Title: Total Harmonic Distortion Reduction of 9-Level Packed E-Cell (PEC9) Inverter
Abstract: In this paper phase-shift PWM technique (PS-PWM) is applied to reduce total harmonic distortion (THD) of PEC-9 inverter and the results have been compared with the level-shift PWM method (LS-PWM). PEC-9 inverter consists of one voltage source, seven active devices and one DC-link which contains two capacitors where each of them must be balanced to one-quarter of Dc source to achieve nine output level. Active balancing method for capacitors was integrated with PS-PWM and the regulation was carried out through redundant switching states of PEC-9. Each output level of the inverter is produced via comparing a set of carrier waveforms with one reference signal. The PS-PWM and LS-PWM techniques have been applied for PEC-9 using MATLAB / SIMULINK program. With 5mH L-filter, the THD of LS-PWM was determined as 2.28%, while THD for PS-PWM was 0.34%.