Seamless Transition of a Microgrid Between Grid-Connected and Islanded Mode

This thesis focuses on improving the behavior of inverters during transition periods from islanded mode to grid-connected mode (GC) and vice-versa. A systematic approach is presented to add smart features to inverters to enhance their capability to cope with sudden changes in the power system. The importance of microgrids lies in their ability to provide a stable and reliable source of power for critical loads in the presence of faults. For this purpose, a design is proposed consisting of a distributed energy resource (DER), battery energy storage system (BESS) and a load connected through a bypass switch with the main utility distribution substation. The BESS is connected to the AC distribution feeder through a smart inverter that is controlled in both modes of operations. The system was tested using MATLAB/Simulink models and the results show proof of the seamless transition between the two modes of operation. The cost of building the software system was unnoticeable due to the availability of a MATLAB license but the real cost of the hardware needed to build the system will be moderate though the importance will be significant