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Renewable energy sources play a crucial role in the provision of power supply in active distribution networks. In networks that rely on renewable energy sources, it may become imperative to curtail the power generated by such units due to a variety of factors. The curtailment of renewable energy generation can be attributed to various factors such as overgeneration, voltage limitations at the network bus, and power limitations at the network line. As per the specified parameters, it is possible for the power generation of renewable units to exceed the load consumption at certain intervals throughout the operational duration. Hence, it is essential to devise a solution that mitigates the frequency and duration of power generation curtailments of renewable units. It is feasible to redistribute overgeneration of renewable energy sources from periods of excess to periods of insufficient capacity to meet demand. This study demonstrates that the provision of power to loads from the sub-distribution substation experiences a reduction in power supply and cost. It is feasible to transmit surplus power from a single bus to multiple other buses. The term used to refer to the ability to transfer power across different locations and time periods is known as spatiotemporal flexibility. The presence of data centers in distribution networks enables a reduction in costs and the frequency of power interruptions associated with renewable energy sources, through the utilization of spatiotemporal flexibility. The objective of this paper is to present a methodology for achieving temporal and spatial flexibility in data centers, with the aim of minimizing costs and curtailing the output generation of renewable energy units. Undoubtedly, this approach can also be executed by incorporating mobile batteries; however, it is noteworthy that mobile batteries entail additional costs on the network. Consequently, the implementation of the spatiotemporal flexibility approach in data centers has been adopted as a substitute for the utilization of mobile batteries. This approach, also referred to as virtual battery, effectively eliminates the costs associated with the use of mobile batteries. This study examines overgeneration of renewable units, bus voltage limitations, and line power restrictions on the standard IEEE 33-bus network. Three scenarios are considered, each involving changes in data center power in response to varying load profiles. The implementation of equitable power distribution across data centers, both in terms of temporal and spatial dimensions, as well as the adoption of flexible spatiotemporal flexibility scenario for data centers, have been observed. The findings of this study indicate that the approach employed in this paper leads to a decrease in costs and the output power of renewable units in the examined scenarios. The implementation of spatiotemporal flexibility mode has resulted in a reduction of power supply expenses ranging from 12 to 37 percent when compared to the basic case. Ultimately, the sensitivity analysis pertaining to the placement of data centers and the associated uncertainty index is presented. • Implementing a model of spatiotemporal flexibility within data centers to function as a virtual storage device. • The curtailment of power generation in renewable energy units has been executed under three different distinct circumstances. • The robust optimization method has been employed to demonstrate the uncertainties inherent in the operation problem. [ABSTRACT FROM AUTHOR]

Abstract Along with the advent of restructuring in power systems, considerable integration of renewable energy resources has motivated the transition of traditional distribution networks (DNs) toward new active ones. In the meanwhile, rapid technology advances have provided great potentials for future bulk utilization of generation units as well as the energy storage (ES) systems in the distribution section. This paper aims to present a comprehensive review of recent advancements in the operation of active distribution systems (ADSs) from the viewpoint of operational time-hierarchy. To be more specific, this time-hierarchy consists of two stages, and at the first stage of this time-hierarchy, four major economic factors, by which the operation of traditional passive DNs is evolved to new active DNs, are described. Then the second stage of the time-hierarchy refers to technical management and power quality correction of ADSs in terms of static, dynamic and transient periods. In the end, some required modeling and control developments for the optimal operation of ADSs are discussed. As opposed to previous review papers, potential applications of devices in the ADS are investigated considering their operational time-intervals. Since some of the compensating devices, storage units and generating sources may have different applications regarding the time scale of their utilization, this paper considers real scenario system operations in which components of the network are firstly scheduled for the specified period ahead; then their deviations of operating status from reference points are modified during three time-intervals covering static, dynamic and transient periods. Highlights • A survey of operational methods of active distribution systems (ADSs) is presented. • A two-stage time-hierarchy methodology is adopted to categorize recent research. • Day-ahead economic management of ADSs is explored in the first stage. • Static, dynamic and transient operations of ADSs are studied in the second stage. • Modeling and control needs of ADS economic/technical operation are reviewed. [ABSTRACT FROM AUTHOR]

This paper brings together several contemporary topics in energy systems aiming to provide a literature review based reflection on how several interrelated energy systems can contribute together to a more sustainable world. Some directions are discussed, such as the improvement of the energy efficiency and environmental performance of systems, the development of new technologies, the increase of the use of renewable energy sources, the promotion of holistic and multidisciplinary studies, and the implementation of new management rules and "eco-friendly and sustainable" oriented policies at different scales. The interrelations of the diverse energy systems are also discussed in order to address their main social, economic and environmental impacts. The subjects covered include the assessment of the electricity market and its main players (demand, supply, distribution), the evaluation of urban systems (buildings, transportation, commuting), the analysis of the implementation of renewable energy cooperatives, the discussion of the diffusion of the electric vehicle and the importance of new bioenergy systems. This paper also presents relevant research carried out in the framework of the Energy for Sustainability (EfS) Initiative of the University of Coimbra, linking the reviewed areas to the multidisciplinary approach adopted by the EfS Initiative. To conclude, several research topics that should be addressed in the near future are proposed. [ABSTRACT FROM AUTHOR]

The energy sector is undergoing substantial changes in order to promote better efficiency, increase the use of renewable energy, reduce emissions and effectively deploy technologies to trade off costs and benefits One emerging solution is the application of the Power-to-Gas technology, which can be used for different purposes. In recent years, Power-to-Gas has been studied to understand the role it could play in the electrical system. This paper has the aims of analysing the existing literature about the Power-to-Gas technology in detail, by considering some solutions that have a direct impact on the electrical system (in particular electrolyser and CO 2 production) and applications in the different sectors of the electricity value chain (i.e., generation, transmission, distribution and utilisation). This paper sets out the conceptual aspects that are necessary to include Power-to-Gas facilities in a more comprehensive analysis framework of the operation of the electrical system in various sectors. Some perspectives concerning new Power-to-Gas applications are also presented for each sector, and some promising aspects that are expected to play a relevant role in the future technical and economic evolution of electrical systems are discussed. [ABSTRACT FROM AUTHOR]

