Asymptotically stable controller for SSTs based on Lyapunov direct stability method

Abstract

An asymptotically stable controller for solid-state transformers (SSTs) based on Lyapunov direct stability (LDS) method is presented in this study. The proposed controller has four control objectives for the SST application, which includes unity power factor at medium-voltage AC (VAC) side of the SST, constant DC-link voltage and constant output voltage magnitude and frequency at low-VAC side of the SST. To fulfil the above-mentioned objectives four control laws are derived from the Lyapunov function, directly. The proposed LDS-based controller is simulated using MATLAB/Simulink software. The obtained results indicate the fast and superior dynamic characteristics of the proposed controller. The LDS-based controller is comprehensive and can be adopted for the SST applications.