DSP-controlled active filters for system harmonics compensation

This paper presents the design and development of transformer-less series active filter, shunt active filter and unified power quality conditioner for harmonics compensation in a low-voltage ac system. The topology is based on a single-phase voltage source inverter (VSI) with four, IGBT switches for series and shunt active filters. Simple time-domain extraction technique is used to determine the harmonic components present in the source voltage and load current. The pulse width modulation technique is used to generate the required gate drive signals to the VSI. Both the control and extraction techniques are carried out using real-time digital signal processing (DSP) techniques. The combination of series and shunt active filters to work as a unified power quality conditioner using DSP techniques for harmonics compensation is also presented. The experimental results show that the DSP-controlled series active filter, shunt active filter and unified power quality conditioner can significantly reduce harmonic distortions in the supply system.