Comparative study between active and hybrid power filters for power quality enhancement

Abstract

In this thesis a comparative study between a single-phase shunt active power filter, single phase shunt hybrid power filter and a three phase filter with series connection of passive and hybrid filter has been cited. Due to tremendous achievements on efficiency and regulation of power electronics devices their use has been increased. But in the same way they have become the sole cause of harmonic distortion affecting power quality of the system. Indirect control scheme having unipolar pulse width modulation (U-PWM) has been used in both single phase shunt active power filter (SPSAPF) and single phase shunt hybrid power filter (SPSHPF). The additional component used in a SPSHPF is a power factor correction capacitor (PFC) that is connected in series with a transformer. The voltage source inverter which is the main component of the filter, is connected with the primary winding of transformer. In indirect current control scheme extraction of reference source current is achieved from the distorted load current. The U-PWM technique is used for generating gate signals by comparing a high frequency triangular wave (carrier signal) with a low frequency regulation signal and it’s opposite. A combined environment of series attachment of a passive filter and a small rated active filter can have better compensation performance which has been used for a three phase supply. While the passive filter mitigates load produced harmonics the active filter helps to enhance filtering properties of passive filter. This ensures a great diminution of the rating of the active filter guiding to an economical practical system. The simulation of a typical distribution was carried out to validate the proposed filter techniques. It has been found that SPSHPF has a much better performance than SPSAPF. Also the series connected passive and active filter has effective harmonic mitigation quality.