Photovoltaic generators interfacing a DC micro-grid: Design considerations for a double-stage boost power converter system

A photovoltaic generator (PVG) is usually connected to a DC micro-grid via a multi-stage-step-up power converter to improve system modularity, minimise shading effects and boost PVG voltage. Under varying operating conditions, the nonlinear characteristics of a PVG may affect performance of the entire PVG system. Further, if these issues are not properly taken into account at the design stage, significant changes in system dynamics may risk stability of the system. Therefore, it is important to understand interactions between a PVG and the rest of the system. A clear understanding of these interactions can help to set system design recommendations and guidelines. In particular, this paper explores the effects of a nonlinear PVG source interfacing a double-stage conventional boost converter connected to a DC bus. It addresses the impact of these effects on the design of both the power circuit and the control loops. Finally, this paper provides system design recommendations to ensure stability under varying operating conditions.