A method is proposed for calculating the I-V and P–V curves of a PV array composed of series-, parallel- and series–parallel connected-cells or modules or strings exposed to uniform and non-uniform radiation with and without bypass diodes (BpDs). The P–V curve of the array exposed to uniform radiation has one power peak irrespective of the presence or absence of BpDs. In non-uniform radiation, the curve has a number of power peaks equal to that of the radiation levels in presence of BpDs irrespective of the number of diodes against one peak in absence of BpDs. The proposed method is based on combining Lambert-based simultaneous-solutions of the describing-equations V = g (I) and I = f (V) to obtain a global voltage equation V in terms of current I over all current range. The method is extended to locate the global maximum power point (GMPP) of the array by locating a point close to the GMPP