| With the global energy crisis and worsen of environment pollution taken into consideration, developing the utilization of clean renewable energy has been imperative. As a novel green and renewable energy, the solar energy is abundant, economic and non-pollution. So its application attracts lots of attentions. Solar photovoltaic technology is currently one of the world's most clean, most realistic and best prospects for large-scale development and utilization technologies. The grid-connected solar energy photovoltaic power system as one of the main utilization of solar energy, has become a hot spot in the world. This paper researches the grid-connected PV system with maximum power point tracking (MPPT) and islanding detection.First, summarizing the composing of the photovoltaic energy system, introducing the presently technology application of the system in our country and abroad and according to different needs classing structures.Second, describing in detail the working principle of solar cells, giving the equivalent circuit model, analyzing the I-V, P-V output characteristics of PV array and external factors on them and using the software to build the simulation of the output characteristic for the solar cell under different temperature and isolation.Third, analyzing the MPPT principle, comparing several common MPPT methods and a maximum power point simulation platform has been set up. Based on the disturbance-observer method and the conductance increment method, a method of selecting different length of sync according to the different tracking stages is proposed and simulated. The simulation result confirms the feasibility of the method.Last, introducing the definition of an island effect and its harm to the grid, analyzing the causes of island states, describing the international and domestic common standards for islanding detection and several common methods of islanding detection. There is also a PSIM simulation of under-voltage islanding detection method.
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