Elevation angle is one of the most significant parameters of land mobile satellite channels, subject to rapid variations in the case of Low Earth Orbit (LEO) satellite systems. In this paper a novel trace-based framework is proposed and analyzed which is capable of predicting elevation angle as a function of time during satellite visibility window. Tracetime based modeling makes the framework practical for real-time evaluation of elevation angle and its alteration incurred by communication links in LEO satellite systems. The proposed method is particularly suitable for development of communication channel models and services in mobile LEO satellite networks where path variability is of great importance.
Microgrids are prone to network-wide disturbances such as voltage and frequency deviations. Detection of disturbances by a microgrid central controller (MGCC) is therefore necessary for improving the network operation. Motivated by this application, this paper presents a new structure for the centralized detection of disturbances with noisy synchrophasor data and packet delay/dropouts. We build the proposed structure starting from the analysis of noise-delay tradeoff in synchrophasor networks, and developing a new phasor data concentrator (PDC) for compensation of data losses. The statistical performance metrics of the disturbance detector are numerically evaluated in the case of islanding detection, corroborating that the centralized detector counteracts the measurement noise and lowers the detection time.Numerical results show that the proposed structure significantly mitigates the probability of false detection. Moreover, it can achieve the lower bound of average detection time in a wide range of packet drop rates. This study is useful to network designers who need to employ data acquisition systems for reliable and robust microgrid control applications.
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