Distributed ancillary service support for independent AC-areas through HVDC grid
This work aims to study different ancillary services such as frequency support, rotor angle stability and voltage stability that can be provided to independent AC areas through Multi-Terminal HVDC grid. An agent-based control scheme has been suggested to support the frequency of the imbalanced AC area using other intact areas during a disturbance. The frequency support is carried out through some agents/controller, where the objective of the agents is to reach a common value for a given state, i.e. frequency, using the local and neighbouring information. In this scheme, the concept of Adaptive Graph (AG) has been introduced to the consensus problem to deal with the limitation of original scheme in considering the rated capacity of HVDC converters. In this case, the frequency consensus can be reached to a new stable value by removing one or several converters from the communication graph when reaching rated active power capacity. In order to test the proposed scheme, a model of 7-terminal dc-grid and corresponding AC areas is developed in real time simulator OPAL-RT. The results show that the adaptive graph scheme improves the reliability of the system during distributed frequency support.