Showing papers on "Electric power published in 2013"

Toward Reliable Power Electronics: Challenges, Design Tools, and Opportunities

Abstract: A new era of power electronics was created with the invention of the thyristor in 1957. Since then, the evolution of modern power electronics has witnessed its full potential and is quickly expanding in the applications of generation, transmission, distribution, and end-user consumption of electrical power. The performance of power electronic systems, especially in terms of efficiency and power density, has been continuously improved by the intensive research and advancements in circuit topologies, control schemes, semiconductors, passive components, digital signal processors, and system integration technologies.

Supercapacitors: Review of Materials and Fabrication Methods

Abstract: Supercapacitors are considered to be promising candidates for power devices in future generations. These devices are expected to find many future applications in hybrid electric vehicles an...

Global Energy Scenario and Impact of Power Electronics in 21st Century

Abstract: Power electronics technology has gained significant maturity after several decades of dynamic evolution of power semiconductor devices, converters, pulse width modulation (PWM) techniques, electrical machines, motor drives, advanced control, and simulation techniques. According to the estimate of the Electric Power Research Institute, roughly 70% of electrical energy in the USA now flows through power electronics, which will eventually grow to 100%. In the 21st century, we expect to see the tremendous impact of power electronics not only in global industrialization and general energy systems, but also in energy saving, renewable energy systems, and electric/hybrid vehicles. The resulting impact in mitigating climate change problems is expected to be enormous. This paper, in the beginning, will discuss the global energy scenario, climate change problems, and the methods of their mitigation. Then, it will discuss the impact of power electronics in energy saving, renewable energy systems, bulk energy storage, and electric/hybrid vehicles. Finally, it will review several example applications before coming to conclusion and future prognosis.

System, apparatus and method for supplying electric power, apparatus and method for receiving electric power, storage medium and program

Abstract: An electric power supply system includes an electric power reception apparatus and an electric power supply apparatus adapted to supply electric power to the electric power reception apparatus when the electric power reception apparatus is placed on the electric power supply apparatus. The electric power supply apparatus includes a plurality of electric power supply units adapted to supply electric power by electromagnetic induction to the electric power reception apparatus. A selection unit of the electric power supply apparatus selects, from the total plurality of electric power supply units, a plurality of electric power supply units whose location corresponds to a position where the electric power reception apparatus is placed, and a control unit controls the supply of electric power such that electric power is supplied to the electric power reception apparatus from the selected plurality of electric power supply units.

Monitoring and Optimization for Power Grids: A Signal Processing Perspective

Abstract: Although the North American power grid has been recognized as the most important engineering achievement of the 20th century, the modern power grid faces major challenges [87]. Increasingly complex interconnections even at the continent size render prevention of the rare yet catastrophic cascade failures a strenuous concern. Environmental incentives require carefully revisiting how electrical power is generated, transmitted, and consumed, with particular emphasis on the integration of renewable energy resources. Pervasive use of digital technology in grid operation demands resiliency against physical and cyberattacks on the power infrastructure. Enhancing grid efficiency without compromising stability and quality in the face of deregulation is imperative. Soliciting consumer participation and exploring new business opportunities facilitated by the intelligent grid infrastructure hold a great economic potential.

Handbook of electrical power system dynamics : modeling, stability, and control

Abstract: This book aims to provide insights on new trends in power systems operation and control and to present, in detail, analysis methods of the power system behavior (mainly its dynamics) as well as the mathematical models for the main components of power plants and the control systems implemented in dispatch centers. Particularly, evaluation methods for rotor angle stability and voltage stability as well as control mechanism of the frequency and voltage are described. Illustrative examples and graphical representations help readers across many disciplines acquire ample knowledge on the respective subjects.

A review of energy storage technologies for marine current energy systems

Abstract: Increasing concerns about the depletion of fossil resources and the issue of environment lead to a global need for producing more clean energy from renewable sources. Ocean is appreciated as a vast source of renewable energies. Considering marine renewable energies, it can be noticed that significant electrical power can be extracted from marine tidal currents. However, the power harnessed from marine tidal currents is highly fluctuant due to the swell effect and the periodicity of the tidal phenomenon. To improve the power quality and make the marine generation system more reliable, energy storage systems can play a crucial role. In this paper, an overview and the state of art of energy storage technologies are presented. Characteristics of various energy storage technologies are analyzed and compared for this particular application. The comparison shows that high-energy batteries like sodium-sulphur battery and flow battery are favorable for smoothing the long-period power fluctuation due to the tide phenomenon while supercapacitor and flywheel are more suitable for eliminating short-period power disturbances due to swell or turbulence phenomena. This means that hybrid storage technologies are needed for achieving optimal results in tidal marine current energy applications.

