Generation of voltage fluctuations in power systems with DC arc furnaces

There is an increasing use of high-power DC arc furnaces for scrap melting all over the world. Onsite measurements in several steel plants with these furnaces have shown that flicker relevant voltage fluctuations cannot be prevented. The first reason is the time-varying need of reactive power. Also dynamic compensators like TCRs are often not able to avoid considerable flicker, particularly in cases of small network short-circuit capacities. Another flicker origin is the existence of interharmonics. Together with the converter-characteristic harmonics, these interharmonics may result in difference frequencies in the flicker-relevant range. In the paper, the general interactions are explained and a calculation program is presented for the simulation of the power quality conditions in the electric power supply system.