Interaction of droop control structures and its inherent effect on the power transfer limits in multi-terminal VSC-HVDC

Abstract

Abstract-Future multi-terminal HVDC systems are expected to utilize dc voltage droop controllers and several control structures have been proposed in literature. This paper proposes a methodology to analyse the impact of various types of droop control structures using small-signal stability analysis considering all possible combinations of droop gains. The different control structures are evaluated by the active power transfer capability as a function of the droop gains, considering various possible stability margins. This reveals the flexibility and robustness against active power flow variations, due to disturbances for all the implementations. A case study analyzing a three terminal HVDC VSC-based grid with eight different kinds of droop control schemes points out that three control structures outperform the remaining ones. Additionally, a multi-vendor case is considered where the most beneficial combinations of control structures has been combined in order to find the best performing combination.

Small‐signal stability analysis and optimal control parameters design of MMC‐based MTDC transmission systems

“…In recent years, several MMC‐HVDC projects (e.g. Trans Bay Cable project, Zhejiang Zhoushan five‐terminal MMC‐HVDC project, Zhangbei four‐terminal MMC‐HVDC project, and North Sea link project) have been in operation or under construction, and MMC‐based MTDC has become an important trend for the future development of smart grids and the global energy interconnection [5–9].…”