Enhancement of Power Quality and Controllability of Electrical Arc Furnaces Using UPQC

Electrical Arc Furnace (EAF) is large, nonlinear and time-varying load that affects power quality of the power system by producing many problems such as harmonics, flicker, current unbalance and low power factor. This paper proposes a modified Unified Power Quality Conditioner (UPQC) to reduce power quality problems of EAF and enhance its controllability. Harmonic reduction, power quality improvement and current balancing are some of the advantages of proposed system. Moreover, it can rapidly and precisely regulate the current of each phase at its optimal value, restrict the lasting short circuit currents and ignite distinguished arcs. In addition, fast restriction of short circuit currents as well as control of arc voltage by the proposed UPQC gives the opportunity of substituting special heavy-duty furnace transformers with more simple ones. Besides, connection of converters at the low voltage side of furnace transformer through two step-down injection transformers reduces the nominal rating of solid-state switches to the available ones. In this paper, the advantages of proposed system are verified by simulation of a test system in the MATLAB under various conditions.