Maximum Power Point Tracking Algorithm for Grid-tied Photovoltaic Cascaded H-bridge Inverter

In this article, a maximum power point tracking algorithm properly adapted for a grid-tied photovoltaic multi-level inverter is presented. The inverter structure is based on a single-phase cascaded H-bridge configuration, where each power cell is supplied by an individual photovoltaic panel. The dedicated maximum power point tracking algorithm is based on a suitable hysteresis band, which defines the proper boundaries for maximum power point tracking references to ensure both stable inverter operation and maximum photovoltaic power extraction. The inverter control method is a mixed staircase pulse-width modulation based on a sorting algorithm. Some experimental tests have been performed by using a laboratory prototype of a single-phase five-level photovoltaic cascaded H-bridge inverter, which is controlled by means of dSPACE real-time hardware platform (ds1006, dSPACE GmbH, Paderborn, Germany), where the control section is implemented on a field-programmable gate array (Xilinx Virtex5, Xilinx, Inc., San Jose, CA). The experimental results confirm that the proposed control is able to efficiently track the maximum power point while assuring good performance in terms of harmonic distortion and power factor in both standard and mismatch conditions.