双馈风电场抑制电网低频振荡的自适应附加控制策略

An Adaptive Additional Control Strategy for Suppressing Low-Frequency Grid Oscillations in Doubly-Fed Wind Farms

针对大型风电场跨区输送电能时引起的弱或负阻尼低频振荡问题,提出一种基于李雅普诺夫稳定性理论的快速终端滑模附加阻尼控制策略.研究双馈风力发电机(DFIG)灵活的功率调控特性和快速响应阻尼调节能力,根据DFIG转子外加电压与磁链之间的关系和滑模变结构控制方法设计转子磁链控制器.在系统发生低频振荡时,期望磁链值与实际磁链值产生偏差,附加阻尼控制器输出一个自适应控制信号到转子侧功率控制环节,提高风电场有功出力,抑制系统的低频振荡.在MATLAB/Simulink中建立风电并网系统仿真模型进行离线仿真实验,并搭建基于实时数字仿真系统的大型风电场跨区输电模型进行实时仿真验证.离线仿真和实时仿真结果均表明:当系统发生低频振荡时,应用所提控制方法能够快速调节DFIG发出有功功率,增强系统的阻尼水平,有效抑制系统低频振荡抑制.

Aiming at the problem of weakly or negatively damped low-frequency oscillations caused by cross-zone transmission of electricity from large wind farms,this paper proposes a fast terminal sliding-mode additional damping controller based on the Lyapunov stability theory.By investigating the flexible power regulation characteristics and the capability of dynamic frequency response to damping regulation of doubly-fed wind turbines(DFIG),a rotor magnetic chain controller is designed according to the relationship between the applied voltage and magnetic chain of DFIG rotor and the sliding mode variable structure control method.When low-frequency oscillations occur in the system,the desired magnetic chain value will deviate from the actual magnetic chain value.The additional damping controller outputs an adaptive control signal for the rotor-side power control link to increase the active output of the wind farm and suppress low-frequency oscillations in the system.A simulation model of the wind power grid-connected system is established in MATLAB/Simulink for off-line simulations,and a real-time simulation experiment of a large wind farm cross-zone transmission model based on real time digital simulation system is conducted.The results of both off-line and real-time simulations show that when low-frequency oscillations occur in the system,the proposed control method can quickly regulate the active power emitted by the DFIG and enhance the damping level of the system,which is effective in suppressing low-frequency oscillations in the system.