Impacts of Grid Impedance on Power Quality of Converters in Distribution Networks

Abstract

Motor drive systems consist of a diode-rectifier and a rear-end inverter which are used in a wide-range of industrial applications. However, power quality and harmonics in distribution networks can affect these diode rectifier-based systems. Previously, the effects of amplitude and phase angle of background voltage harmonics in distribution networks and their impacts on current harmonics have been explored. However, the grid impedance effects on the voltage and current harmonics are not considered in the existing literature. Therefore, this paper investigates the impacts of grid impedance on the voltage and current harmonics and the behavior of the three-phase diode-rectifier. Moreover, the mathematical analysis as well as simulation test have been carried out to validate the effects of the grid impedance on the power converter harmonics. The results indicate that for small values of grid impedance, both voltage and current harmonics do not change significantly, and the filtering effect is not significant; however, when the grid impedance increases, both voltage and current harmonics of the grid will be affected based on the commutation effects.