正阻尼直驱风电系统限幅持续饱和引起的振荡分析

Analysis of Oscillation Caused by Continuous Saturation of Limit for Positive Damping PMSG System

新能源风电接入所引起的振荡研究,现较少考虑稳定系统在大扰动后限幅等非线性环节对系统动态的影响。本文基于时域模型,结合降阶系统,分析大扰动后直驱风电机组PMSG(permanent magnet synchronous generator)限幅持续饱和引起的切换型振荡机理。首先给出大扰动后并网PMSG因d轴电流参考值限幅持续饱和引起的切换型振荡现象;其次从数学降阶系统解的存在性角度分析了振荡原因;然后从限幅饱和后直流电压环失效所获得的物理降阶系统的角度,发现物理降阶系统阻尼为负可解释原系统切换型振荡;最后讨论了原系统和物理降阶系统的振荡关联性。结果表明,d轴电流参考值限幅环节持续饱和会显著影响系统的动态行为。

In researches on the oscillation caused by the access of wind power which is one of the new energies,the influence of nonlinear links such as the limit of a stable system after large disturbance on the system dynamics is seldom taken into account.Based on a time-domain model and combined with a reduced-order system,the mechanism of switching oscillation caused by the continuous saturation of limit for a permanent magnet synchronous generator(PMSG)after large disturbance is analyzed in this paper.First,the switching oscillation phenomenon of the grid-connected PMSG caused by the continuous saturation of d-axis current reference limit after large disturbance is given.Second,the reason for oscillation is analyzed from the perspective of the solution existence of the mathematical reduced-order system.Third,from the perspective of a physical reduced-order system obtained from the failure of DC voltage loop after the limit saturation,it is found that the negative damping of the physical reduced-order system can explain the switching oscillation of the original system.Finally,the oscillation correlation between the original system and the physical reduced-order system is discussed.Results show that the continuous saturation of d-axis current reference limit can obviously affect the system’s dynamic behavior.