考虑控制链路延时的风电场经MMC-HVDC并网系统稳定性分析及提升策略

柔直换流站的双闭环控制结构易引发链路延时导致系统失稳,基于小信号稳定性分析,提出基于改进粒子群（PSO）算法控制器参数优化的稳定性提升策略。首先,建立考虑链路延时的d-q旋转坐标系下68阶详细状态空间模型,并利用时域仿真模型进行验证。其次,基于特征根分析控制链路延时对系统稳定性的影响,获取风电场侧换流站双闭环控制器链路延时作用影响系统稳定性的特性,通过参与因子法筛选出影响系统稳定性的控制器参数。最后,以阻尼比和特征根到虚轴的距离为优化目标,提出基于改进PSO算法的稳定性提升策略。结果表明所建立考虑控制链路延时稳定性分析模型和稳定性提升策略的有效性,且在系统控制链路延时较长情况下,稳定性提升效果较为显著。

STABILITY ANALYSIS AND IMPROVEMENT METHOD OF WIND FARM GRID-CONNECTED SYSTEM VIA MMC-HVDC CONSIDERING LINK DELAY

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.