EV Charging in Case of Limited Power Resource Rasolonjanahary, Manan’Iarivo Louis; Bingham, Chris; Schofield, Nigel ...
Actuators,
12/2021, Letnik:
10, Številka:
12
Journal Article
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In the case of the widespread adoption of electric vehicles (EV), it is well known that their use and charging could affect the network distribution system, with possible repercussions including line ...overload and transformer saturation. In consequence, during periods of peak energy demand, the number of EVs that can be simultaneously charged, or their individual power consumption, should be controlled, particularly if the production of energy relies solely on renewable sources. This requires the adoption of adaptive and/or intelligent charging strategies. This paper focuses on public charging stations and proposes methods of attribution of charging priority based on the level of charge required and premiums. The proposed solution is based on model predictive control (MPC), which maintains total current/power within limits (which can change with time) and imparts real-time priority charge scheduling of multiple charging bays. The priority is defined in the diagonal entry of the quadratic form matrix of the cost function. In all simulations, the order of EV charging operation matched the attributed priorities for the cases of ten cars within the available power. If two or more EVs possess similar or equal diagonal entry values, then the car with the smallest battery capacitance starts to charge its battery first. The method is also shown to readily allow participation in Demand Side Response (DSR) schemes by reducing the current temporarily during the charging operation.
This paper extends traditional Gaussian mixture model (GMM) techniques to provide recognition of operational states and detection of emerging faults for industrial systems. A variational Bayesian ...method allows a GMM to cluster with its mixture components to facilitate the extraction of steady-state operational behaviour; this is recognised as being a primary factor in reducing the susceptibility of alternative prognostic/diagnostic techniques, which would initiate false-alarms resulting from control set-point and load changes. Furthermore, a GMM with an outlier component is discussed and applied for direct novelty/fault detection. An advantage of the variational Bayesian method over traditional predefined thresholds is the extraction of steady-state data during both full- and part-load cases, and a primary advantage of the GMM with an outlier component is its applicability for novelty detection when there is a lack of prior knowledge of fault patterns. Results obtained from the real-time measurements on the operational industrial gas turbines have shown that the proposed technique provides integrated preprocessing, benchmarking, and novelty/fault detection methodology.
Strain Sensing with Metamaterial Composites Everitt, Henry O.; Tyler, Talmage; Caraway, Bill D. ...
Advanced optical materials,
05/2019, Letnik:
7, Številka:
9
Journal Article
Mapping strain fields in visually opaque structural composites—for which failure is often sudden, irreparable, and even catastrophic—requires techniques to locate and record regions of stress, ...fatigue, and incipient failure. Many composite materials are transparent in the terahertz spectral region, but their strain history is often too subtle to recover. Here, terahertz metamaterials with strain‐severable junctions are introduced that can identify structurally compromised regions of composite materials. Specifically, multilayer arrays of aluminum meta‐atoms are designed and fabricated as strip dipole antennas with a terahertz frequency resonance and a strong response to cross‐polarized radiation that disappears when local stress irreversibly breaks their bowtie‐shaped junction. By spatially mapping the local polarimetric response of this metamaterial as a function of global strain, the regions of local stress extrema experienced by a visually opaque material may be visualized. This proof‐of‐concept demonstration heralds the opportunity for embedding metamaterial laminates within composites to record and recover their strain‐dependent history of fatigue.
A new concept for mapping strain fields in composite materials is introduced, using a specially tailored metamaterial composed of multilayer arrays of severable strip dipole antennas. Because their terahertz resonance and strong response to cross‐polarized radiation disappears when local stress irreversibly breaks the bowtie junction, the occurrence of local stress above a predetermined threshold may be permanently recorded and recovered.
