Grid 1 :A Design Methodology for Smart LED Lighting
Systems Powered By Weakly Regulated Renewable Power Grids
This paper appears in: Smart
Grid, IEEE Transactions on
Issue Date: Sept. 2011
The increasing use of intermittent
renewable energy sources to decarbonize electric
power generation is expected to introduce dynamic instability to the mains.
This situation is of particular concern for mini-grids or isolated grids in
which wind and/or solar power sources are the dominant or the sole power
sources. In this paper, we utilize the photo-electro-thermal theory to develop
a design methodology for LED lighting systems for weakly regulated voltage
sources, with the objectives of minimizing the fluctuation of the human
luminous perception and adopting reliable LED driver with long lifetime and
robustness against extreme weather conditions. The proposed LED system,
practically verified in a 10 kVA small power grid driven
by an ac voltage source and a wind energy simulator, can be considered as a
smart load with its load demand following the power generation. A typical swing
of 40 V in the mains will cause only 15% actual light variation in a 132 W LED
system when compared with 40% change in 150 W high-pressure-sodium lamp system.
The design methodology enables future large-scale LED systems to be designed as
a new generation of smart loads that can adapt to the voltage and power
fluctuations arising from the intermittent nature of renewable energy sources.
Grid 2 :A Simple Adaptive Overcurrent
Protection of Distribution Systems With Distributed Generation
This paper appears in: Smart Grid, IEEE Transactions
on
Issue Date: Sept. 2011
A
significant increase in the penetration of distributed generation has resulted
in a possibility of operating distribution systems with distributed generation
in islanded mode. However, overcurrent protection of
an islanded distribution system is still an issue due to the difference in
fault current when the distribution system is connected to the grid and when it
is islanded. This paper proposes the use of adaptive protection, using local
information, to overcome the challenges of the overcurrent
protection in distribution systems with distributed generation. The trip
characteristics of the relays are updated by detecting operating states (grid
connected or island) and the faulted section. The paper also proposes faulted
section detection using time overcurrent
characteristics of the protective relays. Simulation results show that the
operating state and faulted section can be correctly identified and the
protection system settings can be updated to clear the faults faster.
Grid 3 :Hedging Against Uncertainty: A Tale of Internet
Data Center Operations Under Smart Grid Environment
This
paper appears in: Smart Grid, IEEE Transactions on
Issue Date: Sept. 2011
Internet
Data Center (IDC) supports the reliable operations of many important online services. As the
demand of Internet services and cloud computing keep increasing in recent
years, the power usage associated with IDC operations had been surging
significantly. Such mass power consumption has brought heavy burden on IDC
operators. Recently there are extensive research on
power management for IDCs. However, one important challenge faced by IDC operators
has been overlooked. How to handle the uncertainties in IDC operations is a
challenging task. The uncertainties come from both the dynamic workload and
time-varying electricity prices. In this paper, we systematically investigate
the problem of minimizing the operation risk of IDCs against those
uncertainties at the same time guaranteeing quality of service under
deregulated electricity market environment. We propose a novel hedging scheme
and model the operation risk minimization problem as a bilevel
programming. We also design an optimal hedging algorithm. We conduct extensive
evaluations based on real-life workload data from Google and electricity price
data from deregulated electricity market for multiple IDC locations. Results
show that our scheme can significantly reduce the operation risk by countering
the uncertainties.
Grid 4 :Real-Time Coordination of Plug-In Electric
Vehicle Charging in Smart Grids to Minimize Power Losses and Improve Voltage
Profile
This paper appears in: Smart Grid, IEEE Transactions
on
Issue Date: Sept. 2011
This paper proposes a novel load management solution for coordinating the charging of multiple plug-in electric vehicles (PEVs) in a smart grid system. Utilities are becoming concerned about the potential stresses, performance degradations and overloads that may occur in distribution systems with multiple domestic PEV charging activities. Uncontrolled and random PEV charging can cause increased power losses, overloads and voltage fluctuations, which are all detrimental to the reliability and security of newly developing smart grids. Therefore, a real-time smart load management (RT-SLM) control strategy is proposed and developed for the coordination of PEV charging based on real-time (e.g., every 5 min) minimization of total cost of generating the energy plus the associated grid energy losses. The approach reduces generation cost by incorporating time-varying market energy prices and PEV owner preferred charging time zones based on priority selection. The RT-SLM algorithm appropriately considers random plug-in of PEVs and utilizes the maximum sensitivities selection (MSS) optimization. This approach enables PEVs to begin charging as soon as possible considering priority-charging time zones while complying with network operation criteria (such as losses, generation limits, and voltage profile). Simulation results are presented to demonstrate the performance of SLM for the modified IEEE 23 kV distribution system connected to several low voltage residential networks populated with PEVs.
