Shading mitigation techniques: State-of-the-art in photovoltaic applications

The Photovoltaic (PV) systems are gaining popularity for both standalone and grid connected applications. These systems offer benefits of being static, modular, environmental friendly; and converts light from the Sun, which is perennial source of clean and green energy. The energy conversion in PV system is although instantaneous, yet less efficient because of optical and electrical losses. The optical loss caused by partial shading reduces a PV system output greatly, if not properly mitigated. The shading mitigation techniques are therefore an integral part of power conditioning unit of all large PV systems. These mitigation techniques ensure global peak operation of PV plant under undesirable condition of partial shading. Multitudes of such mitigation techniques are available in literature; though each one of them exhibits some vulnerability. This paper therefore intends to present state-of-art in existing shading mitigation techniques. The review presents rationale behind the reported techniques and compares them on some common parameters of control strategy, granularity, accuracy, tracking speed, complexity, efficiency and number of sensors employed. This comprehensive review on shading mitigation techniques would certainly help researcher to select appropriate MPPT techniques for a given PV application.