Using SHM-PWAM modulation technique for three-phase four-leg active power filter

In this paper, a selective harmonic mitigation (SHM) strategy based on the pulse width and amplitude modulation (PWAM) concept has been proposed for three-phase four-leg shunt active power filters (APF). The pulse amplitude modulation (PAM), which is mainly used in communication systems, is applied simultaneously with the PWM to the three-phase four-leg inverter. This leads to an increase in the system degrees of freedom in mitigating more harmonics compared to the conventional PWM-based strategies. The control signals of three legs, mathematically expressed using Fourier-based equations to mitigate lower order non-triple harmonics, and the fourth leg produces the harmonics that are equal to the lower order triple harmonics which produced by the other legs. Simulation results show the priority of the SHM-PWAM technique over the conventional SHM-PWM from the THD point of view.