Font Size: a A A

Research On Islanding Detection Methods For Multiple Inverters Based Distributed Generation Units

Posted on:2020-06-17Degree:MasterType:Thesis
Country:ChinaCandidate:G K WangFull Text:PDF
GTID:2392330572477850Subject:Power system and its automation
Abstract/Summary:PDF Full Text Request
With the rapid development of photovoltaic power generation,wind power generation and energy storage system,the penetration of distributed power generation system based on renewable energy is increasing.Distributed generation improves the flexibility and reliability of power system,which is of great significance to the sustainable development of China.Therefore,the distributed generation has a broad prospect and accord with the national low-carbon economic development strategy.However,there exists the problem of islanding in distributed generation system.Islanding means that when isolated from the utility trips due to faults or maintenance, the distributed grid-connected generation system at the user end fails to detect the outage status in time and shutting down,thus forming an islanded system composed by the distributed generation system and the local load.Islanding can lead to instability of the voltage amplitude and frequency.And as the distributed systems are directly connected to user-side devices,it can seriously threaten the safety of electrical equipment and personnel.In order to detect the islanding timely and effectively,a variety of islanding detection methods have been proposed,which can be divided into two categories:communication-based islanding detection technology and local islanding detection technology.However,the islanding detection technology of distributed generation system with multiple inverters connected to grid in parallel is not mature currently.In multiple inverters system,the conventional islanding detection methods can cause the counteraction effect and affect the power quality seriously.Therefore,the islanding detection method which is suitable for application in multiple inverters based distributed generation system is worth studying.In this paper,firstly,the mechanism and hazards of islanding effect are analyzed, and the research status of islanding detection technology is introduced.The definition of non-detection zone is presented,and the requirements for islanding detection performance of utility interface standards in various countries are introduced.Then the operational principles of passive islanding detection methods and active islanding detection methods are elaborated in detail,and their advantages and disadvantages are analyzed respectively.In addition,the counteraction in multiple inverters system is analyzed,and the islanding detection methods proposed for multiple inverters system are introduced.Two islanding detection methods which are suitable for application in multiple inverters system are proposed in this paper.One method is the hybrid method combing voltage unbalance/total harmonic distortion and bilateral reactive power variation.The design principle of hybrid method is analyzed,and the operational principle of the proposed method is introduced.Then the detection performance is analyzed in terms of non-detection zone,detection speed and power quality effect.Comparison analysis reveals that the proposed method has a more satisfactory islanding detection performance for application in inverter-based distributed generation units.Simulation and experimental results under various conditions were carried out to verify the islanding detection performance of the proposed method.The other method is synchronized reactive power variation method for islanding detection using high-frequency signal injection.Firstly,the operational principle and the parameter design of the proposed method are introduced in detail,and the initial operation and the operational principle under the large fluctuation of grid voltage are demonstrated.Then,based on the parameter design,the influence on power quality of the proposed method in terms of total harmonic distortion and power factor is analyzed.Simulation studies are carried out to verify the effectiveness of the proposed islanding detection method under various system conditions.
Keywords/Search Tags:Distributed generation, grid-connected inverter, islanding detection, non-detection zone
PDF Full Text Request
Related items