Analytical derivation of poorly-damped eigenvalues in two-terminal VSC-HVDC systems

Under specific conditions, Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) systems can experience stability, or poor-damping related issues. Analytical investigation of the system eigenvalues can demonstrate the impact of physical or control parameters on the system stability. However, especially in case of high-order systems, such expressions are challenging to obtain and so extensive in form that they are impractical to use and cannot provide useful hints on the impact of single parameters on the system's stability. Therefore, current methods in power system analysis rather rely on a purely numerical approach to describe eigenvalues and are deprived of the benefits of the symbolic representation. This paper suggests a method to analytically describe a two-terminal VSC-HVDC link with respect to its dominant eigenvalues, providing a useful tool for the investigation of poorly-damped performance and system stability, by deriving compact analytical eigenvalue expressions.