Enhancing Dynamic Voltage Stability in Resilient Microgrids Using FACTS Devices

Microgrids (MGs) have emerged throughout the world as the major means of integrating a variety of distributed energy resource (DER) technologies into the distribution system. These DER technologies are mostly coupled through electronic power converters (EPCs). This fact has created new operation challenges as these converter-interfaced DERs could compromise the MG stability, reliability, and resilience margins. On the other hand, induction motor-type loads (IMs) are dynamic loads with the greatest incidence in distribution grids. Air conditioning (A/C) type loads have IMs among their components. IMs demand considerable amounts of reactive power for their correct operation. In particular, when there are disturbances in MGs with high penetration of these types of loads, the phenomenon of fault-induced delay voltage recovery (FIDVR) occurs. This phenomenon causes problems with the dynamic voltage stability (DVS) due to the deficit and inability to supply reactive power of the DERs generator park composing the MG, which could lead to a voltage collapse. To face these new issues, this work proposes an approach to incorporate flexible ac transmission system (FACTS) controllers, such as an SVC and a DSTATCOM, into the grid as reactive power supply resources for improving the microgrid dynamic voltage stability. The proposal includes the design, optimal location, and dynamic modeling of FACTS devices aiming at enhancing MG operation resilience. For validation of the developed methodology, an MG test system reported in the literature and a real microgrid system of the Galapagos Islands in Ecuador have been used. The results demonstrated the superiority of DSTATCOM over SVC in enhancing DVS, FIDVR mitigation, and consequently operational resilience.