The UK National Grid has placed increased emphasis on the development of Demand Side Response (DSR) tariff mechanisms to manage load at peak times. Refrigeration systems, along with HVAC, are ...estimated to consume 14% of the UK’s electricity and could have a significant role for DSR application. However, characterized by relatively low individual electrical loads and massive asset numbers, multiple low power refrigerators need aggregation for inclusion in these tariffs. In this paper, the impact of the Demand Side Response (DSR) control mechanisms on food retailing refrigeration systems is investigated. The experiments are conducted in a test-rig built to resemble a typical small supermarket store. The paper demonstrates how the temperature and pressure profiles of the system, the active power and the drawn current of the compressors are affected following a rapid shut down and subsequent return to normal operation as a response to a DSR event. Moreover, risks and challenges associated with primary and secondary Firm Frequency Response (FFR) mechanisms, where the load is rapidly shed at high speed in response to changes in grid frequency, is considered. For instance, measurements are included that show a significant increase in peak inrush currents of approx. 30% when the system returns to normal operation at the end of a DSR event. Consideration of how high inrush currents after a DSR event can produce voltage fluctuations of the supply and we assess risks to the local power supply system.
The paper proposes a new, robust cluster-based classification technique for Novelty Identification in sensor networks that possess a high degree of correlation among data streams. During normal ...operation, a uniform cluster across objects (sensors) is generated that indicates the absence of novelties. Conversely, in presence of novelty, the associated sensor is clustered distinctly from the remaining sensors, thereby isolating the data stream which exhibits the novelty. It is shown how small perturbations (stemming from noise, for instance) can affect the performance of traditional clustering methods, and that the proposed variant exhibits a robustness to such influences. Moreover, the proposed method is compared with a recently reported technique, and shown that it performs 365% faster computationally. To provide an application case study, the technique is used to identify emerging fault modes in a sensor network on a sub-15MW industrial gas turbine in presence of other abrupt, but normal changes that visually might otherwise be interpreted as malfunctions.
The paper considers certain impedimental issues related to the use of magnetic gearbox and magnetic coupling technologies in high performance servo control systems. A prototype magnetic coupling is ...used as a basis for demonstrating that the underlying torque transfer characteristic is significantly nonlinear when transmitted torque approaches the maximum designed pull-out torque of the device. It is shown that linear controllers for speed control proportional plus integral （PI） and position control proportional plus derivative （PD） result in acceptable performance provided the magnetic coupling operates below 80 % of designed pull-out torque. To fully compensate for the inherent nonlinearity of the torque transfer characteristic, feedback linearizing control laws and state transformations are derived resulting in exactly linear input-output characteristic for position and speed control of magnetically-geared drive-trains. With the addition of state feedback, the closed-loop dynamics for both position and speed control of a magnetically-geared drive-train can be designed to satisfy the integral of time multiplied by absolute error （ITAE） optimized linear response for a step input. Outstanding results are demonstrated through simulation and experimental real-time implementation on a demonstrator magnetically-geared drive-train.
The paper presents a methodology to improve the operating robustness of low-cost magnetic drive-train (MDT) systems in which load-side sensing is not a preferred option for addressing pole-slipping ...and variable torsional stiffness issues. Firstly, through dynamically analysing the relative displacement angle between both sides of the MDT (resulting from the developed electromagnetic- and load-torque), the paper offers an operating criteria using the inertia ratio, electromagnetic- and load-torque excitations to prevent the MDT from pole-slipping. Subsequently, the relationship between controller parameters and dominant/resonant poles of closed-loop MDT control system, is discussed. It is shown that controller parameters for MDTs to accommodate a wide range of torsional stiffness variations can be determined from natural frequencies that are bounded by operating constraints. Using the presented principles, desired performance with respect to speed reference tracking and load-torque disturbance accommodation can be achieved by simply determining the natural frequency of the dominant poles. Simulation studies and experimental measurements on a custom MDT test facility are used to underpin the efficacy of the proposed analysis and design techniques.
