Study of Microgrid Fault Analysis During Grid-Connected and Islanded Operation

Microgrids (MGs) are becoming increasingly common because of their reduced infrastructure requirements, low power losses, environmental, and economic advantages. A small-scale network is mainly used at the distribution level, comprising multiple static, dynamic, and smart loads (SLs) such as electric vehicles (EVs) for grid integration and distributed generations (DGs) or distributed energy resources (DERs) that function as collective load or generation sources. MGs can run in an islanded mode in the event of a grid failure or operate in a grid-connected mode. Nonetheless, they have several operational challenges, including power quality issues, power system instability, dependability, and protection due to the varying power output of DERs depending on natural phenomena. It is initially required to research the fault characteristics of MGs to develop protective systems. Therefore, this paper analyses the performance of MGs and their DERs under different static and dynamic loads, and abnormal conditions in a grid-connected and standalone mode. The MATLAB SimPower system is used to simulate the modeling of MG and DERs as a small-scale distribution network. Different types of three-phases and phase-phase (Ph–Ph) fault scenarios are simulated both inside and outside the DGs to evaluate MG performance under abnormal conditions. The results show that both the voltage and frequency of the MG decrease from their typical levels following the fault occurrence. Additionally, it has been observed that the DERs’ contribution to maintaining the MG power quality is insufficient during the fault’s duration. However, post-fault resolution indicates that DERs progressively recover MG voltage and frequency to their nominal levels.