Description and Comparison of DC Voltage Control Strategies for Offshore MTDC Networks: Steady-State and Fault Analysis

Estimates are that circa 40 GW of offshore wind power capacity is going to be installed throughout Europe by the end of this decade. In this scenario, a pan-European offshore grid network is needed in order to efficiently integrate large amounts of offshore wind into the different European countries’ transmission networks. In this paper, the dynamic model of a multi-terminal HVDC (MTDC) transmission system composed of voltage-source converters is presented. Afterwards, the dynamic models are used to compare four different methods for controlling the DC voltage inside MTDC networks, viz.: droop control, ratio control, priority control and voltage margin method. Lastly, a case study is performed in a four-node MTDC network and the different control strategies are compared during steady-state and an onshore three-phase fnult.