EMI reduction with a soft-switched auxiliary commutated pole inverter

PWM-controlled power converters are increasingly used in the More Electric Aircraft (MEA). However, Electromagnetic Interference (EMI) is introduced due to the high dv/dt and di/dt slew rates of their fast-switching power devices. Though EMI is conventionally mitigated by adding filters that can be often heavy and bulky, a better solution would be to address it at source, in order to achieve higher power density systems. This paper investigates how soft-switching topologies can attenuate EMI by addressing it at source. Specifically, the auxiliary commutated pole inverter (ACPI) is employed to actively control the dv/dt of the output voltage. The effect this control has on the output voltage frequency spectrum is examined with analytical models. Subsequently, a control scheme is developed for regulating the output voltage to the desired waveform and simulation results are presented. A 1.4-kW ACPI phase-leg prototype is utilized for proof of concept. Reductions in the harmonic content of the output voltage are observed in the range of 1 to 20 MHz. It is expected that the ACPI can benefit from better EMI performance and can contribute to the overall effort of achieving high power density systems for MEA applications.