Comparison of Non-Communication based DC Load Shedding Schemes

Whenever the total power that can be provided by the distributed energy resources (DERs) is less than the total power demand of the loads, the DC bus voltages start to fall which could lead to power collapse. This paper investigates and compares the performances of the existing non-communication based (decentralized) load shedding schemes in a direct current (DC) microgrid to protect the integrity of the microgrid under a large disturbance. The simulation is carried out in a Matlab environment with various forms of load and distributed energy resources on an IEEE 37 AC Node converted to DC. The findings show that the conventional load shedding scheme could expose critical loads to substantial and lengthy voltage sags. Voltage sags and over-shedding of load could be resolved using combined load shedding scheme. The adaptive schemes minimise the duration and magnitude of voltage drop by utilizing the rate of change of voltage (ROCOV) to achieve a more reliable assessment of the microgrid operating conditions and determine the appropriate load shedding voltage thresholds and time delays. All the schemes could not achieve an optimal load shedding, this work therefore leads to the need for more advanced load shedding schemes that can shed load optimally for future DC microgrids.