Learning Exact Topology of a Loopy Power Grid from Ambient Dynamics

Estimation of the operational topology of the power grid is necessary for optimal market settlement and reliable dynamic operation of the grid. This paper presents a novel framework for topology estimation for general power grids (loopy or radial) using time-series measurements of nodal voltage phase angles that arise from the swing dynamics. Our learning framework utilizes multivariate Wiener filtering to unravel the interaction between fluctuations in voltage angles at different nodes and identifies operational edges by considering the phase response of the elements of the multivariate Wiener filter. The performance of our learning framework is demonstrated through simulations on standard IEEE test cases.Comment: accepted as a short paper in ACM eEnergy 2017, Hong Kon

The location of the axon initial segment affects the bandwidth of spike initiation dynamics

The dynamics and the sharp onset of action potential (AP) generation have recently been the subject of intense experimental and theoretical investigations. According to the resistive coupling theory, an electrotonic interplay between the site of AP initiation in the axon and the somato-dendritic load determines the AP waveform. This phenomenon not only alters the shape of AP recorded at the soma, but also determines the dynamics of excitability across a variety of time scales. Supporting this statement, here we generalize a previous numerical study and extend it to the quantification of the input-output gain of the neuronal dynamical response. We consider three classes of multicompartmental mathematical models, ranging from ball-and-stick simplified descriptions of neuronal excitability to 3D-reconstructed biophysical models of excitatory neurons of rodent and human cortical tissue. For each model, we demonstrate that increasing the distance between the axonal site of AP initiation and the soma markedly increases the bandwidth of neuronal response properties. We finally consider the Liquid State Machine paradigm, exploring the impact of altering the site of AP initiation at the level of a neuronal population, and demonstrate that an optimal distance exists to boost the computational performance of the network in a simple classification task. Copyright

Coordinated Control Of The Modern Grid: High-Bandwidth Optimal Coordination, Inference, And Verification

University of Minnesota Ph.D. dissertation. March 2020. Major: Electrical/Computer Engineering. Advisor: Murti Salapaka. 1 computer file (PDF); x, 126 pages.Modernization of electric grids worldwide continues in earnest, with increasing deployments of renewable and distributed energy resources (DERs); flexible loads with evolving usage patterns; and new control solutions in distribution networks. The convergence of these new technologies inherently increases the complexity of the power system; and maintaining safe, reliable, and efficient operation of modern grids relies on the successful integration of these many technologies together. Achieving successful modern grid control solutions requires not only the development of innovative distributed coordination techniques, but also methods to effectively and accurately test such complex solutions prior to field deployment and approaches to achieve cost-effective, high-bandwidth, inference capabilities in buildings and distribution grids. In the first part of this thesis, we make important contributions to the design of power hardware-in-the-loop (PHIL) simulations, an important tool for derisking modern grid technologies in a controlled laboratory setting. This technique allows actual at-power devices and systems to be interconnected in software simulations of complex, large-scale power system scenarios to evaluate their closed-loop interaction. We develop a novel approach to designing PHIL simulation interfaces that maximizes simulation bandwidth and accuracy by leveraging a modern control framework that explicitly considers objectives on accuracy and can automatically synthesize a single, optimal controller that meets these objectives while stabilizing the closed-loop system. This method improves upon common approaches to PHIL interface design that typically involve multiple steps of manual compensation and stabilization design that can result in interfaces that are stable but have suboptimal bandwidth and accuracy. The approach developed is general and can be applied to most PHIL system configurations. We also present a practical method and metrics for verifying the true accuracy of PHIL simulation results without relying on relative comparisons to potentially inaccurate models or previous simulation results. We demonstrate the accuracy evaluation method and show the improved performance achievable when using the optimal PHIL interface design approach in an experimental case study involving a 100-kVA battery inverter. The second part of this thesis develops a novel approach for high-frequency, multi-class nonintrusive load monitoring (NILM) that enables effective net-load monitoring capabilities with minimal additional equipment and cost. Relative to existing NILM work, the proposed solution operates at a faster timescale, providing accurate multiclass state predictions for each 60-Hz ac cycle without relying on event-detection techniques. We also introduce an innovative hybrid classification-regression method that allows for the prediction of not only load on/off states via classification but also their individual operating power levels via regression. The overall approach is validated using a test bed with eight residential appliances and is shown to have high accuracy, good scaling and generalization properties, and sufficient response time to support building grid-interactive control at fast timescales relevant to the provision of grid frequency support services. The third part of this thesis develops and experimentally demonstrates a first-of-its-kind hierarchical control solution for optimally dispatching thousands of deferrable loads and DERs across a distribution feeder to provide fast frequency response (FFR) within 500 ms to the bulk power system. This approach rapidly coordinates resources online after a frequency event occurs, allowing fast-changing, behind-the-meter resources to be incorporated and aggregate FFR power set points to be achieved more quickly and accurately than existing approaches. We also present a solution for determining the optimal amount of headroom to operate solar inverters with to minimize opportunity cost while ensuring the FFR response viability of a building with the inverter and deferrable loads. We develop practical algorithms for fast, cost-based optimal dispatch at multiple aggregation scales, establish their optimality, and demonstrate via simulation that they are faster than state-of-the-art, coordinated frequency response approaches. The entire control platform developed is implemented and experimentally verified using a unique PHIL demonstration, including more than 100 powered loads and DERs connected to a real-world distribution network model. Experimental results from multiple scenarios confirm that the optimal FFR dispatch approach scales well and can optimally coordinate more than 10,000 net-load resources across a distribution network while achieving hardware response times within 500 ms, which is not possible using existing optimal coordination approaches

An advanced platform for development and evaluation of grid interconnection systems using hardware-in-the-loop

The recently highlighted vulnerabilities, environmental effects, and critically aging status of the North American Electric Power System (EPS) are fueling a shift towards a power system paradigm that more fully leverages Distributed Resources (DRs). In order to support and accelerate DR grid integration, methods to rapidly evaluate DRs against existing grid interconnection standards and assess advanced DRs integrated in complex EPS scenarios are needed. This thesis develops a novel solution for rapid evaluation of DR grid interconnection standard conformance that uses a real-time simulator and a single graphical user interface to automate the time-consuming process required for the many repeated conformance tests of IEEE Std 1547.1™. A method for evaluating advanced DR grid integration scenarios using Power Hardware-in-the-Loop (PHIL) is presented. The results from a novel demonstration of a DR grid integration scenario using both PHIL-based and hardware-only approaches are presented, establishing the utility and validity of the PHIL method