T.J. Hammons

Bio: T.J. Hammons is an academic researcher from University of Glasgow. The author has contributed to research in topics: Electric power system & Electricity generation. The author has an hindex of 11, co-authored 64 publications receiving 1086 citations.

Flexible AC transmission systems (FACTS)

Abstract: The paper reviews literature which addresses the application of Flexible AC Transmission System (FACTS) concepts to the improvement of Power System utilisation and performance. It summarises literature on using high speed thyristor based control of HVAC power system elements to enhance the power carrying capacity of existing transmission circuits without compromising reliability. It describes a study system representative of existing power systems that has been developed to evaluate the economic and technical issues of loading transmission lines to their thermal limits. Considered are two scenarios, a multi-line corridor and a long radial interconnection, where the issues addressed are transient and dynamic stability, power flow control, reactive support and voltage stability. A benchmark system is developed to validate performance of die more simple devices. It is concluded that FACTS devices have the potential to significantly increase system stability margins thereby increasing loading capabil...

Renewable energy alternatives for developed countries

Abstract: This paper examines renewable energy alternatives in developed countries: environmental mechanisms; future energy alternatives; green electricity marketing and its potential; pricing; and limitations on the eve of open access. It discusses objectives in electricity restructuring; the role of resources planning in forming long range energy environmental policies; feasibility of electricity trading mechanisms; green marketing in the United States and Australia; green energy offers in Canada; and the results of green pricing programs in Europe and the United States. The role of existing and planned mechanisms to achieve environmental benefits in restructured electricity markets are reviewed. Technological and institutional challenges of achieving real, long-term reductions in carbon dioxide and other emissions from the electric sector are discussed. Factors associated with infrastructure turnover together with technology development and deployment are addressed, where attention is given to policies which promote highly integrated and coordinated reductions in emissions. The paper then focuses on the green pool and trends in power marketing where status of competitive markets, green pricing programs for franchise customers, green power products for contestable customers, credibility of green power marketing, and public policy for renewable energy technologies in competitive markets are discussed. It then reviews green energy in Ontario on the eve of open access, and shows there is a market for green energy if customers have a choice.

African electricity infrastructure interconnections and electricity exchanges

Abstract: This paper discusses African electrical energy resources: feasibility studies, interconnection of power systems, the present state of the electric power sector, future expansion of African power systems, and implementation of an African power grid network. It examines involvement of the World Bank with African electricity infrastructure, Grand Inga interconnection projects, the Great Lakes project, and prospects for evaluation of a unified power system in Africa. First, the poorness of African countries and their limited electricity infrastructure is discussed. Objectives for electricity infrastructure development in response to perceived needs is examined and the development challenge for the future, with ways of meeting that challenge defined. Grand Inga interconnections projects are then reviewed. The Democratic Republic of Congo's potential is equivalent to 88400 MW of continuous energy; 42000 MW is located in the Inga region. Development of the Great Lakes interconnected network which links Burundi, Rwanda and Democratic Republic of Congo is also reviewed. The paper discusses existing power systems in Africa and presents the idea of dividing the continent into five main regions of about the same surface area for electricity trade. Feasibility studies of an HVDC line from Democratic Republic of Congo to Egypt and other studies to South Africa and Europe are discussed. A scenario for energy balance for the 2050 is presented, and export of electricity to neighboring continents, mainly Europe, in excess of 200 TWh/year by 2050 is outlined. Implementation of an integrated African grid network is discussed.

Voltage dips due to direct connection of induction generators in low head hydro electric schemes

Abstract: This paper analyses phenomena which affect voltage dip due to direct connection of induction generators running close to synchronous speed to electrical distribution systems in low head hydroelectric power schemes. The paper examines transient phenomena on connection of induction generators at close to synchronous speed in determining whether costly system reinforcement may be avoided thus making many uneconomic developments viable while satisfying constraints of permissible voltage dip if the transient phenomena is taken duly into account. More use of renewable energy in electricity supply thus reducing greenhouse gas emissions from fossil plant will therefore result. The analysis is based on a detailed induction generator model with single and double rotor bar simulation using Park's equations with simulation of rotor dynamics on connection of the generator to the electrical supply. >

