Multi terminal VSC-HVDC systems are a promising solution to the problem of connecting offshore wind farms to AC grids.Optimal power sharing and appropriate control of DC-link voltages are essential and must be maintai...Multi terminal VSC-HVDC systems are a promising solution to the problem of connecting offshore wind farms to AC grids.Optimal power sharing and appropriate control of DC-link voltages are essential and must be maintained dur-ing the operation of VSC-MTDC systems,particularly in post-contingency conditions.The traditional droop control methods cannot satisfy these requirements,and accordingly,this paper proposes a novel centralized control strategy based on a look-up table to ensure optimal power sharing and minimum DC voltage deviation immediately during post-contingency conditions by considering converter limits.It also reduces destructive effects(e.g.,frequency devia-tion)on onshore AC grids and guarantees the stable operation of the entire MTDC system.The proposed look-up table is an array of data that relates operating conditions to optimal droop coefficients and is determined according to N-1 contingency analysis and a linearized system model.Stability constraints and contingencies such as wind power changes,converter outage,and DC line disconnection are considered in its formation procedure.Simulations performed on a 4-terminal VSC-MTDC system in the MATLAB-Simulink environment validate the effectiveness and superiority of the proposed control strategy.展开更多
文摘Multi terminal VSC-HVDC systems are a promising solution to the problem of connecting offshore wind farms to AC grids.Optimal power sharing and appropriate control of DC-link voltages are essential and must be maintained dur-ing the operation of VSC-MTDC systems,particularly in post-contingency conditions.The traditional droop control methods cannot satisfy these requirements,and accordingly,this paper proposes a novel centralized control strategy based on a look-up table to ensure optimal power sharing and minimum DC voltage deviation immediately during post-contingency conditions by considering converter limits.It also reduces destructive effects(e.g.,frequency devia-tion)on onshore AC grids and guarantees the stable operation of the entire MTDC system.The proposed look-up table is an array of data that relates operating conditions to optimal droop coefficients and is determined according to N-1 contingency analysis and a linearized system model.Stability constraints and contingencies such as wind power changes,converter outage,and DC line disconnection are considered in its formation procedure.Simulations performed on a 4-terminal VSC-MTDC system in the MATLAB-Simulink environment validate the effectiveness and superiority of the proposed control strategy.
