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This paper studies the maximum power point tracking (MPPT) methods under partially shaded conditions for a stand-alone PV array system. The rules for judging partially shaded conditions are presented and integrated into four MPPT methods. These methods are tested in real-time simulation environment, and their advantages and disadvantages are further analyzed. Matlab/Simulink/SimPowerSystems are used with RT-Lab for building the real-time simulation models and the MPPT controller for partially shaded conditions. Based on the simulation results, the MPPT methods integrated with judging rules for partially shaded conditions can track the maximum power point better than those without judging rules, elevating the usage efficiency of PV arrays.

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Maximum power point tracking algorithm is widely implemented in photovoltaic system to maximize the PV array output power. In general, Perturb and Observe (P&O) is simple thus being selected to continuously track the array maximum power point (MPP). Under uniform solar irradiance, PV array characteristic is non-linear and consisting only one MPP along the functional operating voltage. However, when the PV array is partially shaded, the P-V characteristic becomes more complex with multiple MPPs. The occurrence of multiple MPP might cause the PV array to be trapped at the local MPP. At this operating condition of local MPP, PV array will generate lesser output power. In this study, the performance of PV array is explored especially when each PV module is at 30% and 70% shaded conditions. Simulation results show that PV array at absolute MPP can generate greater output power with the largest increased by 74.6% hence achieving higher power efficiency.