VSC-Based HVDC Power Transmission Systems: An Overview

Abstract: The ever increasing progress of high-voltage high-power fully controlled semiconductor technology continues to have a significant impact on the development of advanced power electronic apparatus used to support optimized operations and efficient management of electrical grids, which, in many cases, are fully or partially deregulated networks. Developments advance both the HVDC power transmission and the flexible ac transmission system technologies. In this paper, an overview of the recent advances in the area of voltage-source converter (VSC) HVdc technology is provided. Selected key multilevel converter topologies are presented. Control and modeling methods are discussed. A list of VSC-based HVdc installations worldwide is included. It is confirmed that the continuous development of power electronics presents cost-effective opportunities for the utilities to exploit, and HVdc remains a key technology. In particular, VSC-HVdc can address not only conventional network issues such as bulk power transmission, asynchronous network interconnections, back-to-back ac system linking, and voltage/stability support to mention a few, but also niche markets such as the integration of large-scale renewable energy sources with the grid and most recently large onshore/offshore wind farms.

Modular Multilevel Converters for HVDC Applications: Review on Converter Cells and Functionalities

Abstract: In this paper, the principle of modularity is used to derive the different multilevel voltage and current source converter topologies. The paper is primarily focused on high-power applications and specifically on high-voltage dc systems. The derived converter cells are treated as building blocks and are contributing to the modularity of the system. By combining the different building blocks, i.e., the converter cells, a variety of voltage and current source modular multilevel converter topologies are derived and thoroughly discussed. Furthermore, by applying the modularity principle at the system level, various types of high-power converters are introduced. The modularity of the multilevel converters is studied in depth, and the challenges as well as the opportunities for high-power applications are illustrated.

Energy services for the Millennium Development Goals.

Abstract: In line with the UN Millennium Project more broadly, this report on energy addresses three crucial components: firstly, a rigorous understanding of the energy services that drive and, when absent, impede progress towards achieving the MDGs in different parts of the world; secondly, a clear sense of the operational challenges faced by the world's poorest countries in providing these services; and thirdly, a systematic set of recommendations as to how these energy challenges can be met. The report shows linkages between all of the MDGs and energy and argues that much greater quality and quantity of energy services will be required to meet the MDGs. The report also illustrates the distinct roles of women and men in relation to the provision and use of energy services, the critical importance of associating women with the provision of modern energy services, as well as the distinct routes needed to scale up energy services in rural and urban areas.

Flexible power transmission--the HVDC options

Abstract: Chapter 1 INTRODUCTION. Chapter 2 SEMICONDUCTOR POWER DEVICES. Chapter 3 LINE COMMUTATED HVDC CONVERSION (LCC). Chapter 4 SELF-COMMUTATING CONVERSION. Chapter 5 PULSE WIDTH MODULATION (PWM). Chapter 6 MULTI-LEVEL CONVERSION. Chapter 7 MULTI-LEVEL DC REINJECTION. Chapter 8 LINE-COMMUTATED CSC TRANSMISSION. Chapter 9 DEVELOPMENTS IN LINE COMMUTATED HVDC SCHEMES. Chapter 10 VSC TRANSMISSION. Chapter 11 MULTI-LEVEL VSC AND CSC TRANSMISSION. REFERENCES.

Conceptual survey of Generators and Power Electronics for Wind Turbines

Abstract: This report presents a survey on generator concepts and power electronic concepts for wind turbines. The report is aimed as a tool for decision-makers and development people with respect to wind turbine manufactures, utilities, and independent system operators as well as manufactures of generators and power electronics. The survey is focused on the electric development of wind turbines and it yields an overview on: State of the art on generators and power electronics; future concepts and technologies within generators and power electronics; market needs in the shape of requirements to the grid connection, and; consistent system solutions, plus an evaluation of these seen in the prospect of market needs. This survey on of generator and power electronic concepts was carried out in co-operation between Aalborg University and Risoe National Laboratory in the scope of the research programme Electric Design and Control. (au)