虚拟同步发电机特性的三相逆变器小信号建模及分析

Small-signal Modeling and Analysis of Three-phase Characteristics of Virtual Synchronous Generator

现有的虚拟同步发电机特性的三相逆变器小信号稳定性分析中,对于线路和负载通常采用稳态方程,且忽略了电压电流内环控制器的动态特性,导致分析结果产生一定误差。为了更准确地分析其动态特性,首先建立了虚拟同步发电机特性的三相逆变系统的小信号模型;与Matlab/Simulink中实际虚拟同步发电机三相逆变系统的仿真模型对比分析了负载扰动下的过渡过程,验证了所建小信号模型的准确性。然后通过计算参与因子表,分析了状态变量和特征根的关联程度。进而研究了负载参数、线路参数、虚拟机参数以及调节器PI参数对系统特征根的影响规律,并对距虚轴较近的一对共轭特征根进行特征根灵敏度分析,揭示了负载、线路、虚拟机以及调节器等参数对该特征根对应模态的贡献度。最后,通过Matlab/Simulink模型和小信号模型在多组参数下的扰动测试,结果表明特征根对应的响应特性与两种模型仿真的过渡过程吻合,验证了各参数对系统主特征根的影响规律。该小信号模型可以作为虚拟同步发电机特性的三相逆变器动态特性分析的有效工具。

Currently,among stability analysis of small-signal three-phase inverter with characteristics of virtual synchronous generator,the steady-state equation is adopted to calculate the relevant information of lines and load,and dynamic characteristics of voltage-current inner loop controller are ignored,resulting errors of such analysis results. In order to analyze dynamic characteristics more accurately,firstly,this paper set up a small-signal model of three-phase inverter with characteristics of virtual synchronous generator,and then made a comparison with simulation model of threephase inverter system of practical virtual synchronous generator in Matlab / Simulink,analyzing the transient process of load disturbance and verifying the accuracy of the setup small-signal model. Then,by calculating participation factors,the paper analyzed correlation degree of state variables and eigenvalues and made research on influence laws of such parameters as load,line,virtual generator and modulator PI on eigenvalues of the system. In addition,as for the pair of conjugate eigenvalue which is close to the virtual axis,the authors made sensitivity analysis and thus revealed the contributions made by parameters like load,line,virtual generators and modulator to modal state of relative eigenvalues.Finally,disturbance tests with Matlab / Simulink model and the small-signal model with various sets of parameters were carried out,which proved that response characteristics of relative eigenvalues coincided with the transient process of these two model stimulations,thus verified the influence law of various parameters to major eigenvalues of the system.Such small-signal model can be seen as an efficient tool to analyze dynamic characteristics of three-phase inverter withcharacteristics of virtual synchronous generator.