Grid 5 :Smart Power Router: A Flexible Agent-Based
Converter Interface in Active Distribution Networks
This
paper appears in: Smart Grid, IEEE Transactions on
Issue Date: Sept. 2011
Due to the large-scale implementation of distributed generation, the power delivery system is changing gradually from a “vertically” to a “horizontally” controlled and operated structure. This transition has prompted the emergence of the active distribution network (ADN) concept as an efficient and flexible distribution system to deal with various challenging issues. This paper addresses a multiagent system (MAS) as a suitable technology to manage autonomous control actions and perform the coordination in an ADN. In this agent-based ADN a smart power router is implemented, which can flexibly integrate network areas and optimally manage power flows. Operational and control functions of the power router has been investigated in a laboratory experiment. In this lab setup, a configuration of the power router is established in a combination of a three-inverter system and an agent. The experiments show that the ADN can operate in an efficient and flexible way with the support of the power router interface. The control function of the inverters and the operation of MAS are thoroughly verified.
Grid
6 :A Physical and Logical Security Framework
for Multilevel AFCI Systems in Smart Grid
This paper appears in: Smart Grid, IEEE Transactions
on
Issue Date: Sept. 2011
The arc fault circuit interrupter (AFCI) is expected to be one of the most essential components in smart grid systems for providing physical security and safety against electrical fire hazards caused by arc faults. As AFCIs are widely deployed as a part of mandatory installation requirements, a hierarchy consisting of multilevel AFCIs has been established, where a portable AFCI is connected serially to an outlet box AFCI. However, this multilevel AFCI structure causes serious problems when the AFCI detects arc faults in the surveillance area of its descendant AFCIs. This can cause de-energizing of the entire area covered by the upper-level AFCI, which may lead to blackouts over large areas. This paper proposes an integrated security framework comprised of physical and logical security measures as a solution for this problem. Firstly, the problem is tackled through communication between the hierarchy levels. Since the proposed system deals with physical security and safety, the communication must guarantee reliable message delivery within the specified deadlines. A controller area network (CAN) is chosen as the communication technology because it provides deterministic message delivery that meets the system requirements. Moreover, CAN has the advantages of verified performance and cost competitiveness through accelerated industrial adoption. Along with the physical security framework, a logical security framework is also proposed with group key management that prevents unauthorized access. Finally, this paper reports an integrated methodology for optimizing the design parameters satisfying the bandwidth and security demands of physical and logical measures because both demands competitively share a common communication resource.
Grid 7 :Design of a Hall Effect Current Microsensor for Power Networks
This paper appears in: Smart Grid, IEEE Transactions
on
Issue Date: Sept. 2011
Current
transformers (CTs) are used to measure line currents in a power network for
indicative and protective purposes. However, due to magnetic hysteresis in the
cores, traditional CTs may saturate when they detect large fault currents.
Thus, a more efficient and accurate device is required. This paper aims at
designing a more economical device, a microsensor to
measure power network currents. The characteristics of this new design are
measured and discussed. The new component will not be saturated for fault
currents as high as 40 kA and can be used directly with an intelligent
protective system or a digital meter for smart metering of electric power
networks if it is designed with an integrated circuit (IC) chip.
Grid 8 :Quantifying Changes in Building Electricity Use, With
Application to Demand Response
This
paper appears in: Smart Grid, IEEE Transactions on
Issue Date: Sept. 2011
We present methods
for analyzing commercial and industrial facility 15-min-interval electric load
data. These methods allow building managers to better understand their
facility's electricity consumption over time and to compare it to other
buildings, helping them to “ask the right questions” to discover opportunities
for demand response, energy efficiency, electricity waste elimination, and peak
load management. We primarily focus on demand response. Methods discussed
include graphical representations of electric load data, a regression-based
electricity load model that uses a time-of-week indicator variable and a
piecewise linear and continuous outdoor air temperature dependence and the
definition of various parameters that characterize facility electricity loads and
demand response behavior. In the future, these methods could be translated into
easy-to-use tools for building managers.
