Power Loss Distribution Research Articles

A pulsatile hemodynamic evaluation of the commercially available bifurcated Y-graft Fontan modification and comparison with the lateral tunnel and extracardiac conduits

ObjectiveFontan completion, resulting in a total cavopulmonary connection, is accomplished using a lateral tunnel, extracardiac conduit, or bifurcated Y-graft. The use of Y-grafts is hypothesized to provide symmetric hepatic blood flow distribution to the lungs, a factor related to pulmonary arteriovenous malformations. The present study evaluates the hemodynamic performance of the largest commercially available Y-graft cohort to date, highlights 6 representative cases, and compares commercially available Y-graft performance with lateral tunnel/extracardiac conduit connections. MethodsA total of 30 patients with commercially available Y-grafts and 30 patients with lateral tunnel/extracardiac conduits were analyzed. Total cavopulmonary connection anatomies and flow waveforms were reconstructed using cardiac magnetic resonance images and phase-contrast cardiac magnetic resonance. Computational fluid dynamic simulations were performed to quantify total cavopulmonary connection power loss, resistance, and hepatic flow distribution. Comparisons between graft types were investigated. ResultsTotal cavopulmonary connection resistance was significantly higher for Y-grafts. Hepatic flow distribution was similar overall but showed discrepancies at extreme values with more unbalanced flow in the Y-graft cohort. Power loss was more sensitive to left pulmonary artery stenosis in the Y-graft cohort. Prediction of Y-graft hepatic flow distribution is multifactorial. ConclusionsCommercially available Y-grafts do not inherently provide more balanced hepatic flow distribution than lateral tunnel/extracardiac conduit connections, which are more energetically favorable and less sensitive to pulmonary artery stenosis. Graft type should be considered on an individual basis because hemodynamic performance is based on a combination of factors, including pulmonary flow distribution, pulmonary artery stenosis, and superior vena cava positioning.

Distributed Renewable Generation and Storage System Sizing Based on Smart Dispatch of Microgrids

This paper considers the contribution of independent owners (IOs) operating within microgrids (MGs) toward green power generation in deregulated energy markets. An optimization scheme is introduced for sizing distributed renewable generation (DRG) and a distributed energy storage system (DESS) based on a novel energy management system (EMS) that accounts for demand response (DR), DESS dispatch and performance degradation, dynamic pricing environments, power distribution loss and irregular renewable generation. The proposed EMS utilizes an iterative Newton-Raphson linear programming algorithm that schedules resources in order to minimize the objective function, to deal with the complicated nonlinear nature of the problem and to enable efficient long-term assessments. The EMS is used to evaluate candidate solutions that are generated by a genetic algorithm (GA) to determine the optimal combination of DRG and DESS. A case study for IEEE 34-bus distribution MG in Okinawa, Japan, is used for testing the algorithm and analyzing the potential for IO/MG investments and their strategies.

Both transversal negative permeability and backward-wave propagation in X-Band waveguide with double-side SRR metamaterials

In this article X-band rectangular waveguides partially filled with the double-side single ring resonator (DSRR) array are investigated for miniaturization, stop-band, and multi-band filters applications. Several rectangular waveguides loaded with the DSRR array in 2–10 GHz frequency band have been studied and optimized. We observe both the transversal negative permeability presented above the cutoff frequency and the backward-wave located below the cutoff frequency with the DSRR array in X-band waveguide. Both simulation and measurement results of DSRR array are with good agreement. The DSRR array provides better performance of the transversal negative permeability and the backward-wave than the split-ring resonator array. The physical explanation of backward-wave is presented. The power loss distributions are clearly presented for the negative permeability attenuation and the backward-wave propagation. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:240–246, 2016.

Towards Integrating Distributed Energy Resources and Storage Devices in Smart Grid

Internet of Things (IoT) provides a generic infrastructure for different applications to integrate information communication techniques with physical components to achieve automatic data collection, transmission, exchange, and computation. The smart grid, as one of typical applications supported by IoT, denoted as a re-engineering and a modernization of the traditional power grid, aims to provide reliable, secure, and efficient energy transmission and distribution to consumers. How to effectively integrate distributed (renewable) energy resources and storage devices to satisfy the energy service requirements of users, while minimizing the power generation and transmission cost, remains a highly pressing challenge in the smart grid. To address this challenge and assess the effectiveness of integrating distributed energy resources and storage devices, in this paper we develop a theoretical framework to model and analyze three types of power grid systems: the power grid with only bulk energy generators, the power grid with distributed energy resources, and the power grid with both distributed energy resources and storage devices. Based on the metrics of the power cumulative cost and the service reliability to users, we formally model and analyze the impact of integrating distributed energy resources and storage devices in the power grid. We also use the concept of network calculus, which has been traditionally used for carrying out traffic engineering in computer networks, to derive the bounds of both power supply and user demand to achieve a high service reliability to users. Through an extensive performance evaluation, our data shows that integrating distributed energy resources conjointly with energy storage devices can reduce generation costs, smooth the curve of bulk power generation over time, reduce bulk power generation and power distribution losses, and provide a sustainable service reliability to users in the power grid.

