A Study of Combined-type Active Filter using Linear Power Amplifier

Abstract

In recent years, along with the increase of the power converter used in home information equipments and home electric appliances, the harmonic current in the single-phase utility line generated from the converter causes a problem to electronic equipments. An active filter is one of the effective solutions for this problem. But the conventional type active filters utilize voltage source PWM inverter, which requires high switching frequency in order to compensate high order harmonic current in general. Using high switching frequency, this type inverter generates the electromagnetic noise and gives interference to other electronic equipments. So we propose the new type active filter using linear power amplifier with no switching operation. We have already reported that this type of active filter is useful for suppressing the higher harmonic current effectively. However the efficiency of this type active filter is very low. So we study on the reduction of the capacity of linear power amplifier by using combined type active filter in this paper. By combining the active filter that used linear power amplifier, and a partial-switching type active filter operating at low switching frequency, we show by theoretical and experimental results that the proposed active filter is effect to suppress the higher harmonic current in a single-phase utility line.