Model Predictive Control of a VSI with Long Prediction Horizon

This work presents a Model Predictive Control (MPC) strategy for a Voltage Source Inverter (VSI) used in a three-phase Uninterruptible Power Supply (UPS) for critical loads. An MPC using continuous variables is proposed for solving this problem and the output of the controller is used as the reference voltage to be generated by a PWM modulator. The solution of this unconstrained MPC gives rise to an explicit solution that can be computed beforehand, allowing the prediction horizon to be easily extended. Therefore, the effect of the length of the prediction horizon over the system performance is also evaluated in the paper. This study addresses how this parameter should be chosen to minimize the error between the actual and the desired output voltage. The proposed control strategy has been tested on a simulated model of a UPS supplying a three-phase resistor load. This model has been developed using MATLAB/Simulink with PSIM software. The simulation results show that proposed continuous MPC controller achieves high performance and high degree of robustness.