Big data and IoT-based applications in smart environments: A systematic review

This paper reviews big data and Internet of Things (IoT)-based applications in smart environments. The aim is to identify key areas of application, current trends, data architectures, and ongoing challenges in these fields. To the best of our knowledge, this is a first systematic review of its kind, that reviews academic documents published in peer-reviewed venues from 2011 to 2019, based on a four-step selection process of identification, screening, eligibility, and inclusion for the selection process. In order to examine these documents, a systematic review was conducted and six main research questions were answered. The results indicate that the integration of big data and IoT technologies creates exciting opportunities for real-world smart environment applications for monitoring, protection, and improvement of natural resources. The fields that have been investigated in this survey include smart environment monitoring, smart farming/agriculture, smart metering, and smart disaster alerts. We conclude by summarizing the methods most commonly used in big data and IoT, which we posit to serve as a starting point for future multi-disciplinary research in smart cities and environments

The use of direct current distribution systems in delivering scalable charging infrastructure for battery electric vehicles

The use of low voltage direct current (LVDC) distribution is becoming recognised as a technology enabler that can be used to efficiently network native DC generators with DC loads, offer improved power sharing capabilities, reduce power system material resource requirements and enhance the performance of variable speed machinery. Practical deployment opportunities for LVDC range from small-scale microgrids in the context of energy for development to sophisticated, modern building-level power distribution systems for commercial office spaces, manufacturing applications and industrial processes. However, the incumbent AC distribution system benefits from existing technical product and safety standards, which makes the early adoption of LVDC systems challenging from a risk and cost perspective. Concurrently, the demand for native DC loads such as Battery Electric Transportation Systems is growing. This is especially significant in the area of private electric vehicles (EVs), taxis and buses, but the prospect of electric trucks, ferries and shortrange aircraft are also tangible opportunities. The success of this electric transport revolution depends on several factors, one of which is the availability of battery charging infrastructure that can cost effectively integrate with the existing electrical network, deliver adequate energy transfer rates and adapt to the rapid technical development of this industry. This thesis explores the application of two, novel LVDC distribution systems for the development of scalable EV charging networks; where charging infrastructure has the ability to scale with increasing EV adoption and has a lower risk of becoming a stranded asset in the future. The modelling is supported by real, rapid DC charger utilisation data from the national charging network in Scotland, comprising over 192 chargers and 400,000 charging events. During the work of this thesis, it was found that a combined heat and power (CHP) system can economically support short duration charging scenarios by providing additional power capacity in a congested electrical grid. In this case the highest system efficiency and Net Present Value (NPV) is achieved with a fuel cell directly connected to the DC charging network, compared to other gas reciprocating CHP options. Furthermore, the proposition of a reconfigurable LVDC charging network, interfaced to the public AC distribution network, reduces the capital outlay, offers a higher NPV and improved scalability compared to other charging solutions. For charging system designers and operators, it was found that rapid DC chargers can be classified by specific locations, each possessing a distinct Gaussian arrival pattern and Gamma distribution for charging energy delivered.The use of low voltage direct current (LVDC) distribution is becoming recognised as a technology enabler that can be used to efficiently network native DC generators with DC loads, offer improved power sharing capabilities, reduce power system material resource requirements and enhance the performance of variable speed machinery. Practical deployment opportunities for LVDC range from small-scale microgrids in the context of energy for development to sophisticated, modern building-level power distribution systems for commercial office spaces, manufacturing applications and industrial processes. However, the incumbent AC distribution system benefits from existing technical product and safety standards, which makes the early adoption of LVDC systems challenging from a risk and cost perspective. Concurrently, the demand for native DC loads such as Battery Electric Transportation Systems is growing. This is especially significant in the area of private electric vehicles (EVs), taxis and buses, but the prospect of electric trucks, ferries and shortrange aircraft are also tangible opportunities. The success of this electric transport revolution depends on several factors, one of which is the availability of battery charging infrastructure that can cost effectively integrate with the existing electrical network, deliver adequate energy transfer rates and adapt to the rapid technical development of this industry. This thesis explores the application of two, novel LVDC distribution systems for the development of scalable EV charging networks; where charging infrastructure has the ability to scale with increasing EV adoption and has a lower risk of becoming a stranded asset in the future. The modelling is supported by real, rapid DC charger utilisation data from the national charging network in Scotland, comprising over 192 chargers and 400,000 charging events. During the work of this thesis, it was found that a combined heat and power (CHP) system can economically support short duration charging scenarios by providing additional power capacity in a congested electrical grid. In this case the highest system efficiency and Net Present Value (NPV) is achieved with a fuel cell directly connected to the DC charging network, compared to other gas reciprocating CHP options. Furthermore, the proposition of a reconfigurable LVDC charging network, interfaced to the public AC distribution network, reduces the capital outlay, offers a higher NPV and improved scalability compared to other charging solutions. For charging system designers and operators, it was found that rapid DC chargers can be classified by specific locations, each possessing a distinct Gaussian arrival pattern and Gamma distribution for charging energy delivered

