虚拟同步发电机的输入阻抗建模及稳定性分析

Input Impedance Modeling and Stability Analysis for Virtual Synchronous Generator

虚拟同步发电机(virtual synchronous generator,VSG)和前级接口变换器的交互稳定对其可靠实现调频、调压等辅助服务功能至关重要。采用阻抗分析方法是解决该类问题的有效途径,但需要获知前后级子系统准确的阻抗模型。为此,建立了计及滤波器寄生参数的三相并网逆变器小信号电路模型,推导出VSG的闭环输入阻抗模型,深入探讨了功率环参数、功率指令和电网运行条件等因素对闭环输入阻抗的影响,并分析了VSG与前级接口变换器的交互稳定性。最后,通过10kVA的MATLAB/simulink仿真模型对理论分析的正确性进行了仿真验证。

The interactive stability of the virtual synchronous generator(VSG) and the front-end dc-dc interface converter is critical for VSG to reliably supply the auxiliary services such as frequency regulation, voltage regulation, and so on. The impedance analysis method is widely used to address the interactive stability issues, which depends closely on the accurate impedance models of the front-end and the rear-end subsystems. In this paper, the small-signal impedance model of VSG considering the parasitic resistance of the filters is established. Then, the influence of the power loop parameters, the power references and the grid operating conditions on the closed-loop input impedance is deeply studied. Finally, the interaction stability between VSG and the front-end photovoltaic/energy-storage interface converter is analyzed with the deduced impedance model. The correctness of the theoretical analysis is verified by a 10 k VA simulation model in MATLAB/Simulink.