فهرست مطالب

Journal of Energy Management and Technology
Volume:3 Issue: 2, Spring 2019

  • تاریخ انتشار: 1398/03/11
  • تعداد عناوین: 7
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  • Babak Pouresmaeil, Sajad Najafi Ravadanegh *, Shahram Hosseinzadeh Pages 1-8
    In recent years some researchers have focused on dividing of large distribution grids to autonomous Microgrids (MGs). The benefit of MGs consists of their ability to increase the reliability of distribution networks and reduce the power losses. The distribution resource within the MGs can balance the gap between limited generation capacity and actively growing demands. In this paper, we proposed the new dynamic boundaries for MGs to gain the flexibility in the grid. The proposed method is based on finding the optimal state of switches and sizing & siting of distributed energy resource (DES) in an MG-based distribution network. A bi-level optimization problem is used to solving the proposed method. In the upper level of the optimization, the sizing & siting of DER is implemented and the system, is updated to optimal switching in lower level. The stochastic model of wind, solar and load demand is represented. The 94 bus distribution network is modified to the MG-based distribution network for testing and validating the proposed model. The Particle swarm optimization (PSO)is applied to minimize the objective function of upper level and Genetic algorithm (GA) is used for minimization of lower level[1]. According to the results the optimal planning of the autonomous MGs can improve distribution network operation performance.
    Keywords: Autonomous MGs, Switching, Stochastic model, Reconfiguration, Uncertainty
  • Adekola Oke *, Chukwuemeka Diji Pages 9-13
    Logging encompasses all activities involved in the processing of fully developed tree for production of finished and intermediate planks of varying sizes. Energy is a major input for logging. In this study energy audit and analysis was used to determine the specific energy and cost of production. Primary data for the study included site visits and use of questionnaire to collect data on the wood species, energy use pattern and types of equipment used for logging. Measuring instruments such as wattmeter, stop watch and measuring tape were used to measure the current, voltage and power factor; time of operation and size of timber log used in sawmilling in the selected study areaThe study covered 24 sawmills spread across 5 states in the south-western part of Nigeria. The study showed that there are seven wood species in the study area. The specific energy (kWh/m3) and average processing costs per unit volume ($/m3) of the seven species measured in the study area are respectively as follows - Afara (Terminalia superba): 1.65 and 0.094; Iroko (Milicia excelsa): 4.48 and 0.260; Mahogany (Khaya ivorensis): 1.47 and 0.084; Opepe (Naulea diderrichii): 1.77 and 0.100; Omo (Cordia millenii): 0.75 and 0.043; Obeche (Triplochyton scleroxylon): 0.58 and 0.033; Igba (Parkia biglobosa): 1.01 and 0.058.The study showed that the Iroko was the most common wood species processed in the study area and has the highest specific energy for processing. The Iroko was also the most expensive wood specie for log processing in the study area.
    Keywords: Log processing, energy audit, energy analysis, specific energy, specific costs
  • Alireza Akbari Dibavar, Sayyad Nojavan *, Kazem Zare Pages 14-25

    Demand response program (DRP) and energy storage systems (ESSs) are two main tools for load management in smart grids. They can make distribution networks more reliable without costly upgrades for substation constructing or lines reinforcement. This work proposes an optimization framework of optimal sitting and sizing of ESSs in a smart distribution network in the presence of DRP and considering renewable energy sources (RESs) effects and network constraints. The proposed objective function includes two terms: 1) minimization of total investment costs of ESSs; 2) minimization of active losses cost and the power purchased from upstream grid and diesel generators. DRP can reduce operation costs by shifting an amount of loads from hours with high demand to hours with lower demand and so can reduce network losses and help in peak load shaving process. In order to solve the proposed optimization model, a mixed-integer non-linear programming (MINLP) model is constructed and solved using DICOPT solver by GAMS optimization software. A modified 33-bus distribution network is considered and the results of three different cases are compared. Finally it can be noted that total cost of network in case 2, with optimal ESS allocation is reduced by 4.9% with compare to the base case, while this reduction is about 20% in case 3 with considering DRPs beside ESS allocation.

