Evaluation of mismatch power loss in a PV string composed of series-connected modules: Theory versus experiment

Ground-installed PV power-systems are usually built in parallel-rows; each is composed of series-connected modules. With time, some modules got-polluted or −shaded differently. On damage, some modules may be replaced by others of different ratings. This creates mismatch among the series-connected modules accompanied by loss of output power. This motivates the authors to extend their earlier proposed three-stage methodology for calculating the I-V and P-V curves to evaluate the mismatch power loss. The studied mismatches are due to series-connected dusty and clean modules, modules with different ratings, and modules with a half-cell shading in one of the modules. The proposed three-stage methodology is based on solution of Lambert-function in three-steps. The calculated current–voltage and power-voltage curves as well as highest output power by proposed methodology are validated by experimental results for the investigated mismatch conditions. The percentage mismatch power-loss recorded values of 5.4 %, 12.11 %, and 17.9 %.