Current Limiting Method for Voltage Source Grid-Forming Inverters

Inhalt:
Grid-forming inverters are targeted for the future electric-grids thank to their enhanced stability features, including fault ride-through performances. When operated under direct voltage control, handling overcurrent is an issue for grid-forming schemes. Hence, limiting current control strategies have been proposed. One of them is switching from voltage to current control, nevertheless, it needs two controllers running in parallel, which increases the computational effort and brings to saturation problems. This work proposes a dual voltage/current tracking controller, based on a passivity control law (state feedback based), which serves as common structure between both the voltage/current controllers. When a fault is detected, a switch to current control is enabled, reducing the current to safe values in less than 10 switching periods. Current controller is composed only by proportional terms, avoiding anti-windups schemes. Experimental results are provided to validate the proposed method.