Influence of varying Common Mode Choke Sizes on the Performance and Stability of an Active EMI Filter

Power electronic converters generate conducted and radiated Electromagnetic Interference (EMI). An Active EMI Filter (AEF) is smaller in size, volume, weight, and cost than a similarly performing Passive EMI Filter (PEF). This paper proposes a Voltage Sense Current Inject (VSCI) Feedback (FB)-type AEF for Common Mode (CM) attenuation which can be installed at the AC-input of an 11kW On-Board Charger (OBC). The simulation model of a 4-phase (4 ph) Common Mode Choke (CMC) is presented, which is used to model the behavior of three different CMCs. Three AEF designs are compared to each other in terms of their performance, while a stability assessment for the AEF FB-loop is described which is based on the Nyquist stability criterion. It is shown that an AEF can reduce the CMC impedance by approximately 58% in comparison to a baseline PEF. This is verified by both simulation and experimental validation with a Vector Network Analyzer (VNA). The results of a transient Electromagnetic Compatibility (EMC) simulation for the Power Factor Correction (PFC)-stage underline the performance of the proposed AEF.