Reactive control in a deregulated environment with static VAr compensators improving voltage stability

The deregulated market requires great attention to be paid to analysis and control methodologies. This evolution has to satisfy reliability, security and optimisation objectives. In this context the importance of reactive control has to be highlighted. Power electronic devices can be efficiently employed to solve this crucial problem. A co-ordinated control strategy for the reactive power based upon a hierarchical structure is considered. An optimisation procedure is effected at a high level maximising the economic gain and avoiding the possibility of critical conditions deriving from voltage instabilities. The optimisation output data are used as reference signals for static VAr compensators. The rationale behind the static VAr compensator control design is the invariant manifold theory, allowing the reference signal to be tracked with accuracy and robustness. An application is presented with reference to the IEEE 118-bus system which outlines the flexibility and goodness of the proposed technique.