This manuscript presents an optimal modulation and systematic filter design approach for a single-stage DAB-based DC-AC microinverter to achieve improved differential-mode (DM) noise performance. As DM filters contribute significantly to the overall converter volume, the main objective of this work is to design a minimal volume DM filter to meet appropriate EMC standards. In addition, the DM filter design method needs to ensure near unity power factor converter operation. To achieve these targets, this paper analyzes three modulation strategies based on fixed or variable switching frequency operation where the different control modulation variables are varied to find the simulated DM noise spectrum. Based on the required DM attenuation, a constrained optimization problem is formulated to determine minimal DM filter parameters. Simulation results show that a spread spectrum approach with variable switching frequency is shown to minimize the DM EMI attenuation effort and thus the overall volume for the DM EMI filter.
