弱电网接入下跟网型变流器的动态交互与稳定性分析

The grid-connected converter with grid-following control(GCC-GFL)for renewable energy sources has a risk of instability when integrated into the weak grid.This paper aims to investigate the dynamic interactions and stability characteristics of the GCC-GFL system.From a control system perspective,the mechanism of small-signal instability in the system is revealed through dynamic interaction analysis between the GCC-GFL and the weak grid.Meanwhile,a novel stability evaluation index is proposed based on the real and imaginary parts of the equivalent loop gain in a multi-loop control system.On this basis,the dominant loop of the control system leading to system instability is identified.Furthermore,quantitative analyses are conducted to investigate the stability region of the GCC-GFL,consider-ing the influence of AC grid strength,steady-state operating points,and converter control parameters.Finally,the correctness and effectiveness of the proposed methods are verified by the impedance analysis method,the time-domain simulations,and the experiments,respectively.