Equalizing the Use of Voltage Sources in Multi-level Structures

In multi-level converters which employ several DC voltage sources to deliver an AC output waveform by voltage levels, the selection method and use time of each source has direct effect on the longevity of sources and consequently total system. It is obvious that equal entrance and exit of voltage sources and also time use of them, increase longevity of sources and total system. On the other hand, same condition of working in voltage sources, yield to same condition for switches and uniformed heat distribution produced due to power losses. In this paper the subject of equalizing the use of voltage sources in multi-level structures, especially in symmetrical CHB, would be discussed. For this purpose, switching tables of CHB is corrected and Simulation results on a seven level of this structure with both prevalent and proposed methods are presented. These results confirm performance of corrected switching table and shows improvement in proposed converter work and uniformity in power loss distribution created by switches.

Equalizing the Use of Voltage Sources in Multi-level Structures

In multi-level converters which employ several DC voltage sources to deliver an AC output waveform by voltage levels, the selection method and use time of each source has direct effect on the longevity of sources and consequently total system. It is obvious that equal entrance and exit of voltage sources and also time use of them, increase longevity of sources and total system. On the other hand, same condition of working in voltage sources, yield to same condition for switches and uniformed heat distribution produced due to power losses. In this paper the subject of equalizing the use of voltage sources in multi-level structures, especially in symmetrical CHB, would be discussed. For this purpose, switching tables of CHB is corrected and Simulation results on a seven level of this structure with both prevalent and proposed methods are presented. These results confirm performance of corrected switching table and shows improvement in proposed converter work and uniformity in power loss distribution created by switches.

Abstract 14364: Hemodynamic Evaluation of 30 Y-Graft Fontan Completions

Background: Fontan completion, resulting in a total cavopulmonary connection (TCPC), is accomplished using either a traditional baffle or bifurcated Y-graft. The use of Y-grafts was originally hypothesized to provide more even hepatic blood flow distribution to the lungs, a factor related to pulmonary arteriovenous malformations. This study evaluates the hemodynamic performance of the largest Y-graft cohort to date, compares those results with a traditional baffle, and highlights Y-graft cases that exhibit both favorable and poor performance. Methods: Thirty Y-graft and 30 traditional baffle Fontan patients were analyzed. TCPC anatomies and vessel flow waveforms were reconstructed using cardiac magnetic resonance (CMR) images and phase-contrast CMR. Computational fluid dynamic simulations were performed to quantify TCPC power loss, resistance, and hepatic flow distribution (HFD). Comparisons between graft types and subanalysis of favorable versus poor performing Y-grafts were investigated. Results: The TCPC resistance distribution, HFD distribution, and the effect of LPA stenosis on power loss for Y-grafts and traditional baffles are shown in Fig. 1A-1C. TCPC resistance was significantly lower in traditional baffle patients. HFD was similar overall, with median and range of 40 (1-77) and 51 (1-99) for the traditional baffle and Y-graft, but show a discrepancy at extreme values with more unbalanced flow in the Y-graft cohort. Power loss was more sensitive to LPA stenosis in the Y-graft cohort. Prediction of Y-graft HFD is multi-factorial and six representative cases are shown in Fig. 1D. Conclusions: Y-grafts do not inherently provide more balanced HFD than traditional baffles. Traditional baffles are more energetically favorable and less sensitive to PA stenosis. Graft type should be considered on an individual basis as hemodynamic performance is based on a combination of factors, including global flow distribution, PA stenosis and SVC positioning.

Power loss and load distribution models including frictional effects for spur and helical gears

Friction between meshing gear teeth are amongst the most influential power loss sources in a gearbox near nominal operating conditions. Speed, load and coefficient of friction are some of the most important factors regarding frictional losses in gears. The aim of this work is to introduce gear load sharing models for spur and helical gears taking into account elastic and frictional effects allowing to do more refined estimations of gear friction losses.

Optimal Power Flow in Islanded Microgrids Using a Simple Distributed Algorithm

In this paper, the problem of distributed power losses minimization in islanded distribution systems is dealt with. The problem is formulated in a very simple manner and a solution is reached after a few iterations. The considered distribution system, a microgrid, will not need large bandwidth communication channels, since only closeby nodes will exchange information. The correction of generated active powers is possible by means of the active power losses partition concept that attributes a portion of the overall power losses in each branch to each generator. The experimental part shows the first results of the proposed method on an islanded microgrid. Simulation results of the distributed algorithm are compared to a centralized Optimal Power Flow approach and very small errors can be observed.

