Adaptive Voltage-Based Load Shedding Scheme for the DC Microgrid

Abstract

The direct current (DC) microgrid requires a fast load shedding scheme that prevents instability and voltage collapse when the distributed energy resources are unable to meet the power demand. The load shedding scheme is also expected to prevent unnecessary service interruptions caused by over-shedding of loads. This paper proposes an adaptive voltage-based load shedding scheme utilizing voltage thresholds that are automatically adjusted depending on the rate of change of locally measured bus voltages. The performance of the proposed load shedding scheme is investigated and compared with that of the conventional voltage-based load shedding scheme, using a realistic and detailed study system, under various disturbances. The comprehensive simulation studies that are conducted using the PSCAD software indicate that the adaptive load shedding scheme (i) effectively maintains the DC microgrid power balance through fast and coordinated load shedding, (ii) prevents the DC bus voltages from falling below acceptable levels, (iii) ensures that the critical loads do not experience excessive steady-state voltage deviations, (iv) minimizes the durations and magnitudes of the temporary voltage drop caused by sudden disturbances, and (v) improves power supply reliability.

Keywords

• Direct current microgrid
• integrity protection
• adaptive load shedding
• voltage sag