The Research On Capacitive Characteristics And Attenuation Effect Of The Single-phase Diode-bridge Converter-base Loads

Recently, the single-phase diode-bridge converter-based loads have rapidlyproliferated in residential areas. The single device has small power rate and high currentdistortion while the devices are distributed widely in the systems. When a large numberof harmonics inject into the power distribution system, it will result in serious distortionof supply voltage, and do harm to power system loads and the nearby electronic devices.Because of the filter capacitor, the circuit in each harmonic will be capacitive which willhave an effect on the reactive power compensation and may cause harmonic resonancewith the system inductive. In this paper, based on the frequency-domain model of thesingle-phase bridge rectifier filter circuit, the fundamental and harmonic equivalentcircuits were derived. Combining with the equivalent circuits, the capacitive andinductive characteristic of the loads were obtained through theoretical analysis,simulation and experiments. Then a comparative analysis of the relationship of theattenuation effect with wave crest factor，peak displacement factor was done throughsimulation and experiments. The specific work is as follows:①The fundamental equivalent circuit under the ideal voltage and the harmonicequivalent circuit under distorted voltage were derived based on the frequency-domainmodel.②According to the fundamental equivalent circuit, the characteristic of thefundamental equivalent admittance and the phase difference of the fundamental currentand voltage were analyzed by theory. The results indicated that this type of loads alwaysshowed capacitive behavior and the leading phase-angles were concentrated in a narrowrange. Combined with the harmonic equivalent circuit, analysis of the current of eachbranch and simulation studies on the circuit were performed. The results showed that inthe case of different voltages or load parameters, the circuit could be capacitive orinductive. A method that could determine the range of circuit parameters which made thesingle-phase bridge rectifier circuit capacitive on different voltages was proposed. In thisway, the non-linear capacitive resonance which happened between the circuit and thesystem inductance would be prevented.③The relationship of the attenuation (amplification) with the wave crestcoefficient, displacement factor was analyzed through simulation. The results showedthat it would bring many errors if using only one voltage waveform index to reflect attenuation alone. Finally, combining the crest factor with peak displacement factor toreflect the attenuation (amplification) was proposed in this paper.