The Research On Harmonics Characteristics Of Single-phase Nonlinear Loads In Low Voltage Distribution System Base On Experiments

With the rapid development of power electronics technology and wide application of single-phase nonlinear devices, a severe influence has been made on power quality in low voltage distribution system. Experimental method is employed in this paper to study the harmonic characteristics of single-phase nonlinear devices in low voltage distribution system, and the experimental platform on which experiments to study harmonic characteristics of individual equipment, diversity and attenuation effect are carried is established, and the experimental schemes are set up correspondingly. Based on this, the harmonic characteristics of single-phase nonlinear devices and the effects on architectural electricity designing are studied. The main rresearch emphasises are as follow:①The spectrum characteristics, phase characteristics and the effects on low voltage distribution system of CFL, computer, laptop computer, microwave oven, television are studied according to the experimental measurements results of these nonlinear devices;②Referring to the operation status of the nonlinear devices mentioned above in residential and office buildings, these nonlinear devices are combined into several groups. The harmonic currents characteristics of each group and diversity effect resulted in the phase diversity of defferent devices are studied, and the conception of general diversity factors is proposed to describe the harmonic sources combination characteristics;③The CFL is selected to analyze the interaction between voltage and current through measuring its current waveform under different voltage backgrounds, and conception of crest factor is proposed, which is proved to be the evaluation parameter of attenuation effect instead of volage total harmonic distortion(VTHD);④The total powers and power factors of single-phase nonlinear devices are analysised according to the experimental measurements results, also, compairing with the power factors carried out in current design manual, the power factors of these devices are proposed for reference, besides, the current flowing through neutral line is studied when nonlinear loads considered, and the conception of zero sequence current ratio is proposed to describe the current relationship between phase line's and neutral line's; ⑤The harmonic characteristics studied above are applied to architectural electricity designing, and the the defects of current design methods and principles are pointed out, based on which, improvement suggestions for architectural electricity designing in residential and office buildings are proposed.This paper lays a theoretical foundation for harmonic load prediction and elimination in low voltage distribution system, and provided a reference for establishing the architectural electricity designing principles in residential and office buildings, being of certain theory and the practical value.