Series-Connected Partial-Power Converters Applied to PV Systems: A Design Approach Based on Step-Up/Down Voltage Regulation Range

This paper proposes a novel approach to reduce the power processed by series-connected partial-power converters (S-PPC) applied to string/multistring level maximum power point tracking photovoltaic systems. A design procedure based on the definition of the voltage regulation range is presented. It introduces an additional degree of freedom that allows a proper design of the converter in order to reduce not only the active power but also the nonactive power, reducing losses and increasing power density. By means of the proposed approach, it is also demonstrated that by replacing the conventional step-up partial-power converter by a step-up/down partial-power converter, the active and nonactive power can be further reduced, allowing to better explore the benefits of the partial-power concept. In order to validate the proposed approach, two 750-W prototypes of full-bridge S-PPC and full-bridge/push-pull S-PPC were implemented and experimentally evaluated. The step-up/down prototype presented a reduction of 46.9% in nonactive power and 23.4% of its volume, resulting in a higher efficiency and power density in comparison to the voltage step-up prototype counterpart.