基于构网型SVG控制优化的双馈风场高频谐振抑制分析

Analysis of High-Frequency Resonance Suppression in Doubly-Fed Wind Farms Based on Grid-Forming SVG Control Optimization

含跟网型(grid-following,GFL)静止无功发生器(static var generator,SVG)的双馈风场内集电电缆投入后可能出现高频振荡问题。针对这一问题,利用谐波线性化方法分别建立双馈风机(doubly-fed induction generator,DFIG)、构网型(grid-forming,GFM)SVG和跟网型SVG的序阻抗模型。基于所建风场联合序阻抗模型进行阻抗分析发现,由于跟网型SVG在高频段呈现容性特征,投入集电电缆后风场系统高频段阻抗呈现负阻尼特性,导致高频谐振发生风险增高。与无电流内环的构网型SVG相比,含电流内环的构网型SVG不但动态响应速度快,而且具有虚拟阻抗限流等功能,因此提出一种基于构网型双环SVG虚拟阻抗优化的风电场高频谐振抑制措施,通过虚拟阻抗优化实现对系统整体阻抗的重塑,进而抑制高频谐振的发生。最后,通过仿真验证了理论分析和所提高频谐振抑制方法的正确性。

High-frequency resonance occurs after a no-load line is operated in a doubly fed wind farm with a gridfollowing(GFL)static var generator(SVG).To solve this problem,the harmonic linearization method was used to establish the sequence impedance models of a doubly fed induction generator(DFIG),grid-forming(GFM)SVG,and grid-following SVG.Based on the established joint sequence impedance model of the wind farm,impedance analysis shows that the capacitive characteristics of the grid-following SVG in the high-frequency band result in the high-frequency impedance of the wind farm system exhibiting negative damping characteristics after the no-load line is put into operation.This situation increases the risk of high-frequency resonance.In comparison to the grid-forming SVG without the current inner loop,the GFM SVG with the current inner loop not only demonstrates a fast dynamic response speed but also provides the function of virtual impedance current limiting.Therefore,a high-frequency resonance suppression method for wind farms based on virtual impedance optimization of a GFM double-loop SVG is proposed.By optimizing virtual impedance,the overall impedance of the system was reshaped,thereby inhibiting the occurrence of high-frequency resonances.Finally,the correctness of the theoretical analysis and the proposed high-frequency resonance suppression method was verified through simulation.