Load matching in a direct-coupled photovoltaic system-application to Thevenin's equivalent loads

Abstract

A methodology is developed for the assessment of load matching and further estimation of the optimum photovoltaic (PV) arrays arrangement over a prolonged period of time. The method calls for the calculation of the appropriate effectiveness factor defined as the ratio of the load energy over the maximum energy that can be produced by the PV array for a specific time period. The effectiveness factor depends on the PV array characteristics, the load characteristics, and the solar irradiance conditions. To produce realistic predictions for the effectiveness factor and the PV arrays arrangement with validity over long periods of time, the present statistical model describing irradiance employs a stochastic variation of solar radiation over a long period of time and not just a fixed diurnal variation as traditionally done in the past. Simulations are performed for the case of Thevenin's equivalent loads. In order to generalize the analysis, the simulation results are presented in a reduced form based on the values of the voltage and current corresponding to the maximum power of the PV array. The results are presented in multiple-curve comprehensive plots, which allow to determine the optimum photovoltaic array panel's arrangement without engaging sophisticated mathematical calculations.