Analysis and Modeling of Multi-mode Operation for Series-parallel CLLC Resonant Converter

The direct current converters will be the key device for DC power distribution to achieve flexible control and active management of voltage and power between the medium-voltage direct current (MVDC) distribution grid and the low voltage direct current micro-grid. This paper proposes a new control strategy for the dual-active-bridge (DAB) converters with CLLC resonant tank. Compared to traditional control strategies, three modes of operation are in the new strategy to achieve bidirectional transmission of power and voltage control. Each mode of operation provides an accurate modeling analysis process to obtain a small-signal model. Series voltage balance and parallel power balance of the resonators are theoretically equivalent. In addition, distributed, modular, and plug & play design strategies also can be easily applied for the converter. The simulation results verify the effectiveness of the analysis and modeling.