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The GS is an iterative technique for solving the non-linear transcendental equations. The generalized form of equation to be solved using GS can be represented as [15, 20]:

(1.30)

Where ‘x’ is the variable to be determined and ‘k’ denotes the number of iterations, x^k+1 is the new value obtained and x^k represents the old value. The algorithm converges if the absolute error of new and old values is less than the tolerance of 10^-6. In this work, the GS method is employed to determine the unknown parameters by solving the equations of (1.10), (1.11), and (1.13) to get the values of V_t, R_se, and R_sh with the input values of V_mpp, I_mpp, V_oc, I_sc, and N_s, and initialization of V_t, R_se, and R_sh. Then, the obtained values of V_t, R_se, and R_sh are used to compute the unknown parameters of I_LG and I_sat. The detailed procedure on determination of five parameters of PV module is described in [15]. However, under dynamic environmental condition the GS method is failed to obtain the converged solution as the initial values cannot be chosen appropriately. Hence, a variant of GS method called Successive Under Relaxation was used to solve (1.28) and (1.29) to obtain the voltage and current at MPP under varying environmental condition as given in [15]. However, the appropriate choice of selection of relaxation factor should be made for faster convergence of solution else may result in slow convergence as SUR exhibits linear convergence characteristics [21].