Case-Study of an HTS Saturable Core Reactor for Power Flow Control in a Transmission Grid

Power flow control in transmission grids is a major challenge for system operators. The flow depends on the reactance of the lines, and, in meshed grids, the capacity of a line may not be fully used when another branch is already overloaded. Alternatively, often current ratings of lines could be dynamically increased under favorable meteorological conditions. Congestions in the grid arise and its mitigation often implies curtailing renewable generation or splitting markets. Being able to route power in the grid adequately is a solution to prevent these situations and their corresponding economic losses. For such, the reactance of the lines needs to be adjusted, which can be done, e.g., by adding variable capacitors that are series- or shunt-connected to them. A Superconducting Saturable Core Reactor (SSCR) is used in this work, as an alternative to the latter approach, demonstrating how it can provide an effective power flow control through the modulation of line reactance, thus supporting grid operation. The SSCR is connected in series with one of the lines in a meshed grid, and the inductance of the device is modulated by varying its core permeability through a dc current flowing on a high-temperature superconducting (HTS) lossless coil. A selected use case is simulated in the PSS/E packages, to assess the performance of the device. The characteristic of a laboratory-scale HTS-SCR is measured and modeled, and steady-state experiments are presented.