Commercial Grid Research Articles

Long term experimental study on commercial grid connection for Micro-scale horizontal axis wind turbine

Long term experimental study on commercial grid connection for Micro-scale horizontal axis wind turbine

Techno-Economic Analysis of a Hybrid Grid-Connected/PV/Wind System in Pakistan

In view of the current energy crisis prevailing in Pakistan, renewable energy resources are considered as practical and economical alternatives. In this work, technical as well as economic aspects of hybrid photovoltaic (PV) and wind systems connected to commercial grid are investigated for selected locations of Pakistan. A pre-feasibility study of the renewable resources was done using NREL’s Geospatial Toolkit having a broad meteorological database and additionally, a database of various renewable energy system components from different manufacturers. The locations were selected on the basis of favorable environmental criteria based on meteorological data e.g. daily, monthly and annual profiles of solar irradiance, temperatures, wind speeds etc. The suggested hybrid system was simulated in NREL’s HOMER software over the system life span as guaranteed by the manufacturers. Performances and economic impacts of various components constituting the system in different locations were then analyzed to draw a conclusion with respect to the least calculated Net Present Cost (NPC). Finally, an optimum hybrid system with most appropriate components was suggested for the location that rendered least NPC. The consumer-end advantages of such systems over grid-alone system were also presented. The system was simulated for four different locations in Pakistan and was shown that it could input an adequate amount of energy into the main grid.

Performance of Different Types of DC – DC Converter with P & O Algorithm of MPPT

This comparative study analysis of dc-dc converter for MPPT controller with P and O algorithm of a grid connected system finds the better suitable converter which can give the output with maximum power from the PV module and can have reliability to connect it to the GRID. In this paper the performance of LLC, ZETA and SEPIC converters are designed and simulated then its results are compared to identify the best suitable converter for the grid connected PV with P and O algorithm of MPPT circuit. The performance analysis has been carried out by connecting these converters in the circuit which already simulated for connecting the PV output to the commercial grid. The comparative performance analysis is done at the stage of gird as well as in the stage of output of the converter too.

Nanostructured Carbon Materials for Li-S and Li-Se Batteries

Novel energy storage systems with high energy density and reduced cost has drawn significant attention due to the emerging storage application, such as commercial electronic devices, electrical vehicles, and grid storage systems. Conventional Li-ion batteries, however, are hard to meet the requirement for those applications in near future due to the theoretical energy density limit. Therefore, advanced batteries with different chemistry which could provide higher capacity and energy density are necessary for further development. Among many candidates, Lithium-sulfur battery (Li-S) has been recognized as one promising system due to its high gravimetric energy density and low material cost, which is superior to most of current Li-ion batteries. Besides sulfur, selenium (Se) has also been involved in the battery study, since it shares similar lithiation/delithiation mechanism to sulfur. In addition, although with lower gravimetric capacity than sulfur, the better electrical conductivity and less shuttling behavior make selenium parallel path of the sulfur system. Due to their dissolution nature of both Li-S and Li-Se systems, supporting materials which provide a robust framework with sufficient internal space and reactive sites, are critical for the chemistry. Although there were many candidates for the supporting material in Li-S and Li-Se batteries, such as metal oxides and graphene based materials, porous carbon materials are still dominant for a practical point of view. Relatively low cost, Industrial scale production and convenient handling make porous carbon materials superior to other supporting materials. Here we present a summary of our work on several porous carbon materials as the supporting material, which help enable high S/Se loading on both material level and electrode level, for the Li-S and Li-Se batteries. We will demonstrate the preparation, characterization and electrochemical performance of the carbon materials. The comparison of corresponding Li-S and Li-Se will be also described. Besides carbon materials, we will also discuss about our study on the influence of polymer binder and electrolyte on the optimized electrodes on both Li-S and Li-Se systems. Further discussions on the battery design and cell-level energy density estimation will be also addressed.

