计及频率耦合的跟网-构网混联系统交互阻抗建模及稳定性分析

Interaction Impedance Modeling and Stability Analysis of Hybrid Grid-Following and Grid-Forming Interconnected Systems with Frequency Coupling Considered

中文关键词:混联系统  频率耦合  交互阻抗模型  小干扰稳定性

keywords:hybrid interconnected systems  frequency coupling  interaction impedance model  small-signal stability

中文摘要:针对新能源混联系统（由跟网型与构网型变流器构成）阻抗建模中忽略频率耦合效应，导致稳定性分析结果出现偏差的问题，提出一种基于复变量的交互阻抗建模方法。该方法通过引入交互项量化系统耦合效应，构建了含频率耦合的等效单输入单输出阻抗模型。基于此模型，分析了系统的小干扰稳定性，并讨论了关键控制参数对阻抗特性的影响规律。仿真结果表明：所建立的阻抗模型精度较高，能准确判断小干扰稳定性；跟网型锁相环带宽变化主要影响中频段阻抗，构网型功率环的虚拟惯量和阻尼则显著影响次/超同步频段，其中增大惯量（或减小阻尼）容易诱发稳定性问题。

Abstract:Traditional impedance modeling of hybrid grid-following （GFL） and grid-forming （GFM） converter systems generally neglects frequency coupling effects，resulting in inaccurate system interaction characterization and deviations in small-signal stability analysis. To solve this problem，this paper proposes an interaction impedance modeling method based on complex variables. By introducing interaction terms to quantify system coupling effects，an equivalent single-input single-output （SISO） impedance model incorporating full frequency coupling characteristics is constructed. On the basis of the established model，the small-signal stability of the hybrid system is analyzed，and the influence mechanisms of key control parameters on system impedance characteristics are comprehensively discussed. Simulation results show that the proposed model has high modeling accuracy and can effectively evaluate system small-signal stability. The phase-locked loop bandwidth of grid-following converters mainly affects the medium-frequency impedance characteristics，while the virtual inertia and damping of the power loop of grid-forming converters dominate the sub-synchronous and super-synchronous frequency bands. Increases in virtual inertia or decreases in virtual damping will deteriorate system stability and induce oscillation risks.