Closed-loop control for a single-phase cascaded multilevel inverters operating with SHE-PWM

Abstract

This paper presents the development of a control approach for single-phase cascaded multilevel inverters employing Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM), a low-frequency modulation technique to reduce harmonic content by means of the elimination of low-order harmonics. After determining the switching angles for a range of modulation indexes, a closed-loop control strategy is proposed for regulating the peak current at the output. An alternative feedback strategy for this single-phase system is presented, which match the AC signal of output current to the DC input of the modulator. Simulation results validate the proposed control system for load and reference variations, while the elimination of desired harmonics is confirmed by spectral analysis over time.