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We propose a novel stochastic consensus-based secondary voltage and frequency restoration scheme with communication delays and noises for islanded microgrids (µGs). Existing distributed methods commonly design restoration layer with the assumption of ideal communication among distributed generations (DGs). Albeit, the communication channels are exposed to delay and noise, whereas any DG receives delayed and noisy measurements from its neighbors due to peripheral noises and communication delays. Delay and noise have a great impact on the control of µG, which terribly reduce the stability and quality of it. To eliminate the adverse effects of delays and noises, we propose novel consensus protocols that consider effects of the communication noises and delays simultaneously for complete plant dynamics, and study mean square consensus for frequency and voltage restoration of µGs whereas providing stringent real power sharing. To this end, we derive the mean square consensus restoration proof using rigorous Lyapunov analysis. As a result the suggested method decreases the sensitivity of the system to failures and increases its reliability. Finally, we have done several simulation scenarios in MATLAB/SimPowerSystems Toolbox to verify the proposed strategy performance.

Existence of Generalized interline power-flow controller (GIPFC) in a transmission line changes the voltage and current signals which are measured with the protection relays of power system dynamically. In this paper, the effects of the GIPFC on the measured impedance by loss of excitation (LOE) relay of synchronous generator are firstly investigated by both analytical and computational methods for different operating modes of the power system. Results indicate that the presence of GIPFC causes a substantial delay on the operation of LOE relay. It is also shown that when partial LOE happens, the GIPFC redounds to the LOE relay under-reaching. Consequently, to readjust the relay in the presence of GIPFC, a new modified LOE protection algorithm on the basis of synchronized phasor measurements received from phasor measurement units (PMUs) is presented. The most important advantage of this modified algorithm is that it is a general algorithm which considers all VSC-based FACTS controllers. Regarding the simulations results, it is concluded that using the modified algorithm for the LOE relay can sufficiently decrease the delay and prevent the relay from under-reaching. The impacts of unified power-flow controller (UPFC) and interline power-flow controller (IPFC) on the LOE relay are also demonstrated. Index Terms-Flexible ac transmission system (FACTS) controllers, generalized interline power-flow controller (GIPFC), unified power-flow controller (UPFC), interline power-flow controller (IPFC), generator loss of excitation (LOE) protection, phasor measurement units (PMUs).