直驱风电场经LCC-HVDC外送系统阻抗建模及振荡机理分析

Impedance Modeling and Oscillation Mechanism Analysis of D-PMSG-based Wind Farms Integration Through LCC-HVDC System

由于大规模远距离输送的客观需要,直驱风电场经电网换向换流器高压直流(line-commutedconverterhigh voltage direct current,LCC-HVDC)送出已经成为一种常见方式。然而,风电机组与LCC-HVDC的交互作用尚未明确,可能引发的振荡问题会危害电网的稳定安全运行。文中首先采用双傅里叶变换得到交/直流映射函数的频域表达,建立直驱风电场经LCC-HVDC送出系统阻抗模型。然后,基于送出系统在各频段内的主导因素分析,开展送出系统阻抗特性分析,研究对次同步频段和超同步频段内阻抗特性影响较大的因素。最后,结合仿真案例分别揭示直驱风电场经LCC-HVDC送出系统在次同步和超同步存在的振荡风险,并阐述振荡机理。

The energy sources and main consumption are unevenly distributed in China,causing the pressing need for large-scale long-distance transmission of wind power.The direct-drive permanent magnet synchronous generator(D-PMSG)based wind farm integration through line-commuted converter high voltage direct current(LCC-HVDC)system has become a common way to deliver the wind power.However,the interaction between the wind turbines connected to grid through the power electronics devices and LCC-HVDC has not been thoroughly investigated,and the potential oscillations may seriously affect the safe operation of the power grid.In this paper,the frequency-domain expression of AC/DC mapping function was obtained by using double Fourier transform,and the impedance model of the D-PMSG-based wind farms integrated through LCC-HVDC system was established.Based on the analysis of the dominant factors in each frequency range,the impedance characteristics were discussed,and the factors that have significant influence on the impedance characteristics in sub-synchronous and super-synchronous frequency band were studied in depth.Finally,the oscillation risks of the system in sub-synchronous and super-synchronous frequency bands were revealed and verified by time-domain simulation,and the oscillation mechanism was presented.