A comprehensive multi-criteria model to rank electric energy production technologies

Abstract: The purpose of this research was to develop a model for decision-makers to rank various renewable and non-renewable electricity production technologies according to multiple criteria. The model ranks electric power plants using wind, solar, geothermal, biomass, hydropower (i.e., renewable sources), nuclear, oil, natural gas and coal in terms of four comprehensive criteria clusters: financial, technical, environmental and socio-economic-political. The model was built using the Analytic Hierarchy Process (AHP) with empirical data from government and academic sources. The results indicate that wind, solar, hydropower and geothermal provide significantly more overall benefits than the rest even when the weights of the primary criteria clusters are adjusted during sensitivity analysis. The only non-renewable sources that appear in three of the 20 top rank positions are gas and oil, while the rest are populated with renewable energy technologies. These results have implications for policy development and for decision makers in the public and private sectors. One conclusion is that financial incentives for solar, wind, hydropower and geothermal are sound and should be expanded. Conversely, subsidies for non-renewable sources could be diminished. The work concludes with ideas for future research such as exploring a full range of sensitivity analyses to help determine an optimal mix of renewable and non-renewable technologies for an overall energy system. The scope of the model could also be expanded to include demand as well supply side factors.

The Next Generation of Electric Power Unit Commitment Models

Abstract: Keywords: ELECTRICITE ; METHODE MATHEMATIQUE ; ENERGIE : PRODUCTION Reference Record created on 2004-09-07, modified on 2016-08-08

Turbulent character of wind energy.

Abstract: Wind turbines generate electricity from turbulent wind. Large fluctuations, and, more importantly, frequent wind gusts cause a highly fluctuating electrical power feed into the grid. Such effects are the hallmark of high-frequency turbulence. Here we show evidence that it is the complex structure of turbulence that dominates the power output for one single wind turbine as well as for an entire wind farm. We illustrate the highly intermittent, peaked nature of wind power fed into the grid. Multifractal scaling is observed, as described initially by Kolmogorov's 1962 theory of turbulence. In parallel, we propose a stochastic model that converts wind speed signals into power output signals with appropriate multifractal statistics. As more and more wind turbines become integrated into our electric grids, a proper understanding of this intermittent power source must be worked out to ensure grid stability in future networks. Thus, our results stress the need for a profound understanding of the physics of turbulence and its impact on wind energy.

Regulated Charging of Plug-in Hybrid Electric Vehicles for Minimizing Load Variance in Household Smart Microgrid

Abstract: With the advent of the plug-in hybrid electric vehicles (PHEVs), the vehicle-to-grid (V2G) technology is attracting increasing attention recently. It is believed that the V2G option can aid to improve the efficiency and reliability of the power grid, as well as reduce overall cost and carbon emission. In this paper, the possibility of smoothing out the load variance in a household microgrid by regulating the charging patterns of family PHEVs is investigated. First, the mathematic model of the problem is built up. Then, the case study is conducted, which demonstrates that, by regulating the charging profiles of the PHEVs, the variance of load power can be dramatically reduced. Third, the energy losses and the subsidy mechanism are discussed. Finally, the impacts of the requested net charging quantities and the battery capacity of PHEVs on the performance of the regulated charging are investigated.

General Steady-State Analysis and Control Principle of Electric Springs With Active and Reactive Power Compensations

Abstract: This paper provides a general analysis on the steady-state behavior and control principles of a recently proposed concept of “electric springs” that can be integrated into electrical appliances to become a new generation of smart loads. The discussion here is focused on how different real and/or reactive load powers can be canceled or altered using the electric springs. Mathematical derivations supporting the theoretical framework of the concept are detailed in the paper. Experimental results validate the theoretical discussions and solutions proposed. It is demonstrated that the electric spring is capable of providing different types of power/voltage compensations to the load and the source.

Contactless Power Transfer System

Abstract: A system for powering components in a vehicle seat enables electronic components within the vehicle seat to receive power without wires connecting the seat to a vehicle body. The system includes a power transmitter that generates an electromagnetic field, and a power receiver located within the vehicle seat and the electromagnetic field. The power receiver is configured to generate electrical power from the electromagnetic field and deliver the power to at least one component in the vehicle seat.

