This paper discusses the steady-state operation of
phase-shift modulated dual-bridge series resonant converter
(DBSRC) intended for dc/dc power bidirectional control over a
wide range of input and output voltages. The analysis, developed
here for the most general case of three independent phase-shift
control angles, demonstrates the existence of minimum current trajectories
in the 3-D control space along which the DBSRC cell can
deliver any admissible power level with minimum tank circulating
current. At nonunity conversion ratios, minimum current operation
prevents the DBSRC output bridge from experiencing severe
hard-switching losses, substantially reducing the effort normally
required by auxiliary zero-voltage switching assistance circuitry,
and outperforming the efficiency of conventional one-angle modulation
approaches especially at light load. The developed approach
is validated via computer simulations and experimental tests on
a 1-kW DBSRC prototype. Tests performed at a nonunity voltage
conversion ratio indicate a marked light-load efficiency improvement
with respect to the conventional one-angle modulation, confirming
the importance of the minimum current operation when
the converter is expected to operate with programmable output
voltages or under wide input voltage variations
PHEV/EV DC charging infrastructure attracts more and more attention recently. High power isolated bi-directional DC-DC converters provide galvanic isolation, V2G capability and reduce the cost and footprint of the system. Maintaining high power efficiency in wide vehicle battery pack voltage range is required. Three full bridge based high power bidirectional DC-DC converters are conceptually designed for this application and their advantages and disadvantages are addressed. Experimental test bench is built and efficiency evaluation for bi-directional operation is reported.
This paper treats ground faults in mixed DC and AC systems. Grounding methods affect commonmode voltage and circulating currents under normal conditions. Ground faults produce fault currents and systemwide offsets throughout the system with respect to ground. During ground fault transients, the aggregate bus-to-ground ground capacitance and inductance produce underdamped oscillatory overvoltages. Continuous operation under DC or AC offset affects component selection.
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