Communication-free based decoupled DC-voltage and frequency control in the multi-terminal HVDC (MTDC) grids

Abstract

In the Multi-Terminal VSC-HVDC connected to AC (MTDC-AC) systems, upholding the DC-Voltage and Frequency (DCVF) are requisite for its stability and reliability. The PVF double droop control is admired for regulating the DCVF in a communication-free manner. However, during any contingencies, the fixed droop constants and control interaction between the droop controls deteriorate the DCVF response of the MTDC-AC grid with the PVF droop control. In this paper, the Decoupled DC-voltage and Frequency Deviation based Adjustable Droop Control (D2CFD-ADC) method is proposed to overcome these drawbacks. Further, analysis has been carried out to show the effect of control interaction on the DCVF deviations in the system. The proposed method is validated in the MTDC-AC test system and simulated in the PSCAD/EMTDC software.