Resilient Networks

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    Communication-free Voltage Regulation in Distribution Networks with Deep PV Penetration
    ( 2020-01-07) El Helou, Rayan ; Kalathil, Dileep ; Xie, Le
    In this paper, we present a scheme of fully localized voltage regulation in distribution grids through reactive power compensation using photovoltaic (PV) inverters. We employ quasi-steady state representation of the effect of incremental changes in reactive power on voltage, in the form of discrete-time dynamics. We prove using this representation that nodal voltages may be regulated with guaranteed stability in the sense of Lyapunov without any node-to-node communication. We present properties of this communication-free control, such as guarantees on when it works and when it fails. Numerical studies based on realistic distribution network parameters are conducted to illustrate the performance and robustness of this proposed method with respect to changes of operating conditions and system parameters.
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    Impact of GPS Spoofing on HVDC Modulation
    ( 2020-01-07) Venkatasubramanian, Mani ; Eastlake, Nathan
    This paper investigates a variety of scenarios in which control signals utilized in high-voltage DC (HVDC) modulation are subjected to oscillatory error due to GPS spoofing of phasor measurement unit (PMU) time synchronization. The result of this spoofing is the presence of forced oscillations in a system through HVDC modulation due to cyclic erroneous measurements. These scenarios are tested in the Kundur two-area system with a supplementary HVDC line which utilizes various supplementary controllers for modulation. The simulation results are examined for system transient behavior as well as for the observable small-signal effects of the GPS spoofed control signals across the system. It is found that the harmonics of the spoofed control signal frequencies can interact with the inter-area modes of the system, resulting in resonant oscillations and the severity of the oscillations is dependent upon the magnitude of the time-error and the damping levels of the system modes.
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    Dynamics-aware Continuous-time Economic Dispatch: A Solution for Optimal Frequency Regulation
    ( 2020-01-07) Khatami, Roohallah ; Parvania, Masood ; Chen, Christine ; Guggilam, Swaroop ; Dhople, Sairaj
    This paper outlines a continuous-time economic dispatch (CTED) problem that intrinsically embeds dynamic constraints arising from the electromechanical behavior of synchronous generators and enables near-to-real-time optimal scheduling of generation. In its original form, the CTED problem is infinite-dimensional, however, we present a linear-programming reformulation that offers computational burden comparable to traditional economic dispatch. The resulting optimal dispatch trajectories are continuously differentiable and induce only small-signal variations in automatic generation control signals. In addition to yielding better system frequency response, this improves economic efficiency since the dispatch cost is better aligned with the actual cost of operating the system. We demonstrate the economic advantages and dynamic-performance improvements of the proposed method with time-domain simulations for a detailed differential algebraic equation model of an illustrative power network.
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    Fast, Approximate State Estimation Based Approach for Cyber Threat Detection in Power Systems
    ( 2020-01-07) Chattopadhyay, Abhiroop ; Dasgupta, Sujay ; Macwan, Richard ; Valdes, Alfonso ; Nuqui, Reynaldo ; Gross, George ; Sauer, Pete
    Increasing reliance on cyber-components for communication and control has made cybersecurity in power systems an increasing concern. While Information technology (IT) based detection and prevention methods are deployed to detect cyber threats, leveraging of the system physics provides a complementary detection scheme. Here, we consider malicious power order threats directed at a high-voltage direct current (HVDC) line in a large AC network. A fast, approximate tracking state estimation method is investigated that uses a reduced iteration count and measurement prioritization using power transfer distribution factors (PTDF) to rapidly compute the approximate injections at the AC buses of the HVDC line as a power order is executed. The algorithm’s accuracy in tracking the system’s change is investigated. It is observed that with the above methods, the estimator can achieve results within 5% of the true injection. Deviations from the expected injection can be understood to be indicative of a compromised power order.
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    Planning Sensitivities for Building Contingency Robustness and Graph Properties into Large Synthetic Grids
    ( 2020-01-07) Birchfield, Adam ; Overbye, Thomas
    Interest in promoting innovation for large, high-voltage power grids has driven recent efforts to reproduce actual system properties in synthetic electric grids, which are fictitious datasets designed to be large, complex, realistic, and totally public. This paper presents new techniques based on system planning sensitivities, integrated into a synthesis methodology to mimic the constraints used in designing actual grids. This approach improves on previous work by explicitly quantifying each candidate transmission line’s contribution to contingency robustness, balancing that with geographic and topological metrics. Example synthetic grids build with this method are compared to actual transmission grids, showing that the emulated careful design also achieves observed complex network properties. The results shed light on how the underlying graph structure of power grids reflects the engineering requirements of their design. Moreover, the datasets synthesized here provide researchers in many fields with public power system test cases that are detailed and realistic.