Research On Anti-islanding Strategy Based On Grid-connected PV System

PV grid connected power generation is a kind of power generation which is vigorously developed and supported. With the transformation of energy structure in the future, it will become a very important element in the power system. However, the isolated island effect is one of the key problems in grid connected photovoltaic power generation technology. It will cause problems such as personal safety, economic benefits, power quality and so on. Therefore, this paper focuses on the deep research of the anti-island strategy of photovoltaic grid connected generation system.The research background, significance and research status of the anti-island strategy of photovoltaic grid connected generation system are described. The advantages and disadvantages of various anti-island strategies and their applications are analyzed and compared, which provides a reference for the study of the anti-island strategy.Topological structure and control method of single-phase and three-phase photovoltaic grid connected generation system are analyzed. The simulation model of single-phase and three-phase photovoltaic grid connected generation system is established based PSCAD, and the simulation analysis is carried out. The simulation results verify the correctness of the model and control method, which lays a theoretical foundation for the further research of the anti-island strategy.A new active anti-island strategy based on phase locked angle disturbance is proposed. The reference current lock phase is introduced to a tiny with the sinusoidal variation of the disturbance and the reference current joined a second harmonic. When power off, the islanding of grid connected PV system can be judged by comparing the second harmonic voltage extracted from the common point with the threshold. A simulation model of anti-island based on phase locked angle disturbance is established. Simulation is carried out for different types of load, and the correctness of the method is verified.A hybrid PV inverter anti-island strategy is proposed. The over-under voltage / frequency method is combined with active power perturbation method. The real time analysis of the matching degree between the output of the inverter and the load power are conducted, which will control the photovoltaic grid connected generation system switching between two anti-island operating modes. This strategy can solve the problem of passive anti-islanding strategy has non- detection zone when the power matched, and it also can solve the problem of anti-islanding affecting power quality. The hybrid method is applied to the three-phase photovoltaic grid connected power generation system, and the simulation is carried out for different conditions.