The focus of this study is on the design of a full-bridge unidirectional resonant LLC Solid State Transformer. The proposed topology uses a high-frequency transformer to optimize the size and weight of the converter. This converter has the capability of operating at fluctuating load conditions while it keeps the voltage regulated in different operation point. The converter is designed to maintain soft switching by using a resonant circuit in this design to minimize the switching loss of the high frequency converter. ZVS in the leading leg for turn on mode and ZCS commutation in the lagging leg for all of the modes are achieved in the H-bridge through the suggested circuitry which is analyzed mathematically in detail in this study. A combination of Pulse frequency modulation (PFM) and Phase Shifting Modulation (PSM) are utilized to control this resonant converter. The experimental setup for the suggested configuration was implemented and the results of the simulation and calculations have been verified with test results. The hardware set up was tested with two different power levels and the output results confirm that the control method works properly to feed the load and keeps the converter working in the expected frequency range and maintainingmore »
Design and Implementation of a LLC Resonant Solid State Transformer
In this study, analysis and control of a highly efficient, high-power full-bridge unidirectional resonant LLC solid-state transformer (SST) are discussed. A combination of pulse frequency modulation and phase-shift modulation is utilized to control this resonant converter for a wide load range. The converter is designed to maintain soft switching by using a resonant circuit to minimize the switching loss of the high-frequency converter. Zero-voltage-switching (ZVS) is achieved for the H-bridge converter. The ZVS boundary for the proposed combined control method is also analyzed in detail. The experimental setup for the suggested configuration was implemented, and the performance of the proposed control scheme and resonant LLC SST have been verified with test results. The proposed combined control scheme improves control performance. The obtained results show that, the proposed system can regulate output voltage and maintain soft switching in a wide range of load. Thus, the efficiency of the system is improved and an efficiency of 97.18% is achieved.
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