A universal controller for grid-connected voltage-source converters

Abstract

The power-synchronization control (PSC) and vector current control (VCC), the latter including cascaded outer loops, are, respectively, considered to be grid-forming and grid-following schemes. They have significant structural differences. Despite that, it is here shown that the two schemes can be unified by making a series of minor modifications to PSC. This results in a universal controller, allowing various combinations of the two schemes to be explored. Fundamentally, it allows PSC to be used as a guideline for a robust VCC design, permitting stable and well-performing operation irrespective of the grid strength.