Research Of Inverter For Grid-connected PV System And Reliability Analysis

With an increasingly serious problem of environmental pollution and energy shortages, looking for a large reserve, clean new energy has risen to the world's agenda. As one of the best environmentally-friendly energy sources, solar energy has been applied more and more widely by human. This paper deeply researches the grid-connected photovoltaic (PV) system and does simulations with the main objection of transforming the solar energy into electrical energy maximum and no pollution. It has realistic significance to do researches and experiments on the grid-connected PV system. And the grid-connected PV inverter is one of the necessary equipments of the grid-connected PV system. The efficiency and reliability of inverter will influence the performance of the whole system. So an effective inverter suited to the grid-connected PV system is presented in this thesis.This paper bases on grid-connected PV system as research object and focuses on single-phase grid-connected PV systems to conduct a comprehensive analysis, and then does a detail analysis and simulation from the main circuit topology of grid-connected system, control strategies, system parameters, anti-island effect as well as reliability analysis.Firstly, the status of PV system home and abroad is introduced. The basic structure and types of the PV source, advantages and disadvantages, development trend, requirements on inverter are also presented. An overall understanding of the system is set up naturally.Secondly, this paper discusses the topology of the main circuit of the inverter. In accordance with the actual situation, it is better to choose two stages transform structure, DC/DC converter with Boost topology structure and DC/AC inverter with full-bridge inverter, this two parts are connected by DClink. This paper discusses control mode of output current of the inverter and then determines the overall program of grid-connected PV system. With the development of digital signal processors (DSP), it is possible that some advanced control strategies can be applied to the grid-connected PV system. This paper takes digital signal processor TMS320F2812 from TI Company as core cell of control circuits. The design of driver and protection circuits and system's EMC are introduced in detail. MATLAB/Simulink toolboxes are used to build the whole circuit model and the simulation study.Then as we know islanding effect relates to the security issues of the grid-connected PV system. The paper analyzes the causes and effects as well as detection methods used now, such as passive and active and external islanding detection methods. According to the features of the system designed this paper, the voltage feed forward position feedback disturbance method is used to solve the problem, and then this paper builds the MATLAB model based on the method and carries out the simulation. The simulation result shows that the method is feasible and up to the demand of IEEE Std.2000-929.Reliability study of PV system has an important impact on the economic operation and making investment decision to the entire system. This paper does reliability analysis of the grid-connected PV system according to the basal components. Doing analysis on the grid-connected PV system meeting a certain level reliability has played a guiding role to its use.