مشخصات پژوهش

The increasing use of power electronic loads in industry and consumers results in injection of the considerable amount of current harmonics to the distribution system. Current harmonics of nonlinear loads may be generating harmonic voltage drops due to the distribution system impedance. These harmonics cause unwanted effects like transformer overheating, over currents on neutral conductors, communications failures, errors in monitoring equipment and disorder in operation of other devices. One of the most important nonlinear loads is rectifier. Depending on the congestion of conversations, Base Transceiver Station (BTS) for mobile communication includes several single phase rectifiers to feed batteries and amplifiers with over five kilowatt rated power in Iran. There are more than 30000 BTS in Iran which inject large amount of current harmonics to distribution systems. In each BTS, there are various types of rectifiers which each of them has different circuit topology and injects different harmonics. In this paper, in order to comprehensive study, the stations with different types of rectifiers, various congestion of conversations and different distances from supply system were selected to measurement and analyze. Then, voltage, current, active power and power quality parameters of selected stations were measured using ION power analyzer devices and data were recorded. The results of measurement and analyze show that the power quality parameters in these stations are not in standard range and will be harmful to distribution systems. Depending on the harmonic spectrums of current in these stations, several methods are proposed to improve power quality parameters such as: using of suitable transformer in primary side, embedding and tuning passive filters to eliminate specific harmonics and using of renewable energy systems as off grid. Besides, one passive filter has been designed and implemented that reduces total harmonic distortion of injection current considerable.