European Journal of Scientific Research ISSN 1450-216X Vol.47 No.1 (2010), pp.122-134 © EuroJournals Publishing, Inc. 2010 http://www.eurojournals.com/ejsr.htm Development of an Improved Model of SPV Cell for Partially Shaded Solar Photovoltaic Arrays R.Ramaprabha Department of EEE, SSN College of Engineering, Chennai, Tamilnadu, India Tel: +91-044-27475065; Fax: +91-044-27475063 E-mail: ramaprabhasuresh@gmail.com B.L.Mathur Department of EEE, SSN College of Engineering, Chennai, Tamilnadu, India Tel: +91-044-27475065; Fax: +91-044-27475063 E-mail: blmathur@ssn.edu.in Abstract A loaded illuminated Solar Photovoltaic (SPV) cell produces forward voltage and forward current. When a number of such cells are connected as series string and some of these cells are not illuminated then the voltage across unilluminated cells may get reversed, though the current remains in the forward direction. In a commercial module, groups of cells (generally 18) are shunted by a diode to limit the reverse voltage to 0.7 V but all the cells are not shunted. Characteristics of these unilluminated cells are therefore required to be studied in the second quadrant also. This work presents first and second quadrant model of SPV cell. Equivalent shunt resistance (R sh ) in the model varies with environmental parameters. The effect of change in R sh hitherto neglected by many researchers has been correctly modelled and incorporated in the equivalent circuit. The developed model has been validated through experimentation using a novel simple electronic load. Keywords: SPV Module, Improved model, Reverse Characteristics, MATLAB, Novel Electronic load 1. Introduction Solar Photovoltaic (SPV) cells directly convert sunlight into electricity. Many SPV cells are grouped together to form a module. Modules are normally formed by series connection of SPV cells to get the required output voltage. Modules having large output currents are realized by increasing the surface area of each SPV cell or by connecting several of these in parallel. A SPV array may be either a module or group of modules connected in series/parallel configuration. Output of the SPV array may directly feed loads or may use power electronic converter for further processing. These converters may be used to serve different purposes like controlling the power flow in grid connected systems, track the maximum power available from the SPV array. Model of SPV system is therefore required to study and optimize the performance of the complete system including these converters and other connected loads. This paper aims at developing a complete mathematical model of a SPV cell suitable for analysis of a non-uniformly illuminated solar array. SOLKAR (Model No.3712/0507) cells and