Reliability Assessment and Comparison between Centralized and Distributed Energy Management System in Islanding Microgrid

As the number of DER in the microgrid increases, the electrical interfaces and communication interactions are more sophisticated and frequent than ever, which poses a great challenge for microgrid Energy Management System (EMS). Efforts has been made to address this challenge. The solutions generally fall into two categories: centralized and distributed solution. Comparing with centralized EMS, distributed EMS is commonly considered as a more promising and reliable approach. Nonetheless, the current microgrid reliability research are focused on the physical layer of microgrid, such as overhead lines, transformers, circuit breakers and the DER device itself. The reliability analysis that considers controller failure and EMS framework are not reported in current publications. In this paper, a general reliability assessment methodology based on Monte Carlo simulation is presented to assess the reliability of both centralized EMS and distributed EMS in islanding microgrid. Different performance metrics such as system-average-interruption-frequency-index (SAIFI) and expected-energy-not-supplied (EENS) are used to quantify and evaluate the reliability. Simulation results indicates that using the same controller, the microgrid with distributed EMS is able to achieve better reliability indices, and the distributed EMS can achieve same level of reliability using less reliable controllers.