Disturbance-observer-based model predictive control for output voltage regulation of three-phase inverter for uninterruptible-power-supply applications

In this paper, an offset-free model predictive control (MPC) method is suggested for regulating the output voltage of a three-phase inverter for an uninterruptible power supply (UPS) application through the multivariable design approach. A reference state, which satisfies the control objective of output voltage regulation, is derived. In addition, a one-step-ahead cost index penalizing the state tracking error is used by the proposed MPC. A disturbance observer (DOB) is used to compensate for the errors caused by uncertainties. Online optimization considering the input constraint of the inverter system is very simple, and no numerical method is required. It is shown that the proposed MPC makes the closed-loop system globally asymptotically stable in the presence of input constraints. The closed-loop performance is experimentally evaluated when resistive and resistive-inductive loads are used.