The concept of microgrid has emerged as a feasible answer to cope with the increasing number of distributed renewable energy sources which are being introduced into the electrical grid. The microgrid communication network should guarantee a complete and bidirectional connectivity among the microgrid resources, a high reliability and a feasible interoperability. This is in a contrast to the current electrical grid structure which is characterized by the lack of connectivity, being a centralized-unidirectional system. In this paper a review of the microgrids information and communication technologies (ICT) is shown. In addition, a guideline for the transition from the current communication systems to the future generation of microgrid communications is provided. This paper contains a systematic review of the most suitable communication network topologies, technologies and protocols for smart microgrids. It is concluded that a new generation of peer-to-peer communication systems is required towards a dynamic smart microgrid. Potential future research about communications of the next microgrid generation is also identified. [ABSTRACT FROM AUTHOR]

This paper presents a taxonomical survey on distributed generation (DG) planning from the distribution power system performances viewpoint. The distribution power system performance indices such as minimization of real power loss index, minimization of reactive power loss index, improvement of voltage profile index, short circuit current capacity index, System Average Interruption Duration Index ( SAIDI), and Customers Average Interruption Duration Index (CAIDI) are consider in this work as major issue in distribution power systems. Such performances can enhance by conventional/traditional devices as well as DG technologies planning such as fuel cell, bio gas, wind turbine, photovoltaic, solar, geo-thermal, tidal and wave etc. In this paper also presents the current status of DG planning in the distribution power systems from the distribution power system performances viewpoints. This survey article is very much useful for scientific person, engineer, industrial person and researchers regarding with DG planning in the distribution power systems from the power system performances viewpoints. [ABSTRACT FROM AUTHOR]

In a general microgrid (MG), a step-up distribution transformer is used to facilitate integration of the low-voltage (LV) AC microgrid into a medium-voltage distribution system. On the other hand, isolation transformers are placed between distributed energy resources (DERs) (e.g. non-renewable/renewable energy resources and energy storage devices) and common AC buses/lines to eliminate DC-current components and to configure 3-phase & 4-wire, 3-phase & 3-wire, 1-phase & 2-wire, or 1-phase & 3-wire AC microgrids. When all neutral points of isolation transformers are grounded through a unique grounding system of the step-up distribution transformer, a uni-grounded AC microgrid structure is configured. This paper not only mentions advantages and shortcomings of the uni-grounded LVAC microgrid operation, but also investigates its transient operation characteristics. Transient simulation results of the uni-grounded LVAC MG are surveyed through various fault situations and operation transition tests between the grid-connected mode and the islanded mode of the microgrid. Available fault protection methods of a uni-grounded LVAC microgrid are considered. Transient simulation results from PSCAD software are used to validate the fault protection solutions developed for the uni-grounded LVAC microgrid. Last, a generalised fault protection system of uni-grounded LVAC microgrids is proposed in the paper. [ABSTRACT FROM AUTHOR]

The intuition of the power distribution system is to supply good quality of power to the customers with cost-effectively and environment friendly. Renewable energy resources (RES) are integrated in the distribution system to meet out the variable load demand with the decarbonizing effect. With the inclusion of RES, the operation of Distribution Network (DN) has become more complex. This paper describes the state of art in various load flow methods used to analyze the parameters in DN. This paper emphasizes upon the various challenges of DN with the integration of RES. It reviews the various pricing methodologies for the delivered power in DN elaborately. The importance of Demand Side Management (DSM) and energy storage in DN are explored in this paper. The analysis of nodal voltages in the DN with Solar PV, Storage, PHEV and Diesel sources is demonstrated on IEEE four node test feeder. [ABSTRACT FROM AUTHOR]

In the countries such as Pakistan, for analyzing the losses and techniques in the power distribution and for mitigating, are the two active areas of research which is spread globally for increasing the accessibility of power irrespective of installing future generation equipment. As, the Technical Loss and the Non-Technical Loss are accounted by the total energy losses. They both are also referred as TL and NTLs. In terms of the non-technical losses there are major financial losses for the utility companies present in the countries that are in the developing stage. NTLs is the major cause for the additional losses and also it includes the part of damaging the network that includes the infrastructure and network reliability reduction. This paper is subjected to investigating the non-technical losses in terms of the power distribution systems. In addition to that, the consumer energy consumption information is used for analyzing the NTLs from Rawalpindi region from the different feeder source. The data of Low Voltage (LV) of the distribution network are focused more that consists of commercial, industrial, residential and agricultural consumers by the use of KWh interval data which is captured over a month using the smart meter infrastructure. The discussion of this review paper determines analysis and prevention techniques of NTLs to safeguard from the illegal use of the electricity in the distribution of electrical power system. [ABSTRACT FROM AUTHOR]

A reliability of electrical energy supply could be disrupted by the build-up of space charge distribution within or on the surface of insulator. Preventive measures have been carried out since the earliest days of power transmission network invented till today to alleviate the space charge effect on electrical energy systems. Although the preventive measures have been taken greatly, there are inevitable factors especially environmental conditions that lead to the accumulation of space charge. Space charge which carries energy such as kinetic, heat and other forms is believed released these energies during the space charge accumulation process and subsequently distort the local electric field. Despite the numerous papers published on space charge investigation in polymeric insulation, there is an absence of thorough review papers on this topic as well as space charge effects on glass insulation. Hence, this paper provides a summary of charge distribution measurement within and on the surface of insulators along with a new approach to measure the space charge distribution on the surface of glass insulator strings. This knowledge will provide a contribution to the development of a new online space charge distribution measurement system for glass insulator string that will be more efficient, by utilizing the available technology for data transmission. This new approach also has the capability to monitor the condition of the insulator while energized and in service, thus the faulty insulators can be replaced without disrupting the distribution of electrical energy around the world. [ABSTRACT FROM AUTHOR]

Optimal expansion of medium-voltage power networks because of load growth is a combinatorial problem which is important from technical and economic points of view. The planning solutions consist of installation and/or reinforcement of high voltage/medium voltage (HV/MV) substations, feeder sections, distributed generation (DG) and storage units to expand the capacity of the network. The cost objective function of the system should be minimized subject to the technical constraints. Due to the complicacy and the complexity of the problem, it should be solved by modern optimization algorithms. In this paper, the most famous optimization algorithms for solving the distribution network planning problem are reviewed and compared, and some points are proposed to improve the performance of the algorithms. In order to compare the algorithms in practice, and verify the proposed improvement points, the numerical studies on three test distribution networks are presented. The results show that every algorithm has its own advantages and disadvantages in specific conditions. However, in general manner, the hybrid Tabu search/genetic algorithm (TS/GA) and the improved particle swarm optimization (PSO) algorithm proposed in this paper are the best choices for optimal distribution network planning. [ABSTRACT FROM AUTHOR]