A Mathematical Model for Minimizing Add-On Operational Cost in Electrical Power Systems Using Design of Experiments Approach

One of the key functions of the Distribution System Operators (DSOs) of<br />electrical power systems (EPS) is to minimize the transmission and<br />distribution power losses and consequently the operational cost. This<br />objective can be reached by operating the system in an optimal mode which is performed by adjusting control parameters such as on-load tap changer (OLTC) settings of transformers, generator excitation levels, and VAR compensators switching. The deviation from operation optimality will result in additional losses and additional operational cost of the power system. Reduction of the operational cost increases the power system efficiency and provides a significant reduction in total energy consumption. This paper proposes a mathematical model for minimizing the additional (add-on) costs based on Design of Experiments (DOE). The relation between add-on operational costs and OLTC settings is established by means of regression statistical analysis. The developed model is applied to a 20-bustest network. The regression curve fitting procedure requires simulation experiments which have been carried out by the DigSilent PowerFactory 13.2 Program for performing network power flow. The results show the effectiveness of the model. The research work raises the importance the power system operation management of the EPS where the Distribution System Operator can avoid the add-on operational costs by continuous correction to get an operation mode close to optimality.

A New PWM Strategy for Grid-Connected Half-Bridge Active NPC Converters With Losses Distribution Balancing Mechanism

Photovoltaic systems technological development is driven by the request for higher efficiency and safety. These concerns influence also the choice of the power converter stage. Several topologies have been proposed and many of them are available commercially. Among them, the neutral point clamped (NPC) and derived topologies offers high efficiency, low leakage current, and low EMI. However, one main disadvantage of the NPC inverter is given by an unequal distribution of the losses in the semiconductor devices, which leads to an unequal distribution of temperature that can affect lifetime. By using the active NPC (ANPC) topology, where the clamping diodes are replaced by bidirectional switches, the power losses distribution problem is alleviated. The modulation strategy is a key issue for losses distribution in this topology. In this paper, two known strategies are discussed and a new PWM strategy, namely the adjustable losses distribution is proposed for better losses distribution in the ANPC topology. Simulations and experimental results help in evaluating the modulation strategies.

An interleaved, FPGA-controlled, multi-phase and multi-switch synchronous boost converter for fuel cell applications

This work describes the practical implementation of an interleaved multi-phase, multi-switch boost converter for fuel cell applications. The paper aims to validate the concept of digitally-controlled Multi-Interleaving Boost Converter (MIBC) for fuel cell applications, from two-phase, four-legs per phase, synchronous boost converter, abbreviated as 2-4-MIBC. Compared with the Interleaved Boost Converter (IBC), MIBC exhibits interesting performance in terms of magnetics, input and output current ripple, part count and distributed power losses. A potential field of application is indeed medium and higher power fuel cell front-end converters, where minimizing input current ripple is significant but also redundancy and reliability are crucial. Actually, this approach covers all these aspects since provide module and device redundancy with real-time and flexible digital control reconfiguration. Relevant aspects related to design, modeling, simulation and experimental verification of 1 kW, FPGA-controlled, 2-4-MIBC are treated in this paper.

DSP-Based Interleaved Buck Power Factor Corrector With Adaptive Slope Compensation

This paper introduces the adaptive slope compensation method into the digital clamping current control at various input voltages to improve the power factor (PF) and the total harmonic distortion (THD) of the universal input. The controller conducts a phase-management mechanism for various input voltages and load conditions to raise the circuit conversion efficiency. The optimal switching timing for one- and two-phase operations can be determined from the power loss distribution. A digital signal processor chip TMS320F28035 is used to implement the digital platform. A 300-W laboratory prototype with a universal line voltage 80-V dc output voltage is designed and tested to verify the feasibility. The values of efficiency from light load (10% of rated power) to full load at 115- and 230-V inputs are greater than 95%. PF values from medium to full load are greater than 0.94. Input current harmonics also meet the norm of IEC 61000-3-2 Class D.

A Comprehensive Study of Improved Evolutionary Particle Swarm Optimization (IEPSO) for Network Reconfiguration with DGs Sizing Concurrently

This paper deals with the reconfiguration of the distribution network system to investigate the total power losses considering Distribution Generations (DGs) sizing concurrently. To overcome other limitations and enhance the solution performances, a new optimization approach called Improved Evolutionary Particle Swarm Optimization (IEPSO) is proposed. The primary aim of this study is to investigate the contribution of the proposed algorithms towards total power losses by considering the optimum DG size simultaneously. The proposed method is compared with the traditional Particle Swarm Optimization (PSO) and Improved Particle Swarm Optimization (IPSO) respectively. The amount of time that an algorithm spends in obtaining an alternative topological status for the system power loss reduction and distribution generation sizing is taken into consideration. In this context, the study is tested using IEEE 33 bus distribution system.

