System configuration, fault detection, location, isolation and restoration: a review on LVDC Microgrid protections

Low voltage direct current (LVDC) distribution has gained the significant interest of research due to the advancements in power conversion technologies. However, the use of converters has given rise to several technical issues regarding their protections and controls of such devices under faulty conditions. Post-fault behaviour of converter-fed LVDC system involves both active converter control and passive circuit transient of similar time scale, which makes the protection for LVDC distribution significantly different and more challenging than low voltage AC. These protection and operational issues have handicapped the practical applications of DC distribution. This paper presents state-of-the-art protection schemes developed for DC Microgrids. With a close look at practical limitations such as the dependency on modelling accuracy, requirement on communications and so forth, a comprehensive evaluation is carried out on those system approaches in terms of system configurations， fault detection, location, isolation and restoration

A Viable Residential DC Microgrid for Low Income Communities – Architecture, Protection and Education

The availability of fossil fuels in the future and the environmental effects such as the carbon footprint of the existing methodologies to produce electricity is an increasing area of concern. In rural areas of under-developed parts of the world, the problem is lack of access to electrification. DC microgrids have become a proven solution to electrification in these areas with demonstrated exceptional quality of power, high reliability, efficiency, and simplified integration between renewable energy sources (principally solar PV) and energy storage. In the United States, a different problem occurs that can be addressed with the same DC microgrid approach that is finding success internationally. In disinvested, underserved communities with high unemployment and low wages, households contribute a significant portion of their income towards the fixed cost of their electrical utility connection, which by law must be supplied to every household. In order to realize such a microgrid in these communities, there are three major areas which need to be accounted for. Firstly, there needs to be a custom architecture for the community under consideration and it needs to be economical to match the needs of the underserved community. Secondly, DC microgrid for home energy interconnection is potentially less complex and less expensive to deploy, operate and maintain however, faster protection is a key element to ensuring resilience, viability and adoptability. Lastly, these types of efforts will be sustainable only if the people in the community are educated and invested in the same as they are the key stakeholders in these systems. This dissertation presents an approach to make the DC Microgrid economically feasible for low income households by reducing the cost they incur on electric bills. The approach is to overlay a DC system into homes that have a utility feed in order to incorporate renewable energy usage into an urban setting for the express purpose of driving down individual household utility costs. The results show that the incorporation of a certain level of “smart” appliances and fixtures into the renovation of vacated homes and the use of a microgrid to enable sharing of renewable energy, such as solar power combined with energy storage, between homes in the proposed architecture yields the least expensive option for the patrons. The development of solid state circuit breakers that interface between the microgrid and the home DC power panels helps in faster protection of the DC system. In this dissertation, a SiC JFET based device is designed and built to protect against DC faults at a faster rate than the available solutions. The prototype is tested for verification and used to discriminate against short circuit faults and the results show the successful fault discrimination capabilities of the device. A basic system level simulation with the protection device is implemented using Real Time Hardware in the loop platform. Finally, as a part of engaging the community members, the high school kids in the area who might potentially be living in some of the houses in this community are being educated about the microgrid, appliances and other technologies to get a better understanding of STEM and hopefully inspiring them to pursue a career in STEM in the future

A Viable Residential DC Microgrid for Low Income Communities – Architecture, Protection and Education

