SVC and STATCOM application in Electric Arc Furnace efficiency improvement

Electric Arc Furnaces (EAF) are high power industrial loads which cause power quality problems at all voltage levels due to their unbalanced and nonlinear characteristics. The rapid, stochastic large swings in real and reactive power required by the arc furnace causes voltage drops, rapid voltage variation and distortion across the ac supply network. These voltage drops and fluctuations not only have negative impact on the power system quality and other loads, but also have an effect on the arc furnace operation, power output and efficiency. Hence, some sort of reactive compensation is required to limit the voltage disturbances injected by arc furnace into the electric power system. In this paper, an accurate electric arc furnace model, whose parameters have been set according to a 80 MVA actual arc furnace, is studied. A Static VAR Compensator (SVC) is simulated in PSCad and Real Time Digital Simulation (RTDS)/RSCAD platform for the purpose of comparison of voltage regulation at EAF bus. It is shown that the SVC mitigates the reactive power fluctuations in addition to providing the fundamental reactive power, and regulates the Point of Common Coupling (PCC) bus voltage precisely during the arc furnace operation. To verify the PSCad simulation results and make a comparison, a real time simulation study based on Real Time Digital Simulation (RTDS)/RSCAD platform has been performed in this case. On the other hand, a 80 MVA static synchronous compensator (STATCOM) is simulated in PSCad. It is illustrated that the SVC is inherently limited in its ability to respond rapidly to the fluctuating arc furnace load. It is found that the transient performance of the EAF voltage in case which equipped with the STATCOM is better than the case equipped with SVC. It is also demonstrated that although the voltage regulation by the SVC compensates a portion of the reactive power fluctuation, it is completely unable to supply any portion of the fluctuating real power drawn by the arc furnace, while the STATCOM can supply those components of active and reactive power fluctuation. The STATCOM will not normally have a source of real power connected to its DC terminals. It is therefore unable to supply sustained real power or real power fluctuations. With suitable choice of DC capacitor, however, it is capable of supplying in large part the fluctuating real power requirement of the furnace.