虚拟同步发电机的暂态稳定性分析

摘要

虚拟同步发电机通过模拟传统同步发电机的摇摆方程实现换流器的虚拟惯性控制,在大扰动下同样存在暂态失稳现象.文中分析了单机无穷大母线连接方式下虚拟同步发电机的暂态稳定性.首先,建立了虚拟同步控制的换流器的大信号模型并基于奇异摄动理论对系统进行降阶,通过与电磁暂态仿真模型进行对比验证了模型的正确性.然后,在此基础上引入胞映射方法对降阶模型的全局非线性进行分析,求出了以虚拟角速度和虚拟相角表示的相平面的吸引域及故障临界切除时间,并对影响虚拟同步发电机大扰动下稳定性的关键因素进行分析,分析结果与小信号分析的结果进行对比.分析表明,系统参数如电网内阻抗、输送功率、虚拟惯量、阻尼系数及滤波器参数等都对虚拟同步发电机的暂态稳定性有重要影响.最后,基于MATLAB/Simulink 仿真验证了结论的正确性.%The virtual synchronous generator(VSG)realizes the virtual inertia control of the converter by simulating the swing equation of traditional synchronous generator,which also suffers the transient instability under large disturbance.This paper analyzes the transient stability of the VSG connected to the infinite bus.Firstly,the large signal model of the inverter controlled by the VSG is established and the system order is reduced based on the singular perturbation theory.The correctness of the model is verified by comparison with the electromagnetic transient simulation model.On this basis,the cell mapping method is introduced to analyze the global nonlinear characteristics of the reduced order model.The region of attraction in the phase plane,which is represented by the virtual angular velocity and the virtual phase angle is found and the key factors that affect the stability of the VSG under large disturbance are analyzed.The results of the analysis are compared with the results of the small signal analysis,which shows that system parameters,such as the internal impedance of the power grid,the feeding power,the virtual inertia,the damping coefficient and the filter parameters,have significant influences on the transient stability of the VSG under large disturbance.Finally,based on MATLAB/Simulink simulation,the rationality of the proposed method is verified.