Interharmonic Compensation and Voltage Flicker Suppression with Cascaded STATCOM in Renewable Energy Based Weak Grid

Voltage flicker, one of the significant power quality issues, is caused by the injection of interharmonic currents. It will be more critical in renewable energy based weak grid. In this paper, a delta-connected cascaded static var compensator is employed to compensate the interharmonic currents produced by a three-phase electric arc furnace load, simultaneously suppressing the voltage flicker. The actual interharmonic load currents acquired from an industrial site are analyzed and their influence on the voltage flicker is revealed. The compensation strategy including the current command extraction, voltage and current dual close-loop adjustment, and the capacitor voltage balance algorithm, is elaborated in detail. Different simulation results are carefully designed and compared with different parameters of the low-pass filters in the current command extraction process, as well as variable grid impedance values.