Passive Hybrid Filter for Varying Rectifier Loads

Shunt passive filter suffers from inherent problem of getting into series and parallel resonance with power system components besides its inability to operate for diode rectifier fed load with large DC smoothing capacitor. Moreover their application has been considered inadequate for voltage fed type of harmonic producing loads, like diode rectifier fed Variable Frequency Drive(VFD), etc, and their compensation characteristics has been dominated by unknown source impedance, which poses problem in their design. On the other hand series passive filter has been found suitable for voltage fed type of harmonic producing loads but suffers heavily on account of poor voltage regulation at point of common coupling(PCC), and poor power factor(pf) throughout its range of operation. This paper proposes a new hybrid passive filter, which provides harmonic compensation at par with active filters, whose design is insensitive to source impedance, eliminate the chances of resonance over a wide spectra and reduces large variation of pf and terminal voltage with varying rectifier load. Besides these the topology also helps fast settling of transients and blocking of harmonics. The investigations are carried out to validate the performance of proposed passive hybrid filter with slightly detuned resonant points (corresponding to available component values), for effective and efficient operation under varying rectifier load conditions.