Dominant/Lower Order Harmonic Injection Based Electric Fault Detection for DC Microgrids in Grid Coupled/Decoupled Scenarios

Microgrids are able to provide a more reliable and efficient energy supply than traditional grids, as they are able to operate independently from the main grid. This allows for better management of intermittent nature of renewable energy sources, such as solar and wind, and better integration of energy storage devices and electric vehicles. They are typically used to provide reliable, resilient, and cost-effective energy to a specific area. The protection design of DC microgrids is particularly difficult due to their low fault current contribution. Thus, traditional protection schemes such as over-current and short-circuit protection, may not be sufficient to protect DC network. However, the DC microgrids are more vulnerable to faults due to the lack of standard protection scheme. Therefore in this article, Hopping Discrete Fourier Transform (HDFT) based selective harmonic extraction method is used to identify the DC fault current, which is non-linear in nature, and is used to differentiate between normal and fault conditions. The proposed methodology helps to improve the accuracy of protection systems, as well as reduce the risk of false tripping. The Simulation results reveal that the proposed scheme is robust to changes in fault resistances and can be used to identify faults in grid-coupled/decoupled scenarios of microgrids. The effectiveness of the proposed protection scheme has been validated by the simulation results obtained using PSS/Sincal and MATLAB/Simulink. The proposed method is also compared to other existing methods and the results reveal that the proposed method is more accurate and reliable.