Two-stage Input-Output Feedback linearization controller for AC-AC converter-based SST

Abstract

Classical transformers are the most important constituent of the power system and act as a passive interface between high voltage and low voltage systems. They have undesirable characteristics such as poor voltage regulation, large size/weight, sensitivity to harmonics, and poor power flow control. Solid-state Transformers (SSTs), are an emerging power electronics-based technology, sought to replace classical transformers after a century. SSTs are equivalent to a classical transformer with embedded desired functionalities. In this paper, three-phase AC-AC converter with capacitor at the DC-link is employed as power electronic interface in MV and LV side of the SST. Input-output feedback linearization (IOFL) controller is used to control the AC-AC based SST in two stages for controlling the external and internal states. AC-AC SST is linearized by the input-output feedback linearization technique where an internal dynamics is observed. IOFL is used to control the internal dynamics and second stage of the controller in the outer loop. Simulation studies are realized to confirm the applicability of IOFL controller and the control method.