Influence of HVDC P2P Links on Static Voltage Stability in Transmission Grids with High Shares of Renewable Energy

Abstract

The Energiewende with the massive installation of renewable energy sources (RES) in the distribution grid leads to major changes in the transmission system. RES are often installed at sites with a high yield of primary energy, which results in higher average transmission distances. Thus, reactive power demand increases, which affects static voltage stability. To address these challenges, technologies like High Voltage Direct Current (HVDC) Point-to-Point (P2P) links will be used in the transmission grid. Within this paper an iterative load-flow algorithm is proposed to evaluate voltage stability margins, i.e. the distance from the actual operating point to the stability limit regarding active power transmission. Due to the possibility of modern Voltage Source Converters (VSC) to control active and reactive power independently, voltage stability limit is investigated for different loadings of the HVDC P2P links. A 58 bus-transmission grid representing the German transmission system is used, where regional distributed renewable feed-in as well as three HVDC P2P links are applied. The dispatch of conventional power plants is determined through a merit-order approach. Results show that HVDC-links can have a positive effect on voltage stability depending on their power transmission. The choice of the operating point can therefore be crucial for voltage stability.