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The optimal allocation of protective devices is a serious issue in an electrical power system; in order to reduce the possibility of faults, the protection devices should be optimally placed. The paper presents a continuous genetic algorithm (CGA) for the optimal allocation of directional relays for the efficient energy minimization in a radial distribution system (DG). The algorithm is flexible to use for the changes and improvements in the optimal location for a DG unit and can optimize the energy consumption in the radial distribution system. The proposed algorithm has been implemented on IEEE 33 and 69-bus system using MATLAB (R2014b, MathWorks). Low energy consumption is a common design objective in an energy-constrained distribution system. Engineers, power utilities, and network operators can profit from the proposed methodology to enhance the use of DG in distribution networks. [ABSTRACT FROM AUTHOR]

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Summary: Multicarrier energy systems are increasingly used for a number of applications, among which the supply of electricity, heating, and cooling in buildings. The possibility of switching between different energy sources is a crucial advantage for the optimal fulfillment of the energy demand. The flexibility of these systems can benefit from the integration with smart grids, which have strong variations in time during their operation. The energy price is the parameter that is usually considered, but also the primary energy factor and the greenhouse gases emissions need to be accounted. This paper presents an application of an operational optimization method for a multicarrier energy system, based on real data–driven model and applied to different countries. The generation plant of a hospital is considered as case study, coping with multiple energy needs by relying on different conversion technologies. The optimal operation of the system shows a wide range of variability, depending on the chosen objective function, the hour of the day, the season, and the country. The results are affected mostly by the energy mix of the electricity supplied from the power grid, which has a direct influence on the primary energy consumption and the greenhouse gases emissions and an indirect influence on the electricity prices. [ABSTRACT FROM AUTHOR]

Using forest-based biomass to produce bio-energy and bio-fuels could provide economic, environmental, and social benefits for communities. However, variability in biomass availability and high cost of delivered feedstock impact the profitability of the supply chain. Therefore, optimization models were developed in previous studies to design cost effective and profitable biomass-based supply chains at strategic level. Medium term variations in biomass supply and demand are not usually accounted for in strategic models. This may affect the feasibility of strategic plans prescribed by the optimization model at tactical level. To solve this issue, an integrated model is developed in this paper that includes strategic and tactical decisions simultaneously in order to optimize forest-based biomass supply chains. In addition to yearly variations in biomass supply, which can occur due to changes in harvest level, monthly variations in biomass availability, bioenergy/biofuels demand, and losses during preprocessing and storage of biomass are incorporated in the model. Other unique features of this model compared to the few integrated models developed in previous studies are as follows. (1) Decision regarding opening a new conversion facility is made yearly, not just at the beginning of the planning horizon. (2) A multi-product (heat, electricity, bio-oil and pellets) supply chain is considered. (3) The impact of fossil-based energy prices on bio-conversion investment decisions are accounted for in the model. (4) The optimization problem is modeled in a way that the global optimum solution is obtained within a reasonable time. Using a case study in Interior British Columbia, it is shown in the paper that the capacity of conversion technologies and the amount of procured biomass prescribed by the strategic model would not be sufficient to meet the monthly demand of bioenergy. Moreover, the net present value of the strategic model is overestimated due to underestimating the demand and procurement cost, and ignoring storage costs. It is shown that these issues are resolved using the integrated model. [ABSTRACT FROM AUTHOR]

This paper proposes a novel multiphase transformer connection scheme which converts three phase balanced AC input to seven phase balanced AC output. Generalized theory to convert a three phase utility supply into any number of phases is presented. Based on the proposed generalized principle, a three phase to seven phase power converting transformer design is presented with connection scheme, analysis and simulation and experimental results of the proposed three phase to seven phase conversion transformer. The proposed transformer in this paper is analyzed and compared with the connection scheme for seven phase available in the literature. The connection scheme is found to have higher power density, lower core area and lower core requirement as compared to the available connection scheme of the same rating. Impedance mismatching between different phases of the transformer is observed in the three phase to seven phase transformer available in the literature. As this mismatching introduces error in study of per phase equivalent circuit diagrams as well as imbalance in voltage and currents. The present design also addresses the impedance mismatching issue and reduces mismatching in the proposed transformer design. A prototype of the proposed system is developed and waveforms are presented. The proposed design is verified using simulation and validated using experimental approach. [ABSTRACT FROM AUTHOR]

