Solar PV Cell

The equivalent circuit of the solar PV cell is given below in Fig. 5.2. Iph is the cell photocurrent that is proportional to solar irradiation, Irs is the cell reverse saturation current that mainly depends upon the temperature, Ko is a constant, Ns and Np are the number of series and parallel strings in the PV array respectively, Rsh and Rp is the series and parallel resistance of the PV array. Generally, a PV module comprises of a number of PV cells connected in either series or parallel and its mathematical model can be simply expressed as given below. The equation describing the I-V characteristics of the solar array are as follows [2]:

Fig. 5.2 Equivalent circuit of solar cell

Fig. 5.3 Simulated I-V curve of a SPV module for varying irradiance condition at 25 °C temperature

Fig. 5.4 Simulated P-V curve of a SPV module for varying irradiance condition at 25 °C temperature

where, I denotes the PV array output current, V is the PV array output voltage. All of the constants in the above equation can be determined by examining the manufacturer rating of the SPV array and then the published or measured I-V curves of the array as described in Table 5.1. Simulated I-V and P-V curve of a SPV module for varying irradiance condition at 25 °C temperature are shown in Figs. 5.3 and 5.4, respectively. As a typical case, the Sun Power modules (SPR – 305) array is used to illustrate and verify the model. The model parameters are given in Table 5.1 and can be found in the datasheet [3].