Study On Single Phase Grid Connected Control Strategy For Photovoltaic System

As the speed of the energy consumption is becoming more and more fast, people have to turn to use the clean and renewable energy to face the increasing environmental pollution. The solar energy, as a safe clean and renewable energy, has an important way to research. Therefore, this thesis will studied in two aspects of the grid connected photovoltaic control technology in detail, fix on the maximum power tracking problem on the one hand and fix on the grid connected control system on the other hand.Firstly, this thesis selects the two-stage structure as the research object by analyzing the different topology of single-phase photovoltaic grid connected inverter, establishing the mathematical model of photovoltaic cells through analysising of the working principle of photovoltaic cells, expounds the common method of the maximum power point tracking, and using the method of perturbation and observation to find the MPP. Secondly, according to the single-phase grid connected inverter circuit structure, we can come out the mathematical model of the single-phase grid connected inverter, through the control method of the synchronous rotating coordinate system in three-phase grid connected inverter to come out the control method of single phase grid connected inverter. And build the virtual voltage and current by useing the method of the Nikai Hiroyoshi integral, and then, use the vector control method based on grid voltage orientation. On this basis, establishes the PI control strategy of current inner loop and voltage outer loop. Thirdly, analysis the control methods of the grid connected inverter SPWM pulse width modulation and phase locked loop control. To ensure that the grid connected current and the grid voltage are strictly in the same frequency and phase. Finally, realizing the control of the whole single phase photovoltaic grid connected generation system, the simulation results show that the control method is feasible.