Novel High-Efficiency Three-Port Bidirectional Step-Up/Step-Down DC–DC Converter for Photovoltaic Systems

Yu-En Wu and Shiu-Liang Hsiao
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Yu-En Wu: Department of Electronic Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 824, Taiwan
Shiu-Liang Hsiao: Department of Electronic Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 824, Taiwan

Sustainability, 2021, vol. 13, issue 14, 1-18

Abstract: This paper presents a novel high-efficiency three-port bidirectional DC–DC converter for photovoltaic (PV) systems. A PV system’s output is stepped up to supply a DC bus or DC load while charging the battery. When the PV output is insufficient, the battery voltage is stepped up to the DC bus; when the DC bus has excess energy, it is stepped down to charge the battery. Thus, a high-efficiency three-port bidirectional step-up/step-down converter is achieved. A common-core coupled inductor was designed and adopted in the proposed converter. Power switches and diodes in the circuit are shared to achieve bidirectional operation. In step-up mode, the clamp capacitor is used to reduce the voltage spike on the main switches. Moreover, the voltage-doubling capacitor recovers energy from the secondary-side leakage inductance. Furthermore, the input capacitors recover the primary-side leakage inductance energy in step-down mode. Thus, the converter can improve its conversion efficiency. Finally, this paper details the implementation of a 500 W three-port bidirectional converter to verify the feasibility and the practicability of the proposed topology. According to the measurement results, the highest efficiency levels of the PV and the battery in step-up mode were 94.3% and 94.1%, respectively; the highest efficiency in step-down mode was 95.2%.

Keywords: three-port bidirectional converter; coupled inductor; photovoltaic system (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
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