Dual-mode magnetically integrated photovoltaic microconverter with adaptive mode change and global maximum power point tracking

Abstract

This study proposes a high step-up galvanically isolated dc-dc converter based on the quasi-Z-source (qZS) network. The voltage gain of the converter can change in a wide range. This feature makes the converter suitable for applications with a wide input voltage range. The range of the dc gain is increased by the implementation of the combined energy transfer principle. A reconfigurable structure is used to combine the energy transfer by the isolation transformer and the coupled inductor of the impedance-source network. The adaptive mode change activates the energy transfer via an additional winding in the qZS network at lower voltages, which results in considerable efficiency improvement. Consequently, the input voltage range of the converter is extended to the values useful in photovoltaic applications impacted by partial shading. The proposed approach is verified in a photovoltaic (PV) microconverter, where the energy harvest from a PV module is possible during shading by enabling the global maximum power point tracking (GMPPT). It is demonstrated that the dual-mode operation of the converter helps to achieve a flat efficiency curve along with outstanding maximum power point tracking (MPPT) performance.