A two-stage power dispatching algorithm for system support by droop-controlled DC grids

This paper presents a two-stage algorithm to regulate the power flow among a Multi-Terminal DC (MTDC) grid with DC voltage droop controllers to provide system support for the surrounding AC systems. At stage one, DC voltage of each terminal is calculated with the proposed analytical model to track the power demand of AC systems determined by the system operator. At stage two, power initial set points or DC droops of the droop controllers are modified according to the calculated DC voltage in the first stage. The proposed algorithm can accurately and quickly track the power demand from AC systems to provide system support under the system frequency disturbances. A four-terminal MTDC grid was modeled in the DIgSILENT/PowerFactory to demonstrate the effectiveness of the proposed algorithm.