Impact of the voltage feed-forward and current decoupling on VSC current control stability in weak grid based on complex variables

With power converters integrated to the weak power grid, the influences of the voltage feed-forward and the current decoupling on the stability of the current control loop become obvious and need to be considered. Complex transfer functions are applied to analyze the effects of the feed-forward and cross decoupling compensation on the stability of the current control loop. Negative influences of the voltage feed-forward and the current decoupling on the current loop stability are demonstrated based on the complex root locus analysis. The effects of the voltage feed-forward are dominating while the effects of the current decoupling is ignorable. Simulations in Matlab/Simulink are carried out and the results validate the root locus analysis.