electronic interface is presented that is suitable for this assessment. Plenty of simulations are carried out; from their results one can offer some valuable comments regarding ground condition impacts on the transients. It will be confirmed that grounding resistance and structure of dc microgrids have considerable impacts on the transients experienced by power electronic switches. The permissible range of the grounding resistance and the worst states of the switching template from transient voltage and current aspects are determined. By real-time monitoring of the grounding resistance and taking into account the simulations outcomes, one can alleviate transients experienced by the switches and promote fault ride through capability of the converter. Since computational burden of the proposed simple model is relatively low, it is applicable in real-time monitoring of the ground systems in practice.