Research On Grid-connected Photovoltaic System And Control Strategies

As the energy crisis and the pollution are serious, the exploitation of solar energyhas received more and more attention. The solar energy is transformed to electricenergy, and the electric energy is fed to the grid by the grid-connected photovoltaicsystem. This is the mostly form of the exploitation of solar energy.The control strategies of the grid-connected photovoltaic system are deeplyresearched. Firstly, the basic principium of solar battery is analyzed, and theequivalent model is educed, Through analyzing the I-V character of the solar battery,the solar battery is a nonlinear power, and the output power is influenced by the solarradiation and the environment temperature, for transforming the solar energy withgreat efficiency, the Maximum Power Point Tracking should be adopted. Throughcontrasting the methods of MPPT, improved P&Q and BOOST circuit are applied.Secondly, by contrasting the control manners of the current fed to the grid, thehysteresis control is adopted. For the stabilization of the grid-connected photovoltaicsystem, the double close loop control is introduced into the control of the inverter, thecurrent and the voltage of the grid are in synchronization, and the power factor is oneapproximately. Finally, islanding effect of the grid-connected photovoltaic system isresearched, the methods of the islanding detection are introduced, the scheme ofparameters optimization based on the method of active frequency drift with positivefeedback (AFDPF) is analyzed, thus can be taken as a good guideline in the analysisof the non detection zone (NDZ) of AFDPF.Simulation model due to the solar battery model, MPPT model, grid-connectedmodel are built on the platform of MATLAB/Simulink by using the modules of theSimPowerSystems. The simulation results confirm the schemes and control strategies.