Current Based Model Predictive Control for DC Capacitor Optimization in Grid-Connected and Stand-Alone Nine-Level Packed U-Cell Inverter

摘要

This paper investigates the application of Model Predictive Control (MPC) for controlling the load current and balance capacitors voltages of a nine-level Packed U-Cell inverter in both grid-connected and stand-alone modes of operations. PUC inverter has the advantage of minimum manufacturing cost compared to other multilevel topologies, but it needs bulky dc capacitors. Therefore, this paper proposes the MPC as a proper solution to optimize the capacitors size of nine-level PUC inverter, which makes it more interesting for various industrial applications particularly for single-phase grid-connected devices. For this purpose, structure of nine-level PUC is firstly investigated in terms of switching states, advantages and disadvantages. Afterwards, MPC control method has been developed and designed based on the mathematical equations of nine-level PUC topology. The proposed control loop is thereafter simulated using Matlab/Simulink software and the obtained results prove the desired load current reference tracking and capacitors voltages balancing with optimized capacitance; while minimum Total Harmonic Distortion (THD) and low capacitors voltages ripple have been observed.