Multiple Grid-Forming Inverters in Black-Start: The Challenges

Black-start of multiple grid-forming inverters is one of the major challenges toward implementing grid of microgrids. In this article, the technical challenges for the black-start of multiple grid-forming inverters are reported. Specifically, this article discusses inverter synchronization, voltage and frequency regulations, and power-sharing between multiple grid-forming inverters. Furthermore, a control scheme for black-start operation is developed for grid-forming inverters in this work. Some experiment results have been provided to support the proposed controller performance and some technical challenges. The experiments have been performed using a 208V, 60Hz, 30kVA islanded small-scale nanogrid powered by multiple inverters.