Secondary Control of a Multi-Terminal HVDC Grid Using a Consensus-Based Distributed Scheme

Abstract

Variants of droop control for power-sharing in a multi-terminal high voltage dc (MTDC) grid result in voltage deviation from the nominal value. Moreover, the power-sharing is inaccurate in the droop-controlled MTDC system. This paper proposes a secondary control scheme with a distributed architecture to compensate the voltage deviation and share the power mismatch automatically. Furthermore, a distributed observer is used to estimate the average voltage of the MTDC grid stations. The proposed distributed controller and observer use the local measurements and communications with neighboring stations, in which a limited information of output powers and voltages are shared. Therefore, the requirement of the global information in the centralized secondary control schemes is eliminated, which improves the reliability and stability of the MTDC system. The case studies illustrate that the proposed distributed scheme regulates the stations' average voltage and shares the power mismatch automatically.