Characteristics of Compensation for Fluctuating Output Power of a Solar Power Generator in a Hybrid Energy Storage System Using a Bi2223 SMES Coil Cooled by Thermosiphon With Liquid Hydrogen

Due to global issue of energy shortage, alternative energy such as solar and wind energy has to be introduced to the commercial electricity grid. A hybrid energy storage system which is able to convert unstable alternative energy into constant electricity has been proposed. The hybrid energy storage system is composed of hydrogen system and SMES system. This research concerns on the issue of continuous operation of SMES system by introducing a threshold voltage range into the SMES control method. This control method was applied to an SMES coil in a 1-kW-class hybrid energy storage model system. Using the control method, we could restrain the temperature rise of the SMES coil. An experiment has been carried out to confirm the effectiveness of the control method in continuous operation of the hybrid energy storage system. The fluctuation output of a solar power generator was appropriately compensated by electrolyzer and SMES systems.

貯湯量に関する周期境界条件を考慮した家庭用PEFCコージェネレーションシステムの最適運用計画

This paper proposes a new operational planning method for residential PEFC (Polymer Electrolyte Fuel Cell) cogeneration system considering the periodical boundary conditions concerning hot water in storage tank. It can be easily expected that residential PEFC cogeneration system is likely to produce more hot water than needed, because heat efficiency of PEFC is higher than its electrical efficiency. In that case, the surplus hot water would be discarded, and it might deteriorate total operational cost. However, previous researches have not discussed and focused on how to deal with the surplus hot water, and when to discard it. Therefore, we introduce periodical boundary conditions concerning hot water amount in storage tank, and include the cost of disposal hot water as the penalty into our objective function in order to consider them in the operational planning. We simulate the operational planning in the conditions of 3 seasons by using 2 methods, which are proposed method considering periodical boundary constraints and conventional method of operational planning. The study system is configured of PEFC, commercial grid, storage tank, and auxiliary gas boiler. The simulation results show the efficacy of proposed method in many cases. In addition, the bird's-eye view figures composed of optimal solutions reveal some information about the way to decide the appropriate periodical boundary conditions.

The ATLAS Event Service: A new approach to event processing

The ATLAS Event Service (ES) implements a new fine grained approach to HEP event processing, designed to be agile and efficient in exploiting transient, short-lived resources such as HPC hole-filling, spot market commercial clouds, and volunteer computing. Input and output control and data flows, bookkeeping, monitoring, and data storage are all managed at the event level in an implementation capable of supporting ATLAS-scale distributed processing throughputs (about 4M CPU-hours/day). Input data flows utilize remote data repositories with no data locality or pre-staging requirements, minimizing the use of costly storage in favor of strongly leveraging powerful networks. Object stores provide a highly scalable means of remotely storing the quasi-continuous, fine grained outputs that give ES based applications a very light data footprint on a processing resource, and ensure negligible losses should the resource suddenly vanish. We will describe the motivations for the ES system, its unique features and capabilities, its architecture and the highly scalable tools and technologies employed in its implementation, and its applications in ATLAS processing on HPCs, commercial cloud resources, volunteer computing, and grid resources.Notice: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The publisher by accepting the manuscript for publication acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.

High Efficiency High-Step-up Single-ended DC-DC Converter with Small Output Voltage Ripple

Renewable energy resources such as wind and photovoltaic power generation systems demand a high step-up DC-DC converters to convert the low voltage to commercial grid voltage. However, the high step-up converter using a transformer has limitations of high voltage stresses of switches and diodes when the transformer winding ratio increases. Accordingly, conventional studies have been applied to series-connect multioutput converters such as forward-flyback and switched-capacitor flyback to reduce the transformer winding ratio. This paper proposes new single-ended converter topologies of an isolation type and a non-isolation type to improve power efficiency, cost-effectiveness, and output ripple. The first proposal is an isolation-type charge-pump switched-capacitor flyback converter that includes an extreme-ratio isolation switched-capacitor cell with a chargepump circuit. It reduces the transformer winding number and the output ripple, and further improves power efficiency without any cost increase. The next proposal is a non-isolation charge-pump switched-capacitor-flyback tapped-inductor boost converter, which adds a charge-pump-connected flyback circuit to the conventional switched-capacitor boost converter to improve the power efficiency and to reduce the efficiency degradation from the input variation. In this paper, the operation principle of the proposed scheme is presented with the experimental results of the 100 W DC-DC converter for verification.

