Abstract：When the transformer was closed at no load, the primary winding would generate a large amplitude of inrush current, which adversely affected the transformer and the stable operation of the power grid, and even caused the relay protection device to malfunction. In this paper, the mechanism of inrush current was analyzed. Based on the inrush current suppressor composed of an anti-parallel thyristor and a filter circuit, an inrush current suppression method was proposed. The odd-order harmonics were mainly generated during the anti-parallel thyristor conduction. Based on this characteristic, the filtering effects of a high-order damping filter and a high-order damping trap filter were compared. The high-order trap circuit with RC resistance-capacitance damping was selected as the filter in this paper, and its parameters were optimized. Then, the anti-parallel thyristor was connected in series with the filter, and the closed-loop feedback control of the terminal voltage was used to construct the inrush current suppression scheme based on soft starter. The active suppression of the inrush current was realized by the smooth start of the transformer terminal voltage. Based on Matlab/Simulink, the inrush current suppressor of three-phase transformer groups and three-phase three-column transformer under different wiring modes was established to verify the effectiveness of the proposed method.
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2020, Vol. 35 
