Experimental validation of autonomous converter control in a HVDC grid

Much research has been done regarding the control and coordination of VSC converters in a Multiterminal HVDC network or grid. Amongst those, one underlying concept is the most common- the DC voltage droop control. In this paper, the control concept has been further developed to use alternative droop characteristics on each converter. This approach allows precise converter current regulation during normal operation while stabilizes DC voltage during power disturbance. Control algorithms of alterative droop characteristics are provided and interactions of different control characteristics are also analyzed. This concept is validated using both digital simulation (PSCAD/EMTDC) and physical modelling of a HVDC grid using a 4-terminal VSC Physical Simulator. Results obtained from the two simulation platforms are compared and show good agreement. The feasibility and advantage of using alternative droop characteristics on each single converter are also validated.