Renewable energy technique is gaining more interest due to increasing demand and threat zero carbon foot prints. The energy from wind has a high potential as a source of energy. The growing demand of wind energy tends to produce a quality output power in terms of grid integration. An appropriate controller is required to control the power produce by the wind energy. A decent number of research publications reports had reviewed maximum power point tracking (MPPT), grid side controller (GSC) and machine side controller (MSC) associated with wind energy conversion system (WECS). However survey on pitch angle based control has not been focused exclusively in any such reviews. A concise review of pitch angle controller, maximum power extraction control and grid synchronisation controller is analysed in this paper. Thus, this paper presents a comprehensive review of overall control strategies for wind energy conversion control. The review paper is intended to provide a suitable reference for further research in the field of wind energy. [ABSTRACT FROM AUTHOR]

Smart grid engineering is the key for a beneficial use of widespread energy resources, it is a modernized electrical grid that uses analog or digital information and communications technology. Renewable energy itself a thrust area of research due to its availability, applicability and environmental friendly nature and the application of smart grid in renewable energy makes it vast and more promising. This fusion enables the efficient use of renewable energies which is a key challenge for now. The present review paper attempts to investigate the role of smart grid in the renewable energy. The introductory section sets the role of renewable energy and distributed power in a smart grid system. Subsections cover the concept and availability of renewable energies, renewable energy power calculation formulae, smart grid concepts and its feasibility, case studied as performed by different researchers around the World, discussion and future recommendations and finally the conclusions from the study. To achieve this, articles from different sources such as internet, reports, conferences and journals of Elsevier, Springer, Tailor and Franacis, Wiley and many more have been collected and reviewed. This paper concludes that renewable energies can be used efficiently and in a smart way by using the smart grids. However, the smart grid technology is not mature enough and needs more research on the same. [ABSTRACT FROM AUTHOR]

Energy storage (ES) is an important device to ensure operation stability and efficiency of a renewable energy based distributed energy generation (DEG) system. As such, many researchers have modelled the operation (scheduling) of energy storage in a DEG system, where it is mostly portrayed to operate on a daily cycle. In this paper, an analysis of the operation mode of energy storage is presented. Two modes of operation are defined, daily mode (DM) (ES operates in daily cycles) and weekly mode (WM) (ES operates in weekly cycles) which are modelled accordingly. This paper then attempts to analyse and compare between both modes in term of operation and cost. The analysis is performed through a mixed integer linear programming (MILP) model programmed via the General Algebraic Modelling System (GAMS). In general, with high capital cost of ES, it is advisable to program the ES to operate in a DM. The reason to this conclusion is mainly due to three factors, intermittency of renewable resources, varying weather conditions, and discharge rate of ES(s). [ABSTRACT FROM AUTHOR]

The hydrokinetic energy conversion system has capabilities to supply inevitable and secured power which is obtained from free stream like ocean, river, and man-made channel etc. So far, researchers have done different work on resource availability, design parameter, electricity generation cost, reactivity of plant, its impact on environmental separately. In this paper an attempt is made to review the technology, performance, design optimization, reliability, techno-economic analysis and environmental impact of the hydrokinetic energy conversion systems altogether to establish the relationship between the above said aspects towards the viability of power project. After conducting these reviews it has become clear that in order to avoid cavitation, coefficient of pressure should be less than cavitation coefficient especially at leading edge of hydrokinetic turbine blade. Moreover, to avoid stall and separation, angle of attack should be kept as less as possible. By implementing hydrofoil blade profile, performance of the hydrokinetic turbine can be improved. Sometimes, implementation of double blade hydrofoil may be beneficial and increase the coefficient of lift more than that of the single blade hydrofoil. Apart from the above considerations it is to be noted that deployment of turbine near bed level should be avoided as it brings down available power, increase hydrodynamic loading, turbulence level, and fouling by sediments. Moreover to increase the performance arm and end plate can be incorporated in hydrokinetic turbine design. It is also observed that hybrid conversion system is also viable in order to reduce power generation cost. This paper will help researchers to identify areas of design parameter of hydrokinetic turbine that need to improve and encourage the project developer, funding and financial institution, policy maker or government officials, and local community, to provide knowledge about hydrokinetic energy conversion system for executing the project and compete with the existing market. [ABSTRACT FROM AUTHOR]

This review paper is focused on the impact of distributed generation (DG) on distribution system protection. The integration of DG is transforming the traditional radial distribution system into a multi-source system that requires protection that is capable of maintaining proper coordination under bi-directional and variable power flow conditions. The multiple types of DGs with different short circuit characteristics mean that the protection must also be effective under conditions of unpredictable fault currents. New grid code requirements demand that DGs remain connected under fault conditions to provide grid support and improve system reliability and security of supply. A discussion is given of the traditional protection techniques for the distribution system and the shortcomings of such techniques when DGs are integrated into the system. The paper also presents a wide survey and review of recent techniques proposed by various researchers to mitigate the effects of DG integration on the performance of distribution system protection. Centralised and distributed techniques have been proposed that include deployment of intelligent smart devices and communication systems to enhance and provide novel ideas for solving the protection problem. The implementation challenges of these techniques are discussed and proposals for the future given. [ABSTRACT FROM AUTHOR]

Diffusion of Renewable Energy Technologies (RETs) governs by the status of technology in terms of efficiency and techno-economical feasibility. The states plan for the deployment of resources for the development with special reference to sustainable environment. The demand and supply energy model help to provide more focus on the long term goals. The theory of diffusion modeling allows analysis of diffusion processes and study of growth rates of different technologies and underlying diffusion factors of the particular states, particularly for Indian 8 National Missions implication factors concerning to National Action Plan for Climate Change (NAPCC). The Energy Management Systems (EMS) and Distribution Management Systems (DMS) provide control on hybrid sources of energy generation and distribution over on-grid and off-grid applications. Energy Distributive system model for adequate accurate predictive analysis plays important role for sustainable country energy resources, in consideration of all influential factors in energy generation and distribution. For prediction aspects the important parameters are geographical location, seasonal influence, effect of climate change and state or area concession. With the abundant data and relative economic indicator, energy prediction is performed with close loop predictive system based of timing algorithm. The energy economics in free trade market like India, where the peak load varies abruptly due to season and community demand, its hourly prediction model is more useful. The energy model provides the estimation and prediction of hybrid power generation in consideration of the parameters on resource potential, technology, efficiency and consumption pattern. The monitor, statistical and prediction model with inbuilt mechanism for renewable energy certificate (REC) and perform, achieve and trade (PAT) incentives are explored in this paper. The paper presents energy models to enhance knowledge and skills in the efficient transfer and management of technology for optimally allocating different types of renewable resources, technology and economic feasibility. [ABSTRACT FROM AUTHOR]

