Research On Islanding Detection Technology Of Photovoltaic Grid-Connected Inverter

China’s energy consumption mainly relies on traditional petrochemical fuels.Recently,the petrochemical energy crisis and environmental problems in our country have become more and more serious with the development of social economy.It is imminent to change our energy industrial structure and develop new energy sources.As solar energy resources have the advantages of being clean,pollution-free,safe,reliable,economical,and inexhaustible,it has played an irreplaceable role in the renewable energy sources.The new energy power generation technologies represented by photovoltaic power generation technologies have received increasing attention from the international community.In photovoltaic power generation systems,distributed power generation systems have a very important position.Distributed power supplies provide energy for the power grid and local loads.As more and more distributed photovoltaic power generation systems are used in the energy industry,many potential grid protection issues have gradually attracted people’s attention.One of the difficulties is that How to detect the islanding.The islanding can cause serious damage to power quality,damage to electrical equipment,and threats to the safety of operating personnel.Therefore,the occurrence of islanding should be avoided.The relevant anti-islanding equipment should be used to monitor the operation of the system in real time.When islanding occurs,the islanding state is detected and the islanding protection device is triggered so that the photovoltaic grid-connected inverter can be cut off from the main grid as soon as possible to avoid the aforementioned hazards.This paper takes the three-phase photovoltaic grid-connected inverter as the research object,studies the islanding detection existing in the system,discusses the influence of the relevant parameters on the distribution of Non-Detection Zone,and according to the existing deficiencies of the anti-islanding strategies,An improved islanding detection algorithm based on reactive power disturbance is proposed.This paper expounds the research background,cause and harm of islanding,and analyzes the current research status of islanding detection technology.The three-phase photovoltaic grid-connected inverter is modeled based on the constant power control strategy of the inverter to achieve flexible control of active/reactive power,which lays the foundation for the subsequent research on islanding detection algorithms.A comprehensive study of the mechanism of islanding,comparative analysis of several common islanding detection methods such as remote detection,passive detection and active detection methods.At the same time,the description method of non-detection zone is introduced.The non-detection zone of common anti-islanding strategy is described by Q_f0×C_norm description method.The influence of related parameters on the distribution of non-detection zone is analyzed.Based on the participating scientific research projects,several improvements are proposed for the existing assessment criteria for non-detection zone.Based on the analysis and research of common islanding detection algorithms and their non-detection zone,the advantages of anti-islanding strategies based on reactive power disturbances are described,and the basic principles are analyzed.Aiming at the shortcomings of the existing reactive power disturbance islanding detection methods,such as low efficiency in islanding detection and large impact on power quality,a novel islanding detection method based on reactive power disturbance is proposed and simulated.And the experiment verified the islanding detection algorithm proposed in this paper.