Study on Characteristic Parameters of Short-Circuit Impedance for a Four-Winding Inductive Filtering Transformer in Power System Supplying Nonlinear Loads

Different from a three-winding transformer and ac passive filtering method, this paper proposes an inductive filtering (IF) method with a four-winding inductive filtering transformer (FW-IFT) for power system supplying nonlinear loads. Based on this, the characteristic parameters of the short-circuit impedance for the FW-IFT are studied in detail by theoretical analysis and experimental verification. According to the single-phase equivalent circuit, the voltage equations of the FW-IFT are established at the fundamental and harmonic frequencies. By short-circuit test, the constraint condition of the inductive filtering is obtained, which can satisfy the demand of nonlinear loads in power system. Then, the influences of the filter impedance on characteristic parameter of the short-circuit impedance are analyzed and calculated. The detailed theoretical calculation and the experimental results verified the feasibility and correctness of the aforementioned theoretical analysis and calculation.