An Effective Adaptive Overcurrent Protection Scheme forMicrogrids

Abstract

Conventional distribution systems have some concerns related to the finite availability of conventional power sources and the green house impacts of these sources. These concerns createa significant interest in the research and development in renewable energy fields and encourage the generations from clean sources at the customer area. Basically renewable energy sources interfaced with the distribution system are called Distributed Generators (DGs) and hence forming a Microgrid (MG), which can operate either in grid connected or islanded modes. As a result of the major benefits that DG brings to distribution systems, its proliferation is anticipated to be increased, and this inevitably will change the traditional operation and protection principles of power distribution systems. This leads to some protection challenges such as difference in fault current level among different operating modes and bidirectional power flow which will lead to loss of coordination between protection devices. Based on challenges that face conventional protection systems due to DG insertion, new protection techniques have to be developed to mitigate negative impacts of DGs on protection system. One of these techniques is the adaptive overcurrent protection technique, in which the relays settings are automatically adapted to be continuously suitable for the current prevailing condition. Practical implementation of adaptive protection require relays with multi switch group factors and communication networks to connect relays and DGs with the system monitoring and controlling unit. In this thesis, an adaptive protection technique, based on topological analysis method, is presented to adapt relay settings for each configuration. The proposed adaptive protection scheme is applied to a part of the IEEE 13