Recent improvements in computer processing power have enabled the development of intelligent electronic devices (IEDs) to be capable of interpreting a substantial quantity of data at high speeds. The distribution industry is one of the largest users of real-time data during the operation of their energy distribution network and as such, has an inherent need for data processing technology. The development of intelligent devices and communication protocols has given rise to the concept of distribution system automation (DSA). In this paper the major features of DSA development are discussed. A method of communication along with the integration of wired and wireless communication solutions with IED and Mote technology is described. Protection scheme automation is investigated, showing that automated response to network fault conditions is possible. Network reconfiguration is another key aspect of DSA research and two distinct calculation techniques are discussed. The current index (CI) and the load balance index (LBI) calculation methods are presented and the benefits of LBI are highlighted. Distributed generation (DG) is addressed in the context of automation with a demand side management (DSM) program proposed to manage load during peak and off-peak periods. The paper discusses switching DG sources, load deferral strategies and direct load control to effect a reduction in load during peak periods. The paper furthers this load management by load filling during off-peak periods. Finally, conclusions on the effectiveness of the proposed method are drawn and recommendations are made for further research. [ABSTRACT FROM AUTHOR]

Microgrids are a suitable, reliable and clean solution to integrate distributed generation into the mains grid. Microgrids can present both AC and DC distribution lines. The type of distribution conditions the performance of distribution line and implies different features, advantages and disadvantages in each case. This paper analyses, in detail, all this parameters for AC and DC microgrids in order to identify and describe the available alternatives for building and configuring a microgrid. Elements and issues involved in the implementation and development, such as protections, power converters, economic analysis, and availability are discussed and described. This analysis constitutes a tool for selecting a suitable configuration of a microgrid adapted to the needs in each situation. In addition, the paper provides a picture of the current situation of microgrids, and identifies and proposes future research lines. [ABSTRACT FROM AUTHOR]

For decades, Ghana’s economy has been fuelled by abundant inexpensive hydropower. As a developing economy, Ghana’s electricity demand has long been relatively low, though rising in recent times due to increasing economic growth, urbanization and industrial activities. However, the rapid demand growth, as well as periodic hydrological shocks, leaves the country increasingly reliant on expensive oil and gas-based generation power plants, with a resultant drain on the national economy. The main electricity generation company, the Volta River Authority, is not able to generate enough electricity for all the demand sectors. The electricity supply-demand margins - the difference between peak demand and available supply - of the country fall short of the recommended engineering practice and thus presents a high supply security risk. The country has been experiencing an increase in the frequency of power cuts over the last ten years. It is clear that Ghana will have to expand and diversify its generation capacity in order to improve supply security. This paper provides a review of the assessed potential renewable energy resources, their current exploitation status, and their potential contribution to the electricity supply of the country. The paper also presents the barriers to their utilization and the existing policy and regulatory instruments to overcome those barriers, plus the current and expected future impacts of these instruments. The results show that Ghana has several RES, such as wind, solar PV, mini hydro and modern biomass that can be exploited for electricity production. While their exploitation for electricity generation is currently very low, providing just 0.13% of the country’s generation, the review shows a great potential for RES generation to increase substantially over the next decade, looking at the government commitment and legal frameworks that are being put in place. [ABSTRACT FROM AUTHOR]

Abstract: The effectiveness and cost-effectiveness of two main types of instruments (feed-in tariffs and quotas with tradable green certificates) have usually been compared in the literature on renewable electricity promotion. Due to negative past experiences with a third instrument (auctions), this instrument has been broadly dismissed in academics and, until recently, also in policy practice. However, and based on an in-depth review of experiences with auction schemes for renewable electricity around the world, this paper argues that some of the problems with auctions in the past can be mitigated with the appropriate design elements and that, indeed, auctions can play an important role in the future implementation of renewable electricity support instruments around the world. The paper provides a proposal for the coherent integration of several design elements. [Copyright &y& Elsevier]

Abstract: Hybrid energy systems are being utilized for supplying electrical energy in urban, rural and remote areas to overcome the intermittence of solar and wind resources. A hybrid renewable energy system incorporates two or more electricity generation options based on renewable energy or fossil fuel unit. The techno-economic analysis of the hybrid system is essential for the efficient utilization of renewable energy resources. Due to multiple generation systems, hybrid system analysis, is quite complex and requires to be analyzed thoroughly. This requires software tools for the design, analysis, optimization, and economic viability of the systems. In this paper, 19 softwares with their main features and current status are presented. The softwares studied are HOMER, Hybrid2, RETScreen, iHOGA, INSEL, TRNSYS, iGRHYSO, HYBRIDS, RAPSIM, SOMES, SOLSTOR, HySim, HybSim, IPSYS, HySys, Dymola/Modelica, ARES, SOLSIM, and HYBRID DESIGNER. The research work related to hybrid systems carried out using these softwares at different locations worldwide is also reviewed. The main objective of the paper is to provide the current status of these softwares to provide basic insight for a researcher to identify and utilize suitable tool for research and development studies of hybrid systems. The capabilities of different softwares are also highlighted. The limitations, availability and areas of further research have also been identified. [Copyright &y& Elsevier]

Abstract: Islanding detection of distributed generations (DGs) is one of the most important aspects of interconnecting DGs to the distribution system. Islanding detection techniques can generally be classified as remote methods, which are associated with islanding detection on the utility sides, and local methods, which are associated with islanding detection on the DG side. This paper presents a survey of various islanding detection techniques and their advantages and disadvantages. The paper focused on islanding detection using a conventional and intelligent technique. A summary table that compares and contrasts the existing methods is also presented. [Copyright &y& Elsevier]

