Output Characteristic Analysis And Mismatch Losses Assessment Of Photovoltaic Arrays Under Partial Shading Conditions

Partial shading causes mismatch losses between photovoltaic(PV)modules in PV arrays,which significantly reduces the output power of PV arrays.The performance of a PV module depends mainly on the availability of solar irradiance.Partial shading leads to minor irradiance differences between adjacent PV modules,so mismatch occurs when the interconnected PV modules have different electrical characteristics.In addition to causing mismatch losses,these irradiance alterations can engender failures in maximum power point tracking and cause significant fluctuations in the output power of PV arrays.Therefore,it is of great significance to study the effect of partial shading on the electrical performance of PV arrays.The dependence of PV module parameters and thermodynamic performance on solar irradiance and temperature is determined under partial shading conditions,and the mismatch losses in PV arrays are quantified.The main work is as follows:A new mathematical model based on the basic data of PV manufacturers is proposed to evaluate the thermodynamic performance of PV modules.Time-varying acceleration coefficients particle swarm optimization is utilized to extract the physical parameters of the single-diode PV model.In the optimization process of the Time-varying acceleration coefficients particle swarm optimization,the time-varying mechanism to mitigate the premature convergence.The physical parameters of PV modules are especially sensitive to the changes of module temperature and solar irradiance.The output characteristics of PV modules under different temperature and irradiance conditions are studied.The thermodynamic performance assessment of PV modules is carried out with respect to the comparison of maximum power,fill factor,energy efficiency,exergy efficiency and power conversion efficiency of the PV modules.The simulation results show that the mathematical model can evaluate the thermodynamic performance of different types of PV modules.Based on the conducting state of blocking diode,a calculation algorithm with several subsection functions is proposed to quantify the mismatch losses in PV arrays under partial shading conditions.A single diode model without any approximation is employed to characterize the output characteristics of PV modules under standard conditions.The output characteristics of PV arrays with blocking diodes under partial shading conditions are further analyzed.The analytical solutions of short-circuit current,open-circuit voltage,maximal power point current and maximal power point voltage are derived with the Lambert W function.To describe the output characteristics of a PV array under complex shading conditions,the output characteristic equations of PV arrays are calculated in sections with the judgment of the blocking diodes states to quantify the mismatch losses of PV arrays.The simulation results of the output performance of three different types of PV arrays indicate that the calculation algorithm with several subsection functions has high accuracy in the mismatch losses assessment of PV arrays under partial shading conditions.