Enes Durbaba

Abstract

In this thesis, grid connected photovoltaic system with the DC to DC buck-boost, boost converters and DC/AC unipolar switched inverter has been analyzed. Two different DC to DC converters have been used to extract the maximum power available from the solar panel. The single-phase unipolar inverter has been used for the interface between the DC to DC converter and grid.

In this study, the leakage current flowing through parasitic capacitor of the photovoltaic panel has been taken into consideration and minimized with the help of inverter design. The time variation of the common mode voltage of the inverter causes the leakage current. Therefore, the existing photovoltaic inverter topologies have been investigated and a new photovoltaic inverter which provides the constant common mode voltage has been proposed. The mathematical models of the PV inverters have been analyzed in the Matlab/Simulink and tested in power quality laboratory.

Also, the effect of the model predictive current control on determination of maximum power point of the photovoltaic modules has been studied to determine the fast and robust maximum power point tracking system. The voltage controlled perturb and observe algorithm with the linear controllers (i.e, proportional-integral type controller) and the voltage controlled perturb and observe with the predictive current control method have been compared and simulation of these methods have been carried out in MATLAB/Simulink. Also, the particle swarm optimization algorithm is used in the simulation and two different MPPT algorithms are compared.

Keywords: PV inverter, Common mode voltage, Leakage current, Maximum power point tracking, Predictive current control, Particle swarm optimization, Perturb and observe method, DC to DC converters