An Agent-Based Approach to Virtual Power Plants of Wind Power Generators and Electric Vehicles

Abstract: Wind power is gaining in significance as an important renewable source of clean energy. However, due to their inherent uncertainty, wind generators are often unable to participate in the forward electricity markets like the more predictable and controllable conventional generators. Given this, virtual power plants (VPPs) are being advocated as a solution for increasing the reliability of such intermittent renewable sources. In this paper, we take this idea further by considering VPPs as coalitions of wind generators and electric vehicles, where wind generators seek to use electric vehicles (EVs) as a storage medium to overcome the vagaries of generation. Using electric vehicles in this manner has the advantage that, since the number of EVs is increasing rapidly, no initial investment in dedicated storage is needed. In more detail, we first formally model the VPP and then, through an operational model based on linear programming, we show how the supply to the Grid and storage in the EV batteries can be scheduled to increase the profit of the VPP, while also paying for the storage using a novel scheme. The feasibility of our approach is examined through a realistic case-study, using real wind power generation data, corresponding electricity market prices and electric vehicles' characteristics.

Modeling and Simulation of All-Electric Ships With Low-Voltage DC Hybrid Power Systems

Abstract: DC hybrid power systems are of interest for future low emission, fuel-efficient vessels. In spite of the advantages they offer onboard a ship, they result in a complex, interconnected system, which requires effective analysis tools to enable a full realization of the advantages. Modeling and simulation are essential tools to facilitate design, analysis, and optimization of the system. This paper reviews modeling of hybrid electric ship components including mechanical and electrical elements. Power electronic converters are modeled by nonlinear averaging methods to suit system-level studies. A unified model for bidirectional converters is proposed to avoid transitions between two separate models. A simulation platform using the derived models is developed for the system-level analysis of hybrid electric ships. Simulation results of power sharing among two diesel generators, a fuel cell module, and an energy storage system are presented for three modes of operation.

TV with integrated wireless power transmitter

Abstract: Disclosed here is a TV system with an integrated wireless power transmitter. The wireless power transmitter enables the TV system to provide a power source in the form of pockets of energy. A wireless power receiver may be coupled to the electrical devices to receive an electrical power source and transfer it to the electrical device. The receivers in the devices may capture energy from the pockets of energy formed by the wireless transmitter component in the TV system in order to power an electrical device.

Toward high-energy-density, high-efficiency, and moderate-temperature chip-scale thermophotovoltaics

Abstract: The challenging problem of ultra-high-energy-density, high-efficiency, and small-scale portable power generation is addressed here using a distinctive thermophotovoltaic energy conversion mechanism and chip-based system design, which we name the microthermophotovoltaic (μTPV) generator The approach is predicted to be capable of up to 32% efficient heat-to-electricity conversion within a millimeter-scale form factor Although considerable technological barriers need to be overcome to reach full performance, we have performed a robust experimental demonstration that validates the theoretical framework and the key system components Even with a much-simplified μTPV system design with theoretical efficiency prediction of 27%, we experimentally demonstrate 25% efficiency The μTPV experimental system that was built and tested comprises a silicon propane microcombustor, an integrated high-temperature photonic crystal selective thermal emitter, four 055-eV GaInAsSb thermophotovoltaic diodes, and an ultra-high-efficiency maximum power-point tracking power electronics converter The system was demonstrated to operate up to 800 °C (silicon microcombustor temperature) with an input thermal power of 137 W, generating 344 mW of electric power over a 1-cm2 area

Control strategies for high-power electric vehicles powered by hydrogen fuel cell, battery and supercapacitor

Abstract: Problems relating to oil supply, pollution, and green house effects justify the need for developing of new technologies for transportation as a replacement for the actual technology based on internal combustion engines (ICE) Fuel cells (FCs) are seen as the best future replacement for ICE in transportation applications because they operate more efficiently and with lower emissions This paper presents a comparative study performed in order to select the most suitable control strategy for high-power electric vehicles powered by FC, battery and supercapacitor (SC), in which each energy source uses a DC/DC converter to control the source power and adapt the output voltage to the common DC bus voltage, from where the vehicle loads are supplied Five different controls are described for this kind of hybrid vehicles: a basic control based on three operation modes of the hybrid vehicle depending on the state of charge (SOC) of the battery (operation mode control); a control strategy based on control loops connected in cascade, whose aim is to control the battery and SC SOC (cascade control); a control based on the technique of equivalent fuel consumption, called equivalent consumption minimization strategy (ECMS); and two based on control techniques very used nowadays, the first one of them is a fuzzy logic control and the second one is a predictive control These control strategies are tested and compared by applying them to a real urban street railway The simulation results reflect the optimal performance of the presented control strategies and allow selecting the best option for being used in this type of high-power electric vehicles

