Power Balance Control of Cascaded Matrix-Based Dual-Active-Bridge Converter

Though the merits of matrix-based dual-active-bridge (MB-DAB) as a grid-connected Solid-State-Transformer (SST) submodule have been presented in literature lately, its operation and control in the cascaded configuration have not been explored. The objective of this paper is to present the operation and control challenges of the cascaded matrix-based dual-active-bridge (CMB-DAB) in detail, from the perspective of the Medium-Voltage-AC (MVAC) to Low-Voltage-DC (LVDC) conversion stage of a grid-connected SST. Subsequently, the control strategy required to eliminate the unavoidable power imbalance issue is explained comprehensively. The simulation results are presented for a 7-level 52.65 kVA CMB-DAB converter to demonstrate the inevitable power imbalance issue and the proposed control strategy as a mitigation technique. The proposed power balance controller (PBC) is observed to perform smoothly in adjunction with the LVDC bus control and remediate power imbalances during steady-state as well as transient-states by adding suitable phase-shift correction terms.