Three-phase inverter with output LC filter using predictive control for UPS applications

The total harmonic distortion (THD) plays a major role in determining the quality of the inverter output waveform. The use of an inverter with an output LC filter allows for generation of sinusoidal voltages with low harmonic distortion. Several control schemes have been proposed for the control of three-phase inverter. This paper presents a new and simple control scheme using predictive control. The controller uses a discrete-time model of the system to predict the behavior of the output voltage for all possible switching states generated by the inverter. Then, a cost function is used as a criterion for selecting the switching state that will be applied during the next sampling interval. A simple estimation of the load-current can be calculated from filter-current and output voltage. Therefore, there is no need of internal current-control loops and no modulators; the gate-drive signals are generated directly by the control. The simulation results under linear and nonlinear loads are presented, using Matlab/Simulink tools, verifying the feasibility and good performance of the proposed control scheme. Finally, the effect of error in system parameters values are presented.