Research On Control Methods Of Photovoltaic Grid-connected Inverters

Since the 21 st century, to solve the gradually serious of the energy shortages and environmental pollution problems, Solar power with its unique advantages has received the attention of the world. However, in grid-connected photovoltaic(PV) system, external factors can affect the reliability, stability and efficiency of the system. Therefore, for realizing the coordinated development of economy and environment by making better use of solar power,all kinds of technology of photovoltaic power generation system should be carried on. This paper mainly involves two key technologies of PV system: MPPT Control Technology and PV Grid Control Technology.Firstly, the classification of the photovoltaic(PV) grid inverter is introduced and the advantages and disadvantages of the structure of grid inverter is compared in detail. Lastly,this paper chose to make a study on the Single-phase two-stage inverter structure. After then,the working principle of the Pre-Boost circuit and Stage full-bridge inverter circuit is analyzed.Secondly, for investigating the output characteristics of photovoltaic cells, a mathematical model that can meet the practical engineering requirement is established and made the simulation analysis. Based on the simulation research of battery output characteristics, the significance of the maximum power point tracking is proposed and the maximum power point tracking(MPPT) common technology is analyzed. Furthermore, an improved control method is proposed, and the control method is a combination of disturbance observer method with Newton’s method. The mathematical model of each module of the system is established and simulated. The simulation results show that this method can rapidly and stably track the maximum power point.Thirdly, based on the clear control objectives, the direct control of the AC side output current is adopted to control the output of photovoltaic grid connected inverter. On the basis of analysis and comparison of several common grid current control modes, a control strategy based on the Voltage feedforward compensation of double-loop PWM is proposed and simulated. The simulation results show that the method of power grid tracking control has a good effect.Finally, on the basis of the analysis and research, simulation model to establish the 1KW individual PV. And calculate the parameters of the system components, the establishment of a system simulation model. The simulation results show that the methods are taken on the system has a good effect.