A novel backup protection scheme for hybrid AC/DC power systems

This thesis presents and demonstrates (both via simulation and hardware-based tests) a new protection scheme designed to safeguard hybrid AC/DC distribution networks against DC faults that are not cleared by the main MVDC (Medium Voltage DC) link protection. The protection scheme relies on the apparent impedance measured at the AC "side" of the MVDC link to detect faults on the DC system. It can be readily implemented on existing distance protection relays with no changes to existing measuring equipment. An overview of the literature in this area is presented and it is shown that the protection of MVDC links is only considered at a converter station level. There appears to be no consideration of protecting the MVDC system from the wider AC power system via backup - as would be the case for standard AC distribution network assets, where the failure of main protection would require a (usually remote) backup protection system to operate to clear the fault. Very little literature considers remote backup protection of MVDC links.;To address this issue, the research presented in this thesis characterises the apparent impedance as measured in the neighbouring AC system under various DC fault conditions on an adjacent MVDC link. Initial studies, based on simulations, show that a highly inductive characteristic, in terms of the calculations from the measured AC voltages and currents, is apparent on all three phases in the neighbouring AC system during DC-side pole-to-pole and pole-poleground faults. This response is confirmed via a series of experiments conducted at low voltage in a laboratory environment using scaled down electrical components. From this classification, a fast-acting backup protection methodology, which can detect pole-to-pole and pole-poleground faults within 40 ms, is proposed and trialled through simulation. The solution can be deployed on distance protection relays using a typically unused zone (e.g. zone 4).;New relays could, of course, incorporate this functionality as standard in the future. To maximise confidence and demonstrate the compatibility of the solution, the protection scheme is deployed under a real-time hardware-in-the-loop environment using a commercially available distance protection relay. Suggestions to improve the stability of the proposed solution are discussed and demonstrated. Future areas of work are identified and described. As an appendix, early stage work pertaining to the potential application and benefits of MVDC is presented for two Scottish distribution networks. The findings from this are presented as supplementary material at the end of the thesis.This thesis presents and demonstrates (both via simulation and hardware-based tests) a new protection scheme designed to safeguard hybrid AC/DC distribution networks against DC faults that are not cleared by the main MVDC (Medium Voltage DC) link protection. The protection scheme relies on the apparent impedance measured at the AC "side" of the MVDC link to detect faults on the DC system. It can be readily implemented on existing distance protection relays with no changes to existing measuring equipment. An overview of the literature in this area is presented and it is shown that the protection of MVDC links is only considered at a converter station level. There appears to be no consideration of protecting the MVDC system from the wider AC power system via backup - as would be the case for standard AC distribution network assets, where the failure of main protection would require a (usually remote) backup protection system to operate to clear the fault. Very little literature considers remote backup protection of MVDC links.;To address this issue, the research presented in this thesis characterises the apparent impedance as measured in the neighbouring AC system under various DC fault conditions on an adjacent MVDC link. Initial studies, based on simulations, show that a highly inductive characteristic, in terms of the calculations from the measured AC voltages and currents, is apparent on all three phases in the neighbouring AC system during DC-side pole-to-pole and pole-poleground faults. This response is confirmed via a series of experiments conducted at low voltage in a laboratory environment using scaled down electrical components. From this classification, a fast-acting backup protection methodology, which can detect pole-to-pole and pole-poleground faults within 40 ms, is proposed and trialled through simulation. The solution can be deployed on distance protection relays using a typically unused zone (e.g. zone 4).;New relays could, of course, incorporate this functionality as standard in the future. To maximise confidence and demonstrate the compatibility of the solution, the protection scheme is deployed under a real-time hardware-in-the-loop environment using a commercially available distance protection relay. Suggestions to improve the stability of the proposed solution are discussed and demonstrated. Future areas of work are identified and described. As an appendix, early stage work pertaining to the potential application and benefits of MVDC is presented for two Scottish distribution networks. The findings from this are presented as supplementary material at the end of the thesis

Design and Implementation of a True Decentralized Autonomous Control Architecture for Microgrids

