scholarly journals Investigation on the Impact of Degree of Hybridisation for a Fuel Cell Supercapacitor Hybrid Bus with a Fuel Cell Variation Strategy

Vehicles ◽  
2019 ◽  
Vol 2 (1) ◽  
pp. 1-17 ◽  
Author(s):  
Partridge ◽  
Wu ◽  
Bucknall
Keyword(s):  
Fuel Cell ◽  
Control Strategy ◽  
Power Output ◽  
Normal Operation ◽  
System Protection ◽  
Double Decker ◽  
Wide Range ◽  
Hybrid Bus ◽  
Cell Variation ◽  
The Impact

This paper presents the development of a control strategy for a fuel cell and supercapacitor hybrid power system for application in a city driving bus. This aims to utilise a stable fuel cell power output during normal operation whilst allowing variations to the power output based on the supercapacitor state-of-charge. This provides flexibility to the operation of the system, protection against over-charge and under-charge of the supercapacitor and gives flexibility to the sizing of the system components. The proposed control strategy has been evaluated using validated Simulink models against real-world operating data collected from a double-decker bus operating in London. It was demonstrated that the control strategy was capable of meeting the operating power demands of the bus and that a wide range of degrees of hybridisation are viable for achieving this. Comparison between the degree of hybridisation proposed in this study and those in operational fuel cell (FC) hybrid buses was carried out. It was found that the FC size requirement and FC variation can be significantly reduced through the use of the degree of hybridisation identified in this study.

scholarly journals Quadrature Voltage Compensation in the Isolated Multi-Modular Converter

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 529
Author(s):  
Cristian Verdugo ◽  
Jose Ignacio Candela ◽  
Pedro Rodriguez
Keyword(s):  
Control Strategy ◽  
Phase Voltage ◽  
Multilevel Converters ◽  
Photovoltaic Panels ◽  
Circulating Current ◽  
Three Phase ◽  
Voltage Compensation ◽  
Wide Range ◽  
Modular Converter ◽  
The Impact

Series connections of modules in cascaded multilevel converters are prone to power imbalances due to voltage differences on their DC side. When modules are connected to direct current (DC) sources, such as photovoltaic panels, the capability of withstanding power imbalances is crucial for generating the maximum power. In order to provide a possible solution for this requirement, this paper proposes a control strategy called Quadrature Voltage Compensation, which allows a wide range of power imbalances. The proposed control strategy regulates the power by introducing a circulating current between the arms and a phase angle in the output voltage. The impact of the circulating current and its effect on the phase voltage are studied. To highlight the features of the proposed strategy, an analytical model based on vector superposition is also described, demonstrating the strong capability of tolerating power differences. Finally, to validate the effectiveness of the Quadrature Voltage Compensation, simulation and experimental results are presented for a three-phase isolated multi-modular converter.

scholarly journals Development and Evaluation of a Degree of Hybridisation Identification Strategy for a Fuel Cell Supercapacitor Hybrid Bus

Energies ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 142 ◽  
Author(s):  
Wei Wu ◽  
Julius Partridge ◽  
Richard Bucknall
Keyword(s):  
Real World ◽  
Control Strategy ◽  
Electrical Energy ◽  
Clean Energy ◽  
General Strategy ◽  
Hybrid Propulsion ◽  
Double Decker ◽  
Hybrid Bus ◽  
Clean Energy Source ◽  
Performance Conditions

Fuel cells (FC) are a clean energy source that are capable of powering a vehicle’s electrical energy requirements whilst providing zero operating emissions. In this study, a full-scaled computer model FC/supercapacitor (SC) hybrid has been developed to investigate the performance of the hybrid propulsion system under real-world performance conditions. A control strategy focused on maintaining a constant FC output at a user-defined value has been developed and applied to the FC/SC hybrid model. Driving cycles collected from a practical double-decker bus have been utilised to evaluate the developed model. It has been demonstrated that the proposed control strategy is capable of maintaining a constant and stable FC output while meeting a real world dynamic load. Based on the obtained results, a general strategy to identify the degree of hybridisation between the FC and the SC in a FC hybrid system has been developed and demonstrated.