A key challenge for engineers and scientists over the coming decades is to develop and deploy power plants with sufficient capacity and flexibility to meet the growing demand for energy (mainly ...electrical) whilst simultaneously reducing emissions (primarily greenhouse gases). With fusion-based power plants not currently being considered viable for large-scale deployment for at least 40 years, other technologies must to be considered. Renewable and high efficiency combined gas-fired plants, along with nuclear solutions, are regarded as the most suitable candidates, with Small Modular Reactors (SMRs) developing as a favoured choice. However, two main impediments to the current deployment of SMRs exist: (1) safety concerns, particularly following the Fukushima accident, and (2) their economic models, with high capital costs only being available through a limited number of investors. The goal of this paper is to provide a review and a holistic assessment of this class of nuclear reactor, with specific focus on the most common technology: the Light Water Reactor (LWR). In particular, the paper provides a state-of-the-art assessment of their life cycle, along with a comparison of their relative merits with other base-load technologies. It is shown that SMRs are a suitable choice when the power to be installed is in the range 1–3GWe and the social aspects of the investment, such as the creation of new employment positions, is a goal of policy makers. The paper thereby provides governments and stakeholders with key economic and social boundaries for the viable deployment of SMRs.
•There is a growing interest towards Small Modular Reactors (SMR).•This paper reviews the economics, financial and strategic aspects of SMR.•For several SMR the diseconomy of scale is compensated by the economy of multiples.•SMR can be an economically competitive technology mainly in the 1–3GWe Market.•SMR are an attractive technology for policy maker due to the higher local content.
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Urban built form and density are crucial parameters for the optimization of building energy performance. However, a cohesive framework which correlates building energy with urban ...built form and density is lacking, with no unified agreement on the concept of urban density. This study establishes the subtle interrelationships between urban built forms, density and building energy performance using two density indicators, specifically, site coverage and plot ratio. This paper initially considers geometrical variables of four customary urban built forms to investigate their relationship with the density indicators. Energy analyses are performed on the geometrical models representing residential buildings using the City of London as an example of a temperate climate. Annual building energy demands of pavilion, terrace, court and tunnel-court forms are calculated. The findings are used to produce a heat map of energy intensity on the Form Signature graphs. Results show that high-rise buildings with greater plan depths achieve higher energy efficiency. Moreover, it is shown that greater cut-off angles correspond to higher energy demands under temperate climatic conditions. An energy indicator, termed Energy Equity is introduced which represents the ratio between PV energy generation installed on roofs with respect to the total energy demand of the building. Further analyses show that by considering energy demand and PV energy generation simultaneously, low-rise buildings with greater plan depths provide improved energy performance. A comparative analysis of the energy performance of different built forms with similar geometric parameters demonstrates that the tunnel-court and the pavilion built forms provide the best and worst energy performance, respectively. However, when constraining density whilst changing other geometric parameters, this converse is true. Finally, the study illustrates that the same density for the same built form can be achieved by different combinations of geometric parameters that certainly affects energy performance of buildings. Graphic display of the analysis results provide urban planning guidelines that represent the database of major findings of this study. It can be used by designers, planners and architects to identify the most energy-efficient built form and density for promoting more sustainable cities.
This article presents a high performance and low-cost design methodology for the servo control of magnetic drive-trains (MDTs) operating in direct drive mode. For the first time, this article ...considers using sensitivity peaks to analyze the robustness and stability of MDT control systems. Initially, through analysis of a dynamic model, the key spring characteristic parameters with respect to operating points, are developed. It is also shown that a wider dynamic performance envelope can be achieved by linearizing the MDT model at around 60<inline-formula><tex-math notation="LaTeX">\%</tex-math></inline-formula>-80<inline-formula><tex-math notation="LaTeX">\%</tex-math></inline-formula> of the maximum coupling torque, as opposed to traditional linearization under zero torque conditions. Subsequently, this article exploits the spring characteristics for a design methodology based on the <inline-formula><tex-math notation="LaTeX">\text{H}_\infty</tex-math></inline-formula> mixed sensitivity approach to determine suitable control parameters. Following this, the maximum exogenous load-torque disturbance and speed reference that will not induce pole-slipping can be determined. Finally, preferential position reference profiles and optimal gains for position controllers are given to prevent demand-induced speed oscillations. The proposed methodologies are validated through simulation and experimental studies.
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