Abstract
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.
Highlights
With the growing scale of the distribution networks, its reliable operation becomes more challenging [1], [2]
The 10 kV revised STATCOM prototype consists of three cascaded H-bridges (CHB) phase legs, and each has cascaded twenty individual H-bridge cells
During the distribution system single line-to-ground (SLG) fault, it is necessary to suppress the arc induced by the parasitic capacitive currents from the two non-faulty phases
Summary
With the growing scale of the distribution networks, its reliable operation becomes more challenging [1], [2]. The arc current can be accurately compensated with reduced power electronic usage All these active ac-suppression options [17]–[20] connect to the neutral point of the feeder side of the transformer and dedicated dc sources are needed. Despite the complications from the unpredictable transitional resistances, the arc-suppression current (3) can still be safely used as the control target This would not completely compensate the whole capacitive current at the start, but it reduces the fault current and increases the neutral displacement voltage, so that the total capacitive current gets closer to the value defined by (3).
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