As one of the most successfully commercialized distributed energy resources, the long-term effects of microturbines (MTs) on the distribution network has not been fully investigated due to the complex thermo-fluid-mechanical energy conversion processes. This is further complicated by the fact that the parameter and internal data of MTs are not always available to the electric utility, due to different ownerships and confidentiality concerns. To address this issue, a general modeling approach for MTs is proposed in this paper, which allows for the long-term simulation of the distribution network with multiple MTs. First, the feasibility of deriving a simplified MT model for long-term dynamic analysis of the distribution network is discussed, based on the physical understanding of dynamic processes that occurred within MTs. Then a three-stage identification method is developed in order to obtain a piecewise MT model and predict electro-mechanical system behaviors with saturation. Next, assisted with the electric power flow calculation tool, a fast simulation methodology is proposed to evaluate the long-term impact of multiple MTs on the distribution network. Finally, the model is verified by using Capstone C30 microturbine experiments, and further applied to the dynamic simulation of a modified IEEE 37-node test feeder with promising results. [ABSTRACT FROM AUTHOR]

Distribution system is considered as one of the leading part of an electrical power grid structure and it is gaining more importance especially in smart grid concept. The mature structure of distribution systems is evolving due to the high penetration of distributed generation (DG) sources. Conventional protection schemes in distribution systems are prone to potential threats with increasing number of DG units. The characteristics of DG systems such as wind and solar energy conversion systems are generally uncertain in nature. These units add complexity to conventional protections schemes in terms of directional protection challenges. Besides, the integration of DG units to grid results in availability of new local energy sources in the points where loads are connected. Thus, misoperations and imperfect selectivity of relays can occur within the distribution system. These issues call for the need of a bi-directional relay operation and an operation strategy where adaptive protection and relay coordinations are applied in new distribution systems compatible with smart grid necessities. In this paper an adaptive protection scheme is proposed for distribution systems with DG. Simulation results on a modified Institute of Electrical and Electronics Engineers (IEEE) 4-node distribution system show that the proposed algorithm can perform adaptive relay coordination under various fault conditions. Compared with the conventional protection structure, relay coordination of adaptive protection scheme provides fast fault isolation and greater adaptation to different operating modes considering DG units. [ABSTRACT FROM AUTHOR]

This work analyzed the environmental compatibility of a biomass plant to be constructed to produce both electricity and heat (bioenergy) in a small town in Piedmont (northern Italy). In order to study both the critical local impacts (with specific reference to air quality) and the overall environmental benefit (decrease of GHG generation), we evaluated the emissive flow modifications for the hypothesis of activating the biomass plant in the municipal area, by considering introduced and eliminated pollutant loads. This analysis included a consideration of the non-energy-related emissions (“ground value”) currently operating in the area. After carefully analyzing the major operational characteristics of the proposed plant and the principal characteristics of the surrounding territory and its energy needs, the evaluation was conducted using the tools of mass and energy balances, and an external costs methodology was also applied in order to define the social cost of the plant. In addition, the plant′s potential modification to local air quality was evaluated by considering the meteorological and physical characteristics of the considered area, using a pollutant dispersion model. Several different configurations for the flue gas purification line were also considered, so that the evaluation of the costs and benefits was based on the analysis of both industrial and external costs. The conclusions, while based only on the specific studied case, can be considered to be fairly representative in general as a methodological approach for studying the effects of the implementation of biomass energy plants. [ABSTRACT FROM AUTHOR]

