The Research On Photovoltaic Power Flexible Grid-connected In Microgrid Based On H-infinity Control

Photovoltaic generation has become the focus of the development of new energy, with the advantage of the huge reserves, cleanness and non-pollution. Especially the distributed photovoltaic grid-connected generation system, has become the main development direction of photovoltaic generation system, with the traits of high flexibility, no noise, construction combination. At the same time, the grid-connection of a large number of distributed photovoltaic generation has a great impact on power grid. However, this problem has been solved because of the appearance of Microgrid. Microgrid provides feasible and effective new ways for grid-connection scale applications of new energy and renewable energy, improving the complementarities and the comprehensive technical economic benefits of different types of distributed generation, which is in line with China's new energy generation and sustainable development strategic requirements, and provide the necessary technical foundation for the realization of the smart grid. The traditional control methods of the photovoltaic generation system has been unable to meet the flexible control requirements by Microgrid, therefore, the flexible grid-connection control technology research of photovoltaic in Microgrid is of great significance.The focus of this thesis, is to research on the H-infinity control method of the flexible grid-connection of photovoltaic power. First, this thesis exposits the concept, connotation and technical features of the smart grid and Microgrid in detail, concisely introduces to the basic principle and structural characteristics of the all kinds of micro power, studies the design requirements, the existing control method, and the main research direction of Microgrid, further illustrates the importance of studying the photovoltaic generation system control method applicable to Microgrid. Second, a photovoltaic array simulation model based on four basic parameters under the MATLAB/ simulink environment is given, laying the research foundation for further study of the photovoltaic generation system. Aiming at the shortcomings of traditional photovoltaic system MPPT algorithm, an improved MPPT algorithm based on variable-step and power prediction is proposed, which overcomes the contradiction between the tracking speed and voltage fluctuations in the perturbation method MPPT. Second, in order to meet the flexible control demand of Microgrid and to improve the controllability of the photovoltaic power, this paper proposes a given power tracking algorithm based on variable-step and power prediction, which increases a work mode on the original MPPT, changing the traditional photovoltaic power passive position for the more participation of control and adjustment in Microgrid by photovoltaic power. Finally, the H-infinity control theory has carried on concise exposition, and the theory is applied to flexible grid-connection control of photovoltaic power. A controller design method of flexible grid-connection optimization controller based on H-infinity is proposed. A photovoltaic generation system grid-connection control mathematical model is established, and the voltage tracking H-infinity controller is designed using the proposed method. The stability and robustness of the designed system has been theoretically analyzed. Three conditions of the control system has been verified through MATLAB/Simulink platform, which proves that photovoltaic generation grid-connection system using the H-infinity controller has the advantages of accurate control, high adaptability and strong robustness.