A high-efficiency fuel-cell power-generation system with an active-clamp flyback–forward converter is presented in this paper to boost a 12-V dc voltage into a 220-V 50-Hz ac voltage. The proposed system includes a high-efficiency high-step-up interleaved soft-switching flyback– forward converter and a full-bridge inverter. The front-end active-clamp flyback–forward converter has the advantages of zero-voltage-switching performance for all the primary switches, reverse-recovery-problem alleviation for the secondary output diodes, large voltage-conversion ratio, and small input-current ripple. Furthermore, there are two coupled inductors in the proposed converter. Each coupled inductor can work in the flyback mode when the corresponding main switch is in the turn-on state and in the forward mode when it is in the turnoff state, which takes full use of the magnetic core and improves the power density. In addition, the full-bridge inverter with an LC low-pass filter is adopted to provide low-total harmonic-distortion ac voltage to the load. Therefore, high-efficiency and high-power density conversion can be achieved in a wide input-voltage range by employing the proposed system. Finally, a 500-W prototype and another 1-kW converter are implemented and tested to verify the effectiveness of the proposed system.
- Active clamp
- Fly back–forward converter
- Fuel cell generation system.
Fig. 1. Proposed high-efficiency fuel-cell power-generation system.
EXPECTED SIMULATION RESULTS:
Fig. 2. Experimental results of proposed ZVS flyback–forward converter: (a) ZVS operation of main switch S1. (b) ZVS operation of clamp switch Sc1. (c) Voltage and current waveforms on clamp capacitors Cc1 and Cc2. (d) Current waveforms of primary side. (e) Voltage waveforms on output diodes Do1 and Do2. (f) Detailed turnoff current across output diode Do1.
Fig. 3. Experimental results of full-bridge inverter: (a) AC output-voltage and output-current waveforms at 500-W resistor load. (b) AC output-voltage and output-current waveforms at 180-W RCD load. (c) Dynamic response from 50- to 500-W resistor load.
In this paper, an interleaved high-step-up ZVS fly back–forward converter has been proposed for the fuel-cell power generation system. The voltage doubler rectifier structure is employed to provide a large voltage-conversion ratio and to remove the output-diode reverse-recovery problem. Furthermore, ZVS soft-switching operation is realized for all the primary active switches to minimize the switching losses. In addition, the input-current ripple is small due to the interleaved operation and the current-fed-type configuration. The steady state operation analysis and the main circuit performance are discussed to explore the advantages of the proposed converter in a high-efficiency high-step-up power-generation system. Finally, a 500-W 12-V dc to 220-V ac system is employed and another 1-kW prototype operated at 100 kHz is tested as examples to illustrate the important design guidelines of the proposed converter. Experimental results have demonstrated that the proposed system is an excellent power-converter system for fuel-cell applications, featuring high efficiency, high-step up ratio, and high power density.
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