An advanced modulation technique for the cascaded multilevel inverter used as a shunt active power filter

Abstract

Nowadays, the increase in the usage of non-linear loads especially the power electronic equipments leads to deterioration of the quality of voltage waveforms at the point of common coupling (PCC) of various consumers. Active power Filter (APF) has been used to mitigate the harmonic pollution in electrical networks. APF acts as an ideal current source and inject the compensating current into the ac lines by selective harmonic compensation in order to cancel the line current harmonics. A cascaded H-Bridge multilevel inverter has been used to realize the three phase shunt active filter. For the multilevel inverter a unipolar multicarrier PWM (MCPWM) technique is proposed. Since the harmonics are the most critical factor in selecting the control technique for the active power filters, the potential impact of the MCPWM techniques on the THD is investigated. The simulation is done in MATLAB/SEVIULINK software and the results show that with the proposed unipolar multi carrier technique, THD is reduced significantly in the over modulation region compared to conventional techniques and hence is employed in the realization of active filter.