Abstract: Traditional power load management in China is featured by power rationing without considering user demand. However, since the 1990s, demand side management (DSM) has been introduced by local governments and enterprises in China to improve terminal power efficiency and optimize resources allocation, and certain breakthrough have already been achieved. Demand response aims at improving the energy efficiency of end-users and achieving emission reduction targets. Based on the development status of power industry and electricity market in China, this paper firstly reviews the three key development stages of traditional DSM, including management content, operation mode and results assessment. Secondly, this paper analyzes the demand side management aimed at energy conservation and emissions reduction, selecting the core elements and key processes influencing terminal power efficiency of DSM development. In addition, DSM safeguard system and incentive mechanism, including political, economic, technical and managerial measures, are further discussed to achieve the aim of energy conservation and emission reduction. Finally, this paper systematically analyzes related policies and regulations proposed by the government, and put forward relative policy recommendations for DSM development in China. [Copyright &y& Elsevier]

Abstract: In 2009, an estimated 585 million people had no access to electricity services in sub-Saharan Africa. Unlike many other regions of the world, under current assumptions, that figure is expected to rise significantly to about 652 million by 2030-an unsustainable and unacceptable situation. Knowing of the intrinsic linkages between access to energy services and development, national governments and regional organisations have identified the urgent need for accelerated electrification rates. Some of the established and emerging concepts, systems and technologies grouped under the term ‘Smart Grids’ may offer an important contribution to achieving universal access to electricity. We argue that these Smart Grid advances may enable sub-Saharan African countries to leapfrog elements of traditional power systems and accelerate and improve electrification efforts. We introduce the notion of Just Grids to reflect the need for power systems to contribute towards equitable and inclusive economic and social development without marginalising the poor. The paper reviews the literature, and identifies specific options that could be implemented in sub-Saharan Africa. After selecting criteria that focus on potential impact as well as requirements for their implementation, a qualitative first-pass assessment of the potential of these options is made. This paper provides support for policy development, and suggests areas for further, more detailed research. [Copyright &y& Elsevier]

Abstract: This paper attempts to present the state of art of research work carried out on the optimal planning of distributed generation (DG) systems under different aspects. There are number of important issues to be considered while carrying out studies related to the planning and operational aspects of DG. The planning of the electric system with the presence of DG requires the definition of several factors, such as: the best technology to be used, the number and the capacity of the units, the best location, the type of network connection, etc. The impact of DG in system operating characteristics, such as electric losses, voltage profile, stability and reliability needs to be appropriately evaluated. For that reason, the use of an optimization method capable of indicating the best solution for a given distribution network can be very useful for the system planning engineer, when dealing with the increase of DG penetration that is happening nowadays. The selection of the best places for installation and the preferable size of the DG units in large distribution systems is a complex combinatorial optimization problem. This paper aims at providing a review of the relevant aspects related to DG and its impact that DG might have on the operation of distributed networks. This paper covers the review of basics of DG, DG definition, current status of DG technologies, potential advantages and disadvantages, review for optimal placement of DG systems, optimizations techniques/methodologies used in optimal planning of DG in distribution systems. An attempt has been made to judge that which methodologies/techniques are suitable for optimal placement of DG systems based on the available literature and detail comparison(s) of each one. [Copyright &y& Elsevier]

Abstract: This paper presents a review of reliability models and methods for estimating renewable energy resources influence on electrical generation availability. These models and methods may be used to evaluate the impacts on the distribution systems reliability of distributed generation integration, especially when they are based on renewable energy sources. For such, the paper presents the main characteristics of renewable resources models that have been developed for wind, small hydro, solar and biomass, and presents the main methods for reliability evaluation of distribution systems with such resources integrated. These evaluation methods may be based on analytical techniques, Monte Carlo simulation or hybrid approaches. The impact of distributed generation on the reliability of electric distribution systems depends mainly on the operational mode and the energy source in which it is based. The most uncertain case is related to generation based on renewable energy of intermittent nature where the generation availability depends on the availability of the energy source and the availability of the generating unit. [Copyright &y& Elsevier]

Abstract: A microgrid is particularly a portion of the power distribution system that comprises distributed generation, energy storage and loads. To be capable of operating in parallel to the grid, as an autonomous power island and in transition modes, microgrids must be robust in controlling the local voltage and frequency, and protecting the network and equipment connected to the microgrid. It also needs to facilitate demand side management and resynchronization. This paper presents a review of existing microgrid test networks around the world (North America, Europe and Asia) and some significantly different microgrid simulation networks present in the literature. Paper is focused on the test systems and available microgrid control options. A summary table comparing and contrasting the existing test systems is presented. The paper is concluded highlighting the worthy findings and possible areas of research that would enhance practical use of microgrid facilities. [Copyright &y& Elsevier]

During recent years, with the advent of restructuring in power systems as well as the increase of electricity demand and global fuel energy prices, challenges related to implementing demand response programs (DRPs) have gained remarkable attention of independent system operators (ISOs) and customers, aiming at the improvement of attributes of the load curve and reduction of energy consumption as well as benefiting customers. In this paper, different types of DRPs are modeled based on price elasticity of the demand and the concept of customer benefit. Besides, the impact of implementing DRPs on the operation of grid-connected microgrid (MG) is analyzed. Moreover, several scenarios are presented in order to model uncertainties interfering MG operations including failure of generation units and random outages of transmission lines and upstream line, error in load demand forecasting, uncertainty in production of renewable energies (wind and solar) based distributed generation units, and the possibility that customers do not respond to scheduled interruptions. Simulations are conducted for two principal categories of DRP including incentive-based programs and time-based programs on an 11-bus MG over a 24-h period and also a 14-bus MG over a period of 336 h (two weeks). Simulation results indicate the effects of DRPs on total operation costs, customer's benefit, and load curve as well as determining optimal use of energy resources in the MG operation. In this regard, prioritizing of DRPs on the MG operation is required. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a review about conventional and renewable energy scenario of the county in quantitative terms of supply, generation and exploitation of available resources. In this energy scenario, the renewable energy share is in the range of a fraction of a percentage compared to total conventional energy supplies, so depicting it as a sector of least significance for government. Main emphasis in this paper has been given on presentation of data about renewable energy (RE) installations in the country, on-going activities, development projects, RE planning and achievements of public sector RE institutions and organizations. At the end some suggestions are given for effective planning and exploitation of RE resources and use of technologies. These suggestions are not only useful for Pakistan but also are equally important for the third world countries to enhance appreciably RE contribution in their total energy supplies of their country. [Copyright &y& Elsevier]

