Protecting a microgrid at the case of grid connected and disconnected mode

ebrahim faraji

Abstract


Reducing fossil fuel resources and adverse environmental effects and low efficiency of traditional electricity networks, tend to increase the production of electricity near the charge and the distribution of networks using renewable sources.One of the basic strategies in order to solve the so called problems posed by the use of microgrids. A series of small sources of energy in the voltage level distribution are called microgrid. Microgrid operation occurs in two cases connected to the network and separate from them. In this study, a differential protection scheme to protect a microgrid using the time-frequency conversion such as S Morin conveys are presented. Initially, consecutive bus currents are measured and processed using S conversion and their time-frequency contours are achieved. Content of time-frequency fault signals of current is calculated by the energy spectrum contours, and then the differential energy to record the error patterns in the case of the microgrid connected to the network or harmonic distortion is calculated. The efficiency of the proposed method in different types of errors (symmetric or asymmetric) and high impedance error in the microgrid is evaluated in radial or circular structures. A threshold value for the energy difference can be stimulated at the right time to send a signal about 2 to 3 cycles since the occurrence of error is very convenient. The results show that the protection scheme based on Differential energy of the microgrid can protect against conditions of various errors effectively. Therefore, the proposed approach is the right choice for wide area protection. Pscad software is used to simulate microgrid and MATLAB software to analyze the results of simulation.

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DOI: http://dx.doi.org/10.1000/ijses.v2i2.94

Copyright (c) 2016 International Journal Series in Engineering Science (IJSES) (ISSN: 2455-3328)

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