Nondissipative String Current Diverter for Solving the Cascaded DC-DC Converter Connection Problem in Photovoltaic Power Generation System

Frequently considered one of the promising solutions for grid connection of the photovoltaic (PV) power generation system, module-integrated converters have been the focus of numerous papers. Most of the proposed approaches thus far have relied on the use of series string of the dc-dc converter to create a high-voltage string connected to the dc-ac inverter. The boost converter is better in this application. However, under inhomogeneous irradiation, the power generated by each PV module and the output dc voltage of each boost become unbalanced so that the output currents of each boost are balanced and equal to the string current. In this case, the boost converter cannot always deliver all the power from a mixture of shaded panels and those delivering full power. In this paper, a nondissipative string current diverter is proposed to overcome this problem. One important feature of the proposed circuit herein is the ability to effectively decouple each converter from the rest of the string, making it insensitive to change in the string current. Hence, it is possible to obtain the maximum power from the PV module with the maximum power point tracking algorithm implemented on each dc-dc converter and to do so at the optimum efficiency. The simulation and experimental results verify that the proposed topology exhibits notable performances despite inhomogeneous irradiation. On the other hand, the string current diverter circuit is very easy to control and does not operate without inhomogeneous irradiation, so the topology efficiency is improved for any type of irradiation.