Cell parameter variability analysis and MPPT control of photovoltaic modules

This paper presents an analysis of inherent cell mismatch in PV modules and its impact on Maximum Power Point Tracking (MPPT) achieved via buck-boost converter control. Inherent cell mismatch is defined as mismatch induced within the module stemming from manufacturing imperfections or long-term degradation processes such as delamination. We model the mismatch processes in a module by considering various distributions in the cell parameters of a one-diode model such as series and shunt resistances. In order to study the impact of inherent cell mismatch on power output we developed, in Matlab Simulink, a PV module model where the parameters of each PV cell can be configured dynamically. The model also includes a DC-DC buck-boost converter and MPPT controller using a simple Perturb and Observe (P&O) algorithm. The impact on MPPT due to various distributions of PV cell parameters is reported. Since the parameters can be dynamically changed, we are also able to study the impact on MPPT due to parameter variations occurring over both slow and fast time-scales.