Research On The Method Of Islanding Detection For Grid-connected Distri Buted Generation

Increasingly serious environmental and energy issues, making the huge prospectsfor development of distributed generation, the way not only make the power systemflexibility and improve the stability, but also reduce the power loss, and greatly reducecosts. Distributed generation systems even contain the entire system, including thepower grid will lead to significant changes on the structure and operation of this gridoperation mode. This trend, the field of distributed power generation technology toensure that new and more complex power system up and running safe and reliable, hasbecome a important issue, as an important part of the islanding detection technology, itincreasingly been the focus.At present, the classification issued by the islanding detection can detect thelocation divided into two categories: distributed power supply side of the detectionmethod and the grid side of the detection method, also called local detection and remotedetection. The detection method of the power supply side of the receipt of differenttypes of distributed power the impact of the grid side of the detection rule is not subjectto the type of distributed power. Grid side of the remote detection method is rarely usedin practical applications, because of high costs, technical requirements, difficult toachieve. According to whether or not to impose the disturbance detection method can bedivided into two categories: passive islanding detection and active islanding detection.Passive islanding detection method prevalent defects blind, active islanding detectionmethod, although there is a high sensitivity, but can not overcome the impact of powerquality, active and system stability. The main work done in this paper for the followingthree aspects:First, this paper presents an active islanding detection method for a distributedresource (DG) unit which is coupled to a utility grid through grid-connected converter.Second, with the proposed method which is based on adding periodical disturbingcurrent through current controller of the interface voltage-sourced inverter, islandingcan be effectively detected. But when the disturbing current remains unchanged, thismethod still has some shortages, so this article improved it and used a changedtime-varying disturbing current ending with faster detecting time and less disturbing.In the end, the studies reported in this paper are based on time-domain simulationsin the MATLAB environment. And the results show that the proposed islandingdetection method always meets the two-second UL detection requirement.