Electric Power Allocation in a Network of Fast Charging Stations

Abstract: In order to increase the penetration of electric vehicles, a network of fast charging stations that can provide drivers with a certain level of quality of service (QoS) is needed. However, given the strain that such a network can exert on the power grid, and the mobility of loads represented by electric vehicles, operating it efficiently is a challenging and complex problem. In this paper, we examine a network of charging stations equipped with an energy storage device and propose a scheme that allocates power to them from the grid, as well as routes customers. We examine three scenarios, gradually increasing their complexity. In the first one, all stations have identical charging capabilities and energy storage devices, draw constant power from the grid and no routing decisions of customers are considered. It represents the current state of affairs and serves as a baseline for evaluating the performance of the proposed scheme. In the second scenario, power to the stations is allocated in an optimal manner from the grid and in addition a certain percentage of customers can be routed to nearby stations. In the final scenario, optimal allocation of both power from the grid and customers to stations is considered. The three scenarios are evaluated using real traffic traces corresponding to weekday rush hour from a large metropolitan area in the US. The results indicate that the proposed scheme offers substantial improvements of performance compared to the current mode of operation; namely, more customers can be served with the same amount of power, thus enabling the station operators to increase their profitability. Further, the scheme provides guarantees to customers in terms of the probability of being blocked (and hence not served) by the closest charging station to their location. Overall, the paper addresses key issues related to the efficient operation, both from the perspective of the power grid and the drivers satisfaction, of a network of charging stations.

Portable self powered line mountable device for measuring and transmitting ambient temperature

Abstract: A device for attaching to an electric power line conductor includes an electrically conductive housing with an opening for accepting the power line conductor and configured to be grounded to the power line conductor. At least one magnetic core is configured to surround the power line conductor and power a power supply electronics module. An ambient temperature measuring assembly is mounted inside and near the bottom of the electrically conductive housing. The ambient temperature measuring assembly is thermally insulated from the housing for thermally separating the ambient temperature measuring assembly from the housing.

Energy harvesting using a PZT ceramic multilayer stack

Abstract: In this paper, the interdisciplinary energy harvesting issues on piezoelectric energy harvesting were investigated using a ‘33’ mode (mechanical stress and/or electric field are in parallel to the polarization direction) lead zirconate titanate multilayer piezoelectric stack (PZT-Stack). Key energy harvesting characteristics including the generated electrical energy/power in the PZT-Stack, the mechanical to electrical energy conversion efficiency, the power delivered from the PZT-Stack to a resistive load, the electrical charge/energy transferred from the PZT-Stack to a super-capacitor were systematically addressed. Theoretical models for power generation and delivery to a resistive load were proposed and experimentally affirmed. In a quasi-static regime, 70% generated electrical powers were delivered to matched resistive loads. A 35% mechanical to electrical energy conversion efficiency, which is more than 4 times higher than other reports, for the PZT-Stack had been obtained. The generated electrical power and power density were significantly higher than those from a similar weight and size cantilever-type piezoelectric harvester in both resonance and off-resonance modes. In addition, our study indicated that the capacitance and piezoelectric coefficient of the PZT-Stack were strongly dependent on the dynamic stress. (Some figures may appear in colour only in the online journal)

Wireless power supply receiver-transmitter device, wireless power supply receiver and wireless power supply transmitter

Abstract: There is provided a power supply receiver-transmitter device, a wireless power supply receiver, and a wireless power supply transmitter which allow wireless power supply transmission and wireless data transmission and reception, and improve the usability thereof. The wireless power supply receiver-transmitter device includes: a wireless power supply receiver (PR) including a power receiver unit (RU) and a first data transmitter/receiver unit (DRU); a wireless power supply transmitter (PT) including a power transmitter unit (TU); and a second data transmitter/receiver unit (DTU). The wireless power supply receiver (PR) wirelessly receives electric power transmitted from the wireless power supply transmitter (PT), and the first data transmitter/receiver unit (DRU) bidirectionally transmits and receives data to/from the second data transmitter/receiver units (DTU) through optical communications.

Reduction of Energy Storage Requirements in Future Smart Grid Using Electric Springs

Abstract: The electric spring is an emerging technology proven to be effective in i) stabilizing smart grid with substantial penetration of intermittent renewable energy sources and ii) enabling load demand to follow power generation. The subtle change from output voltage control to input voltage control of a reactive power controller offers the electric spring new features suitable for future smart grid applications. In this project, the effects of such subtle control change are highlighted, and the use of the electric springs in reducing energy storage requirements in power grid is theoretically proven and practically demonstrated in an experimental setup of a 90 kVA power grid. Unlike traditional Statcom and Static Var Compensation technologies, the electric spring offers not only reactive power compensation but also automatic power variation in non-critical loads. Such an advantageous feature enables non-critical loads with embedded electric springs to be adaptive to future power grid. Consequently, the load demand can follow power generation, and the energy buffer and therefore energy storage requirements can be reduced.