Abstract: Due to increased attention towards clean and sustainable energy, distributed energy (DE) systems are gaining popularity all over the world. Power electronics are an integral part of these energy systems being able to convert generated electricity into consumer usable and utility compatible forms. But the addition of power electronics adds costs to the DE capital investments along with some reliability issues. Therefore, widespread use of distributed energy requires power electronics topologies that are less expensive and more dependable. Use of modular power electronics is a way to address these issues. Adoption of functional building blocks that can be used for multiple applications results in high volume production and reduced engineering effort, design testing, onsite installation and maintenance work for specific customer applications. In this paper, different power electronics topologies are reviewed that are typically used with distributed energy systems. The integrated power electronics module (IPEM) based back-to-back converter topologies are found to be most suitable interface that can operate with different DE systems with small or no modifications. Also the requirements for a hierarchical control structure with standardized power and communication interfaces are addressed in the paper along with some discussion on future design possibilities for the IPEM-based power electronics topologies. It is expected that modular and flexible power electronics and standardized controls and interfaces, will provide commonality in hardware and software for the power electronics interfaces, thus will enable their volume production and decrease their cost share in distributed energy applications. [Copyright &y& Elsevier]

Abstract: The oceans represent a huge energy reservoir. Although today all of the marine power projects are very near from the shore and they are rated at low power, the huge potential of the seas may in a not very distant future bring marine power further into the sea. Also offshore oil and gas exploration is moving into deeper waters and at longer distances from land. New carbon sequestration projects under the seabed are on the way which require a vast amount of electric power consumption. The substitution of offshore power generators by power provided from the grid may have environmental benefits, but the deployment of offshore transmission of bulk electrical power to or from offshore platforms to the electrical grid onshore is a mayor challenge. The main objective of this paper is to focus on trends that can lead to a feasible transmission system in offshore energy systems far from land, and to introduce the technological alternatives which could help to reach that goal. The paper describes the main alternatives and the technical and economical aspects of the transmission of electrical power offshore. [Copyright &y& Elsevier]

In present day scenario, the focus is reallocating towards integration of small and medium scale power plants based on renewable energy sources into the power distribution system. Solar is the fastest growing form of renewable energy and a single phase voltage source inverter is used to interface photovoltaic based plants with the distribution system. The grid integrated inverter has stringent control requirements. A current controller is employed to mitigate the harmonics in the current injected into the grid and regulate the power exchange between the plant and the grid. This paper presents a review of the current control strategies implemented for a single phase grid tied photovoltaic inverter. A comparative performance evaluation of the current control techniques is also presented through simulation and experimental results. [ABSTRACT FROM AUTHOR]

Significant advancements have been made in the past few decades (since the 1980s) on detailed evaluation and quantification of wave resources globally. Larger availability and advances of computational resources have contributed to the utilisation of numerical wave models as powerful tools in climatic and energy studies. This review presents current state-of-the-art numerical tools and their status in the process of wave power assessments. We focus on the evolution of studies undertaken at the European coastline regions and the Black Sea. Although, a number of studies have been successfully developed and implemented in the past contributing to our understanding of the resource, this paper discusses the benefits, limitations and potential for improvement of numerical tools. From the literature, it is evident that different applications and scale may require different models, however, it is also the experience and knowledge of the user, applied in the tuning of a number of parameters that govern the process of wave generation, propagation, and the quality of input parameters that are the cornerstones of a successful model. This review depicted that the use of numerical wave models, depending on specific region and application, offers significant benefits on quantification of coastal zone wave resources which benefit multiple offshore applications and the energy industry. [ABSTRACT FROM AUTHOR]

The evolution of existing electricity grids to smart grids is aimed at accommodating increasing shares of renewable generation thus contributing for the de-carbonization of economy, offering more diversified services to consumers, enhancing different types of markets (energy, capacity, ancillary services) and improving the system's overall efficiency. As the economic characteristics of the electricity sector tend to discourage investments in smart grids, many countries have adopted incentive policies to foster the deployment of new technologies, which vary according to the particular characteristics of each country. Therefore, the design of specific public policies for Brazil must consider not only the motivations involved, but also the existing challenges for the implementation of smart grids and the socio-economic context. Moreover, the relevance of the proposed policies can be seen from different perspectives. This justifies the need to elicit information from multiple stakeholders for decision support purposes. This paper presents and assesses a set of policies identified by different stakeholders as having a potential to foster the development of smart grids in Brazil. The methodology to shape this set of policies consisted of a thorough literature review of international experiences, combined with meetings with experts in several domains. Then, these policies were assessed by applying a Delphi questionnaire aiming at measuring their effectiveness in fulfilling the objectives associated with investments in smart grids. A first conclusion is that all policies were assessed as having a positive impact taking into account each of the objectives, differing only in the priority to be assigned to each one. The policies that were considered more relevant were: "Incentive Policies for Promoting Demand-Side Management, Distributed Generation and Storage", "Regulatory Changes to Foster Innovation in the Energy Sector" and "Regulation of New Business Models". Among the policies with the worst scores, "Mandatory Rollout of Smart Meters" and "Establishing Quality Standards for the Telecommunications Industry" were ranked as the two lower-ranked policies, i.e., they were assigned lower priority under all objectives. [ABSTRACT FROM AUTHOR]

Reliability assessment tools are of crucial importance for planning and modernisation of distribution power systems. In recent years there has been an increased deployment of renewable energy, distributed generation, energy storage, electric vehicle, protection device automation and demand response schemes in the distribution networks. All these technologies contribute in their own way to network reliability. The objective of this paper is to provide a critical survey of the reliability assessment techniques used for the evaluation of distribution networks, emphasising the importance of an increased penetration of distributed energy resources and a more widespread application of control, protection and communication technologies. A detailed analysis and a comparison between different techniques and models used for the reliability assessment will be provided for each technology along with the guidelines for their application. A case study will be used to demonstrate the properties and the modelling procedure of the reliability assessment tools for modern distribution networks. [ABSTRACT FROM AUTHOR]

In spite of the dramatic changes that affected the electricity sector in the last decade across Europe, the governance of the system has not evolved accordingly, and the centralised regulatory framework is still the norm. This paper focuses on the role of governance as a driver for innovation in the power sector: through the assessment of the Italian market and of significant Italian policies, it reflects on the instruments that allow the full integration of Distributed Energy Resources and the creation of distributed grid control systems across Europe. [ABSTRACT FROM AUTHOR]

