Two PWM techniques for single-phase shunt active power filters employing a direct current control strategy

This paper presents a comparison of two pulse-width-modulation (PWM) control techniques applied to a single-phase shunt active power filter (SPSAPF) using theoretical and experimental validation methods. A direct current control strategy is implemented using a standard PWM (S-PWM) and a modified PWM (M-PWM) in order to compensate the current harmonics and the reactive power generated by a nonlinear load. The M-PWM technique is based on two comparisons of a triangular high-frequency carrier signal with a low-frequency modulating signal (which represents the load current harmonics) and its opposite. The M-PWM shifts the first significant harmonic rays towards twice the switching frequency and eliminates the spectral rays that are centred around the odd multiples of the switching frequency. The simulation and experimental results are presented with a view to determine which of the M-PWM or the S-PWM performs better in terms of source current total harmonic distortion and reactive power compensation.