A Tunable LCL Resonant Immittance Network Based Triple-Active-Bridge Converter Utilizing a Hybrid Modulation Scheme for Wide-Range High-Efficiency Operation /

Abstract

Triple-active-bridge (TAB) converter is a promising solution for coupling multiple energy sources and loads in transportation electrification and power grid applications, but it suffers from switching and conduction losses which degrades its efficiency performance. In this regard, topology morphing, and hybrid modulation scheme can be an effective solution to achieve high-efficiency operation of a TAB converter. With this motivation, a novel topology and hybrid modulation scheme for a triple-active-bridge (TAB) converter employing a tunable LCL resonant immittance network is proposed in this paper to achieve wide-range high efficiency operation. By virtue of a tunable LCL resonant immittance network employing switch-controlled capacitor (SCC), the resonant frequency of the immittance network can be effectively controlled that allows to achieve full range zero-voltage switching (ZVS) and minimize the circulating currents at all ports of the TAB converter. The hybrid modulation combines dynamic frequency modulation (DFM) for high-to-medium power operation and conventional dual-phase-shift (DPS) modulation for medium-to-low power operation. With DFM, the resonant frequency of the tunable LCL network is dynamically adjusted by using SCC to the switching frequency, allowing ZVS operation and near zero circulating currents within its operating power range. For medium-to-low power range, the converter is operated with DPS modulation to achieve ZVS operation with minimum circulating currents. The combination of both operation modes ensures high-efficiency operation of the TAB converter with flat efficiency curve throughout entire operation range. The performance and effectiveness of the proposed solution is verified by extensive simulation and experimental results and compared with the previously proposed state-of-the art solutions