Simple technique for high-throughput marking of distinguishable micro-areas for microscopy.

Today's (nano)-functional materials, usually exhibiting complex physical properties require local investigation with different microscopy techniques covering different physical aspects such as dipolar and magnetic structure. However, often these must be employed on the very same sample position to be able to truly correlate those different information and corresponding properties. This can be very challenging if not impossible especially when samples lack prominent features for orientation. Here, we present a simple but effective method to mark hundreds of approximately 15×15 μm sample areas at one time by using a commercial transmission electron microscopy grid as shadow mask in combination with thin-film deposition. Areas can be easily distinguished when using a reference or finder grid structure as shadow mask. We show that the method is suitable to combine many techniques such as light microscopy, scanning probe microscopy and scanning electron microscopy. Furthermore, we find that best results are achieved when depositing aluminium on a flat sample surface using electron-beam evaporation which ensures good line-of-sight deposition. This inexpensive high-throughput method has several advantageous over other marking techniques such as focused ion-beam processing especially when batch processing or marking of many areas is required. Nevertheless, the technique could be particularly valuable, when used in junction with, for example focused ion-beam sectioning to obtain a thin lamellar of a particular pre-selected area.

A Three Phase Based Four Switch Inverter for Renewable Energy Sources in Micro grid

Inverters designed using reduced active semiconductor devices can be of interest to the industry because of their lower cost and enhanced reliability linked to their less complex gating and control circuitries. In this paper a four switch three phase b-4 topology for the grid connected application in an effort to reduce the cost of the inverter is investigated. Admittedly, this topology warrants higher voltage ratings of the semiconductor devices used and the dc-link split capacitors used with respect to a conventional six-switch three-phase b-6 topology inverter for a specific set of grid voltages. In this paper, application of four power semiconductor switch based three phase inverter has been proposed for renewable energy based generalized three phase micro grid interconnection. The b-4 of three phase inverter topology is investigated to make the commercial micro grid system to be cost effective and hardware optimized. A simple sinusoidal pulse width modulation (SPWM) is used to control the switching of the four switches. Main advantage of this converter is that it needs only four switches. As a result the system is less costly and also the complexity in associated with gating and control circuitry is very much reduced

Cryogenic System for 80-kV DC HTS Cable in the KEPCO Power Grid

DC HTS cable has advantages in the absence of ac loss. Therefore, the Korea Electric Power Corporation (KEPCO) has started a project of operating and manufacturing technology for applying an 80-kV 500-MW 500-m-long dc HTS cable to the commercial power grid since 2011. LS Cable Ltd. has joined this project for designing and manufacturing an HTS power cable, and KEPCO has taken on cryogenic system and real power grid operation. The cryogenic system for an 80-kV dc HTS cable is composed mainly of Stirling-type cryocoolers. The Stirling cryocooler has been examined and verified by real grid operation in Icheon substation, and we therefore became assured of reliability for the cooling HTS cable system. We present the cryogenic system design, installation, and some results of preliminary tests in this paper.

CFD Simulation of Enhanced Oil Recovery Using Nanosilica/Supercritical CO<sub>2</sub>

In this study series of runs were done by a CFD technique in which the injected fluid is nanoparticles/supercritical CO2. Geometry of the porous medium was created with the commercial grid generation tool (Gambit software). Continuity, momentum and volume fraction equations were solved based on the finite volume method. The benefits of existing nanoparticles in the gas injection process have been investigated. The numerical results show that addition of nanosilica into the supercritical CO2improves the oil recovery. It was also found that by increasing the nanoparticles concentration from 1 Vol. % to 2 Vol. %, the oil recovery factor increases about 5%. In addition, obtained results confirmed that by injecting the nanofluid fingers are reduced. The displacing fluid containing nanoparticles is more efficient than the supercritical CO2in sweeping the in-situ oil.

