双馈风电机组虚拟惯量控制对系统小干扰稳定性的影响

含虚拟惯量控制的双馈风电机组与电力系统的动力学特性存在耦合关系,而锁相环的跟踪能力将直接影响虚拟惯量的控制输入量,因此,考虑虚拟惯量控制的双馈风电机组在锁相环作用下,对系统小干扰稳定性的影响成为亟需解决的问题。首先,计及双馈风电机组的转子电压、锁相环、虚拟惯量控制、转子侧变频器、风电机组机械部分等暂态特性,建立了考虑锁相环与虚拟惯量控制的双馈风电机组并网的互联系统小干扰模型。在此基础上,考虑到锁相环与虚拟惯量控制均会影响同步发电机振荡模态,采用解析的方法从机理上揭示了二者共同作用下系统的小干扰稳定性,即对于含虚拟惯量控制的双馈风电机组,锁相环主要通过影响虚拟惯量对系统的参与程度进而影响系统阻尼:锁相环比例—积分(PI)参数越小,虚拟惯量控制状态变量对区间振荡模态的参与因子越小,机电振荡模态阻尼比越大,这与不含虚拟惯量控制的双馈风电机组中锁相环对系统阻尼特性的影响相反。仿真结果验证了所建模型的合理性与分析结果的正确性。

Impact of Virtual Inertia Control of DFIG Wind Turbines on System Small-signal Stability

Doubly-fed induction generator(DFIG)wind turbines with virtual inertia control considered and the power system are coupled to each other on dynamic characteristic. Since the control input of virtual inertia is affected by the tracking ability of phase-locked loop(PLL), the impact of DFIG wind turbines considering virtual inertia control under the action of PLL on system small-signal stability has become a problem demanding prompt solution. First, by taking into account the transient characteristics of rotor voltage, PLL, virtual inertia control, rotor side converter and mechanical part of DFIG wind turbines, an interconnected power system model of DFIG considering PLL and virtual inertia control is created. Then, as both PLL and virtual inertia control will affect the oscillation modes of synchronous generators, the impacts of PLL and virtual inertia control on power system small-signal stability are explored theoretically by analytic method. The results show that the damping ratio of power system is affected by the participation factor of virtual inertia influenced by PLL. Besides, the smaller the PI parameter of PLL is, the smaller the participation factor of virtual inertia is, and the bigger the damping ratio of electromechanical oscillation will be. This is opposite to the impact of DFIG without considering virtual inertia control under the action of PLL on system stability. The rationality of the interconnected power system model and correctness of analysis results have been verified by simulation. This work is supported by National Natural Science Foundation of China(No. 51277193), National Basic Research Program of China(973 program)(No. 2012CB215206), and Fundamental Research Funds for the Central Universities(No. 2014ZZD02).