This study presents a buck-boost-flyback integrated converter (BBFIC), which can step up the voltage of photovoltaic (PV) module or fuel cell to a much higher level for grid-tied applications. The converter combines two buck-boost converters and one flyback converter into a single-stage structure with single power switch. In the power stage, an inductor and a coupled inductor are adopted to feature buck-boost and flyback behaviours, and three capacitors are connected in series to stack up output voltage. Even though it possesses the characteristics of buckboost and flyback converters, the problem of reversed voltage polarity is avoided and the energy stored in leakage inductor can be recycled without additional active clamp circuits. The structure of BBFIC can be easily expanded to obtain an extra-high voltage gain by stacking buck-boost cells or flyback cells. Voltage gain derivation and theoretical analysis are detailed in this study. Simulations and practical results measured from a prototype have validated the proposed BBFIC.

This study proposes a novel isolated bidirectional DC/DC converter for micro-grid system, which can fulfil battery charging and discharging. Even though the proposed converter only employs four active switches and a coupled inductor, it can achieve high-voltage ratio without excessive duty ratio or high transformer turns ratio. The power stage of the converter is mainly developed by integrating a three-winding coupled inductor, three-switched capacitors, and a flyback-behaviour converter into a novel structure. The energy stored in the leakage inductance can be totally recycled for efficiency improvement. The operation principle, steady-state analysis, and design considerations of the proposed converter are described in detail. Finally, a laboratory prototype is built to validate the converter. The measured results have verified the correctness and the theoretical analysis.

This paper presents a novel interleaved converter (NIC) with extra-high voltage gain to process the power of low-voltage renewable-energy generators such as photovoltaic (PV) panel, wind turbine, and fuel cells. The NIC can boost a low input voltage to a much higher voltage level to inject renewable energy to DC bus for grid applications. Since the NIC has two circuit branches in parallel at frond end to share input current, it is suitable for high power applications. In addition, the NIC is controlled in an interleaving pattern, which has the advantages that the NIC has lower input current ripple, and the frequency of the ripple is twice the switching frequency. Two coupled inductors and two switched capacitors are incorporated to achieve a much higher voltage gain than conventional high step-up converters. The proposed NIC has intrinsic features such as leakage energy totally recycling and low voltage stress on power semiconductor. Thorough theoretical analysis and key parameter design are presented in this paper. A prototype is built for practical measurements to validate the proposed NIC.

Abstract:In this paper, an integrated three-voltage-booster DC-DC (direct current to direct current) converter is proposed to achieve high voltage gain for renewable-energy generation systems. The proposed converter integrates three voltage-boosters into one power stage, which is composed of an active switch, a coupled-inductor, five diodes, and five capacitors. As compared with conventional high step-up converters, it has a lower component count. In addition, the features of leakage-energy recycling and switching loss reduction can be accomplished for conversion efficiency improvement. While the active switch is turned off, the converter can inherently clamp the voltage across power switch and suppress voltage spikes. Moreover, the reverse-recovery currents of all diodes can be alleviated by leakage inductance. A 200 W prototype operating at 100 kHz switching frequency with 36 V input and 400 V output is implemented to verify the theoretical analysis and to demonstrate the feasibility of the proposed high step-up DC-DC converter.