Microgrids can serve as an integral part of the future power distribution systems. Most microgrids are currently managed by centralized controllers. There are two major concerns associated with the centralized controllers. One is that the single controller can become performance and reliability bottleneck for the entire system and its failure can bring the entire system down. The second concern is the communication delays that can degrade the system performance. As a solution, a true decentralized control architecture for microgrids is developed and presented. Distributing the control functions to local agents decreases the possibility of network congestion, and leads to the mitigation of long distance transmission of critical commands. Decentralization will also enhance the reliability of the system since the single point of failure is eliminated. In the proposed architecture, primary and secondary microgrid controls layers are combined into one physical layer. Tertiary control is performed by the controller located at the grid point of connection. Each decentralized controller is responsible of multicasting its status and local measurements, creating a general awareness of the microgrid status among all decentralized controllers. The proof-of concept implementation provides a practical evidence of the successful mitigation of the drawback of control command transmission over the network. A Failure Management Unit comprises failure detection mechanisms and a recovery algorithm is proposed and applied to a microgrid case study. Coordination between controllers during the recovery period requires low-bandwidth communications, which has no significant overhead on the communication infrastructure. The proof-of-concept of the true decentralization of microgrid control architecture is implemented using Hardware-in-the-Loop platform. The test results show a robust detection and recovery outcome during a system failure. System test results show the robustness of the proposed architecture for microgrid energy management and control scenarios

Efficient use of deep learning and machine learning for load forecasting in South African power distribution networks

Abstract: Load forecasting, which is the act of anticipating future loads, has been shown to be important in power system network planning, operations and maintenance. Artificial Intelligence (AI) techniques have been shown to be good tools for load forecasting. Load forecasting can assist power distribution utilities maximise their revenue through optimising maintenance planning. With the dawn of the smart grid, first world countries have moved past the customer’s point of supply and use smart meters to forecast customer loads. These recent studies also utilise recent state of the art AI techniques such as deep learning techniques. Weather parameters are such as temperature, humidity and rainfall are usually used as parameters in these studies. South African load forecasting studies are outdated and recent studies are limited. Most of these studies are from 2010, and dating backwards to 1999. Hence they do not use recent state of the art AI techniques. The studies do not focus at distribution level load forecasting for optimal maintenance planning. The impact of adjusting power consumption data when there are spikes and dips in the data was not investigated in all these South African studies. These studies did not investigate the impact of weather parameters on different South African loads and hence load forecasting performance...D.Phil. (Electrical and Electronic Management

Simplified control strategies for modular multilevel matrix converter for offshore low frequency AC transmission system

PhD ThesisThe Low frequency AC (LFAC) transmission system is considered as the most cost-saving choice for the short and intermediate distance. It not only improves the transmission capacity and distance but also has higher reliability which makes it more advantageous than the HVDC transmission system. Modular Multilevel Matrix Converter (M3C) is recognized as the most suitable frequency converter for the LFAC transmission system which is responsible for connecting 16.7 Hz and 50 Hz ac systems. In such applications, the ‘double αβ0 transform’ control method is most popular technique that realizes the decoupled control of the input current, output current and circulating current. However, the derivation process of the mathematical model is so complicated that it gives too much burden on the controller of the M3C system. Therefore, this thesis is focusing on simplifying the M3C control strategies when used in LFAC systems and the primary contribution to the knowledge is outlined as follows: (1) A simplified hierarchical energy balance control method which employs an independent control for each of three sub-converters in M3C is proposed in Chapter 5. The output frequency circulating current is injected and utilized to balance the energy between the three arms of the sub-converter. The proposed method achieves a reduced execution time and a simplified control structure, with which a low-cost processor is applicable and the control bandwidth of the system is improved. (2) An improved energy balance control method with injecting both input and output frequency circulating currents is proposed in Chapter 6. The magnitudes of the circulating current responsible for the energy balance control in either frequency are half reduced as compared to the single frequency injection method in Chapter 5. This arrangement alleviates the negative impact of the injected circulating current on the external grid and allows the M3C systems work through larger grid unbalance situations. Finally, the effectiveness of the proposed control strategy is demonstrated by extensive simulation results and validated experimentally using a scaled-down laboratory prototype

