A Four-Degrees-of-Freedom Modulation Strategy for Dual-Active-Bridge Series-Resonant Converter Designed for Total Loss Minimization

A Bidirectional LLCL Resonant DC-DC Converter With Reduced Resonant Tank Currents and Reduced Voltage Stress of the Resonant Capacitor

“…According to the same base value, ILa(norm), ILm(norm), and ILr(norm) of Bi-LLC can be shown in (18). Its intermediate variables a~d under n=1 are also listed in Table III By combining (17), (18), and Table III, when n=1 and g=1, the resonant inductors' normalized RMS current comparisons between LLCL and Bi-LLC in forward and backward modes can be totally shown in Fig. 13.…”

“…For LLCL converter, the current through La (iLa_F(t) in forward mode, iLa_B(t) in backward mode), Lm (iLm_F(t) in forward mode, iLm_B(t) in backward mode), and Lr (iLr_F(t) in forward mode, iLr_B(t) in backward mode) are all shown in (16). Based on (16), by taking the dc output current as the base value, the corresponding normalized RMS currents ILa(norm), ILm(norm), and ILr(norm) can be derived as (17). The intermediate variables a~d in (17) are listed in Table III.…”

“…Based on (16), by taking the dc output current as the base value, the corresponding normalized RMS currents ILa(norm), ILm(norm), and ILr(norm) can be derived as (17). The intermediate variables a~d in (17) are listed in Table III. According to the same base value, ILa(norm), ILm(norm), and ILr(norm) of Bi-LLC can be shown in (18).…”

“…To minimize the phase difference between bridge currents and voltages, thereby reducing the reactive power, LCL and CLC resonant networks are employed into DAB in [14] and [15], respectively. Based on series resonant converter [16], [17], a phase shift and modified pulse-width modulation strategy has been proposed in [16], which simultaneously reduce the resonant tank current and extend the ZVS range. In [17], zero reactive power, minimum tank current, and complete soft-switching are all achieved by modulating the internal, external phase shift and switching frequency.…”

“…Based on series resonant converter [16], [17], a phase shift and modified pulse-width modulation strategy has been proposed in [16], which simultaneously reduce the resonant tank current and extend the ZVS range. In [17], zero reactive power, minimum tank current, and complete soft-switching are all achieved by modulating the internal, external phase shift and switching frequency. However, since none of the topologies above can simultaneously obtain a wide soft-switching range, a simple control strategy and a good voltage regulation capability, compromises are often needed.…”