0885-8969 (c) 2018 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TEC.2018.2876132, IEEE Transactions on Energy Conversion 1 Effect of Partial Shading on PV fed Induction Motor Water Pumping Systems Arjun M, Vanjari Venkata Ramana, Student Member, IEEE, Roopa Viswadev Damodaran, B Venkatesaperumal, Member, IEEE, and Sukumar Mishra**, Senior Member, IEEE Abstract—Partial shading is one of the certain conditions in photovoltaic (PV) power plants. Often the panels get partially shaded due to soiling, clouds, and trees. The effect of shading is of high concern and importance especially in applications such as water pumps due to agricultural environments in which they are employed in. However, the research focus on PV fed pumps till date has been restricted to only uniform shading conditions. Unlike uniform shading conditions during maximum power tracking, where the panel voltage remains almost constant for an entire range of irradiance, partial shading offer conditions such as highly variable panel voltage, transitions of intermediate DC-DC power converter from continuous conduction mode to discontinuous conduction mode. These effects severely affect the performance of the power converter and therefore the power output of the pump. This paper presents a study on the effects caused by partial shading conditions on pumps through simulations and verified by experimentations. The simulation and experimental results are found to be in good agreement with each other. This research work thus helps in understanding the detrimental effects casued by partial shading conditions and thus serves as a reference tool for practitioners who wish to study PV fed pumps. Index Terms—continuous and discontinuous conduction modes of operation, induction motor (IM), partial shading conditions, photovoltaic (PV) systems, water pumping systems. I. I NTRODUCTION Photovoltaic (PV) systems have gained a lot of prominence in the recent years due to their long – term advantages. PV arrays are the most basic units of any PV driven systems. These PV arrays have a characteristic that it exhibits a non- linear relationship between its voltage and current, and there exists only one operating point at which maximum power can be extracted from the PV array [1] [2]. This operating point is called maximum power point (MPP) and operating the PV at this MPP is one of the most sought–after research topics in PV systems. In an array consisting of a number of panels, it is very much sure that not all panels receive same irradiation. Often some panels are exposed to shades of buildings, clouds, etc., causing multiple peaks in the characteristics of PV array, and is termed as partial shading condition (PSC) [3]. Extracting MPP point under such conditions becomes more challenging and complex. Several efficient algorithms for detecting the MPP under partial shading conditions have been reported in the literature. The algorithms successfully identify MPP even The Authors are with Department of EEE, National Institute of Technology Karnataka, Surathkal, Karnataka, India (corresponding author: Arjun M, email: arjunmudlapur@gmail.com) **The author is with department of EEE, Indian Institute of Technology, Delhi, India at rapidly changing environmental circumstances, however, its effects on power converters and the overall system output are not studied yet. This study on the impact of PSC in PV systems is of high importance especially in the field of water pumping systems. PV fed water pumps are often employed in agricultural sectors where panels are exposed to soiling, shades of trees and clouds. With slow–moving clouds the conditions worsen even more. Over the years of developments in the field of PV pump systems, several topologies have been developed. PV pumping systems with DC machines [4]– [6], induction machines (IM), permanent magnet (PM) machines [7], [8] and switched reluctance machines [9] can be seen in literature. IM based water pumping systems are available in single and two–stage conversions [13]. Single stage conversion systems eliminate the usage of the DC–DC converter and a single inverter performs maximum transfer and power conversion operation [10]– [12]. Several algorithms for maximum efficiency and loss minimization [12], optimized v/f control [14], the com- parison between MPPT and maximum efficiency operations [15] are studied in the recent years. The effect of changing insolation on the pump output [16], the effect of pumping head, insolation and PV array size on pumping performance [17], [18], nonlinear behaviour [19], [20] of the pump system has been mathematically modeled and their validity is tested on hardware prototype. With the advancements in power electronic technology, better and efficient control techniques have become practically possible. Systems with push-pull converters [21], vector control [22] for induction motors have been implemented as laboratory prototypes. These controls are however complex and require a high degree of microcontroller computation. The issues with the PI controller design and the tuning techniques based on the open loop characteristics have been studied in [23]. A Fuzzy logic based control has also been proposed to overcome the tuning issues of the conventional PI controller [24]. However, all these studies mentioned above assumes the PV to be receiving uniform irradiance. In case of uniform shading, the maximum power condition for varying irradiance occurs near the open circuit voltage region of the PV characteristics. In case of partial shading, the MPP occurs anywhere on the curve [29]. The occurrence of MPP anywhere over such wide range is found to have considerable effects on both single stage and double stage pump systems. In single stage pumps, if the peak power lies at the short circuit current region, the available panel voltage may not be sufficient to run the IM pump system, and the pump fails to operate, though adequate power is