Investigation of resonance phenomena in power lines supplying powerful rectifier plants

Abstract

A feature of modern power supply systems is the presence of a large number of electrical devises that consume non-sinusoidal current. The examples of the devices are frequency converters or rectifiers of large unit power. But substations for supplying a group of variable frequency drives affect negatively also. Since the equivalent circuit of the power includes line inductive and capacitive elements, under certain conditions, resonant can occur in the power supply system. The model for studying a power supply system with a powerful rectifier load has been developed in the MATLAB + Simulink environment. The equivalent power line circuit is adopted in the form of a certain number of series-connected sections. The number of sections was chosen from the condition of obtaining information about all harmonics, which the electric power quality standard prescribes to analyze. The simulation results show the number of the harmonic at which the resonance occurs depends on the length of the power line. It has been found that at resonance, the maximum current harmonic circulates through the source. And at the end of the line in this moment, the current harmonic has a minimum value, while the corresponding voltage harmonic rises sharply.