直驱风电场经交流并网系统dq阻抗模型及稳定性分析

为研究直驱式风电场经交流并网系统中，由变流器控制器与电网互相作用而引发新的次同步振荡问题，综合考虑变流器内部控制动态特性、交流动态响应和功率传输特性，推导了直驱风电机组经交流并网系统dq等效阻抗模型。结合系统阻抗行列式稳定判据，分析了直驱风电机组网侧变流器内部控制参数变化对次同步振荡的影响。研究表明，随着网侧变流器中内、外环的PI控制参数（Kp、Ki）的减小，发生振荡失稳的风险增加，系统稳定性下降。最后，通过PSCAD/EMTDC环境下时域仿真验证了模型与理论分析的正确性。

Dq impedance model and stability analysis of Direct-drive wind farm via AC grid-connected system

In order to study the new subsynchronous oscillation problem caused by the interaction between the controller and the grid in the direct drive wind farm through the AC grid-connected system, comprehensively considering the internal control dynamic characteristics, AC dynamic response and power transmission characteristics of the converter, the dq equivalent impedance model of the direct-drive wind turbine through the AC grid-connected system is deduced. Combined with the stability criterion of the system impedance, the influence of the change of the internal control parameters of the grid-side converter of the direct-drive wind turbine on the subsynchronous oscillation is analyzed. Research shows that as the PI control parameters (Kp, Ki) of the inner and outer loops of the grid-side converter decrease, the risk of oscillation instability increases and the system stability decreases. Finally, the correctness of the model and theoretical analysis is verified by time-domain simulation under PSCAD/EMTDC environment.