Alexandra von Meier

Micro-synchrophasors for distribution systems

This paper describes a research project to develop a network of high-precision phasor measurement units, termed micro-synchrophasors or μPMUs, and explore the applications of μPMU data for electric power distribution systems.

The Local Team: Leveraging Distributed Resources to Improve Resilience

In recent years, extreme weather events have severely affected the performance of the electric grid. Very large-scale events (VLSE) with potentially catastrophic impacts on the grid pose more than an inconvenience in todays electricity-driven lifestyle, and the frequency and severity of such events may continue to increase as a consequence of global climate change. This article summarizes the state of the art in leveraging distributed resources to improve resilience of the electric grid. It also highlights the technical questions that need to be addressed through additional research and development if the value of distributed resources is to be maximized.

DISTIL: Design and implementation of a scalable synchrophasor data processing system

The introduction and deployment of cheap, high precision, high-sample-rate next-generation synchrophasors en masse in both the transmission and distribution tier - while invaluable for event diagnosis, situational awareness and capacity planning - poses a problem for existing methods of phasor data analysis and storage. Addressing this, we present the design and implementation of a novel architecture for synchrophasor data analysis on distributed commodity hardware. At the core is a new feature-rich timeseries store, BTrDB. Capable of sustained writes and reads in excess of 16 million points per second per cluster node, advanced query functionality and highly efficient storage, this database enables novel analysis and visualization techniques. Leveraging this, a distillate framework has been developed that enables agile development of scalable analysis pipelines with strict guarantees on result integrity despite asynchronous changes in data or out of order arrival. Finally, the system is evaluated in a pilot deployment, archiving more than 216 billion raw datapoints and 515 billion derived datapoints from 13 devices in just 3.9TB. We show that the system is capable of scaling to handle complex analytics and storage for tens of thousands of next-generation synchrophasors on off-the-shelf servers.

Abnormal event detection with high resolution micro-PMU data

Power system has been incorporating increasing amount of unconventional generations and loads such as renewable resources, electric vehicles, and controllable loads. The induced short term and stochastic power flow requires high resolution monitoring technology and agile decision support techniques for system diagnosis and control. In this paper, we discuss the application of micro-phasor measurement unit (μPMU) for power distribution network monitoring, and study learning based data-driven methods for abnormal event detection. We first resolve the challenging problem of information representation for the multiple streams of high resolution μPMU data, by proposing a pooling-picking scheme. With that, a kernel Principle Component Analysis (kPCA) is adopted to build statistical models for nominal state and detect possible anomalies. To distinguish event types, we propose a novel discriminative method that only requires partial expert knowledge for training. Finally, our methods are tested on an actual distribution network with μPMUs, and the results justifies the effectiveness of the data driven event detection framework, as well as its potentials to serve as one of the core algorithms to ensure power system security and reliability.

A Linear Power Flow Formulation for Three-Phase Distribution Systems

Power flow analysis is one of the tools that is required in most of the distribution system studies. An important characteristic of distribution systems is the load unbalance in the phases and a three-phase power flow analysis is needed. In this paper, a three-phase linear power flow (3LPF) formulation is derived based on the fact that in a typical distribution system, voltage angles and magnitudes vary within relatively narrow boundaries. The accuracy of the proposed 3LPF is verified using several test cases. Potential applications of the proposed method are in distribution systems state estimation and volt-VAR optimization.

A data-driven analysis of capacitor bank operation at a distribution feeder using micro-PMU data

In this paper, we conduct a data-driven experimental analysis on capacitor bank switching event at a distribution grid in Riverside, CA using data from two distribution level phasor measurement units, a.k.a, μPMUs. Of particular interest was to detect the capacitor bank switching events based on feeder-level and load-level μPMUs and thus eliminating the need to install separate sensors for the switched capacitor banks. In addition, the operational parameters of capacitor bank is investigated. Moreover, the dynamic effects of capacitor bank switching events is also considered through voltage and current synchrophasor data. This paper takes a first step in using μPMU data to conducting a detailed analysis of how different voltage-levels are affected by capacitor bank switching events in distribution systems.

Every Moment Counts: Synchrophasors for Distribution Networks with Variable Resources

Historically, with mostly radial power distribution and one-way power flow, it was only necessary to evaluate the envelope of design conditions, e.g., peak loads or fault currents, rather than continually observe the operating state. But the growth of distributed energy resources introduces variability, uncertainty, and opportunities to recruit diverse resources for grid services. This chapter addresses how the direct measurement of voltage phase angle might enable new strategies for managing distribution networks with diverse, active components.

Integration of renewable generation in California: Coordination challenges in time and space

The successful integration of intermittent and distributed electric generation from renewable resources can be viewed as a coordination problem at multiple scales in both space and time. This paper presents an overview of coordination issues relative to the goals for renewable integration in California.

Optimal dispatch of reactive power for voltage regulation and balancing in unbalanced distribution systems

Optimization of distributed power assets is a powerful tool that has the potential to assist utility efforts to ensure customer voltages are within pre-defined tolerances and to improve distribution system operations. While convex relaxations of Optimal Power Flow (OPF) problems have been proposed for both balanced and unbalanced networks, these approaches do not provide universal convexity guarantees and scale inefficiently as network size and the number of constraints increase. In balanced networks, a linearized model of power flow, the LinDistFlow model, has been successfully employed to solve approximate OPF problems quickly and with high degrees of accuracy. In this work, an extension of the LinDistFlow model is proposed for unbalanced distribution systems, and is subsequently used to formulate an approximate unbalanced OPF problem that uses VAR assets for voltage balancing and regulation. Simulation results on the IEEE 13 node test feeder demonstrate the ability of the unbalanced LinDistFlow model to perform voltage regulation and balance system voltages.

The disposition of excess weapons plutonium: A comparison of three narrative contexts

The Nonproliferation Review/Winter 1998 20 Alexandra von Meier, who received her Ph.D. in Energy and Resources from U.C. Berkeley in 1995, is an Associate Specialist at the Center for Nuclear and Toxic Waste Management. Jennifer Miller is a doctoral candidate in the Department of Rhetoric, and Ann Keller is a doctoral candidate in the Department of Political Science, all at the University of California, Berkeley. THE DISPOSITION OF EXCESS WEAPONS PLUTONIUM: A COMPARISON OF THREE NARRATIVE CONTEXTS