Dynamic stability of grid-connected photovoltaic systems

A mathematical model of grid-connected photovoltaic energy sources suitable for stability studies is presented. The power electronic conditioning unit is modelled from basic power transfer relations. Using this model, it is demonstrated that there exist two solutions for a given power output, one of which is unstable. By doing eigenvalue and eigenvector analysis, dynamic orbits are presented that help visualize any potential problem that may occur under disturbances. Simulations are carried out showing instances where the voltage at the photovoltaic panel collapses, in particular when operating close to the maximum power point.