Probability for conditional noncoherency of microgrid due to transmission overloading

Microgrid is capable of connecting the distributed generation to the main grid. With specific outages and loading conditions, noncoherency may exist in the microgrid, i.e. a transmission path undesirably increases possibility of overloading and decreases security and reliability of microgrid. In this paper, coherency analysis is performed to a specific microgrid. Considering unavailability of the transmission branches, the stochastic fluctuation of the loads and distributed generation, the critic loads at different buses yielding noncoherency are quantified. The cumulative probability of the load is derived, which is combined with the critic load curve to quantify probabilities of the critic load and the noncoherency. Impact of the static voltage characteristics of the loads and voltage setting of the generators on noncoherency probability are quantified. Finally, numerical results are provided to validate feasibility of proposed algorithm.