An Analytical Review on State-of-the-Art Microgrid Protective Relaying and Coordination Techniques

In recent years, a trend of shifting from traditional power grids to modern smart grids has emerged the formation of microgrids (MGs), connecting low-voltage distributed generation (DG) units, loads and local storage apparatus to the medium voltage distribution system. This revolution in power distribution systems has pledged ample advantages for customers including reliability, quality, and efficiency of generated power. Furthermore, it also eliminates the necessity to construct long transmission lines resulting in cost saving and reduced power losses. In contrary to the benefits provided by MGs, protection of these entities is an enormously perplexing procedure predominantly due to dynamic behavior of MGs, bidirectional power flow, and high penetration of inverter-interfaced DG sources that interferes the conventional operation and coordination of protection relays. This article presents an analytical appraisal on state-of-the-art protection techniques to address problems associated with the MG protection. Advantages and disadvantages of each protection technique, as well as proper selection of protective relays suitable for each protection zone are discussed. Recommendations on protection procedures and effective techniques be employed to resolve the MG protection issues are also presented.