Modified PWM with indirect current control technique applied to a single-phase shunt active power filter topology

This paper presents and analyses a new indirect current control technique applied to single-phase shunt active power filter (SPSAPF) implemented with pulse width modulation (PWM) based on two comparisons to compensate harmonics and reactive power of a non-linear load. This method uses a residual signal constructed from the comparison between the supply current and the desired value. To evaluate its performance, we have compared it with the direct current control technique based on the classic demodulation. The PWM control technique adopted is based on two comparisons of a triangular high frequency carrier signal and the source harmonic current. This harmonic signal namely +v and its opposite value -v are used, at the same instant, in the comparison process to generate the gate signals for the semi-conductor devices. By using the averaging technique, the direct consequence of using this PWM technique is that the transfer function of the SPSAPF becomes a pure gain. Simulation results using power system blockset Toolbox PSB of Matlab show the performance of the new control algorithm for SPSAPF implemented with the PWM adopted and its capability to compensate harmonics and reactive power.