Abstract
This paper proposes a practical and reliable decentralized load shedding strategy to protect the integrity of the direct-current (DC) microgrid. The proposed strategy utilizes time delays that automatically adapt to the DC microgrid operating conditions through continuous evaluation of the bus voltage variations, without depending on remote communication. It is evaluated in comparison with the conventional timer-based load shedding strategy. The studies are performed in the PSCAD software environment, on a detailed model of a DC microgrid that contains various types of loads and distributed energy resources. The results of the investigations show that the proposed adaptive time delay strategy (i) effectively restores the balance between the power demand and supply in the DC microgrid by quickly shedding the necessary amount of loads, (ii) is able to prioritize the non-critical loads by coordinating the load shedding steps based on a pre-determined order, (iii) prevents the steady-state values of the DC microgrid voltages from falling below a predetermined lower limit, (iv) significantly limits the voltage sags caused by power deficit in the microgrid, (v) is highly expandable and is able to coordinate a large number of load shedding steps, and (vi) improves the reliability of the electrical power provided to the DC microgrid loads, by avoiding inessential load shedding.
Highlights
Microgrids facilitate the integration of distributed energy resources (DERs) in power distribution networks and provide the consumers with reliable and high-quality electrical energy [1]–[3]
The conventional control actions, e.g., adjusting the DER power outputs, may not be adequate to prevent sustained under-voltage conditions and cascading outages caused by a significant power deficit, especially in an islanded DC microgrid
The results indicate that the conventional strategy with short delays does not provide sufficient time for the bus voltages to reach the acceptable levels, before shedding the group of loads
Summary
Microgrids facilitate the integration of distributed energy resources (DERs) in power distribution networks and provide the consumers with reliable and high-quality electrical energy [1]–[3]. The timer-based strategy coordinates the load shedding steps using different time delays and a common voltage threshold.
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