Novel Digital Controller for Multi Full-Bridge DC/DC Converter
Lusney, John Travis
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Distributed generation that utilizes 5-10kW Solid Oxide Fuel Cells requires power electronics to optimize the overall system efficiency while reducing the cost. The Adaptive Energy Zero-Voltage-Switching Phase-Shift-Modulated Full-Bridge (AE-ZVS-PSM-FB) topology meets these criteria under all loading conditions, but suffers from complexity associated with an analog control implementation. This thesis presents a novel Look-Up-Table (LUT) based digital controller required for such converter. The applied design approach also reduces the design time and controller requirements, which in turn decreases the overall system cost. Steady-state analysis for the AE-ZVS-PSM-FB converter is performed using a piece-wise equivalent circuit model. This analysis is used to verify the LUT concept that forms the basis for the proposed LUT-based digital controller. The proposed LUT-based digital control algorithm is developed and verified using Field Programmable Gate Array (FPGA) Logic platform. Design procedures and operational function under steady state and step change conditions are presented. Simulation results demonstrate the LUT concept in the AE-ZVS-PSM-FB converter, and the simplicity of the proposed LUT-based digital controller in producing the expected switching sequence. Simulation results were also produced showing successful dynamic response of LUT-based digital controller interconnected with the converter under different operating conditions. A Xilinx FPGA demonstration board was used to generate experimental switching sequence results to demonstrate the simplicity of the proposed controller.