Topology and Control Strategy of an ISOP-LLC Cascaded with Buck Converter for Seafloor Observation Network

Le résumé fourni par la source

The power supply of seafloor observation network connection box needs to meet the core requirements of medium-voltage direct current (MVDC) wide-range input, high power density and resistant to load disturbance. Aiming at the issues of realizing wide-range input and complex input voltage sharing control that exist in traditional modular topology, this paper proposes an Input-series-output-parallel (ISOP) LLC cascaded with Buck converter topology and control strategy. The front-stage ISOP-LLC operates in DC-DC transformer (DCX) mode, and the voltage stress is reduced by connecting multiple converters in series, and the natural voltage sharing characteristics of ISOP-LLC are systematically analyzed by a small-signal averaging model with the same switching frequency of the submodules. To eliminate the effect of bus voltage fluctuation, Buck converter adopts a dual closed-loop control strategy introducing intermediate bus voltage feedforward to regulate the output voltage. A distributed voltage sharing control algorithm based on the submodule ring communication structure is designed to address the switching frequency offset of the LLC converter. The design of the converter with 9~15kV input and 375V/20kW output is accomplished, and the effectiveness of the proposed topology is verified by MATLAB/Simulink.

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