Modeling of Common-Mode Voltage Source for Multilevel Inverter Topologies

Power converters are considered the major source of electromagnetic interference (EMI) in power conversion devices in electric vehicles and in more electrical aircraft. Several works study the impact of power converters on conducted emissions (CE), due mainly to common-mode (CM) currents, most of them with the traditional two-level inverter in power drive systems. An inverter is commonly modeled as a voltage source with input and output impedances. This paper presents an equivalent circuit of parallel and series multilevel inverters that can be used to analytically calculate CM currents. The method developed here, precisely estimates CM currents which is very important to prevent CM chokes to saturate and to fail on respecting standard limits.