关键词: 海上风电场, 模块化多电平换流器, 状态空间模型, 系统链路延时, 模态辨识, 粒子群算法

Abstract: The double closed-loop control structure of flexible DC converter station is easy to cause link delay and lead to system instability. Based on the small-signal stability analysis, a stability improvement strategy based on the optimization of particle swarm optimization（PSO） algorithm controller parameters is proposed. At first, the detailed state-space model of 68 order system in d-q synchronous reference frame is established, which is validated by the time domain simulation. Secondly, the influence of link delay on system stability is analyzed based on eigenvalue analysis, the characteristic of system stability affected by the link delay of the double closed-loop controller parameter at the wind farm side modular multilevel converter（WFMMC） is obtained, and the participation factor analysis is adopted to filter out the controller parameters related to the stability of the system. Finally, taking the damping ratio and the distance from the characteristic root to the imaginary axis as the optimization goals, a stability improvement strategy based on the improved PSO algorithm is proposed. The results indicate that the stability model and the stability improvement method is effective, and in the case of a long link delay, the stability improvement effect is more significant.

Key words: offshore wind farm, modular multilevel converter, state-space model, system link delay, mode identification, particle swarm optimization