Common-Mode Current Analysis and Cancellation Technique for Dual Active Bridge Converter Based DC System

This article presents an active neutral point clamped (ANPC)-based parallel dual-active bridge (DAB) architecture which combines
dv/dt
cancellation and power sharing in order to reduce electromagnetic interference (EMI) caused by common-mode (CM) current. High
dv/dt
associated with wide bandgap devices causes high CM current mainly due to parasitic capacitances. The corresponding conducted EMI can remarkably reduce the reliability of power converters and other onboard systems. This issue becomes worse due to higher dc bus voltage trend in electric vehicles (EV) and other dc systems. Conventional techniques struggle to provide attenuation in a wide frequency range. The problem can also be severe in soft-switched DAB converters as they operate at relatively higher frequencies. In this article, initially, an in-depth theoretical analysis is provided to understand the complimentary
dv/dt
events. Various factors causing nonideal
dv/dt
cancellation are discussed in detail together with possible solutions. Detailed experimental results are obtained from a 1100 V–150 V parallel DAB system including both the high and low voltage sides at different
dv/dt
rates.
dv/dt
cancellation at lowered
dv/dt
rates facilitated by power sharing and small snubbers provide up to 25 dBuA reduction in CM conducted EMI. A comparison with CM chokes is also presented to validate improved attenuation in a wide frequency range.