Offset-Free Model Predictive Control for Output Voltage Regulation of Three-Phase Inverter for Uninterruptible Power Supply Applications

This paper proposes an offset-free model predictive control (MPC) method for output voltage regulation of the three phase inverter for an uninterruptible power supply (UPS) application. A use of a disturbance observer (DOB) is made to estimate the unknown disturbance caused by the load current and a plant-model mismatch. The proposed MPC optimizes the one step ahead cost function. The online computation considering the input constraint of the inverter system is very simple. It is shown that the closed-loop system is globally asymptotically stable in the presence of input constraints and that the integral action in the DOB eliminates the steady state errors caused by a plant-model mismatch. The effectiveness of the closed-loop system is experimentally shown under a use of resistive load.