Grid 9 :SCUC With Hourly Demand Response Considering Intertemporal Load Characteristics
This
paper appears in: Smart Grid, IEEE Transactions on
Issue Date: Sept. 2011
In this
paper, the hourly demand response (DR) is incorporated into
security-constrained unit commitment (SCUC) for economic and security purposes.
SCUC considers fixed and responsive loads. Unlike fixed hourly loads,
responsive loads are modeled with their intertemporal
characteristics. The responsive loads linked to hourly market prices can be
curtailed or shifted to other operating hours. The study results show that DR
could shave the peak load, reduce the system operating cost, reduce fuel
consumptions and carbon footprints, and reduce the transmission congestion by
reshaping the hourly load profile. Numerical simulations in this paper exhibit
the effectiveness of the proposed approach.
Grid 10 :Towards Decentralization: A Topological
Investigation of the Medium and Low Voltage Grids
This
paper appears in: Smart Grid, IEEE Transactions on
Issue Date: Sept. 2011
The
traditional power grid has been designed in a hierarchical fashion, with energy pushed
from the large scale production factories towards the end users. With the
increasing availability of micro and medium scale generating facilities, the
situation is changing. Many end users can now produce energy and share it over
the power grid. Of course, end users need incentives to do so and want to act
in an open decentralized energy market. In the present work, we offer a novel
analysis of the medium and low voltage power grids of the North Netherlands
using statistical tools from the complex network analysis field. We use a
weighted model based on actual grid data and propose a set of statistical
measures to evaluate the adequacy of the current infrastructure for a
decentralized energy market. Further, we use the insight gained by the analysis
to propose parameters that tie the statistical topological measures to economic
factors that influence the attractiveness of participating in such
decentralized energy market, thus identifying the important topological
parameters to work on to facilitate such open decentralized markets.
Grid 11 :A Fault Steady State Component-Based Wide
Area Backup Protection Algorithm
This paper appears in: Smart
Grid, IEEE Transactions on
Issue Date: Sept. 2011
A novel
wide area backup protection algorithm to identify fault branch based on the
fault steady state component is proposed. Under normal conditions of the power
system, subsets of buses called protection correlation regions (PCRs) are
formed on the basis of the network topology and phasor
measurement unit (PMU) placement. After the fault occurs, by analyzing the fault
steady state component of differential current in each PCR, the fault
correlation region is confirmed and then a fault correlation factor (FCF), is
calculated in real time to locate the fault branch. The simulation results for
the 10-generator 39-bus system verify that this method is able to easily
identify fault branch with limited measurement points.
Grid 12 :Communication Requirement for Reliable and Secure State
Estimation and Control in Smart Grid
This paper appears in: Smart Grid, IEEE Transactions on
Issue Date: Sept. 2011
System state estimation and control are important issues to ensure the stability and reliability of the smart grid system. In this paper, the problem of how to securely estimate the system state and control the smart grid is studied. In the setup studied, the sensor(s) and the controller communicate with each other through a wireless channel subjected to monitoring by an eavesdropper. The channel capacity requirement that ensures negligible information leakage to the eavesdropper about the system state and control messages is studied from the information theoretic perspective. Two scenarios with single sensor or multiple sensors are studied. Numerical simulations are used to evaluate the capacity requirement in typical configurations of the smart grid.
Grid 13 :Optimal Sizing of Thyristor-Controlled
Impedance for Smart Grids With Multiple Configurations
This paper
appears in: Smart Grid, IEEE Transactions on
Issue Date: Sept. 2011
Smart
grids have become one of the important and challenging topics due to the
numerous benefits it can bring to the power system. In this context,
distributed generation (DG) is expected to play a significant role. The smart
grid can have multiple configurations depending on the smart grid operating
strategy and system conditions. In smart grids, DG could be operated either
grid connected or islanded. Such flexible and variable configuration results in
variable fault current levels which could impact the operation of the existing
protective devices on the distribution system. In this paper, it is proposed to
optimally size thyristor-controlled impedance (TCI)
of both inductive and capacitive type to manage the fault current levels under
different smart grid configurations. The salient benefit is to avoid damage and
delayed operation of protective devices due to the variability in fault
currents with synchronous-based DG. The problem is formulated as a nonlinear
programming (NLP) problem and the optimum size and type of the TCI is
determined using particle swarm optimization (PSO). Results show that by optimally
locating and sizing TCI, fault current levels under various smart grid
configurations can be managed and thus avoiding protective device coordination
failure and damage.
