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Reliable virtual sensing for wireless sensor networks

Several “energy-hungry” sensors such as gas detectors, radar, and cameras have excessive energy dissipation. Virtual sensing is a technique which “breaks the downward spiral” between energy expenditure and events-miss probabilities. The idea is to deactivate main sensors and utilize a set of energy-friendly HW & SW components instead. However, reliability of such systems composed of virtual and real sensors should be as high as possible. In this article, a novel approach is proposed to improve the virtual sensing reliability. An ontology on sensor-environment relationships is utilized to automatically generate rules before deployment to switch between real and virtual sensors.

We illustrate the general approach by a case study: we show how reliable virtual sensing reduces the energy consumption and event-miss probabilities of object tracking applications. Seismic sensors and a dynamic time-warping algorithm shape the virtual object tracking sensor. We validate the precision of such virtual sensors over several experiments. A series of experiments with a network of TelosB sensor nodes show that virtual sensors have much less energy consumption than a Doppler μ-radar (main) sensor. Finally, we evaluate event-miss probabilities and lifetime extension by using the WSNetsimulator.

A Multiple Train Trajectory Optimization to Minimize Energy Consumption and Delay

In railway operations, if the journey of a preceding train is disturbed, the service interval between it and the following trains may fall below the minimum line headway distance. If this occurs, train interactions will happen, which will result in extra energy usage, knock-on delays, and penalties for the operators. This paper describes a train trajectory (driving speed curve) optimization study to consider the tradeoff between reductions in train energy usage against increases in delay penalty in a delay situation with a fixed block signaling system.

The interactions between trains are considered by recalculating the behavior of the second and subsequent trains based on the performance of all trains in the network, apart from the leading train. A multitrain simulator was developed specifically for the study. Three searching methods, namely, enhanced brute force, ant colony optimization, and genetic algorithm, are implemented in order to find the optimal results quickly and efficiently. The result shows that, by using optimal train trajectories and driving styles, interactions between trains can be reduced, thereby improving performance and reducing the energy required. This also has the effect of improving safety and passenger comfort.

Real-Time Optimal Voltage Regulation for Distribution Networks Incorporating High Penetration of PEVs

This paper proposes a vehicle-to-grid reactive power support (V2GQ) strategy for optimal coordinated voltage regulation in distribution networks with high distributed generation (DG) penetration. The proposed algorithm employs plug-in electric vehicles (PEVs), DG, and on-load tap changer (OLTC) to satisfy PEV charging demand and grid voltage requirements with relaxed tap operation, and minimum DG active power curtailment. The voltage regulation problem is formulated as a nonlinear programming and consists of three consecutive stages, in which successive stages apply the outputs of their preceding stages as constraints.

The first stage aims to maximize the energy delivered to PEVs to assure PEV owner satisfactions. The second stage maximizes the DG extracted active power. Third stage minimizes the voltage deviation from its nominal value utilizing the available PEV and DG reactive powers. The main implicit objective of the third stage problem is relaxing the OLTC tap operation. In addition, the conventional OLTC control is replaced by a proposed centralized controller that utilizes the output of the third stage to set its tap position. Real-time simulations are developed to demonstrate the effectiveness of the proposed optimal coordinated algorithm on a typical distribution network using OPAL-RT real-time simulator (RTS) in a hardware-in-the-loop (HIL) application.

Voltage control algorithm for distribution systems with distributed generation

This paper proposes an automatic voltage control method for distribution networks using distributed generators connected to the grid in order to maintain voltage levels and to provide reactive power. This method consists in exchanging information withn a two-layer hierarchical control structure. The first one is the local control, responsible for monitoring each generator operating conditions.

The second one is the central control, responsible for providing the appropriate setpoints to each local control with an algorithm based on the sensitivity theory. This method is based on a sensitivity theory that chooses the generator which will cause the major impact on the network voltage profile when changing its reactive power injection. In order to test the proposed method, the authors implemented the IEEE 13-node test feeder in the Real Time Digital Simulator at Escola Politecnica da Universidade de Sao Paulo – Brazil.

Cyber Security and Operational Reliability

This paper presents a new proposed infrastructure that enables simultaneous cyber security and operational security. The basis of the method is command interception and fast authentication from the cyber security point of view (reliable detection of cyber intrusions) and from the operational reliability point of view. To simplify the process, the command authentication is done at the relay level and relay controls. As such it does not depend on the communication architecture. The method is based on new developments on dynamic state estimation based protection and substation level distributed state estimation. This infrastructure provides the capability to monitor, intercept, and authenticate/block commands as they reach the relay and the control circuits of the relay. Since all controls are exercise through a relay, this approach provides 100% coverage.

The authentication/blockage of commands is done quickly because of the distributed approach which enables quick assembly of a local real time model and fast analytics with this local model. Specifically, for each command the proper local real time model is constructed and quickly analyzed to determine the effects on the power system. The analytics determine the effect of the command, if executed, on the system and in particular on the operational reliability of the system. In case of a command that may have adverse effects on the operational reliability of the system, the command will be blocked and the operator will be alerted. In addition to the command authentication at the relay level, an open-source real-time network monitoring system for capturing and parsing network traffic is presented. Because the method is based on the substation level dynamic state estimator which uses only local substation level measurements and data, a byzantine type attack is not considered possible for the proposed approach. Finally, a discussion on the architecture required to integrate the network monitoring and state estimation sys- ems is presented. The methodology is presently being tested in a laboratory setup that includes a digital simulator of the electric power system and hardware in the loop.