Model-guided modulation for matrix-type ac-dc DAB converter considering ac-side capacitor voltage ripple

Abstract

The matrix-type ac-dc dual-active-bridge converter is a promising topology for single-stage ac-dc power conversion, recognized for its high power density, reliability, and efficiency. This converter uses small capacitance for the ac-side filter, typically ranging from a few to a dozen microfarads, to achieve a high power factor (PF) and optimize both power density and cost. However, the relatively small ac-side capacitance can cause noticeable capacitor voltage ripple during the switching cycle. This article presents a time-domain steady-state model to accurately characterize the steady-state behavior of the converter. The analysis reveals that the ac-side capacitor voltage ripple can substantially impact the performance of the converter, particularly by causing the front-end circuit to lose zero voltage switching (ZVS), thereby reducing efficiency and worsening electromagnetic interference issues. The steady-state model is then used in an optimized modulation strategy to determine the optimal control variables to ensure ZVS operation, realize PF correction, and enhance efficiency. Simulation and experimental results demonstrate the theoretical analysis and validate the findings. Specifically, using the proposed modulation method, compared to the modulation method that does not account for the ac-side capacitor voltage ripple, the efficiency at light-load and heavy-load conditions can be improved by over 11.21% and 2.66%, respectively.