Time-domain protection scheme for inverter-dominated islanded microgrid using low-bandwidth communication channels

This paper introduces a low-bandwidth communication time-domain protection scheme for inverter-dominated islanded microgrids. The developed scheme relies on pre- and post-fault current samples at line ends, and requires only sharing one value per phase between both line ends. Firstly, the identification function (IF) is developed by multiplying the phase current samples by its derivative at each line end. Next, the fault identification index (FII) is deduced to compare the pre- and post-fault identification functions at each line end. In order to differentiate between internal faults and other scenarios, the differential fault detection index (DFDI) is formulated via calculating the difference between both fault identification indices at both line ends. The developed scheme is validated by simulating the modified IEEE 33-bus microgrid on PSCAD/EMTDC, and different scenarios are carried out considering external and internal faults. Besides, the influence of different factors, such as high resistance faults and measurement errors, is investigated. Moreover, a real-time hardwarein-loop is conducted to verify the performance of the developed scheme. Compared with the existing techniques, the developed scheme is immune to the HRFs and measurements errors, and is independent of the inverters' control strategies.