A Soft-Switched Power Module With Integrated Battery Interface for Photovoltaic-Battery Power Architecture

Abstract

In conventional photovoltaic (PV)-battery systems, a centralized battery storage system (BSS) is typically connected through a separate bidirectional converter at the common dc link to support the PV system. It is known that a bidirectional converter typically requires more switches than a unidirectional converter, and hence, a complete PV-battery power interface will result in a high-cost system and will suffer high power losses. This paper proposed an integrated battery storage interface with soft-switching capability for module-integrated PV systems. In the proposed system, a multi-input converter (MIC) structure that consists of an integrated soft-switched quasi-resonant (QR) Cuk- and flyback-based circuit is presented. In this approach, the battery charging circuit is integrated with the input side of the PV power optimizer while the battery discharging circuit of the proposed system shares the output filter of the PV power optimizer, resulting in a compact and efficient system. The proposed converter is capable of tracking the maximum power point (MPP) and following the charging profile (constant voltage and constant current) of the battery. Moreover, all the switches in the proposed converter are able to achieve soft-switched turn on and turn off for different operating conditions. The operating principles and the theoretical analysis of the proposed system are presented. Experimental results on a 175-W proof-of-concept prototype are presented to demonstrate the features of the proposed converter.