Control of a Three Phase Grid-Connected Photovoltaic System with Maximum Power Point Tracking

Abstract

The power output of a photovoltaic system is greatly dependent on environmental conditions such as solar irradiation and ambient temperature. Due to the nonlinear nature of these conditions, the power output of the PV system is nonlinear. As a result, interfacing its output to the electrical grid is not possible. In order to achieve a grid connected photovoltaic (PV) system, controlled maximum power point tracking techniques are needed to obtain a steady state output response. In this work, a two level grid-connected photovoltaic system is modelled and implemented in Matlab/Simulink with maximum power point tracking. Because the power output of the PV array is usually low, a boost converter is applied at the PV generator side to step up the voltage to a desired level necessary for the grid side inverter. Space vector pulse width modulated voltage source inverter is used to convert and transform the DC source voltage of the PV generator into three phase AC voltages and currents suitable for grid integration. The grid is operated at unity power factor and its active and reactive powers are both controlled. Phase locked loop (PLL) in d-q reference frame is used to detect the phase angle of the utility grid. Matlab/Simulink simulations are performed to confirm the results. Simulation results shows that the current controller makes the grid interface inverter output current to be in phase with the grid voltage.

Keywords: Photovoltaic (PV), Boost Converter, maximum power point tracking (MPPT), Perturb and Observe (PO), Space vector pulse width modulation (SVPWM), voltage oriented control (VOC), dc link voltage, Phase Locked Loop (PLL)