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
