Microgrid Dispatch with Protection Constraints

This paper introduces a two-level microgrid dispatch procedure that takes into account microgrid protection settings. The first dispatch level is based on a dynamic economic dispatch algorithm that considers frequency-aware islanding constraints, ensuring the frequency stability of the microgrid during unplanned islanding transitions. The results of the first dispatch level are used as inputs to the load flow calculations performed in the second dispatch level. Based on the load flow calculations, the overcurrent, i.e. overload, and voltage protection settings in the microgrid during the first 15 minutes after a re-dispatch may be set to less conservative values if needed. In this way, the microgrid's operating region is expanded ensuring that tripping of the current or voltage protection relays will not cause a microgrid outage during the first 15 minutes after the dynamic economic dispatch was performed. After this 15-minute period, the voltage and current protection settings will be set to default, i.e. grid-connected or islanded, operating mode values. The case studies presented demonstrate the effectiveness of the proposed microgrid dispatch scheme. Two-level dispatch was compared with the standard economic dispatch and showed increased reliability of power supply.