The Benefits of Energy Storage Combined with Hvdc Transmission Power Modulation for Mitigating Inter-area Oscillations

The modern power grid is a complex and dynamic system that relies on both distributed and centralized controls. When large generation and load complexes are separated by long transmission lines, the propensity for inter-area oscillations increases. These oscillations have been identified as a hazard for utility systems since they may cause damage to equipment or restrictions on power flows over select transmission lines. In previous work, active damping methods have been investigated that include power modulation between areas using energy storage or high voltage DC transmission (HVDC). More recently, the latter approach has been pursued in the western interconnection due to the availability of existing infrastructure, specifically the Pacific DC Intertie (PDCI). Unfortunately, the HVDC damping scheme only allows the modulation of power between two buses, providing limited controllability over certain oscillatory modes, such as those oriented more or less perpendicular to the PDCI. In this paper, the benefits of adding additional energy storage to improve controllability are highlighted through analysis and simulation, including an official base case for the western North American Power System (wNAPS).