    Keywords: Optimal allocation, Energy storage systems, Demand response program, Load management, Smart distribution network
  • MohammadAmin Hojjati Kermani *, Masoud Aliakbar Golkar, Sadaan Zokaei Pages 26-33

    In order to enhance the reliability of the power transmission grid, planning and employing regional protection along with traditional local protection is necessary. Both regional and wide area protection is contingent upon communication and data networking infrastructure and hence prone to cyber-attacks.  Moreover, since this kind of protection maintains network integrity while taking into account the specified combinatorial parameters; its output is not necessarily consistent with the output of local protection mechanisms. In other words, applying regional protection alters the arrangement of the whole network for maintaining the interests of all consumers. On the contrary, the local manager of transmission or distribution network may find this in conflict with his/her interests and may even take actions against it via cyber-attacks.The primary step to analyze these types of cyber-attacks is the ability to define the attacks in an adjustable way in a parametric model so that one can explicitly test different forms of attacks and subsequently offer methods to deal with them.In the present study, a multi-stage attack has been extracted and modeled with a timed Petri net, and then the results are compared with those of similar articles.

    Keywords: Cyber Attack, Special Protection Scheme, Timed Petrinet
  • Mohammad Jafari *, Behzad Ahmadi Pages 34-43
    Increasing uncertainty parameters in power systems have caused the system to require a controller in order to retain the stability at the time presence of renewable power plants and electric vehicles. In this research, sliding mode and feedback linearization controllers have been proposed to control parking lots in the field of reactive power and access targets, those have been followed up, including improving the voltage profile, the performance of synchronous generators and wind power plant in the transient state by the application of this control Method. The proposed control method is simulated on the IEEE-9 Bus grid and the extent of achieving the desired targets is examined in the efficiency of parking in the field of reactive power. The codes have been expanding by using MATLAB open source code software. Hence, the system developed by modeling. The simulation results of this method indicate proper tracking of the control objectives in the normal grid conditions and the parking resistance of the transient States. It can be concluded that the presence of all-Electric Vehicles (parking lots) in the grid causes a reduction of 50% in the rotor speed fluctuations of synchronous generators and reduces voltage fluctuations by up to 10 times by the qualitative and quantitative aspects, which indicates a 7.4% improvement in voltage profile. Therefore, by maintaining the grid voltage in the appropriate range and limiting the current flow in rotor windings, has been avoided the possibility of damage to the rotor winding during a probable short circuit in the grid.
    Keywords: Nonlinear controller, Smart parking, Doubly fed induction generator, Sliding Mode Controller, feedback linearization controller
  • Paul Kwakwa * Pages 44-57
    Although energy is important, the increasing consumption has sustainable implications. Tunisia’s energy consumption in recent times has exceeded supply raising concerns for future energy security. However, the country’s energy intensity has been reducing for close to two decades. The study was embarked upon to investigate the drivers of Tunisia’s total energy consumption and energy intensity. Estimation results from the fully modified OLS using annual time series data from 1971-2014 indicate that income, forest extraction, oil extraction and urbanization have positive effects on total energy consumption while mining activities and political regime negatively affect total energy consumption. However, income, political regime, urbanization and mining activities were all found to reduce energy intensity. Further asymmetric analysis showed that the parameters have been influenced by a structural effect. The policy implications of the findings include the need for the government of Tunisia to encourage investment activities on research and development to deepen the formulation an improved energy savings technology to meet the rising demand for energy in the urban areas.
    Keywords: Tunisia, natural resource, energy consumption, energy intensity, asymmetric effects
  • Jaber Fallah Ardashir *, Amin Mohammadpour Shotorbani, Hossein Khoun Jahan, Mehran Sabahi Pages 58-64

    This paper presents a single-phase transformer-less flying capacitor inverter (FCI) for applications in grid-tied PV systems. In this structure, the neutral point of the grid is connected directly to the negative terminal of PV, so the common mode (CM) leakage current eliminate without using any control strategy. The main merits of this inverter are flexible grounding configuration and high safety. A fractional-order proportional resonant (FPR) controller is employed for the proposed FCI to improve its performance during transient and steady state operation. The low output current ripple of the proposed FPR controller against parameter uncertainties is compared with conventional proportional resonant (PR) controller. The capability of controllers is investigated for parametric changes. The grid connected inverter can achieve the maximum power point tracking (MPPT) of the solar panels and inject a sinusoidal current into the grid with FPR controller. Finally, performance of the proposed controller scheme as well as the grid-tied FCI topology are verified through simulation results.

    Keywords: Grid Tied Inverter, Fractional Proportional Resonant, Photovoltaic system, flying capacitor inverter, Leakage Current