Improved Fractional-order Damping Method for Voltage-controlled DFIG System Under Weak Grid
Improved Fractional-order Damping Method for Voltage-controlled DFIG System Under Weak Grid
复制标题
弱电网下压控DFIG系统改进分数阶阻尼方法
DOI：
10.35833/mpce.2020.000843
复制
发表时间：
2021-08
影响因子：
6.3
通讯作者：
张兴
中科院分区：
文献类型：
--
作者：
谢震;高翔;杨淑英;张兴
当双馈感应发电机接入弱电网时，其与电网之间的耦合会增加，从而造成稳定性问题。在弱电网中，锁相环(PLL)的跟踪精度和鲁棒性很难保持，电流控制DFIG(CC-DFIG)系统的不稳定风险也会增加。本文采用了一种新型的压控DFIG(VC-DFIG)方式，它是一种电压和频率独立支撑的并网结构，对弱电网具有一定的适应性。建立了VC-DFIG系统的小信号阻抗模型。在弱电网特别是并联补偿电网中，双馈发电机的阻抗不可避免地与电网阻抗产生耦合，产生谐振。在VC-DFIG的基础上，进行了阻抗稳定性分析，研究了控制结构和短路比对系统性能的影响。然后，提出了一种前馈阻尼法来修正VC-DFIG系统在谐振频率下的阻抗。利用所提出的分数阶阻尼法，提高了参数波动情况下共振抑制的鲁棒性和快速性。最后，给出了实验结果，验证了该控制策略的有效性。
When a doubly-fed induction generator (DFIG) is connected to a weak grid, the coupling between it and the grid will increase, which will cause stability problems. It is difficult to maintain the tracking accuracy and robustness of the phase-locked loop (PLL) in the weak grid, and the risk of instability of the current-controlled DFIG (CC-DFIG) system will increase. In this paper, a new type of voltage-controlled DFIG (VC-DFIG) mode, which is a grid-forming structure that can independently support the voltage and frequency and has a certain adaptability in weak grid, is adopted. A small-signal impedance model of the VC-DFIG system is also established. The impedance of DFIG inevitably generates coupling with the grid impedance in the weak grid especially parallel compensation grids, and results in resonance. On the basis of the VC-DFIG, impedance stability analysis is performed to study the influences of the control structure and short circuit ratio. Then, a feedforward damping method is proposed to modify the impedance of the VC-DFIG system at resonance frequencies. The proposed fractional order damping is utilized, which can enhance the robustness and rapidity of resonance suppression under parameter fluctuations. Finally, the experimental results are presented to validate the effectiveness of the proposed control strategy.