Real-Time Solution and Implementation of Selective Harmonic Elimination of Seven-Level Multilevel Inverter

This paper proposes a new method to calculate switching angles in selective harmonic elimination technique. It is introduced as a substitute for Newton-Raphson method and similar iteration methods. By utilizing classical control such as the proportional-integral (PI) control, the proposed method can perform a real-time calculation for multilevel inverter's (MLI) switching angles over a wide range of modulation indexes. Therefore, it is able to respond to system dynamics without the need to store precalculated large lookup tables. The proposed method is applied to seven levels cascaded full H-bridge to eliminate its third- and fifth-harmonic contents from the modulation index 0.1 to 1.04. The same procedure can be extended to the vast majority of MLI topologies. A Simulink model is built to simulate and validate the accuracy, dynamics, and continuity of the solution generated by the proposed method. An experimental prototype is also built and its results are discussed to confirm the theory and simulation of the proposed method.