弱电网下基于虚拟母线电压控制的双馈风机稳定性优化研究

为了提高弱电网下双馈风机并网的稳定性，研究了弱电网下基于虚拟母线电压控制的双馈风机稳定性优化问题。首先建立了双馈风机系统接入弱电网的小信号模型，基于特征值分析法，发现电网强度较弱或风机输出功率较高时，会导致系统稳定性变差甚至振荡失稳。然后提出了一种弱电网下提高双馈风机稳定性的虚拟母线电压控制方法，相当于改变了锁相环跟踪并网点的位置，降低了电网阻抗，等效为提升了风机并网点的电网强度。接着分析了虚拟母线电压控制对系统稳定性的影响效果并分析了补偿因数和时间常数的设计范围，研究发现系统稳定性随着补偿因数的增加而增强，随着时间常数的增加而变弱。在Matlab/Simulink中搭建了双馈风机接入弱电网的时域模型并在半实物平台中进行实证，验证了该优化控制方法的正确性和有效性。

Stability Optimization of DFIG Based on Virtual Bus Voltage Control in Weak Grid

In order to improve the stability of doubly fed induction generator （DFIG） connected to weak grid， this paper conducts the studies of the stability optimization of the DFIG based on virtual bus voltage control in weak grid. Firstly， the small signal model of the DFIG system connected to the weak grid is established. Using the eigenvalue analysis method， it is found that the system stability will become worse or even oscillatory instability will occur when power grid is weak or the output power of the DFIG is high. Then a virtual bus voltage optimization control method is proposed to improve the stability of the DFIG in the weak grid，changing the position of the phase-locked loop tracking the grid-connected point， reducing the grid impedance，which is equivalent to improving the power grid strength of the grid-connected point. Furthermore，the effect of the virtual bus voltage control on the system stability and the design range of compensation factor and time constant is analyzed. The results of this study indicate that the system stability increases with the increase of the compensation factor and weakens with the increase of the time constant. The time domain model of the DFIG connected to the weak grid is built in Matlab/Simulink and the demonstration is carried out on a semi-physical simulation platform， verifying the correctness and effectiveness of the optimization control method.