Grid 14 :Scheduling Power Consumption With Price Uncertainty
This paper appears in: Smart
Grid, IEEE Transactions on
Issue Date: Sept. 2011
The problem
of causally scheduling power consumption to minimize the expected cost at the
consumer side is considered. The price of electricity is assumed to be
time-varying. The scheduler has access to past and current prices, but only
statistical knowledge about future prices, which it uses to make an optimal
decision in each time period. The scheduling problem is naturally cast as a
Markov decision process. Algorithms to find decision thresholds for both noninterruptible and interruptible loads under a deadline
constraint are then developed. Numerical results suggest that incorporating the
statistical knowledge into the scheduling policies can result in significant
savings, especially for short tasks. It is demonstrated with real price data
from Commonwealth Edison that scheduling with mismatched modeling and online
parameter estimation can still provide significant economic advantages to
consumers.
Grid 15 :SmartPark
as a Virtual STATCOM
This
paper appears in: Smart Grid, IEEE Transactions on
Issue Date: Sept. 2011
Power electronic-based FACTS devices such as STATCOMs are sometimes essential for voltage support in transmission networks. They can also be used for continuous operation of doubly-fed induction generator-based wind turbines during faults. However, these devices are quite expensive and therefore cannot be used extensively. This paper explores the potential of a low-cost solution that utilizes the reactive power and voltage support capabilities of plug-in vehicles parked in charging stations (SmartParks) so that they can behave as virtual STATCOMs. For this solution, a 12-bus multimachine power system is considered wherein one of the conventional units is replaced by a 400 MW wind farm. Twelve SmartParks are developed and integrated into the test system. First, they are connected to a weak bus in the system and used in voltage control mode. Their performance is compared with a STATCOM of a similar rating. Next, the SmartParks are connected to the wind farm bus, and a coordinated reactive power control strategy is proposed to improve the fault-ride-through capability of the wind farm without exceeding the current limits of rotor and grid-side converters. The entire study is carried out in real time on a real-time digital simulator platform.
Gridv 16 :Parameter Exploration
in Science and Engineering Using Many-Task Computing
Robust scientific methods require the exploration of the parameter
space of a system (some of which can be run in
parallel on distributed resources), and may involve
complete state space exploration, experimental
design, or numerical optimization techniques. Many-Task Computing (MTC) provides a
framework for performing robust design, because it supports the execution of a
large number of otherwise independent processes. Further, scientific workflow
engines facilitate the specification and execution
of complex software pipelines, such as those found in
real science and engineering design problems. However, most existing
workflow engines do not support a wide range of experimentation techniques, nor
do they support a large number of independent tasks. In
this paper, we discuss Nimrod/K - a set of add in
components and a new run time machine for a general
workflow engine, Kepler. Nimrod/K provides an
execution architecture based on the tagged dataflow concepts, developed in 1980s for highly parallel machines. This is embodied in a new Kepler "Director”
that supports many-task computing by orchestrating execution of tasks on on clusters, Grids, and Clouds.
Further, Nimrod/K provides a set of "Actors” that facilitate the various
modes of parameter exploration
discussed above. We demonstrate the power of Nimrod/K to solve real problems in cardiac science.
Gridv 17:Collective Receiver-Initiated Multicast for Grid Applications
Grid applications often need to distribute large amounts of data efficiently from one cluster to multiple others (multicast). Existing sender-initiated methods arrange nodes in optimized tree structures, based on external network monitoring data. This dependence on monitoring data severely impacts both ease of deployment and adaptivity to dynamically changing network conditions. In this paper, we present Robber, a collective, receiver-initiated, high-throughput multicast approach inspired by the BitTorrent protocol. Unlike BitTorrent, Robber is specifically designed to maximize the throughput between multiple cluster computers. Nodes in the same cluster work together as a collective that tries to steal data from peer clusters. Instead of using potentially outdated monitoring data, Robber automatically adapts to the currently achievable bandwidth ratios. Within a collective, nodes automatically tune the amount of data they steal remotely to their relative performance. Our experimental evaluation compares Robber to BitTorrent, to Balanced Multicasting, and to its predecessor MOB. Balanced Multicasting optimizes multicast trees based on external monitoring data, while MOB uses collective, receiver-initiated multicast with static load balancing. We show that both Robber and MOB outperform BitTorrent. They are competitive with Balanced Multicasting as long as the network bandwidth remains stable, and outperform it by wide margins when bandwidth changes dynamically. In large environments and heterogeneous clusters, Robber outperforms MOB.