Indication of safe transition paths of phase shifter settings by greedy algorithms

In a liberalised market environment, the use of phase shifting transformers (PSTs) or other power flow controlling devices allows the transmission system operator (TSO) to utilise the available grid infrastructure in a more optimal way. In previous work, research has been performed on how to coordinate multiple devices in order to maximise the total transfer capacity. Once the optimal phase shifter settings are determined, the question is how to go from the current setting to this optimal point. In this paper, algorithms are developed to calculate a safe transition between two sets of PST settings. The problem is modelled as a graph in which each combination of PST settings is represented by a vertex (node). Classical shortest path determination algorithms have an unacceptable calculation time for this problem, and an alternative solution must be found. The requirement of the shortest path can be relaxed to a requirement for a good path. This enables the use of a greedy algorithm, which is developed and tested in this paper. Also, an adapted form of the greedy algorithm is proposed, in order to avoid excessive switching between multiple PSTs.