Buck-Flyback (fly-buck) Stand-Alone Photovoltaic System for Charge Balancing with Differential Power Processor Circuit

초록

In this paper, a buck-flyback (fly-buck) stand-alone photovoltaic (PV) system for charge balancing with a differential powerprocessor (DPP) circuit is proposed. Conventional feed-back DPP converters draw differential feed-back power from the outputof a string converter. Therefore, the power is always through the switches and diodes of the string converter. Because of thereturning conduction path, there are always power losses due to the resistance of the switch and the forward voltage of the diode. Meanwhile, the proposed feed-back DPP converter draws power from the magnetically-coupled inductor in a string converter. This shortens the power path of the DPP converter, which reduces the power losses. In addition, the extra winding in themagnetically-coupled inductor works as a charge balancer for battery-stacked stand-alone PV systems. The proposed system,which uses a single magnetically-coupled inductor, can control each of the PV modules independently to track the maximumpower point. Thus, it can overcome the power loss due to the power path. It can also achieve charge balancing for each of thebattery modules. The proposed topology is analyzed and verified using 120W hardware experiments.

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