Optimized Overcurrent Relay Coordination in a Microgrid System

: Microgrids are a conglomeration of loads and distributed generators at a distribution level network. Since this network is no longer a single source fed network, the typical protection strategies may not be deployed. Reconfiguration is a topology changing feature that is visible in microgrid. This is also another factor that is to be considered while protecting the microgrid setup. This paper proposes a protection scheme that has normal and fault currents captured for all topologies of the microgrid. For each topology, the optimized time multiplier settings of overcurrent relays are computed using Dual Simplex Algorithm. This aids in clearing the fault as fast as possible from the network. A 21-bus microgrid system is considered and the optimized overcurrent relay coordination scheme is realized for the same.

Sensitivity Analysis on Linear Programming Problems with Trapezoidal Fuzzy Variables

In the real word, there are many problems which have linear programming models and sometimes it is necessary to formulate these models with parameters of uncertainty. Many numbers from these problems are linear programming problems with fuzzy variables. Some authors considered these problems and have developed various methods for solving these problems. Recently, Mahdavi-Amiri and Nasseri (2007) considered linear programming problems with trapezoidal fuzzy data and/or variables and stated a fuzzy simplex algorithm to solve these problems. Moreover, they developed the duality results in fuzzy environment and presented a dual simplex algorithm for solving linear programming problems with trapezoidal fuzzy variables. Here, the authors show that this presented dual simplex algorithm directly using the primal simplex tableau algorithm tenders the capability for sensitivity (or post optimality) analysis using primal simplex tableaus.