Review of PREPA Technical Requirements for Interconnecting Wind and Solar Generation

Abstract: The U.S. Department of Energy (DOE) and the National Renewable Energy Laboratory (NREL) have partnered with the Government of Puerto Rico to assist in addressing barriers to the deployment of energy efficiency and renewable energy in Puerto Rico. This document provides an overview of the minimum technical requirements (MTR) for interconnection of wind power and photovoltaic generation developed by the Puerto Rico Electric Power Authority (PREPA). Integrating a large amount of variable renewable generation such as wind and solar into an electrical grid presents several potential challenges for operating a power system, particularly with small island grids like the Puerto Rico electrical system. Establishing valid technical requirements for interconnection of variable renewable generation to the electric grid is an important step in overcoming such challenges. The interconnection requirements need to address several important aspects of renewable integration such as safety, impacts on power system reliability and performance, and costs. Being an isolated island system, PREPA does not fall under Federal Energy Regulatory Commission (FERC) jurisdiction, and therefore FERC interconnection standards are not required to be applied to generators in Puerto Rico. In this regard, PREPA has developed its own set of interconnection requirements with which all transmission-level wind and solar PV generators shall comply. In this report, NREL provides an impartial third-party review of PREPA’s MTRs, drawing comparisons with other similar requirements and best engineering practices. Over the course of the collaboration on the MTR review (2012-2013), PREPA revised the MTRs based on the draft review. As such, PREPA’s responses to the recommendations are also included in this report. The PREPA MTRs are anticipated to constantly evolve as the level of renewable penetration increases, modeling tools are improved, and experience with system performance increases. This review is intended to assist PREPA in this process. Acknowledgements The authors would like to acknowledge the substantial contributions to this report provided by staff at PREPA, the Governor’s Office, and the Puerto Rico Energy Affairs Administration (PREAA). NREL worked closely with staff from PREPA, PREAA, and the Governor’s Office throughout the technical review of PREPA’s MTRs to ensure accurate understanding of Puerto Rico’s electricity grid and the status of renewable energy integration. The authors would like to particularly thank Martin Perez, Luis Francis, Alvin Roman (PREPA) and Efrain O’Neill (Governor’s Energy Affairs Advisor) for their significant contributions and support of this effort, especially for reviewing the recommendations and providing a summary of PREPA’s responses. The authors would also like to thank Jennifer DeCesaro and Steve Lindenberg from DOE who sponsored this work, this effort could not have been completed without their support and involvement. This report is available at no cost from the National Renewable Energy Laboratory (NREL) iv at www.nrel.gov/publications. List of Abbreviations and Acronyms AGC automatic generation control DER distributed energy resources DFIG double-fed induction generator ERCOT Electric Reliability Council of Texas FESTIV Flexible Energy Scheduling Tool for Integration of Variable Generation FRT fault ride-through HECO Hawaiian Electric Company HVRT high-voltage ride-through Hz hertz IEC International Electrotechnical Commission IEEE Institute of Electrical Engineers & Electronics Engineers kV kilovolt LVRT low-voltage ride-through ms millisecond MTR minimum technical requirements MVA mega volt ampere MVAR mega volt ampere reactive MW megawatt NERC North American Electric Reliability Corporation PFR primary frequency response PSLF Positive Sequence Load Flow POI point of interconnection PQ power quality PPA power purchase agreement PRC protection and control PREPA Puerto Rico Electric Power Authority PSCAD power systems computer aided design PSS/E power system simulation for engineering PV photovoltaic RR ramp rate SCADA supervisory control and data acquisition SCR short circuit ratio STATCOM static synchronous compensator SVC static VAR compensator VAR volt ampere reactive VRS voltage regulation system WPP wind power plant WTG wind turbine generator ZVRT zero-voltage ride-through This report is available at no cost from the National Renewable Energy Laboratory (NREL) v at www.nrel.gov/publications. Table of

Electric power automation equipment

Abstract: The utility model discloses electric power automation equipment, which comprises an information processing module. The information processing module comprises a main processor and a wireless transceiver module. The wireless transceiver module and the main processor are in communication with each other based on the wireless communication protocol. The communication of the information processing module is realized also based on the wireless communication protocol. According to the technical scheme of the utility model, the automatic synchronization and the mutual communication among automation equipment are carried out in a wireless manner, so that the data transmission, including resource sharing, downloading and the like, can be realized. Therefore, the electric power automation equipment is convenient, efficient and safe to use.