The present paper studies thoroughly the performance of the classical perturb-and-observe (P&O) method under
fast-changing solar irradiation, including increase or decrease of the irradiation level with small or large steps,
when the initial operating point lies to the right or left of the MPP. In sixteen case studies of sudden variation of
solar irradiation, the classical P&O method fails to track MPP properly in four cases. The classical P&O tracker
does not work properly under a ramp change of irradiation level. A modified P&O-based-MPP tracking method is
proposed and tested under step and ramp changes of irradiation irrespective of the value and direction of the
perturbation in irradiation level and the location of the initial operating point. The proposed method succeeds in
capturing the MPP under a ramp or slow change of irradiation level. The proposed method tracks correctly the
MPP in the above-mentioned case studies and shows better performance in tracking speed, steady state efficiency,
dynamic efficiency and tracking accuracy when compared with the classical P&O method and other
modified methods reported in the literature.