System operational dispatching and scheduling strategy for hybrid cascaded multi-terminal HVDC.

• Free variables are selected based on mathematical model of hybrid cascaded MTDC. • System security operating range is analyzed to determine the free variables values. • An operation point calculation method for the hybrid cascaded MTDC is proposed. • The hybrid MTDC system operational dispatching and scheduling strategy is proposed. A hybrid cascaded Multi-terminal HVDC (MTDC) system involving both series and parallel-connected converters, which combines the advantages of line commutated converter based (LCC) and voltage source converter based (VSC) HVDC for ultra-high voltage, large-capacity and flexible power transmission, is proposed and is to be implemented in a real project in China. Due to complexity of operational control and difficulty of operational scheduling brought by the hybrid cascaded MTDC system and the lack of prior related research works, this paper establishes the mathematical model of the hybrid cascaded MTDC system and then proposes a system operational dispatching and scheduling strategy, which includes: 1) feasible coordinated operational control strategies investigation; 2) security operating range of the whole hybrid cascaded MTDC system analysis; 3) operating points of the hybrid cascaded MTDC system calculation. Simulations results based on PSCAD/EMTDC are used to validate the proposed system operational dispatching and scheduling strategy. [ABSTRACT FROM AUTHOR]