Harmonic analysis of a capacitor‐filtered rectifier with line impedance

Abstract

AbstractAlthough the amount of harmonics generated from home electronic equipment such as televisions is small, the number of sets is large and they are used at the same time. Therefore, the harmonics generated from the power supplies of the electronic equipment is a cause of harmonic interference in the power distribution systems [1, 2]. In this paper, the input current of a capacitor‐filtered rectifier used widely as a power supply for electronic equipment is calculated with the impedance of the distribution system taken into consideration. As a result, an accurate expression became possible for the capacitor‐filtered rectifier current which had been treated by means of an approximate equation in the case where a line impedance, particularly inductance, exists [1, 2]. Also, an accurate prediction became possible for the current waveforms and harmonic behaviors according to the variations of the circuit parameters. The results computed as the parameters are varied indicate that the diode current path width, current waveforms and harmonic distributions, are strongly dependent on the inductance variation. The load circuits of a constant‐resistance type and of a constant‐power type were studied. As the inductance is increased, the harmonics are decreased whereas the amplitude and the average power of the fundamental wave are also decreased in the case of a constant resistance load. On the other hand, in the case of a constant power load, the amplitude of the fundamental wave tends to increase as the inductance is increased. When several of the capacitor‐filtered rectifiers are connected in parallel to a power distribution system, the amplitude of the harmonic cannot be evaluated by a linear sum of the harmonic contents of individual rectifiers.