Topology and Control Method of a Single-Cell Matrix-Type Solid-State Transformer

Abstract

Aiming at fulfilling the desirable features of compact structure, high efficiency, high reliability, and multifunctionality for the solid state transformers (SSTs), a single-cell matrix-type SST as well as its control method is proposed as the interface between the medium-voltage (MV) and the low-voltage (LV) levels for direct MV AC to LV AC conversion. To achieve zero voltage switching (ZVS) at both the MV and LV sides, a modulation scheme to construct the special resonant currents during the dead time by actively controlling the MV and LV side gate signals is implemented. Furthermore, the ZVS conditions of the MV and LV side bridges are analyzed, and system parameters are properly designed to ensure full range ZVS operation. A 1-kW SST prototype is developed to verify the functionality and effectiveness of the proposed methods. The experiments show that sinusoidal input and output, bidirectional power flow capability, and ZVS at both sides over wide input voltage and load ranges are achieved with the nominal efficiency of 96.1%. The experimental results match the theoretical analysis and the simulation results well.