Machine Learning Methodologies for Prediction of Rhythm-Control Strategy in Patients Diagnosed with Atrial Fibrillation: Model Development and Comparison Study (Preprint)

2021 ◽  
Author(s):  
Rachel Soon-Yong Kim ◽  
Steve Simon ◽  
Brett Powers ◽  
Amneet Sandhu ◽  
Jose Sanchez ◽  
...  
Keyword(s):  
Machine Learning ◽  
Atrial Fibrillation ◽  
Control Strategy ◽  
Prediction Models ◽  
Rhythm Control ◽  
Machine Learning Algorithms ◽  
Support Tool ◽  
Wide Range ◽  
Complex Models ◽  
The Impact

BACKGROUND Identification of the appropriate rhythm management strategy for patients diagnosed with atrial fibrillation (AF) remains a major challenge for providers. While clinical trials have identified sub-groups of patients in whom a rate- or rhythm-control strategy might be indicated to improve outcomes, the wide range of presentations and risk factors among patients presenting with AF makes such approaches challenging. A strength of electronic health records (EHR) is the ability to build in logic to guide management decisions, such that the system can automatically identify patients in whom a rhythm-control strategy is more likely and promote efficient referrals to specialists. However, like any clinical decision-support tool, there is a balance between interpretability and accurate prediction. OBJECTIVE In this investigation, we sought to create an EHR-based prediction tool to guide patient referral to specialists for rhythm-control management by comparing different machine learning algorithms. METHODS We compared machine learning models of increasing complexity and using up to 50,845 variables to predict the rhythm-control strategy in 42,022 patients within the UC Health system at the time of AF diagnosis. Models were evaluated on their classification accuracy, defined by the F1 score and other metrics, and interpretability, captured by inspection of the relative importance of each predictor. RESULTS We found that age was by far the strongest single predictor of a rhythm-control strategy, but that greater accuracy could be achieved with more complex models incorporating neural networks and more predictors for each subject. We determined that the impact of better prediction models was notable primarily in the rate of inappropriate referrals for rhythm-control, in which more complex models provided an average of 20% fewer inappropriate referrals than simpler, more interpretable models. CONCLUSIONS We conclude that any healthcare system seeking to incorporate algorithms to guide rhythm management for patients with AF will need to address this trade-off between prediction accuracy and model interpretability.

A Mathematical Model and Performance Evaluation for a Single-Stage Grid-Connected Photovoltaic (PV) System

2008 ◽  
Vol 9 (6) ◽  
Author(s):  
Prajna Paramita Dash ◽  
Amirnaser Yazdani
Keyword(s):  
Mathematical Model ◽  
Control Strategy ◽  
Voltage Control ◽  
Current Control ◽  
Operating Conditions ◽  
Single Stage ◽  
Control Loop ◽  
Pv System ◽  
Wide Range ◽  
The Impact

This paper proposes a control strategy for important transients of a single-stage, three-phase, PV system that is connected to a distribution network. The proposed control strategy adopts an inner current-control loop and an outer DC-link voltage control loop. The current-control mechanism renders the PV system protected against external faults, enables control of the DC-link voltage and, therefore, controls/maximizes the PV system power output. The paper also proposes a feed-forward compensation strategy for the DC-link voltage control loop to mitigate the impact of the nonlinear characteristic of the PV array on the closed-loop stability, and to permit design and optimization of the DC-link voltage controller for a wide range of operating conditions. A mathematical model and a control design methodology are presented for the PV system, and it is shown that under the proposed control, the PV system fulfills the operational requirements of a grid-connected PV system. The effectiveness of the proposed control strategy and the most important transients of the PV system are evaluated through simulation studies conducted on a detailed switched model of the PV system in the PSCAD/EMTDC software environment.

Design and Construction of a Machine to Evaluate the Forces in Roller Chain Drives

1992 ◽  
Author(s):  
James C. Conwell ◽  
Glen E. Johnson ◽  
S. W. Peterson
Keyword(s):  
Experimental Investigation ◽  
Impact Force ◽  
Normal Operation ◽  
Test Machine ◽  
Chain Drive ◽  
Roller Chain ◽  
Wide Range ◽  
The Impact ◽  
Chain Drives ◽  
Design And Construction

Abstract In this article, a brief history of chain drives is presented, and the design and construction of a machine to investigate chain drive force phenomena is discussed. The new test machine allows the measurement of the impact force between a roller and the sprocket during “seating” and it can also be used to measure the forces that exist in the link sides plates during normal operation (including start-up and shut down conditions). Data can be obtained for a wide range of chain loads and speeds. Two companion papers (“Experimental Investigation of the Impact Force that Occurs When a Roller Seats on the Sprocket During Normal Operation of a Roller Chain Drive” and “Experimental Investigation of the Forces in a Link Side Plate During Normal Operation of a Roller Chain Drive”, both presented at this conference) describe experiments that have been completed with this test machine.

