Stability of a boost converter fed from photovoltaic source

Abstract

The use of photovoltaic panels has become very attractive in distributed power generation systems as they provide a clean and cheap form of energy. There are various converter topologies that are employed in order to connect these sources to the grid but almost always the main component is a DC–DC converter. Most readily available DC–DC converters are designed to work under a (nearly) constant voltage source and therefore their behaviors may not be as expected when connected to a variable current source like a photovoltaic panel. In fact, as it is reported in this paper, the behavior of the overall system (PV panel/DC–DC converter) can be drastically different from the desired one which may have a detrimental effect on the grid. As a case study, this paper explores the dynamics and stability of a boost converter that is fed from a photovoltaic panel under an ohmic load. All major control methods (peak/average current mode control, voltage mode control) are considered. We show with numerical, experimental and analytical results that the converter can behave unpredictably (or chaotically) when the output of the PV varies in response to the variation in solar radiation, and we report for the first time how the domain of stability in the parameter-space and the mechanisms of instability are affected by the characteristics of the photovoltaic source. The dynamical features are explored from circuit theory and nonlinear dynamics points of view. This knowledge will help in compensating for the aforementioned uncertainty and can be used to design converters that remain stable throughout the range of incident solar radiation and load values. The results have been experimentally validated.