Power Flow Control to Optimise a Distribution System's Operation

Abstract

The growing integration of renewable energies (RE) into the power System causes congestions to occur more requently. To reduce congestions in the short term and to make the utilisation of the power system more e!cient in the long term, power flow control (PFC) is already proposed in the transmission system. However, exemplary studies show that congestions in the distribution system will increase if the transmission system is expanded. For this reason, the potential of PFC to reduce congestions in the model of a real distribution system is investigated in this work. Several Unified Power Flow Controller (UPFC) devices are optimised in terms of number, placement in the power system, size, control Parameters and costs. Two optimisation approaches are developed, with one reducing the number of degrees of freedom by integrating system knowledge. With respect to a critical grid state with many congestions and with costs of the UPFCs being neglected, PFC can reduce congestions significantly (99.13 %). When costs are taken into account, an implementation of UPFCs is found to reduce 73.2 % of RE curtailment. A Basic Analysis of the costs suggests that the installation of UPFCs is profitable. The results demonstrate that PFC should be considered in the future to integrate more RE into the power system and to increase its efficient use. Furthermore, it is found that the integration of System Knowledge leads to better results faster and that, contrary to expectations, the optimisation problem faced is simple to solve. The developed Methods not only allow to determine an optimal use of UPFCs in a Distribution system that minimises congestions, but also to estimate their profitability. Thanks to the modular structure, the optimisation can be changed and supplemented and thus provides a basis for further simulations.