Experimental Investigation of the Forces in a Link Side Plate During Normal Operation of a Roller Chain Drive

1992 ◽  
Author(s):  
James C. Conwell ◽  
Glen E. Johnson ◽  
S. W. Peterson
Keyword(s):  
Experimental Investigation ◽  
Unit Length ◽  
Linear Chain ◽  
Normal Operation ◽  
Test Machine ◽  
Side Plate ◽  
Inertia Effects ◽  
Roller Chain ◽  
Wide Range ◽  
The Impact

Abstract The fluctuation in the tension of a chain link during normal operation is very likely the root cause of chain stretch and fatigue in roller chain drives. In this paper we present the results from a recent experimental investigation of this tension variation phenomenon. The experimental procedure is described, and data are presented for a wide range of initial tensions, transmitted loads, and chain speeds. At low speeds, the data give reasonable agreement with previously published theoretical models for quasi-static load distribution. However, at higher speeds (where inertia effects are more significant) the experimental results indicate that quasi-static models do not provide an adequate explanation. The differences are noted and discussed. An empirical equation for “tight side” chain tension is presented in terms of torque transmitted, sprocket pitch radius, mass per unit length of chain, and linear chain speed. This paper is accompanied by companion papers that describe the design and construction of the test machine and the measurement of the impact force as a roller seats on the sprocket.

scholarly journals Design of Bionic Buffering and Vibration Reduction Foot for Legged Robots

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Qian Cong ◽  
Xiaojie Shi ◽  
Ju Wang ◽  
Yu Xiong ◽  
Bo Su ◽  
...  
Keyword(s):  
Impact Energy ◽  
Vibration Reduction ◽  
Legged Robots ◽  
Normal Operation ◽  
Natural Vibration Frequency ◽  
Strong Impact ◽  
Legged Robot ◽  
Wide Range ◽  
Unique Shape ◽  
The Impact

When legged robots walk on rugged roads, they would suffer from strong impact from the ground. The impact would cause the legged robots to vibrate, which would affect their normal operation. Therefore, it is necessary to take measures to absorb impact energy and reduce vibration. As an important part of a goat’s foot, the hoof capsule can effectively buffer the impact from the ground in the goat’s running and jumping. The structure of the hoof capsules and its principle of buffering and vibration reduction were studied. Inspired by the unique shape and internal structure of the hoof capsules, a bionic foot was designed. Experimental results displayed that the bionic foot could effectively use friction to consume impact energy and ensured the stability of legged robot walking. In addition, the bionic foot had a lower natural vibration frequency, which was beneficial to a wide range of vibration reduction. This work brings a new solution to the legged robot to deal with the ground impact, which helps it adapt to a variety of complex terrain.

Effect of Sub-Freezing Temperature on a PEM Fuel Cell

2006 ◽  
Author(s):  
Q. G. Yan ◽  
H. Toghiani
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Cold Start ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Operating Conditions ◽  
Normal Operation ◽  
Subzero Temperatures ◽  
Wide Range ◽  
Backing Layer

The cold-start behavior and the effect of subzero temperatures on fuel cell performance were studied using a 25-cm2 PEMFC. The fuel cell system was housed in an environmental chamber that allowed the system to be subjected to temperatures ranging from sub-freezing to those encountered during normal operation. Fuel cell cold-start was investigated under a wide range of operating conditions. The cold-start measurements showed that the cell was capable of starting operation at −5 °C without irreversible performance loss when the cell was initially dry. The fuel cell was also able to operate at low environmental temperatures, down to −15 °C. However, irreversible performance losses were found if the cell cathode temperature fell below −5 °C during operation. Freezing of the water generated by fuel cell operation damaged fuel cell internal components. Several low temperature failure cases were investigated in PEM fuel cells that underwent sub-zero start and operation from −20 °C. Cell components were removed from the fuel cells and analyzed with scanning electron microscopy (SEM). Significant damage to the MEA and backing layer was observed in these components after operation below −5 °C. Catalyst layer delamination from both the membrane and the gas diffusion layer (GDL) was observed, as were cracks in the membrane, leading to hydrogen crossover. The membrane surface became rough and cracked and pinhole formation was observed in the membrane after operation at subzero temperatures. Some minor damage was observed to the backing layer coating Teflon and binder structure due to ice formation during operation.