The availability of fossil fuels in the future and the environmental effects such as the carbon footprint of the existing methodologies to produce electricity is an increasing area of concern. In rural areas of under-developed parts of the world, the problem is lack of access to electrification. DC microgrids have become a proven solution to electrification in these areas with demonstrated exceptional quality of power, high reliability, efficiency, and simplified integration between renewable energy sources (principally solar PV) and energy storage. In the United States, a different problem occurs that can be addressed with the same DC microgrid approach that is finding success internationally. In disinvested, underserved communities with high unemployment and low wages, households contribute a significant portion of their income towards the fixed cost of their electrical utility connection, which by law must be supplied to every household. In order to realize such a microgrid in these communities, there are three major areas which need to be accounted for. Firstly, there needs to be a custom architecture for the community under consideration and it needs to be economical to match the needs of the underserved community. Secondly, DC microgrid for home energy interconnection is potentially less complex and less expensive to deploy, operate and maintain however, faster protection is a key element to ensuring resilience, viability and adoptability. Lastly, these types of efforts will be sustainable only if the people in the community are educated and invested in the same as they are the key stakeholders in these systems. This dissertation presents an approach to make the DC Microgrid economically feasible for low income households by reducing the cost they incur on electric bills. The approach is to overlay a DC system into homes that have a utility feed in order to incorporate renewable energy usage into an urban setting for the express purpose of driving down individual household utility costs. The results show that the incorporation of a certain level of “smart” appliances and fixtures into the renovation of vacated homes and the use of a microgrid to enable sharing of renewable energy, such as solar power combined with energy storage, between homes in the proposed architecture yields the least expensive option for the patrons. The development of solid state circuit breakers that interface between the microgrid and the home DC power panels helps in faster protection of the DC system. In this dissertation, a SiC JFET based device is designed and built to protect against DC faults at a faster rate than the available solutions. The prototype is tested for verification and used to discriminate against short circuit faults and the results show the successful fault discrimination capabilities of the device. A basic system level simulation with the protection device is implemented using Real Time Hardware in the loop platform. Finally, as a part of engaging the community members, the high school kids in the area who might potentially be living in some of the houses in this community are being educated about the microgrid, appliances and other technologies to get a better understanding of STEM and hopefully inspiring them to pursue a career in STEM in the future

Techno-economic impact of single feeder: multiple microgrids on power utility companies.

Masters Degree. University of KwaZulu-Natal, Durban.Abstract available in the PDFList of Figures on page numbers ix-xi

Protection of Future Electricity Systems

The electrical energy industry is undergoing dramatic changes: massive deployment of renewables, increasing share of DC networks at transmission and distribution levels, and at the same time, a continuing reduction in conventional synchronous generation, all contribute to a situation where a variety of technical and economic challenges emerge. As the society’s reliance on electrical power continues to increase as a result of international decarbonisation commitments, the need for secure and uninterrupted delivery of electrical energy to all customers has never been greater. Power system protection plays an important enabling role in future decarbonized energy systems. This book includes ten papers covering a wide range of topics related to protection system problems and solutions, such as adaptive protection, protection of HVDC and LVDC systems, unconventional or enhanced protection methods, protection of superconducting transmission cables, and high voltage lightning protection. This volume has been edited by Adam Dyśko, Senior Lecturer at the University of Strathclyde, UK, and Dimitrios Tzelepis, Research Fellow at the University of Strathclyde

Distributed Power Generation in Europe: Technical Issues for Further Integration

The electric power sector in Europe is currently facing different changes and evolutions mainly in response to the three issues at EU level - environmental sustainability, security of supply, and competitiveness. These issues, against a background of growing electricity demand, may represent drivers for facilitating the further deployment of Distributed Power Generation technologies in Europe. The present Report focuses on the potential role of Distributed Power Generation (or simply Distributed Generation, DG) in a European perspective. More specifically, this work aims to assess the technical issues and developments related to DG technologies and their integration into the European power systems. As a starting point the concept of Distributed Generation is characterised for the purpose of the study. Distributed Generation, defined as an electric power source connected to the distribution network, serving a customer on-site or providing network support, may offer various benefits to the European electric power systems. DG technologies may consist of small/medium size, modular energy conversion units, which are generally located close to end users and transform primary energy resources into electricity and eventually heat. There are, however, major issues concerning the integration of DG technology into the distribution networks. In fact, the existing distribution networks were not generally designed to operate in presence of DG technologies. Consequently, a sustained increase in the deployment of DG resources may imply several changes in the electric power system architecture in the near future. The present Report on Distributed Generation in Europe, after an overview of the basic elements of electric power systems, introduces the proposed definition and main features of DG. Then, it reviews the state-of-the-art of DG technologies as well as focuses on current DG grid integration issues. Technical solutions towards DG integration in Europe and developments concerning the future distribution systems are also addressed in the study.JRC.F.7-Energy systems evaluatio

Resilience-driven planning and operation of networked microgrids featuring decentralisation and flexibility