Clothing-Integrated Human-Technology Interaction

Due to the different disabilities of people and versatile use environments, the current handheld and screen-based digital devices on the market are not suitable for all consumers and all situations. Thus, there is an urgent need for human- technology interaction solutions, where the required input actions to digital devices are simple, easy to establish, and instinctive, allowing the whole society to effortlessly interact with the surrounding technology. In passive ultra-high frequency (UHF) radio frequency identification (RFID) systems, the tag consists only of an antenna and a simple integrated circuit (IC). The tag gets all the needed power from the RFID reader and can be thus seamlessly and in a maintenance-free way integrated into clothing. In this thesis, it is presented that by integrating passive UHF RFID technology into clothing, body movements and gestures can be monitored by monitoring the individual IDs and backscattered signals of the tags. Electro-textiles and embroidery with conductive thread are found to be suitable options when manufacturing and materials for such garments are considered. This thesis establishes several RFID- based interface solutions, multiple types of inputs through RFID platforms, and controlling the surrounding and communicating with RFID-based on/off functions. The developed intelligent clothing is visioned to provide versatile applications for assistive technology, for entertainment, and ambient assistant living, and for comfort and safety in work environments, just to name a few examples

Modelado Estocástico e Integración de Recursos Energéticos Distribuidos en la Red Eléctrica Inteligente

The residential sector accounts for approximately 30% of the energy consumed in developed countries. This demand is currently covered not only by fossil fuels but also renewable energy sources that ensure a reduction in polluting emissions but which are generally distributed, generate intermittently and are difficult to manage. This requires the development of energy policies that reduce global consumption, as well as control and management systems that target the final consumer. In order to deal with this issue a detailed knowledge of the consumers’ behaviour is needed, both at an aggregate level for the management of the system and at an individual level for the development of measures to adapt their consumption. Furthermore, in this novel context, the feasibility of the different available strategies must be studied in addition to the benefits that can be obtained from their implementation and the control measures that can be developed. This PhD Thesis addresses the development of an energy modelling system for the residential sector as a way of predicting the electricity demand in households and establishing demand response strategies, energy policies and control actions that ease the integration process of distributed energy resources accordingly. The selected modelling technique follows the so-called bottom-up methodology, which enables the consumption in the residential sector as the sum of the individual contributions of each device installed in each household to be obtained. In addition, the simulation of these profiles is carried out using stochastic techniques that allow the heterogeneous and unpredictable behaviour of residents to be reproduced with a high temporal resolution. The modelling system has been divided into three main components which include the consumption due to lighting systems, the heating and air conditioning devices demand and the general appliances consumption. This has facilitated a detailed study of different energy saving policies and the assessment of potential demand response strategies, as well as the development of novel energy management techniques. All of these measures together with the modelling system have been implemented in a simulation tool which was also provided with renewable production data, collected in actual installations. Therefore, not only has the consumption been studied on its own, but also the integration of various resources has been assessed. Some of the studied measures are: replacing devices with more efficient technologies in the case of lighting systems, implementing low-level demand response strategies for household appliances, studying the impact on the low-voltage grid of increasing installation rates of certain technologies such as air conditioning systems and developing novel control techniques in the context of a smart community that can improve the hosting capacity of renewable solar production. Finally, the models and strategies studied in this work have been combined with an advanced metering infrastructure under the umbrella of a smart building. In this context, they provided an additional source of information towards the digitalisation of the electrical system where the extensive use of data allows for the implementation of even more advanced control strategies and will undoubtedly lead to future developments under the paradigm of Smart Grids.El sector residencial representa aproximadamente el 30% de la energía consumida en los países desarrollados. Esta demanda está actualmente cubierta no solo por combustibles fósiles sino también por fuentes renovables que aseguran una reducción en las emisiones contaminantes, pero que generalmente se encuentran distribuidas, producen intermitentemente y son difíciles de gestionar. Esto exige el desarrollo de políticas energéticas que reduzcan el consumo global y sistemas de control y gestión que tengan como objetivo el consumidor final. Solucionar estos retos pasa por conocer el comportamiento los consumidores, tanto a nivel agregado para la gestión del sistema, como a nivel individual para el desarrollo de medidas de adaptación de su propio consumo. Además, en este contexto novedoso es necesario estudiar la viabilidad de las distintas estrategias, los beneficios que se pueden obtener y las medidas de control adicionales que pueden ser desarrolladas. La siguiente Tesis doctoral plantea el desarrollo de un sistema de modelado del consumo en el sector residencial como medio para predecir las necesidades de demanda eléctrica dentro de la red inteligente y establecer a partir de ellas medidas de respuesta a la demanda, políticas energéticas y acciones de control que ayuden a la integración de los recursos energéticos distribuidos. La técnica de modelado escogida sigue una metodología bottom-up (de abajo a arriba) que permite obtener el consumo en el sector residencial como la suma de las contribuciones de cada dispositivo instalado en cada vivienda. Además, la simulación de dichas curvas se ha realizado mediante técnicas estocásticas que permiten reproducir el comportamiento heterogéneo y poco predecible de los residentes con altas resoluciones temporales. El sistema de modelado se ha dividido en tres componentes principales que son el consumo en iluminación, el consumo en calefacción y aire acondicionado y el consumo en electrodomésticos de uso generales. Esto ha permitido un estudio detallado de las distintas medidas de ahorro energético y potenciales estrategias de respuesta a la demanda así como el desarrollo de novedosas técnicas de gestión energética. Todas estas medidas junto con el sistema de modelado han sido implementadas en una herramienta de simulación en la cual se han incluido también datos de producción renovable recogidos en instalaciones reales. De este modo, no solo se ha estudiado el consumo de forma independiente, sino que diversas medidas energéticas han sido también evaluadas. Algunas de ellas han sido: la sustitución de dispositivos por tecnologías más eficientes en el caso de sistemas de iluminación, la implementación de estrategias de respuesta a la demanda a bajo nivel para los electrodomésticos disponibles en los hogares, el estudio del impacto en la red de baja tensión del aumento de determinadas tecnologías como los sistemas de aire acondicionado y el desarrollo de técnicas de control en el contexto de una comunidad inteligente que mejoren la capacidad de acogida de producción fotovoltaica. Finalmente, los modelos y estrategias estudiadas han sido integradas junto con un sistema de contadores inteligentes bajo el paraguas de un edificio gestionable. En este contexto, han aportado una fuente adicional de información hacia la digitalización del sistema eléctrico donde el uso masivo de datos permite implementar estrategias de control aun más avanzadas y que dará pie sin lugar a dudas a futuros desarrollos