The substantial increases in the energy consumption during the second half of the last century have amplified the use of fossil fuels in various economic sectors, mainly the power sector. Also, the low-efficient technologies still adopted in many countries have mounted the losses associated with various energy conversion processes to substantial levels. Tasks and challenges associated with transferring power sectors from energy-wasting utilities into advanced smart grid-based utilities are discussed in this article. To transfer the Lebanese dilapidated and aging electrical power sector into a modern economically profitable sector, adopted two major projects have been adopted: the Lebanese Electrical Network Control Center and the Advanced Metering Infrastructure. This article explains the outcomes and impacts of the major components of these two projects; it article also discusses the problems encountered during the implementation process of the Lebanese Electrical Network Control Center, where several original software packages have been modified by the research team to properly integrate the Lebanese Electrical Network Control Center with the aging Lebanese power sector. Finally, the article describes the controlled design project, which also has been implemented as part of the Lebanese Electrical Network Control Center project and highlights problems associated with upgrading the high-voltage transmission lines. [ABSTRACT FROM AUTHOR]

The four-switch three-phase (FSTP) inverter has been proposed as an innovative inverter design to reduce the cost, complexity, size, and switching losses of the dc–ac conversion system. Traditional FSTP inverter usually operates at half the dc input voltage; hence, the output line voltage cannot exceed this value. This paper proposes a novel design for the FSTP inverter based on the topology of the single-ended primary-inductance converter (SEPIC). The proposed topology provides pure sinusoidal output voltages with no need for output filter. Compared to traditional FSTP inverter, the proposed FSTP SEPIC inverter improves the voltage utilization factor of the input dc supply, where the proposed topology provides higher output line voltage which can be extended up to the full value of the dc input voltage. The integral sliding-mode control is used with the proposed topology to optimize its dynamics and to ensure robustness of the system during different operating conditions. Derivation of the equations describing the parameters design, components ratings, and the operation of the proposed SEPIC inverter is presented in this paper. Simulation model and experimental setup are used to validate the proposed concept. Simulations and experimental results show the effectiveness of the proposed inverter. [ABSTRACT FROM AUTHOR]

Wind energy conversion system (WECS) is interfaced with the utility system through power electronic converters which plays an important role in the integration of wind power into the electric grid. The main power quality disturbances due to integration of WECS to grid are variation in power and harmonics. To maintain grid synchronization and to keep total harmonic distortion (THD) within operational limits, appropriate control schemes are required for the grid side converter. The main objective of grid side controller is to control the power delivered to the grid, grid synchronization, to supply high quality power to grid and to meet grid code compliance. In this paper control schemes used in grid interfaced wind energy conversion system for generator side and grid side converter control, are reviewed thoroughly. The paper presents a comparative study of rotor flux oriented control and direct torque control (DTC) techniques applied in generator side converter of permanent magnet synchronous generator (PMSG) drives for wind turbine application. For grid side converter, various control schemes are developed mainly based on voltage oriented control (VOC) or on direct power control (DPC). The performance of VOC based control system basically depends on method applied for current control. A comparative study is done among them and findings are tabulated. Integration requirements of wind turbine to grid, grid synchronization and requirement of monitoring unit are also discussed. [ABSTRACT FROM AUTHOR]

The increasing share of intermittent renewable electricity production leads to operational challenges in the electric power sector. Storage will be needed, among other options, to ensure an efficient and reliable operation of the electric power system. The power to gas (PtG) concept provides a possibility to store excess renewable electric power and as such it can increase the utilisation of RES-based electricity generation. The renewable methane, produced via PtG, can be stored in the gas system and used e.g. for electricity generation. The gas system has a much larger storage capacity compared to current electricity storage technologies. However, PtG introduces extra couplings between the gas, electricity and carbon ( CO 2 ) sector and it is not known what the effect of these new interactions could be. Therefore, an operational model has been developed that includes the gas, electricity and CO 2 sector to analyse the effects of PtG on these sectors and on the interactions between them. Based on a case study, it is found that PtG partially transfers capacity and flexibility problems, triggered by the introduction of intermittent RES-based electricity generation, from the electricity to the gas sector. Moreover, a downward pressure on the gas prices is observed. However, the effects of PtG are generally smaller than those of the large-scale introduction of intermittent renewable electricity generation. Also, complex inter-sector dependencies are introduced through the CO 2 that is required in the PtG process. If PtG is to be deployed at large scale, the study of these effects is relevant for policy makers, regulators, energy markets’ participants and system operators. [ABSTRACT FROM AUTHOR]

