Robust Unified Multi Diverse Protection Schemes for Low Voltage Microgrid

A microgrid (MG) is characterized by an arrangement of renewable energy sources (RES) and loads connected together to the distribution system. With the high dispersion of distributed generations (DG) in microgrids, which is inevitable, the distribution system will experience diverse challenges not only in its performance but also in the protection set-up. The lack of a comprehensive applicable protection scheme, which must be attuned to islanded and grid-connected modes of microgrid operation, is a key problem. The problem becomes more challenging and complex in an islanded operation of a microgrid (MG) due to limited fault current contribution by inverter based DGs. Therefore, conventional protection strategies cannot be applied in a radial distribution system with DGs. The lack of comprehensive protection schemes, which must be attuned with islanded and grid-connected modes of microgrid operation, is a challenging task to be implemented. To grasp the superlative protection scheme for MGs, the combined action of different protection strategies is required. Extensive research on the development of MG protection strategies reveals their incompetency to cater for protection of every component of the entire microgrid in its prevailing conditions being employed in solo-mode and also that no scheme is able to work without communication assistance. The current work proposes the comprehensive implementation of communication-less unified diverse protection schemes that include current differential relays, directional and non-directional overcurrent conventional IEC (International Electrotechnical Commission) standard-based overcurrent relays, and novel non-standard voltage-current relays. The assembly and graphical representation of proposed relays for each scheme are developed in MATLAB/Simulink during the simulation. The accomplished results of these diverse protection schemes are validated through simulations applied to the benchmark microgrid system using an industrial software package called ETAP (Electrical Transient Analyzer Program).