Browsing by Department "NOVA University Lisbon"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    The Impact of Demand Response Programs on Reducing the Emissions and Cost of A Neighborhood Home Microgrid
    (MDPI AG, 2019) Fouladfar, Mohammad Hossein; Loni, Abdolah; Bagheri Tookanlou, Mahsa; Marzband, Mousa; Godina, Radu; Saad Al-Sumaiti, Ameena; Pouresmaeil, Edris; Islamic Azad University; Northumbria University; NOVA University Lisbon; Khalifa University; Renewable Energies for Power Systems; Department of Electrical Engineering and Automation
    The desire to increase energy efficiency and reliability of power grids, along with the need for reducing carbon emissions has led to increasing the utilization of Home Micro-grids (H-MGs). In this context, the issue of economic emission dispatch is worthy of consideration, with a view to controlling generation costs and reducing environmental pollution. This paper presents a multi-objective energy management system, with a structure based on demand response (DR) and dynamic pricing (DP). The proposed energy management system (EMS), in addition to decreasing the market clearing price (MCP) and increasing producer profits, has focused on reducing the level of generation units emissions, as well as enhancing utilization of renewable energy units through the DR programs. As a consequence of the nonlinear and discrete nature of the H-MGs, metaheuristic algorithms are applied to find the best possible solution. Moreover, due to the presence of generation units, the Taguchi orthogonal array testing (TOAT) method has been utilized to investigate the uncertainty regarding generation units. In the problem being considered, each H-MG interacts with each other and can negotiate based on their own strategies (reduction of cost or pollution). The obtained results indicate the efficiency of the proposed algorithm, a decrease in emissions and an increase in the profit achieved by each H-MG, by 37% and 10%, respectively.
  • Thumbnail Image
    Item
    Power quality improvement with a pulse width modulation control method in modular multilevel converters under varying nonlinear loads
    (Springer International Publishing AG, 2020-05-01) Mehrasa, Majid; Godina, Radu; Pouresmaeil, Edris; Rodrigues, Eduardo M.G.; Catalão, João P.S.; University of Trieste; NOVA University Lisbon; Renewable Energies for Power Systems; University of Aveiro; University of Porto; Department of Electrical Engineering and Automation
    In order to reach better results for pulse width modulation (PWM)-based methods, the reference waveforms known as control laws have to be achieved with good accuracy. In this paper, three control laws are created by considering the harmonic components of modular multilevel converter (MMC) state variables to suppress the circulating currents under nonlinear load variation. The first control law consists of only the harmonic components of the MMC's output currents and voltages. Then, the second-order harmonic of circulating currents is also involved with both upper and lower arm currents in order to attain the second control law. Since circulating current suppression is the main aim of this work, the third control law is formed by measuring all harmonic components of circulating currents which impact on the arm currents as well. By making a comparison between the switching signals generated by the three proposed control laws, it is verified that the second-order harmonic of circulating currents can increase theswitching losses. In addition, the existence of all circulating current harmonics causes distributed switching patterns, which is not suitable for the switches' lifetime. Each upper and lower arm has changeable capacitors, named "equivalent submodule (SM) capacitors" in this paper. To further assess these capacitors, eliminating the harmonic components of circulating currents provides fluctuations with smaller magnitudes, as well as a smaller average value for the equivalent capacitors. Moreover, the second-order harmonic has a dominant role that leads to values higher than 3 F for equivalent capacitors. In comparison with the first and second control laws, the use of the third control-law-based method will result in very small circulating currents, since it is trying to control and eliminate all harmonic components of the circulating currents. This result leads to very small magnitudes for both the upper and lower arm currents, noticeably decreasing the total MMC losses. All simulation results are verified using MATLAB software in the SIMULINK environment.