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This paper proposes a new high step-up DC-DC converter designed especially for regulating the DC interface between various microsources and a DC-AC inverter to electricity grid. The figuration of proposed converter is a quadratic boost converter with the coupled inductor in the second boost converter. The converter achieves high step-up voltage gain with appropriate duty ratio and low voltage stress on the power switch. Additionally, the energy stored in the leakage inductor of the coupled-inductor can be recycled to the output capacitor. The operating principles and steady-state analyses of continuous-conduction mode and boundary-conduction mode are discussed in detail. To verify the performance of the proposed converter, a 280W prototype sample is implemented with an input-voltage range of 20 ~ 40 V and output voltage of up to 400 V. The upmost efficiency of 93.3% is reached with high line input; on the other hand, the full-load efficiency remains at 89.3% during low line input.

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A novel high step-up dc-dc converter for a distributed generation system is proposed in this paper. The concept is composed of two capacitors, two diodes, and one coupled inductor. Two capacitors are charged in parallel, and are discharged in series by the coupled inductor. Thus, high step-up voltage gain can be achieved with an appropriate duty ratio. The voltage stresses on the main switch and output diode are reduced by a passive clamp circuit. Therefore, low resistance R D S (O N ) for the main switch can be adopted to reduce conduction loss. In addition, the reverserecovery problem of the diode is alleviated, and thus, the efficiency can be further improved. The operating principle and steady-state analyses of the voltage gain are also discussed in detail. Finally, a 24-V input voltage, 400-V output voltage, and 400-W output power prototype circuit of the proposed converter are implemented in the laboratory to verify the performance.

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