Headroom-based Frequency and DC Voltage Control for Large Disturbances in Multi-Terminal HVDC (MTDC) Grids

In the AC-integrated MTDC (AC-MTDC) grids, regulating the DC voltage and frequency became indispensable for reliable and stable operation. For effective DC voltage and frequency regulation, Headroom-based Adaptive Droop Control (HR-ADC) has been proposed in this paper. The HR-ADC changes droop value adaptively based on the available headroom at Grid Side Voltage Source Converters (GSCs), Wind and solar form connected Voltage Source Converter stations, say Renewable Energy Side Voltage Source Converters (RECs). In the case of RECs, available power at the Wind or Solar Farms is also considered while operating in the proposed HR-ADC. This approach is autonomous and robust, ensuring the system operates stably and reliably even during significant disturbances in the AC-MTDC grids. A lower-order dynamic model-based eigenvalue and post-contingencies analysis of the AC-MTDC grid has been carried out to show the virtue of the proposed HR-ADC methodology. Further, to show the significance of the proposed method, it is compared with a conventional Fixed Droop Control (FDC) by considering the five terminal CIGRE Bi-polar DC grid benchmark model integrated into two area power systems. A PSCAD/EMTDC software is used to simulate this test system.