High-impact and low-probability extreme events including both man-made events and natural weather events can cause severe damage to power systems. These events are typically rare but featured in long duration and large scale. Many research efforts have been conducted on the resilience enhancement of modern power systems. In recent years, microgrids (MGs) with distributed energy resources (DERs) including both conventional generation resources and renewable energy sources provide a viable solution for the resilience enhancement of such multi-energy systems during extreme events. More specifically, several islanded MGs after extreme events can be connected with each other as a cluster, which has the advantage of significantly reducing load shedding through energy sharing among them. On the other hand, mobile power sources (MPSs) such as mobile energy storage systems (MESSs), electric vehicles (EVs), and mobile emergency generators (MEGs) have been gradually deployed in current energy systems for resilience enhancement due to their significant advantages on mobility and flexibility. Given such a context, a literature review on resilience-driven planning and operation problems featuring MGs is presented in detail, while research limitations are summarised briefly. Then, this thesis investigates how to develop appropriate planning and operation models for the resilience enhancement of networked MGs via different types of DERs (e.g., MGs, ESSs, EVs, MESSs, etc.). This research is conducted in the following application scenarios: 1. This thesis proposes novel operation strategies for hybrid AC/DC MGs and networked MGs towards resilience enhancement. Three modelling approaches including centralised control, hierarchical control, and distributed control have been applied to formulate the proposed operation problems. A detailed non-linear AC OPF algorithm is employed to model each MG capturing all the network and technical constraints relating to stability properties (e.g., voltage limits, active and reactive power flow limits, and power losses), while uncertainties associated with renewable energy sources and load profiles are incorporated into the proposed models via stochastic programming. Impacts of limited generation resources, load distinction intro critical and non-critical, and severe contingencies (e.g., multiple line outages) are appropriately captured to mimic a realistic scenario. 2. This thesis introduces MPSs (e.g., EVs and MESSs) into the suggested networked MGs against the severe contingencies caused by extreme events. Specifically, time-coupled routing and scheduling characteristics of MPSs inside each MG are modelled to reduce load shedding when large damage is caused to each MG during extreme events. Both transportation networks and power networks are considered in the proposed models, while transporting time of MPSs between different transportation nodes is also appropriately captured. 3. This thesis focuses on developing realistic planning models for the optimal sizing problem of networked MGs capturing a trade-off between resilience and cost, while both internal uncertainties and external contingencies are considered in the suggested three-level planning model. Additionally, a resilience-driven planning model is developed to solve the coupled optimal sizing and pre-positioning problem of MESSs in the context of decentralised networked MGs. Internal uncertainties are captured in the model via stochastic programming, while external contingencies are included through the three-level structure. 4. This thesis investigates the application of artificial intelligence techniques to power system operations. Specifically, a model-free multi-agent reinforcement learning (MARL) approach is proposed for the coordinated routing and scheduling problem of multiple MESSs towards resilience enhancement. The parameterized double deep Q-network method (P-DDQN) is employed to capture a hybrid policy including both discrete and continuous actions. A coupled power-transportation network featuring a linearised AC OPF algorithm is realised as the environment, while uncertainties associated with renewable energy sources, load profiles, line outages, and traffic volumes are incorporated into the proposed data-driven approach through the learning procedure.Open Acces

Coordinated and optimized voltage management of distribution networks with multi-microgrids

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 201

A Review of Current Research Trends in Power-Electronic Innovations in Cyber-Physical Systems.

In this paper, a broad overview of the current research trends in power-electronic innovations in cyber-physical systems (CPSs) is presented. The recent advances in semiconductor device technologies, control architectures, and communication methodologies have enabled researchers to develop integrated smart CPSs that can cater to the emerging requirements of smart grids, renewable energy, electric vehicles, trains, ships, internet of things (IoTs), etc. The topics presented in this paper include novel power-distribution architectures, protection techniques considering large renewable integration in smart grids, wireless charging in electric vehicles, simultaneous power and information transmission, multi-hop network-based coordination, power technologies for renewable energy and smart transformer, CPS reliability, transactive smart railway grid, and real-time simulation of shipboard power systems. It is anticipated that the research trends presented in this paper will provide a timely and useful overview to the power-electronics researchers with broad applications in CPSs.post-print2.019 K