An Inductively Filtered Multiwinding Rectifier Transformer and Its Application in Industrial DC Power Supply System

A Four-Winding Inductive Filtering Transformer to Enhance Power Quality in a High-Voltage Distribution Network Supplying Nonlinear Loads

“…The three-phase construction of the FW-IFT, which consists of the primary, filtering, secondary, and tertiary winding connected to 220 kV alternative current (ac) grid with passive filters of 35 kV, 110 kV, and 35 kV nonlinear loads, respectively, is described in Figure 4a. As long as the equivalent impedances Z K4,12 and Z K4,13 are approximately equal to zero, the FW-IFT will satisfy the IF condition [21]. So the single-phase equivalent circuit model of the FW-IFT is a radial circuit, where includes the short-circuit impedance Z K14 , and equivalent impedances Z K4,23 , Z K2,34 , Z K3,24 , as shown in Figure 4b.…”

“…This proves that the proposed IF method is capable of improving the filtering performance, eliminating harmonic amplification phenomena, and compensating for the current harmonic contents produced from the nonlinear load. = , which can satisfy the inductive filtering condition [21]. From Equation (6), it can be seen that the content of the harmonic currents in the primary windings is closely related to the grid-side system impedance sh Z , the short- The equivalent impedances of inductive filtering winding for a FW-IFT (Z K4,12 ,Z K4,13 ) should be designed to be approximately equal to 0; that is to say, Z K4,12 = 0, Z K4,13 = 0, which can satisfy the inductive filtering condition [21].…”

“…= , which can satisfy the inductive filtering condition [21]. From Equation (6), it can be seen that the content of the harmonic currents in the primary windings is closely related to the grid-side system impedance sh Z , the short- The equivalent impedances of inductive filtering winding for a FW-IFT (Z K4,12 ,Z K4,13 ) should be designed to be approximately equal to 0; that is to say, Z K4,12 = 0, Z K4,13 = 0, which can satisfy the inductive filtering condition [21]. From Equation (6), it can be seen that the content of the harmonic currents in the primary windings is closely related to the grid-side system impedance Z sh , the short-circuit impedance Z K14 , the fully tuned inductive filters' impedance Z Fjh and the grid-side voltage .…”

“…Since the IF method is different between active and passive filtering methods, it is the preeminent solution against nonlinear loads, which it achieves by fully utilizing the electromagnetic inductive filtering principle of the transformer, which is applied in the industrial direct-current (dc) supply system and high voltage dc system [20][21][22]. For the four-winding inductively filtered rectifier transformer (FW-IFRT), the ratings of the wye-connected bank of secondary winding of the load side and the delta-connected bank of tertiary winding of the load side are selected to be same, permitting the cancellation of 5th and 7th order characteristic harmonics, while only containing 11th and 13th order characteristic harmonics at the grid side [21]. However, for the FW-IFT, the 5th, 7th, 11th, and 13th order characteristic harmonics still exist in the grid side because of the voltage level and load rating capacity of the medium voltage (MV) and low voltage (LV) sides.…”

“…to zero, the FW-IFT will satisfy the IF condition[21]. So the single-phase equivalent circuit model of the FW-IFT is a radial circuit, where includes the short-circuit impedance 14 K Z , and equivalent impedances 4,23 K Z as shown inFigure 4b.…”