Measurement and Simulation on Stand-alone Photovoltaic Systems

Abstract: As a sustainable and cost-effective solution of energy supply in remote areas, standalone photovoltaic (SAPV) systems are widely used after the exploding developmentof photovoltaic cell industry in recent years. A wide variety of computer softwaretools are available for the dimensioning, analysis and optimization of solar energysystems. This thesis investigates the reliability of specified software tools using themethodology of comparing the measured data and simulation results.Two stand alone photovoltaic systems were established. One has a conventionalregulator and the other with a maximum power point tracking (MPPT) regulator.Their operation parameters were monitored and stored with data acquisition tools. Asurvey concerning the software tools that are capable for SAPV systems simulationwas implemented to select the appropriate software to be investigated. TRNSYS 16was selected to simulate the PVSA systems due to its modular structure andtremendous flexibility.The measurement results have shown that the MPPT system couldn’t producereasonable energy when the radiation is low. This enlarged the PV energy errors ofMPPT system together with the ideal MPPT output from simulations. On the contrary,the inconsistence of charging control between reality and simulation, which wasaffected by the fractional state of charge (FSOC) and battery voltage, was thedominating reason of PV energy errors of conventional system. Battery efficiencywhich was used to calculate FSOC became an important parameter in the simulationof charging/discharging control. All to all, the errors were either coming from the realoperation or the simulation of regulators.The comparisons of simulations and measurements have also shown that the onediode equivalent circuit model could correctly simulate the electrical performance ofsolar cells. Whereas the inbuilt thermal model of the solar cell and the battery modelstill need to be improved.