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Observing the Power Grid: Working Toward a More Intelligent, Efficient, and Reliable Smart Grid with Increasing User Visibility

As an essential fixture of modern society, electricity is often taken for granted. In many cases, it becomes invisible or is ignored until it is not there or it is time to pay the electric bill. Electricity has been around for well over a century, and the march of industry and progress have created the most complex interconnected system in existence. In a delicate balancing act, the amount of electricity generation must track the amount consumed to prevent the system from collapsing, as there is only very limited storage capacity on the grid. The balance is maintained via a combination of predictions and control systems distributed across the grid. How well this balance is maintained produces signals that propagate across the entire system from the large generators to the wall outlets that are ubiquitous across the world. Observing these signals can provide a great deal of insight into the current status and operation of the power grid and can be done cheaply and accurately from inside a home or office.

A federated simulation toolkit for electric power grid and communication network co-simulation

This paper introduces a federated simulation toolkit (FSKIT) that couples continuous time and discrete event simula- tions (DES) to perform the co-simulation of electric power grids and communication networks. A High Performance Computing (HPC) oriented power system dynamic simulator, GridDyn, was used for the electric power grid simulation. GridDyn is coupled to the open-source network simulator, ns-3, through FSKIT. FSKIT provides time control for advancing the state of federated simulators, and facilitates communication among objects in the federate. A wide-area communication-based electric transmission protection scheme is simulated with FSKIT, using the IEEE 39- bus test system. A communication network for the 39-bus system is built in ns-3, and basic protection relay logic is added to the power system model in order to perform the co-simulation.

Massively parallel acceleration of a document-similarity classifier to detect web attacks

This paper describes our approach to adapting a text document similarity classifier based on the Term Frequency Inverse Document Frequency (TFIDF) metric to two massively multi-core hardware platforms. The TFIDF classifier is used to detect web attacks in HTTP data. In our parallel hardware approaches, we design streaming, real time classifiers by simplifying the sequential algorithm and manipulating the classifiers model to allow decision information to be represented compactly. Parallel implementations on the Tilera 64-core System on Chip and the Xilinx Virtex 5-LX FPGA are presented. For the Tilera, we employ a reduced state machine to recognize dictionary terms without requiring explicit tokenization, and achieve throughput of 37 MB/s at a slightly reduced accuracy. For the FPGA, we have developed a set of software tools to help automate the process of converting training data to synthesizable hardware and to provide a means of trading off between accuracy and resource utilization. The Xilinx Virtex 5-LX implementation requires 0.2% of the memory used by the original algorithm. At 166 MB/s (80X the software) the hardware implementation is able to achieve Gigabit network throughput at the same accuracy as the original algorithm.

Application Experiments: MPPA and FPGA

This paper describes the mapping approach, programmability, and performance of the Ambric Massively Parallel Processor Array (MPPA), and compares these aspects to an FPGA. Two application kernels, a trellis decoder, and n-gram frequency counter, were ported to the Ambric development system and an Altera Stratix II. We find that the mapping strategies to Ambric and FPGAs are similar at the high level, but diverge quite a bit in implementation due to differences in granularity between the basic compute units of the two devices. Both require substantial refactoring from the baseline sequential algorithm. The FPGA proved superior in terms of performance, but the Ambric fares significantly better than the FPGA in programmability and ease of application development.

Design of the HELIGS high-performance transmission-distribution-communication-market go-simulation framework

This paper describes the design rationale for the Hierarchical Engine for Large-scale Infrastructure Co-Simulation (HELICS), a new open-source, cyber-physical-energy co-simulation framework for electric power systems. HELICS is designed to support very-large-scale (100,000+ federates) co-simulations with off-the-shelf power-system, communication, market, and end-use tools. Other key features include cross-platform operating system support, the integration of both event-driven (e.g., packetized communication) and time-series (e.g., power flow) simulations, and the ability to co-iterate among federates to ensure physical model convergence at each time step. After describing the requirements, we evaluate existing co-simulation frameworks, including High-Level Architecture (HLA) and Functional Mockup Interface (FMI), and we conclude that none provide the required features. Then we describe the design for the new, layered HELICS architecture.

Integrated stochastic weather and production simulation modeling

High penetration of intermittent renewable generators can substantially increase the variability and uncertainty in power system operations. Energy storage and demand response have been proposed as resources that can be used to mitigate this uncertainty and variability. This paper describes planning system that couples a stochastic weather model, renewable generation models that are driven by the weather, a stochastic production simulation model, and a system stability model. The system is used to simulate operation of the California grid with 33% variable renewable generation in the year 2020. The values of energy storage and demand response are estimated by identifying the avoided costs of the conventional hydro and fossil resources that they displace when providing regulation, load following, and energy arbitrage functions. The impacts on system stability are also assessed.

A parallel multigrid reduction in time method for power systems

This paper presents a fully multilevel approach to parallel in time solution of transient power system simulations. The method employs a multigrid reduction algorithm in time parallelized using the MPI distributed memory programming model. The method is demonstrated on a simple Single Machine Infinite Bus differential-algebraic equation model problem, for which speedup is obtained for as few as 8 processing cores on a problem with 10,000 time steps. Speedup of a factor of 13 is observed for a 100,000 step version of this simple problem. Based on these results, we expect significantly better speedup on larger problems where more work is available to each processor allowing greater amortization of the parallel communication.

Integration of functional mock-up units into a dynamic power systems simulation tool

Modelica is an object oriented modeling language that allows straightforward specification of differential,algebraic and discrete equations in a standardized format. It has been used in a number of applications to support multi-domain system simulations such as are found in the automotive and aerospace industries. More recently it has begun to be used in the power systems industry. Modelica models can be compiled into functional mock-up interfaces(FMI) which contain standardized interfaces to the modeling equations and dynamically linked libraries which allow the coupling of models with each other or into other simulation software. The interface allows the decoupling of the model from the mathematical solver used for the simulation. In this document we describe in detail the coupling between functional mock-up units and GridDyn, a dynamic power system simulation tool, which incorporates a DAE solver and variable time step methods.

Compressing Phasor Measurement data

Phasor Measurement units (PMUs) are becoming standard equipment in electrical grids around the world. They are capable of generating a significant amount of data on a continuous basis from distribution and transmission networks. Several months of data from 2 PMUs situated on a distribution network were captured in raw format. This data was separated by measurement type and compressed using a number of standard compression algorithms. The results show the compressibility of PMU data for these algorithms and are used to estimate the space requirements for storing a day of data from a single PMU.

Automated low frequency load cutoff

The power grid is changing, new types of generation are increasingly coming on line at both the commercial and consumer scale. As technology improves, energy harvesting, by various means, will force the grid to adapt. Traditional means of control and management may become strained or inadequate for the future grid. The grid is also becoming smarter with increasing interaction between utilities and consumers, and as it becomes more interconnected and interactive, new threats from these interconnections arise. The drive to reduce costs and make the grid more efficient will inevitably push the operation of the grid closer to the safe limits making it increasingly likely small triggers will cause wide scale problems. One potential solution is making the system controls layered with a series of different control mechanisms including both automated and centralized systems. This article explores and demonstrates the development and potential impact of one such consumer level control mechanism. Specifically, we developed a prototype system by which non-essential, non-time critical “dumb” loads can be made to respond to detected events observable in the system frequency, and thereby assist in the recovery from larger events. This system responds in a totally automated fashion without communications or control signals, and thus provide a measure of immunity from communications problems and could replace a small amount of reserves that would otherwise be required. We examine here the construction, operation and potential benefits of such a device.