Two-stage current-limiting control strategy for direct-droop-controlled grid-forming inverters

Abstract

This document describes systems and techniques for a control system for a grid-forming inverter. In aspects, a reactive power current-limiting subsystem, based on a measured reactive power, is configured to generate a first signal representing a magnitude of a modulation waveform presentable to a pulse-width modulator configured to direct transistors in the inverter of the grid-forming inverter. An active power current-limiting subsystem, based at least in part on a measured active power, is configured to generate a second signal representing a rotating phase angle of the modulation waveform presentable to the pulse-width modulator. The reactive power current-limiting subsystem and active power current-limiting subsystem are configured to cause an alternating current (AC) output of the grid-forming inverter to resume a nominal form subsequent to current being directed around one or more transistors in an inverter to prevent an excessive output current from flowing through the one or more transistors.