An Investigation Into the Optothermal Behavior of a High Power Red Light Emitting Diode: Impact of an Optical Path

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Ahmet Mete Muslu ◽  
Burak Ozluk ◽  
Mehmet Arik
Keyword(s):  
Computational Models ◽  
Red Light ◽  
Monochromatic Light ◽  
Junction Temperature ◽  
Normal Operation ◽  
Imaging Method ◽  
Light Emitting ◽  
Wide Range ◽  
Red Led ◽  
The Impact

Abstract Monochromatic light emitting diodes (LEDs) are getting more attention day by day for a very wide range of applications such as general lighting, signage, automotive lighting, display, water purification, and skin imaging. While they are taking place in a large number of applications, thermal challenges associated with the operation of LEDs have become a significant issue to address since their performance is greatly affected by thermal conditions. Thus, this study focuses on identifying thermal, optical, and electrical characteristics of an AlGaInP-based red LED considering the impact of the LED dome on the chip performance. The junction temperature measurement results obtained with forward voltage change method were validated with thermal imaging method (TIM) and computational models. It was observed that the LED dome may critically affect the thermal, optical, and electrical behaviors of the LED chip. In fact, a 3.7% increase in junction temperature and a 6.1% drop in optical conversion efficiency were found at the normal operation of the red LED after the LED dome was removed. The results were also compared with a blue LED, and lower junction temperatures were measured for the red LED at each driving current. The difference in junction temperature became even more noticeable at higher driving currents. Results have shown a good agreement between three different methods with a maximum variation of 6.9%.

Using High Resolution Solar Measurement in PV Variability Studies

2012 ◽  
Author(s):  
Manajit Sengupta
Keyword(s):  
Solar Radiation ◽  
Solar Energy ◽  
Power Output ◽  
Temporal Variability ◽  
Solar Variability ◽  
Multiple Time ◽  
Variability Modeling ◽  
Wide Range ◽  
Temporal And Spatial ◽  
The Impact

Clouds, aerosols, water vapor and other atmospheric constituents influence solar energy reaching the earth’s surface. Each of these atmospheric constituents has it’s own inherent scale of temporal and spatial variability and they in turn influence the variability in the amount of solar radiation reaching the earth’s surface. This combined influence of the atmospheric constituents and their separate variability characteristics makes solar variability modeling a complicated task. Output from photovoltaic (PV) power plants is dependent on the amount of solar energy reaching the surface. Therefore variability in solar radiation results in variability in PV plant output. The issue of variability in PV plant output has become important in the last couple of years as utility scale PV plants go online and increase in size. Understanding variability in PV plant output requires an understanding of (a) the spatial and temporal variability of solar radiation; (b) the influence of this solar variability on PV plant output. The goal of this paper is to understand what temporal and spatial scales of variability in Global Horizontal Radiation (GHI) are important to a PV plants and what measurements are needed to be able to characterize them. As solar radiation measuring instruments are point receivers it is important to understand how those measurements translate to energy received over a larger spatial extent. Also of importance is the temporal nature of variability characterized not at a single point on the ground but over large spatial areas. In this research we use high temporal and spatial resolution measurements from multiple time synchronized solar radiation sensors to create solar radiation fields at various spatial and temporal scales using a wide range of interpolation techniques. These solar fields are then used to create plant power output for various size PV plants. As various interpolation schemes can produce different distributions we investigate the impact of interpolation schemes on GHI and power output distribution. While power output from PV plants is an important quantity the temporal variability of power is a matter of concern to utilities. In this paper we show how PV plant output varies across different time scales.

Sign in / Sign up

Export Citation Format

Share Document