This paper presents modeling, control and performance of a DC micro-grid connected to the utility under variable load demand and different environmental conditions. This micro-grid consists of 60 kW wind turbine (WT) energy conversion system, 40 kW photovoltaic (PV) panel and 40 kW fuel cell (FC) module, in addition to, DC and AC loads. The WT energy conversion system is controlled by the indirect field orientation control (FOC) method to extract maximum power from the wind. The PV module is controlled to generate the available maximum power using P&O MPPT control considering environmental conditions. The fuel cell, with a current controlled DC/DC boost converter, supplies power only when the load demand exceeds the total power of the WT and PV systems. A bidirectional 6-pulse PWM converter connects the micro-grid to utility using the natural frame control (NFC) technique. It controls the DC bus voltage, power and reactive power transfer to/from the utility according to the available power from the DG units and the total load demand. The various control algorithms are presented to harness the maximum power from the renewable energy sources at different operating modes. In addition, voltage stability and smooth power transfer between the micro-grid and utility are maintained. [ABSTRACT FROM AUTHOR]

Solid-oxide fuel cells (SOFCs) are unique in their ability to directly convert the chemical energy of a wide variety of fuels to electric power with unmatched energy conversion efficiency. The articles in this issue of MRS Bulletin highlight the enormous potential of, and recent progress toward, operating SOFCs at lower temperatures (<650°C). Lower temperatures dramatically increase the number of potential applications for this technology as well as provide the opportunity to incorporate a wider variety of materials in SOFC power generation systems with greater reliability and lower cost. The articles in this issue describe materials development and processing for low-temperature SOFCs, including the enabling of nanotechnology and microelectromechanical systems-based cell designs, the development of highly active electrodes and their three-dimensional microstructural characterization, as well as the use of novel proton-conducting electrolytes, all of which provide new avenues of research. New fabrication methods are also being applied in the development of micro-SOFCs and microtubular SOFCs with higher power densities. Finally, advances in lowering performance degradation rates, a critical commercialization issue, are described. [ABSTRACT FROM AUTHOR]

Emerging applications such as industrial automation, in-vehicle, professional audio-video, and wide area electrical utility networks require strict bounds on the end-to-end network delay. Solutions so far to such a requirement are either impractical or ineffective. Flow based schedulers suggested in a traditional integrated services (IntServ) framework are O(N) or O(log N), where N is the number of flows in the scheduler, which can grow to tens of thousands in a core router. Due to such complexity, class-based schedulers are adopted in real deployments. The class-based systems, however, cannot provide bounded delays in networks with cycle, since the maximum burst grows infinitely along the cycled path. Attaching a regulator in front of a scheduler to limit the maximum burst is considered as a viable solution. International standards, such as IEEE 802.1 time sensitive network (TSN) and IETF deterministic network (DetNet) are adopting this approach as a standard. The regulator in TSN and DetNet, however, requires flow state information, therefore contradicts to the simple class-based schedulers. This paper suggests non-work conserving fair schedulers, called 'regulating schedulers' (RSC), which function as a regulator and a scheduler at the same time. A deficit round-robin (DRR) based RSC, called nw-DRR, is devised and proved to be both a fair scheduler and a regulator. Despite the lower complexity, the input port-based nw-DRR is shown to perform better than the current TSN approach, and to bind the end-to-end delay within a few milliseconds in realistic network scenarios. [ABSTRACT FROM AUTHOR]

Micro/nano fluidic energy conversion devices have been reported for decades, but are still limited by low efficiency and output power in practical applications. Recently, several reports have demonstrated that the efficiency can be dramatically increased with microjet systems. However, previous devices with a single jet have low output power which is hard for utilization. Here, for the first time, we present a multi-pores microjet array generator and show that this device can achieve high output power with a simple design. The output performance is experimentally investigated by using a stainless steel micropores-array membrane with pore radius of 8 μm and thickness of 60 μm. The experiment results show that this generator can output a maximum voltage of ~85 kV and current of 1268.08 nA. The output power is 38 mW and the corresponding power density is up to 1.39  ×  106 W m−2. This work may enable microjet systems being used in low power devices and open up a new prospect for environmental energy harvesting. [ABSTRACT FROM AUTHOR]