Two-Phase Current Injection Method for Single Line-to-Ground Fault Arc-Suppression With Revised STATCOM

To suppress the arc current in the single line-to-ground (SLG) fault in neutral isolated distribution network, a two-phase current injection method is proposed for the revised static synchronous compensator (STATCOM), as an extra function during the SLG fault. Therefore, the traditional roles of the dedicated passive coil or power electronic based arc-suppression devices can be taken by this multi-purpose STATCOM. This article first introduces the principles and the models of the arc-suppression current injection during SLG fault. Then, different options of arc-suppression current injection by the revised STATCOM are analyzed in terms of stabilizing the floating dc capacitor voltages of the cascaded H-bridges (CHB) converter. It is discovered that the two-phase current injection is the only viable option to maintain the floating dc capacitors voltages. Then, the arc-suppression current controller and the dc capacitors voltages controller are proposed, and the design process of the control parameters adapting to the varying transitional (grounding) resistances computed online is also introduced. The proposed methods are first validated by simulations. Then, an MVA-rating CHB converter prototype is constructed, and 10 kV feeder SLG fault and arc-suppression experiments are performed to demonstrate the effectiveness of the proposed method.