基于序阻抗的虚拟同步机同步频率谐振现象

Synchronous Frequency Resonance in Virtual Synchronous Generator Based on Sequence-Impedance

针对虚拟同步机(VSG)的同步频率谐振(SFR)现象,鉴于多输入多输出功率耦合模型的不足,通过建立可描述VSG宽频域动态特性的单输入单输出序阻抗模型,提出一种基于序导纳和序阻抗的SFR分析方法,并对单环和多环控制VSG的SFR现象进行对比研究。基于序导纳的极点分布,有效研究SFR与VSG功率环控制参数、虚拟阻抗、内环控制及电网阻抗之间的关系;基于序阻抗的频率特性曲线,对比内环控制引入前后SFR的阻尼特性,从“负阻尼”的角度揭示单环和多环控制VSG的SFR谐振机理;搭建基于RT-Box的实验平台,验证VSG在不同控制方案及不同电网阻抗下的SFR现象,指明VSG控制的优化设计方向。

As for the synchronous frequency resonance(SFR)phenomenon existing in virtual synchronous generator(VSG),considering the shortcomings of multi-input multi-output power coupling SFR analysis models,a sequence-admittance and sequence-impedance based SFR analysis method is proposed by modeling the single-input single-output sequence impedance model that can describe the wide-frequency dynamics of the VSG,and the SFR phenomena of single-loop and multi-loop VSG are comparatively studied.Based on the pole distribution map of sequence admittance,the relationships between SFR and the VSG power control loop parameters,virtual impedance,inner-loop control and grid impedance are effectively studied.Based on the Bode diagrams of sequence-impedance,the damping characteristics of SFR with and without the inner-loop control are compared,and then the resonance mechanism of SFR in single-loop and multi-loop VSG is revealed from the perspective of negative damping.By building the experimental platform based on the RT-Box,the SFR phenomena of VSG under different control schemes and grid impedances are verified,indicating the optimal design direction of VSG control.