Frequency response using MTDC grids: A comparative study of common methods

This paper compares different control strategies which facilitate the exchange of frequency response between AC power systems connected by a meshed three-terminal offshore HVDC grid. The paper discusses the influence of such additional control loops on both the HVDC grid direct voltage response as well as on the AC systems frequency stability using instantaneous value average dynamic models. The control strategies tested in this paper are namely: the classical frequency droop based method, the synthetic inertia control loop using the AC system frequency derivative as input and finally an integrated synthetic inertia emulation control scheme utilized as part of the direct voltage control loop. The control goal is the exchange of frequency reserves between the AC systems through the HVDC grid.