Smart robust voltage control for distribution networks using interval arithmetic and state machine concepts

Due to the connection of a great number of distributed generation (DG) plants, a critical voltage regulation problem in medium voltage distribution networks arises. After a synthetic survey of different strategies reported in literature to solve this problem, a voltage control concept for smart distribution networks with high penetration of distributed generation is presented. It makes use of all the possible means of intervention usually available in a distribution network and asks for an additional communication infrastructure due to its centralized structure. The proposed concept is a compromise between nearly global optimal operation and ease of implementation. Control actions are hierarchically organized by means of a state machine which constitutes the core of the decision logic of the controller. The voltage controller decisions regarding reactive and active power control of the controllable distributed plants are based on a linearised model of the distribution network. The model is valid in a broad range of operation. Uncertainties are accounted by interval arithmetic methods. Efficient operation is guaranteed by constrained optimization. The control concept has been extensively validated by simulation runs with load and generation profiles from real life operation in a distribution network located in Vorarlberg, Austria. Results are very promising so that the real implementation as a prototype will be carried out in two distribution networks in two different regions of Austria in the near future.