Comparison of model based MPPT and exact MPPT for current equalization in partially shaded PV strings

Current equalization approach for distributed maximum power point tracking (DMPPT) is more efficient as compared to other schemes under partial shading conditions. The operating voltage of each PV module of the shaded string is maintained at its MPP voltage (V_MP) by injecting suitable compensation current by a dc-dc converter connected across each module. The basic idea of current equalization scheme is to determine the MPP voltage for each individual PV module in the partially shaded string. In the present work, the MPP voltage is determined using two methods - the model based MPP voltage determination and the exact MPP voltage determination. Subsequently, a comparison of the model based MPPT and the exact MPPT for current equalization is given in this paper. Analysis and simulation results of this comparison for a partially shaded PV string are presented. The power output with exact MPPT method improves by ~ 10% when compared to model based method.