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 »
A High Efficiency, Decoupled On-board Battery Charger with Magnetic Control
In this paper, a high efficiency, decoupled on-board battery charger is proposed. The proposed topology is composed of two LLC resonant converters sharing the same full-bridge inverter with constant switching frequency. The outputs of two LLC resonant converters are connected in series. One of the LLC resonant converters is operated at the resonant frequency, which is the highest efficiency operation point. The magnetic control is adopted for the second LLC resonant converter to fulfill the closed-loop control of charge voltage and current for constant voltage (CV) and constant current (CC) charge modes. The proposed topology can achieve zero voltage switching (ZVS) for all primary switches and zero current switching (ZCS) for all secondary diodes during both CC and CV modes. Furthermore, thanks to constant frequency operation, the electromagnetic interference (EMI) filter design is simplified. Simulation and experimental studies are presented to verify the feasibility and validity of the proposed topology.
- Award ID(s):
- Publication Date:
- NSF-PAR ID:
- Journal Name:
- International Conference on Renewable Energy and APplications
- Page Range or eLocation-ID:
- 920 to 925
- Sponsoring Org:
- National Science Foundation
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In this paper, a new topology for grid-connected solar PV inverter is proposed. The proposed topology employs an LLC resonant converter with high frequency isolation transformer in the DC-DC stage. The DC-DC converter stage is controlled to generate a rectified sine wave voltage and current at the line frequency. An unfolder inverter interfaces between this DC stage and the grid. Both phase-shift and frequency control methods are used to control the LLC resonant converter. The switching frequency is determined depending on the phase-shift angle to extend the zero-voltage switching (ZVS) region. The transformer leakage and magnetization inductances are also properly designed to provide ZVS for wide operation area. The LLC converter operates in the ZVS region except the narrow band around the zero-crossings of the inverter output current. Since the LLC resonant converter has a high frequency transformer, the line frequency transformer requirement is eliminated, and thus more compact and efficient design is obtained. The proposed topology is validated by the simulation and experimental results.
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