A Study On Protect Effection And Admittance Capacity Of Distributed Generation Connected To Power Grid

Along with the rapid development of the social economy, science and technology,human’s energy demand is also continue to increase. However, because of the growingglobal energy shortage, the distributed generation as a new way is getting more and moreattention from people, and constantly developing to mature. DGs have many advantagessuch as environmental protection, energy conservation and economic flexible, but afterthey connect to the distribution network, they will impact such as the operating mode, thevoltage distribution, relay protection, and stability and security of the grid, and so on.This paper firstly analyzes the different types of DGs, including their characteristicsand influence to grid. Then the paper focuses on the study of the mathematical model thatsingle DG connects to different location of the grid. Through the examples contrast, thepaper compares the different effects of the current protection with the DG’s differentoutput capacity and access location, and get the allowed position and capacity of DGunder the no impaction of the protection selectivity and sensitivity.Further, the paper discusses the influence of the fault current that least one of two DGconnect to upper, downstream or adjacent side the fault, and establishes the mathematicalmodel under various conditions. Then examples are used to compare the influences offault curren, as well as two DGs’effect to the line current respectively. Then themathematical model that the admittance capacity of the DGs connect to grid is built upunder combined limited conditions.Finally, based on photovoltaic cells as a tangible model, this paper applies Matlab tobuilt photovoltaic battery simulation model that connects to 10kV grid, and verifies thecorrectness and rationality of each simulation model. When single or multiple DGsconnect to 10kV grid, because of the different position of the failure, they will change thepower trend, and different lines’short-circuit current, as will as support system nodes’voltage. The paper makes use of experiment to compare these effects, and the simulationresults validate the former analysis that DGs will effect grid’s relay protect effection, andthe system simulation model is also validated correctly.