Family of single‐phase isolated high‐frequency transformer integrated improved magnetically coupled Z‐source ac–ac converters

Abstract

This study proposes single-phase improved coupled-inductor (CL) Z-source (ZS) ac-ac converters with integrated high-frequency transformer (HFT) isolation. They can provide wide range of buck-boost voltage with same/reversed phase angle, similar to the existing ZS ac-ac converters. Meanwhile, integrating a HFT with CL in proposed converters benefit in twofold: (i) the CL enhances the voltage gain, which in turn reduces the voltage stresses/ratings of active switches. Moreover, the turns ratio of CL add another degree of freedom to gain adjustment beside the duty ratio; (ii) the HFT (20 kHz) is integrated with CL by adding only one winding to the same magnetic core, which provides electrical isolation for applications such as dynamic voltage restore, saving extra bulky line frequency (60 Hz) transformer. In addition, the proposed converters provide both continuous input/output currents. The commutation strategy is also implemented to eliminate the switch voltage spikes. A proposed HFT isolated improved three-winding Δ-CL ZS (Δ-ZS) ac-ac converter is introduced at first, and its operation, circuit analysis and component design/selection are discussed in detail along with comparisons with counterpart converters. Various different CL structures based proposed HFT isolated ZS ac-ac converters are presented afterwards. Experimental results on 200 W prototype converter are provided finally to verify their merits.

A single‐phase q‐source AC‐AC converter with continuous input current, safe commutation feature, and reduced bidirectional switch counts

“…The minimum capacitances of capacitors and inductances of inductors are derived from the optimal current and voltage ripple values. The volume metric of the converter is calculated by (25) and (26) based on the energy stored in the inductor, coupled inductor, and capacitors.…”

“…An advance switching strategy for single and three‐phase AC‐AC converters has been introduced in Fang et al, 21 Li et al, 22 and Tang et al 23 to solve the commutation problem and eliminate the snubber circuit. The most popular impedance networks in single‐phase AC‐AC converters to operate in‐phase or 180° phase‐shift regarding the input voltage have been introduced 24–26 . Ahmed et al 25 have suggested a family of isolated single‐phase Z‐source AC‐AC converters.…”

“…The most popular impedance networks in singlephase AC-AC converters to operate in-phase or 180 phase-shift regarding the input voltage have been introduced. 24- 26 Ahmed et al 25 have suggested a family of isolated single-phase Z-source AC-AC converters. The topologies provide galvanic isolation and safe commutation features.…”

Optimization of Impedance-Source Galvanically Isolated DC–DC Converters With Reduced Number of Switches

“…In addition, D must be increased to achieve an HV gain; however, it causes HV tensions in network components [10]. Therefore, a variety of topologies for ZS-based DC-DC converters have been proposed using magnetic connection methods (e.g., methods that use transformers) to eliminate this problem, optimize voltage gain, and reduce voltage stress [11]. The current study primarily concentrates on ZS-based DC-DC converters with isolation transformers.…”

“…Based on Equations ( 5) and ( 8), the average value of the DC-link voltage between the power switches (S) (i.e., v pn.av ) can be computed as Using Equation (11), the peak output voltage of the Zsource impudence can be expressed as follows:…”