Electric arc furnace compensation using LaGrange minimization

Electric Arc Furnaces (EAFs) are generally moderated by ancillary compensation to remove the time-varying reactive component from the utility load; the compensation strategy is fundamentally based upon an application of the Clarke transformation which does not use the zero component; as a result, the highly unbalanced EAF currents have a component that remains uncompensated. The present work uses LaGrange minimization to determine inactive currents that are then used to direct a Static Compensator (STATCOM). Where there is significant unbalance, the technique results in reduced line currents and improvements to the magnitude and stability of power delivered to the arc. The real power delivered by the STATCOM under the LaGrange technique is zero; where there is no line imbalance the results are identical to those produced by use of the Clarke transformation. The LaGrange scheme is compared directly to the Clarke transformation-based compensation scheme by the use of a PSCad model.