Performance response tests on a multivariable fuzzy rule-based relay for short circuits in AC micro-grids

This paper presents the results of offline and online performance tests on a new multivariable fuzzy rule-based (MFR) relay for AC micro-grids. The relay is based on measurement of four critical parameters (P, Q, V and I) and fuzzy logic implementation of rules framed on the basis of these parameters. The online test is performed by embedding the relay in a micro-grid test bed capable of grid-connection. The offline test is performed by simulating High, Normal and Low states of the four parameters using proper combination of digital signal sources to implement short circuits (SCs) in SIMPOWERSystems® software. In both offline and online tests, the faults simulated are standard SCs in the utility and micro-grid. The results of both offline and online tests are similar, and show that the MFR relay outputs logic 1 during SC faults. The relay also outputs logic 0 before and after the SC faults for both offline and online tests.