Leakage Current Modeling of Power Converter at IT Ground System

Abstract

Distributed power systems using solar power, fuel cells, and batteries require a PCS (Power Conditioning System) that converts DC voltage into AC power. However, parasitic capacitance (CP) occurs between the distributed power input module and the ground due to the structural characteristics and installation structure of the distributed power system. In order to reduce the leakage current generated by the PCS for distributed power generation, and since the leakage current is affected by the common mode voltage, the size of the common mode voltage can be reduced and the leakage current blocked by using the insulation characteristics of the transformer. However, in the IT grounding method using a transformer, the leakage current, which is a zero component, cannot pass through the transformer, but a leakage current path is created due to the parasitic capacitance (CT) existing inside the transformer. In addition to the transformer, a new leakage current path occurs through the cable impedance depending on the cable length, and the leakage current increases after adding cable impedance compared to not adding it. Therefore, in this paper, the validity of the equivalent circuit was verified by analyzing the before and after adding of cable impedance in the IT grounding method through PCS modeling and comparing it with the experimental results.