Energy-efficient operation modes of a frequency converter with a series-parallel resonant circuit under power stabilization at a variable load

Abstract

An analysis of the power characteristics for a frequency converter is performed for matching with a varying load by means of a series-parallel resonant circuit. It is shown that a change in the active component of the load does not always lead to a proportional change in the input resistance of the resonance circuit, with at certain frequencies the resonant circuit even exhibiting a constant input resistance under a change in the load within a considerable range; that is, it has the properties of parametric output-power stabilization. At these frequencies, a large reactive component appears in the input impedance of the circuit, which does not allow one to obtain an operation mode close to a resonance one or achieve an acceptable energy-conversion efficiency. The frequency characteristics of the circuit have been studied under conditions of an extreme approach of its resonant frequencies. It is found that, in this case, owing to the distortions of the phase-frequency characteristic, one can obtain a quasi-resonant operation mode of the converter over the entire range of the load resistance. It is shown that the proposed method for the tuning of resonance circuit allows one, under a twofold change in the load, to achieve parametric stabilization of the output power with energy parameters of cosϕ > 0.94 at extreme points of the range of resistance variation. The obtained results are confirmed by simulation and physical experiment.