Analysis of a concurrent soft black start using inverter-based generation

The transition towards inverter-based generation introduces new challenges and opportunities in grid restoration. One of these challenges lies in the limited power ratings of inverter-based generation compared to conventional power plants in charge of the black start process. This paper proposes a novel approach to black start utilizing a coordinated soft start process with multiple non-collocated inverters ramping up their voltage outputs simultaneously. First, the concept is demonstrated on a simplified symmetric grid under ideal conditions, where the concurrent energization process overcomes the limitations of individual inverter ratings. The feasibility of this approach is then analyzed against the impact of communication delays. Results show that large power flows during the ramp-up can be avoided by means of proper control parametrization. Finally, the approach is evaluated on a larger grid and under the presence of inrush currents to validate the proposed strategy.