Robust Fallback Scheme for the Danish Automatic Voltage Control System

This paper proposes a fallback scheme for the Danish automatic voltage control system. It will be activated in case of the local station loses telecommunication to the control center and/or the local station voltage violates the acceptable operational limits. It cuts in/out switchable and tap-able shunts to maintain the voltage locally. The fallback scheme is fully selfregulated according to the predefined triggering logic. In order to keep the robustness and avoid many shunts are being triggered in a short term, the inverse time characteristic is used to trigger switching one by one. This scheme allows for fast triggering when the voltage violation is large, and enlarges the response time when the voltage violation is small. The functioning of the fallback scheme is investigated via time domain simulations, where case studies are carried out in a benchmark model and a model of the western Danish power system.