University of Tabriz

About: University of Tabriz is a education organization based out in Tabriz, Iran. It is known for research contribution in the topics: Population & Nanocomposite. The organization has 12141 authors who have published 20976 publications receiving 313982 citations.

Three-Phase HFL-DVR With Independently Controlled Phases

Abstract: Conventional dynamic voltage restorers (DVRs) are connected to the power grid through power-frequency transformers. These bulky and costly transformers cause voltage drop and power losses. In this paper, a high-frequency-link dynamic voltage restorer (HFL-DVR) is proposed based on transformer-isolated topologies. This topology facilitates independent operation conditions for each phase in a three-phase system. It enjoys relatively low cost, low losses, and small size. Also, it is free from transformer inrush currents. Small-signal ac equivalent circuit for the power stage including HFL-DVR is derived based on an averaged modeling approach. Transfer functions are obtained to study the effect of inputs such as dc-link voltage, grid voltage, and the load current on the output of HFL-DVR. In order to obtain acceptable properties such as transient overshoot, setting time, and steady-state error, a PID controller is added to the system. This shows that the effect of disturbances on the output of HFL-DVR can be reduced. The experimental results are obtained from a 220V/50Hz HFL-DVR setup. The simulation and experimental results have been compared to verify theoretical aspect of the proposed DVR for both symmetrical and asymmetrical voltage sag conditions.

Electrochemical studies of Zn–Ni alloy coatings from non-cyanide alkaline bath containing tartrate as complexing agent

Abstract: The Zn–Ni alloys have been electro-deposited from a non-cyanide alkaline bath containing tartrate as a complexing agent for Ni 2+ ions. A water soluble polymer is used as a brightener. It was prepared by the reaction of epiclorohydrin with hexamethylenetetramine and mercaptobenzimidazol. Its effect on co-deposition process was examined. It was found that adding brightener in plating bath has a great effect on the cyclic voltammogram and galvanostatic measurements during the electrodeposition. Under the examined conditions, the electrodeposition of the alloys was of anomalous type. X-ray diffraction measurements revealed that the alloys consisted δ-phase (Ni 3 Zn 22 ). The composition and morphology of the deposits were also studied by using scanning electron microscopy (SEM) and energy dispersive analysis X-ray (EDAX), respectively. The effect of optimum plating bath conditions on the corrosion resistance is studied by Tafel polarization.