Grid-connected Photovoltaic Power Generation System Model And Control Method Research

With the increasing depletion of fossil energy resources and the environmental problemsbrought about by burning fossil fuels, people are looking for efficient and renewable cleanenergy. Solar energy, with all the above advantages, has become a direction of human energytransition. Based on the existing model of grid connected photovoltaic power generationsystem, this thesis focuses on the control methods of photovoltaic grid connected system. Theworks are as follows:In order to improve the overall power transmission efficiency of photovoltaic powergeneration system and reduce system power loss, this thesis analyses the current photovoltaicmaximum power point tracking (MPPT) method in depth. Combined with a specific structureof the grid connected photovoltaic power system, a concept of generalized photovoltaicmaximum power point tracking is presented. Combining the impedance method and theconstant voltage tracking method, an improved constant voltage tracking (CVT) maximumpower tracking method is proposed, in which the maximum power tracking can be achievedby adjusting the voltage difference. The simulation results show that the improved CVTmethod has not only the advantages of fast tracking, but also advantages of good stability,smooth output curve and non-oscillatory.Taking boost photovoltaic power generation system as the research object, the boost typeDC converter model and control model under small signal are put forward based on the statespace averaging method. On the basis of this, the simulation results show that the stability ofthe system is enhanced by changing the DC converter and other control structures, whencompared with PD, PID and PI control methods. In addition, the PD and PID are easy tocause overshoot, so the PI regulator performs better in optimizing the system.The thesis puts forward the mathematical model of the inverter and control system of thephotovoltaic power generation systems including filter portion. Simulation shows that,Dead-Beat Control performs well in controlling inverter, and the LC filter also shows a goodperformance.