虚拟同步机并联电流控制型变换器系统暂态同步稳定性分析

并网并联供电系统中,电流控制型变换器注入电流对虚拟同步机暂态同步稳定性有不可忽视的影响,甚至可能导致系统出现不可逆失稳问题.研究并联供电系统中变换器间的交互机理是保证系统在暂态过程中安全稳定运行的重要前提.文中建立了电流控制型变换器与虚拟同步机暂态交互模型,发现注入电流对虚拟同步机暂态稳定性的影响主要由功率耦合项决定.在此基础上,利用等面积准则分别分析了在纯感性和阻感性网络条件下不同注入电流相角对虚拟同步机暂态稳定性的影响.研究结果表明,当注入电流相角与并联线路导纳角相加接近-90°时,系统的稳定性将得到增强.基于PSCAD/EMTDC软件的仿真结果和基于RT-LAB的实验结果验证了理论分析的正确性.

Transient Synchronization Stability Analysis of System with Paralleled Virtual Synchronous Generators and Current-controlled Converters

The injected current of current-controlled converters has unnegligible effect on the transient synchronization stability of virtual synchronous generators (VSGs) in the grid-connected paralleled power supply system, which may result in irreversible instability problem of the system. Studying the interaction mechanism among different converters in the paralleled power supply system is an important prerequisite for ensuring stable operation of the system during the transient period. This paper builds the transient interaction model of VSGs and current-controlled converters. It is found that the effect of injected current on the transient stability of VSG is determined by the power coupling terms. On this basis, the effect of phase angle of injected current on the transient stability of VSG is studied by using equal area criterion (EAC) in both purely inductive and resistive-inductive networks. The research result shows that, when the sum of the phase angle of injected current and the admittance angle of paralleled line is close to -90°, the system stability will be enhanced. The simulation results based on PSCAD/EMTDC and the experimental results based on RT-LAB verify the correctness of the theoretical analysis.