PDM Control Method for a Matrix Converter Converting Several‐Hundred‐kHz Single‐Phase Input to Commercial Frequency Three‐Phase Output

SUMMARYThis paper discusses pulse density modulation (PDM) control methods for a single‐phase to three‐phase matrix converter (MC) in high‐frequency applications. The proposed circuit is used as an interface converter for a wireless power transfer system. This converter can input a frequency of several hundred kilohertz and output a low frequency, that is, 50 Hz or 60 Hz, for a commercial power grid. The proposed circuit implements zero voltage switching (ZVS) operation by using PDM control methods and obtains high efficiency. In this paper, two PDM control strategies are compared: delta–sigma conversion and the PDM pattern generation method based on space vector modulation (SVM), which is proposed here. Also, the experimental results obtained with the proposed system will be presented and discussed. The total harmonic distortions (THDs) of the output voltage with delta–sigma conversion and the PDM pattern generation method based on SVM are found to be 5.96% and 2.15%, respectively. In addition, the maximum efficiencies with delta–sigma conversion and the PDM control based on SVM are 93.4% and 97.3%, respectively. From the results, the validity of the PDM control based on SVM has been confirmed for improvement of the output waveforms and reduction of the switching loss.

複数家庭で構成される電力システムの蓄電池を用いた出力平滑化制御

This paper addresses output smoothing control of an electric power system with multiple homes. The notion of home is a unit of small-scale power system closed to consumers. A home consists of local renewable-based energy source, energy storage, load, power conversion circuit, and control system. Output smoothing control aims to regulate the output power of a single home or coupled multiple homes to the outside of it and is expected to reduce the influence of fluctuating renewable sources to the outside, e.g. a commercial distribution grid. In this paper, we propose a batterybased algorithm for the output smoothing control and demonstrate its effectiveness in a practical,residential power system with two homes. In addition to the practical demonstration, by deriving a mathematical model for dynamics of active power flow in the controlled system and analyzing the model numerically and theoretically, we provide a guideline of tuning the feedback gain of the algorithm for a desired control response.

Commercial grid scaling of Energy Bags for underwater compressed air energy storage

Large-scale ability to store surplus energy for use during periods of high demand is a formidable asset in reducing the energy cost, improving electric grid reliability and addressing climate change. An Energy Bag is a fabric balloon-like vessel anchored to a sea- or lakebed for the purpose of storing surplus energy in the form of compressed air. This mode of energy storage is attractive because the passive pressure force of the deep-water environment takes on the significant role of pressure vessel structure to maintain pressurization of the air stored within the Energy Bag. Upon further investigation, it becomes evident that particular attention must be given to the storage volume and pressure required to satisfy requirements economically for commercial grid-scale development of this novel technology. This paper provides an introduction to the benefits and prerequisites pertaining to commercial scale energy storage capacity as related to Energy Bag structure, volume and deployment depth.

Short-channel functional near-infrared spectroscopy regressions improve when source-detector separation is reduced

In functional near-infrared spectroscopy (fNIRS) of human cerebral hemodynamics, dedicated surface-sensitive recording channels are useful for regressing out background hemodynamics and isolating activation-specific responses. A wide variety of source-detector separations have been utilized for this purpose. Here, we report a direct comparison of regression performance between two extremes of the reported range, 13 and 6mm. Measurements of visual stimulation response (flickering radial checkerboard) were obtained from nine adults using a standard commercial source-detector grid with 13-mm diagonals, into which three extra detector fibers were placed to provide 6-mm channels at certain locations. When the NIRS recordings (17 total trials) were processed, the contrast-to-noise ratio was significantly higher with 6-mm regression channels than with 13mm. The advantage could be due in part to the undesired sensing of brain activity by the 13-mm channels. We suggest that shorter distances be considered for optimal removal of superficial hemodynamics in NIRS signals from the adult brain.

