Isolated seven-level inverter for grid-connected power systems with predictive control method

Abstract

A novel isolated 7-level (7L) multi-level inverter (MLI) topology for grid-connected medium and high voltage power applications is presented in this paper. The topology consists of two isolated transformers with different winding ratio and four switches connected to a single-phase grid. This topology provides a great advantage over conventional MLIs by reducing passive and active components to allowing a 7L output voltage. Moreover, model predictive control (MPC) method is implemented to 7L-MLI to generate gate signals of switches and ensure capacitor voltage balancing and grid connection. Performance of proposed topology has been confirmed by in-depth analysis under simulation and laboratory setup with existing studies. Experimental results of a 1.5 kW 220 V-rms prototype are presented to support the simulation results. The prototype shows that the harmonic results match the limits of the IEC 61000-3-2 standard and show a better performance for grid connection and capacitor voltage balancing than conventional ones.