Interactive Grid Interfacing System by Matrix-Converter-Based Solid State Transformer with Model Predictive Control

The back-to-back connection of two three-to-single-phase matrix converters (MCs) through a high-frequency transformer to create the so called MC-based solid state transformer (SST) for interactive grid interfacing is proposed in this paper. The solution provides single-stage bidirectional ac-ac power conversion. There are advantages of no lifetime-limited storage capacitors, light weight, and compact volume. The conventional modulation methods of this MC-SST system require additional control design for power management. Besides, space vector modulation contains sophisticated voltage and current vectors computation and duty cycle composition, considering the two back-to-back connected three-to-single-phase MCs. In this paper, a model predictive control (MPC) is proposed for this MC-SST linking different ac grids. The proposed MPC predicts the state variables based on the discrete model of MC-SST system and the present circuit variables, and then selects an optimal switching state that ensures the smallest value of a cost function, for the next sampling time. Simulation and experimental studies are carried out to demonstrate effectiveness and simplicity of the proposed MPC for such MC-SST grid-interfacing system.