Fault analysis and protection of a microgrid

As penetration of distributed generation (DG) increases at the distribution level, managing these systems effectively becomes increasingly challenging. One proposed way to manage these systems is through the adoption of microgrids. A microgrid is a distribution level network made of several loads and DG sources that operate as a single aggregate load or generation source. Microgrids can either operate connected to the grid, or in the case of a grid fault, in an islanded mode. In this paper, we use Matlab Simulink´s SimPowerSystems to model a small portion of distribution network as if it were a microgrid. We add a mix of renewable DG sources and one dispatchable source, which at maximum output can produce more power than the average microgrid load. We then simulate the four major fault types at each bus in both grid-connect and island modes and analyze fault currents and voltage levels in order to determine how the protection scheme of the distribution network would need to be changed to facilitate microgrid functionality. We show that standard protection methods are insufficient and propose the use of digital relays connected to breakers.