High Fill-Factor Substrate-Based Wire-Grid Polarizers With High Extinction Ratios

Low-cost, substrate-based, millimeter-wave-to-THz wire-grid polarizers have been fabricated on crystalline-quartz substrates using planar processing techniques. The polarizers achieve high extinction ratios (at least 60 dB) with a single layer, while maintaining low insertion loss (a few decibels) by taking advantage of previously under-utilized “spoof” surface-plasmon effects. Full-wave finite-element simulations done with High Frequency Structure Simulator and experiments both show that metal fill-factors upwards of 90% greatly improve polarizer extinction ratio. The extinction ratio of high fill-factor polarizers exceeds that of a commercial free-standing wire grid by up to 20 dB at normal incidence.

MRI distortion: considerations for MRI based radiotherapy treatment planning

Distortion in magnetic resonance images needs to be taken into account for the purposes of radiotherapy treatment planning (RTP). A commercial MRI grid phantom was scanned on four different MRI scanners with multiple sequences to assess variations in the geometric distortion. The distortions present across the field of view were then determined. The effect of varying bandwidth on image distortion and signal to noise was also investigated. Distortion maps were created and these were compared to the location of patient anatomy within the scanner bore to estimate the magnitude and distribution of distortions located within specific clinical regions. Distortion magnitude and patterns varied between MRI sequence protocols and scanners. The magnitude of the distortions increased with increasing distance from the isocentre of the scanner within a 2D imaging plane. Average distortion across the phantom generally remained below 2.0mm, although towards the edge of the phantom for a turbo spin echo sequence, the distortion increased to a maximum value of 4.1mm. Application of correction algorithms supplied by each vendor reduced but did not completely remove distortions. Increasing the bandwidth of the acquisition sequence decreased the amount of distortion at the expense of a reduction in signal-to-noise ratio of 13.5 across measured bandwidths. Imaging protocol parameters including bandwidth, slice thickness and phase encoding direction, should be noted for distortion investigations in RTP since each can influence the distortion. The magnitude of distortion varies across different clinical sites.

PDM Control Method for a Matrix Converter Converting Several-Hundred-kHz Single-Phase Input to Commercial Frequency Three-Phase Output

This paper discusses pulse density modulation (PDM) control methods for a single-phase to three-phase matrix converter (MC) in high-frequency applications. The proposed circuit is used as an interface converter for a wireless power transfer system. This converter can input a frequency of several hundred kilohertz and output a low frequency, i.e., 50Hz or 60Hz, for a commercial power grid. The proposed circuit implements a zero voltage switching (ZVS) operation by using PDM control methods and obtains high efficiency. In this paper, two PDM control strategies are compared: delta-sigma conversion and the PDM pattern generation method based on space vector modulation (SVM), which is proposed here. Also, the experimental results obtained with the proposed system will be presented and discussed. The total harmonic distortions (THDs) of the output voltage with delta-sigma conversion and the PDM pattern generation method based on SVM are found to be 5.96% and 2.15%, respectively. In addition, the maximum efficiencies with delta-sigma conversion and the PDM control based on SVM are 93.4% and 97.3%, respectively. From the results, the validity of the PDM control based on SVM has been confirmed for improvement of the output waveforms and reduction of the switching loss.

A Two-Stage Wind Grid Inverter with Boost Converter

At present, the conversion efficiency of commercial small wind grid inverter is low, and, in case of low wind speed, the wind energy cannot be used efficiently. In order to resolve this problem, it is necessary to improve the topological structure and control strategy, and design a new small wind grid inverter. In this paper, we apply a two-voltage stage topology with boost converter. The boost circuit is to achieve the maximum power output of the wind energy by the segmented regulation, while the improved inverter topology realizes the overall system function with the former stage circuit. The experimental results show that the new wind grid inverter has superior performance in the low wind speed, and has the high quality energy output. This research has an important practical significance to improve the utilization of renewable energy.