Sizing and siting static synchronous compensator devices in the Portuguese transmission system for improving system security

This study presents a methodology for siting and sizing static synchronous compensator (STATCOM) devices in the Portuguese transmission system in order to improve system security following severe grid faults. Security issues arise since the Portuguese transmission system incorporates significant levels of wind generation without fault ride through and reactive current injection capabilities during grid faults. As the transmission system operator (TSO) is responsible for assuring system security, the goal of the study is to take advantage of the proved STATCOM ability for injecting reactive current in order to mitigate the disconnection of large amounts of wind farms in case of severe grid faults. The proposed methodology was developed and tested in coordination with the Portuguese TSO and it is based on the formulation of an optimisation problem in order to minimise the installed STATCOM power while ensuring its compliance with the current grid code requirements, namely in what concerns to the system stability and security. Given the discrete and complex nature of the problem, a hybrid approach, combining both a heuristic method and an evolutionary particle swarm optimisation (EPSO) algorithm was developed. Results show the effectiveness of the proposed methodology as well as its robustness regarding the validity of the obtained solutions while facing the most severe operational scenarios.