The ever greater share of renewable energy sources (RES) in the European energy market stresses the transmission grid to its limits with rising frequency. Therefore, there is a pressing need for a spatially and temporally detailed model of the European power system to serve as a basis for investigating the efficient integration of RES. Here we outline a far-reaching description of transmission grid operation and present a review of approaches developed for modeling the physical power flows and the respective congestion management techniques that control them. By this, we hope to equip the interdisciplinary energy research community with a better understanding of power systems and corresponding modeling tools, thus enhancing their respective efforts. Additionally, a literature review and classification of existing studies on these topics is included in the paper as well. The analysis shows that the fundamental modeling components determining power flows across power systems include the electricity market, the inter-zonal power trading and the intra-zonal congestion management models, where a complete incorporation of all of them requires an iterative or multi-level approach. However, due to the high complexity of such an approach, most common and computationally efficient strategies apply integrated approaches using linearized descriptions for the physical flows. [ABSTRACT FROM AUTHOR]

This paper introduces a hybrid strategy for an ideal operation programming of electrical frameworks through minimization of production cost and in addition better usage of renewable energy resources. The hybrid technique is the combined performance of bacterial foraging optimization algorithm (BFOA) and artificial neural network (ANN) technique. Here, the photovoltaic (PV) system, wind turbine (WT) and storage system are considered in micro gird (MG) system. The proposed control strategy is to manage the power flows between the energy sources and the grid. To achieve this point, demand response (DR), customer response, offer priority, DR magnitude, duration, and minimum cost of energy (COE) is determined. The proposed method is implemented in MATLAB/Simulink working platform and compared with the exiting methods such as, genetic algorithm (GA) and artificial bee colony algorithm (ABC) respectively. In the proposed method, the maximum generated power of PV, WT, MT and battery is 7.5 kW, 9 kW, 15.5 kW and 4.5 kW respectively. By using GA, the generated powers are 5.5 kW, 7.5 kW, 11 kW and 3.5 kW respectively. The SOC of the proposed method is analyzed and is about 80%. The proposed method has less cost effective based on their load demand. [ABSTRACT FROM AUTHOR]

In the past decade, energy storage systems (ESSs) as one of the structural units of the smart grids have experienced a rapid growth in both technical maturity and cost effectiveness. These devices propose diverse applications in the power systems especially in distribution networks. Despite offering numerous applications, the ESSs are new devices characterized by high investment costs. Besides technological advancement, optimal ESS planning and scheduling is one of the effective ways to reduce the costs and justifying high investment costs by taking their benefits out as much as possible. During the past few years, various studies have been conducted by the researcher to address the problem of optimal ESS planning in distribution networks. In this context, various models, methods, and considerations have been proposed to enhance the functionality of optimal planning process. The aim of this paper is to review the problem of optimal ESS planning including optimal bus location, power rating, and energy capacity determination in the distribution networks. In order to facilitate continuing and growing research in this field, a comprehensive literature survey and classification of the related studies followed by research gaps and future opportunities is provided. [ABSTRACT FROM AUTHOR]

Locating the source of voltage sags in order to identify the events causing the problem and improving mitigation strategies is a major issue. When two utilities manage interconnected networks or manage a micro grid and an upstream grid, an occurred fault in one area may cause voltage sags that affect sensitive customers/critical loads in another area. From this viewpoint, this paper first reviews and analyses with detail different methods for voltage sag source location. Then eleven generalized method are introduced. A comparative analysis is performed between some of the discussed methods by applying extensive numerical simulations in a Brazilian regional utility by using PSCAD/EMTDC and MATLAB. The location of each monitor represents a difference kind of system topology (radial, interconnected, one source, two sources and interconnected microgrids). In the following, the effectiveness of methods was obtained and comprised for each monitor location and for the whole system.. The results obtained show that the effectiveness of methods based on instantaneous positive sequence components and Clarke's components is equal in many methods except distance relay and resistance sign methods, and that the effectiveness is lower, higher or equal than methods based on positive sequence phasors. The phasor based methods had less effectiveness. The generalized methods based on reactive power using instantaneous positive sequence components and Clarke's components gave the right location in 88% of total simulated cases. The results also provided a comprehensive background to propose future works and to select the best method especially at interconnection point of a micro grid with the presence of renewable distributed energy sources. [ABSTRACT FROM AUTHOR]

China's thermal power industry has gone through the phases of rapid development in the last decade. But the excessive enthusiasm of thermal power investment is making this industry overcapacity. The unbalanced demand-supply relationship in electric power market greatly affects the economic benefit of most thermal power plants. In this paper, we give an overall review of the overcapacity situation of China's thermal power industry, which is supported by latest data. Then, policy orientation and its effect is discussed. It can be found out that policies on the respect of construction scale control, renewable power integration, feed-in tariff reduction and environmental protection were considered as the main solution to relieve the over capacity situation. Finally, we propose three suggestions for the future development of China's thermal industry. [ABSTRACT FROM AUTHOR]

This paper presents a technique for the optimal planning and design of hybrid renewable energy systems for microgrid applications. The Distributed Energy Resources Customer Adoption Model (DER-CAM) is used to determine the optimal size and type of distributed energy resources (DERs) and their operating schedules for a sample utility distribution system. Using the DER-CAM results, an evaluation is performed to evaluate the electrical performance of the distribution circuit if the DERs selected by the DER-CAM optimization analyses are incorporated. Results of analyses regarding the economic benefits of utilizing the optimal locations for the selected DER within the system are also presented. The electrical network of the Brookhaven National Laboratory (BNL) campus is used to demonstrate the effectiveness of this approach. The results show that these technical and economic analyses of hybrid renewable energy systems are essential for the efficient utilization of renewable energy resources for microgrid applications. [ABSTRACT FROM AUTHOR]

Electricity consumption data is regarded as nonlinear, non-stationary series, and is often made up by a superposition of several distinct frequencies. Thus most of the conventional approaches currently employed for the modeling and forecasting involve great complexity and uncertainty. Recently, fluctuation characteristic analysis has increasingly become essential step in the application of electricity demand forecasting, yet the implementation of this analysis is an inherently difficult task. To obtain reasonable accuracy and stability in the modeling, there has been the tendency to accommodate multidimensional attributes of the consumption demands with decomposition based approach in terms of more advanced and hybrid form. And the decomposition can be achieved through utilization of two different procedures, namely component model-based and frequency domain analysis-based decomposition. Consequently, a comprehensive review and summarization of decomposition based approach for the prediction is conducted in this paper. More specifically, the issues of demand forecasting classification, the dependency between the electricity demand and external indicators, features of various decomposition approach, as well as the unique fluctuation characteristic of electricity demand at different time scales are discussed. In addition, future research directions of the decomposition based prediction approach are outlined. [ABSTRACT FROM AUTHOR]

