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Real-time awareness of the phasor state, including the volatile frequency and phase angle, is critical to maintain reliable and stable operations of the power grid. However, the high cost and low accessibility of current synchrophasors restrict their large-scale deployment over highly distributed microgrids. In this paper, we present a practical system design for monitoring the microgrid frequency and phase angle over mobile platforms and significantly reduce the cost of such monitoring. Being different from current synchrophasors, our system does not rely on continuous GPS reception and hence it is highly accessible and applicable to heterogeneous microgrid scenarios. We develop various techniques to provide the timing signal that is necessary for precise microgrid monitoring. For frequency monitoring, the network time protocol is exploited for time synchronization. For phase angle monitoring which requires a higher timing accuracy, 200 Hz primary synchronization signal being embedded in the 4G LTE cellular signal is harvested for time synchronization. We implemented our system over off-the-shelf smartphones with a few peripheral hardware components and realized an accuracy of 1. 7 MHz and 0. 01 rad for frequency and phase angle monitoring, respectively. Although the accuracy of the prototype is lower than that of the GPS-based systems, the system could still satisfy the requirements of microgrid monitoring. The total cost of the system can be controlled within 100 and no installation cost is required. Experiment results compared with the traditional frequency disturbance recorders verify the effectiveness of our proposed system.
Lu et al. (Fri,) studied this question.