Phase-Shift-Controlled Isolated Buck-Boost Converter With Active-Clamped Three-Level Rectifier (AC-TLR) Featuring Soft-Switching Within Wide Operation Range

Abstract

An active-clamped three-level rectifier (AC-TLR) is derived from the diode-clamped three-level inverter, by replacing the active switches and the diodes in the three-level inverter with the diodes and active switches, respectively. Novel isolated Buck-Boost converters, featuring single-stage conversion and soft-switching within wide operation range, are developed based on the proposed AC-TLR. By utilizing the AC-TLR, the voltage stress on the power devices and passive components, including the rectifying diodes, the active-clamping switches, the flying capacitor and output filter capacitors, is reduced to the half of the output voltage. Low voltage rating switching devices with better switching and conduction performances, and a transformer with reduced turns ratio and parasitic parameters are used to enhance the efficiency. The full-bridge isolated Buck-Boost converter with the proposed AC-TLR is analyzed in detail as an example. An optimized phase-shift control strategy is employed to realize isolated Buck and Boost conversion. Soft-switching of all of the switching devices in both the primary and secondary-side circuits is achieved within the whole operation range by using the proposed AC-TLR and the phase-shift control strategy. Experimental results on a prototype with 380V output verify the effectiveness of the proposed AC-TLR and its derived isolated Buck-Boost converters.

Topology and Control Strategy of PV MVDC Grid-Connected Converter with LVRT Capability

“…Isolated boost has strong boosting capacity but cannot operate in low-voltage range. In the isolated buck-boost topologies [18,20], buck and boost modes are achieved by coordinated control of active switches of the primary and secondary sides. The output voltage cannot reach MV level.…”

“…The cascaded two stages decrease the efficiency and increase the cost of the converter. The semi-active rectifier-based isolated buck-boost converters are developed in [18,19]. A three-level full-bridge isolated buck-boost converter is proposed in [20] to increase the output voltage.…”

Minimum-Output-Current-Ripple Control of Current-Fed Three-Level Phase-Shift Full-Bridge Converter

“…She proposed a hybrid TL-PSFB converter to accommodate a wide range of output voltages by adding a clamp inductor on the AC side, and the converter has good soft switching performance [23]. Soft switching of the secondary diode has also been noticed in the literature [24][25][26]. In addition, some scholars have done some improving research on the topology in some other aspects.…”