Isolated AC/AC Converter With LLC Resonant Converter High-Frequency Link and Four-Quadrant Switches in the Output Stage

Abstract

An AC-AC converter with a high-frequency link employing an LLC resonant converter operating in the vicinity of the resonance frequency was studied, in which a single output power stage is used, formed by a high-frequency AC-AC converter employing four-quadrant switches. The topology, its operation and the modulation strategy are described. The high-frequency stage switches located on the primary side of the transformer operate with soft switching of the ZVS type, while the four-quadrant switches that form the output stage operate with soft switching of the ZCS type. Experimental data obtained with a 1.5 kW experimental prototype (input 220 VRMS, output 220 VRMS and switching frequency 40 kHz), which was designed, built and tested in the laboratory, are reported herein. This converter can be considered a candidate for the building block of medium voltage solid-state transformers (SST) for power distribution systems.

Robust and low‐cost design of LLC‐type DC transformer in hybrid AC / DC nano‐grids to improve energy conversion ability

“…To show the superiority of the proposed DCT, the maximum efficiency, control complexity to ensure the desired M, and cost are compared with existing converters, as summarized in Table 2. It can be seen that by comparing with the converters in References 7,12,24,27‐33, the proposed DCT can ensure the highest efficiency while guaranteeing the simple control and low cost.…”

“…To deal with this issue, a high‐efficiency converter utilizing a half‐bridge LLC converter has been detailedly analyzed in Reference 30, which is hard to support the high power applications. A secondary‐side phase‐shift‐control is then introduced in Reference 31 to reduce the conduction loss at normal operation; four‐quadrant switches are ensured by the approach in Reference 32 to adapt the high‐frequency applications; the dual‐output LLC resonant converter is given 33 with the wide input voltage range. However, the systematic efficiency improvement becomes rather difficult for these resonant converters.…”

Family of single‐phase high‐frequency isolated AC–AC converters

“…The DAB converter is an interesting choice to provide high‐frequency isolation as in Qin and Kimball, 13 but this topology cannot provide a nearly unity input power factor. An LLC resonant converter with a high‐frequency link composed of a single output power stage is studied in Pacheco et al 15 Even though it can achieve input PFC, it requires bidirectional switches. A family of high‐frequency Z‐source ac–ac converters is proposed in Ahmed et al 28 Despite presenting low component count, the structures rely on bidirectional switches similar to Pacheco et al 15 Some of the secondary side switches still require dissipative snubbers to avoid voltage spikes, this being a significant drawback from the efficiency point of view.…”

“…However, the conduction losses in the semiconductors of the LV side are somewhat high. An ac–ac converter with a high‐frequency link employing an inductor–inductor–capacitor (LLC) resonant converter is analyzed in Pacheco at el 15 . to reduce the number of elements required by the topologies formerly presented in earlier studies, 6,13 but it relies on bidirectional switches.…”

A High Power Interleaved Parallel Topology Full-Bridge LLC Converter for Off-Board Charger

“…In the overwhelming majority of the planet, the automobile has been an extremely significant transportation vehicle [2,3]. Regrettably, in the recent century, the use of conventional vehicles has increased to the extent that it has caused environmental and human life hazards [4]. This is because these cars burn gasoline, diesel or natural gas, producing carbon dioxide (CO 2 ), carbon dioxide (SO 2 ) and oxides of nitrogen as harmful exhaust components [5].…”