Frequency regulation and congestion management by Virtual Storage Plants

The potential role of energy storage as flexible resource to help meet the challenging energy and environmental targets is well recognized. It can provide both steady-state and dynamic support to the power networks. A Virtual Storage Plant (VSP) is an aggregation of heterogeneous energy storage units that act as a single storage device to provide system-level support. This paper introduces an innovative and scalable hierarchical control framework for the optimal coordination of a large number of distributed storage devices through VSPs to provide frequency regulation and congestion management in multi-area power networks. The proposed approach combines distributed optimization and consensus-based control. At a lower level, aconsensusbased control is designed to track power setpoints and to maintain a balanced state-of-charge among storage units. This facilitates the modeling of VSPs at higher level, where a distributed optimization approach is applied to achieve crossregional coordination of multiple VSPs to deliver frequency support to interconnected power systems, while avoiding congested power flows over the tie lines. The proposed control framework is assessed on a realistic case study implemented by using MATLAB and the high-fidelity power system simulator DigSILENT. The IEEE 39 Bus system and a real regional power network in South-East Europe are considered in the case study. The simulation results demonstrate the promising performance of the proposed approach and the effectiveness of VSP in promoting large-scale storage integration.