Nonisolation Soft-Switching Buck Converter With Tapped-Inductor for Wide-Input Extreme Step-Down Applications

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Differential power processing (DPP) systems are among the most effective architectures for photovoltaic (PV) power systems because they are highly efficient as a result of their distributed local maximum power point tracking ability, which allows the fractional processing of the total generated power. However, DPP systems require a high-efficiency, high step-up/down bidirectional converter with broad operating ranges and galvanic isolation. This study proposes a single, magnetic, highefficiency, high step-up/down bidirectional DC-DC converter. The proposed converter is composed of a bidirectional flyback and a bidirectional isolated switched-capacitor cell, which are competitively cheap. The output terminals of the flyback converter and switched-capacitor cell are connected in series to obtain the voltage step-up. In the reverse power flow, the converter reciprocally operates with high efficiency across a broad operating range because it uses hard switching instead of soft switching. The proposed topology achieves a genuine on-off interleaved energy transfer at the transformer core and windings, thus providing an excellent utilization ratio. The dynamic characteristics of the converter are analyzed for the controller design. Finally, a 240 W hardware prototype is constructed to demonstrate the operation of the bidirectional converter under a current feedback control loop. To improve the efficiency of a PV system, the maximum power point tracking method is applied to the proposed converter.

Section: Resultsmentioning

confidence: 99%

Bidirectional Power Conversion of Isolated Switched-Capacitor Topology for Photovoltaic Differential Power Processors

Kim¹,

Park²,

Jeon³

2016

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“…The surface temperatures of the components were measured by a Thermal Imaging Camera (DM-60,Zhejiang Dali Technology Co., Ltd). The infrared thermography system consists mainly of a camera and software for converting the recorded information to the temperature signal [22], [23]. Fig.…”

Section: B Experimental Resultsmentioning

confidence: 99%

High Efficiency Step-Down Flyback Converter Using Coaxial Cable Coupled-Inductor

Kim¹,

Park²

2013

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This paper proposes a high efficiency step-down flyback converter using a coaxial-cable coupled-inductor which has a higher primary-secondary flux linkage than sandwich winding transformers. The structure of the two-winding coaxial cable transformer is described, and the coupling coefficient of the coaxial cable transformer and that of a sandwich winding transformer are compared. A circuit model of the proposed transformer is also obtained from the frequency-response curves of the secondary short-circuit and of the secondary open-circuit. Finally, the performance of the proposed transformer is validated by the experimental results from a 35W single-output flyback converter prototype. In addition, the proposed two-winding coaxial transformer is extended to a multiple winding coaxial application. For the performance evaluation of the extended version, 35W multi-output hardware prototype of the DC-DC flyback converter was tested.

“…Many step-up DC-DC converters with a charge pump coupled-by the magnetic devices outputs have been used in PV systems [16][17][18][19][20][21][22][23]. However, for the application of a converter to a MLI, a gain-matching constraint between the boost and the charge-pump should be satisfied.…”

Section: A Boost Converter With An Isolated Charge-pumpmentioning

confidence: 99%

A New Photovoltaic System Architecture of Module-Integrated Converter with a Single-sourced Asymmetric Multilevel Inverter Using a Cost-effective Single-ended Pre-regulator

Manoharan¹,

Ahmed²,

Park³

2017

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In this paper, a new architecture for a cost-effective power conditioning systems (PCS) using a single-sourced asymmetric cascaded H-bridge multilevel inverter (MLI) for photovoltaic (PV) applications is proposed. The asymmetric MLI topology has a reduced number of parts compared to the symmetrical type for the same number of voltage level. However, the modulation index threshold related to the drop in the number of levels of the inverter output is higher than that of the symmetrical MLI. This problem results in a modulation index limitation which is relatively higher than that of the symmetrical MLI. Hence, an extra voltage pre-regulator becomes a necessary component in the PCS under a wide operating bias variation. In addition to pre-stage voltage regulation for the constant MLI dc-links, another auxiliary pre-regulator should provide isolation and voltage balance among the multiple H-bridge cells in the asymmetrical MLI as well as the symmetrical ones. The proposed PCS uses a singleended DC-DC converter topology with a coupled inductor and charge-pump circuit to satisfy all of the aforementioned requirements. Since the proposed integrated-type voltage pre-regulator circuit uses only a single MOSFET switch and a single magnetic component, the size and cost of the PCS is an optimal trade-off. In addition, the voltage balance between the separate H-bridge cells is automatically maintained by the number of turns in the coupled inductor transformer regardless of the duty cycle, which eliminates the need for an extra voltage regulator for the auxiliary H-bridge in MLIs. The voltage balance is also maintained under the discontinuous conduction mode (DCM). Thus, the PCS is also operational during light load conditions. The proposed architecture can apply the module-integrated converter (MIC) concept to perform distributed MPPT. The proposed architecture is analyzed and verified for a 7-level asymmetric MLI, using simulation results and a hardware implementation.