EMI Performance of Active Neutral Point Clamped Phase Leg for Dual Active Bridge DC-DC Converter

This paper evaluates the Electromagnetic Interference (EMI) caused by Active Neutral Point Clamped (ANPC) phase leg undergoing Zero Voltage Switching (ZVS). ZVS, together with a high fundamental frequency operation is encountered in Dual Active Bridge (DAB) converters. This allows ANPC phase leg to be operated in a different manner than its inverter counterpart. A comprehensive evaluation of four switching schemes for NPC/ANPC-DAB with regard to their EMI performance, voltage overshoot, and losses have been done. Switching state redundancies have been used to reduce the EMI of the ANPC phase leg. To further help in reduction of high frequency EMI and voltage overshoot, a low inductance busbar design has been presented for through-hole discrete devices. Finite element simulation and measurement results show a busbar inductance of 7.7 nH for long commutation loops. Finally, EMI performance (conducted and radiated) together with the busbar design have been experimentally validated for two of the most useful switching schemes. The switching schemes and the busbar design can boost adoption of NPC/ANPC-DAB by ensuring EMI compliance and improved efficiency without affecting the normal DAB operation or using additional hardware.