Distributed energy storage systems (ESSs) are becoming essential components for the operation of the increasingly complex electricity grid, where dispersed generation is causing power-flows occurring both top-down and bottom-up. Specifically, the combination of ESSs coupled with application-specific control methods can achieve the interdependent objectives of system stakeholders such as the system operator, electrical utilities, retailers, equipment vendors, the government and the electricity customers. The necessity for an accelerated rate of transition to a multi-directional grid arrangement has been exacerbated by the rapid proliferation of distributed renewable energy sources (RESs) that are now price comparable to traditional supply sources. While there are review articles covering ESS technologies and applications as well as the plethora of future advanced grid arrangements that may eventuate, there is none which comprehensively covers individual and aggregated ESS applications and the corresponding benefits, comparing different technology selection methods and providing application-specific controls. Both operational and monetary benefits are identified and critically reviewed from the perspective of the aforementioned stakeholders. Wholesale and retail energy market regimes are also considered for monetisation of the benefits. The control methods that are provided cover both balanced and unbalanced grid conditions. This comprehensive review paper will be of immense value to researchers and practitioners seeking to understand and unpack the aggregated benefits of ESS in the electricity grid. [ABSTRACT FROM AUTHOR]

In operational and planning studies in power electric distribution systems, one of the most important tasks is to quantify the evolution of the system. In particular, it is necessary to be able to measure the growth of electrical demand, with special attention to residential consumption. For that reason, it is fundamental to predict its future values. Considering the availability of real measure data, statistic parametric methods are widely used to describe and forecast those residential loads. This paper reviews the principal statistical linear parametric methods and implements four of them to analyse real measure data from Chilean systems. Additionally, those methods are compared among them and the performance of a non-tested continuous approach based on diffusion processes can be evaluated. In each case, the parametric adjustment and the validation methods are explained. [ABSTRACT FROM AUTHOR]

The term smart grid refers to a modernization of the electrical network consisting in the integration of various technologies such as dispersed generation, dispatchable loads, communication systems and storage devices which operates in grid-connected and islanded modes. As a result, traditional optimization techniques in new power systems have been seriously influenced during the last decade. One of the most important technical and economical tools in this regard is the Optimal Power Flow (OPF). As a fundamental optimization tool in the operation and planning fields, OPF has an undeniable role in the power system. This paper reviews and compares the OPF approaches mainly related to smart distribution grids. In this work, the main OPF approaches are compared in terms of their objective functions, constraints, and methodologies. Furthermore, computational performances, case study networks and the publication date of these methods are reported. Finally, some basic challenges arising from the new OPF methodologies in smart grids are addressed. [ABSTRACT FROM AUTHOR]

Energy storage systems (ESSs) are generally planned based on the active power. While, reactive power is another important aspect of the ESSs that has not been adequately addressed and discussed. Moreover, ESSs are often managed individually, but coordinated planning on the ESSs and distributed generators (DGs) may result in more suitable outcomes. In order to address these issues, a coordinated ESS and DG planning is presented in this paper. In the proposed planning, the place and capacity of the ESSs and DGs are determined at the same time. The active and reactive powers are included in the planning for both the ESSs and DGs. In other words, the optimal active and reactive capacities are denoted for both the ESSs and DGs on the network. The proposed coordinated ESS and DG planning is carried out on a radial distribution network under deregulated electricity market. Objective function of the proposed planning is to maximize the profit of distribution company (DISCO) subject to the secure operation of the network. The planning is expressed as a nonlinear, mixed integer optimization problem and solved by advanced PSO as a strong Meta-heuristic optimization technique. Simulation results demonstrate the great impacts of the proposed planning on the network. The results demonstrate the priority of the proposed coordinated DG and ESS planning compared to the individual ESS planning. Additionally, it is verified that considering reactive power of the DGs and ESSs changes the results of the planning and provides more realistic and reasonable outputs. The proposed planning significantly increases DISCO profit while guarantees the safe operation of the network through satisfying several security constraints. [ABSTRACT FROM AUTHOR]

This paper investigates heat pump systems in smart grids, focussing on fields of application and control approaches that have emerged in academic literature. Based on a review of published literature technical aspects of heat pump flexibility, fields of application and control approaches are structured and discussed. Three main categories of applications using heat pumps in a smart grid context have been identified: First stable and economic operation of power grids, second the integration of renewable energy sources and third operation under variable electricity prices. In all fields heat pumps - when controlled in an appropriate manner - can help easing the transition to a decentralized energy system accompanied by a higher share of prosumers and renewable energy sources. Predictive controls are successfully used in the majority of studies, often assuming idealized conditions. Topics for future research have been identified including: a transfer of control approaches from simulation to the field, a detailed techno-economic analysis of heat pump systems under smart grid operation, and the design of heat pump systems in order to increase flexibility are among the future research topics suggested. [ABSTRACT FROM AUTHOR]

Owing to the central role in electricity market operation, researchers have long sought to investigate the price responsiveness of both electricity supply and consumption sides. From the perspective of demand-side management (DSM), electricity prices prediction can be regarded as a pattern recognition problem of classifying future electricity prices with respect to a predefined threshold. From a fresh perspective this paper develops an efficient framework, called TSS-RFE-MRMR based SVM (Time series segmentation, recursive feature elimination, and minimum redundancy maximum relevance based support vector machine), for providing estimates of price fluctuation over certain valuation domains and modeling high-dimensional electricity market price without adopting additional impact factors. It starts from adopting a novel feature space determination scheme, called principal component analysis-dynamic programming (PCA-DP) based time series segmentation. Then, the RFE-MRMR filter for significant features selection is implemented, where both redundant and less relevant features are progressively eliminated among the potential feature sets. To test the performance of the proposed approach, it is evaluated on Ontario and New York electricity markets and compared with other method. Our experimental results indicate that the proposed approach outperforms other traditional method and present a relatively higher prediction accuracy on the electricity price. [ABSTRACT FROM AUTHOR]