Conducted Common-Mode Electromagnetic Interference Suppression in the AC and DC Sides of a Grid-Connected Inverter

Electromagnetic interference (EMI) filters are inevitable parts of power electronic systems. A novel EMI filter for single-phase grid-inverter is proposed in this study, to suppress the common-mode (CM) EMI noise. The noise source and propagation path impedances are analysed, and the interaction between AC and DC side is studied. By connecting the ground terminal of the CM capacitors to the midpoint of the DC-link, the noise coupling between AC and DC side is reduced. When compared with the state-of-the-art of EMI filter, the proposed topology has advantages: the AC and DC filters can be designed independently; the impedance of the CM loop is improved; there is a remarkable CM EMI noise suppression effect on both AC and DC sides. Simulation and experimental results verify the theoretical analysis and proposed EMI filter structure.