PV String-Level Isolated DC–DC Power Optimizer with Wide Voltage Range

Hyungjin Kim, Gibum Yu, Jaehoon Kim and Sewan Choi
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Hyungjin Kim: Department of Electrical & Information Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea
Gibum Yu: Department of Electrical & Information Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea
Jaehoon Kim: Department of Electrical & Information Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea
Sewan Choi: Department of Electrical & Information Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea

Energies, 2021, vol. 14, issue 7, 1-18

Abstract: This paper proposes a photovoltaic (PV) string-level isolated DC–DC power optimizer with wide voltage range. A hybrid control scheme in which pulse frequency modulation (PFM) control and pulse width modulation (PWM) control are combined with a variable switching frequency is employed to regulate the wide PV voltage range. By adjusting the switching frequency in the above region during the PWM control process, the circulating current period can be eliminated and the turn-on period of the bidirectional switch of the dual-bridge LLC (DBLLC) resonant converter is reduced compared to that with a conventional PWM control scheme with a fixed switching frequency, resulting in better switching and conduction loss. Soft start-up control under a no-load condition is proposed to charge the DC-link electrolytic capacitor from 0 V. A laboratory prototype of a 6.25 kW DBLLC resonant converter with a transformer, including integrated resonant inductance, is built and tested in order to verify the performance and theoretical claims.

Keywords: isolated DC–DC converter; photovoltaics; LLC resonant converter; dual-bridge; wide voltage range; power optimizer (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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