فهرست مطالب

  • Volume:4 Issue: 4, 2020
  • تاریخ انتشار: 1399/04/18
  • تعداد عناوین: 6
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  • Seyed Hossein Tabatabaei, HamidReza Najafi *, Hussain Eliasi, Alireza Jalilian Pages 1-11

    In this paper, a new structure is presented for an interlinking converter (IC) to improve voltage in hybrid AC-DC microgrids. This structure consists of a series IC (SIC) and a parallel IC (PIC) parts. The PIC is responsible for ex-changing the power between sub-grids and decreasing voltage unbalance indices. Based on the free capacity of PIC, voltage unbalance compensation reference is calculated on the AC sub-grid side. In the series part of IC, any kind of voltage disturbance is compensated for the sensitive load. In order to increase the speed of dynamic response and to decrease the loss in SIC, the resistor of output filter is removed and then, fluctuations are damped in an active way in the control system. This is carried out by feeding back the current of the capacitor of the output filter and applying it to the control system and using the current mode control in the inner loop which improves the stability. Proportional-resonant and proportional-differential controllers are used in the control part of SIC. Therefore, proper tracking of the reference signal is guaranteed. Results obtained from the simulation of the case study system in MATLAB software verify the capabilities of the proposed approach.

    Keywords: Hybrid AC-DC microgrid, interlinking converter, unbalance compensation, voltage sag, active damping
  • Amir Gallaj, Mojtaba Beiraghi *, Jaber Fallah Ardashir, Reza Ghanizadeh Pages 12-20
    This paper presents a new switched-capacitor multilevel converter (SCMC) which is able to produce any levels at output voltage waveform. This topology can increase the value of input dc voltage sources using the switched-capacitor units. In the proposed SCMC topology, as the numbers of switched-capacitor units increase, the voltage gain and the number of generated levels will be increased. In this paper, the main merit of proposed SCMC topology is inherent voltage balancing of capacitors which do not require complicated switching strategy. The proposed SCMC structure is compared with traditional multilevel converters. The comparison results verify that the presented SCMC structure needs lower dc voltages sources, switches, and capacitors. The mathematical analysis of standing voltage on switches and different kinds of power losses in the presented SCMC structure are provided. In order to verify the performance of presented SCMC topology, the experimental results for a typical 13-level converter is provided.
    Keywords: Multilevel converter, Switched-Capacitor, Standing Voltage, Power Losses, Voltage balancing
  • Mohsen Shahabi, HassanAli Ozgoli *, Abbas Akbarnia Pages 21-27

    This paper proposed the effect of using a heat recovery system in the gas turbines of Semnan to shahroud oil pumping station in energy conservation point of view. Heating the transferred fluids is one of the common approaches to reduce fluids viscosity and energy consumption, respectively. Due to the low efficiency of station turbines compared to modern turbines, it is expected that the use of heat recovery has a positive effect on improving station performance. By analyzing the combustion products of the gas turbine at the station, the heat extracted from the exhaust gas flow has been calculated which is consumed in the recovery boiler. The pipeline application process including recovery boiler and main equipment of Semnan and Shahroud pumping stations have been modeled. By applying the model, it found that the amount of energy savings by gas-oil heating using a heat exchanger equals to 395311 m3 natural gas in annually. Therefore, optimal points of using combustion heat in the gas turbine output were obtained. In addition, the reduction of power consumption in the presented station has been calculated. Economic calculations were carried out for different countries including Iran, Scandinavian countries, China and the Europian Union average, based on their energy prices and bank interest rates.

    Keywords: Oil Pumping Station, Pipeline, Energy Saving, Gas turbine, Heat Recovery
  • Easa Aliabbasi, Akbar Allahverdizadeh *, Behnam Dadashzadeh, Reza Jahangiri Pages 28-35
    This paper presents a non-contact system to measure electrical current crossing a wire. To do so, design and simulation of a piezoelectric cantilever beam with a tip mass is presented using mathematical modeling. The sandwich cantilever beam is composed of two piezoelectric layers and a mid-layer made up of steel. For mathematical modeling, the governing differential equation of the beam is extracted and solved by Galerkin method. Then the output voltage is calculated for different values of external forces. The force applied to the tip mass from the magnetic field of wire is used as external excitation force of the beam. According to the response of the output voltage, the current crossing the wire is calculated. Validation of the model is demonstrated compared to other references. In results section, frequency response behavior and influence of the geometric parameters on output voltage are analyzed. Appropriate values of these parameters should be used in design process of this non-contact sensor to have an observable applied force from the current carrying wire.
    Keywords: Bimorph cantilever beam, Piezoelectric, Electrical current measurement, Forced excitation, Non-contact sensor
  • Nima Norouzi, Maryam Fani * Pages 36-48
    Despite significant medical advances in the past centuries, infectious diseases such as the flu or malaria are still a severe threat to society. While some do not have specific geographic areas, others can spread and become epidemic or pandemics. While the first and foremost aspect of an epidemic is the loss of human life and will always remain, the outbreak can also have significant consequences for national or regional economies. The evidence reported in various studies suggests that the epidemic is affecting the country's economy through various aspects, including health, transportation, agriculture, and tourism. At the same time, markets and economic trade with other countries may also be affected, while the convergence of modern economies means that an epidemic can also encompass international supply chains. All these facts state that Coronavirus, as the first major pandemic in the last century, is one of the most critical issues to be studied. These facts, as well as the fast urbanization, increased international travel, and changing conditions are causing a global outbreak, not just a local phenomenon, imply that measures are needed for all countries to tackle this threat. In this paper, the impacts of the Coronavirus on the economic status and Energy demand (mainly oil and electricity) are being studied to determine the vulnerability of the economic and energy security in the time of severing epidemics or pandemics
    Keywords: Coronavirus, Petroleum, Demand Analysis, Economic impacts, COVID-19, Pandemic
  • Nohman Jbari, Adil Elbaouchi, Redouane Benhima, Iman Bennis, Rachid Boulif, Youssef Zeroual, Hicham EL Arroussi * Pages 49-56
    In recent years, biodiesel from microalgae has received large interest around the world, as sustainable energy for biofuel production. Mineral fertilizers can be a promising source for the development of low cost culture media. We investigate the influence of fertilizer-based media: MAP, TSP, Phosphoric acid and Ammonitrate on cell viability, nutrients uptake, biomass, lipids production and lipids profile of 3 microalgae strains. The best biomass production was 2.105 g L-1, 1.95g.L-1 and 1.75g.L-1 for D. tertiolecta, Isochrysis sp.and Tetraselmis sp cultured in TSP, MAP and H3PO4(54%)based-media respectively, compared to control medium (1.85, 1.76 and 1.71 g L-1 respectively). Lipid content of all strains in fertilizer-based media was similar to control. The lipid profile showed that FAMEs of all microalgae underwent a significant reduction in PUFAs for fertilizers based-media, which improves the quality of biodiesel. Mineral fertilizers are a promising source that can be a low-cost microalgae production base at the industrial level.
    Keywords: Microalgae, Fertilizers, culture, medium, Biodiesel