Research On Islanding Detection Method Of Distributed Photovoltaic Power Generation System

With the problems of environment pollution,gradually exhausted fossil energies,and energy safe providing,the development and utilization of renewable energy,which is represented by photovoltaic power generation,has been paid more and more attention by the international community.Compared with the traditional power generation technology,photovoltaic power generation has the advantages of sustainable energy,safety and environmental protection,and economic operation.Recently,China is conducting the energy revolution and self-innovation to promote the rapid development of PV industry,where the distributed photovoltaic power generation is an important development direction of photovoltaic power generation.As one of the important development direction of photovoltaic power generation,distributed photovoltaic(PV)grid connected power generation has obtained rap id development.As more and more distributed photovoltaic power generation system is connected to the power grid,it also brings some new problems.Islanding effect will cause the failure of the recloser,the personal injury of the maintenance personnel an d the damage of the electrical equipment.In this paper,the existing islanding detection methods are analyzed and their performance is evaluated.Based on this,an adaptive islanding detection algorithm based on MPPT is proposed.First of all,a two grade non-isolated distributed photovoltaic system is set up,where the using the incremental conductance method is used to track the maximum power point,and the LCL filter,active damping and PR control parameters are designed with the theory of instantaneous power under two-phase static coordinate realizing the control of grid connected inverter.Secondly,this paper analyzes the mechanism and harm of islanding effect,introduces the relevant standards of islanding detection at home and abroad,studies the common active and passive islanding detection methods,and analyzes their advantages and disadvantages.In this paper,the detection blind zone of several common islanding detection methods is described,and the performance of the islanding detection algorithm is evaluated.Finally,aiming at the existing islanding detection methods,this paper proposes an adaptive islanding detection method based on the MPPT model,which realizes the disturbance on MPPT based on the periodic disturbance of the duty ratio D in Boost circuit,thereby affecting the PV output power,and determine the state of the island operation by detecting and connecting point voltage which is influenced by the disturbance on the island operation condition.The disturbance of the duty cycle D is obtained by the real-time calculation of the grid voltage,which effectively reduces the power loss,and the detection blind area is eliminated with the worst condition being considered when the parameters are designed.Then,the effectiveness of the proposed islanding detection algorithm is verified by simulation and experiment,and the power loss caused by the algorithm is analyzed and calculated.