Enhanced critical clearing time estimation and fault recovery strategy for an inverter-based microgrid with IM load

摘要

This paper analyzes an inverter-based microgrid with an induction motor (IM) load and proposes an enhanced method to calculate its critical clearing time (CCT) and a fault recovery strategy to increase its resiliency. The CCT calculation is improved by accounting for the transient electrical phase that deacelerates the IM immediatly after the fault. Results show that our method is able to accurately calculate this effect without adding much computational complexity and corrects the overestimation error obtained with previous methods. The fault recovery strategy increases the resiliency of the microgrid by avoiding IM stalling after a fault. It is achieved by commanding a reduction in the inverter source output frequency that increases the electrical torque available at low speeds leading to a larger CCT and expedited recovery. The accuracy and functionality of both the CCT estimation and the fault recovery strategy are validated with a microgrid experimental set-up.