Stability Analysis of a Virtual Synchronous Machine-based HVDC Link by Gear’s Method

Declining equivalent inertia caused by the massive integration of converter-based technologies can increase the risk of stability problems in the future power system. Control of HVDC systems as Virtual Synchronous Machines (VSMs) for providing emulated inertia is a promising countermeasure against this development. However, low inertia converter dominated power systems are raising new challenges for stability analysis. Thus, new numerical techniques and tools are needed for efficient and accurate analysis of small-and large-signal stability issues in complex power systems with different kinds of generation units, converter systems and control loops that can experience potential interactions, internally or with the network. Gear's method with a variable time step, offers the possibility to obtain fast and flexible procedures for large-signal stability analysis. Additionally, it can make stability analysis efficient by combining the small-signal and large-signal analysis into the same process. This paper will show how the stability of a power system with a VSM-based HVDC link can be evaluated by the method and presents an approach for simultaneous small-and large-signal stability assessment.