Improvements in the Voltage Stability of a Microgrid due to Smart FACTS – an Approach from Resilience

Abstract

Flexibility along with other characteristics of electrical microgrids (MGs) have allowed, from the point of view of supply, a greater presence of distributed generation (DG) systems through Distributed Energy Resources (DERs). In the context of demand, this permits the connection of different types of static and dynamic loads. However, the increase of dynamic loads can give rise to voltage instability problems; this resulting in a high reactive power compensation requirement. Furthermore, the MG transition from the grid-connected operating mode to the islanding one significantly hinders control actions of DERs. This can lead to a difficult transition and in extreme cases to the MG voltage collapse, which seriously compromise its operational resilience. This paper proposes incorporating smart FACTS (Flexible AC Transmission System) devices, particularly DSTATCOMs (Distribution Static Synchronous Compensators), as an effective solution to substantially improve the MG voltage stability. It aims at dealing with a great amount of dynamic loads especially during the transition to isolated operation of the MG. To this aim, several case studies were considered and analyzed using the CIGRE microgrid test system in the DIgSILENT Power Factory software. The Results obtained showed comparative improvements with the incorporation of smart DSTATCOM devices as regards the margin and behavior of MG voltage stability, as well as improvements in terms of operational resilience.