Further developments in autonomous converter control in a multi-terminal HVDC system

There has been much discussion over how HVDC grids incorporating many converters should be controlled and several methodologies have been proposed. An underlying principle of a proposed method, Voltage Droop control, was the minimisation of the inter-dependency of the control of the individual converters, inferring little, or no, reliance on a communication system. Since then further work has shown that the philosophy´s fundamental principles were correct and it was applicable to multi-converter systems. Nevertheless, further work has led to refinements that enhance the basic concept to include converters operating with different control modes and system objectives. These developments are described in this paper.