An isolated AC module for photovoltaic energy conversion

ABSTRACT

In this paper, an isolated ac module with pseudo dc-link and galvanic isolation is proposed for photovoltaic energy conversion. The studied grid-tie ac module can individually extract the maximum solar power from each photovoltaic panel and transfer to ac utility system. It consists of an interleaved active-clamping single-ended primary-inductive circuit (SEPIC) with a secondary voltage doubler, a full-bridge polarity selector operating under line frequency to achieve high efficiency. For the studied topology, key features such as reduced input current ripple, zero-voltage switching (ZVS) of primary switches, low reverse-recovery current of the output diodes, and lower switch voltage stress are obtained. Also, to reduce input current ripple, an interleaved control strategy is adopted. A simple control strategy is proposed to generate a rectified sinusoidal waveform voltage at the pseudo dc-link capacitors and achieve the high maximum power point tracking (MPPT) accuracy. The operation principles and design considerations of the studied ac module are analyzed and discussed. A prototype with 25–60 V dc input, 110 V/60 Hz ac output and 150 W power rating has been constructed for verifying the feasibility of the proposed ac module.

KEYWORDS:

• AC module
• active-clamping
• interleaved
• pseudo dc-link
• SEPIC

Funding

This research is sponsored by Ministry of Science and Technology of Taiwan, R.O.C. under contracts MOST 103-2622-E-033-008-CC3, MOST 104-2623-E-027-005-ET, and MOST 104-2622-E-027-023-CC3.

Additional information

Funding

This research is sponsored by Ministry of Science and Technology of Taiwan, R.O.C. under contracts MOST 103-2622-E-033-008-CC3, MOST 104-2623-E-027-005-ET, and MOST 104-2622-E-027-023-CC3.