A Comparative Study of Two PWM Techniques for Single-Phase Shunt Active Power Filters Employing Direct Current Control Strategy

This paper presents an experimental evaluation of two pulse-width-modulation (PWM) control techniques applied to a single phase shunt active power filter (SPSAPF). 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 control technique is based on two comparisons of a triangular high frequency carrier signal with a low frequency modulating signal (that represents the load current harmonics) and its opposite. The M-PWM shifts the first significant harmonics rays towards twice the switching frequency, and eliminates the spectral rays that are centered on the odd multiples of the switching frequency. Furthermore, it is shown that, for a M-PWM, the losses of the active filter are four times smaller than when using a S-PWM. Simulation and experimental results are presented to verify the better performance of the M-PWM over the S-PWM in terms of the total harmonic distortion (THD) of the source current and the reactive power compensation