• Energy Research

Abstract A new method of tracking the maximum power point (MPP) of a photovoltaic (PV) module exploiting the effects of the inherent characteristic resistances of the photovoltaic cells is proposed in this paper. An analysis of the mathematical model of the IV characteristic of the PV module revealed a possibility of estimating the MPP from its characteristic parameters such as the open circuit voltage (Voc), short circuit current (Isc), series resistance (Rse) and the shunt resistance (Rsh). The first stage of estimation process, for obtaining the voltage at the MPP, was facilitated by the effects of the series and shunt resistance on the IV characteristic of the PV module and the second stage of estimation process was facilitated by the combined process of the first stage of estimation and the condition for extracting the maximum power from the mathematical model of the pv characteristic of the PV module. The estimated voltage at the MPP in the second stage of estimation was found very close to the true MPP. The effectiveness of tracking the MPP with the proposed method has closely matched with the true MPP. This was validated by the results obtained through simulations and experiments. An analysis of the effects of degradation on the performance of the proposed technique showed that the performance was excellent during the first few years and with the update of characteristic resistances in the proposed algorithm the performance was found to be almost invariant. The successful experimental results obtained with a 100 Wp PV module indicate that the technique can be favourably implemented for standalone PV power systems.

Abstract This paper presents a new method of tracking global maximum power point (GMPP) under non-uniform irradiation of the photovoltaic (PV) array and also suitable under uniform irradiation. From a comprehensive analysis of the PV characteristic it was found that the slope of the PV characteristic was constant up to a voltage point just less than the maximum power point voltage. This constancy in slope was effectively utilized to estimate the maximum power which can be delivered by the PV array. The proposal in this paper was based on estimating the maximum PV power in various preplanned segments by measuring the slopes at different strategic points. These strategic points were decided based on the measured open circuit voltage of the PV array. After measuring the slopes at the strategic points, the estimation will be effected and the segment in which the global maximum power occurs was computed. Upon determination of the optimal segment, the conventional perturb and observe technique was deployed in the optimal segment to reach the global maximum power point. Once the GMPP was reached any change in the level of irradiation or irradiation pattern will be sensed by monitoring the PV array current. Computer Simulation and experimental evaluation were made and conformed that the proposed method of GMPP tracking worked effectively yielding excellent steady state tracking efficiency with no divergence.