Composite power semiconductor switches for high-power applications

It is predicted that 80 % of the world’s electricity will flow through power electronic based converters by 2030, with a growing demand for renewable technolo gies and the highest levels of efficiency at every stage from generation to load. At the heart of a power electronic converter is the power semiconductor switch which is responsible for controlling and modulating the flow of power from the input to the output. The requirements for these power semiconductor switches are vast, and include: having an extremely low level of conduction and switching losses; being a low source of electromagnetic noise, and not being susceptible to external Electromagnetic Interference (EMI); and having a good level of ruggedness and reliability. These high-performance switches must also be economically viable and not have an unnecessarily large manufacturing related carbon footprint. This thesis investigates the switching performance of the two main semiconductor switches used in high-power applications — the well-established Silicon (Si)-Insulated-Gate Bipolar Transistor (IGBT) and the state-of-the-art Wide-Bandgap (WBG) Silicon-Carbide (SiC)-Metal–Oxide–Semiconductor Field-Effect Transistor (MOSFET). The SiC-MOSFET is ostensibly a better device than the Si-IGBT due to the lower level of losses, however the cost of the device is far greater and there are characteristics which can be troublesome, such as the high levels of oscillatory behaviour at the switching edges which can cause serious Electromagnetic Compatibility (EMC) issues. The operating mechanism of these devices, the materials which are used to make them, and their auxiliary components are critically analysed and discussed. This includes a head-to-head comparison of the two high-capacity devices in terms of their losses and switching characteristics. The design of a high-power Double-Pulse Test Rig (DPTR) and the associated high-bandwidth measurement platform is presented. This test rig is then extensively used throughout this thesis to experimentally characterise the switching performance of the aforementioned high-capacity power semiconductor devices. A hybrid switch concept — termed “The Diverter” — is investigated, with the motivation of achieving improved switching performance without the high-cost of a full SiC solution. This comprises a fully rated Si-IGBT as the main conduction device and a part-rated SiC-MOSFET which is used at the turn-off. The coordinated switching scheme for the Si/SiC-Diverter is experimentally examined to determine the required timings which yield the lowest turn-off loss and the lowest level of oscillatory behaviour and other EMI precursors. The thermal stress imposed on the part-rated SiC-MOSFET is considered in a junction temperature simulation and determined to be negligible. This concept is then analysed in a grid-tied converter simulation and compared to a fully rated SiC-MOSFET and Si-IGBT. A conduction assistance operating mode, which solely uses the part-rated SiC-MOSFET when within its rating, is also investigated. Results show that the Diverter achieves a significantly lower level of losses compared to a Si-IGBT and only marginally higher than a full SiC solution. This is achieved at a much lower cost than a full SiC solution and may also provide a better method of achieving high-current SiC switche