Analysis and experimental verification of series-connected micro-converter photovoltaic system

The micro-converter Photovoltaic (PV) system which is composed of several cascaded Buck-Boost converters and a central inverter, enables each PV panel to operate at its local maximum power point (MPP). The cascaded buck-boost converter can operate in buck, boost or pass-through mode to realize a wide output voltage range without inverted polarity. However, there is a difficulty in keeping power balance between the central inverter and the series-connected converters, especially in startup process. Thus, this paper proposes an improved startup procedure and protection strategy to enhance stabilization and enable the converters to start successively. The wide-range output voltage of the converters and proper control strategy broaden the restriction upon the number of modules in series. Simulation and experimental results are presented to demonstrate the benefits of the proposed control strategy.