Stability Delay Margin Computation of Shipboard Microgrid with Fuel Cell Using Direct Method

This paper investigates the delay-dependent stability of a shipboard microgrid with various energy generation units. The coordination and control of distributed energy sources requires a communication network that induces inevitable time delays. When a disturbance in load or generation arises, these delays impair the controller's function and cause undesirable variances in the system frequency. Determining the largest time delay, or stability delay margin, that the shipboard microgrid is essential that it can endure before turning unstable. In this paper, the stability delay margins are calculated using a frequency-domain method. The technique can identify the crossover frequency and associated delay margin and is based on the removal of exponential terms from the characteristic equation. Stability delay margins for a large set of proportional-integral gains are calculated. Lastly, to verify the theoretical delay margins, time-domain simulations are used.