Fault ride through strategy of VSC-MTDC system connected with offshore wind farms

摘要

Along with the scale of offshore wind power plants expanding, we need to develop more mature fault-ride through strategies to ensure the safe operation of the power system. This paper proposes a coordinate control strategy (CCS) for secure fault-ride through of doubly fed induction generator (DFIG)-based offshore wind farms. The offshore wind farms are connected to the onshore grid through a voltage source converter based multi-terminal high voltage DC transmission (MTDC). The coordinate control strategy works in the way that on the terrestrial fault occurrence, the power set point of wind turbines will be adjusted according to μ, which can prevent the DC voltage from exceeding its limit value. The power reduction factor μ is calculated based on the deviation of DC voltage. In addition, the receiving end converters will adjust the proportion of reactive power and active power injected into the ac grid based on the deviation of voltage magnitude of ac-and dc-terminal, which improves stability of ac grid. Nonlinear simulation are presented by DIgSILENT/PowerFactory to verify the functioning of this coordinate control strategy.