Automatic Meter Reading using Power Line Signaling and Voltage Zero-crossing Detection

In India, the electric power transmission and distribution loss is very high, about 7% in transmission and 26% in distribution. Though deployment of automated meter reading system will reduce losses, particularly in distribution, penetration of automated meter reading is low due to high costs involved. World over, the Two-Way Automatic Communications System (TWACS) is the most widely used power line communications technology offering two-way communication between substation and end users. The TWACS introduces disturbance on the power system voltage for short durations near zero-crossing to generate the outbound (from substation to end user) signal. To generate the inbound (from end user to substation) signal, short duration current pulses are introduced, near voltage zero-crossings. Information is generated as a sequential combination of voltage disturbances for the outbound signal and current pulses for the inbound signal. The current study proposes a low-cost modification of the TWACS to reduce voltage and current harmonics. The proposed system has been modelled and simulated using SIMULINK/SIMPOWER Systems. The simulation results show that there is a reduction in voltage harmonics from 0.84 to 0.17% and in current harmonics from 2.07 to 1.10%.

Tunable terahertz absorption in graphene-based metamaterial

One of the most important advantages of graphene is the capability of dynamically tuning its conductivity by means of chemical doping or gate voltage. Based on this property, we proposed a tunable graphene-based terahertz absorber composed of a periodically patterned graphene structure and a metal ground plane spaced by a thin SiO2 dielectric layer. Our calculated results show that a perfect absorption can be achieved by using a single layer of graphene-based metamaterial structure at a fixed Fermi energy level. Moreover, the calculated electric field and power loss distributions enable us to reveal the absorption mechanism of the designed absorber. More importantly, we found that the absorption peak can be dynamically controlled over a broadband frequency range by adjusting the gate voltage without re-optimizing or re-fabricating the physical structure. This work may provide a further step in the development of compact tunable devices, such as tunable sensors and absorbers, switches, and slow light devices.

Cost–benefit analysis for optimal distributed generation placement in distribution systems

This paper presents an optimisation method to determine optimal allocations of distributed generation (DGs) and capacitors based on maximisation of a profit/worth analysis approach. The optimal locations and sizes of DGs and capacitors have been determined by minimising the power distribution loss. This method considers various technical and economic factors such as line losses, sizes of DGs and capacitors at optimal locations, investment costs, operating costs and maintenance costs of DG and capacitor to achieve the objective for a predetermined number. The electricity market price of grid power has been considered to recover initial investment in a specified time period. The improvement in the voltage profile of the system has also been considered in this work. The particle swarm optimisation technique has been used to solve the optimal placement of DGs and capacitors to maximise the profit. The proposed technique is tested on 33-bus and 69-bus test systems.

Development of a metering system to evaluate power distribution losses

Development of a metering system to evaluate power distribution losses

운동오차 예측을 위한 공작기계 스핀들용 유도전동기의 발열량 해석

This paper deals with thermal characteristic analysis of induction motors for machine tool spindle for motion error prediction. Firstly, the inverse design of general induction motors for machine tool spindle has been performed by design principles. Characteristics considering VVVF inverter of induction motors were analyzed. Secondary, power loss and thermal characteristics of induction motors analyzed by equivalent thermal resistance model from Motor-CAD S/W. To develop a second-order fitted power-loss distribution model for the constant-torque operating range of the induction motor, we employed the design of experiment and response surface methodology techniques. Finally, the analysis results were experimentally verified, and the validity of the proposed analysis method was confirmed.

Study of Direct-Drive Permanent Magnet Synchronous Generators with Solid Rotor Back-Iron and Different Windings

Direct-drive permanent magnet (PM) synchronous generators (DDPMSGs) are gaining more and more attention and application for wind power. This paper presents a comprehensive performance comparison of an external rotor surface-mounted PM synchronous generator equipped with three commonly used winding types, i.e., integral-slot distributed winding (ISDW), fractional-slot concentrated winding (FSCW), and fractional-slot distributed winding. The tradeoff between torque and the power factor, loss distribution, current, torque, and PM demagnetization characteristics under a short-circuit fault and the steady temperature rise are investigated and compared using finite-element analyses. It is found that, generally, FSCW PM generators exhibit high rotor losses compared with ISDWs, which will lead to an overly high temperature rise. Measures such as segment PMs and the adoption of lamination steel in the rotor can reduce the rotor loss and greatly improve the machine efficiency. However, the temperature rise of FSCW machines is still higher than that of ISDW machines. The conclusion is intended to help choose the proper winding types.